WO2023076617A1

WO2023076617A1 - Systems and methods for collection of fluid from gas streams

Info

Publication number: WO2023076617A1
Application number: PCT/US2022/048252
Authority: WO
Inventors: Maher DAMAK; Karim Khalil; Andras Kiss; Scott Rowe; Kripa Varanasi
Original assignee: Infinite Cooling Inc.
Priority date: 2021-10-29
Filing date: 2022-10-28
Publication date: 2023-05-04

Abstract

The present disclosure provides systems and methods for passively collecting fluid from a gas stream using one or more porous collectors. Porous collectors may be or include mesh(es) or other porous structures, such as perforated or stamped sheets (e.g., of metal or plastic). By providing collector(s) in a path of a gas stream that are appropriately constructed and positioned, as further discussed subsequently, appreciable fluid collection can occur by simple inertial impact of the fluid on the collector(s). Specifically, systems herein can exploit swirl component(s) of velocity of a gas stream (that are not axial with a primary direction of flow) to cause fluid to be collected (e.g., impact and remain) on collectors. A swirl component of velocity may be, for example, a tangential, radial, or rotational component or a combination thereof.

Description

SYSTEMS AND METHODS FOR COLLECTION OF FLUID FROM GAS STREAMS

PRIORITY APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63/273,832, filed on October 29, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] This disclosure relates generally to structures that can be used for passively collecting fluid from a gas stream.

BACKGROUND

[0003] Various systems have been implemented to capture fluid from gas streams, for example for recycling and/or plume or fog abatement purposes. Fog collection has been attempted with large woven meshes placed perpendicularly to fog-laden wind. The perpendicular arrangement results in a high pressure drop in the flow direction and low capture efficiencies. Other technologies include systems using electric fields to capture water from fog, cooling towers and other gas streams. In some embodiments, they rely on an electrostatic force to attract droplets to a collector. Examples of active collection schemes that use voltages applied to emitter electrodes to cause fluid to be collected are described in U.S. Patent Publication No. 2021/0031212. While such systems can be highly efficient in their collection, they are electrified and therefore have additional construction, installation, maintenance, and operating costs. Drift eliminators are another technology that is used in cooling towers to capture large droplets that are entrained out of the cooling tower. They typically use tortuous channels to make droplets change direction, impact the walls and fall back in the tower. Similar to fog collection meshes, drift eliminators impose a pressure drop in the axial direction of the flow. Therefore, while collection technologies exist, there remains a need for simple, low-cost collection systems and methods, especially those that have minimal impact on the flow of the gas stream from which they collect fluid. SUMMARY

[0004] Most exhaust systems are sensitive to pressure drop. A certain flow rate is needed and systems are typically designed to produce that flow rate without additional blockage of the flow. Traditionally, passive systems such as drift eliminators or fog collection meshes have relied on adding collectors to the flow path and having droplets impact the obstructions as they travel through them. These traditional approaches are associated with high pressure drops in the axial direction and typically cannot be added to an exhaust without reducing the flow rate and/or increasing fan energy consumption.

[0005] The present disclosure provides, inter alia, systems and methods for passively collecting fluid from a gas stream using one or more porous collectors. Porous collectors may be or include mesh(es) or other porous structures, such as perforated or stamped sheets (e.g., of metal or plastic). By providing collector(s) in a path of a gas stream that are appropriately constructed and positioned, as further discussed subsequently, appreciable fluid collection can occur by simple inertial impact of the fluid on the collector(s). Specifically, systems herein can exploit swirl component(s) of velocity of a gas stream (that are not axial with a primary direction of flow) to cause fluid to be collected (e.g., impact and remain) on collectors. A swirl component of velocity may be, for example, a tangential, radial, or rotational component or a combination thereof. Collector(s) may be aligned such that a swirl component of velocity causes fluid dispersed in a gas stream to collect more so than an axial component of velocity along a primary direction of flow for the gas stream. For example, fluid in a gas stream may impact collector(s) that are parallel to a primary direction of flow only negligibly if there is no swirl component to the gas stream’s velocity but collect significantly on the collector(s) when there is a swirl component. Fluid may be dispersed in a gas stream as liquid, vapor, droplets, drift or mist. The fluid may be or comprise water. Once sufficient fluid has collected on collector(s), for example due, at least in part, to surface tension of the fluid on the collector(s), it may be shed due, at least in part, to gravity. The fluid may be collected into one or more gutters upon shedding. For example, gutter(s) may be disposed at a bottom of collector(s) such that fluid naturally falls from collector(s) into the gutter(s) once gravity overcomes surface tension. By using passive collection, the need for electrification is eliminated.

[0006] Using systems and methods disclosed herein, fluid collection can occur while causing an asymmetric effect on pressure drop in a primary direction of flow (relatively large effect on flow rate) and local pressure drop in other direction(s) (e.g., perpendicular to the flow (relatively minimal effect on flow rate). By reducing or minimizing the effect on pressure drop in a primary direction of flow of a gas stream, other processes, such as cooling, that are performed using the gas stream can be relatively unaffected. For example, cooling tower efficiency can remain high while harvesting water (or other fluid) from gas escaping the cooling tower to ambient. Thus, when a gas stream has a swirl component to velocity, effective anisotropic porosity in a collection of one or more collectors can yield a low pressure drop in a primary direction and a moderate pressure drop in non-primary direction(s) (e.g., horizontal direction(s)), where the moderate pressure drop in non-primary direction(s) has relatively minimal externalities. Thus, in some embodiments, water collection proceeds as swirl of the flow of a gas stream is reduced, while axial flow (along a primary direction of flow) is less affected. Therefore, in some embodiments, underlying fan and/or exhaust components to a system can still operate substantially as intended. In some embodiments, pressure drop in non- primary direction(s) should be tuned (e.g., using parameters discussed in detail subsequently) so that reduction in a swirl component of velocity is slow enough for fluid (e.g., droplets) to have time to be collected on (e.g., impact and be retained on) collector(s).

[0007] One or more of several advantages can be realized in various embodiments of collection systems and methods described herein. In some embodiments, an appreciable amount of water is collected from a gas stream, while maintaining a relatively low pressure drop in a primary direction of flow. Therefore, in some embodiments, the effect on a fan on the system that is rejecting air can be minimal. Some embodiments, in addition to fluid collection, may result in improved fan efficiencies. Depending on specific aerodynamic performance, flow straightening may result in the conversion of swirl kinetic energy to fluid potential energy (static pressure). In some such embodiments, the system results in a static pressure rise rather than static pressure drop in a primary direction of fluid flow (e.g., out of a cooling tower), decreasing a required static pressure rise of a fan, and thus the fan power consumption, for a given flow rate. In some embodiments, a significant amount of swirl reduction can be achieved with a disclosed system and/or method. While generally fluid collection from gas streams is of primary concern, flow straightening is a potentially advantageous by-product, as it can make gas flow more efficient in some applications. For cooling towers and other similar applications, collected water may be much purer than circulating water in the system. Any contamination in collected water comes from the presence of drift that is also collected with the distilled water in the plume. Field testing has shown that water collected by collector(s) from air escaping from cooling towers can have more than lOx lower contaminants and dissolved contents than cooling tower water in circulation. In some embodiments, collection systems disclosed herein can be used as a new source of fresh water, as collected water does not have to be used for cooling after collection but can be used for demineralized water production, drinking water production and other municipal uses.

[0008] Collections systems disclosed herein may be used for a variety of purposes, for example depending on the application they are used in, such as at a cooling tower or in a duct of an HVAC system. Systems and methods disclosed herein may be used for water capture. For example, in the particular cases of cooling towers and other vapor emitters, they enable passive water harvesting and, if desired, re-use. Systems and methods disclosed herein may also be used for mist filtration. For example, in cases of flows carrying fluid (e.g., liquid droplets) that a user does not want to leave a system (e.g., escape to ambient and/or comingle with another gas stream), systems and methods disclosed herein can be used to reduce either fully or partially the amount of fluid in the gas stream. For example, toxic and/or irritating fluids (e.g., vapors and/or liquid) can be removed with disclosed systems and methods. Additionally or alternatively, systems and methods disclosed herein may be used for plume abatement. Industrial plumes can be emitted from various systems, such as cooling towers. In some embodiments, systems disclosed herein may be constructed and disposed (e.g., positioned and oriented) to passively remove fluid from such plumes to fully or partially eliminate them, which may enhance visibility, improve safety and/or limit or prevent diffusion of toxic species.

[0009] In some aspects, a method for collecting fluid from a gas stream includes flowing a gas stream, wherein velocity of the gas stream comprises an axial component along a primary direction of flow of the gas stream and a separate swirl (e.g., tangential, radial, and/or rotational) component. The method may further include collecting fluid from the gas stream on one or more porous (e.g., mesh) collectors disposed along the primary direction of flow, wherein the one or more collectors are aligned such that the fluid collects on (e.g., impact and remain on) the one or more collectors at least [e.g., only or substantially (e.g., at least 90% due to)] due to the swirl component of the velocity. [0010] In some embodiments, the collecting occurs passively at least in part due to the swirl component.

[0011] In some embodiments, the one or more collectors are spaced apart in a direction non-parallel to the axial component of the velocity. In some embodiments, the one or more collectors are substantially parallel (e.g., within 5 degrees) to the axial component of the velocity.

[0012] In some embodiments, the gas stream is flowed towards (e.g., through) a gas outlet to ambient (e.g., through a duct) and the collecting occurs as the gas stream flows toward the ambient.

[0013] In some embodiments, a pressure drop across the one or more collectors is no more than 50% (e.g., no more than 25% or no more than 10%) of an initial pressure of the gas stream immediately prior to the one or more collectors.

[0014] In some embodiments, collecting the fluid comprises collecting at least 10% (e.g., at least 20%, at least 40%, or at least 60%) of initial fluid in the gas stream. In some embodiments, flowing the gas stream over the one or more collectors causes the axial component of the velocity to be reduced less (e.g., at least 2x less, at least 3x less, at least 5x less, at least lOx less) than the swirl component of the velocity is reduced relative to initial values of the axial component and the swirl component, respectively. In some embodiments, less than 25% (e.g., less than 20%, less than 15%, less than 10%, less than 5%, less than 2%, or less than 1%) of the fluid collected on the one or more collectors is re-entrained into the gas stream as the gas stream flows over the one or more collectors.

[0015] In some embodiments, the swirl component of the velocity is at least partially actively imparted to the gas stream. In some embodiments, the method comprises rotating a fan to actively impart at least a portion of the swirl component of the velocity to the gas stream. In some embodiments, the swirl component of the velocity is at least partially passively imparted to the gas stream. In some embodiments, the method comprises flowing the gas stream over one or more turbulence inducing structures [e.g., angled corners of the one or more collectors (e.g., where ones of the one or more collectors are joined together (e.g., at an angle))] (e.g., one or more baffles and/or wind breaks) to passively impart at least a portion of the swirl component of the velocity to the gas stream. [0016] In some embodiments, the gas outlet is an outlet of a cooling tower and a cooling efficiency of the cooling tower is reduced during the method by no more than 20% on average over a period of time relative to a baseline cooling efficiency of the cooling tower without the one or more collectors under otherwise equivalent conditions.

[0017] In some embodiments, the gas outlet is an outlet of a cooling tower and a normalized cooling efficiency of the cooling tower is reduced during the method by no more than 20% on average over a period of time, wherein the normalized cooling efficiency of the cooling tower is a value normalized as a function of time during operation since installation of the one or more collectors.

[0018] In some embodiments, the collecting occurs at a position along the direction of flow prior to the gas stream exiting a gas outlet (e.g., and prior to the fan, e.g. within 20 m, within 10 m, or within 5 m) (e.g., and after the fan, e.g. within 20 m, within 10 m, or within 5 m). In some embodiments, the collecting occurs after the gas stream exits a gas outlet (e.g., within 20 m, within 10 m, or within 5 m of the gas outlet).

[0019] In some embodiments, the method comprises shedding, at least in part due to gravity, at least a portion of the fluid collected on the one or more collectors into one or more gutters (e.g., channels) (e.g., disposed at a bottom surface of the one or more collectors) (e.g., and collecting the at least a portion of the fluid from the one or more gutters). In some embodiments, the at least a portion of the fluid collected into the one or more gutters has at least 5x (e.g., at least lOx) lower contaminants and dissolved contents than circulating fluid from which the fluid was entrained into the gas stream.

[0020] In some embodiments, flowing the gas stream along the one or more collectors straightens flow of the gas stream (e.g., relatively increases the axial component of the velocity). [0021] In some embodiments, the method comprises providing the one or more collectors, wherein providing the one or more collectors comprises determining one or more of a number of collectors in the one or more collectors, a dimension (e.g., height and/or width) of each of the one or more collectors, a spacing between ones of the one or more collectors, a wire diameter, and open area in each of the one or more collectors (e.g., determined by pore size and/or wire spacing and wire diameter) based on one or more of a target fluid capture percentage, a target cooling efficiency for a cooling tower at which the one or more collectors are installed, and a target pressure drop across the one or more collectors. [0022] In some embodiments, each of the one or more collectors comprises a mesh of one or more wires defining openings in the mesh and collecting the fluid comprises collecting droplets of the fluid such that each of the droplets is in contact with at least one of the one or more wires of the mesh [e.g., is in contact with multiple wires (e.g., each of the droplets individually at least partially spans one of the openings on the mesh of one of the collectors)]. [0023] In some embodiments, the method comprises mixing ambient air into the gas stream after the gas stream exits a gas outlet prior to the collecting the fluid from the gas stream. In some embodiments, collecting the fluid from the gas stream comprises collecting condensed fluid from a region where the fluid condenses in the gas stream. In some embodiments, collecting the fluid from the gas stream comprises collecting water from a plume in the gas stream.

[0024] In some embodiments, the fluid is liquid, vapor, droplets, drift or mist (e.g., of water) dispersed in the gas stream.

[0025] In some embodiments, the fluid collects on the one or more collectors without using a voltage and/or electric field. In some embodiments, the one or more collectors are nonelectrified.

[0026] In some embodiments, the one or more collectors is a plurality of collectors disposed about a central axis and aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream). In some embodiments, the plurality of collectors is disposed axisymmetrically about the central axis.

[0027] In some embodiments, the method includes charging the fluid in the gas stream upstream of the one or more collectors. In some embodiments, the method includes applying a non-charging electric field (e.g., to the charged fluid) to direct the fluid towards the collectors. In some embodiments, the electric field is applied using electrodes disposed near (e.g., within 0.5 m of) the one or more collectors [e.g., wherein applying the electric field comprises applying a voltage (e.g., a high voltage) of a same polarity as the charged fluid to the electrodes] (e.g., wherein each of the electrodes is operable to generate an electric field that directs the fluid towards a respective one of the collectors). In some embodiments, the electrodes are porous and/or spaced apart to allow the gas stream to flow through the electrodes (e.g., without substantially interfering with the flow of the gas stream).

[0028] In some embodiments, the collecting occurs passively. [0029] In some aspects, the disclosure is directed to a system for collecting fluid from a gas stream. The system may comprise one or more porous collectors disposed along a primary direction of gas flow for a gas stream comprising fluid dispersed therein (e.g., oriented parallel to the primary direction). In some embodiments, the one or more collectors are positioned and oriented such that a swirl component of velocity of the gas stream results in the fluid being collected from the gas stream on the one or more collectors. The system may include one or more porous (e.g., mesh) collectors disposed along a primary direction of flow for a gas stream comprising fluid dispersed therein. In some embodiments, the one or more collectors each have a Stokes number (St) of at least 0.05 (e.g., at least 0.1 or at least 0.2), wherein, St = ^{2Rd PlU} with llgRc

Rd is an effective radius (e.g., droplet radius) of the fluid in the gas stream (e.g., an average droplet radius), Rc is a characteristic feature size (e.g., an average wire radius in a mesh collector or average pore separation in a non-mesh porous collector), pi is a density of the fluid in the gas stream, U is speed of the flow of the gas stream, and Tj_g is dynamic viscosity of the gas stream. [0030] In some embodiments, the one or more collectors is a plurality of collectors that are spaced apart in a direction non-parallel to the primary direction of gas flow. In some embodiments, the one or more collectors are aligned substantially parallel (e.g., within 5 degrees) to the primary direction of gas flow. In some embodiments, each of the one or more collectors is tilted with respect to the primary direction of gas flow (e.g., and is/are mutually parallel or and is/are mutually non-parallel).

[0031] In some embodiments, each of the one or more collectors comprises a mesh (e.g., a ID or 2D mesh) (e.g., a rectangular or square mesh) comprising one or more wires. In some embodiments, the one or more wires comprises (e.g., each comprise) a conductive material (e.g., a metal) and/or a non-conductive material (e.g., a polymer). In some embodiments, the one or more wires are coated with a coating that changes (e.g., increases or decreases) the surface tension of the one or more wires (e.g., to promote coalescing and/or shedding of collected fluid). [0032] In some embodiments, the one or more collectors are disposed in a duct. In some embodiments, the system includes a gas outlet [e.g., wherein the gas stream escapes to ambient from the gas outlet and the one or more collectors are disposed near (e.g., within 30 m, within 20 m, with 10 m, or within 5 m of) the gas outlet] (e.g., wherein the gas outlet is an outlet of a cooling tower) [e.g., wherein the one or more collectors are aligned (e.g., parallel) with the primary direction of flow and span the gas outlet],

[0033] In some embodiments, the system includes one or more gutters (e.g., one or more channels) disposed to collect fluid shed from the one or more collectors due, at least in part, to gravity (e.g., wherein the one or more gutters are disposed along bottom edge(s) of the one or more collectors) (e.g., wherein two or more collectors share a common gutter).

[0034] In some embodiments, the system includes a fan to impart (e.g., introduce and/or increase) a (e.g., the) swirl component to velocity of the gas stream. In some embodiments, the one or more collectors are disposed in a shroud of the fan. In some embodiments, wherein the one or more collectors are disposed prior to the fan along the primary direction of flow of the gas stream (e.g., within 20 m, within 10 m, or within 5 m of the fan). In some embodiments, the gas outlet is an outlet from which gas stream escapes to ambient. In some embodiments, the one or more collectors are disposed after and over a gas outlet (e.g., of a cooling tower) (e.g., within 20 m, within 10 m, or within 5 m of the outlet). In some embodiments, the one or more collectors are disposed after and over the gas outlet such that ambient air can mix into the gas stream after the gas outlet and prior to collecting the fluid from the gas stream by the one or more collectors. In some embodiments, the one or more collectors are disposed after and over the gas outlet such that the one or more collectors are disposed to collect condensed fluid from the gas stream in a region where the fluid condenses.

[0035] In some embodiments, one or more of a number of collectors in the one or more collectors, a dimension (e.g., height and/or width) of each of the one or more collectors, a spacing between ones of the one or more collectors, a wire diameter, and open area in each of the one or more collectors (e.g., determined by pore size and/or wire spacing and wire diameter) is based on one or more of a target fluid capture percentage, a target cooling efficiency for a cooling tower at which the one or more collectors are installed, and a target pressure drop across the one or more collectors.

[0036] In some embodiments, the one or more collectors have a curved, circular, or polygonal cross-section taken in a plane perpendicular to the primary direction of flow. In some embodiments, the one or more collectors comprises a plurality of collectors that are concentrically arranged. In some embodiments, the one or more collectors are each planar. In some embodiments, the one or more collectors comprises a plurality of collectors and ones of the collectors are physically attached together. In some embodiments, each of the one or more collectors is a panel (e.g., a planar panel) [e.g., comprising a rigid frame (e.g., that holds a mesh (e.g., under tension))].

[0037] In some embodiments, the one or more collectors are each held under tension (e.g., each comprises a mesh held under tension) [e.g., by one or more tensioning cables (e.g., running through the mesh)].

[0038] In some embodiments, the system includes one or more turbulence inducing structures [e.g., angled comers of the one or more collectors (e.g., where ones of the one or more collectors are joined together (e.g., at an angle))] that can introduce turbulence to the gas stream [e.g., to impart (e.g., introduce or increase) a swirl component of velocity to the gas stream], [0039] In some embodiments, the system is non-electrified. In some embodiments, the one or more collectors are non-electrified. In some embodiments, the system is a passive collection system.

[0040] In some embodiments, the system is operable to collect at least 10% (e.g., at least 20%, at least 40%, or at least 60%) of initial fluid in the gas stream.

[0041] In some aspects, a system for collecting fluid from a gas stream includes porous collectors disposed about a central axis. In some embodiments, the collectors are disposed in alignment with one or more radial directions from the central axis. In some embodiments, ones of the collectors are disposed in alignment with different ones of the one or more radial directions. In some embodiments, ones of the collectors are disposed along a same one of the one or more radial directions and on opposing sides of the central axis. In some embodiments, the collectors are disposed axisymmetrically about the central axis.

[0042] In some embodiments, the collectors is an even number of collectors and the collectors are disposed in pairs about the central axis, each pair comprising one collector disposed on a first side of the central axis and another collector disposed on a second side of the central axis opposite the first side. In some embodiments, the collectors extend from the central axis to an outer perimeter and the outer perimeter is an ellipse (e.g., circle). In some embodiments, the collectors extend from the central axis to an outer perimeter and the outer perimeter is a polygon (e.g., rectangle).

[0043] In some embodiments, the collectors are passive collectors (e.g., cannot be electrified). In some embodiments, the collectors are grounded. [0044] In some embodiments, the system includes a pre-charging stage operable to charge the fluid in the gas stream (e.g., using corona discharge), wherein the pre-charging stage is disposed relative to the collectors to be in an upstream direction (e.g., in an upstream direction when the collectors are disposed in a duct or after and over a gas outlet) (e.g., disposed after a fan that applies a swirl component of velocity to the gas stream). In some embodiments, the precharging stage comprises one or more electrodes (e.g., low radius wires or needles) (e.g., operable to maintain a voltage of at least 1 kV and, optionally, no more than 500 kV [e.g., a voltage of at least 5 kV at least 10 kV, at least 15 kV, at least 25 kV, at least 50 kV, at least 100 kV) (e.g., and no more than 250kV, no more than 100 kV, or no more than 50 kV)]) (e.g., disposed in a plane substantially perpendicular to an axial component of velocity of the gas stream). In some embodiments, the pre-charging stage comprises a grounded surface (e.g., a mesh or plate) (e.g., disposed in a plane substantially perpendicular to an axial component of velocity of the gas stream) (e.g., disposed in a downstream direction from the one or more electrodes).

[0045] In some embodiments, the system includes a frame (e.g., a metal frame or non- conductive frame) (e.g., a one piece or multi-piece frame), wherein the collectors are attached to the frame. In some embodiments, the frame comprises a central support aligned with the central axis (e.g., a rod) and the collectors are attached to the central support. In some embodiments, the frame comprises an outer cage (e.g., a cylindrical or rectangular cage) and the collectors are (e.g., also) attached to the outer cage. In some embodiments, the outer cage is open (e.g., is a skeletal outer cage or is porous). In some embodiments, the collectors are electrically insulated from the frame.

[0046] In some embodiments, the system includes one or more electrodes disposed near (e.g., within 0.5 m of) each of the collectors (e.g., one electrode per collector, more than one electrode per collector, or at least some of the collectors having more than one associated electrode), wherein the gas stream can flow through (e.g., around) the one or more electrodes (e.g., due to a swirl component of velocity of the gas stream) [e.g., wherein the one or more electrodes are attached to a frame (e.g., under tension)]. In some embodiments, the one or more electrodes are disposed such that an electric field generated using the one or more electrodes directs fluid from the gas stream towards no other of the collectors than the collector near which the one or more electrodes are disposed. In some embodiments, the one or more electrodes comprises a wire (e.g., a tensioned wire) or a tube. In some embodiments, the one or more electrodes form a mesh (e.g., a wire mesh) (e.g., a ID or 2D mesh). In some embodiments, the system includes one or more electrically insulating members (e.g., each comprising one or more sheds), wherein the one or more electrodes are attached to a (e.g., the) frame by the one or more electrically insulating members. In some embodiments, each of the one or more electrodes is attached to the frame by a unique set of one or more of the one or more electrically insulating members. In some embodiments, the one or more electrodes are electrically insulated from the frame.

[0047] In some embodiments, the collectors are planar. In some embodiments, all of the collectors have a substantially identical size. In some embodiments, each of the collectors has a length along the central axis and a width extending along one of the one or more radial directions with which the collector is aligned and the length is larger than the width (e.g., at least 1.5x or at least 2x as large as the width). In some embodiments, each of the collectors is a panel (e.g., a planar panel). In some embodiments, each of the collectors comprises a mesh (e.g., a wire mesh). In some embodiments, each of the collectors comprises a rigid frame that holds the mesh under tension [e.g., by one or more tensioning cables (e.g., running through the mesh)].

[0048] In some embodiments, the collectors are disposed in a duct (e.g., and span the duct) such that the central axis is aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream). In some embodiments, the collectors are disposed after and over a gas outlet (e.g., of a cooling tower or of a duct) such that the central axis is aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream). In some embodiments, the collectors span the gas outlet.

[0049] In some embodiments, the collectors are aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream). In some embodiments, the collectors are disposed substantially perpendicular to a swirl component of velocity of the gas stream (e.g., an axial component of velocity of the gas stream). In some embodiments, the collectors are each disposed substantially parallel to a plane on which the central axis lies. In some embodiments, the collectors are positioned and oriented such that a swirl component of velocity of the gas stream results in the fluid being collected from the gas stream on the collectors. [0050] In some embodiments, the collectors each have a Stokes number St) of at least 0.05 (e.g., at least 0.1 or at least 0.2), wherein St = ²^^P^^U, with Rd is an effective radius (e.g., droplet radius) of the fluid in the gas stream (e.g., an average droplet radius), Rc is a characteristic feature size (e.g., an average wire radius in a mesh collector or average pore separation in a non-mesh porous collector), pi is a density of the fluid in the gas stream, U is speed of flow of the gas stream, and Tj_g is dynamic viscosity of the gas stream. In some embodiments, the system is operable to collect at least 10% (e.g., at least 20%, at least 40%, or at least 60%) of initial fluid in the gas stream.

[0051] In some embodiments, the fluid is liquid, vapor, droplets, drift or mist (e.g., of water) dispersed in the gas stream.

[0052] Any two or more of the features described in this specification, including in this summary section, may be combined to form implementations not specifically explicitly described in this specification.

[0053] At least part of the methods, systems, and techniques described in this specification may be controlled by executing, on one or more processing devices, instructions that are stored on one or more non-transitory machine-readable storage media. Examples of non- transitory machine-readable storage media include read-only memory, an optical disk drive, memory disk drive, and random access memory. At least part of the methods, systems, and techniques described in this specification may be controlled using a computing system comprised of one or more processing devices and memory storing instructions that are executable by the one or more processing devices to perform various control operations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Drawings are presented herein for illustration purposes, not for limitation. The foregoing and other objects, aspects, features, and advantages of the disclosure will become more apparent and may be better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:

[0055] Fig. l is a view of a cooling tower with a plume emanating therefrom where a system including a plurality of spaced-apart collectors is positioned above or within the cooling tower to collect fluid from the plume, according to illustrative embodiments of the present disclosure;

[0056] Figs. 2A-2C are cross-section views of three different positions at which one or more collectors can be installed: inside a cooling tower before a fan (Fig. 2A), in a fan shroud (Fig. 2B), and after and over a cooling tower along a primary direction of gas flow (Fig. 2C), according to illustrative embodiments of the present disclosure;

[0057] Fig. 3 is a photograph of an experiment that included testing a system of parallel collectors over one cooling tower outlet in a row of cooling towers results in a reduced water plume density indicating fluid collection, according to illustrative embodiments of the present disclosure;

[0058] Fig. 4 is a graphical plot of the normalized cooling efficiency of a cooling tower before and after installing a plurality of collectors over the cooling tower outlet showing no significant change in cooling tower performance as a function of time, according to illustrative embodiments of the present disclosure;

[0059] Figs. 5A-5C are side views of three different levels of porosity in porous collectors, where the low porosity example (Fig. 5A) results in rapid straightening of the flow and minimal droplet capture, the “optimal” porosity example (Fig. 5B) results in efficient capture of droplets, and the high porosity example (Fig. 5C) results in most droplets passing through without impacting any solid surface of the collectors, according to illustrative embodiments of the present disclosure;

[0060] Fig. 6 is a block flow diagram of a method for collecting fluid from a gas stream, according to illustrative embodiments of the present disclosure;

[0061] Figs. 7A-7E are views of a mesh collector, according to illustrative embodiments of the present disclosure; and

[0062] Figs. 8A-8D are views of a system for collection of fluid from a gas stream using collectors disposed about a central axis, according to illustrative embodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

[0063] Described herein are, inter alia, systems for collecting fluid from a gas stream that include one or more porous (e.g., mesh) collectors disposed along a primary direction of flow of the gas stream and methods of their use. Fluid may be passively collected from the gas stream when the collector(s) are aligned with the flow and the flow has a complex velocity. That is, one or more porous collectors may be disposed to exploit a non-axial component of velocity that does not point along a primary direction of flow of a gas stream. In some embodiments, a swirl component of velocity is imparted actively (e.g., by a fan or other airflow promoting device) or passively (e.g., by one or more turbulence inducing structures, such as portions of collectors joined together at an angle). The swirl component of velocity may include or be, for example, a tangential component, a radial component, or a rotational component. For example, while a conventional fan generally pushes air in a primary direction of flow, it may also impart a swirl component to the velocity as a result of the gas stream interacting with its rotating fan blades. In some embodiments, porous collectors are substantially parallel (e.g., with 5 degrees of) a primary direction of flow of a gas stream and spaced apart in a direction substantially perpendicular (e.g., within 5 degrees) to the primary direction thereby effectively having an asymmetric porosity where the gas stream is largely unimpeded along the primary direction while being relatively impeded in a direction of the swirl component of its velocity such that fluid is collected from the gas stream by inertial impact of the fluid with the collectors at least due to the swirl component. By constructing the porosity (e.g., mesh size and open area), dimensions, and position and orientation of the porous collectors, as described in further detail subsequently, a system can be tuned to operate within desired parameters such target fluid collection percentages and target pressure drops across the collector(s). By exploiting the swirl component of velocity that is present in certain gas streams, such collection can occur passively without the need for installing and/or providing additional electrical power beyond that already present.

[0064] In some embodiments, a system includes a series of mesh collectors, each including one or more wires, that are disposed with a vertical orientation on top of a fan exhaust. Fig. 1 shows a simplified sketch of how collectors could be arranged after and over a gas outlet, in this case of a cooling tower, where a fan (located inside the cooling tower) pushes the gas stream to ambient. The flow that comes out of the fan has a velocity with an axial component along a primary direction of flow for the gas stream out of the cooling tower (e.g., parallel to a plane normal for the plane of the gas outlet in the case of the illustrated cooling tower) as well as a swirl component that is imparted by the fan. The gas stream includes fluid dispersed therein, as is the case for typical gas streams used in cooling towers, as indicated by the plume that forms when the fluid containing gas stream interacts with ambient as it exits the gas outlet. As the flow passes through one or more meshes, droplets are collected by inertial impact on the mesh wires, and the swirl velocity is reduced because of the pressure drop through the mesh collectors in the horizontal direction. At the distal end of the collectors (relative to the primary direction of flow), the flow is straighter (lower swirl) and has less liquid content as liquid droplets are captured on the meshes. Because the meshes are vertical (relative to the primary direction of flow) and spaced apart, the vertical pressure drop may be minimal and the cooling tower fan performance may be not affected significantly. Moreover, because the meshes are vertical, the liquid droplets can shed down from (e.g., along) the mesh at least in part due to gravity when they become large enough as they coalesce. A gutter or other channel may be placed at the bottom of the mesh to collect the liquid and channel it to a re-use location, for example back to the cooling tower. (In some embodiments, fluid is simply allowed to drip back into the cooling tower, for example to be recycled without specifically redirecting it to a fluid input for the tower.) By reducing the liquid content of the plume that may be formed naturally at or near the gas outlet, the plume is less opaque, which may help with visibility around the plume and alleviate safety hazards due to freezing of the plume downstream or corrosion on nearby surfaces (e.g., in a dense industrial setting).

[0065] While the example illustrated in Fig. l is a common arrangement that could be used for collector(s) disclosed herein, systems are not limited to use in such applications. Collector(s) may be used in combination with other gas streams other than those emanating from a cooling tower. For example, collector(s) may be disposed (e.g., installed) at gas vents, at exhausts, in ducts, after ducts, in HVAC systems, or other locations where removal fluid from a gas stream is desirable.

[0066] The following sections describe, inter alia, design considerations for the construction and placement of collectors that may be useful for tailoring a system to its intended application (e.g., particular gas stream, gas outlet, and/or duct). Those of ordinary skill in the art will readily appreciate that there is generally a synergistic effect between the different aspects of collectors (e.g., in terms of their position, orientation, dimensions, materials, etc.) that means a wide range of embodiments may be sufficiently suitable (e.g., to accomplish a desired fluid capture percentage) for any given application. For example, one parameter, such as collector size, may be changed to accommodate for, for example, ease of installation, if another parameter, such as number of collectors or collector spacing, is changed correspondingly without significantly altering the overall system performance and/or suitability.

Collector Positioning

[0067] Generally it is desirable to place a collection system in a location that allows the capture of a significant amount of fluid (e.g., liquid droplets) from the gas stream. In the case of liquid droplets that are already entrained in the flow, collector(s) may be placed inside a gas duct (e.g., pipe), immediately following a gas outlet (e.g., exhaust), or further downstream of an outlet. In the case of liquid droplets actively forming in a gas stream (for example due to condensation), collector(s) may be placed further downstream, in a location where a sufficient number of liquid droplets have formed for the desired result. For example, collector(s) may be placed after and over a gas outlet (e.g., within 20 m, within 10 m, or within 5 m of a gas outlet) such that ambient air can mix into the gas stream prior to flowing through the collector(s) thereby facilitating natural condensation to enhance collection of the fluid when the gas stream gets to the collector(s).

[0068] In some embodiments where the application is at a cooling tower, collector(s) may be placed inside the tower or at the outlet of a fan shroud to capture the drift and any condensation that happened inside the tower. It can alternatively be placed above the fan shroud outlet, in which case further mixing with ambient air to promote additional condensation may be promoted in some embodiments. Figs. 2A-2C show a variety of locations at which collectors may be disposed with respect to a cooling tower: inside (Fig. 2A), in a fan shroud (Fig. 2B), and after and over (“above”) (Fig. 2C). Note the vertical black arrows showing evaporative cooling indicate the primary direction of gas flow for the gas stream, which exits the cooling tower through its outlet at the top, while the fan, which may already be present as part of a conventional cooling tower, imparts (e.g., introduces or enhances) a swirl component to velocity of the gas stream. Note further that, in some embodiments, a fan can impart a swirl component of velocity to a gas stream in its vicinity even prior to the gas stream passing through the fan, for example if of sufficient size and or rotating at sufficient speed, such that arrangements of collectors as shown in Fig. 2A may be viable to collect fluid from the gas stream.

[0069] Moreover, while the collectors illustrated in Figs. 2A-2C are substantially parallel (e.g., within 5 degrees) to the primary direction of flow of the gas stream (are vertical) and are mutually substantially parallel, collectors need not necessarily be so disposed. Collectors may be angled (e.g., tilted) relative to a primary direction of flow of a gas stream, for example by an angle of at least 15 degrees, at least 20 degrees, at least 25 degrees, or at least 30 degrees. Collectors may be (e.g., additionally or alternatively) not mutually parallel. For example, collectors can be disposed at angles relative to each other, in any direction (e.g., perpendicular to a primary direction of flow). Collectors may be planar. Collectors may be panels (e.g., as discussed further subsequently). Collectors may have a curved, circular, or polygonal crosssection taken in a plane perpendicular to a primary direction of flow. Where multiple collectors are included, they may be concentric with one another. Collectors may be evenly spaced or may be irregularly spaced (e.g., to account for varying magnitude of a swirl component of velocity of a gas stream across a cross section of the gas stream perpendicular to a primary direction of flow. [0070] In some embodiments, collector(s) are disposed prior to a fan along a primary direction of flow of a gas stream within 20 m, within 10 m, or within 5 m of the fan. In some embodiments, collector(s) are disposed after and over a gas outlet (e.g., of a cooling tower) within 20 m, within 10 m, or within 5 m of the outlet. In some embodiments, collecting occurs at a position along a direction of flow prior to the gas stream exiting a gas outlet. In some embodiments, collecting occurs after a gas stream exits a gas outlet, for example within 20 m, within 10 m, or within 5 m of the gas outlet, for example after the gas stream escapes to ambient. [0071] An experimental installation of collectors was tested at a cooling tower for a power plant to demonstrate feasibility of passive fluid collection with collectors. Fig. 3 shows a series of cooling towers where collectors are installed after and over the gas outlet of one of the towers (indicated by the black arrow). As shown in the figure, a significant portion of the water can be captured with this design as evidenced by the significant reduction in the water plume density. Furthermore, the performance of the tower was not significantly impacted by the system as shown in Fig. 4, which plots the normalized cooling efficiency of the tower as a function of time since system installation. The cooling efficiency is a function of the hot and cold water temperatures (THW and Tew, respectively), as well as ambient wet bulb temperature (TWB) as defined in Equation 1 below. The values in Fig. 4 are normalized by the average cooling efficiency over the same time period.

Anisotropy of Porous Collectors

[0072] A system may include one or more collectors. When a plurality of collectors are included and similarly aligned, there is an effective porosity along a primary direction of flow of a gas stream based on how the collectors are spaced and a porosity in other direction(s) defined by porosity of the collectors themselves. The relative porosities along the different directions can be controlled (e.g., optimized) by design choice of which collectors to use and how to arrange and space them. Figs. 5A-5C show examples where three collectors are spaced apart in one direction and each have a porosity in a perpendicular direction. Generally, porosity along a primary direction of flow (the axial component of velocity) is designed to be relatively low to minimize reduction in flowrate (which could negatively affect other processes upstream). In some embodiments, flowing a gas stream over one or more collectors causes an axial component of velocity to be reduced less (e.g., at least 2x less, at least 3x less, at least 5x less, at least lOx less) than a swirl component of the velocity is reduced relative to initial values of the axial component and the swirl component, respectively. Low porosity along a primary direction of flow may result in a relatively small pressure drop across collector(s), which may mean that operation of other components does not need to be altered to accommodate for the presence of the collector(s), for example fan power may be able to remain constant relative to the power used without the collector(s) installed. In some embodiments, a pressure drop across collector(s) is no more than 50% (e.g., no more than 25% or no more than 10%) of an initial pressure of a gas stream immediately prior to the collector(s).

[0073] Generally porosity aligned with a swirl component of velocity for a gas stream will be reasonably optimized for desired collection, which may be a high percentage (e.g., at least 60%) or relatively low percentage (e.g., at least 10%) of initial fluid in a gas stream. Fluid (e.g., droplet) capture rate will depend on various factors such as, for example, one or more of internal geometry of porous structure of the collector, its overall porosity (e.g., average porosity and/or gradient of porosity), droplet size distribution, and air speed. Porosity may be tuned as a function of these or other parameters, as discussed subsequently.

[0074] When choosing where and how to place collector(s), effects of interaction with the collector(s) on flow characteristics of a gas stream may be considered. As shown in Figs. 5A-5C, a very low porosity would straighten the flow very fast and would lead to most droplets (dots with trajectories mapped with arrows) not being captured while, on the opposite end of the spectrum, a high porosity would mean that most droplets can pass through the porous medium without impacting any solid collection surface. An “optimal” porosity may therefore exist to capture droplets as they travel through the porous medium without undesirably altering flow characteristics.

Collector Dimensions

[0075] The dimensions of collector(s) in one or more planes non-parallel (e.g., perpendicular) to gas flow are generally chosen to be large enough so that a sufficient amount of fluid-carrying flow passes through it. In some applications, it may be desired that as much liquid as possible is collected, in which case the diameter of the collector shall be at least the diameter of the liquid-carrying gas flow.

[0076] Dimension(s) of collector(s) in a primary direction of flow (defining an axial component of velocity) are large enough to allow fluid (e.g., droplets) to be captured. In some embodiments, one or more dimensions are linked to a horizontal collection rate: droplets have to travel enough horizontally so that the target collection rate is reached. If droplets need to travel a distance I horizontally to be captured, have an average vertical velocity v_v and an average horizontal velocity Vh, then they need to spend a time l/vh flowing over a collector. Therefore, a height of a collector should be at least v_v*l/vh to meet the desired collection rate with the collector. Using multiple collectors can change a determination of useful or necessary height requirements for the collectors.

[0077] In some embodiments, a system includes an array of substantially parallel (e.g., within 5 degrees) meshes that are parallel to a primary direction of flow. (Such embodiments are non-limiting as meshes do not need to be parallel and can also be angled with respect to the flow axial direction.) Generally in such cases, the gas stream travels between the meshes, and when the gas stream has a swirl component of velocity, it also passes through the meshes. As it passes through the meshes, fluid is collected (e.g., liquid droplets impact and are retained on the meshes). With appropriately designed porous structures (e.g., meshes), the fluid collection can be an appreciable percentage of initial fluid in the gas stream (e.g., at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70% of initial fluid).

Porous Structure Parameters [0078] In some embodiments, a collector may include a mesh. A mesh may include one or more wires. One or more wires may be arranged a two-dimensional mesh, for example forming an array of square or rectangular openings (referred to as a “square mesh” or “rectangular mesh,” respectively). Other opening shapes, for example polygonal shapes, may be used depending on, for example, how wire(s) are arranged in a mesh. Additionally, different wire cross-sections may be used, for example circular, rounded, or polygonal cross sections. A one-dimensional mesh (e.g., a one dimensional array of wires) may also be used in certain embodiments, which may include parallel (or non-parallel) wires running along a same direction (e.g., forming a zig-zag type arrangement). Similarly, for non-mesh porous structures, pores may have different shapes (e.g., rectangular, circular, square, polygonal) and may be arranged in a one-dimensional or two-dimensional array that may be a regular array or an irregular array (e.g., with pore or mesh sizing that changes over the collector surface, for example to accommodate for changing velocity along the collector(s)). Wire diameters, distance and angle between wires, and open area are some specific parameters that may be tuned for a given mesh collector. Similarly, pore size, pore shape, and pore separation may be tuned in non-mesh porous collectors, such as perforated or stamped sheets of material (e.g., metal or plastic). A wire may include an electrically conductive material (e.g., metal), non-conductive material (e.g., plastic). A wire may be coated with a material to change (e.g., increase or decrease) a surface tension of the wire (e.g., to promote coalescing and/or shedding of collected fluid).

[0079] When a square mesh is selected, at least two parameters can be tuned: wire diameter (which may be taken as a largest cross sectional dimension for non-circular wires), and open area (which is based on distance between wires and wire diameter). Wire diameter may be selected so that a minimum fraction of droplets that are directed toward the wire (e.g., by a swirl component of velocity) get captured by inertial impact. The impact efficiency can generally be characterized by a Stokes number. The Stokes number should be high enough and generally above 0.1 (St>0.1). In some applications, a Stokes number of at least 0.05 (or even lower) may be suitable. In some embodiments, a higher Stokes number may be desirable, for example at least 0.2, at least 0.5, at least 1, or at least 2. Stokes number may be given by the following formula for a porous structure of a collector used to perform fluid collection:

where Rd is an effective radius (e.g., droplet radius) of the fluid in the gas stream (e.g., an average droplet radius), Rc is a characteristic feature size (e.g., an average wire radius in a mesh collector or average pore separation in a non-mesh porous collector), pi is a density of the fluid in the gas stream, tZis speed of the flow of the gas stream, and Tj_g is dynamic viscosity of the gas stream.

[0080] The percentage of water that is captured when the flow passes through a single mesh can then be given by:

where OA is the open area fraction of the porous structure (e.g., mesh) of a collector.

[0081] The percentage of water capture after the flow passes through n collectors is

[0082] In some embodiments, when a certain water capture rate J] is needed or desired, wire diameter and open area can be tuned to achieve it based on the previous formulae.

[0083] Another important consideration for collector(s) in certain applications is fluid (e.g., water) shedding (e.g., drainage) from the collector(s). Once liquid droplets collect on a collection surface of a collector, they are held by surface tension forces. As more droplets coalesce, the aggregate droplet grows in size. When a droplet reaches a certain size, gravity overcomes surface tension and it sheds (e.g., falls and/or flows down). A gutter or channel may be placed at the bottom to capture the dripping fluid (e.g., water or other liquid).

[0084] Another force in play is air drag from the flow, which can dislodge captured droplets from a collector and re-entrain them into the flow, which is generally undesirable. Therefore, in some embodiments, wire diameter and distance between wires (or other pore size and pore separation) should also be selected, in conjunction with surface tension of the material, to ensure that surface tension forces can hold droplets in place in the presence of gas flow while also shedding fluid, due at least to gravity, as desired. As an example, thicker wires can provide more surface area for surface tension forces to hold the droplets on a mesh. Lower distance between the wires may also enable droplets to be held by multiple wires at once, which provides additional surface tension force. In some embodiments, less than 25% (e.g., less than 20%, less than 15%, less than 10%, less than 5%, less than 2%, or less than 1%) of the fluid collected on collector(s) is re-entrained into the gas stream as the gas stream flows over the one or more collectors.

[0085] A coating may also be applied to a mesh (e.g., including one or more wires) or other porous structure to change (e.g., increase or decrease) surface tension to a desired value for a given system. For example, a generic collector design may be tuned to a particular installation using one or more coatings. A coating may be reapplied periodically if collector(s) are used in an environment that degrades the coating. A coating may also be used in circumstances where porous structure (e.g., mesh) material choice is primarily dictated by other considerations such as mechanical (e.g., cost, processability) or cost but further tuning of surface tension is desired.

[0086] Tuning parameters of wire diameter (or pore separation), wire spacing (or pore size), and pressure drop through a collector is therefore often desirable to facilitate desired shedding (e.g., drainage) of fluid from collector(s), for example in applications where fluid harvesting is desired (e.g., for recycling or subsequent alternative use).

Porous Structure (e.g.. Mesh) Height and Spacing

[0087] Collector height and spacing may be determined based on the target collection rate. Each collector has a collection rate for a given gas stream (e.g., based on fluid content, velocity, and collector parameters, such as porous structure height, spacing, and sizing), and that dictates how many collectors a particular flow parcel needs to pass through to reach the target collection rate. Collector spacing and height need to be selected so that fluid can cross the necessary number of collectors (to achieve the target collection rate, or better) before leaving the region where the collector(s) are disposed. For example, if each collector captures 50% of droplets and target collection rate is 87.5%, then the gas stream needs to cross 3 collectors before leaving the system.

[0088] As an example, in some embodiments, if spacing between collectors is d, then the horizontal distance droplets need to travel is I = 3d, and the height of the system (assuming uniform horizontal gas speed, i.e. a small horizontal pressure drop) needs to be v_v.— = v_v.— . vh ^vh

Note that in general, gas speed is decreased as flow goes through collectors (since they are at least partial barriers) and thus the formula above is approximate as it assumed constant horizontal velocity, Vh. Those of ordinary skill in the art will readily understand how a system accounting for variable horizontal velocity can be modeled and therefore designed for. As illustrated by this analysis, mesh spacing and height are generally proportional to each other. Therefore, when considering only target collection rate, one may be able to use short collectors that are close together (more collectors in total) or long collectors that are further apart (less collectors in total). Factors like (but not limited to) construction costs (e.g., materials prices), installation factors (e.g., connection points for collectors in a particular system, labor and shipping for installation), and desired flow characteristics (e.g., amount of flow straightening) can contribute to a particular choice of collector number and dimensions amongst potentially suitable choices.

Mesh Tensioning and Mounting

[0089] In some embodiments, maintaining the straightness of the mesh under flow conditions is important. For example, collector vibration and movement may be undesirable to avoid losing droplets of fluid (e.g., to re-entrainment into the gas stream) that was already captured by the collector. Vibration may be of special concern for certain types of porous collectors, such as mesh collectors, especially those with smaller (and therefore less rigid) wire(s). Therefore, in some embodiments, having a rigid collector (e.g., mesh) may be desired to mitigate the effects of movement and/or vibration.

[0090] If a collector does not have enough rigidity from its basic construction, for example its mesh or other porous structure, various ways can be employed in various embodiments to provide additional rigidity. A collector may be maintained under tension. A rigid frame may be employed to hold a collection surface (e.g., mesh) of a collector, for example made of metal or thick plastic. The frame may be used to provide constant tension to the collection surface. Stiffening members, such as rods and/or cables, may be provided, for example attached at their end(s) to a frame for the collector. Thus, a mesh or porous structure may be designed according to preferred fluid capture and gas flow criteria while a small number of stiffening members are added that may improve rigidity with relatively minimal impact on collection and flow performance (e.g., due to being relatively spaced apart on a collector). As one example, rod(s) and/or cable(s) may be woven into a relatively less rigid mesh. Rods and/or cables may be attached to a porous collection surface (e.g., mesh), for example at a periphery of the surface with tension applied at those attachment points. Tensioned cables and/or rods may run along and/or perpendicular to a collection surface (e.g., mesh or porous structure) of a collector with attachment mechanism(s) provided to connect the meshes to these cables.

[0091] In some embodiments, a collector mesh is affixed to a more rigid metal edging or frame on the sides and is kept under tension. For example, one or more springs can apply tension to a metal edging attached to a collector. A tensioning system may apply tension force to a rigid edging in order to achieve a more uniform transfer of force to the collector. Tensioning can be done using springs or turnbuckles, for example. Pre-tensioning a mesh collector can reduce potential deflections of the mesh due to wind or vibrations.

[0092] In some embodiments, rigidifying members (e.g., rods) are added along the length of a collector to increase rigidity of the collector. In some embodiments, one or more tensioning cables (e.g., metal cables) are run through a collector (e.g., through openings of a mesh collector). Tensioning cable(s) may be attached to a rigid frame or edging such that they tension a mesh collector thereby straightening it. Additionally an edging/frame for a collector may be specifically designed to house tensioning cable(s) so that the weaving it through the edge/frame could be done easily (e.g., by running the tensioning cable(s) over one or more capstans). The edge/frame would be fixed to the mesh collector uniformly so that when the cable is pulled in tension it applies the tension force to the entirety of the mesh as a well distributed force.

Collector Examples

[0093] Fig. 6 is a block flow diagram for example method 600 of using collector(s) to collect fluid from a gas stream. For example, collector(s) according to Figs. 7A-7E, discussed subsequently, can be used to perform method 600. In step 602, a gas stream is flowed, where the gas has a velocity with an axial component along a primary direction of flow of the gas stream and a separate swirl component. The swirl component may be a tangential, rotational, or radial component of velocity or a combination thereof. For example, the swirl component may be imparted (e.g., introduced or enhanced) by an active device, such as a fan or other powered circulation mechanism. As another example, that can be used alternatively or additionally with the preceding example in some embodiments, the swirl component may be imparted (e.g., introduced or enhanced) passively, for example by one or more turbulence inducing structures, such as comers or other flow disrupting shapes, such as those that may be formed by a particular joining of different collectors. Other examples of turbulence inducing structures useable in various embodiments include baffles and wind breaks. In step 604, fluid is collected from the gas stream on one or more porous collectors (e.g., mesh collectors) at least due to the swirl component. As described previously, exploiting the swirl component of velocity specifically enables a low pressure drop to be realized along a primary direction of flow of a gas stream while also collection an appreciable portion of fluid from the gas stream (e.g., at least 10% of initial fluid or higher). In optional step 606, the collector(s) used to collect fluid in step 604 may be aligned such that they additionally straighten flow of the gas stream. In optional step 608, the fluid is shed from the collector(s) due, at least in part, to gravity. For example, once sufficient fluid has collected on a collector, gravity may induce shedding of the fluid.

[0094] Figs. 7A-7E show views of example collectors 700. Referring first to Figs. 7A- 7B, an example collector 700 includes wire mesh 710. Wire mesh 710 is a 2D mesh (some embodiments include a ID mesh). As can be seen from Fig. 7B, collector 700 is non-planar. Gutter 760 attached to collector 710. Wire mesh 710 can be made out of conductive material (e.g., metal) or non-conductive material (e.g., plastic). In some embodiments, wire, especially of large diameter, is more mechanically rigid and therefore better suited than plastic. Gutter 760 is attached to mesh 710 and includes collection wings 762a-b and tubular member 764. Tubular member 764 has a circular cross section, but tubular members with other cross sections can also be used, such as tubular members with rectangular or triangular cross section. As shown in Fig. 7B, gutter 760 is in fluid communication with fluid conduit 770 that can be used to drain collected fluid towards a periphery of a system. In some embodiments, gutter 760 and fluid conduit 770 are a common structure (e.g., a single piece of tubing).

[0095] Referring now to Figs. 7C-7E, another example collector 700 includes wire mesh 710 and collection frame 714. Collector 700 is planar. An edge of collection frame 714 surrounds a portion of mesh collection surface 710 around at least a portion of an outer perimeter of collection surface 710. The edge is a J-edge; a curved portion 714b of the J-edge surrounds a portion of collection surface 710 around at least a portion of an outer perimeter of collection surface 710. Fig. 7E shows a close up along a top portion of the edge of collection frame 714 and Figs. 7C and 7D show close ups along a bottom portion of the edge of collection frame 714. Mesh collection surface 710 is tack welded at a plurality of locations to collection frame 714 (tack welds are hidden by edge of collection frame 714). At bottom portion of collection frame 714 is formed at least partially from perforated sheet metal, as shown in Figs. 7D and 7E. A top portion of collection frame 714 is formed from non-perforated sheet metal, as shown in Fig. 7E. [0096] In some embodiments, one or more gutters (e.g., one or more channels) are disposed to collect fluid shed from the one or more collectors due, at least in part, to gravity. The one or more gutters may be disposed along bottom edge(s) of the one or more collectors. Two or more collectors may share a common gutter. In some embodiments, collector(s) shed fluid (e.g., drain the fluid), at least in part due to gravity, into a gutter. Fluid collected into a gutter may be transported to elsewhere, for example through collection conduit attached to the gutter. In some embodiments, the system includes a gutter disposed at an edge of collector(s) (e.g., wherein the gutter is a common gutter for at least two collectors or is a respective gutter for only one collector). In some embodiments, an edge of a collector is disposed in a gutter (e.g., wherein the gutter is attached to two opposing surfaces of a collector). In some embodiments, the gutter includes one or more collection wings (e.g., to direct collected fluid that has been shed down into the gutter). In some embodiments, the gutter includes a tubular member into which fluid can drain from collector(s) (e.g., and the tubular member has a circular or rectangular cross section). In some embodiments, the gutter is in fluid communication with a collection conduit. [0097] In some embodiments, a gutter is disposed at a bottom of a collector (e.g., each of a plurality of collectors). A gutter may be attached to a collector. A gutter may include a channel placed around the bottom of the collector. Collected fluid (e.g., water) sheds (e.g., drains) down a collector due to gravity and fall into the gutter. A gutter may be angled downward (e.g., relative to level ground) to more readily allow its contents to flow toward a periphery of a system. A gutter may be connected to collection conduit (e.g., a tube or pipe), for example at a periphery a system, to transfer the collected fluid. A gutter may be common to several collectors or each collector may have its own respective gutter. An edge of a collector may be disposed in a gutter. For example, the gutter may be attached to two opposing surfaces of the collector. A gutter may include one or more collection wings, for example to direct collected fluid down into the gutter. A gutter may include a tubular member into which fluid can drain away from the gutter. A gutter with collection wings may be shaped such that when droplets shed down a collector (e.g., a mesh), they are funneled into the gutter rather than hitting the collector-gutter interface and redirecting outwards and drip off of the system. [0098] Edging around one or more collectors may serve one or more of multiple purposes. An edge may enable facile handling of a panel so that it can be manipulated into and out of a fluid collection system. An edge may give rigidity to a panel by giving it a stiff border. In some embodiments, this reduces or eliminates the likelihood that a mesh collection surface will buckle under its own weight and is fixed (does not change size) at its overall dimension (e.g., 1.5 m x 1.5 m). A curved portion of an edge (e.g., a J-edge) may allow for easy access to a mesh-wire to edging interface, which allows for periodic spot welding (tack welds) along the length of a mesh. Welding together a mesh collection surface and collection frame at an edge thereof may ensure the mesh and J-edge behave as a single piece and/or may remove the ability for the mesh collection surface to rattle around inside of the edge. In some embodiments, for example along a bottom edge (e.g., J-edge), edge sheet metal may be perforated to allow for collected fluid to easily drain into guttering of a fluid collection system. A perforated edge may include metal that is perforated, for example with a linear density of from 3 to 5 holes per 10 mm, for example in SAE 304 stainless steel sheet metal. Such perforation can allow for sufficient drainage from the gutter for expected collection rates while also maintaining desired overall rigidity of a panel for facile handling and placement into a fluid collection system.

[0099] Fluid used in a system (e.g., for cooling in a cooling tower) may be, for example, water such as brackish water or seawater. Collecting fluid from a gas stream may have an added benefit of desalinizing water while also abating plume. That is, seawater may be used, for example for cooling, and pure, unsalinated water may be collected using a system described herein. In some embodiments, the system is combined with a cooling tower using seawater or other brackish water as feedwater, resulting in an ultra-low cost desalination system. A coastal power plant may use seawater in a cooling tower and an installed fluid collection system can then collect pure water coming out of the cooling tower, which can be used for domestic, industrial or agricultural needs.

[0100] Collected fluid may be much purer than source fluid that is then later dispersed in a gas stream. For example, collected water can be much purer than circulating water in a cooling tower. Contamination may enter collected fluid from the presence of drift that is also collected with the distilled water in the plume. In some embodiments, collected fluid has a purity (e.g., contaminants concentration) that is at least 5x and no more than 50x higher (e.g., at least 5x and no more than 50x lower contaminants concentration) than a purity of the fluid before the fluid entered the gas stream.

Collectors Disposed About an Axis

[0101] In some embodiments, collectors are disposed about a central axis. Two, three, four, five, six, or more collectors may be so disposed. The central axis may aligned with a primary direction of flow of a gas stream from which fluid will be collected (e.g., aligned with an axial component of velocity of the gas stream). The collectors may be disposed in alignment with one or more radial directions from the central axis. In some embodiments, collectors are disposed axisymmetrically about a central axis.

[0102] Thus, collectors may be disposed parallel to a primary direction of flow of a gas stream (e.g., an axial component of velocity of the gas stream) and extend from a center (defined by a central axis) to a periphery, for example as shown in Figs. 8A and 8D (discussed further subsequently). Thus, in some embodiments, collectors may be disposed substantially perpendicular (e.g., intending to be perpendicular or within a few degrees (e.g., within 5 degrees) of perpendicular, for example as limited by how collectors attach to a frame) to a swirl component (e.g., tangential component) of velocity for a gas stream. Such an arrangement can allow for the highest collection at every point in the system. Similar to embodiments with parallel collectors, open area of porous structures of collectors (e.g., of meshes), Stokes number of collectors, and a ratio of collector height to collector edge spacing (e.g., arc length separating outer edges of adjacent collectors disposed about a central axis) can all be tuned, independently or in some combination, to reach a desired collection efficiency of fluid from a gas stream. Such tuning may be made based on nature of fluid in a gas stream (e.g., droplet size distribution in the gas stream), axial component of velocity of the gas stream, tangential component of velocity of the gas stream, or some combination thereof, for example.

[0103] In some embodiments, collectors disposed in alignment with one or more radial directions do not lie precisely on the radial direction(s) but are offset slightly, for example due the manner in which they are attached to a frame. In some embodiments, some collectors are disposed along a same one of one or more radial directions and on opposing sides of a central axis. In some embodiments, there are an even number of collectors. Such collectors may be disposed in pairs about the central axis. Each pair may include one collector disposed on a first side of the central axis and another collector disposed on a second side of the central axis opposite the first side. Collectors may be disposed in a cylindrical arrangement, for example planar rectangular collectors disposed about a central axis (e.g., axisymmetrically disposed about the axis). In some embodiments, collectors are each disposed substantially parallel (e.g., within 5 degrees) to a plane on which a central axis lies. In some embodiments, collectors are tilted with respect to a central axis about which they are disposed (e.g., like fan blades that are stationary), for example at least 5 degrees, at least 10 degrees, at least 15 degrees, or at least 20 degrees. In some embodiments, collectors are not tilted with respect to a central axis about which they are disposed.

[0104] In some embodiments, collectors disposed about a central axis are disposed in a duct such that the central axis is aligned with a primary direction of flow of a gas stream (e.g., an axial component of velocity of the gas stream). Such collectors may span the duct.

[0105] In some embodiments, collectors disposed about a central axis are disposed after and over a gas outlet such that the central axis is aligned with a primary direction of flow of a gas stream (e.g., an axial component of velocity of the gas stream). The gas outlet may be one of a cooling tower or of a duct. The collectors span the gas outlet.

[0106] In some embodiments, the collectors are aligned with a primary direction of flow of a gas stream (e.g., an axial component of velocity of the gas stream). In some embodiments, collectors are tilted with respect to the primary direction instead (e.g., at an angle of no more than 20 degrees). In some embodiments, collectors disposed about a central axis are positioned and oriented such that a swirl component of velocity of a gas stream results in the fluid being collected from the gas stream on the collectors. In some embodiments, a system with such collectors is operable to collect at least 10% (e.g., at least 20%, at least 40%, or at least 60%) of initial fluid in the gas stream.

[0107] Collectors may extend from a central axis to an outer perimeter. The outer perimeter may be an ellipse, such as a circle. Such an arrangement may be used when, for example, a gas outlet has a circular perimeter. The outer perimeter may be a polygon, such as a rectangle (e.g., square). Such an arrangement may be used when, for example, collectors are disposed in a duct. Accordingly, in some embodiments, collectors span a gas outlet or a duct after and over which, or in which, the collectors are disposed. Additionally or alternatively, collectors may be substantially identically sized (e.g., intended to be constructed to be identical in size and so constructed within manufacturing tolerances) or of different sizes. Collectors may have a same width and different lengths (wherein length is taken along a direction parallel to a central axis and width is taken along a radial direction). Collectors may have a same length and different widths. In some embodiments, a collector may have a length along a central axis and a width extending along a radial direction with which the collector is aligned and the length is larger than the width, for example at least 1 ,5x or at least 2x as large as the width. Length and width of a collector may be chosen for any elsewhere described reason, for example to increase (e.g., maximize) fluid collection from a gas stream.

[0108] Collectors may be panels. Collectors may be planar, for example a planar panel. Generally, collectors are porous to allow for gas flow through the collectors, for example to minimize impact on flow (e.g., rate) from the collectors. Collectors may include a mesh, such a wire mesh. Wires may include a conductive material (e.g., a metal) and/or a non-conductive material (e.g., a polymer). Collectors may include a non-mesh porous structure. A rigid frame may hold a mesh. The mesh may be held under tension by the frame, for example including one or more tensioning cables, optionally that run through the mesh to impart the tension. Collectors may be grounded.

[0109] Collectors disposed about a central axis may be attached to a frame. Such a frame may include a central support and/or an outer cage. Collectors may be attached to a central support, an outer cage, or both. Any suitable attachment means may be used, such as one or more screws, bolts, or rivets, or a combination thereof. A collector may be electrically insulated from a frame to which it is attached. Collector may be electrically insulated from a frame to which they are attached. A frame may be conductive (e.g., metal) or non-conductive (e.g., polymer). A frame may be one piece or multiple pieces (“multi-piece”). For example, an outer cage and a central support may be one piece or separate pieces; the separate pieces may be attached together directly or only indirectly through collector(s). Additionally or alternatively, an outer cage may itself be made of multiple pieces, for example two or more rings that are attached together, such as with one or more rods. A central support may be a rod, for example with one or more attachment points for collector(s) at one or both of its ends and/or along its length. An outer cage may be open (e.g., skeletal or porous), for example in order to minimize impact to flow of a gas stream while still holding collectors in place as desired. Gas can flow through an open frame. A frame need not include an outer cage. A frame need not include a central support. A frame may attach to collectors at a top of the collectors, a bottom of the collectors, one or more sides of the collectors, or some combination thereof.

[0110] Collectors may be meshes (e.g., wire meshes) that are attached to a central support and an outer cage. A frame may rigidly hold collectors. For example, meshes may be held under tension by virtue of their attachment to an outer cage and central support of a frame. In some embodiments, meshes are attached to a collector frame that is itself attached a frame (e.g., an outer cage and/or central support).

[0111] Figs. 8A-8D illustrate system 800 that includes porous collectors 802 disposed about central axis 810. In the case of these figures, the arrangement is axisymmetric about the central axis. In other arrangements, collectors are not axisymmetrically disposed, for example where a distance (e.g., arc length) between every pair of adjacent collectors is not the same (distance is not constant), for example one or more pairs of adjacent collectors may be further apart or closer (e.g., measured angularly) than one or more other pairs of adjacent collectors. Each of collectors 802 is aligned with a radial direction (radial directions 808a-b are labeled for illustration). Collectors 802 include a wire mesh. (For clarity of illustration, collectors 802 are shown as solid in the figures.) System 800 may be disposed in a duct or after and over a gas outlet (e.g., of a duct) (not shown in Figs. 8A-8D). Collectors 802 disposed to be aligned with a primary direction of flow of a gas stream (e.g., an axial component of velocity of the gas stream) if the bottom ring is disposed in a plane substantially parallel (e.g., within installation tolerances) to a plane of the gas outlet (assuming the gas outlet has a planar shape, as is generally the case with, for example, cooling towers). That is, collectors 802 are not tilted with respect to central axis 810.

[0112] Collectors 802 are attached to a frame that includes central support 804 and outer cage 806. Therefore, the frame is a multi-piece frame. Central support 804 is aligned with central axis 810. Outer cage 806 is a skeletal outer cage and is therefore open. Outer cage 806 is made of multiple pieces, in this case three rings disposed concentrically with central support 804 and attached to each other independently of collectors 802 with support rods 807. Collectors 802 are attached to both central support 804 and outer cage 806.

Electric Field Enhancement [0113] In some embodiments, an electric field may be used to enhance fluid collection from a gas stream with one or more collection panels, for example in a system with collection panels disposed about a central axis. An electric field may act to direct charged fluid towards one or more collectors, for example grounded and/or conductive collector(s). Fluid may be charged naturally, for example due to its composition and/or as a result of one or more upstream interactions that were not deliberately intended to charge the fluid. Fluid may be intentionally charged in order to improve subsequent collection. Thus, in some embodiments, a pre-charging stage is included upstream of collector(s) to charge fluid in a gas stream as the gas stream flows by before interacting with the collector(s). A passive collection mechanism may still be the primary contributor towards fluid collection from a gas stream even when an electric field is used. An electric field may enhance collection by attracting fluid to droplets that would have passed through the mesh and makes them deposit on the mesh wires.

[0114] A pre-charging stage may include one or more electrodes. For example, an (e.g., ID or 2D) array of electrodes. The one or more electrodes may be maintained at a high voltage during operation. A high voltage may be, for example, at least 1 kV and, optionally, no more than 500 kV [e.g., a voltage of at least 5 kV at least 10 kV, at least 15 kV, at least 25 kV, at least 50 kV, at least 100 kV) (e.g., and no more than 250kV, no more than 100 kV, or no more than 50 kV)]. For example, the electrode(s) may be disposed near a grounded surface such that corona discharge occurs and ions are generated in a gas stream. In some embodiments, grounded surface(s) and electrode(s) operate together to charge passing fluid in a gas stream (e.g., by corona discharge). One or more grounded surfaces may be provided before and/or after (e.g., upstream and/or downstream of) electrode(s) of a pre-charging stage. Grounded surface(s) may be made of metal or other conductive material. The size and spatial distribution of grounded surface(s) can be tuned, if desired, to minimize impact to flow of a gas stream. Such tuning may be balanced by achieving desired charging of fluid passing by in a gas stream. An electrode may be a low radius wire or a needle, for example. Other suitable low radius of curvature geometries may be used. The grounded surface can be or include a mesh or a plate, for example. In some embodiments, as a gas stream (and fluid (e.g., droplets) therein) go through a pre-charging stage, ions attach to the fluid, which become electrically charged. Subsequently, the gas stream may flow towards one or more collectors. [0115] A pre-charging stage may be disposed in a duct or a cooling tower while collector(s) are disposed inside or outside the duct or cooling tower (e.g., after and over a gas outlet). Electrodes of a pre-charging stage, a grounded surface of a charging stage, or both, may be disposed in a plane substantially perpendicular (e.g., within installation and/or manufacturing tolerances) (e.g., within 5 degrees) to an axial component of velocity of the gas stream. A grounded surface of a pre-charging stage may be disposed in a downstream direction from one or more electrodes of the pre-charging stage. A grounded surface and/or one or more electrodes of a pre-charging stage may be sized and shaped to minimize interference with a gas stream (e.g., a grounded surface may consist of large open meshes and/or one or more electrodes may be small needle(s) or wire(s) with sufficient radius of curvature). In some embodiments, a pre-charging stage may be disposed a short distance from collector(s), for example within a distance of one characteristic dimension (e.g., diameter) of a gas outlet. In some embodiments, larger separations may also be used. In some embodiments, a pre-charging stage is adjacent to collector(s), for example with minimal separation distance (e.g., with no space therebetween deliberately provided). U.S. Patent No. 10,882,054 describes systems and methods for charging fluid in a gas stream that can be used in and/or with a pre-charging stage, the relevant disclosure of which is hereby incorporated by reference herein.

[0116] In some embodiments, one or more electrodes are disposed near (e.g., within 0.5 m of) each of one or more collectors. For example, there may be one electrode per collector, more than one electrode per collector, or at least some of multiple collectors having more than one associated electrode. In general, it is desirable that a gas stream can flow through (e.g., around) the one or more electrodes (e.g., due to a swirl component of velocity of the gas stream) to minimize impact on the gas stream from the electrode(s). A high voltage (e.g., with a same polarity as charged fluid) may be maintained by the one or more electrodes. A high voltage may be, for example, at least 1 kV and, optionally, no more than 500 kV [e.g., a voltage of at least 5 kV at least 10 kV, at least 15 kV, at least 25 kV, at least 50 kV, at least 100 kV) (e.g., and no more than 250kV, no more than 100 kV, or no more than 50 kV)]. An electrode may be a wire (e.g., included in a mesh), a mesh, or a tube. Electrodes may be arranged in a ID or 2D array. Collector(s) may be grounded and conductive to facilitate desired electric field generation (e.g., that points towards collector(s)). Such an arrangement would apply an electric field to a gas stream that attracts fluid toward the collector(s). This effect can enhance fluid collection efficiency. Therefore, the same overall efficiency can be reached with fewer collectors and/or smaller collectors (e.g., shorter collector height, e.g., along a central axis).

[0117] Voltage may be tuned to induce a desired electric field using one or more electrodes (e.g., and a grounded collector), for example having a desired field direction and/or field strength. Similarly, electrode design (e.g., geometry, arrangement, and/or material choice) may be chosen based on a desired field direction and/or field strength. A generated electric field may be local to one or more electrodes and a single collector. An electric field may be sufficient to locally direct fluid towards a collector. Electric fields generated by associated electrode(s) and a collector may have no impact on other collector(s). In some embodiments, an electric field generated using one or more electrodes does not interact with an electric field generated by one or more other electrodes.

[0118] One or more electrodes may be used to apply an electric field without themselves causing charging of nearby fluid in a gas stream (e.g., generating any corona discharge). For example, corona discharge may be generated using a pre-charging stage, to charge fluid in a gas stream, and then one or more electrodes disposed near collectors may be used solely to apply an electric field that directs the charged fluid (e.g., without further charging the fluid). Electrode(s) (e.g., disposed near collector(s)) may be maintained at a voltage that causes generation of an electric field sufficient to direct nearby fluid in a gas stream toward collector(s) but does not charge the fluid. In some embodiments, electrode(s) are disposed near a collector (in an arrangement that includes multiple collectors) such that an electric field generated using the electrode(s) directs fluid from a gas stream towards no other collector than the collector near which the electrode(s) are disposed. That is, for example, collectors and electrodes may be disposed in collector-electrode pairs that each include a unique collector and a unique one or more of the electrodes and are separated apart from other pairs. In some embodiments, one or more electrodes are disposed on average closer to one collector than any other collector, for example at least 3x closer, at least 4x closer, at least 5x closer, or at least lOx closer on average. In some embodiments, collectors are planer and each set of one or more electrodes is disposed in a planar arrangement (one or more electrodes are planar). Such a collector and associated one or more electrodes may be disposed in substantially parallel planes (e.g., within 5 degrees) (e.g., separated by a distance of no more than 0.5 m). Collectors may be grounded while electrodes are maintained at a high voltage. Fig. 8D, described further subsequently illustrates an example of all of the features mentioned in this paragraph (though the features need not all be present or not present in an embodiment). One or more electrodes may be porous and/or spaced apart to allow a gas stream to flow through the electrodes (e.g., without substantially interfering with the flow of the gas stream).

[0119] Panels that include a collector and one or more electrodes that can be used in embodiments of a system are disclosed in U.S. Patent No. 11,123,751, the relevant disclosure of which is hereby incorporated by reference herein. (U.S. Patent No. 11,123,751 describes “emitter electrodes.” Such electrodes may be used to generate an electric field without causing or inducing emission (e.g., by corona discharge) or charging nearby fluid, as is preferred in embodiments of the present disclosure. For example panels can be disposed about a central axis, for example axisymmetrically.

[0120] In some embodiments, one or more electrodes comprises a wire (e.g., a tensioned wire) or a tube. In some embodiments, one or more electrodes form a mesh (e.g., a wire mesh) (e.g., a ID or 2D mesh). One or more electrically insulating members (e.g., each comprising one or more sheds) may be used to attach one or more electrodes to a frame to which one or more collectors are attached. In some embodiments, one or more electrodes are attached to an electrode frame and the electrode frame is attached to a frame to which one or more collectors are attached, for example by one or more electrically insulating members. In some embodiments, each of one or more electrodes is attached to a frame, to which one or more collectors are attached, by a unique set of one or more electrically insulating members. In some embodiments, one or more electrodes are attached to a frame (e.g., under tension), the frame being different from one to which one or more collectors are attached. Fig. 8D illustrates an example of such an arrangement that uses unique sets of electrically insulating members.

[0121] Referring back to Figs. 8A-8D, Figs. 8B-8C illustrate system 800 disposed in a path of flow of a gas stream. In Fig. 8B, system 800 includes pre-charging stage 816 that includes electrodes 817 that are used to charge fluid in the gas stream as it flows by. Precharging stage 816 also includes two rows of grounded surfaces 815a-b, one on either side of electrodes 817. Pre-charging stage 816 is disposed upstream of collectors 802. In Fig. 8C, a fan 818 is included and is disposed upstream of pre-charging stage 816 and collectors 802; precharging stage 816 is disposed between fan 818 and collectors 802. Pre-charging stage 816 (and/or fan 818, if present) may be disposed inside of a duct or cooling tower, for example, with collectors 802 (e.g., and the frame to which they are attached) disposed inside or outside of the duct or cooling tower. Thus, in some embodiments, the frame to which collectors 802 is attached can be readily installed atop a gas outlet [e.g., by affixing (e.g., attaching) the frame to the outlet]. For simplicity, collectors 802 attached to a frame are represented by a labeled box in FIGs. 8B-8C.

[0122] Fig. 8D illustrates an arrangement similar to Fig. 8A with the addition of sets of electrodes 812, in this case ID wire arrays, each associated with (e.g., disposed no more than 0.5 m from) one of the collectors, in planar pairs. Sets of electrodes 812 are each attached to outer cage 806 and central support 804 with a unique set of electrically insulating members 814. Multiple electrically insulating members 814 are shown for each set of electrodes 812 but, in some embodiments, a single electrically insulating member 814 may be used. Electrically insulating members 814 include multiple sheds. Each set of electrodes 812 includes multiple electrodes 812 but a single electrode (e.g., mesh or porous plate) may be used in some embodiments.

[0123] Electrically insulating members suitable for use in attaching collectors to a frame are disclosed in U.S. Patent No. 11,123,751, the relevant disclosure of which is hereby incorporated by reference herein. Additionally, electrodes (e.g., emitter electrodes) suitable for use in generating an electric field are disclosed in U.S. Patent Nos. 11,123,752 and 11,123,751, the relevant disclosure of each of which is hereby incorporated by reference herein.

[0124] In this application, unless otherwise clear from context or otherwise explicitly stated, (i) the term “a” may be understood to mean “at least one”; (ii) the term “or” may be understood to mean “and/or”; (iii) the terms “comprising” and “including” may be understood to encompass itemized components or steps whether presented by themselves or together with one or more additional components or steps; (iv) the terms “about” and “approximately” may be understood to permit standard variation as would be understood by those of ordinary skill in the relevant art; and (v) where ranges are provided, endpoints are included. In certain embodiments, the term "approximately" or "about" refers to a range of values that fall within 25%, 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than) of the stated reference value unless otherwise stated or otherwise evident from the context (except where such number would exceed 100% of a possible value). [0125] It is contemplated that systems, devices, methods, and processes of the disclosure encompass variations and adaptations developed using information from the embodiments described herein. Adaptation and/or modification of the systems, devices, methods, and processes described herein may be performed by those of ordinary skill in the relevant art.

[0126] Throughout the description, where articles, devices, and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are articles, devices, and systems according to certain embodiments of the present disclosure that consist essentially of, or consist of, the recited components, and that there are processes and methods according to certain embodiments of the present disclosure that consist essentially of, or consist of, the recited processing steps.

[0127] It should be understood that the order of steps or order for performing certain action is immaterial so long as operability is not lost. Moreover, two or more steps or actions may be conducted simultaneously. As is understood by those skilled in the art, the terms “over,” “under,” “above,” “below,” “beneath,” and “on” are relative terms and can be interchanged in reference to different orientations of the layers, elements, and substrates included in the present disclosure. For example, a first layer on a second layer, in some embodiments means a first layer directly on and in contact with a second layer. In other embodiments, a first layer on a second layer can include another layer there between.

[0128] Headers have been provided for the convenience of the reader and are not intended to be limiting with respect to the claimed subject matter. It will be readily apparent to those of ordinary skill in the art, especially in the context of the description itself, that feature(s) described under one or more of the headers used herein can be combined with feature(s) from one or more other of the headers used herein in various embodiments.

[0129] Certain embodiments of the present disclosure were described above. It is, however, expressly noted that the present disclosure is not limited to those embodiments, but rather the intention is that additions and modifications to what was expressly described in the present disclosure are also included within the scope of the disclosure. Moreover, it is to be understood that the features of the various embodiments described in the present disclosure were not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations were not made express, without departing from the spirit and scope of the disclosure. The disclosure has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the claimed invention.

Claims

What is claimed is:

1. A method for collecting fluid from a gas stream, the method comprising: flowing a gas stream, wherein velocity of the gas stream comprises an axial component along a primary direction of flow of the gas stream and a separate swirl (e.g., tangential, radial, and/or rotational) component; and collecting fluid from the gas stream on one or more porous (e.g., mesh) collectors disposed along the primary direction of flow, wherein the one or more collectors are aligned such that the fluid collects on (e.g., impact and remain on) the one or more collectors at least [e.g., only or substantially (e.g., at least 90% due to)] due to the swirl component of the velocity.

2. The method of claim 1, wherein the collecting occurs passively at least in part due to the swirl component.

3. The method of claim 1 or claim 2, wherein the one or more collectors are spaced apart in a direction non-parallel to the axial component of the velocity.

4. The method of any one of claims 1-3, wherein the one or more collectors are substantially parallel (e.g., within 5 degrees) to the axial component of the velocity.

5. The method of any one of claims 1-4, wherein the gas stream is flowed towards (e.g., through) a gas outlet to ambient (e.g., through a duct) and the collecting occurs as the gas stream flows toward the ambient.

6. The method of any one of claims 1-5, wherein a pressure drop across the one or more collectors is no more than 50% (e.g., no more than 25% or no more than 10%) of an initial pressure of the gas stream immediately prior to the one or more collectors.

7. The method of any one of claims 1-6, wherein collecting the fluid comprises collecting at least 10% (e.g., at least 20%, at least 40%, or at least 60%) of initial fluid in the gas stream.

8. The method of any one of claims 1-7, wherein flowing the gas stream over the one or more collectors causes the axial component of the velocity to be reduced less (e.g., at least 2x less, at least 3x less, at least 5x less, at least lOx less) than the swirl component of the velocity is reduced relative to initial values of the axial component and the swirl component, respectively.

9. The method of any one of claims 1-8, wherein less than 25% (e.g., less than 20%, less than 15%, less than 10%, less than 5%, less than 2%, or less than 1%) of the fluid collected on the one or more collectors is re-entrained into the gas stream as the gas stream flows over the one or more collectors.

10. The method of any one of claims 1-9, wherein the swirl component of the velocity is at least partially actively imparted to the gas stream.

11. The method of any one of claims 1-10, comprising rotating a fan to actively impart at least a portion of the swirl component of the velocity to the gas stream.

12. The method of any one of claims 1-11, wherein the swirl component of the velocity is at least partially passively imparted to the gas stream.

13. The method of any one of claims 1-12, comprising flowing the gas stream over one or more turbulence inducing structures [e.g., angled corners of the one or more collectors (e.g., where ones of the one or more collectors are joined together (e.g., at an angle))] to passively impart at least a portion of the swirl component of the velocity to the gas stream.

14. The method of any one of claims 1-13, wherein the gas outlet is an outlet of a cooling tower and a cooling efficiency of the cooling tower is reduced during the method by no more than 20% on average over a period of time relative to a baseline cooling efficiency of the cooling tower without the one or more collectors under otherwise equivalent conditions.

15. The method of any one of claims 1-14, wherein the gas outlet is an outlet of a cooling tower and a normalized cooling efficiency of the cooling tower is reduced during the method by no more than 20% on average over a period of time, wherein the normalized cooling efficiency of the cooling tower is a value normalized as a function of time during operation since installation of the one or more collectors.

16. The method of any one of claims 1-15, wherein the collecting occurs at a position along the direction of flow prior to the gas stream exiting a gas outlet (e.g., and prior to the fan, e.g. within 20 m, within 10 m, or within 5 m) (e.g., and after the fan, e.g. within 20 m, within 10 m, or within 5 m).

17. The method of any one of claims 1-15, wherein the collecting occurs after the gas stream exits a gas outlet (e.g., within 20 m, within 10 m, or within 5 m of the gas outlet).

18. The method of any one of claims 1-17, comprising shedding, at least in part due to gravity, at least a portion of the fluid collected on the one or more collectors into one or more gutters (e.g., channels) (e.g., disposed at a bottom surface of the one or more collectors) (e.g., and collecting the at least a portion of the fluid from the one or more gutters).

19. The method of claim 18, wherein the at least a portion of the fluid collected into the one or more gutters has at least 5x (e.g., at least lOx) lower contaminants and dissolved contents than circulating fluid from which the fluid was entrained into the gas stream.

20. The method of any one of claims 1-19, wherein flowing the gas stream along the one or more collectors straightens flow of the gas stream (e.g., relatively increases the axial component of the velocity).

21. The method of any one of claims 1-20, comprising providing the one or more collectors, wherein providing the one or more collectors comprises determining one or more of a number of collectors in the one or more collectors, a dimension (e.g., height and/or width) of each of the one or more collectors, a spacing between ones of the one or more collectors, a wire diameter, and open area in each of the one or more collectors (e.g., determined by pore size and/or wire spacing and wire diameter) based on one or more of a target fluid capture percentage, a target cooling efficiency for a cooling tower at which the one or more collectors are installed, and a target pressure drop across the one or more collectors.

22. The method of any one of claims 1-21, wherein each of the one or more collectors comprises a mesh of one or more wires defining openings in the mesh and collecting the fluid comprises collecting droplets of the fluid such that each of the droplets is in contact with at least one of the one or more wires of the mesh [e.g., is in contact with multiple wires (e.g., each of the droplets individually at least partially spans one of the openings on the mesh of one of the collectors)].

23. The method of any one of claims 1-22, comprising mixing ambient air into the gas stream after the gas stream exits a gas outlet prior to the collecting the fluid from the gas stream.

24. The method of any one of claims 1-23, wherein collecting the fluid from the gas stream comprises collecting condensed fluid from a region where the fluid condenses in the gas stream.

25. The method of any one of claims 1-24, wherein collecting the fluid from the gas stream comprises collecting water from a plume in the gas stream.

26. The method of any one of claims 1-25, wherein the fluid is liquid, vapor, droplets, drift or mist (e.g., of water) dispersed in the gas stream.

27. The method of any one of claims 1-26, wherein the fluid collects on the one or more collectors without using a voltage and/or electric field.

28. The method of any one of claims 1-27, wherein the one or more collectors are nonelectrified.

29. The method of any one of claims 1-28, wherein the one or more collectors is a plurality of collectors disposed about a central axis and aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream).

30. The method of claim 29, wherein the plurality of collectors is disposed axisymmetrically about the central axis.

31. The method of any one of claims 1-30, comprising charging the fluid in the gas stream upstream of the one or more collectors.

32. The method of any one of claims 1-31, comprising applying a non-charging electric field (e.g., to the charged fluid) to direct the fluid towards the collectors.

33. The method of claim 32, wherein the electric field is applied using electrodes disposed near (e.g., within 0.5 m of) the one or more collectors [e.g., wherein applying the electric field comprises applying a voltage (e.g., a high voltage) of a same polarity as the charged fluid to the electrodes] (e.g., wherein each of the electrodes is operable to generate an electric field that directs the fluid towards a respective one of the collectors).

34. The method of claim 33, wherein the electrodes are porous and/or spaced apart to allow the gas stream to flow through the electrodes (e.g., without substantially interfering with the flow of the gas stream).

35. The method of any one of claims 1-30, wherein the collecting occurs passively.

36. A system for collecting fluid from a gas stream, the system comprising: one or more porous collectors disposed along a primary direction of gas flow for a gas stream comprising fluid dispersed therein, wherein the one or more collectors are positioned and oriented such that a swirl component of velocity of the gas stream results in the fluid being collected from the gas stream on the one or more collectors.

37. A system for collecting fluid from a gas stream, the system comprising: one or more porous (e.g., mesh) collectors disposed along a primary direction of flow for a gas stream comprising fluid dispersed therein, wherein the one or more collectors each have a Stokes number (Si) of at least 0.05 (e.g., at least 0.1 or at least 0.2), wherein St = ^2RdPlU _with Rd is an effective radius (e.g., droplet radius) of the fluid in ig c the gas stream (e.g., an average droplet radius), Rc is a characteristic feature size (e.g., an average wire radius in a mesh collector or average pore separation in a non-mesh porous collector), pi is a density of the fluid in the gas stream, U is speed of flow of the gas stream, and Tj_g is dynamic viscosity of the gas stream.

38. The system of claim 31 or claim 32, wherein the one or more collectors is a plurality of collectors that are spaced apart in a direction non-parallel to the primary direction of gas flow.

39. The system of any one of claims 36-38, wherein the one or more collectors are aligned substantially parallel (e.g., within 5 degrees) to the primary direction of gas flow.

40. The system of any one of claims 36-38, wherein each of the one or more collectors is tilted with respect to the primary direction of gas flow (e.g., and is/are mutually parallel or and is/are mutually non-parallel).

41. The system of any one of claims 36-40, wherein each of the one or more collectors comprises a mesh (e.g., a ID or 2D mesh) (e.g., a rectangular or square mesh) comprising one or more wires.

42. The system of claim 41, wherein the one or more wires comprises (e.g., each comprise) a conductive material (e.g., a metal) and/or a non-conductive material (e.g., a polymer).

43. The system of claim 41 or claim 42, wherein the one or more wires are coated with a coating that changes (e.g., increases or decreases) the surface tension of the one or more wires (e.g., to promote coalescing and/or shedding of collected fluid).

44. The system of any one of claims 36-43, wherein the one or more collectors are disposed in a duct.

45. The system of any one of claims 36-44, comprising the gas outlet (e.g., wherein the gas outlet is an outlet of a cooling tower) [e.g., wherein the one or more collectors are aligned (e.g., parallel) with the primary direction of flow and span the gas outlet],

46. The system of any one of claims 36-45, comprising one or more gutters (e.g., one or more channels) disposed to collect fluid shed from the one or more collectors due, at least in part, to gravity (e.g., wherein the one or more gutters are disposed along bottom edge(s) of the one or more collectors) (e.g., wherein two or more collectors share a common gutter).

47. The system of any one of claims 36-46, comprising a fan to impart (e.g., introduce and/or increase) a (e.g., the) swirl component to velocity of the gas stream.

48. The system of claim 47, wherein the one or more collectors are disposed in a shroud of the fan.

49. The system of claim 47, wherein the one or more collectors are disposed prior to the fan along the primary direction of flow of the gas stream (e.g., within 20 m, within 10 m, or within 5 m of the fan).

50. The system of any one of claims 36-47, wherein the one or more collectors are disposed after and over a gas outlet (e.g., of a cooling tower) (e.g., within 20 m, within 10 m, or within 5 m of the outlet).

51. The system of claim 47, wherein the gas outlet is an outlet from which gas stream escapes to ambient.

52. The system of claim 50 or claim 51, wherein the one or more collectors are disposed after and over the gas outlet such that ambient air can mix into the gas stream after the gas outlet and prior to collecting the fluid from the gas stream by the one or more collectors.

53. The system of any one of claims 50-52, wherein the one or more collectors are disposed after and over the gas outlet such that the one or more collectors are disposed to collect condensed fluid from the gas stream in a region where the fluid condenses.

54. The system of any one of claims 36-53, wherein one or more of a number of collectors in the one or more collectors, a dimension (e.g., height and/or width) of each of the one or more collectors, a spacing between ones of the one or more collectors, a wire diameter, and open area in each of the one or more collectors (e.g., determined by pore size and/or wire spacing and wire diameter) is based on one or more of a target fluid capture percentage, a target cooling efficiency for a cooling tower at which the one or more collectors are installed, and a target pressure drop across the one or more collectors.

55. The system of any one of claims 30-48, wherein the one or more collectors have a curved, circular, or polygonal cross-section taken in a plane perpendicular to the primary direction of flow.

56. The system of any one of claims 36-55, wherein the one or more collectors comprises a plurality of collectors that are concentrically arranged.

57. The system of any one of claims 36-54, wherein the one or more collectors are each planar.

58. The system of any one of claims 36-57, wherein the one or more collectors comprises a plurality of collectors and ones of the collectors are physically attached together.

59. The system of any one of claims 36-58, wherein each of the one or more collectors is a panel (e.g., a planar panel) [e.g., comprising a rigid frame (e.g., that holds a mesh (e.g., under tension))].

60. The system of any one of claims 36-59, wherein the one or more collectors are each held under tension (e.g., each comprises a mesh held under tension) [e.g., by one or more tensioning cables (e.g., running through the mesh)].

61. The system of any one of claims 36-60, comprising one or more turbulence inducing structures [e.g., angled comers of the one or more collectors (e.g., where ones of the one or more collectors are joined together (e.g., at an angle))] that can introduce turbulence to the gas stream [e.g., to impart (e.g., introduce or increase) a swirl component of velocity to the gas stream],

62. The system of any one of claims 36-61, wherein the system is non-electrified.

63. The system of any one of claims 36-62, wherein the one or more collectors are nonelectrified.

64. The system of any one of claims 36-63, wherein the system is a passive collection system.

65. The system of any one of claims 36-64, wherein the system is operable to collect (e.g., arranged to collect) at least 10% (e.g., at least 20%, at least 40%, or at least 60%) of initial fluid in the gas stream.

66. A system for collecting fluid from a gas stream, the system comprising porous collectors disposed about a central axis.

67. The system of claim 66, wherein the collectors are disposed in alignment with one or more radial directions from the central axis.

68. The system of claim 66 or claim 67, wherein ones of the collectors are disposed in alignment with different ones of the one or more radial directions.

69. The system of any one of claims 66-68, wherein ones of the collectors are disposed along a same one of the one or more radial directions and on opposing sides of the central axis.

70. The system of any one of claims 66-69, wherein the collectors are disposed axisymmetrically about the central axis.

71. The system of any one of claims 60-63, wherein the collectors is an even number of collectors and the collectors are disposed in pairs about the central axis, each pair comprising one collector disposed on a first side of the central axis and another collector disposed on a second side of the central axis opposite the first side.

72. The system of any one of claims 66-71, wherein the collectors extend from the central axis to an outer perimeter and the outer perimeter is an ellipse (e.g., circle).

73. The system of any one of claims 66-71, wherein the collectors extend from the central axis to an outer perimeter and the outer perimeter is a polygon (e.g., rectangle).

74. The system of any one of claims 66-73, wherein the collectors are passive collectors (e.g., cannot be electrified).

75. The system of any one of claims 66-74, wherein the collectors are grounded.

76. The system of any one of claims 66-75, comprising a pre-charging stage operable to charge the fluid in the gas stream (e.g., using corona discharge), wherein the pre-charging stage is disposed relative to the collectors to be in an upstream direction (e.g., in an upstream direction when the collectors are disposed in a duct or after and over a gas outlet) (e.g., disposed after a fan that applies a swirl component of velocity to the gas stream).

77. The system of claim 76, wherein the pre-charging stage comprises one or more electrodes (e.g., low radius wires or needles) (e.g., operable to maintain a voltage of at least 1 kV and, optionally, no more than 500 kV [e.g., a voltage of at least 5 kV at least 10 kV, at least 15 kV, at least 25 kV, at least 50 kV, at least 100 kV) (e.g., and no more than 250kV, no more than 100 kV, or no more than 50 kV)]) (e.g., disposed in a plane substantially perpendicular to an axial component of velocity of the gas stream).

78. The system of claim 76 or claim 77, wherein the pre-charging stage comprises a grounded surface (e.g., a mesh or plate) (e.g., disposed in a plane substantially perpendicular to an axial component of velocity of the gas stream) (e.g., disposed in a downstream direction from the one or more electrodes).

79. The system of any one of claim 66-78, comprising a frame (e.g., a metal frame or non- conductive frame) (e.g., a one piece or multi-piece frame), wherein the collectors are attached to the frame.

80. The system of claim 79, wherein the frame comprises a central support aligned with the central axis (e.g., a rod) and the collectors are attached to the central support.

81. The system of claim 79 or claim 80, wherein the frame comprises an outer cage (e.g., a cylindrical or rectangular cage) and the collectors are (e.g., also) attached to the outer cage.

82. The system of claim 81, wherein the outer cage is open (e.g., is a skeletal outer cage or is porous).

83. The system of any one of claims 79-82, wherein the collectors are electrically insulated from the frame.

84. The system of any one of claims 60-83, comprising one or more electrodes disposed near (e.g., within 0.5 m of) each of the collectors (e.g., one electrode per collector, more than one electrode per collector, or at least some of the collectors having more than one associated

50 electrode), wherein the gas stream can flow through (e.g., around) the one or more electrodes (e.g., due to a swirl component of velocity of the gas stream) [e.g., wherein the one or more electrodes are attached to a frame (e.g., under tension)].

85. The system of claim 84, wherein the one or more electrodes are disposed such that an electric field generated using the one or more electrodes directs fluid from the gas stream towards no other of the collectors than the collector near which the one or more electrodes are disposed.

86. The system of claim 85, wherein the one or more electrodes comprises a wire (e.g., a tensioned wire) or a tube.

87. The system of claim 86, wherein the one or more electrodes form a mesh (e.g., a wire mesh) (e.g., a ID or 2D mesh).

88. The system of any one of claims 84-87, comprising one or more electrically insulating members (e.g., each comprising one or more sheds), wherein the one or more electrodes are attached to a (e.g., the) frame by the one or more electrically insulating members.

89. The system of claim 88, wherein each of the one or more electrodes is attached to the frame by a unique set of one or more of the one or more electrically insulating members.

90. The system of claim 88 or 89, wherein the one or more electrodes are electrically insulated from the frame.

91. The system of any one of claims 66-90, wherein the collectors are planar.

92. The system of any one of claims 66-91, wherein all of the collectors have a substantially identical size.

51

93. The system of any one of claims 66-92, wherein each of the collectors has a length along the central axis and a width extending along one of the one or more radial directions with which the collector is aligned and the length is larger than the width (e.g., at least 1.5x or at least 2x as large as the width).

94. The system of any one of claims 66-93, wherein each of the collectors is a panel (e.g., a planar panel).

95. The system of any one of claims 66-94, wherein each of the collectors comprises a mesh (e.g., a wire mesh).

96. The system of claim 95, wherein each of the collectors comprises a rigid frame that holds the mesh under tension [e.g., by one or more tensioning cables (e.g., running through the mesh)].

97. The system of any one of claims 66-96, wherein the collectors are disposed in a duct (e.g., and span the duct) such that the central axis is aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream).

98. The system of any one of claims 66-96, wherein the collectors are disposed after and over a gas outlet (e.g., of a cooling tower or of a duct) such that the central axis is aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream).

99. The system of claim 98, wherein the collectors span the gas outlet.

100. The system of claim 98 or claim 99, wherein the collectors are aligned with a primary direction of flow of the gas stream (e.g., an axial component of velocity of the gas stream).

101. The system of any one of claims 98-100, wherein the collectors are disposed substantially perpendicular to a swirl component of velocity of the gas stream (e.g., an axial component of velocity of the gas stream).

52

102. The system of any one of claims 66-101, wherein the collectors are each disposed substantially parallel to a plane on which the central axis lies.

103. The system of any one of claims 66-102, wherein the collectors are positioned and oriented such that a swirl component of velocity of the gas stream results in the fluid being collected from the gas stream on the collectors.

104. The system of any one of claims 66-103, wherein the collectors each have a Stokes number (St) of at least 0.05 (e.g., at least 0.1 or at least 0.2), wherein St =

with Rd is an

effective radius (e.g., droplet radius) of the fluid in the gas stream (e.g., an average droplet radius), Rc is a characteristic feature size (e.g., an average wire radius in a mesh collector or average pore separation in a non-mesh porous collector), pi is a density of the fluid in the gas stream, U is speed of flow of the gas stream, and Tj_g is dynamic viscosity of the gas stream.

105. The system of any one of claims 66-104, wherein the system is operable to collect at least 10% (e.g., at least 20%, at least 40%, or at least 60%) of initial fluid in the gas stream.

106. The system of any one of claims 66-105, wherein the fluid is liquid, vapor, droplets, drift or mist (e.g., of water) dispersed in the gas stream.

107. The method of any one of claims 1-35, wherein the one or more collectors are comprised in the system of any one of claims 36-106.

53