US20200109862A1

US20200109862A1 - Fluid heat exchanger

Info

Publication number: US20200109862A1
Application number: US16/574,805
Authority: US
Inventors: Lance E. Helfers
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-10-05
Filing date: 2019-09-18
Publication date: 2020-04-09

Abstract

A method, apparatus and system for fluid heat recovery, more commonly known as a heat exchanger, transfers heat ordinarily lost down a drain to preheat incoming fluid, so that heating systems use less energy to heat incoming fluid. The fluid heat recovery apparatus includes a helical fluid outflow pipe with discharge fluid traveling within it, and a fluid inflow tube embedded within helical channel depressions and between the helical ridge fins of the fluid outflow pipe that contacts the fluid inflow tube outer walls to the surrounding fluid outflow pipe outer wall helical channel depressions and helical ridge fins, and connects to fluid supply lines, thereby transferring heat to incoming fluid that flows in a counter current, then parallel, then counter current direction with respect to the helical fluid outflow pipe flow.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to, and the benefit of, co-pending U.S. Provisional Application 62/742,010, filed Oct. 5, 2018, for all subject matter common to both applications. The disclosure of said provisional application is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a system, method and apparatus for heat recovery from drain fluids. In particular, the present invention relates to a fluid heat exchanger suitable for transferring heat from an outgoing, discharge fluid flow to an incoming, supply fluid flow using physical contact between pipes, tubes and fluid conduits.

BACKGROUND

Generally, a fluid heat recovery apparatus, more commonly known in the industry as a heat exchanger, is a device that transfers heat between one or more mediums. The mediums transfer heat from one enclosed area to another enclosed area. Liquid heat transfer is the most common medium used in heat exchangers, with gas and air mediums also used within different applications. Fluids (liquids, gases and air) can be separated by an enclosed area or in direct contact in the heat exchanger. Fluids in this application are defined in accordance with conventional meanings as substances such as liquids or gases that are capable of flowing and that can change shape at a steady rate when acted upon by a force applied to induce a shape change. Fluid, liquid, gas, water and oil can be used interchangeably under the definition of fluid for this patent application. This patent addresses the use of at least two enclosed mediums to transfer heat from a warm or hot pipe to a cold tube.
Heat exchangers are used in any application with a wide temperature difference between 2 mediums. They are commonly used to save heating costs and limit the amount of material or energy required to move the hot or cold heat away from an area of a process. Heat exchangers have three main flow classifications. Parallel-flow is when two mediums enter the heat exchanger at the same end and travel parallel to one another and flow in the same direction. Counter-flow is when two mediums enter the heat exchanger at opposite ends and flow in different directions. Cross-flow is when two mediums travel perpendicular to one another through the heat exchanger. Counter-flow heat exchangers are the most widely used flow in heat exchangers. This patent uses a combination of counter and parallel flow. The main types of heat exchangers are shell and tube, plate, fin, spiral and combinations of said types. A shell and tube heat exchanger contains a shell or large pressure vessel with a bundle of tubes inside it. One fluid flows through the shell surrounding the tubes and another fluid flows through the tubes to transfer heat between the two fluids. A plate heat exchanger contains metal plates that have a larger surface area to spread the fluids over a wider area for faster heat transfer between the two fluids. A fin heat exchanger uses multiple layers of corrugated material to transfer heat between fluids. A spiral heat exchanger is a coiled or helical tube design that is parallel to each other with two fluids flowing in a counter current flow. A helix or helical can be defined as a spiral, coil, corkscrew, curl, twist and a curve in a three-dimensional space.
However, these types of heat exchangers each experience certain shortcomings and inefficiencies based on their type. Most conventional commercial heat exchangers used for fluid heat recovery of discharge fluids only employ a single type of heat exchanger design, thereby limiting their efficiency and effectiveness, allowing significant quantities of unrecovered heat to be discharged. Additionally, conventional approaches experience shortcomings related to expedient use of industry standard pipe materials with standard configurations and dimensions as well as minimal consideration of turbulence developed in the drain pipes of discharge systems and the length of time available to transfer heat/energy as discharge fluid passes through systems with conventional pipe configurations. This results in allowing fluid to fall down a pipe and film builds up on the walls that can insulate different media and limit heat/energy transfer and incoming cold fluid wrapped around a warm pipe lacks sufficient length to allow enough contact time for the most efficient heat/energy transfer.

SUMMARY

There is a need for an improved fluid heat recovery method, system and apparatus that leverages advantageous characteristics of all said types of heat exchangers in its design to improve efficiency and effectiveness in recovering heat from discharged fluids. The present invention is directed toward further solutions to address this need, in addition to having other desirable characteristics. Specifically this application addresses this need with a compact heat exchanger to transfer energy/heat from one fluid to another more efficiently by implementing different principles related to thermal conductivity, and more generally thermodynamics and fluid dynamics. The present invention uses the warm and/or hot fluid normally sent out inside the drain line and/or pipe in buildings to pre heat cold incoming fluid lines and/or tubes. The inventive device can be placed on a waste water and/or grey water drain line or tube and any warm or hot fluid drain, pipe, line or conduit to preheat incoming cold water or fluid. The inventive device is designed to recover a majority of the heat out of a warm or hot water or fluid drain, line, pipe and transfer the heat to incoming cold water or fluid. The design is simple with only principal two components and no electronic or mechanical components required, which reduces the likelihood of mechanical failure or the need for repair. Additionally, the turbulence in the fluid outflow pipe creates enough movement to keep the fluid outflow pipe clean and transfer energy more efficiently. The preheated tube is dimensioned, sized, shaped, and configured in a way to have a majority of outer walls of the tube surrounding the fluid outflow pipe over a longer flow distance to maximize the time allotted for heat transfer to occur.
The preheated fluid coming out of the inventive heat exchanger's tube is supplied into a tank or tankless water or fluid heater and/or warm water faucet, shower, laundry, tub, sink hose receptacle. The water or fluid heater using the inventive heat exchanger uses less energy to heat fluid or water. Less energy used to heat water or fluid results in more money saved related to the heating of water in a residential, industrial, or commercial system.
In accordance with example embodiments of the present invention, a fluid heat exchanger comprises a fluid outflow pipe possessing an inner wall and an outer wall of a first heat conducting material and disposed along a central axis between a first open end with a radius centered along the central axis and a second open end with a radius centered along the central axis, creating an inner volume forming a fluid conduit, wherein the fluid outflow pipe is in fluid communication with a fluid discharge line. The inner wall and the outer wall of the fluid outflow pipe include contoured surfaces comprising one or more helical channel depressions and one or more helical ridge fins that are interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume to create turbulence in fluid in the fluid discharge line. A fluid inflow tube comprises an inner wall and an outer wall of a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, creating an internal volume forming a supply fluid conduit, wherein the fluid inflow tube is in fluid communication with a fluid supply line, and the fluid inflow tube is configured in a shape dimensioned to fit within the one or more helical channel depressions such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe, and contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe induces heat transfer from the fluid outflow pipe and fluid traveling within the fluid outflow pipe to the fluid inflow tube and fluid traveling within the fluid inflow tube.
In accordance with aspects of the present invention, the first conductive material may be comprised of one of copper, stainless steel, and alloys and combinations thereof, and the second conductive material also may be comprised of copper, stainless steel, and alloys and combinations thereof. The shape of the fluid inflow tube may include a tube outer diameter, a pitch, a chirality and a constant radius all dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe. The shape of the fluid inflow tube may be a helix shape such that the helix shape and the one or more helical channel depressions form congruent helices that match and can be mated together.
In accordance with aspects of the present invention, the fluid heat exchanger the one or more helical channel depressions and helical ridge fins may be concentric along the central axis proceeding lengthwise through the fluid outflow pipe. The outer wall of the fluid outflow pipe and the fluid inflow tube may be attached to each other by brazing, welding, soldering, and combinations thereof, or be other pipe connecting practices known in the art such as various pipe connectors. The fluid inflow tube may be shaped to have a majority of a surface area of the outer wall of the fluid inflow contacting and surrounded by the bottom, the first side, and the second side of the one or more helical channel depressions of the outer wall the fluid outflow pipe and the helical ridge fins of the outer wall of the fluid outflow pipe, creating an increased surface area for transmitting heat energy to promote heat transfer. In this way, instead of each turn of the inflow tube contacting the outer surface of the outflow pipe along only a tangent of the tube cross section, there are at least three such contact points corresponding to the bottom and sides of the helical channel depressions, wherein the sides are formed by the intervening helical ridge fins, and the shape of the channels may be further refined to allow the inflow tube to contact the helical channel depression along the entire surface area that can embed into the depth each of the of the helical channel depressions, such that a majority of the perimeter of the cross section of the inflow tube or pipe and the overall majority of the surface area is in mated contact with the outflow pipe or tube and not just tangentially contacting the outflow pipe or tube. The shape of the fluid inflow tube may be a helix shape that comprises coils of the helix shape bending around the fluid outflow pipe having a pitch that extends a length of the tube along the main axis from the first open end of the fluid outflow pipe down along the fluid outflow pipe to the second end of the fluid outflow pipe, then reverses direction and extends back up to the first end of the fluid outflow pipe, then reverses direction again extending back down to the second end of the fluid outflow pipe before terminating at the second end of the fluid inflow tube, such that fluid traveling in the fluid inflow tube first travels in a counter current flow with respect to a direction of fluid flow of the fluid outflow pipe, then second travels in a same direction of fluid flow of the fluid outflow pipe, and third travels in a counter current flow to a direction of fluid flow of the fluid outflow pipe before exiting the fluid inflow tube through the second open end. The first open end the fluid heat exchanger may be connected to, and in fluid communication with, a fluid discharge line, that empties into, or is otherwise connected to the first end of the fluid heat exchanger, which may be also the first end of the fluid outflow pipe, using any known method of connecting pipes, including but not limited to pipe fittings or threading and connections such as brazing, welding or soldering. The first open end is connected to, and in fluid communication with, a fluid discharge line that transports fluids that may comprise one or more of the group consisting of grey water, waste water, drain water, water exiting plumbing fixtures with elevated temperature, and combinations thereof. The second open end of the fluid heat exchanger, or outflow pipe therein, may be connected to, and in fluid communication with, a fluid discharge line comprising at least one of the group consisting of a main discharge line, a drain waste vent line, a wastewater line, a greywater line, a main drain pipe, a waste stack pipe, a soil stack pipe, and a building drain. In this way, the fluid outflow pipe may replace a section of a fluid discharge line flowing out from the premises, supplying the same type of fluid discharge conduit as was available while also recapturing heat from fluids leaving through the discharge line and transferring that heat to incoming fluids.
In accordance with aspects of the present invention, the third open end of the fluid heat exchanger, which may also be an open end of a fluid inflow tube, may be connected to, and in fluid communication with, a fluid supply line. The fourth open end of the fluid heat exchanger, which may be the other open end of a fluid inflow tube, is connected to, and in fluid communication with, one or more of the group consisting of a water heater, a connection to a water heater, a supply line to a water heater, a water heater intake, a heating element intake, a holding tank, a warm water supply line, a supply line receiving heat energy from a heating element, a pipe receiving heat from an external source, a tube receiving heat from an external source, and combinations thereof, such that the fluid heat exchanger, and more specifically the fluid inflow tube, may replace a section of a fluid supply line flowing into the premises, supplying the same type of fluid supply conduit as was available while also recapturing heat from fluids leaving through the discharge line and transferring that heat to incoming fluids flowing through the fluid supply line.
In accordance with example embodiments of the present invention, a fluid heat recovery system comprises a fluid discharge line in fluid communication with a fluid outflow pipe, a fluid supply line in fluid communication with a fluid inflow tube, and a helical heat exchanger. The heat exchanger includes a fluid outflow pipe with an inner wall and an outer wall formed from a first heat conducting material and disposed along a central axis between a first open end with a radius centered along the central axis and a second open end with a radius centered along the central axis, creating an inner volume disposed along the central axis and forming a fluid conduit, wherein the inner wall and the outer wall of the fluid outflow pipe are twisted, thereby forming a helical contoured surface of the outer wall comprising one or more helical channel depressions and one or more helical ridge fins that are concentric along the central axis with the helical channel depressions and interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume to create a fluid conduit imparting fluid traveling within the fluid discharge line with turbulence inducing vortices. A fluid inflow tube includes an inner wall and an outer wall formed from a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, where the main access follows the same helical pitch, creating an internal volume disposed along the main axis and forming a supply fluid conduit, wherein the fluid inflow tube is configured in a shape with a tube outer diameter, a helical pitch, a chirality and a constant radius of the helix shape dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe. Thus an inflow of fluid traveling within the fluid supply line passes through the fluid inflow tube and is preheated by heat transfer from an outflow of fluid traveling within the fluid outflow pipe, where contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe enables heat transfer from the fluid outflow pipe and the outflow of fluid traveling within the fluid outflow pipe to the fluid inflow tube and the inflow of fluid traveling within the fluid inflow tube.
In accordance with aspects of the present invention, the shape of the fluid inflow tube may be a helix shape or similar shape that comprises coils of the helix shape bending around the fluid outflow pipe having a pitch that extends a length of the tube along the main axis from the first open end of the fluid outflow pipe down along the fluid outflow pipe to the second end of the fluid outflow pipe, then reverses direction and extends back up to the first end of the fluid outflow pipe, then reverses direction again extending back down to the second end of the fluid outflow pipe before terminating at the second end of the fluid inflow tube, such that fluid traveling in the fluid inflow tube first travels in a counter current flow with respect to a direction of fluid flow of the fluid outflow pipe, then second travels in a same direction of fluid flow of the fluid outflow pipe, and third travels in a counter current flow to a direction of fluid flow of the fluid outflow pipe before exiting the fluid inflow tube through the second open end.
In accordance with example embodiments of the present invention, a fluid heat recovery method receives, at a first open end of a fluid outflow pipe from a fluid discharge line in fluid communication with the first open end, a fluid outflow and induces turbulence with vortices created in fluid traveling within the fluid discharge line by directing the flow of fluid outflow across an inner wall of the fluid outflow pipe forming a helical contoured surface, wherein the inner wall and an outer wall formed from a first heat conducting material comprise one or more helical channel depressions and one or more helical ridge fins that are interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume prior to a second open end of the fluid outflow pipe to create a fluid conduit that alters the fluid outflow to induce and improve heat transfer, thereby transferring heat energy from the fluid outflow to the inner walls, then the outer walls, of the fluid outflow pipe. The method receives, at a third open end of a fluid inflow tube from a fluid supply line in fluid communication with the third open end, a fluid inflow, wherein the fluid inflow tube comprises an inner wall and an outer wall formed from a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, creating an internal volume disposed along the main axis and forming a supply fluid conduit, and conducts heat energy from the outer walls of the fluid outflow pipe to the outer walls of the fluid inflow tube, wherein the fluid inflow tube is bent in a helix shape with a tube outer diameter, a helical pitch, a chirality and a constant radius of the helix shape dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe, and contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe enables heat transfer from the fluid outflow pipe to the fluid inflow tube. The method discharges, using the second open end of the fluid outflow pipe, the fluid outflow while transferring heat energy from the fluid inflow tube to the fluid inflow as the fluid inflow travels a length of the fluid inflow tube through coils of the helix shape and supplies preheated fluid inflow out of a fourth open end of the fluid inflow tube in fluid communication with a heating element and heating the fluid inflow by conventional processes of the heating element, and supplies fluid for use over the fluid supply line and using fluid from the fluid supply line and draining fluid into discharge line, while transferring heat energy between these two fluid lines without the respective fluid flows ever coming into any actual fluid contact, thereby preserving the integrity of each respect flow.
In accordance with example embodiments of the present invention, a method for manufacturing and using a helical heat exchanger secures a fluid outflow pipe comprising an inner wall and an outer wall formed from a first heat conducting material and disposed along a central axis between a first open end with a radius centered along the central axis and a second open end with a radius centered along the central axis, creating an inner volume disposed along the central axis and forming a fluid conduit. The method for manufacturing twists the inner wall and the outer wall of the fluid outflow pipe by applying torque in opposite directions of rotation at opposite ends of the fluid outflow pipe, thereby forming a helical contoured surface of the outer wall comprising one or more helical channel depressions and one or more helical ridge fins that are concentric along the central axis with the helical channel depressions and interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume to create a fluid conduit with turbulence inducing vortices for fluid traveling within the fluid discharge line. The method secures a fluid inflow tube comprising an inner wall and an outer wall formed from a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, creating an internal volume disposed along the main axis and forming a supply fluid conduit. The method further bends the fluid inflow tube in a helix shape or similar shape with a tube outer diameter, a helical pitch, a chirality and a constant radius of the helix shape dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe, wherein contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe enables heat transfer from the fluid outflow pipe and fluid traveling within the fluid outflow pipe to the fluid inflow tube and fluid traveling within the fluid inflow tube. The method mates the fluid inflow tube to the fluid outflow pipe, attaching the outer wall of the fluid outflow pipe and the fluid inflow tube to each other by any known method of connecting pipes, including but not limited to pipe fittings or threading and connections such as brazing, welding or soldering.

BRIEF DESCRIPTION OF THE FIGURES

These and other characteristics of the present invention will be more fully understood by reference to the following detailed description in conjunction with the attached drawings, in which:

FIG. 1 depicts a diagrammatic illustrative example of a fluid heat exchanger;

FIG. 2 depicts a diagrammatic illustrative example of a fluid outflow pipe component of the fluid heat exchanger;

FIG. 3 depicts a diagrammatic illustrative example of a fluid inflow tube component of the fluid heat exchanger;

FIG. 4 depicts a diagrammatic illustrative example of a representative diagonal cutaway view of the fluid heat exchanger;

FIG. 5 depicts a diagrammatic illustrative example of a representative longitudinal cutaway view of the fluid heat exchanger;

FIG. 6 depicts a diagrammatic illustrative example of a representative isometric cutaway view of the fluid heat exchanger;

FIG. 7 depicts a diagrammatic illustrative example of a representative cross-sectional cutaway view of the fluid heat exchanger;

FIG. 8 depicts a diagrammatic illustrative example of configurations of a system for implementation of the present invention;

FIG. 9 depicts a diagrammatic illustrative example of a system for implementation of the present invention within a building and plumbing system; and

FIG. 10 is an illustrative flowchart depicting an example fluid heat recovery method.

DETAILED DESCRIPTION

An illustrative embodiment of the present invention relates to an improved fluid heat recovery method, system, and apparatus that use a fluid heat exchanger that combines aspects of multiple different types of heat exchangers in its design to improve efficiency and effectiveness in recovering heat from discharged fluids and transferring that heat energy to desired fluid locations. The present invention is generally directed to a compact fluid heat exchanger that transfers energy/heat from one fluid to another more efficiently by implementing different principles related to thermal conductivity, and more generally thermodynamics and fluid dynamics. This fluid heat exchanger uses the warm and/or hot fluid normally discharged inside a drain line and/or pipe to pre-heat cooler incoming fluid supply lines and fluid inflow tubes. Heat energy is transferred by convection from the fluid discharged in the fluid discharge line as it flows through the fluid outflow pipe, wherein the moving fluid contacts the inner wall of the fluid outflow pipe with a surface of a different temperature and the motion of molecules establishes a heat transfer per unit surface through convection following Newton's Law of Cooling. Then in thermal conduction heat spontaneously flows from a hotter to a colder body and so heat energy is transferred from the warmer fluid outflow pipe to the cooler fluid inflow tube over the areas of physical contact between the two components. Heat energy is then transferred by convection again from the inner wall of the fluid inflow tube to fluid from the supply line flowing through the fluid inflow tube and contacting the surface area of the inner wall of the fluid inflow tube. This fluid heat exchanger can be placed on a waste water and/or grey water drain line or tube and any warm or hot fluid drain, pipe, line or conduit to preheat incoming cold water or fluid.
FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, wherein like parts are designated by like reference numerals throughout, illustrate an example embodiment or embodiments of a method, apparatus, and system for fluid heat recovery, comprising a fluid heat exchanger, according to the present invention. Although the present invention will be described with reference to the example embodiment or embodiments illustrated in the figures, it should be understood that many alternative forms can embody the present invention. One of skill in the art will additionally appreciate different ways to alter the parameters of the embodiment(s) disclosed, such as the size, shape, or type of elements or materials, in a manner still in keeping with the spirit and scope of the present invention.
FIG. 1 depicts an illustrative example embodiment of a fluid heat recovery system 100 including a fluid heat exchanger 102 for implementing the present invention. The fluid heat exchanger 102 has a helix or twist in the middle of the fluid outflow pipe 104 with enough room in the helical ridge fins 122 formed by the helix or twist in the fluid outflow pipe 104 wall to embed a fluid inflow tube 124 within a bottom 140, first side 142, and second side 144 of helical channel depressions 120 disposed between the helical ridge fins 122. A majority of the fluid inflow tube 124 is surrounded by the helical channel depressions 120 and the helical ridge fins 122 of the outer walls 108 of the fluid outflow pipe 104. The fluid inflow tube 124 is intertwined and wrapped around the fluid outflow pipe 104 to completely surround the fluid outflow pipe 104, except for the twisted fins protruding out. The helical ridge fins 122 and fluid inflow tube 124 can be covered further with an insulating shield or tube/pipe. The fluid inflow tube 124 is sized, dimensioned, and configured to make maximum surface area contact with the helical channel depressions 120 and the helical ridge fins 122 to maximize conductive heat exchange between the two structures.
FIG. 2 depicts the fluid outflow pipe 104 having two ends 110, 112 that are round, smooth and cylindrical; which is the same as a conventional straight pipe and a helix or twist in the middle with helical ridge fins 122. The helix or twist structure likewise exists on an inner wall 106 of the fluid outflow pipe 104 and creates turbulence within fluid flowing through the fluid outflow pipe 104, which in turn increases the heat transfer efficiency. The outer helical ridge fins 122 in the middle of the fluid outflow pipe 104 also increase the heat transfer efficiency to the outer surface area of the fluid outflow pipe 104 and surround a majority of the fluid inflow tube 124. Greater heat transfer efficiency in the fluid outflow pipe 104 equals less material used for the fluid inflow tube 124 design.
FIG. 3 depicts the fluid inflow tube 124 configured in a curved U-shape three-dimensional design to fit in the helical ridge fins 122 of the fluid outflow pipe 104 with the incoming and outgoing fluid flowing in opposite directions at the end of its flow. The fluid inflow tube 124 surrounds the middle of the fluid outflow pipe 104 except for the helical ridge fins 122 sticking out. The length of the fluid inflow tube 124 is substantially longer than the fluid outflow pipe 104 to encourage additional heat transfer, where the walls of the fluid outflow pipe 104 contain heat on all sides and the surface area of the outside of the fluid inflow tube 124 is less that the surface area of the outside of the fluid outflow pipe 104 and does not contact the fluid outflow pipe 104 on all sides, so additional length with a greater number of coils brings the ratio of surface areas closer to one to one, thereby providing more overall surface area over which heat transfer may efficiently occur.
The fluid heat exchanger 102 may be manufactured from copper, stainless steel, or alloys, and combinations thereof in consumer, residential, commercial, and industrial applications. As can be understood from the cutaway views depicted in FIGS. 4, 5, 6 and 7, a twisted pipe creates turbulence, which transfers energy/heat more efficiently. A majority of the tube is surrounded by the fins and outer wall of the fluid outflow pipe 104, which increases the surface area to aid in energy/heat transfer. Buildings have different size pipes and tubes according to applicable building codes, regulations and construction practices, and the fluid heat exchanger may be adapted in size to accommodate all of these ranges. For example, a three inch drain pipe and three-quarters of an inch water supply line are common in many new homes, such that the heat exchanger may then be adapted to comprise a fluid outflow pipe 104 that matches a three inch drain pipe and also comprises a fluid inflow tube 124 that matches a three-quarters of an inch water supply line, but every county, state, jurisdiction or area can be different and the fluid heat exchanger may be sized and dimensioned accordingly to accommodate these features. The heat exchanger is so readily adaptable because the twists on the interior walls of the pipe should increase heat transfer by as much as 40% by way of the turbulence created by the twists, additionally allowing the fins to surround and mate with three-quarters of the outer walls of inflow tubing to increase heat transfer. The size of the pipes of a system also determine how many turns tubing makes around a fluid outflow pipe 104, but in a three inch pipe example the fluid inflow tube 124 may typically make five turns in a first direction and then an equal number of turns in an opposite direction, thereby providing the opportunity for incoming fluid flow to traverse turns over the length of the fluid outflow pipe 104 two times before proceeding. The increase in pipe to pipe contact couples with the increased turbulence and increase in contacted surface area per unit length (as opposed to only a single line of tangential contact to a discharge pipe for each turn of tube) is estimated to vastly increase the ability of the exchanger to transfer heat between fluid flows without the respective fluid flows coming into fluid contact. The heat transfer components may be constructed from a variety of materials possesses appropriate characteristics, however building codes or other regulations may limit the materials used, where copper is often the most efficient heat transfer material that is widely used. In addition to flexibility with respect to dimensioning and materials, the heat exchanger can also be installed using many different types of fittings, connections, junctions, couplings, adapters, threading patterns or other plumbing components known in the art, where plumbers may implement different connections and easily be able to use what they prefer to connect plumbing lines with the heat exchanger 102 and the system. Construction of two primary components of the heat exchanger and system, the fluid outflow pipe 104 and fluid inflow tube 124 can be accomplished by a variety of different methods, for example, by tack welding the fluid inflow tube 124 in place on the fluid outflow pipe 104 to align and mate the surfaces such that the fluid inflow tube 124 resides within the helical channel depressions 120, which may correspond to a weld point for each turn or a weld point in five to seven locations throughout the length of the tube and pipe. Additionally, a blanket or covering possessing insulating, reflective, or both properties may be used to wrap around or otherwise surround the pipes and tubes of the heat exchanger 102, thereby increasing the retention of heat for heat transfer in the system as heated fluid passes therethrough.
FIG. 8 depicts an installed system 200 wherein in operation, the fluid heat exchanger 102 uses two parts to achieve energy efficiency in a way that is simple and easy to install. The waste water or grey water pipe of a fluid discharge line 118 has warm or hot fluid flowing out and passes through fluid heat exchanger 102 as depicted in FIG. 8 and FIG. 9; specifically the fluid outflow pipe 104. The fluid discharge line 118 can take many forms, including but not limited to being a main discharge line, a main drain pipe, a waste stack pipe, a soil stack pipe, and/or a building drain. Each helix, bend, twist, or coil on the inner walls 106 of the fluid outflow pipe 104 creates turbulence. The turbulence, pipe material used and helical ridge fins 122 assist in the transfer of heat from the fluid going out of the fluid outflow pipe 104 to the fluid flowing in the opposite or counter current direction in the fluid inflow tube 124.
The relatively cooler water flowing into a water heater 146 is preheated before it enters or cycles through the water heater. It is preheated by transferring a majority of heat from the liquid flowing down the fluid outflow pipe 104 to the outer walls of the fluid outflow pipe 104 and that heat is transferred to the outer walls of the fluid inflow tube 124 and into the water flowing through the fluid inflow tube 124. This preheated water flows in a counter current then parallel and back to counter current flow direction in the fluid heat exchanger 102. The water is preheated before it enters a hot water heater, so the water heater has to work less and use less energy.
The shape of the fluid inflow tube 124 may be formed using techniques known in the art, including the use of tube benders familiar to those of skill in the art. The following manufacturing process is considered to be consistent with an example process that results in the “twisted” tube. The fluid inflow tube 124 is given a diameter and pitch to align and mate with the helical channel depressions 120 of the fluid outflow pipe 104. The helical channel depressions 120 and helical ridge fins 122 may be formed in the fluid outflow pipe 104 by cutting the pipe to length using means known in the art and securing the pipe within a draw bench machine or similar machine, for example a hydraulic draw bench machine used for cold drawing of pipes and tubes, then performing twisting of the pipe body inner wall and outer wall by applying torque while the fluid outflow pipe 104 is held in place with a clamp or other holding means, wherein a rotating die or set of dies applies at least a torsion force and a restrictive force as the fluid outflow pipe 104 is drawn through the die or set of dies. The rotation of the die or dies may be controlled by a computer or other means to create the desired helical twist angle or pitch. In another embodiment, after the fluid outflow pipe 104 is cut to length a machine may be used to clamp, secure or hold in place the two pipe ends 110, 112 and twist the fluid outflow pipe 104 by applying torque in a single direction of rotation at one pipe end 110, 112 or in opposite directions of rotation at opposite ends 110, 112 of the fluid outflow pipe 104 until the desired helical twist angle, spiral pitch or twist rate is achieved. The tube and pipe are manufactured to specifications and tolerances that allow for maximization of contacts between the outer surfaces of the fluid inflow tube 124 and the outer surfaces of the fluid outflow pipe 104, specifically the helical channel depressions 120 and helical ridge fins 122.
FIG. 10 depicts a for fluid heat recovery method 700. At step 702, the fluid heat exchanger receives, at a first open end 110 of a fluid outflow pipe 104 from a fluid discharge line 118 in fluid communication with the first open end 110, a fluid outflow.
At step 704, the fluid outflow pipe 104 induces turbulence with vortices created in fluid traveling within the fluid discharge line 118 by directing the flow of fluid outflow across an inner wall 106 of the fluid outflow pipe 104 forming a helical contoured surface. The inner wall 106 and an outer wall 108 formed from a first heat conducting material comprise one or more helical channel depressions 120 and one or more helical ridge fins 122 that intervene between the one or more helical channel depressions 120 along a length of the fluid outflow pipe 104 equal to the length of the central axis 114, at a matching helical pitch, thereby configuring the inner volume 116 prior to a second open end 112 of the fluid outflow pipe 104 to create a fluid conduit that alters the fluid outflow to induce and improve heat transfer.
At step 706, as the fluid outflow travels through the inner volume 116 of the fluid outflow pipe 104, the fluid outflow transfers heat energy from the fluid outflow to the inner walls 106, then the outer walls 108, of the fluid outflow pipe 104.
At step 708, the outer walls 108 of the fluid outflow pipe conduct heat energy to the outer walls 128 of the fluid inflow tube 124, wherein the fluid inflow tube 124 is configured in a helix shape with a tube outer diameter, a helical pitch, a chirality and a constant radius of the helix shape dimensioned to fit within the one or more helical channel depressions 120 of the fluid outflow pipe 104, such that the outer wall 128 of the fluid inflow tube 124 contacts at least a bottom 140, a first side 142, and a second side 144 of each of the one or more helical channel depressions 120 of the outer wall 108 the fluid outflow pipe 104 between successive helical ridge fins 122 of the outer wall 108 of the fluid outflow pipe 104, and contact between the outer wall 128 of the fluid inflow tube 124 and the outer wall 108 of the fluid outflow pipe 104 enables heat transfer from the fluid outflow pipe 104 to the fluid inflow tube 124. At step 710, the fluid outflow pipe discharges the fluid outflow through the second opening; discharging, using the second open end of the fluid outflow pipe, the fluid outflow.
At step 714 the fluid heat exchanger 102 receives, at a third open end 130 of a fluid inflow tube 124, from a fluid supply line 138 in fluid communication with the third open end 130, a fluid inflow. The fluid inflow tube 124 comprises an inner wall 126 and an outer wall 128 formed from a second heat conducting material and disposed along a main axis 134 between a third open end 130 with a radius centered along the main axis 134 and a fourth open end 132 with a radius centered along the main axis 134, creating an internal volume 136 disposed along the main axis 134 and forming a supply fluid conduit.
At step 716, the fluid heat exchanger 102 transfers heat energy from the fluid inflow tube 124 to the fluid inflow as the fluid inflow travels a length of the fluid inflow tube through coils of the helix shape which increase the amount of time the fluid inflow is in contact with the inner walls 126 of the fluid inflow tube 124, thereby increasing the effect of heat transfer.
At step 718, the fluid inflow tube 124 uses the fourth open end 132 to supply preheated fluid inflow, to a conventional heating element, directly or by way of the fluid supply line 138, where at step 720 the fluid inflow is heated by conventional processes of a heating element in fluid communication with the fluid inflow tube 124. At step 722, the heating element and fluid supply line 138 supply the fluid inflow for use over the fluid supply lines 138, where at step 724, the fluid heat recovery system 100 connects with additional plumbing components and uses fluid from the fluid supply line 138 for different plumbing applications within various plumbing fixtures 148 before draining the fluid into a fluid discharge line 118, potentially restarting the fluid heat recovery method 700 in a continuous cycle.
To any extent utilized herein, the terms “comprises” and “comprising” are intended to be construed as being inclusive, not exclusive. As utilized herein, the terms “exemplary”, “example”, and “illustrative”, are intended to mean “serving as an example, instance, or illustration” and should not be construed as indicating, or not indicating, a preferred or advantageous configuration relative to other configurations. As utilized herein, the terms “about” and “approximately” are intended to cover variations that may existing in the upper and lower limits of the ranges of subjective or objective values, such as variations in properties, parameters, sizes, and dimensions. In one non-limiting example, the terms “about” and “approximately” mean at, or plus 10 percent or less, or minus 10 percent or less. In one non-limiting example, the terms “about” and “approximately” mean sufficiently close to be deemed by one of skill in the art in the relevant field to be included. As utilized herein, the term “substantially” refers to the complete or nearly complete extend or degree of an action, characteristic, property, state, structure, item, or result, as would be appreciated by one of skill in the art. For example, an object that is “substantially” circular would mean that the object is either completely a circle to mathematically determinable limits, or nearly a circle as would be recognized or understood by one of skill in the art. The exact allowable degree of deviation from absolute completeness may in some instances depend on the specific context. However, in general, the nearness of completion will be so as to have the same overall result as if absolute and total completion were achieved or obtained. The use of “substantially” is equally applicable when utilized in a negative connotation to refer to the complete or near complete lack of an action, characteristic, property, state, structure, item, or result, as would be appreciated by one of skill in the art.
Numerous modifications and alternative embodiments of the present invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode for carrying out the present invention. Details of the structure may vary substantially without departing from the spirit of the present invention, and exclusive use of all modifications that come within the scope of the appended claims is reserved. Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. It is intended that the present invention be limited only to the extent required by the appended claims and the applicable rules of law.
It is also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

What is claimed is:

1. A fluid heat exchanger, comprising:

a fluid outflow pipe comprising an inner wall and an outer wall of a first heat conducting material and disposed along a central axis between a first open end with a radius centered along the central axis and a second open end with a radius centered along the central axis, creating an inner volume forming a fluid conduit, wherein the fluid outflow pipe is in fluid communication with a fluid discharge line;

wherein the inner wall and the outer wall of the fluid outflow pipe comprise contoured surfaces comprising one or more helical channel depressions and one or more helical ridge fins that are interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume to create turbulence in fluid in the fluid discharge line;

a fluid inflow tube comprising an inner wall and an outer wall of a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, creating an internal volume forming a supply fluid conduit, wherein the fluid inflow tube is in fluid communication with a fluid supply line; and

wherein the fluid inflow tube is configured in a shape dimensioned to fit within the one or more helical channel depressions such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe, and contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe induces heat transfer from the fluid outflow pipe and fluid traveling within the fluid outflow pipe to the fluid inflow tube and fluid traveling within the fluid inflow tube.

2. The fluid heat exchanger of claim 1, wherein the first conductive material is comprised of one of the group consisting of copper, stainless steel, and alloys and combinations thereof.

3. The fluid heat exchanger of claim 1, wherein the second conductive material is comprised of one of the group consisting of copper, stainless steel, and alloys and combinations thereof.

4. The fluid heat exchanger of claim 1, wherein the shape of the fluid inflow tube comprises a tube outer diameter, a pitch, a chirality and a constant radius all dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe.

5. The fluid heat exchanger of claim 4, wherein the shape of the fluid inflow tube is a helix shape such that the helix shape and the one or more helical channel depressions form congruent helices.

6. The fluid heat exchanger of claim 1, wherein the one or more helical channel depressions and the one or more helical ridge fins are concentric along the central axis.

7. The fluid heat exchanger of claim 1, wherein the outer wall of the fluid outflow pipe and the fluid inflow tube are attached to each other by at least of the group consisting of brazing, welding, soldering, and combinations thereof.

8. The fluid heat exchanger of claim 1, wherein the fluid inflow tube is shaped to have a majority of a surface area of the outer wall of the fluid inflow contacting and surrounded by the bottom, the first side, and the second side of the one or more helical channel depressions of the outer wall the fluid outflow pipe and the helical ridge fins of the outer wall of the fluid outflow pipe, creating an increased surface area for transmitting heat energy to promote heat transfer.

9. The fluid heat exchanger of claim 1, wherein the shape of the fluid inflow tube is a helix shape that comprises coils of the helix shape bending around the fluid outflow pipe having a pitch that extends a length of the tube along the main axis from the first open end of the fluid outflow pipe down along the fluid outflow pipe to the second end of the fluid outflow pipe, then reverses direction and extends back up to the first end of the fluid outflow pipe, then reverses direction again extending back down to the second end of the fluid outflow pipe before terminating at the second end of the fluid inflow tube, such that fluid traveling in the fluid inflow tube first travels in a counter current flow with respect to a direction of fluid flow of the fluid outflow pipe, then second travels in a same direction of fluid flow of the fluid outflow pipe, and third travels in a counter current flow to a direction of fluid flow of the fluid outflow pipe before exiting the fluid inflow tube through the second open end.

10. The fluid heat exchanger of claim 1, wherein the first open end is connected to, and in fluid communication with, a fluid discharge line.

11. The fluid heat exchanger of claim 1, wherein first open end is connected to, and in fluid communication with, a fluid discharge line that transports fluids comprising one or more of the group consisting of grey water, waste water, drain water, water exiting plumbing fixtures with elevated temperature, and combinations thereof.

12. The fluid heat exchanger of claim 1, wherein the second open end is connected to, and in fluid communication with, a fluid discharge line comprising at least one of the group consisting of a main discharge line, a drain waste vent line, a wastewater line, a greywater line, a main drain pipe, a waste stack pipe, a soil stack pipe, and a building drain.

13. The fluid heat exchanger of claim 1, wherein the third open end is connected to, and in fluid communication with, a fluid supply line.

14. The fluid heat exchanger of claim 1, wherein the fourth open end is connected to, and in fluid communication with, one or more of the group consisting of a water heater, a connection to a water heater, a supply line to a water heater, a water heater intake, a heating element intake, a holding tank, a warm water supply line, a supply line receiving heat energy from a heating element, a pipe receiving heat from an external source, a tube receiving heat from an external source, and combinations thereof.

15. A fluid heat recovery system, comprising:

a fluid discharge line in fluid communication with a fluid outflow pipe;

a fluid supply line in fluid communication with a fluid inflow tube;

a helical heat exchanger, comprising:

a fluid outflow pipe comprising an inner wall and an outer wall formed from a first heat conducting material and disposed along a central axis between a first open end with a radius centered along the central axis and a second open end with a radius centered along the central axis, creating an inner volume disposed along the central axis and forming a fluid conduit, wherein the inner wall and the outer wall of the fluid outflow pipe are twisted, thereby forming a helical contoured surface of the outer wall comprising one or more helical channel depressions and one or more helical ridge fins that are concentric along the central axis with the helical channel depressions and interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume to create a fluid conduit imparting fluid traveling within the fluid discharge line with turbulence inducing vortices;

a fluid inflow tube comprising an inner wall and an outer wall formed from a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, creating an internal volume disposed along the main axis and forming a supply fluid conduit, wherein the fluid inflow tube is configured in a shape with a tube outer diameter, a helical pitch, a chirality and a constant radius of the helix shape dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe; and

wherein an inflow of fluid traveling within the fluid supply line passes through the fluid inflow tube and is preheated by heat transfer from an outflow of fluid traveling within the fluid outflow pipe, where contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe enables heat transfer from the fluid outflow pipe and the outflow of fluid traveling within the fluid outflow pipe to the fluid inflow tube and the inflow of fluid traveling within the fluid inflow tube.

16. The fluid heat recovery system of claim 15, wherein the shape of the fluid inflow tube is a helix shape that comprises coils of the helix shape bending around the fluid outflow pipe having a pitch that extends a length of the tube along the main axis from the first open end of the fluid outflow pipe down along the fluid outflow pipe to the second end of the fluid outflow pipe, then reverses direction and extends back up to the first end of the fluid outflow pipe, then reverses direction again extending back down to the second end of the fluid outflow pipe before terminating at the second end of the fluid inflow tube, such that fluid traveling in the fluid inflow tube first travels in a counter current flow with respect to a direction of fluid flow of the fluid outflow pipe, then second travels in a same direction of fluid flow of the fluid outflow pipe, and third travels in a counter current flow to a direction of fluid flow of the fluid outflow pipe before exiting the fluid inflow tube through the second open end.

17. A fluid heat recovery method, comprising:

receiving, at a first open end of a fluid outflow pipe from a fluid discharge line in fluid communication with the first open end, a fluid outflow;

inducing turbulence with vortices created in fluid traveling within the fluid discharge line by directing the flow of fluid outflow across an inner wall of the fluid outflow pipe forming a helical contoured surface, wherein the inner wall and an outer wall formed from a first heat conducting material comprise one or more helical channel depressions and one or more helical ridge fins that are interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume prior to a second open end of the fluid outflow pipe to create a fluid conduit that alters the fluid outflow to induce and improve heat transfer;

transferring heat energy from the fluid outflow to the inner walls, then the outer walls, of the fluid outflow pipe;

receiving, at a third open end of a fluid inflow tube from a fluid supply line in fluid communication with the third open end, a fluid inflow, wherein the fluid inflow tube comprises an inner wall and an outer wall formed from a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, creating an internal volume disposed along the main axis and forming a supply fluid conduit;

conducting heat energy from the outer walls of the fluid outflow pipe to the outer walls of the fluid inflow tube, wherein the fluid inflow tube is bent in a helix shape with a tube outer diameter, a helical pitch, a chirality and a constant radius of the helix shape dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe, and contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe enables heat transfer from the fluid outflow pipe to the fluid inflow tube;

discharging, using the second open end of the fluid outflow pipe, the fluid outflow;

transferring heat energy from the fluid inflow tube to the fluid inflow as the fluid inflow travels a length of the fluid inflow tube through coils of the helix shape;

supplying preheated fluid inflow out of a fourth open end of the fluid inflow tube in fluid communication with a heating element and heating the fluid inflow by conventional processes of the heating element; and

supplying fluid for use over the fluid supply line and using fluid from the fluid supply line and draining fluid into discharge line.

18. A method for manufacturing and using a helical heat exchanger, comprising:

securing a fluid outflow pipe comprising an inner wall and an outer wall formed from a first heat conducting material and disposed along a central axis between a first open end with a radius centered along the central axis and a second open end with a radius centered along the central axis, creating an inner volume disposed along the central axis and forming a fluid conduit;

twisting the inner wall and the outer wall of the fluid outflow pipe by applying torque in opposite directions of rotation at opposite ends of the fluid outflow pipe, thereby forming a helical contoured surface of the outer wall comprising one or more helical channel depressions and one or more helical ridge fins that are concentric along the central axis with the helical channel depressions and interspersed between the one or more helical channel depressions along a length of the fluid outflow pipe at a matching helical pitch, thereby configuring the inner volume to create a fluid conduit with turbulence inducing vortices for fluid traveling within the fluid discharge line;

securing a fluid inflow tube comprising an inner wall and an outer wall formed from a second heat conducting material and disposed along a main axis between a third open end with a radius centered along the main axis and a fourth open end with a radius centered along the main axis, creating an internal volume disposed along the main axis and forming a supply fluid conduit;

bending the fluid inflow tube in a helix shape with a tube outer diameter, a helical pitch, a chirality and a constant radius of the helix shape dimensioned to fit within the one or more helical channel depressions of the fluid outflow pipe such that the outer wall of the fluid inflow tube contacts at least a bottom, a first side, and a second side of each of the one or more helical channel depressions of the outer wall the fluid outflow pipe between successive helical ridge fins of the outer wall of the fluid outflow pipe, wherein contact between the outer wall of the fluid inflow tube and the outer wall of the fluid outflow pipe enables heat transfer from the fluid outflow pipe and fluid traveling within the fluid outflow pipe to the fluid inflow tube and fluid traveling within the fluid inflow tube;

mating the fluid inflow tube to the fluid outflow pipe; and

attaching the outer wall of the fluid outflow pipe and the fluid inflow tube to each other by brazing.