US20160061532A1

US20160061532A1 - Evaporator and condenser section structure for thermosiphon

Info

Publication number: US20160061532A1
Application number: US14/843,210
Authority: US
Inventors: Morten Søegaard Espersen; Maria Luisa Angrisani; Dennis N. Jensen; Sukhvinder S. Kang
Original assignee: Aavid Thermalloy LLC
Current assignee: Aavid Thermalloy LLC
Priority date: 2014-09-02
Filing date: 2015-09-02
Publication date: 2016-03-03
Also published as: CN105579792A; WO2016036867A8; WO2016036867A1

Abstract

A thermosiphon device includes a closed loop evaporator section having one or more evaporation channels that are fed by a liquid return path, and a condenser section with one or more condensing channels. The condenser section may include a vapor supply path that is adjacent one or more condensing channels, e.g., located between two sets of condensing channels. Evaporator and/or condenser sections may be made from a single, flat bent tube, which may be bent about an axis parallel to the plane of the flat tube to form a turnaround and/or twisted about an axis along a length of the tube at the tube ends. A single tube may form both evaporator and condenser sections of a thermosiphon device, and an axially extending wall inside the tube in the evaporator section may separate an evaporator section from a liquid return section.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 62/044,604, filed Sep. 2, 2014, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1) Field of Invention
This invention relates generally to thermosiphon devices and other heat transfer devices that employ a two-phase fluid for cooling.

- 2) Description of Related Art

Thermosiphon devices are widely used for cooling systems, such as integrated circuits and other computer circuitry. For example, U.S. Patent Publication 2013/0104592 discloses a thermosiphon cooler used to cool electronic components located in a cabinet or other enclosure.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a thermosiphon device may have a closed loop evaporator section combined with a counterflow type condenser section. Generally, thermosiphon devices are made such that both the evaporator and condenser sections operate in a counterflow-type mode, or with a closed loop flow. Counterflow type devices tend to be less efficient than closed loop systems, but are suitable for certain applications and tend to be lower cost systems. On the other hand, closed loop systems can have a larger overall size, e.g., because of the dedicated flow paths and other components. By combining a closed loop evaporator section with a counterflow condenser section, the inventors have found that improved thermal performance in comparison to standard counterflow devices can be provided, but with lower equipment cost and overall size of the system.
For example, a thermosiphon cooling device may include a closed loop evaporator section having at least one evaporation channel with an inlet and an outlet. The evaporator section may be arranged to receive heat and evaporate a liquid in the at least one evaporation channel to deliver vapor to the evaporation channel outlet. A liquid return path, having an inlet and an outlet, may deliver condensed liquid to the at least one evaporation channel inlet, and the liquid return path may be arranged such that downward flow of condensed liquid from the liquid return path inlet to the liquid return path outlet is separate from an upward flow of vapor to the evaporation channel outlet. Thus, the evaporator section may operate with a closed loop flow. A condenser section of the device may include at least one condensing channel arranged to receive vapor from the at least one evaporation channel that flows upwardly in the condensing channel and arranged to transfer heat from the vapor to a surrounding environment to condense the vapor to a liquid which flows downwardly in the condensing channel to the liquid return path inlet. That is, the condenser section may operate in a counterflow arrangement in which vapor and condensed liquid flow in the same channel(s).
In some embodiments, a manifold may fluidly connect the at least one evaporation channel and the liquid return path with the at least one condensing channel. Thus, the manifold may function as a vapor/liquid separator such that vapor entering the manifold is separated from any liquid in the manifold and flows into condensing channels. On the other hand, liquid in the manifold may flow to the liquid return path. In some cases, the liquid return path inlet is positioned below the at least one evaporation channel outlet in the manifold so liquid preferentially flows into the liquid return path.
In one embodiment, the evaporator section is formed as a flat tube that is bent at a location where the liquid return outlet communicates with the at least one evaporation channel inlet. For example, the flat tube may be bent to form a 180 or other degree bend where the liquid return outlet communicates with the at least one evaporation channel inlet. In addition, or alternately, an outlet end of the flat tube at the evaporator channel outlet may be twisted about an axis along a length of the flat tube at the outlet end, and/or an inlet end of the flat tube at the liquid return path inlet may be twisted about an axis along a length of the flat tube at the inlet end. For example, inlet and/or outlet ends of the flat tube may be twisted 90 degrees about the axes. This type of arrangement may allow for simplified connections between the evaporator section and other parts of the thermosiphon device, e.g., the need for connectors to provide bends in the system flow path may be eliminated and replaced by bent/twisted tube sections.
In another aspect of the invention, a thermosiphon device may include a closed loop condenser section that has a liquid bypass or exit path for condensed liquid in the vapor supply path of the condenser section. This arrangement may reduce the concern regarding condensate forming in the vapor supply path, e.g., allowing the vapor supply path to be positioned closely to condensing channels of the device in such a way that condensate may form in the vapor supply path. For example, a thermosiphon cooling device includes a closed loop evaporator section having at least one evaporation channel with an inlet and an outlet and arranged to receive heat and evaporate a liquid in the at least one evaporation channel to deliver vapor to the evaporation channel outlet. A liquid return path, having an inlet and outlet, may deliver condensed liquid to the at least one evaporation channel. A condenser section may have a vapor supply channel arranged to receive vapor from the outlet of the at least one evaporation channel and deliver vapor to an upper end of the at least one condensing channel. The at least one condensing channel may be arranged to transfer heat from the vapor to a surrounding environment to condense the vapor to a liquid which flows downwardly in the condensing channel to the liquid return path inlet. The vapor supply channel may carry vapor flow, which is separate from condensed liquid flow in the condensing channels, yet the vapor supply channel may be immediately adjacent the at least one condensing channel. This is in contrast to systems which have a similar closed loop condenser arrangement, but have the vapor supply path physically separated from condensing channels. This separation is typically provided so that vapor in the vapor supply does not prematurely condense, which is known to disrupt the cyclical flow in a thermosiphon. However, the inventors have discovered that a vapor supply path can be provided immediately adjacent one or more condensing channels, and yet may be configured so that gravity-driven cyclical flow is not disrupted. In some embodiments, for example, an area where the vapor supply channel is fluidly connected to the outlet of the evaporator section may be provided with a liquid bypass or other flow path so that condensate in the vapor supply channel may drain to a manifold or other liquid return path of the device.
For example, an outlet end of the at least one evaporator channel may be inserted into or otherwise coupled to the vapor supply channel, and the coupling may be arranged so that liquid flowing downwardly in the vapor supply channel does not enter the outlet end of the at least one evaporator channel. Instead, the coupling between the outlet end and the vapor supply channel may have one or more gaps or other flow paths so that liquid in the vapor supply channel can bypass the outlet end and flow to a liquid return path of the device. In some embodiments, a manifold may fluidly connect the inlet of the liquid return path with a bottom of the at least one condensing channel, and any liquid that exits from the vapor supply channel may enter the manifold. As a result, the vapor supply channel may be surrounded by condensing channels without disrupting flow in the thermosiphon device because liquid in the vapor path can be removed. For example, the condenser section may have a plurality of parallel condensing channels, and the vapor supply channel may be located between two sets of the condensing channels, e.g., along a centerline of the condenser section.
In another aspect of the invention, a thermosiphon cooling device includes an evaporator section with at least one evaporation channel having an inlet and an outlet and arranged to receive heat and evaporate a liquid in the at least one evaporation channel to deliver vapor to the evaporation channel outlet. A liquid return path, having an inlet and outlet, may deliver condensed liquid to the at least one evaporation channel, e.g., by having the outlet fluidly coupled to the evaporation channel inlet. The evaporator section may be formed as a flat tube that is bent, e.g., at 180 degrees or more or less, at a location where the liquid return outlet communicates with the at least one evaporation channel inlet. Such an arrangement may make for a much simplified evaporator section, e.g., by eliminating one or more connections between parts of an evaporator section required by other arrangements. The bent, flat tube configuration for an evaporator section is also applicable to a condenser section. For example, a condenser section may have at least one condenser channel with an inlet and an outlet and arranged to transfer heat and condense a vapor in the at least one condenser channel to deliver condensed liquid to the condenser channel outlet. A vapor supply path, having an inlet and an outlet, may deliver evaporated liquid to the inlet of the at least one condenser channel, e.g., by having the outlet fluidly coupled to the condenser channel inlet. The condenser section may be formed as a flat tube that is bent, e.g., at 180 degrees or more or less, at a location where the vapor supply path outlet communicates with the at least one condenser channel inlet.
In some embodiments, a manifold may be fluidly connected to the at least one evaporation channel outlet and the liquid return path inlet, and the liquid return path inlet may be positioned below the at least one evaporation channel outlet in the manifold. This construction may make for a simplified device, since a single manifold may be used to make vapor and liquid connections between the evaporator section and the condenser section, as well as function as a vapor/liquid separator.
In some embodiments, an outlet end of the flat tube at the evaporator channel outlet may be twisted about an axis along a length of the flat tube at the outlet end, and/or an inlet end of the flat tube at the liquid return path inlet may be twisted about an axis along a length of the flat tube at the inlet end. For example, the inlet and outlet ends of the flat tube may be twisted 90 degrees about the axes. This arrangement may allow for relatively compact connections between the evaporator section and other portions of the thermosiphon device without the use of additional connectors. Instead, the tube ends may be twisted as needed to provide a suitably compact and correctly oriented connection.
In another aspect of the invention, a thermosiphon cooling includes a condenser section having a plurality of condensing channels arranged to receive evaporated liquid and arranged to transfer heat from the evaporated liquid to a surrounding environment to condense the evaporated liquid to a liquid which flows downwardly in the condensing channels. The condenser section may include first and second panels that sandwich a channel-defining member so as to form the plurality of condenser channels, with the first and second panels defining a lower manifold that fluidly connects lower ends of the condenser channels. Such an arrangement may provide a simple and efficient design which eliminates a variety of parts, such as an end cap for the upper ends of the condenser channels. In some embodiments, the first and second panels define an upper manifold that fluidly connects upper ends of the condenser channels, e.g., so the condenser section can be used as a closed loop type device. Alternately, or in addition, the channel-defining member may define a vapor supply channel, e.g., that is located between sets of condensing channels.
In another illustrative embodiment, a thermosiphon cooling device includes an evaporator section with a tube and an axially extending separation wall within the tube to separate at least one evaporation channel from a liquid return path in the tube. The axially extending separation wall may have a bottom end that is positioned away from a lower end of the tube and define the inlet for the at least one evaporation channel. This configuration may provide for a simplified evaporator device that includes a single tube and a plate or other element positioned inside the tube to function as a separation wall. In some embodiments, the tube may also define a condenser section, e.g., an inner surface of the tube may have fins or channels that define one or more condensing channels, one or more evaporation channels, and one or more liquid return paths. In some cases, the fins or channels at the at least one evaporation channel are different from the fins or channels at the liquid return path. For example, the channels or grooves at the evaporation channels may be arranged to enhance liquid boiling, whereas the channels or grooves at the liquid return path may be arranged to enhance condensate consolidation and flow.
Although not described above, conductive thermal transfer structure, such as a plurality of fins, may be in direct, conductive thermal contact with portions of an evaporator section, e.g., adjacent one or more evaporation channels, in contact with portions of a condenser section, e.g., adjacent one or more condensing channels, and/or associated with other parts of the thermosiphon device to influence heat transfer and/or cooling fluid flow.
These and other aspects of the invention will be apparent from the following description. Also, it should be appreciated that different aspects of the invention may be combined in a variety of different ways. For example, aspects related to closed loop evaporator flow and counterflow condenser flow may be combined with the use of a flat, bent tube evaporator, and/or with a condenser formed by sandwiching a channel-defining member between opposed panels.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate select embodiments of the present invention and, together with the description, serve to explain the principles of the inventions. In the drawings:

FIG. 1 is a perspective view of a thermosiphon device in an illustrative embodiment that incorporates aspects of the invention;

FIG. 2 shows a cross sectional side view of the FIG. 1 device;

FIG. 3 shows a cross sectional close up view of a modified version of the FIG. 2 embodiment;

FIG. 4 shows a cross sectional close up view of a modified version of the FIG. 3 embodiment;

FIG. 5 shows a cross sectional close up view of a condenser section having a channel-defining member;

FIG. 6 shows a partial section view of headers joining condenser and evaporator sections in an illustrative embodiment;

FIG. 7 shows a perspective view of thermosiphon devices having a manifold that fluidly couples evaporator sections at a turnaround end of the sections;

FIG. 8 shows a perspective view of a thermosiphon device having inlet and outlet ends of evaporator sections coupled to a connecting tube of a manifold;

FIG. 9 shows a close up view of a manifold arrangement in the FIG. 8 embodiment;

FIG. 10 shows an evaporator section of a thermosiphon device that includes thermal transfer structure having fins extending between evaporator sections;

FIG. 11 shows a perspective view of a thermosiphon device in which a tube defines condenser and evaporator sections;

FIG. 12 shows a cross sectional perspective view of an evaporator section of the tube in the FIG. 11 embodiment;

FIG. 13 shows a cross sectional view along the line 13-13 in FIG. 12; and

FIG. 14 shows side view of a thermosiphon device in another illustrative embodiment.

DETAILED DESCRIPTION

Aspects of the invention are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. Other embodiments may be employed and aspects of the invention may be practiced or be carried out in various ways. Also, aspects of the invention may be used alone or in any suitable combination with each other. Thus, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
In accordance with an aspect of the invention, a thermosiphon cooling device includes an evaporator section formed as a flat tube that is bent at a location where the liquid return outlet communicates with the at least one evaporation channel inlet. For example, the evaporator section may include at least one evaporation channel having an inlet and a liquid return path having an outlet that is fluidly coupled to the evaporation channel inlet, where the at least one evaporation channel and the liquid return path are formed as a flat tube that is bent at a location where the liquid return outlet communicates with the at least one evaporation channel inlet. For example, the flat tube may be arranged as a multi-port extruded (MPE) structure that is generally flat and has a plurality of parallel channels extending along the tube length, at least in the evaporator channel section. The MPE tube may be bent, e.g., to form a 180 degree bend, that defines an area where the liquid return path joins to the evaporation channel(s). Such an arrangement may make for a simplified, low-weight construction that can be made at relatively low cost.
For example, FIG. 1 shows an illustrative embodiment of a thermosiphon device 10, e.g., used to cool electronics devices in a closed cabinet or other enclosure, or in an open environment. That is, as is understood by those of skill in the art, a heat-receiving area 5 of one or more evaporator sections 2 of the device 10 may be thermally coupled with electronics or other heat-generating devices to be cooled, e.g., by direct contact, heat pipe(s), heat exchanger, etc. Vapor generated in one or more evaporation channels in the heat-receiving area 5 may flow to one or more condenser sections 1 that dissipate heat received from the evaporator section(s) 2, e.g., to air or other fluid in an environment around the device 10. In some embodiments, the evaporator section(s) 2 may be positioned inside of a sealed enclosure while the condenser section(s) 1 are located in an environment outside of the enclosure. By providing the evaporator section(s) 2 inside a sealed enclosure and the condenser section(s) 1 outside of the enclosure, devices in the enclosure may be cooled while being contained in an environment protected from external conditions, e.g., protected from dirt, dust, contaminants, moisture, etc. Of course, use of a thermosiphon device with a sealed enclosure is not required, e.g., the device may be used in a completely open system in which heat generating devices to be cooled are thermally coupled to one or more evaporator section(s) 2 of the device 10.
In simplified form, the thermosiphon device 10 operates to cool heat generating devices by receiving heat at the heat-receiving area 5 of the evaporator section(s) 2 such that liquid in evaporation channels 22 boils or otherwise vaporizes. Heat may be received at the evaporation channels 22 by warm air (heated by the heat generating devices) flowing across a thermal transfer structure (e.g., heat sink fins) that is thermally coupled to the evaporation channels 22 or in other ways, such as by a direct conductive path, one or more heat pipes, a liquid heat exchanger, etc. Vapor flows upwardly from the evaporation channels 22 and into a vapor supply path 11 of a condenser section 1. The vapor continues to flow upwardly in the vapor supply path 11 until reaching a turnaround 14 of the condenser section 1. At this point, the vapor flows downwardly into one or more condensing channels 12 of the condenser section 1, where the vapor condenses to a liquid and flows downwardly into the manifold 3. Heat removed from the vapor during condensation may be transferred to thermal transfer structure coupled to the condensing channels 12, e.g., one or more fins conductively coupled to the condenser section 1 adjacent the condensing channels 12. In turn, heat may be removed from the thermal transfer structure by cool air flowing across the structure, by a liquid bath, a liquid heat exchanger, refrigerant coils, or other arrangement. The condensed liquid flows downwardly from the condensing channels 12 into a liquid return path 21 of an evaporator section 2 until reaching a turnaround 24 of the evaporator section 2. The liquid then enters an evaporator channel(s) 22 and the process is repeated.
In the FIG. 1 embodiment, the evaporator section(s) 2 are each formed from a single flat tube, which may be arranged as an MPE tube or other suitable structure. The tube is bent to form the turnaround 24, i.e., where an outlet of the liquid return path 21 is coupled to the inlet of the evaporation channel(s) 22. Any suitable bend may be provided, and in this example, a 180 degree bend is made about an axis that is parallel to the plane of the tube and is perpendicular or otherwise transverse to the length of the tube. Other bend arrangements are possible, though, including a bend about an axis that is perpendicular to the plane of the tube. The heat-receiving area 5 of the evaporator section(s) 2 may be out of contact with the liquid return path 21 portion, e.g., so little or no heat transfer occurs between the two.
In accordance with another aspect of the invention, an inlet end and/or an outlet end of the tube forming the evaporator section(s) 2 may be twisted, e.g., about an axis that is along the length of the tube. In this embodiment, the inlet and outlet ends of the tube are twisted about an axis that extends along an approximate center of the tube along the length of the tube. However, twisting about other axes extending along a length of the tube or otherwise arranged are possible.
While in this embodiment only the evaporator section(s) 2 are formed from a bent, flat tube, one or more condenser sections 1 may be formed from a bent tube in addition or alternately to the evaporator section(s) 2. In such a case, the condenser section may have at least one condenser channel formed as a part of the tube with each condenser channel having an inlet and an outlet and arranged to transfer heat and condense a vapor in the at least one condenser channel to deliver condensed liquid to the condenser channel outlet. Another part of the tube may form a vapor supply path for delivering evaporated liquid to the inlet of the at least one condenser channel. The vapor supply path may have an inlet and an outlet that is fluidly coupled to the condenser channel inlet, and the flat tube may be bent at a location where the vapor supply path outlet communicates with the at least one condenser channel inlet. Moreover, ends of the tube may be twisted, e.g., in a way similar to the evaporator sections 2 shown in FIG. 1.
FIG. 2 shows a cross sectional side view of the FIG. 1 device, and illustrates how an outlet end 26 of the evaporator section 2 is coupled to the inlet of the vapor supply path 11 of the condenser section 1. As described above and in accordance with an aspect of the invention, this coupling may in some cases not be liquid-tight so that any condensate in the vapor supply path 11 can flow through a gap or other flow path between the outlet end 26 of the evaporator section 2 and the vapor supply path 11 and into the manifold 3. For example, in this embodiment, the vapor supply path 11 is positioned adjacent condensing channels 12, which may increase the likelihood that vapor in the supply path 11 condenses to form a liquid. Such condensed liquid may flow downwardly in the vapor supply path 11, but may not enter the outlet end 26 of the evaporator section 2 because the liquid may exit the vapor supply path 11 via a bypass or other flow path to the manifold 3.
That is, the manifold 3 in this embodiment provides a liquid flow path for condensed liquid to return to the evaporator section 2. The inlet end 27 of the evaporator section 2 (i.e., at the inlet to the liquid return path 21) is joined to the manifold 3, which fluidly couples the lower ends of the condenser channels 12 to the inlet end 27. Thus, vapor may flow upwardly in the vapor supply path 11 and into the upper ends of the condenser channels 12. Condensed liquid may flow downwardly into the manifold 3 and be routed to the inlet end 27 of the evaporator section 2. Since the inlet end 27 is positioned below the outlet end 26 of the evaporator section 2, liquid in the manifold 3 will flow first into the inlet end 27. In this embodiment, the manifold 3 includes a tube 35 that is coupled to each of the separate condenser sections 1, e.g., to allow for easier filling of the device 10 with cooling liquid and/or pressure equalization across different portions of the device.
FIG. 3 shows a cross sectional close up view of a modified version of the FIGS. 1 and 2 embodiment in which a connecting tube 35 is not provided. Other than this change, however, this embodiment is identical to that in FIGS. 1 and 2. In this embodiment, the manifold 3 is formed from a pair of clam shell pieces or sections 3 a, 3 b that may be stamped, molded or otherwise formed to receive the condenser section 1 at an upper opening and to receive the inlet and outlet ends 27, 26 of the evaporator section 2 at respective lower openings. A single brazing or other suitable operation may join the manifold sections 3 a, 3 b, the condenser section 1 and the ends 26, 27 of the evaporator section 2. Of course, other construction arrangements are possible, but this arrangement provides for a simple, relatively lightweight and inexpensive device.
Thermal transfer structure 9, such as one or more fins 9, may be thermally coupled to the condenser section(s) 1, e.g., in areas adjacent the condenser channels 12. This may assist in heat transfer from vapor in the condenser channels 12 and/or affect how cooling fluid flows across the thermal transfer structure 9. Of course, any suitable thermal transfer structure may be employed, including heat sink structures, heat pipes, heat exchangers, cold plates, etc.
In accordance with another aspect of the invention, a thermosiphon device may include a closed loop evaporator section, i.e., a liquid return path that leads to the inlet of one or more evaporation channels which have an outlet separate from the liquid return path, and a counterflow-type condenser section. That is, the condenser section may have at least one condensing channel arranged to receive vapor from at least one evaporation channel that flows upwardly in the condensing channel and arranged to transfer heat from the vapor to a surrounding environment to condense the vapor to a liquid which flows downwardly in the condensing channel to the liquid return path inlet. Thus, vapor to be condensed flows upwardly in the condensing channels while condensed liquid flows downwardly in the condensing channels. This is in contrast to a system like that in FIG. 2 where vapor flows upwardly in a dedicated vapor supply path 11 and enters inlets to condensing channels 12 at a upper end of the channels. Instead, vapor may enter the condensing channels 12 at a lower end of the channels, and condensed liquid may likewise exit from the lower end of the channels. One benefit to such an arrangement is that a turnaround 14 need not be provided for the condenser sections 1, reducing materials and cost. Instead, condenser channels 12 may “dead end” at an upper end of the channels so the channels are not in fluid communication at the upper end. Also, a vapor supply path 11 need not be provided, allowing for an increased density of condenser channels 12.
FIG. 4 shows a cross sectional close up view similar to that of FIG. 3, except that the FIG. 1 embodiment has been modified to eliminate the vapor supply path 11. As a result, the inlet and outlet ends 27, 26 of the evaporator section 2 extend into the manifold 3 such that both the outlet of the evaporator channels 22 and the inlet of the liquid return path 21 are in fluid communication with the manifold 3 and the lower ends of the condenser channels 12. The inlet end 27 is positioned below the outlet end 26 so that liquid preferentially flows into the inlet end 27. FIG. 4 also shows how a connector tube 35 may be joined to the manifold 3, e.g., a slot or opening 35 a of the tube 35 may be aligned with a corresponding opening at a bottom of the manifold 3 so that the tube 35 and the manifold 3 are in fluid communication.
In another aspect of the invention, a thermosiphon device includes a condenser section with first and second side panels that sandwich a channel-defining member so as to form a plurality of condenser channels and/or a vapor supply path. In some embodiments, the first and second side panels may define a lower manifold that fluidly connects lower ends of the condenser channels, and/or define an upper manifold that fluidly connects upper ends of the condenser channels. Such a structure may provide for a condenser section that is simple in construction, lightweight, and efficient. The channel-defining member may be arranged in a variety of ways, such as a stamped plate with walls to define the condensing channels when positioned between the side panels.
For example, FIG. 5 shows a cross sectional view of a condenser section 1 that has one of the side panels 16 removed such that a channel-defining member 17 can be seen along with a side panel 15. In this embodiment, the channel-defining member 17 is formed as a punched, stamped or otherwise formed element with a plurality of wall portions to define, at least partially, a plurality of condensing channels 12 and a vapor supply path 12. Of course, other arrangements for the channel-defining member 17 is possible, e.g., the channel-defining member 17 may be formed as a set of individual ribs that are assembled between the side panels 15, 16, may be formed as a corrugated or extruded sheet, etc. Also, the channel-defining member 17 need not necessarily define continuous channels, but rather could have a pattern of dints, cutouts or pin fins, etc. that define discontinuous channels. In this embodiment, the channel-defining member 17 is arranged to be brazed or soldered to the inside surface of the side panels 15, 16, but it should be understood that other arrangements are possible, such as forming the channel-defining member 17 as part of one or both of the panels 15, 16. One advantage to the illustrated embodiment is that the condenser section 1 can be formed by simply positioning the channel-defining member 17 on a surface of a metal sheet, and then folding the metal sheet so that the channel-defining member 17 is positioned between opposed parts of the sheet, i.e., side panels 15, 16 of the condenser section 1. This can make for a very inexpensively made and efficient condenser section 1. Also, if the condenser section 1 is to operate as a counterflow type device, an upper header or void at the turnaround end need not be provided. That is, a vapor supply path 11 need not be provided and each of the condensing channels 12 may “dead end” at an upper end of the channels so that the upper ends of the channels 12 are not fluidly coupled together. This arrangement may also allow for the elimination of a terminating cap at the turnaround end of the condenser section 1, e.g., because the panels 15, 16 may be joined together to close the condenser section 1.
In this embodiment, thermal transfer structure 9 in the form of U-shaped fins 9 are attached to one or both of the panels 15, 16, e.g., to assist in transferring heat from vapor in the condensing channels 12. In this embodiment, the fins 9 are mounted parallel to the direction in which the condensing channels 12 extend, but could be positioned in other ways, such as at different angles. That is, this illustrative embodiment is configured to operate using natural convective flow such that air or other fluid in or around the fins 9 is heated and flows upwardly due to gravity. However, the fins 9 may be arranged for forced convection applications, e.g., where the fins 9 rotated 90 degrees so the fins 9 extend in a direction perpendicular to the direction along which the condensing channels 12 extend. Configuring the condenser section 1 to operate in as a forced convection device may enable the condenser section 1 to be reduced in size, assuming a power input is unchanged. It should also be noted that the thermal transfer structure 9 may take a variety of different shapes or configurations than that shown, e.g., the fins 9 may be louvered, corrugated, include pin elements, etc.
In accordance with another aspect of the invention, a header used to join a condenser section 1 and an evaporator section 2 may be arranged to include a connecting tube or other conduit so that adjacent headers can fluidly communicate with each other. That is, while the embodiments in FIGS. 1 and 4 have a separate tube 35 that is attached to headers 3, tube or other conduit sections may be formed as part of each header and joined together to form a connecting tube 35. For example, FIG. 6 shows an embodiment in which headers 3 include a connecting tube 35 formed as part of the header 3 structure. The connecting tubes 35 of adjacent headers 3 are joined together, e.g., by brazing, solder, welding, adhesive, etc. so that the headers 3 fluidly communicate via passageways 35 b. The tubes 35 may be formed in any suitable way, such as by drawing, drilling, casting, molding, etc. This view in FIG. 6 also shows how the headers 3 are formed from two clam-shell type parts or opposed sections 3 a, 3 b that are joined together to form the header 3. The sections 3 a, 3 b may be formed by stamping, molding, etc. and may allow for simplified assembly of the header 3 with the condenser and evaporator sections 1, 2. For example, the manifold end of the condenser section 1, and the inlet and outlet ends 27, 26 of the evaporator section 2 may be assembled with the header sections 3 a, 3 b, and all of the assembled parts attached together in a single operation, such as brazing. This can not only provide simplified assembly, but also allow for easier filling of the thermosiphon devices 10 in a single operation since the devices 10 are all in fluid communication with each other.
In some embodiments, thermosiphon devices ganged together to cool one or more heat generating devices may be fluidly coupled in ways or locations other than that shown in FIGS. 1 and 6. For example, FIG. 7 shows an illustrative embodiment where the turnarounds of the evaporator sections 2 are fluidly coupled by a manifold 29. In this case, the outlet end of the liquid return path 21 is coupled to the manifold 29, as is the inlet end of the evaporator channels 22. The manifold 29 may be provided in one or more separate sections, e.g., if the device 10 is operated at inclined angles, the manifold 29 may be divided into any number of sub-sections to avoid a situation where a part of the manifold 29 is drained of liquid. A similar approach may also be used for a central manifold 3 in case the device is to be operated at inclined angles.
Of course, other manifold arrangements are possible, such as that shown in FIG. 8 in which inlet and outlet ends 26, 27 of evaporator sections 2 are coupled to a connecting tube 35 of the manifolds 3. FIG. 9 shows a close up view, and illustrates that the inlet end 27 of the liquid return path 21 is positioned below the outlet end 26 of the evaporator channels 22 so that condensed liquid preferentially flows into the inlet end 27. The vapor speed in the vertical direction in the connector tube 35 and headers 3 is low due to the high area of the free liquid-vapor interface, which enhances liquid-vapor separation. Though the ends 26, 27 of the evaporator sections 2 are not twisted as in earlier embodiments, the ends could be twisted to engage with the connector tube 35 and/or header 3. FIG. 9 also illustrates how the manifolds 3 can be formed from pairs of opposed sections 3 a, 3 b which define an opening to receive a lower end of the condenser section 1 and an opening to communicate with the connector tube 35.
Although the embodiments above only describe the use of thermal transfer structure 9, such as a finned heat sink, with condenser sections 1, thermal transfer structure may be used with evaporator sections 2. For example, FIG. 10 shows an embodiment in which a finned heat sink 9 has fins 91 extending between adjacent evaporator sections 2. The fins 91 and other portions of the thermal transfer structure 9 are out of contact with the liquid return path 21 portion of the evaporator section 2 so as to minimize heat transfer to the liquid return path 21. However, the heat sink 9 is directly coupled to the heat receiving area 5/evaporation channels 22 portion of the evaporator sections 2 and to one or more heat-generating devices, such as electronic circuitry. The fins 91 may help dissipate heat, particularly where the thermosiphon device 10 is used in an open environment, and having the fins 91 extend between the evaporator sections 2 (and away from the heat generating devices) may help reduce the overall size of the device 10 while enhancing its cooling capability. While in this illustrated embodiment, the thermal transfer structure 9 is arranged as an extruded (or otherwise formed) heat sink structure with a base plate secured to the heat receiving area 5 and fins 91 extending from the base plate between the evaporator sections 2, the thermal transfer structure 9 may be arranged in other ways. For example, the thermal transfer structure 9 could be made part of a cabinet or other housing for the heat generating devices, e.g., the thermal transfer structure 9 could include a cool plate attached to a cabinet in which heat generating devices are located. In another arrangement, heat generating devices may be attached directly to the thermal transfer structure 9 that is integrated with a cabinet or housing. Thus, the thermal transfer structure 9 may provide a mounting support for one or more thermosiphon devices 10 and/or one or more heat-generating devices inside of a cabinet or housing. That is, thermal transfer structure 9 may be secured in a cabinet or housing (or other configuration), and one or more thermosiphon devices 10 may be mounted to the thermal transfer structure 9. One or more heat generating devices may also be mounted to the thermal transfer structure 9, or may be supported by a cabinet or other structure.
In another aspect of the invention, a single tube may incorporate both an evaporator section and a condenser section. The evaporator section of the tube may include different internal protuberance and/or groove arrangements arranged to enhance condensation routing or liquid evaporation. Also, a part of the evaporation section may include a separation wall that extends axially in the tube and separates an evaporation portion from a liquid return path in the tube. The separation wall may have a low thermal conductivity and may made with grooves in the tube interior to retain the wall in place. For example, FIG. 11 shows a perspective view of a thermosiphon device 10 with one of the tubes 25 defining a condenser and evaporation section 1, 2 shown in cross section. Ends of the tubes 25 may be closed by caps 14, 24, or otherwise closed. The condenser section 1 includes multiple grooves formed in the inner wall of the tube 25 that function as condensing channels 12. Vapor produced in the evaporation section 2 may flow upwardly in the grooves of the tube inner wall and/or at a central portion of the tube 25. Thermal transfer structure 9, such as one or more fins, may be coupled to the condenser section 1 to assist in heat transfer from the vapor in the condenser sections 1 and/or to attach the tubes 25 together.
The evaporator section 2 also includes grooves in the inner wall of the tube 25, e.g., to provide condensate liquid flow paths and evaporation channels. A separation wall 23 may be positioned in the tube 25 and extend axially along the tube 25 to separate evaporation channels 22 from a liquid return path 21 of the evaporator section 2. FIG. 12 shows a close up view of the evaporator section 2 and illustrates how the separation wall 23 extends along a portion of the tube 25. As can be seen in FIG. 13, the separation wall 23 may engage with grooves 19 that hold the separation wall 23 in place and may provide a liquid-tight seal between the wall 23 and the inner wall of the tube 25. In this embodiment, the separation wall 23 may be slid into the grooves 19 from the end of the tube 25, although other arrangements are possible. In any case, the separation wall 23 may extend across an internal space of the tube 25 so as to form a chord or chord-like element. Grooves and/or fins that define the evaporation channels 22 may be arranged differently than grooves that define liquid return paths 21. For example, the grooves and/or fins at the evaporation channels 22 may include sharp corners to promote boiling, whereas grooves/fins at the liquid return paths 21 may include convex-shaped flutes at a radially inner end that enable very thin condensation films and use surface tension to urge the condensed fluid to flow into the grooves. The separation wall 23 may have a low thermal conductivity so that thermal transfer between the area around the evaporation channels 22 to the liquid return path 21 is minimized. One or more heat generating devices may be thermally coupled to the tube 25 in an area where the evaporation channels 22 are located, e.g., on the left side in FIG. 13. While in this embodiment, the tubes 25 are formed from a single continuous piece, two or more different tube sections may be joined together, e.g., where a condenser section 1 is made of aluminum and an evaporator section 2 is made of copper. Other variations are possible as well, such as a portion of the tube 25 where the evaporation channels 22 are provided may be made of a highly thermally conductive material, such as copper, while another portion of the tube 25 where the liquid return path 21 is provided may be made of a lower thermal conductivity material, such as aluminum or plastic. The tube 25 may be filled with cooling liquid at a relatively low level, e.g., between a bottom end of the separation wall 23 and an upper end of the wall, since the evaporation channels 22 need not be completely flooded.
FIG. 14 shows yet another illustrative embodiment of a thermosiphon device 10. In this embodiment, a condenser section 1 having multiple condensing channel 12 extends between upper and lower headers 3, which may be arranged like that shown in FIG. 4. Upper and lower connecting tubes 19 and 35 may fluidly connect multiple headers 3, if provided. An evaporation section 2 includes a tube, e.g., a flat, multi-channel tube, that extends from the lower tube 35 to the upper tube 19. A liquid return path 21 extends from the lower tube 35 and provides liquid to a heat receiving area 5 of the evaporator section 2, e.g., where one or more evaporation channels 22 is provided. Vapor produced at the heat receiving area 5 flows upwardly to the upper tube 19, where the vapor enters the condensing channels 12.
The embodiments provided herein are not intended to be exhaustive or to limit the invention to a precise form disclosed, and many modifications and variations are possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Although the above description contains many specifications, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of alternative embodiments thereof
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified.
The use of “including,” “comprising,” “having,” “containing,” “involving,” and/or variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.
While aspects of the invention have been described with reference to various illustrative embodiments, such aspects are not limited to the embodiments described. Thus, it is evident that many alternatives, modifications, and variations of the embodiments described will be apparent to those skilled in the art. Accordingly, embodiments as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit of aspects of the invention.

Claims

1. A thermosiphon cooling device including:

an evaporator section including at least one evaporation channel having an inlet and an outlet and arranged to receive heat and evaporate a liquid in the at least one evaporation channel to deliver vapor to the evaporation channel outlet, and a liquid return path for delivering condensed liquid to the at least one evaporation channel, the liquid return path having an inlet and an outlet that is fluidly coupled to the evaporation channel inlet, wherein the evaporator section is formed as a flat tube that is bent at a location where the liquid return outlet communicates with the at least one evaporation channel inlet; OR

a condenser section including at least one condenser channel having an inlet and an outlet and arranged to transfer heat and condense a vapor in the at least one condenser channel to deliver condensed liquid to the condenser channel outlet, and a vapor supply path for delivering evaporated liquid to the inlet of the at least one condenser channel, the vapor supply path having an inlet and an outlet that is fluidly coupled to the condenser channel inlet, wherein the condenser section is formed as a flat tube that is bent at a location where the vapor supply path outlet communicates with the at least one condenser channel inlet.

2. The device of claim 1, including the evaporator section and further comprising a manifold fluidly connected to the at least one evaporation channel outlet and the liquid return path inlet.

3. The device of claim 2, wherein the liquid return path inlet is positioned below the at least one evaporation channel outlet in the manifold.

4. The device of claim 2, wherein the flat tube is bent to form a 180 degree bend where the liquid return outlet communicates with the at least one evaporation channel inlet.

5. The device of claim 4, wherein an outlet end of the flat tube at the evaporator channel outlet is twisted about an axis along a length of the flat tube at the outlet end, and wherein an inlet end of the flat tube at the liquid return path inlet is twisted about an axis along a length of the flat tube at the inlet end.

6. The device of claim 5, wherein inlet and outlet ends of the flat tube are twisted 90 degrees about the axes.

7. A thermosiphon cooling device including:

a closed loop evaporator section including at least one evaporation channel having an inlet and an outlet, the evaporator section being arranged to receive heat and evaporate a liquid in the at least one evaporation channel to deliver vapor to the evaporation channel outlet, and a liquid return path for delivering condensed liquid to the at least one evaporation channel inlet, the liquid return path having an inlet and an outlet that is fluidly coupled to the evaporation channel inlet and being arranged such that downward flow of condensed liquid from the liquid return path inlet to the liquid return path outlet is separated from an upward flow of vapor to the evaporation channel outlet, wherein the evaporator section is formed as a flat tube that is bent at a location where the liquid return outlet communicates with the at least one evaporation channel inlet; and

a condenser section including at least one condensing channel arranged to receive vapor from the at least one evaporation channel that flows upwardly in the condensing channel and arranged to transfer heat from the vapor to a surrounding environment to condense the vapor to a liquid which flows downwardly in the condensing channel to the liquid return path inlet.

8. The device of claim 7, further comprising a manifold fluidly connecting the at least one evaporation channel and the liquid return path with the at least one condensing channel.

9. The device of claim 7, wherein the liquid return path inlet is positioned below the at least one evaporation channel outlet in the manifold.

10. The device of claim 7, wherein the flat tube is bent to form a 180 degree bend where the liquid return outlet communicates with the at least one evaporation channel inlet.

11. The device of claim 10, wherein an outlet end of the flat tube at the evaporator channel outlet is twisted about an axis along a length of the flat tube at the outlet end, and wherein an inlet end of the flat tube at the liquid return path inlet is twisted about an axis along a length of the flat tube at the inlet end.

12. The device of claim 11, wherein inlet and outlet ends of the flat tube are twisted 90 degrees about the axes.

13. The device of claim 7, wherein the condenser section includes first and second flat panels that sandwich a channel-defining member so as to form a plurality of condensing channels, the first and second flat panels defining a lower manifold that fluidly connects lower ends of the condenser channels.

14. A thermosiphon cooling device including:

a closed loop evaporator section including at least one evaporation channel having an inlet and an outlet and arranged to receive heat and evaporate a liquid in the at least one evaporation channel to deliver vapor to the evaporation channel outlet, and a liquid return path for delivering condensed liquid to the at least one evaporation channel, the liquid return path having an inlet and an outlet that is fluidly coupled to the evaporation channel inlet; and

a condenser section including a vapor supply channel arranged to receive vapor from the outlet of the at least one evaporation channel and to deliver vapor to an upper end of the at least one condensing channel that is arranged to transfer heat from the vapor to a surrounding environment to condense the vapor to a liquid which flows downwardly in the condensing channel to the liquid return path inlet, wherein the vapor supply channel is adjacent the at least one condensing channel.

15. The device of claim 14, further comprising a manifold fluidly connecting the inlet of the liquid return path with a bottom of the at least one condensing channel.

16. The device of claim 14, wherein a wall that defines at least a part of the vapor supply channel defines at least a part of the adjacent at least one condensing channel.

17. The device of claim 14, wherein an outlet end of the at least one evaporator channel is inserted into the vapor supply channel.

18. The device of claim 14, wherein an outlet end of the at least one evaporator channel is coupled to the vapor supply channel such that liquid flowing downwardly in the vapor supply channel does not enter the outlet end of the at least one evaporator channel.

19. The device of claim 18, further comprising a manifold fluidly connecting the inlet of the liquid return path with a bottom of the at least one condensing channel, and wherein liquid flowing downwardly in the vapor supply channel enters the manifold.

20. The device of claim 14, wherein the condenser section includes a plurality of parallel condensing channels, and wherein the vapor supply channel is located between two sets of the condensing channels.

21. The device of claim 14, wherein the condenser section includes first and second flat panels that sandwich a channel-defining member so as to form a plurality of condensing channels and the vapor supply channel, the first and second flat panels defining a lower manifold that fluidly connects lower ends of the condenser channels, and defining an upper manifold that fluidly connects upper ends of the condensing channels and the vapor supply channel.

22. The device of claim 14, wherein the evaporator section is formed as a flat tube that is bent at a location where the liquid return outlet communicates with the at least one evaporation channel inlet.

23. The device of claim 12, wherein the flat tube is bent to form a 180 degree bend where the liquid return outlet communicates with the at least one evaporation channel inlet.

24. The device of claim 23, wherein an outlet end of the flat tube at the evaporator channel outlet is twisted about an axis along a length of the flat tube at the outlet end, and wherein an inlet end of the flat tube at the liquid return path inlet is twisted about an axis along a length of the flat tube at the inlet end.

25. The device of claim 24, wherein inlet and outlet ends of the flat tube are twisted 90 degrees about the axes.

26. The device of claim 25, wherein the condenser section includes a plurality of condensing channels, and wherein the outlet end of the flat tube is fluidly coupled to the vapor supply channel, and the inlet end of the flat tube is fluidly coupled to a manifold that fluidly couples lower ends of the plurality of condensing channels.

27. A thermosiphon cooling device including:

a condenser section including a plurality of condensing channels arranged to receive evaporated liquid and arranged to transfer heat from the evaporated liquid to a surrounding environment to condense the evaporated liquid to a liquid which flows downwardly in the condensing channels, wherein the condenser section includes first and second panels that sandwich a channel-defining member so as to form the plurality of condenser channels, the first and second panels defining a lower manifold that fluidly connects lower ends of the condenser channels.

28. The device of claim 27, wherein the first and second panels define an upper manifold that fluidly connects upper ends of the condenser channels.

29. The device of claim 27, wherein the channel-defining member additionally defines a vapor supply channel.

30. The device of claim 29, wherein the vapor supply channel is located between sets of condensing channels.

31. A thermosiphon cooling device including:

an evaporator section including a tube with an axially extending separation wall within the tube to separate at least one evaporation channel having an inlet and an outlet from a liquid return path for delivering condensed liquid to the at least one evaporation channel, the axially extending wall having a bottom end that is positioned away from a lower end of the tube and defining the inlet for the at least one evaporation channel.

32. The device of claim 31, wherein the tube defines a condenser section.

33. The device of claim 31, wherein an inner surface of the tube has fins or channels at the at least one evaporation channel.

34. The device of claim 33, wherein the inner surface includes fins or channels at the liquid return path, and the fins or channels at the at least one evaporation channel are different from the fins or channels at the liquid return path.

35. The device of claim 31, wherein the tube has upper and lower sections, the evaporator section being located at the lower section of the tube, the device further comprising a condenser section at the upper section of the tube.