EP2841863A1 - Double-walled dry heat exchanger coil with single-walled return bends - Google Patents

Double-walled dry heat exchanger coil with single-walled return bends

Info

Publication number
EP2841863A1
EP2841863A1 EP13782020.5A EP13782020A EP2841863A1 EP 2841863 A1 EP2841863 A1 EP 2841863A1 EP 13782020 A EP13782020 A EP 13782020A EP 2841863 A1 EP2841863 A1 EP 2841863A1
Authority
EP
European Patent Office
Prior art keywords
tubes
heat exchange
coil
walled
exchange coil
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP13782020.5A
Other languages
German (de)
French (fr)
Other versions
EP2841863A4 (en
EP2841863B1 (en
Inventor
Tom Byrne
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Evapco Inc
Original Assignee
Evapco Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Evapco Inc filed Critical Evapco Inc
Priority to PL13782020T priority Critical patent/PL2841863T3/en
Priority claimed from PCT/US2013/038177 external-priority patent/WO2013163400A1/en
Publication of EP2841863A1 publication Critical patent/EP2841863A1/en
Publication of EP2841863A4 publication Critical patent/EP2841863A4/en
Application granted granted Critical
Publication of EP2841863B1 publication Critical patent/EP2841863B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F17/00—Removing ice or water from heat-exchange apparatus
    • F28F17/005—Means for draining condensates from heat exchangers, e.g. from evaporators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D7/16—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation
    • F28D7/1615—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation the conduits being inside a casing and extending at an angle to the longitudinal axis of the casing; the conduits crossing the conduit for the other heat exchange medium
    • F28D7/1623—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation the conduits being inside a casing and extending at an angle to the longitudinal axis of the casing; the conduits crossing the conduit for the other heat exchange medium with particular pattern of flow of the heat exchange media, e.g. change of flow direction
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F1/00—Tubular elements; Assemblies of tubular elements
    • F28F1/003—Multiple wall conduits, e.g. for leak detection
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/10—Liquid cooling
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D2021/0019—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for
    • F28D2021/0028—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for cooling heat generating elements, e.g. for cooling electronic components or electric devices
    • F28D2021/0031—Radiators for recooling a coolant of cooling systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D2021/0019—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for
    • F28D2021/004—Other heat exchangers for particular applications; Heat exchange systems not otherwise provided for for engine or machine cooling systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D7/08—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being otherwise bent, e.g. in a serpentine or zig-zag
    • F28D7/082—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being otherwise bent, e.g. in a serpentine or zig-zag with serpentine or zig-zag configuration
    • F28D7/085—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being otherwise bent, e.g. in a serpentine or zig-zag with serpentine or zig-zag configuration in the form of parallel conduits coupled by bent portions

Definitions

  • the present invention relates to non-evaporative or "dry" heat exchangers, particularly those used to cool marine power transformers, although the invention can be used in any environment or situation where "dry" cooling solutions are required or desired.
  • the air used for cooling a transformer is passed over a series of coils through which water is circulated.
  • the prior art dry transformer cooling coils consist of a series of straight double-walled tubes which terminate at each end in sealed chambered headers.
  • the inner tubes of the straight tubes terminate in one chamber of the header, and the outer tubes terminate in a separate sealed chamber of the header. Cooling fluid is circulated through the inner tubes, and through the corresponding chambers of the headers at each end. Air is passed only over the tubes, and the chambered headers are located outside of the air stream. Any leak in one of the inner tubes is captured by its corresponding outer tube and travels to the separate header chamber at which the outer tubes terminate.
  • any water from leaks in the inner tubes finds its way to an outer tube chamber in one of the headers.
  • a leak detector is present at the bottom of each of the outer tube chambers to detect the presence of any water.
  • the headers are sealed from one another and from the outside with gaskets, but can be opened for inspection.
  • the disadvantages of this system include the material cost and complex construction of the chambered headers, with outer tubes terminating in one chamber and inner tubes terminating in another chamber.
  • the chambered headers restrict the ability to efficiently circuit the coil. Summary of the Invention
  • the present invention provides an elegant, safe and cost effective alternative to the prior art.
  • a non- evaporative heat exchanger coil having a plurality of straight inner tubes connected by a plurality of return bends.
  • the return bends allow fluid to move back and forth through the straight inner tubes of the coil.
  • the return bends are preferably located outside of the air flow passing over the coil.
  • the straight lengths of the inner tubes are each situated within a corresponding outer or "safety" tube.
  • the outer tubes preferably terminate at or before the return bends that connect the inner tubes to one-another, but in any event, the ends of the outer tubes are located outside of the air flow path.
  • the straight lengths of the heat exchange coil are double-walled or doubled tubed (inner tube within an outer tube), but the return bends are single-walled or single tubed.
  • the inner surfaces of the outer tubes are dimpled, grooved, ribbed, or otherwise patterned to create both contact points and voids between the inner and outer tubes. Leaks occurring in the straight inner tubes are captured by the outer tubes and the leaking fluid will flow in the space between the inner and outer tubes, drip or flow out the end of the outer tube, outside of the air flow path, to be captured in a drip pan or leak detector box at the bottom of the coil housing. According to an embodiment of the invention, leaks occurring in the return bends will also be captured in drip pan or leak detector box.
  • the bottom of the coil housing may be sloped so that only one leak detector is required.
  • capturing leaks outside of the airstream allows a dry transformer to continue operating, notwithstanding the existence of a leak.
  • this embodiment allows a ship to continue operating long enough to return to port for repair.
  • no chambered headers are used, and neither the return bends nor the ends of the outer tubes need be contained in special water-tight housings.
  • the return bends of the inner tubes are located outside of and separated from the air flow path over the coil.
  • the ends of the outer tubes are located outside of and separated from the air flow path over the coil.
  • the return bends and the ends of the outer tubes are located in a return bend box or other portion of the housing that is set off, but attached to, the primary housing.
  • the return bend box need not be water-tight.
  • fluid may also be introduced to and returned from the coil at one of the return bend boxes.
  • the leak detectors may be located at the bottom of the return bend boxes.
  • a sloping drain pan may be provided at the bottom of the coil so that water collected from leaks at one side of the coil drains to the other side of the coil for detection using a single leak detector.
  • the transformer may be turned off, either automatically or manually, so the leak can be repaired.
  • the space between the outer tubes and the inner tubes may be sealed or otherwise closed at one end of the coil, so that any leak in the inner tubes comes out only in the return bend box at the opposite end of the coil.
  • the space between the inner and outer tubes remains open at the header end of the coil, and is sealed at the opposite end of the coil, so that water from leaks in the inner tubes travels down the inside of the outer tubes and into the return bend box at the header end, where it is detected by a leak detector. According to this embodiment, there is no need for a sloping drain pan.
  • the coils may be situated in the bottom portion of a housing or "box" which is attached to a transformer transfer box.
  • Fans located in the top portion of the housing draw air from the transfer box and force it down over the coils where it is cooled, and the cooled air then exits the housing and returns to the transfer box. Heat transfer is facilitated with the use of fins fixed to the outside surfaces of the outer/safety tubes.
  • the coils can be an open system, in which water is drawn from a source, circulated through the coils and returned to the source, or a closed system in which the same water is circulated through the coils.
  • a closed system the water warmed by the air passing over them will be cooled in a separate system before returning to the coils of the present invention.
  • Figure 1A is a schematic of a section of heat exchange coil according to an embodiment of the invention.
  • Figure IB is a representation of the principles of the invention, accomplished with double-walled/double tubed straight tubes connected by single- walled/single tubed return bends.
  • Figure 2A is a front view schematic of a heat exchanger including a heat exchange coil according to an embodiment of the invention.
  • Figure 2B is a side view schematic of the heat exchanger shown in Figure 2A.
  • Figure 3 is a front perspective drawing of a transformer air cooling unit, including a heat exchanger according to an embodiment of the invention.
  • Figure 4 is a rear perspective drawing of a transformer air cooling unit shown in Figure 3.
  • Figure 5 is another rear perspective drawing of the transformer air cooling unit shown in Figure 3.
  • FIG 1 A shows a heat exchange coil 10 according to an embodiment of the invention.
  • Heat exchange coil 10 receives fluid from header 12 through connecting tube 14.
  • Connecting tube 14 is connected to inner tube 16a. Fluid travels through the heat exchange coil through inner tubes 16a, 16b, and 16c, via return bends 18a and 18b.
  • Inner tubes 16a, 16b, and 16c are expanded into outer tubes 20a, 20b, and 20c, respectively.
  • the inner surfaces of outer tubes 20a, 20b, and 20c have dimples, ribs, or other surface features 21 to create both contact between and voids between the inner and outer tubes to allow the passage of fluid between them (see Figure IB).
  • the outer surface of the inner tubes may have spacing features or be fitted with spacing devices to accomplish the same purpose.
  • Fins 22 are fixed to the outside surfaces of the outer tubes to enhance heat exchange. The air flow is directed only over the center portion 24 of the coil. Return bends 18a, 18b, and the ends 26 of outer tubes 20a, 20b and 20c are located outside the air flow path.
  • outer tubes are inserted into the fin matrix and expanded into the fins.
  • the inner tubes are then inserted into the outer tubes and expanded to provide contact at the contact surfaces and voids at non-contact locations.
  • the return bends may then be brazed to the inner tubes.
  • the air flow path (and hence the transformer, or any other device into which the air is ultimately directed) is protected from water contamination resulting from leaks in the heat exchange coil, and leaks are quickly and easily detected, all without complicated nested and sealed chambered header arrangements.
  • the space between the outer tubes and the inner tubes at one end of the coil may be brazed or otherwise sealed shut.
  • water from leaks in the inner tubes falls out of the outer tubes only in the return bend box at the end of the coil that is opposite the end where the space between the inner and outer tubes is sealed shut.
  • FIGS 2 A and 2B show schematics of a heat exchange unit 34 including a heat exchange coil according of the invention.
  • Return bend boxes 30a and 30b are situated outside of the primary housing of heat exchange unit, and contain the return bends (not shown) at both ends of the inner tubes (also not shown).
  • Fins 22 are shown, which as described above, are fixed to the outside surfaces of the outer tubes of the heat exchange coil.
  • Header 12 includes fluid inlet/outlets 32.
  • drain pan 28 may be provided with a slope between the return bend boxes so that water from leaks collected in one return bend box is made to travel to the other side of the coil where it can be detected with a leak detector.
  • FIGs 3-5 show different views of a transformer air cooling unit 36, including a heat exchanger according to an embodiment of the invention.
  • Transformer air cooling unit 36 includes fan box 38, resting on top of heat exchange unit 34.
  • Fans inside fan box 38 pull air from a transformer transfer unit (not shown) through louvers 39 and direct air down through heat exchange unit 34.
  • Air passes over the tubes (not visible in Figs 3-5) and fins 22, to exit the bottom of the unit.
  • Return bends and the ends of outer safety tubes are contained in return bend boxes 30a and 30b, outside of the air flow path, and the air flow path is preferably contained within heat exchange unit 34.
  • Water enters one of fluid inlet/outlets 32 and exits through the other according to desired water flow valving/settings.
  • Leak detector 40 detects the presence of water in the bottom of return bend box 30a.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Abstract

A dry heat exchanger coil having a plurality of straight inner tubes connected by a plurality of return bends. The return bends are located outside of the air flow passing over the coil. The inner tubes are situated within a corresponding outer or "safety" tube. The outer tubes do not contain and are not connected to return bends, but the ends of the outer tubes are located outside of the air flow path. Leaks in the inner tubes are captured by the outer tubes and the leaking fluid will flow in the space between the inner and outer tubes, flow out the end of the outer tube, to be captured in a drip pan at the bottom of the coil housing. Leaks occurring in the return bends will also be captured in drip pan.

Description

DOUBLE- WALLED DRY HEAT EXCHANGER COIL WITH SINGLE-WALLED
RETURN BENDS
[0001] This application claims priority from U.S. Provisional Application No.
61/638,275, the disclosure of which is incorporated herein in its entirety.
Field of the Invention
[0002] The present invention relates to non-evaporative or "dry" heat exchangers, particularly those used to cool marine power transformers, although the invention can be used in any environment or situation where "dry" cooling solutions are required or desired.
Background of the Invention
[0003] According to the prior art, the air used for cooling a transformer is passed over a series of coils through which water is circulated. The prior art dry transformer cooling coils consist of a series of straight double-walled tubes which terminate at each end in sealed chambered headers. The inner tubes of the straight tubes terminate in one chamber of the header, and the outer tubes terminate in a separate sealed chamber of the header. Cooling fluid is circulated through the inner tubes, and through the corresponding chambers of the headers at each end. Air is passed only over the tubes, and the chambered headers are located outside of the air stream. Any leak in one of the inner tubes is captured by its corresponding outer tube and travels to the separate header chamber at which the outer tubes terminate. Thus, any water from leaks in the inner tubes finds its way to an outer tube chamber in one of the headers. A leak detector is present at the bottom of each of the outer tube chambers to detect the presence of any water. The headers are sealed from one another and from the outside with gaskets, but can be opened for inspection. The disadvantages of this system include the material cost and complex construction of the chambered headers, with outer tubes terminating in one chamber and inner tubes terminating in another chamber. In addition, the chambered headers restrict the ability to efficiently circuit the coil. Summary of the Invention
[0004] The present invention provides an elegant, safe and cost effective alternative to the prior art.
[0005] While not intended to limit the scope of the invention, the description of the invention herein is presented in the context of a dry cooling solution for marine and other "dry" applications where the need to prevent water contact or contamination is critical. In particular, the present invention is particularly well-suited for use in a cooling unit used to cool transformers on ships. A "dry" cooling solution is required for marine transformers because if water contact causes a ship or other marine transformer to short circuit and fail, the ship can be left stranded without power. Therefore, marine transformer cooling systems are required to be "failsafe" systems that do not expose water to the transformer and which provide for the isolation and detection of any potential leaks in the system.
[0006] Therefore, there is presented according to an embodiment of the invention, a non- evaporative heat exchanger coil having a plurality of straight inner tubes connected by a plurality of return bends. The return bends allow fluid to move back and forth through the straight inner tubes of the coil. The return bends are preferably located outside of the air flow passing over the coil. The straight lengths of the inner tubes are each situated within a corresponding outer or "safety" tube. The outer tubes preferably terminate at or before the return bends that connect the inner tubes to one-another, but in any event, the ends of the outer tubes are located outside of the air flow path. Thus, the straight lengths of the heat exchange coil are double-walled or doubled tubed (inner tube within an outer tube), but the return bends are single-walled or single tubed. According to an embodiment of the invention, the inner surfaces of the outer tubes are dimpled, grooved, ribbed, or otherwise patterned to create both contact points and voids between the inner and outer tubes. Leaks occurring in the straight inner tubes are captured by the outer tubes and the leaking fluid will flow in the space between the inner and outer tubes, drip or flow out the end of the outer tube, outside of the air flow path, to be captured in a drip pan or leak detector box at the bottom of the coil housing. According to an embodiment of the invention, leaks occurring in the return bends will also be captured in drip pan or leak detector box. The bottom of the coil housing may be sloped so that only one leak detector is required.
[0007] According to an embodiment of the invention, capturing leaks outside of the airstream allows a dry transformer to continue operating, notwithstanding the existence of a leak. In the case of a marine transformer on a ship, this embodiment allows a ship to continue operating long enough to return to port for repair.
[0008] According to an embodiment of the invention, no chambered headers are used, and neither the return bends nor the ends of the outer tubes need be contained in special water-tight housings.
[0009] According to an embodiment of the invention, connecting the inner tubes using return bends, thereby avoiding chambered headers, allows for more flexibility in coil circuit design.
[00010] According to an embodiment of the invention, the return bends of the inner tubes are located outside of and separated from the air flow path over the coil.
[00011] According to an embodiment of the invention, the ends of the outer tubes are located outside of and separated from the air flow path over the coil.
[00012] According to an embodiment, the return bends and the ends of the outer tubes are located in a return bend box or other portion of the housing that is set off, but attached to, the primary housing. According to an embodiment of the invention, the return bend box need not be water-tight.
[00013] According to an embodiment of the invention, fluid may also be introduced to and returned from the coil at one of the return bend boxes. The leak detectors may be located at the bottom of the return bend boxes. According to a further embodiment of the invention, a sloping drain pan may be provided at the bottom of the coil so that water collected from leaks at one side of the coil drains to the other side of the coil for detection using a single leak detector. Preferably, when a leak is detected, the transformer may be turned off, either automatically or manually, so the leak can be repaired.
[00014] According to an embodiment of the invention, the space between the outer tubes and the inner tubes may be sealed or otherwise closed at one end of the coil, so that any leak in the inner tubes comes out only in the return bend box at the opposite end of the coil.
According to a preferred embodiment, the space between the inner and outer tubes remains open at the header end of the coil, and is sealed at the opposite end of the coil, so that water from leaks in the inner tubes travels down the inside of the outer tubes and into the return bend box at the header end, where it is detected by a leak detector. According to this embodiment, there is no need for a sloping drain pan.
[00015] According to an embodiment of the invention, the coils may be situated in the bottom portion of a housing or "box" which is attached to a transformer transfer box. Fans located in the top portion of the housing draw air from the transfer box and force it down over the coils where it is cooled, and the cooled air then exits the housing and returns to the transfer box. Heat transfer is facilitated with the use of fins fixed to the outside surfaces of the outer/safety tubes.
[00016] According to the invention, the coils can be an open system, in which water is drawn from a source, circulated through the coils and returned to the source, or a closed system in which the same water is circulated through the coils. In the case of a closed system, the water warmed by the air passing over them will be cooled in a separate system before returning to the coils of the present invention.
[00017] While the present invention is described in the context of a heat exchanger in which water is used to cool air that in turn is used to cool a power transformer, the invention is equally suited to other types of heat exchange. For example, persons of ordinary skill in the art would readily recognize that the invention can be equally used to effect heat exchange in reverse, whereby air passing over the coils can be used to receive heat from a
process/industrial fluid contained in the coil, thereby cooling the process fluid.
Description of the Drawings
[00018] The subsequent description of the preferred embodiments of the present invention refers to the attached drawings, wherein:
[00019] Figure 1A is a schematic of a section of heat exchange coil according to an embodiment of the invention.
[00020] Figure IB is a representation of the principles of the invention, accomplished with double-walled/double tubed straight tubes connected by single- walled/single tubed return bends. [00021] Figure 2A is a front view schematic of a heat exchanger including a heat exchange coil according to an embodiment of the invention.
[00022] Figure 2B is a side view schematic of the heat exchanger shown in Figure 2A.
[00023] Figure 3 is a front perspective drawing of a transformer air cooling unit, including a heat exchanger according to an embodiment of the invention.
[00024] Figure 4 is a rear perspective drawing of a transformer air cooling unit shown in Figure 3.
[00025] Figure 5 is another rear perspective drawing of the transformer air cooling unit shown in Figure 3.
Detailed Description of the Invention
[00026] In the following description, numerous details are set forth to provide a more thorough explanation of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details.
[00027] Figure 1 A shows a heat exchange coil 10 according to an embodiment of the invention. Heat exchange coil 10 receives fluid from header 12 through connecting tube 14. Connecting tube 14 is connected to inner tube 16a. Fluid travels through the heat exchange coil through inner tubes 16a, 16b, and 16c, via return bends 18a and 18b. Inner tubes 16a, 16b, and 16c are expanded into outer tubes 20a, 20b, and 20c, respectively. According to an embodiment of the invention, the inner surfaces of outer tubes 20a, 20b, and 20c have dimples, ribs, or other surface features 21 to create both contact between and voids between the inner and outer tubes to allow the passage of fluid between them (see Figure IB).
According to an alternative embodiment, the outer surface of the inner tubes may have spacing features or be fitted with spacing devices to accomplish the same purpose. Fins 22 are fixed to the outside surfaces of the outer tubes to enhance heat exchange. The air flow is directed only over the center portion 24 of the coil. Return bends 18a, 18b, and the ends 26 of outer tubes 20a, 20b and 20c are located outside the air flow path.
[00028] According to one method of manufacturing a coil according to the invention, outer tubes are inserted into the fin matrix and expanded into the fins. The inner tubes are then inserted into the outer tubes and expanded to provide contact at the contact surfaces and voids at non-contact locations. The return bends may then be brazed to the inner tubes.
[00029] If a leak occurs in any of inner tubes 16a, 16b, or 16c, it will be captured in corresponding outer tube 20a, 20b, or 20c, travel down the length of the tube in which it was captured by virtue of the voids created between the tubes by the inner surface features 21 of outer tubes 20a, 20b and 20c, then fall out of the end of the outer tube under force of gravity into a drip pan/drain pan 28 in return bend box 30a, 30b (Fig. 2), outside of the air flow path. In this way, the air flow path (and hence the transformer, or any other device into which the air is ultimately directed) is protected from water contamination resulting from leaks in the heat exchange coil, and leaks are quickly and easily detected, all without complicated nested and sealed chambered header arrangements. Alternatively, the space between the outer tubes and the inner tubes at one end of the coil may be brazed or otherwise sealed shut. According to this embodiment, water from leaks in the inner tubes falls out of the outer tubes only in the return bend box at the end of the coil that is opposite the end where the space between the inner and outer tubes is sealed shut.
[00030] Figures 2 A and 2B show schematics of a heat exchange unit 34 including a heat exchange coil according of the invention. Return bend boxes 30a and 30b are situated outside of the primary housing of heat exchange unit, and contain the return bends (not shown) at both ends of the inner tubes (also not shown). Fins 22 are shown, which as described above, are fixed to the outside surfaces of the outer tubes of the heat exchange coil. Header 12 includes fluid inlet/outlets 32. According to an embodiment of the invention, drain pan 28 may be provided with a slope between the return bend boxes so that water from leaks collected in one return bend box is made to travel to the other side of the coil where it can be detected with a leak detector. Alternatively, according to an embodiment of the invention where the spaces between the inner tubes and outer tubes are closed, no sloped drain pan between the return bend boxes is required, as water from any leaks will fall only into the return bend box at the end of the coil opposite the end where the spaces between the inner and outer tubes are sealed shut.
[00031] Figures 3-5 show different views of a transformer air cooling unit 36, including a heat exchanger according to an embodiment of the invention. Transformer air cooling unit 36, includes fan box 38, resting on top of heat exchange unit 34. Fans inside fan box 38 pull air from a transformer transfer unit (not shown) through louvers 39 and direct air down through heat exchange unit 34. Air passes over the tubes (not visible in Figs 3-5) and fins 22, to exit the bottom of the unit. Return bends and the ends of outer safety tubes are contained in return bend boxes 30a and 30b, outside of the air flow path, and the air flow path is preferably contained within heat exchange unit 34. Water enters one of fluid inlet/outlets 32 and exits through the other according to desired water flow valving/settings. Leak detector 40 detects the presence of water in the bottom of return bend box 30a.
[00032] The arrangement shown in Figures 3-5 should not be considered to limit the invention, and given the present disclosure, persons of ordinary skill would readily appreciate that the features of the invention described herein may be used according to any number of heat exchange applications and arrangements. The heat exchange coil of the invention can be used according to any number of arrangements where air passing over the coil must be protected from fluid contained in the coils, provided that return bends and the ends of the outer "safety" tubes are located outside of the air flow path.

Claims

1. A heat exchange coil comprising: a plurality of double-walled tubes traversing an intended air flow path, a plurality of single-walled return tubes connecting said double-walled tubes; said return bend tubes located outside of said intended air flow path.
2. A heat exchange coil according to claim 1, wherein, said double-walled tubes each comprise an inner tube and an outer tube; said inner tubes are connected to said plurality of return bend tubes to define a fluid path through said heat exchange coil; and respective ends of said outer tubes are located outside of said intended air flow path.
3. A heat exchange coil according to claim 2, further comprising surface features on inner surfaces of said outer tubes to create contact points and voids between said inner tubes and outer tubes.
4. A heat exchange coil according to claim 2, further comprising: fins fixed to said outer tubes to increase heat exchange capacity of said heat exchange coil.
5. A heat exchanger comprising a heat exchange coil according to claim 2.
6. A heat exchanger according to claim 5, further comprising return bend boxes configured to house said return bend tubes and ends of said outer tubes.
7. A heat exchanger according to claim 6, wherein at least one of said return bend boxes comprises a drip pan.
8. A heat exchanger according to claim 7, further comprising a leak detector to detect the presence of water in said drip pan.
9. A heat exchange coil according to claim 2, wherein said heat exchange coil is a marine transformer cooling coil.
10. A transformer cooling system, comprising: an air moving system for moving air over a heat exchange coil, a heat exchange coil, comprising: a plurality of double-walled tubes traversing an intended air flow path, a plurality of single-walled return tubes connecting said double-walled tubes; said return bend tubes located outside of said intended air flow path.
11. A transformer cooling system according to claim 10, wherein, said double-walled tubes each comprise an inner tube and an outer tube; said inner tubes are connected to said plurality of return bend tubes to define a fluid path through said heat exchange coil; and respective ends of said outer tubes are located outside of said intended air flow path.
12. A transformer cooling system according to claim 11, further comprising surface features on inner surfaces of said outer tubes to create contact points and voids between said inner tubes and outer tubes.
13. A transformer cooling system according to claim 11, further comprising: fins fixed to said outer tubes to increase heat exchange capacity of said heat exchange coil.
14. A transformer cooling system according to claim 11, further comprising return bend boxes configured to house said return bend tubes and ends of said outer tubes.
15. A transformer cooling system according to claim 14, further comprising a drip pan situated to collect water dripping from one or more ends of said outer tubes.
16. A transformer cooling system according to claim 14, further comprising a leak detector to detect the presence of water in said drip pan.
17. A heat exchange coil according to claim 2, wherein ends of said outer tubes at one end of said coil are sealed to outer surfaces of corresponding inner tubes so that water from leaks in said inner tubes escapes said outer tubes only at another end of said coil.
18. A transformer cooling system according to claim 11 , wherein ends of said outer tubes at one end of said coil are sealed to outer surfaces of corresponding inner tubes so that water from leaks in said inner tubes escapes said outer tubes only at another end of said coil.
EP13782020.5A 2012-04-25 2013-04-25 Double-walled dry heat exchanger coil with single-walled return bends Active EP2841863B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PL13782020T PL2841863T3 (en) 2012-04-25 2013-04-25 Double-walled dry heat exchanger coil with single-walled return bends

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201261638275P 2012-04-25 2012-04-25
PCT/US2013/038177 WO2013163400A1 (en) 2012-04-25 2013-04-25 Double-walled dry heat exchanger coil with single-walled return bends

Publications (3)

Publication Number Publication Date
EP2841863A1 true EP2841863A1 (en) 2015-03-04
EP2841863A4 EP2841863A4 (en) 2016-01-20
EP2841863B1 EP2841863B1 (en) 2022-02-09

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EP (1) EP2841863B1 (en)
DK (1) DK2841863T3 (en)
ES (1) ES2912555T3 (en)
PL (1) PL2841863T3 (en)

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2187555A (en) * 1936-12-01 1940-01-16 Gen Electric Surface cooler
US2858677A (en) * 1955-04-11 1958-11-04 Marley Co Water cooling apparatus
US3467178A (en) * 1966-12-27 1969-09-16 Trane Co Transformer cooling apparatus
US3878593A (en) * 1974-05-01 1975-04-22 Hudson Products Corp Method of manufacturing a bimetal finned tube
US4232735A (en) * 1978-05-05 1980-11-11 Kim Sung C Double-walled finned heat transfer tube
JPS58139413A (en) * 1982-02-15 1983-08-18 Toshiba Corp Foil wound transformer
JPH0878242A (en) * 1994-08-31 1996-03-22 Tada Denki Kk Double-tube cooler
DE19608049A1 (en) * 1996-03-02 1997-09-04 Behr Gmbh & Co Pipe for motor vehicle air conditioning heat transfer
JPH09310935A (en) * 1996-05-21 1997-12-02 Nippon Soken Inc Heat exchanger

Also Published As

Publication number Publication date
ES2912555T3 (en) 2022-05-26
DK2841863T3 (en) 2022-04-25
EP2841863A4 (en) 2016-01-20
EP2841863B1 (en) 2022-02-09
PL2841863T3 (en) 2022-05-30

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