US20120132402A1 - Loop heat pipe and startup method for the same - Google Patents
Loop heat pipe and startup method for the same Download PDFInfo
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- US20120132402A1 US20120132402A1 US13/323,973 US201113323973A US2012132402A1 US 20120132402 A1 US20120132402 A1 US 20120132402A1 US 201113323973 A US201113323973 A US 201113323973A US 2012132402 A1 US2012132402 A1 US 2012132402A1
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- working fluid
- evaporator
- vapor
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- condenser
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
- H01L23/42—Fillings or auxiliary members in containers or encapsulations selected or arranged to facilitate heating or cooling
- H01L23/427—Cooling by change of state, e.g. use of heat pipes
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- 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
- F28D15/02—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 in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/0266—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 in which the medium condenses and evaporates, e.g. heat pipes with separate evaporating and condensing chambers connected by at least one conduit; Loop-type heat pipes; with multiple or common evaporating or condensing chambers
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- 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
- F28D15/02—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 in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/06—Control arrangements therefor
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K7/00—Constructional details common to different types of electric apparatus
- H05K7/20—Modifications to facilitate cooling, ventilating, or heating
- H05K7/20709—Modifications to facilitate cooling, ventilating, or heating for server racks or cabinets; for data centers, e.g. 19-inch computer racks
- H05K7/208—Liquid cooling with phase change
- H05K7/20809—Liquid cooling with phase change within server blades for removing heat from heat source
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F2250/00—Arrangements for modifying the flow of the heat exchange media, e.g. flow guiding means; Particular flow patterns
- F28F2250/06—Derivation channels, e.g. bypass
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
Abstract
A loop heat pipe includes: a first evaporator and a second evaporator each of which vaporizes a liquid-phase working fluid and converts the liquid-phase working fluid to a vapor-phase working fluid; a first condenser and a second condenser each of which condenses the vapor-phase working fluid and converts the vapor-phase working fluid back to the liquid-phase working fluid; a first vapor line through which the working fluid converted to the vapor phase is transported to the first condenser; a first liquid line through which the working fluid converted to the liquid phase is transported to the second evaporator; a second vapor line through which the working fluid converted to the vapor phase is transported to the second condenser; and a second liquid line through which the working fluid converted to the liquid phase is transported to the first evaporator.
Description
- This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-164960, filed on Jul. 13, 2009, and International Patent Application PCT/JP2010/056093, filed on Apr. 2, 2010, the entire contents of which are incorporated herein by reference.
- The present invention is related to a loop heat pipe and a startup method for the same.
- Heat pipes are used for cooling electronic devices. A heat pipe is a heat transfer device that transports heat by utilizing the phase change of the working fluid sealed therein.
- In order to enhance the cooling capability for cooling electronic devices, a heat pipe known as a loop heat pile has been developed that can transport a larger heat load over a longer distance.
- The loop heat pipe includes an evaporator which receives heat from a heat source and vaporizes a liquid-phase working fluid, and a condenser which condenses the vapor-phase working fluid by giving off heat. The loop heat pipe further includes a vapor line through which the working fluid converted to the vapor phase by the evaporator is transported to the condenser, and a liquid line through which the working fluid converted to the liquid phase by the condenser is transported to the evaporator. The loop heat pipe has a loop structure in which the evaporator, the evaporator line, the condenser, and the liquid line are connected in series, and the working fluid is sealed therein.
- In recent years, a blade server of the type that has two CPUs on one blade has been developed in order to enhance the processing capability of the server.
- If two CPUs are to be cooled during operation by using a loop heat pipe, there arises a need to provide two evaporators in order to receive heat from the respective CPUs, which means that two loop heat pipes have to be incorporated into the blade server.
- In order to incorporate two loop heat pipes into the blade server, an area for accommodating the two loop heat pipes needs to be provided on the substrate.
- However, since the blade server was originally developed as a server more compact in volume than the conventional server, electronic devices including CPUs are packed at high density on the substrate.
- There are therefore cases in which it is difficult to secure an area for accommodating two loop heat pipes on the substrate.
- On the other hand, a loop heat pipe equipped with two evaporators has been proposed. A loop heat pipe of this type is depicted in
FIG. 1 . - The
loop heat pipe 110 includes afirst evaporator 111A and acondenser 112. Theloop heat pipe 110 further includes a firstliquid line 114A through which the working fluid converted to the liquid phase by thecondenser 112 is transported to thefirst evaporator 111A, and avapor line 113 through which the working fluid converted to the vapor phase by thefirst evaporator 111A is transported to thecondenser 112. - Further, as depicted in
FIG. 1 , theloop heat pipe 110 includes asecond evaporator 111B which assists in transporting the liquid-phase working fluid into thefirst evaporator 111A at the time of startup. A portion of the liquid-phase working fluid passed through the firstliquid line 114A flows into thesecond evaporator 111B through a secondliquid line 114B and through thecondenser 112. The working fluid converted to the vapor phase by thesecond evaporator 111B merges with the working fluid flowing in thevapor line 113 and is transported to thecondenser 12. The working fluid transported through the secondliquid line 114B is passed through thecondenser 12 and flows into thesecond evaporator 111B without merging with the working fluid flowing in the firstliquid line 114A. - When starting up the
loop heat pipe 110, the liquid-phase working fluid is quickly fed into thesecond evaporator 111B disposed near thecondenser 112, thus starting the circulation of the working fluid through the loop and causing the liquid-phase working fluid to flow into thefirst evaporator 111A. Thesecond evaporator 111B is an auxiliary evaporator provided to assist the startup of theloop heat pipe 110. Therefore, thesecond evaporator 111B has a smaller size and lower cooling capacity than thefirst evaporator 111A. - If such a
loop heat pipe 110 having twoevaporators evaporators - [Patent Document 1] Japanese Unexamined Patent Publication No. 2008-85112
- [Patent Document 2] U.S. Patent Application No. 2004/0182550
- According to an aspect of the embodiment disclosed in this specification to solve the above problem, there is provided a loop heat pipe which includes: a first evaporator and a second evaporator each of which vaporizes a liquid-phase working fluid by receiving heat from a heat source and thereby converts the liquid-phase working fluid to a vapor-phase working fluid; a first condenser and a second condenser each of which condenses the vapor-phase working fluid by giving off heat and thereby converts the vapor-phase working fluid back to the liquid-phase working fluid; a first vapor line through which the working fluid converted to the vapor phase by the first evaporator is transported to the first condenser; a first liquid line through which the working fluid converted to the liquid phase by the first condenser is transported to the second evaporator; a second vapor line through which the working fluid converted to the vapor phase by the second evaporator is transported to the second condenser; and a second liquid line through which the working fluid converted to the liquid phase by the second condenser is transported to the first evaporator.
- The object and advantages of the embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
- It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
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FIG. 1 is a diagram illustrating a loop heat pipe according to the related art; -
FIG. 2 is a diagram illustrating a first embodiment of a loop heat pipe disclosed in this specification; -
FIG. 3 is a diagram illustrating a blade server in which the loop heat pipe ofFIG. 2 is incorporated; -
FIG. 4 is an enlarged longitudinal cross-sectional view of an evaporator in the loop heat pipe ofFIG. 2 ; -
FIG. 5 is an enlarged lateral cross-sectional view of the evaporator in the loop heat pipe ofFIG. 2 ; -
FIGS. 6(A) to 6(D) are diagrams illustrating the operation of the loop heat pipe ofFIG. 2 ; -
FIG. 7 is a diagram illustrating how the amount of received heat becomes unbalanced; -
FIG. 8 is a diagram illustrating a second embodiment of the loop heat pipe disclosed in this specification; -
FIGS. 9(A) to 9(D) are diagrams illustrating the operation of the loop heat pipe ofFIG. 8 ; -
FIG. 10 is a diagram illustrating a third embodiment of the loop heat pipe disclosed in this specification; -
FIG. 11 is a diagram illustrating a blade server in which a fourth embodiment of the loop heat pipe disclosed in this specification is incorporated; -
FIG. 12 is a diagram illustrating Working Examples 1 to 14 of the loop heat pipe disclosed in this specification; -
FIG. 13 is a diagram illustrating Working Example 15 of the loop heat pipe disclosed in this specification; -
FIG. 14 is a diagram illustrating Working Example 16 of the loop heat pipe disclosed in this specification; -
FIG. 15 is a diagram illustrating Working Example 17 of the loop heat pipe disclosed in this specification; and -
FIG. 16 is a diagram illustrating Working Example 18 of the loop heat pipe disclosed in this specification. - A first preferred embodiment of a loop heat pipe disclosed in this specification will be described below with reference to drawings. It will, however, be noted that the technical scope of the present invention is not limited to the specific embodiments disclosed herein, but extends to the inventions described in the appended claims and their equivalents.
-
FIG. 2 is a diagram illustrating the first embodiment of the loop heat pipe disclosed in this specification.FIG. 3 is a diagram illustrating a blade server in which the loop heat pipe ofFIG. 2 is incorporated.FIG. 4 is an enlarged longitudinal cross-sectional view of an evaporator in the loop heat pipe ofFIG. 2 .FIG. 5 is an enlarged lateral cross-sectional view of the evaporator in the loop heat pipe ofFIG. 2 . - As illustrated in
FIG. 2 , theloop heat pipe 10 of the present embodiment includes afirst evaporator 11A and asecond evaporator 11B each of which vaporizes a liquid-phase working fluid 16 by receiving heat from a heat source and thereby converts the liquid-phase working fluid 16 to a vapor-phase working fluid 16. Theloop heat pipe 10 further includes afirst condenser 12A and asecond condenser 12B each of which condenses the vapor-phase working fluid 16 by giving off heat and thereby converts the vapor-phase working fluid 16 back to the liquid-phase working fluid 16. Further, theloop heat pipe 10 includes afirst vapor line 13A through which the workingfluid 16 converted to the vapor phase by thefirst evaporator 11A is transported to thefirst condenser 12A, and a firstliquid line 14A through which the workingfluid 16 converted to the liquid phase by thefirst condenser 12A is transported to thesecond evaporator 11B. Furthermore, theloop heat pipe 10 includes asecond vapor line 13B through which the workingfluid 16 converted to the vapor phase by thesecond evaporator 11B is transported to thesecond condenser 12B, and a secondliquid line 14B through which the workingfluid 16 converted to the liquid phase by thesecond condenser 12B is transported to thefirst evaporator 11A. - In the
loop heat pipe 10, a loop flow passage is formed by connecting in series thefirst evaporator 11A, thefirst vapor line 13A, thefirst condenser 12A, the firstliquid line 14A, thesecond evaporator 11B, thesecond vapor line 13B, thesecond condenser 12B, and the secondliquid line 14B. - The working fluid is hermetically sealed in the loop flow passage. The working
fluid 16 transports heat while undergoing a phase change between the liquid phase and the vapor phase in theloop heat pipe 10. The workingfluid 16 is hermetically sealed in theloop heat pipe 10 at saturated vapor pressure. - As the working
fluid 16, for example, water, alcohol, ammonia, fluorocarbon, or the like, may be used. - In use, the
loop heat pipe 10 is incorporated, for example, in ablade server 20, as illustrated inFIG. 3 . - The
blade server 20 is equipped with twoCPUs first evaporator 11A of theloop heat pipe 10 is disposed in thermal contact with theCPU 21A. Thesecond evaporator 11B is disposed in thermal contact with theCPU 21B. - In many cases, the
blade server 20 has an elongated rectangular shape as depicted inFIG. 3 . Theblade server 20 is usually oriented in such a manner that its width direction extending at right angles to its longitudinal direction coincides with the plumbline direction. Typically, theCPU 21A is located upwardly of theCPU 21B, as viewed along the plumbline direction. - Accordingly, in the
loop heat pipe 10, thefirst evaporator 11A that receives heat from theCPU 21A is located upwardly of thesecond evaporator 11B that receives heat from theCPU 21B, as viewed along the plumbline direction. - A
main fan 22 delivers air to the first andsecond condensers - While
FIG. 3 has depicted an example in which theloop heat pipe 10 is incorporated in the blade server, theloop heat pipe 10 may be incorporated in other electronic apparatus having a heat source to be cooled. - Next, the
first evaporator 11A will be described in further detail below with reference toFIGS. 4 and 5 . Since thesecond evaporator 11B is identical in structure to thefirst evaporator 11A, the description hereinafter given of thefirst evaporator 11A applies as well to thesecond evaporator 11B. - As illustrated in
FIG. 4 , thefirst evaporator 11A has a longitudinally extending shape. The longitudinal direction of thefirst evaporator 11A coincides with the direction in which the workingfluid 16 flows through the flow passage of theloop heat pipe 10. InFIG. 4 , the flow direction of the workingfluid 16 is indicated by arrows. - As illustrated in
FIGS. 4 and 5 , thefirst evaporator 11A includes alongitudinally extending housing 30, ametal block 31 centrally located within thehousing 30, ametal tube 32 located in a hollow space within themetal block 31, and awick 33 located within themetal tube 32. - The
housing 30, themetal block 31, and themetal tube 32 are each formed from a metal having high thermal conductivity such as copper. - The longitudinal direction of the
housing 30 coincides with the longitudinal direction of thefirst evaporator 11A. The secondliquid line 14B is connected to one longitudinal end of thehousing 30. Thefirst vapor line 13A is connected to the other longitudinal end of thehousing 30. - The heat source such as the
CPU 21A is thermally coupled to thehousing 30 by means of a thermal bonding material such as thermal grease (not depicted). - The
metal block 31 is in intimate contact with the inner surface of thehousing 30 and is thus thermally coupled to thehousing 30. Themetal block 31 has a cylindrically shaped hollow core. The longitudinal direction of the hollow core coincides with the longitudinal direction of thefirst evaporator 11A. Themetal block 31 quickly conducts the heat, received from theheat source 21A via thehousing 30, to themetal tube 32 located in the hollow core. - The
metal tube 32 has a longitudinally elongated cylindrical shape. Themetal tube 32 is located in the hollow core of themetal block 31. The longitudinal direction of themetal tube 32 coincides with the longitudinal direction of thefirst evaporator 11A. The outer surface of themetal tube 32 is in intimate contact with the inner surface of the hollow core of themetal block 31, and thus themetal tube 32 is thermally coupled to themetal block 31. - As illustrated in
FIG. 5 , a plurality ofprojections 34 a anddepressions 34 b are formed on the inner surface of themetal tube 32 at a prescribed pitch in the circumferential direction thereof. Theprojections 34 a anddepressions 34 b are formed along the entire longitudinal direction of themetal tube 32. The groove-like space formed between thewick 33 and thedepressions 34 b provides a passage for the workingfluid 16. - The
wick 33 has a longitudinally elongated cylindrical shape, as depicted inFIG. 4 . Thewick 33 is open at one end thereof that faces the secondliquid line 14B and closed at the other end thereof that faces thefirst vapor line 13A. - The
wick 33 is inserted in themetal tube 32 with its closed end facing toward thefirst vapor line 13A. As illustrated inFIG. 5 , the outer surface of thewick 33 contacts the tips of the plurality ofprojections 34 a formed on the inner surface of themetal tube 32, and thus thewick 33 is thermally coupled to themetal tube 32. - The
wick 33 is formed of a porous material. For example, thewick 33 is constructed from a porous member formed by sintering copper powder. Preferably, the hollow interior space of thewick 33 is made to communicate with the exterior thereof by means of numerous fine pores of diameters about 10 μm to 50 μm. - When the liquid-
phase working fluid 16 flows into thefirst evaporator 11A from the secondliquid line 14B, the workingfluid 16 infiltrates into thewick 33 by capillary action, and thewick 33 is thus wetted with the workingfluid 16. The liquid-phase working fluid 16 infiltrated into thewick 33 is heated and vaporized by the heat received from the heat source such as theCPU 21A. - The vapor-
phase working fluid 16 existing in thewick 33 itself or on its surface or in the hollow interior space of thewick 33 is vented from the hollow interior space to the outside through the fine pores formed in thewick 33. - The
housing 30 of thefirst evaporator 11A having the above structure may be chosen to have dimensions measuring 50 mm vertically, 50 mm horizontally, and 20 mm in height, compared with the CPU as the heat source which measures, for example, 30 mm vertically and 30 mm horizontally. Themetal block 31 may be chosen to have dimensions measuring 40 mm vertically, 40 mm horizontally, and 20 mm in height. Themetal tube 32 may be chosen to have an outer diameter of 14 mm and an inner diameter of 10 mm (tube wall thickness of 2 mm). Thedepressions 34 b ofdepth 1 mm are formed in the inner surface of themetal tube 32, for example, at a pitch of 2 mm. Thewick 33 may be chosen to have an outer diameter of 10 mm and an inner diameter of 4 mm. - Next, the
first condenser 12A will be described in further detail below with reference toFIGS. 2 and 3 . Since thesecond condenser 12B is identical in structure to thefirst condenser 12A, the description hereinafter given of thefirst condenser 12A applies as well to thesecond condenser 12B. - As depicted in
FIG. 2 , thefirst condenser 12A includes afirst condenser line 40A and a plurality of firstheat sinking plates 41A coupled to thefirst condenser line 40A. - The
first vapor line 13A is connected to one end of thefirst condenser line 40A. The firstliquid line 14A is connected to the other end of thefirst condenser line 40A. - The plurality of first
heat sinking plates 41A are thermally coupled to thefirst condenser line 40A, and the heat of the workingfluid 16 passing through thefirst condenser line 40A is dissipated via the plurality of firstheat sinking plates 41A. - As depicted in
FIG. 3 , it is preferable to blow air over the plurality of firstheat sinking plates 41A of thefirst condenser 12A by means of themain fan 22 or the like in order to dissipate heat and facilitate the phase change of the workingfluid 16 from the vapor phase to the liquid phase. - Next, the
first vapor line 13A will be described in further detail below with reference toFIGS. 2 and 3 . Since thesecond vapor line 13B is identical in structure to thefirst vapor line 13A, the description hereinafter given of thefirst vapor line 13A applies as well to thesecond vapor line 13B. - One end of the
first vapor line 13A is connected to thefirst evaporator 11A. The other end of thefirst vapor line 13A is connected to thefirst condenser 12A. - All of the working
fluid 16 flowing in thefirst vapor line 13A is not necessarily in vapor phase. Depending on the operating conditions or installation environment of theloop heat pipe 10, the workingfluid 16 may turn into liquid phase during passage between thefirst evaporator 11A and thefirst condenser 12A, so that the workingfluid 16 partly in liquid phase and partly in vapor phase may flow in thefirst vapor line 13A. - The
first vapor line 13A is formed from a metal having high thermal conductivity such as copper. - Next, the first
liquid line 14A will be described in further detail below with reference toFIGS. 2 and 3 . Since the secondliquid line 14B is identical in structure to the firstliquid line 14A, the description hereinafter given of the firstliquid line 14A applies as well to the secondliquid line 14B. - One end of the first
liquid line 14A is connected to thefirst condenser 12A. The other end of the firstliquid line 14A is connected to thesecond evaporator 11B. - All of the working
fluid 16 flowing in the firstliquid line 14A is not necessarily in liquid phase. Depending on the operating conditions or installation environment of theloop heat pipe 10, the workingfluid 16 may turn into vapor phase during passage between thefirst condenser 12A and thesecond evaporator 11B, so that the workingfluid 16 partly in liquid phase and partly in vapor phase may flow in the firstliquid line 14A. - The first
liquid line 14A is formed from a metal having high thermal conductivity such as copper. - The working
fluid 16 is sealed in theloop heat pipe 10 preferably in such an amount that the liquid-phase working fluid 16 fills thefirst evaporator 11A, the secondliquid line 14B, thesecond evaporator 11B, and the firstliquid line 14A. Also preferably, the volume of this workingfluid 16 is a little larger than one half of the volume of the flow passage in theloop heat pipe 10. If the volume of the workingfluid 16 is larger than this specific volume, the flow resistance increases, and the thermal resistance thus increases. On the other hand, if the volume of the workingfluid 16 is smaller than this specific volume, the operation of theloop heat pipe 10 may become unstable. - Next, the operation of the
loop heat pipe 10 will be described below with reference toFIGS. 6(A) to 6(D) .FIGS. 6(A) to 6(D) are diagrams illustrating the operation of the loop heat pipe. - First, as illustrated in
FIG. 6(A) , in theloop heat pipe 10, thefirst evaporator 11A is located upwardly of thesecond evaporator 11B, as viewed along the plumbline direction. Accordingly, in the pre-startup stage, the liquid-phase working fluid 16 is collected in the lower part of theloop heat pipe 10, and the inside of thesecond evaporator 11B is filled with the liquid-phase working fluid 16. The fine pores of thewick 33 inside thesecond evaporator 11B are thus impregnated with the liquid-phase working fluid 16. - The upper part of the
loop heat pipe 10 is filled with the vapor-phase working fluid 16. Accordingly, the inside of thefirst evaporator 11A is filled with the vapor-phase working fluid 16. That is, thewick 33 inside thefirst evaporator 11A is in a dry condition, and thefirst evaporator 11A is thus in the so-called dry-out condition. - When starting up the
loop heat pipe 10, first thesecond evaporator 11B is started to receive heat. In the example illustrated inFIG. 3 , only theCPU 21B is put into operation, and thesecond evaporator 11B begins to receives heat from theCPU 21B which is the heat source. - The
first evaporator 11A is started to receive heat after a predetermined length of time has elapsed from the time thesecond evaporator 11B began to receive heat. This predetermined length of time is determined based on the time taken for the liquid-phase working fluid 16 to begin to flow into thefirst evaporator 11A. - In the
second evaporator 11B that received heat from the heat source, first thehousing 30 is heated by the heat from the heat source, and the heat thus applied to thehousing 30 is transferred to themetal block 31. The heat transferred to themetal block 31 is then transferred to themetal tube 32, and the heat transferred to themetal tube 32 is further transferred via theprojections 34 a of themetal tube 32 to thewick 33 which is thus heated. - When the temperature of the
wick 33 rises as it is heated, the liquid-phase working fluid 16 filled into the fine pores of thewick 33 boils and vaporizes. Since the pressure inside the fine pores increases as the workingfluid 16 in the fine pores of thewick 33 turns into vapor phase, the vapor-phase working fluid 16 is forced out onto the outer surface of thewick 33. - The vapor-
phase working fluid 16 forced out onto the outer surface of thewick 33 passes, for example, through the space formed by thedepressions 34 b of themetal tube 32 and flows into the interior space of thehousing 30 on thesecond evaporator 13B side. The vapor-phase working fluid 16 then flows into thesecond vapor line 13B. - In the operating condition after the startup of the
loop heat pipe 10, some of the vapor-phase working fluid 16 may remain inside themetal tube 32 of thesecond evaporator 11B. This vapor-phase working fluid 16 is also forced out onto the outer surface of thewick 33 as the pressure increases due to the vaporization of the workingfluid 16. - Next, as illustrated in
FIG. 6(B) , as the pressure rises inside thehousing 30 of thesecond evaporator 11B, the liquid-phase working fluid 16 remaining in thesecond evaporator line 13B is forced into thesecond condenser 12B. The liquid-phase working fluid 16 is further forced from thesecond condenser 12B into the secondliquid line 14B, and the fluid level in the secondliquid line 14B thus rises. - Then, the vapor-
phase working fluid 16 pushed by the liquid-phase working fluid 16 is forced to pass through thefirst evaporator 11A and then through thefirst vapor line 13A, and finally flows into thefirst condenser 12A. The vapor-phase working fluid 16 flowing into thefirst condenser 12A is condensed by giving off heat and changes to the liquid phase. The heat contained in the workingfluid 16 is transferred via thefirst condenser line 40A to the firstheat sinking plates 41A from which the heat is dissipated. - In this way, in the
first condenser 12A, the vapor-phase working fluid 16 is cooled, and all or part of it changes to the liquid phase. As a result, the liquid-phase working fluid 16 accumulates in thefirst condenser 12A and thefirst vapor line 13A, and the fluid level thus rises. - Next, as illustrated in
FIG. 6(C) , the liquid-phase working fluid 16 forced into the secondliquid line 14B by being pushed from thesecond condenser 12B side begins to flow into thefirst evaporator 11A. - At this point in time, the
first evaporator 11A starts to receive heat. For example, as illustrated inFIG. 3 , theCPU 21A is put into operation, and thefirst evaporator 11A begins to receive heat from theCPU 21A which is the heat source. - The liquid-
phase working fluid 16 flowing into thefirst evaporator 11A changes to the vapor phase, and the vapor-phase working fluid 16 flows into thefirst vapor line 13A. - Next, as illustrated in
FIG. 6(D) , the interior space of thewick 33 in thefirst evaporator 11A is substantially filled with the liquid-phase working fluid 16, and the operation of theloop heat pipe 10 thus becomes stable. When the operation of theloop heat pipe 10 becomes stable, thefirst evaporator 11A, thesecond evaporator 11B, the firstliquid line 14A, and the secondliquid line 14B are substantially filled with the liquid-phase working fluid 16. The other portions of theloop heat pipe 10 are filled with the vapor-phase working fluid 16. - In this way, the two heat sources are cooled stably by the
loop heat pipe 10. - According to the
loop heat pipe 10 described above, since the loop heat pipe is constructed from a single loop flow passage, the overall dimensions of the structure can be reduced. Furthermore, because of the provision of two evaporators, theloop heat pipe 10 can cool two heat sources. - According to the startup method of the
loop heat pipe 10 described above, since the evaporator filled with the liquid-phase working fluid 16 is first started to receive heat, theloop heat pipe 10 can be started up in a reliable manner. - For example, in the case of a blade server equipped with two CPUs, if the two CPUs can both be mounted in the lower part of the substrate (lower as viewed along the plumbline direction), the two evaporators can both be filled with the liquid-phase working fluid at the time of the loop heat pipe startup. However, such an arrangement greatly constrains the blade server construction, and is therefore difficult to implement in practice.
- Further, in the case of a blade server equipped with two CPUs, the two CPUs are often mounted in different positions as viewed along the plumbline direction. In this case, if different loop heat pipes are provided for the two respective CPUs, the evaporator thermally coupled to the CPU mounted in the upper position as viewed along the plumbline direction may not be able to be filled with the liquid-phase working fluid at the time of startup. If the loop heat pipe is to be started up with no liquid-phase working fluid in the evaporator, the loop heat pipe will not start up because the evaporator is in the dry-out condition and is therefore unable to cause the liquid-phase working fluid to change to the vapor phase.
- By contrast, according to the
loop heat pipe 10 described above, since two evaporators are provided within a single loop, the evaporator located in the lower part as viewed along the plumbline direction can be easily filled with the liquid-phase working fluid at the time of startup. Further, according to the loop heat pipe startup method described above, the evaporator located in the lower part as viewed along the plumbline direction is first started to receive heat, and after the liquid-phase working fluid has begun to flow into the evaporator located in the upper part as viewed along the plumbline direction, the evaporator located in the upper part is started to receive heat. In this way, theloop heat pipe 10 can be started up in a reliable manner. - The
loop heat pipe 10 described above operates stably when the amount of received heat is equal between thefirst evaporator 11A and thesecond evaporator 11B. However, if the amount of received heat is not equal between thefirst evaporator 11A and thesecond evaporator 11B, the amount of the workingfluid 16 that changes from liquid phase to vapor phase becomes different between thefirst evaporator 11A and thesecond evaporator 11B; as a result, the distribution of the workingfluid 16 in the flow passage becomes uneven, and the circulation of the workingfluid 16 may become unstable or may stop. - An example of this will be described with reference to
FIG. 7 .FIG. 7 is a diagram illustrating how the amount of received heat becomes unbalanced. - In the
loop heat pipe 10 depicted inFIG. 7 , the amount of received heat in thefirst evaporator 11A has increased, and on the other hand, the amount of received heat in thesecond evaporator 11B has decreased, resulting in a situation where the amount of received heat is unbalanced. In the example of the blade server depicted inFIG. 3 , this corresponds to the situation where the usage rate of theCPU 21A has increased and its temperature has risen, while the usage rate of theCPU 21B has decreased and its temperature has decreased. - In the
loop heat pipe 10, the vaporization rate of the workingfluid 16 is higher in thefirst evaporator 11A where the amount of received heat has increased than in thesecond evaporator 11B where the amount of received heat has decreased. - As a result, the amount of the liquid-
phase working fluid 16 in the secondliquid line 14B decreases, while the amount of the liquid-phase working fluid 16 in the firstliquid line 14A increases.FIG. 7 shows the condition in which the fluid level of the liquid-phase working fluid 16 has risen into thefirst vapor line 13A. - If this condition further continues, the
first evaporator 11A eventually runs out of the liquid-phase working fluid 16 and is forced into the dry-out condition, and the circulation of the workingfluid 16 stops. - Such a phenomenon tends to occur, in particular, when the flow resistance of the working
fluid 16 is relatively large, for example, when the distance between the evaporator and the condenser is large or when the evaporator is located in a position lower than the condenser. - It is therefore preferable to design the loop heat pipe so that it can operate stably even when the amount of received heat becomes unbalanced between the two evaporators.
- In view of the above, loop heat pipes according to second to fourth embodiments will be described below with reference to drawings as examples of the loop heat pipe that can operate stably even when the amount of received heat becomes unbalanced between the two evaporators. The detailed description of the first embodiment given above essentially applies to those parts of the second to fourth embodiments that are not specifically described herein. Further, in
FIGS. 8 to 11 , the same component elements as those inFIGS. 2 to 7 are designated by the same reference numerals. -
FIG. 8 is a diagram illustrating theloop heat pipe 50 of the second embodiment disclosed in this specification. - The
loop heat pipe 50 includes abypass line 15 which connects between thefirst vapor line 13A and thesecond vapor line 13B. Thebypass line 15 has the function of diverting the flow of the workingfluid 16 and thereby bringing theloop heat pipe 50 back into the stable operating condition when the distribution of the workingfluid 16 in the flow passage has become uneven because, for example, the amount of received heat has become unbalanced between the two evaporators. - It is preferable for the
bypass line 15 to be provided so as to connect between a portion of thefirst vapor line 13A in the vicinity of thefirst condenser 12A and a portion of thesecond vapor line 13B in the vicinity of thesecond condenser 12B. For example, it is preferable for thebypass line 15 to connect between the portion of thefirst vapor line 13A that is located 1 to 3 cm away from thefirst condenser 12A and the portion of thesecond vapor line 13B that is located 1 to 3 cm away from thesecond condenser 12B. - Preferably, the cross-sectional area of the section of the
bypass line 15 through which the workingfluid 16 passes is not larger than the cross-sectional area of the section of thefirst vapor line 13A or thesecond vapor line 13B through which the workingfluid 16 passes. Also preferably, the pressure'loss of the workingfluid 16 in thebypass line 15 is larger than that in the liquid line or the vapor line. - The reason is that the flow resistance of the working
fluid 16 through thebypass line 15 needs to be increased to prevent the workingfluid 16 from easily flowing into thebypass line 15 when theloop heat pipe 50 is operating stably. - Next, a description will be given of the preferred relationship between the cross-sectional area of the fluid flow section of the
bypass line 15 and the cross-sectional area of the fluid flow section of thefirst vapor line 13A or thesecond vapor line 13B. - That is, the ratio of the cross-sectional area of the fluid flow section of the
bypass line 15 to the cross-sectional area of the fluid flow section of thefirst vapor line 13A or thesecond vapor line 13B is preferably in the range of 0.1 to 1, and more preferably in the range of 0.4 to 0.6. - The cross-sectional area ratio of 0.1 or larger is preferable from the standpoint of quickly diverting the flow of the working
fluid 16 and bringing the loop heat pipe back into the stable operating condition when the distribution of the workingfluid 16 in the flow passage has become uneven. If the cross-sectional area ratio is smaller than 0.1, the pressure loss through thebypass line 15 becomes too large, and the flow of the workingfluid 16 through thebypass line 15 is impeded. - On the other hand, the cross-sectional area ratio of 1 or smaller is preferable from the standpoint of preventing the working
fluid 16 from preferentially flowing into thebypass line 15 when theloop heat pipe 50 is operating stably. Further, when the cross-sectional area ratio is 1 or smaller, the liquid-phase working fluid 16 can be caused to flow into thebypass line 15 by utilizing capillary forces. - The length of the
bypass line 15 is suitably chosen according to the configuration of theloop heat pipe 50. - The
bypass line 15 may be provided with a loop section, a bent section, etc. in order to increase the pressure loss of the workingfluid 16. - The structure of the other portions of the
loop heat pipe 50 is the same as that of the foregoing first embodiment. - Next, the operation of the
loop heat pipe 50 will be described below with reference toFIGS. 9(A) to 9(D) .FIGS. 9(A) to 9(D) are diagrams illustrating the operation of theloop heat pipe 50. - First, in
FIG. 9(A) , theloop heat pipe 50 is operating in a stable condition. The process from the time theloop heat pipe 50 is started up until it reaches the stable operating condition is the same as that described in the first embodiment. - Next, suppose that the amount of received heat in the
first evaporator 11A has increased and the amount of received heat in thesecond evaporator 11B has decreased, thus putting theloop heat pipe 50 in a situation where the amount of received heat is unbalanced, as illustrated inFIG. 9(B) . - In the
loop heat pipe 50, the vaporization rate of the workingfluid 16 is higher in thefirst evaporator 11A where the amount of received heat has increased than in thesecond evaporator 11B where the amount of received heat has decreased. - As a result, the amount of the liquid-
phase working fluid 16 in the secondliquid line 14B decreases. Here, since the amount of the workingfluid 16 in the flow passage is constant, the amount of the liquid-phase working fluid 16 in the firstliquid line 14A increases.FIG. 9(B) shows the condition in which the fluid level of the liquid-phase working fluid 16 has risen into thefirst condenser 12A. - As a result, the pressure of the vapor phase portion of the working
fluid 16 in the secondliquid line 14B decreases, while the pressure in thefirst vapor line 13A increases. As the pressure in the secondliquid line 14B decreases, the pressure in thesecond condenser 12B as well as the pressure in thesecond vapor line 13B decreases. - Thereupon, the vapor-
phase working fluid 16 in thefirst vapor line 13A flows through thebypass line 15 into thesecond vapor line 13B. The workingfluid 16 flowing into thesecond vapor line 13B enters thesecond condenser 12B where it is converted to the liquid-phase working fluid 16 which then flows into the secondliquid line 14B. If any liquid-phase working fluid 16 exists in thefirst vapor line 13A, the liquid-phase working fluid 16 may also flow into thebypass line 15. - As a result, the amount of the liquid-
phase working fluid 16 in the secondliquid line 14B increases, while the amount of the liquid-phase working fluid 16 in the firstliquid line 14A decreases. In this way, the distribution of the workingfluid 16 in theloop heat pipe 50 is automatically brought back to the condition illustrated inFIG. 9(A) . Theloop heat pipe 50 is thus restored to the stable operating condition. - However, if the rate of increase in the amount of received heat in the
first evaporator 11A and the rate of decrease in the amount of received heat in thesecond evaporator 11B are large, the amount of received heat becomes further unbalanced, and the distribution of the workingfluid 16 in theloop heat pipe 50 changes to the condition illustrated inFIG. 9(C) . -
FIG. 9(C) illustrates the condition in which the amount of the liquid-phase working fluid 16 in the secondliquid line 14B has further decreased and the amount of the liquid-phase working fluid 16 in the firstliquid line 14A has further increased. In the condition illustrated inFIG. 9(C) , the fluid level of the liquid-phase working fluid 16 has risen into thefirst vapor line 13A. - When the fluid level of the working
fluid 16 thereafter reaches the portion connected to thebypass line 15, the liquid-phase working fluid 16 in thefirst vapor line 13A flows through thebypass line 15 into thesecond vapor line 13B due to the pressure difference and capillary forces, as illustrated inFIG. 9(D) . - The working
fluid 16 flowing into thesecond vapor line 13B is passed through thesecond condenser 12B and flows into the secondliquid line 14B. - As a result, the amount of the liquid-
phase working fluid 16 in the secondliquid line 14B increases, while the amount of the liquid-phase working fluid 16 in the firstliquid line 14A decreases. In this way, the distribution of the workingfluid 16 in theloop heat pipe 50 is automatically brought back to the condition illustrated inFIG. 9(A) . Theloop heat pipe 50 is thus restored to the stable operating condition. - The operation of the
loop heat pipe 50 has been described above by taking as an example the case where the amount of received heat in thefirst evaporator 11A increases and the amount of received heat in thesecond evaporator 11B decreases. However, when the amount of received heat increases only in thefirst evaporator 11A and the amount of received heat remains unchanged in thesecond evaporator 11B, or when the amount of received heat remains unchanged in thefirst evaporator 11A but the amount of received heat decreases in thesecond evaporator 11B, theloop heat pipe 50 can also be restored to the stable operating condition. - In this way, when a relative change occurs in the amount of received heat between the
first evaporator 11A and thesecond evaporator 11B, the distribution of the workingfluid 16 in the flow passage is brought back to the normal condition, and theloop heat pipe 50 is thus restored to the stable operating condition. - Further, when a relative change occurs in cooling capability between the
first condenser 12A and thesecond condenser 12B, the distribution of the workingfluid 16 in the flow passage is also brought back to the normal condition, and theloop heat pipe 50 is thus restored to the stable operating condition. - According to the
loop heat pipe 50 described above, when the distribution of the workingfluid 16 in the flow passage becomes uneven, the workingfluid 16 is caused to flow from thefirst vapor line 13A to thesecond vapor line 13B through thebypass line 15, so that theloop heat pipe 50 can be restored to the stable operating condition. - Accordingly, even when the amount of received heat becomes unbalanced between the two evaporators, the
loop heat pipe 50 can be made to operate stably. - Furthermore, since any uneven distribution of the working
fluid 16 occurring in the flow passage can be resolved without using external energy such as electric power, theloop heat pipe 50 is of an energy saving design. - Next, the loop heat pipe of the third embodiment will be described below with reference to
FIG. 10 .FIG. 10 is a diagram illustrating theloop heat pipe 60 of the third embodiment disclosed in this specification. - In the
loop heat pipe 60, thefirst evaporator 11A and thesecond evaporator 11B are differently sized. For example, thesecond evaporator 11B may be made two times as long as thefirst evaporator 11A. - The
loop heat pipe 60 can be used to cool two heat sources having different heat loads. Theloop heat pipe 60 can also be used to cool two heat sources having different sizes. - For example, the
loop heat pipe 60 can be used to cool a CPU and a chip controller mounted in a server. - Generally, the CPU has a larger size and a larger heat load that the chip controller.
- The
metal block 31 in thefirst evaporator 11A may be chosen to have dimensions measuring 30 mm vertically, 30 mm horizontally, and 20 mm in height, compared with the chip controller as one heat source which measures, for example, 20 mm vertically and 20 mm horizontally. On the other hand, themetal block 31 in thesecond evaporator 11B may be chosen to have dimensions measuring 50 mm vertically, 50 mm horizontally, and 20 mm in height, compared with the CPU as the other heat source which measures, for example, 30 mm vertically and 30 mm horizontally. - The structure of the other portions of the
loop heat pipe 60 is the same as that of the foregoing second embodiment. - According to the
loop heat pipe 60 described above, the heat sources can be efficiently cooled by using the evaporators each designed to match the size and heat load of the heat source to be cooled. - Next, the loop heat pipe of the fourth embodiment will be described below with reference to
FIG. 11 .FIG. 11 is a diagram illustrating ablade server 80 in which theloop heat pipe 70 of the fourth embodiment disclosed in this specification is incorporated. - In the
loop heat pipe 70, the first and second condensers are constructed in integral fashion, as illustrated inFIG. 11 . - More specifically, a plurality of
heat sinking plates 41 are coupled in common to both thefirst condenser line 40A in the first condenser and thesecond condenser line 40B in the second condenser. - The structure of the other portions of the
loop heat pipe 70 is the same as that of the earlier described second embodiment. - According to the
loop heat pipe 70 described above, the overall dimensions can be further reduced because the first and second condensers are constructed in integral fashion. - In the present embodiment, the loop heat pipe of each of the above embodiments and its startup method can be modified in various ways without departing from the spirit and purpose of the present invention.
- For example, while the
first evaporator 11A has been described in each of the above embodiments as being disposed upwardly of thesecond evaporator 11B as viewed along the plumbline direction, thesecond evaporator 11B may be disposed upwardly of thefirst evaporator 11A as viewed along the plumbline direction. - In this case, if it is not possible to identify, at the time of manufacture of the loop heat pipe, the plumbline direction by reference to which the
loop heat pipe 10 is to be oriented for use, a component element such as described below may be provided. 1. An acceleration sensor is attached to theloop heat pipe 10 so that the plumbline direction can be identified. 2. Upon startup of theloop heat pipe 10, the temperatures of the two heat sources such as CPUs are monitored, and the heat source whose temperature rise is larger is identified. Then, power supply to the heat source whose temperature rise is larger is slowed down for a prescribed period of time, to provide a startup time difference between the two heat sources. By providing such a component element, the evaporator located in the lower part as viewed along the plumbline direction can be started to receive heat earlier than the other. - In each of the above embodiments, the
first vapor line 13A, thesecond vapor line 13B, the firstliquid line 14A, and the secondliquid line 14B have been described as having the same diameter, but each line may have a different diameter. - Each of the above embodiments has been described based on the schematically illustrated loop heat pipe, and it will be recognized that each component element is not limited in its structure, arrangement, configuration, etc. to the specific example illustrated herein. For example, the arrangement of the evaporators or condensers and the configuration (layout) of the vapor lines and liquid lines connecting between them can be modified as desired according to the internal configuration of the electronic device in which the loop heat pipe is to be incorporated. Further, other component elements such as startup radiating fins or a startup fan may be provided as desired according to the arrangement and configuration of the evaporators, condensers, vapor lines, or liquid lines.
- Next, the operation and effect of the loop heat pipe disclosed in this specification will be further described below with reference to working examples. However, the present invention is not limited by the working examples described herein.
- First, a loop heat pipe of the structure depicted in
FIG. 8 was fabricated. Then, the loop heat pipe was assembled into a blade server such as depicted inFIG. 3 . The blade server was set with its substrate surface oriented perpendicularly to the plumbline direction so that the two evaporators were arranged in a horizontal plane. The heat load of the CPU A whose heat was to be transferred to the first evaporator was 0 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator was 60 W; the loop heat pipe thus fabricated was taken as Working Example 1. - Working Example 2 was fabricated in the same manner as Working Example 1, except that the heat load of the CPU A whose heat was to be transferred to the first evaporator was 20 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator was 60 W.
- Working Example 3 was fabricated in the same manner as Working Example 1, except that the heat load of the CPU A whose heat was to be transferred to the first evaporator was 40 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator was 60 W.
- Working Example 4 was fabricated in the same manner as Working Example 1, except that the heat load of the CPU A whose heat was to be transferred to the first evaporator was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator was 60 W.
- Working Example 5 was fabricated in the same manner as Working Example 1, except that the heat load of the CPU A whose heat was to be transferred to the first evaporator was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator was 40 W.
- Working Example 6 was fabricated in the same manner as Working Example 1, except that the heat load of the CPU A whose heat was to be transferred to the first evaporator was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator was 20 W.
- Working Example 7 was fabricated in the same manner as Working Example 1, except that the heat load of the CPU A whose heat was to be transferred to the first evaporator was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator was 0 W.
- The blade server was set with its substrate surface oriented in parallel to the plumbline direction so that the two evaporators were arranged in a vertical plane. Further, the heat load of the CPU A whose heat was to be transferred to the first evaporator located in the upper part as viewed along the plumbline direction was 0 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator located in the lower part as viewed along the plumbline direction was 60 W. Otherwise, Working Example 8 was fabricated in the same manner as Working Example 1.
- The heat load of the CPU A whose heat was to be transferred to the first evaporator located in the upper part as viewed along the plumbline direction was 20 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator located in the lower part as viewed along the plumbline direction was 60 W. Otherwise, Working Example 9 was fabricated in the same manner as Working Example 8.
- The heat load of the CPU A whose heat was to be transferred to the first evaporator located in the upper part as viewed along the plumbline direction was 40 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator located in the lower part as viewed along the plumbline direction was 60 W. Otherwise, Working Example 10 was fabricated in the same manner as Working Example 8.
- The heat load of the CPU A whose heat was to be transferred to the first evaporator located in the upper part as viewed along the plumbline direction was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator located in the lower part as viewed along the plumbline direction was 60 W. Otherwise, Working Example 11 was fabricated in the same manner as Working Example 8.
- The heat load of the CPU A whose heat was to be transferred to the first evaporator located in the upper part as viewed along the plumbline direction was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator located in the lower part as viewed along the plumbline direction was 40 W. Otherwise, Working Example 12 was fabricated in the same manner as Working Example 8.
- The heat load of the CPU A whose heat was to be transferred to the first evaporator located in the upper part as viewed along the plumbline direction was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator located in the lower part as viewed along the plumbline direction was 20 W. Otherwise, Working Example 13 was fabricated in the same manner as Working Example 8.
- The heat load of the CPU A whose heat was to be transferred to the first evaporator located in the upper part as viewed along the plumbline direction was 60 W, and the heat load of the CPU B whose heat was to be transferred to the second evaporator located in the lower part as viewed along the plumbline direction was 0 W. Otherwise, Working Example 14 was fabricated in the same manner as Working Example 8.
- Working Examples 1 to 14 were operated as described below, and the temperatures of the CPUs A and B were measured.
- First, power was turned off to the blade server, and the blade server, including the CPUs and the loop heat pipe, was allowed to cool down for a sufficient period of time until the entire structure reached room temperature. Next, power was turned on to the blade server, and the temperatures that the CPUs A and B finally reached were measured.
- The results of the measurements are given in
FIG. 12 . - In Working Example 14, the temperature of the CPU A reached 80° about one minute after power was turned on to the blade server. It was found that when the evaporators were vertically arranged, the loop heat pipe did not start up if the second evaporator located in the lower part as viewed along the plumbline direction did not receive heat.
- On the other hand, in Working Examples 1 to 13, the final temperatures of the CPUs A and B were both lower than 60° C. That is, it was found that even when the two evaporators were vertically arranged, if the second evaporator located in the lower part as viewed along the plumbline direction received heat, the loop heat pipe started up to cool the CPUs A and B. It was also found that when the two evaporators were horizontally arranged, the loop heat pipe started up to cool the CPUs A and B, even if one or the other of the evaporators did not receive heat.
- Further, using the loop heat pipe of the structure depicted in
FIG. 11 , measurements similar to those of Working Examples 1 to 14 were made; in this case also, similar results were obtained. - Next, using a two-phase fluid simulator, computer experiments were conducted to simulate the operation of the loop heat pipes having the structures depicted in
FIGS. 2 and 8 , respectively, and Working Examples 15 to 18 were obtained. SINDA/FLUINT (available from C&R TECHNOLOGIES) was used as the two-phase fluid simulator. - The loop heat pipe of the structure depicted in
FIG. 2 was used. A non-CFC refrigerant R141b, or more specifically, HCFC (hydrochlorofluorocarbon), was used as the refrigerant. The first and second liquid lines and the first and second vapor lines were each 4.5 mm in inner diameter. The first and second liquid lines were each 1.0 m in length. The first and second vapor lines were each 1.0 m in length. The first and second condensers were each 1.0 m in length. The first and second evaporators were each heated by a heat source having an output of 150 W. The first and second evaporators were arranged horizontally relative to the plumbline direction. The loop heat pipe had a first set formed by the second condenser, the second liquid line, the first evaporator, and the first vapor line, and a second set formed by the first condenser, the first liquid line, the second evaporator, and the second vapor line. In each set, the liquid line was divided into eight grids, the evaporator was divided into two grids, the vapor line was divided into 12 grids, and the condenser was divided into eight grids. Then, in the steady-state condition of the loop heat pipe, the proportion of the vapor phase of the working fluid was calculated for each grid in each set. The results of the calculations are given inFIG. 13 . - Working Example 16 was obtained in the same manner as Working Example 15, except that the loop heat pipe of the structure depicted in
FIG. 8 was used. The inner diameter of the bypass line was 4.5 mm, and the length of the bypass line was 1.4 mm. The results of the calculations are given inFIG. 14 . - Working Example 17 was obtained in the same manner as Working Example 15, except that the first evaporator in the first set was heated by a heat source having an output of 50 W and the second evaporator in the second set was heated by a heat source having an output of 150 W. The results of the calculations are given in
FIG. 15 . - Working Example 18 was obtained in the same manner as Working Example 16, except that the loop heat pipe of the structure depicted in
FIG. 8 was used and that the first evaporator in the first set was heated by a heat source having an output of 50 W and the second evaporator in the second set was heated by a heat source having an output of 150 W. The results of the calculations are given inFIG. 16 . - As can be seen from
FIGS. 13 and 14 , in Working Examples 15 and 16 in which the two evaporators were equally heated, all of the working fluid in each vapor line was in vapor phase, and all of the working fluid in each liquid line was in liquid phase. - As can be seen from
FIG. 15 , in Working Example 17, the circulation of the working fluid did occur in the loop heat pipe, but in the first vapor line in the first set, about 40% of the working fluid was in vapor phase and about 60% was in liquid phase. On the other hand, in the second set, all of the working fluid in the second vapor line was in vapor phase. - As can be seen from
FIG. 16 , in Working Example 18, all of the working fluid in each vapor line was in vapor phase, and all of the working fluid in each liquid line was in liquid phase. It was thus found that when the bypass line was added in the loop heat pipe structure of Working Example 17, all of the working fluid flowing in the vapor line of the first set also was maintained in vapor phase. - All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
Claims (11)
1. A loop heat pipe comprising:
a first evaporator and a second evaporator each of which vaporizes a liquid-phase working fluid by receiving heat from a heat source and thereby converts the liquid-phase working fluid to a vapor-phase working fluid;
a first condenser and a second condenser each of which condenses the vapor-phase working fluid by giving off heat and thereby converts the vapor-phase working fluid back to the liquid-phase working fluid;
a first vapor line through which the working fluid converted to the vapor phase by the first evaporator is transported to said first condenser;
a first liquid line through which the working fluid converted to the liquid phase by the first condenser is transported to said second evaporator;
a second vapor line through which the working fluid converted to the vapor phase by the second evaporator is transported to said second condenser; and
a second liquid line through which the working fluid converted to the liquid phase by the second condenser is transported to said first evaporator.
2. The loop heat pipe as claimed in claim 1 , further comprising a bypass line which connects between said first vapor line and said second vapor line.
3. The loop heat pipe as claimed in claim 2 , wherein said bypass line connects between a portion of said first vapor line in the vicinity of said first condenser and a portion of said second vapor line in the vicinity of said second condenser.
4. The loop heat pipe as claimed in claim 2 , wherein the cross-sectional area of a working fluid flow section of said bypass line is not larger than the cross-sectional area of a working fluid flow section of said first vapor line or said second vapor line.
5. The loop heat pipe as claimed in claim 4 , wherein the ratio of said cross-sectional area of said bypass line to said cross-sectional area of said first vapor line or said second vapor line is in the range of 0.1 to 1.
6. The loop heat pipe as claimed in claim 1 , wherein said first evaporator is located upwardly of said second evaporator as viewed along a plumbline direction.
7. The loop heat pipe as claimed in claim 1 , wherein said first condenser and said second condenser are constructed in integral fashion.
8. The loop heat pipe as claimed in claim 7 , wherein said first condenser includes a first condenser line and said second condenser includes a second condenser line, and wherein a plurality of heat sinking plates are coupled in common to both said first condenser line and said second condenser line.
9. A method for starting up a loop heat pipe which comprises: a first evaporator and a second evaporator each of which vaporizes a liquid-phase working fluid by receiving heat from a heat source and thereby converts the liquid-phase working fluid to a vapor-phase working fluid; a first condenser and a second condenser each of which condenses the vapor-phase working fluid by giving off heat and thereby converts the vapor-phase working fluid back to the liquid-phase working fluid; a first vapor line through which the working fluid converted to the vapor phase by the first evaporator is transported to said first condenser; a first liquid line through which the working fluid converted to the liquid phase by the first condenser is transported to said second evaporator; a second vapor line through which the working fluid converted to the vapor phase by the second evaporator is transported to said second condenser; and a second liquid line through which the working fluid converted to the liquid phase by the second condenser is transported to said first evaporator, wherein said first evaporator is located upwardly of said second evaporator as viewed along a plumbline direction, and said first evaporator is started to receive heat after a predetermined length of time has elapsed from the time said second evaporator began to receive heat.
10. The loop heat pipe startup method as claimed in claim 9 , wherein said predetermined length of time is determined based on the time taken for the liquid-phase working fluid to begin to flow into said first evaporator.
11. The loop heat pipe startup method as claimed in claim 9 , wherein said loop heat pipe comprises a bypass line which connects between said first vapor line and said second vapor line.
Applications Claiming Priority (3)
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JP2009164960 | 2009-07-13 | ||
JP2009-164960 | 2009-07-13 | ||
PCT/JP2010/056093 WO2011007604A1 (en) | 2009-07-13 | 2010-04-02 | Loop heat pump and startup method therefor |
Related Parent Applications (1)
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PCT/JP2010/056093 Continuation WO2011007604A1 (en) | 2009-07-13 | 2010-04-02 | Loop heat pump and startup method therefor |
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US20120132402A1 true US20120132402A1 (en) | 2012-05-31 |
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US13/323,973 Abandoned US20120132402A1 (en) | 2009-07-13 | 2011-12-13 | Loop heat pipe and startup method for the same |
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US (1) | US20120132402A1 (en) |
JP (1) | JP5218660B2 (en) |
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- 2010-04-02 WO PCT/JP2010/056093 patent/WO2011007604A1/en active Application Filing
- 2010-04-02 JP JP2011522752A patent/JP5218660B2/en not_active Expired - Fee Related
- 2010-04-02 CN CN2010800314070A patent/CN102472597A/en active Pending
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2011
- 2011-12-13 US US13/323,973 patent/US20120132402A1/en not_active Abandoned
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Also Published As
Publication number | Publication date |
---|---|
JPWO2011007604A1 (en) | 2012-12-27 |
WO2011007604A1 (en) | 2011-01-20 |
CN102472597A (en) | 2012-05-23 |
JP5218660B2 (en) | 2013-06-26 |
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