US20090114374A1

US20090114374A1 - Heat removal method and heat removal apparatus

Info

Publication number: US20090114374A1
Application number: US12/280,397
Authority: US
Inventors: Haruhiko Ohta; Yasuhisa Shinmoto
Original assignee: Kyushu University NUC
Current assignee: Kyushu University NUC
Priority date: 2006-02-22
Filing date: 2007-02-22
Publication date: 2009-05-07
Also published as: WO2007105450A1; TWI361265B; JPWO2007105450A1; TW200739014A; JP4269060B2

Abstract

A heat removal apparatus able to remove heat with a high heat flux from a large area is provided. A heat removal apparatus 1 has a heat removal use channel 31 provided adjacent to a heat removal object HO and a liquid supply use channel 32 extending along the heat removal use channel 31 and through which a liquid state refrigerant flows. In a wall portion 36 a partitioning the heat removal use channel 31 and the liquid supply use channel 32, communicating holes 38 communicating the heat removal use channel 31 and the liquid supply use channel 32 are provided at a plurality of positions. The liquid state refrigerant is supplied from the liquid supply use channel 32 to the heat removal use channel 31 via the communicating holes 38, whereby a liquid film is formed on an inner circumferential surface of the heat removal use channel 31. The liquid film evaporates by the heat from the heat removal object HO, and the evaporated refrigerant is discharged from the heat removal use channel 31.

Description

TECHNICAL FIELD

The present invention relates to a heat removal method and a heat removal apparatus.

BACKGROUND ART

The technology of running a liquid state refrigerant in a channel adjacent to a heat removal object and cooling the heat removal object by heat-exchange between the heat removal object and the refrigerant is known. This technology is being required to handle removal of heat with a high heat flux from a further larger area due to a rapid increase of heat generation densities of electronic apparatuses and the spread of large sized semiconductors for transforming electric power.
FIG. 14 is a diagram explaining a problem occurring in a case where a channel is made longer in order to remove heat from a large area etc. for a conventional heat removal channel 501. In FIG. 14, a plan view is shown on the left side of the sheet surface, and cross-sectional views at the positions y501 to y504 in the plan view are shown on the right side of the sheet surface at the positions y501 to y504.
The heat removal use channel 501 extends in a y-direction as shown in the plan view on the left side of the sheet surface of FIG. 14 and is run through by a liquid state refrigerant RL from an end portion 501 a as shown by arrows A501. The heat removal object (not shown) is arranged on, for example, a negative side in a z-direction of the heat removal use channel 501 and heats a bottom surface 501 b of the heat removal use channel 501 as indicated by arrows A502 in the cross-sectional views on the right side of the sheet surface of FIG. 14. In other words, the heat removal use channel 501 removes the heat of the heat removal object by the bottom surface 501 b.
At the position of y501, the liquid state refrigerant RL fills the heat removal use channel 501. At the position of y502, a portion of the liquid state refrigerant RL evaporates, and bubbles are generated by a gas state refrigerant RG. Note that bubbles are generated on the heated bottom surface 501 b side in the heat removal use channel 501. The bubbles expand and are join at the position of y503 resulting in less of an amount of the liquid state refrigerant RL on the bottom surface 501 b side. Further, at the position of y504, only the gas state refrigerant RG exists on the bottom surface 501 b side, and the liquid state refrigerant RL exists in a liquid film state on only a top surface 501 c facing the bottom surface 501 b.
Namely, when making the heat removal use channel 501 longer, as shown at the position of y504, a so-called burnout phenomenon occurs, so the heat removal object cannot sufficiently exchange heat with the liquid state refrigerant RL, and the cooling capability remarkably falls. Accordingly, in the heat removal use channel 501 shown in FIG. 14, it is regarded as a prerequisite that the liquid state refrigerant RL be filled from an upstream side to a downstream side of the heat removal use channel 501.
Patent Document 1 discloses a technique of providing a sub channel extended along a main channel at a position further apart from the heat removal object than the main channel serving as the heat removal use channel and supplying the liquid state refrigerant from the sub channel to the main channel via a plurality of communicating holes communicating the main channel and the sub channel to thereby make temperature of the liquid state refrigerant uniform from the upstream side to the downstream side of the main channel. Further, in Patent Document 1, a burnout phenomenon is prevented by providing a bursting device for bursting bubbles generated in the main channel.
Patent Document 1: Japanese Patent Publication (A) No. 2005-79337

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

The prior art shown in FIG. 14 and the technique of Patent Document 1 are based on running a liquid state refrigerant filled in a heat removal use channel (main channel), therefore there is an apprehension that various problems may arise. For example, the refrigerant utilizing latent heat for the heat removal is limited to a very small part of the refrigerant flowing through the main channel. For this reason, the heat flux cannot help but become small. In order to remove a required heat quantity from the heat removal object, a large amount of refrigerant must be run with respect to the heat removal area, so the heat removal apparatus becomes larger in size or the required pump power increases. Further, even if these are performed, in the heat removal from a large area extended in a downstream direction, it is fully predictable that burnout as shown at the position of y504 of FIG. 14 will be reached. For these reasons, there is an apprehension that problems may arise such as heat removal from a large area becoming difficult. Other than this, there is an apprehension that problems such as pressure loss and pulsation in the flow of the main channel may occur because of the merging of the flow of the refrigerant in the sub channel with the flow of the refrigerant in the main channel, and a member or device for bursting bubbles generated in the main channel must be provided.
Desirably a heat removal method and a heat removal apparatus capable of removing heat with a high heat flux from a large area are provided.

Means for Solving the Problems

A heat removal method of a first aspect of the present invention removes heat of a heat removal object by supplying a liquid state refrigerant into a heat removal use channel provided adjacent to the heat removal object at a plurality of positions in a predetermined direction of the heat removal use channel, forming a liquid film of the refrigerant over the plurality of positions on an inner circumferential surface of the heat removal use channel, making the liquid film evaporate by the heat from the heat removal object, and discharging the evaporated refrigerant from the heat removal use channel.
Preferably, the predetermined direction is a flow direction of the heat removal use channel.
A heat removal method of a second aspect of the present invention removes heat of a heat removal object by supplying a liquid state refrigerant into a heat removal use channel provided adjacent to the heat removal object within a predetermined range of a flow direction of the heat removal use channel, forming a liquid film of the refrigerant over the predetermined range on the inner circumferential surface of the heat removal use channel, making the liquid film evaporate by the heat from the heat removal object, and discharging the evaporated refrigerant from the heat removal use channel.
A heat removal apparatus of a third aspect of the present invention has a heat removal use channel provided adjacent to a heat removal object; and a liquid supply portion constructed to supply a liquid state refrigerant into the heat removal use channel at a plurality of positions in a predetermined direction of the heat removal use channel and form a liquid film of the refrigerant over the plurality of positions on the inner circumferential surface of the heat removal use channel.
Preferably, the predetermined direction is a flow direction of the heat removal use channel.
Preferably, the liquid supply portion has a liquid supply use channel which is adjacent to the heat removal use channel and in which the liquid state refrigerant flows, and a wall portion partitioning the heat removal use channel and the liquid supply use channel has refrigerant passage portions constructed to allow passage of the liquid state refrigerant from the liquid supply use channel to the heat removal use channel at the plurality of positions.
Preferably, the heat removal use channel is partitioned to a plurality of sections in the flow direction, and the plurality of sections each are provided with discharge ports discharging the gas state refrigerant.
Preferably, the heat removal use channel has discharge ports of the refrigerant provided at both ends in the flow direction.
Preferably, the inner circumferential surface of the heat removal use channel is provided with groove portions.
Preferably, the inner circumferential surface of the heat removal use channel is provided with groove portions extending in a direction traversing the heat removal use channel.
Preferably, the inner circumferential surface of the heat removal use channel is provided with groove portions extending in a direction along the heat removal use channel.
Preferably, the inner circumferential surface of the heat removal use channel is lined by a sheet through which the liquid state refrigerant can permeate.
Preferably, the inner circumferential surface of the heat removal use channel is roughened.

EFFECT OF THE INVENTION

According to the present invention, heat can be removed from a large area with a high heat flux.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A diagram showing an overall construction of a heat removal apparatus of an embodiment of the present invention.

FIG. 2 Diagrams schematically showing an example of the construction of a heat removal portion of the heat removal apparatus of FIG. 1.

FIG. 3 A diagram explaining a heat removal method in an example of the structure of the heat removal portion of FIG. 2A to FIG. 2C.

FIG. 4 Diagrams explaining effects of the heat removal apparatus of FIG. 1 captured from another viewpoint.

FIG. 5 Diagrams explaining modifications of a liquid supply method to a heat removal use channel from a viewpoint of a heating length.

FIG. 6 Cross-sectional views showing modifications of the supply method of liquid to the heat removal use channel.

FIG. 7 Diagrams explaining patterns of flow in a liquid supply use channel and the heat removal use channel.

FIG. 8 Diagrams showing modifications wherein patterns of flow in the liquid supply use channel and the heat removal use channel are three-dimensionally extended.

FIG. 9 Perspective views showing modifications of a wall portion partitioning the heat removal use channel and the liquid supply use channel and communicating holes.

FIG. 10 Diagrams explaining examples of patterns of an inner circumferential surface of the heat removal use channel.

FIG. 11 Diagrams showing a modification wherein the heat removal use channel is magnified in a width direction of the channel.

FIG. 12 Diagrams showing a modification wherein the heat removal use channel is magnified in the flow direction.

FIG. 13 A diagram showing a modification of the overall construction of the heat removal apparatus.

FIG. 14 A diagram showing a conventional heat removal use channel.

FIG. 15 Diagrams explaining a supply rate of a liquid state refrigerant from the liquid supply use channel to the heat removal use channel.

FIG. 16 Diagrams showing examples of making a fluid resistance of the refrigerant passage portion small in an upstream portion and large in a downstream portion in the liquid supply use channel.

FIG. 17 A diagram showing an example of application of the present invention.

FIG. 18 A diagram showing another example of application of the present invention.

FIG. 19 Diagrams explaining effects of the present invention

DESCRIPTION OF NOTATIONS

- 1 . . . heat removal apparatus, 12 . . . heat removal portion, 31 . . . heat removal use channel, 32 . . . liquid supply use channel, 38 . . . communicating holes, and HO . . . heat removal object.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a diagram showing an overall construction of a heat removal apparatus 1 according to an embodiment of the present invention. The heat removal apparatus 1 has a storage tank 3 storing the liquid state refrigerant RL, a pump 5 pumping out the refrigerant in the storage tank 3 etc., a heat removal portion 12 removing the heat of the heat removal object HO (see FIG. 2A to FIG. 2C) by the refrigerant pumped out from the pump 5, a condensation portion 14 condensing a gas state refrigerant flowing out of the heat removal portion 12, a gas and liquid phase separator 19 separating the refrigerant flowing out of the condensation portion 14 to the gas state refrigerant and the liquid state refrigerant, and a subcooling portion 21 subcooling the refrigerant flowing out of the gas and liquid phase separator 19 for preventing cavitation of the pump 5. The refrigerant subcooled by the subcooling portion 21 is pumped out by the pump 5 or stored in the storage tank 3.
The storage tank 3 is constructed by, for example, an accumulator and is used for keeping the pressure of a circulation system of the heat removal apparatus 1 at a predetermined pressure and also fine adjustment of the liquid temperature in accordance with load fluctuations. The pump 5 is driven by a motor 6. The operation of the motor 6 is controlled by a control unit 7. The condensation portion 14 is, for example, an air cooled type. The air for heat exchange with the refrigerant is sent into this by a fan 15. The fan 15 is driven by a motor 16. The operation of the motor 16 is controlled by a control unit 17. The subcooling portion 21 is, for example, an air cooled type. The air for heat exchange with the refrigerant is sent into this by a fan 22. The fan 22 is driven by a motor 23. The operation of the motor 23 is controlled by a control unit 24.
Between the pump 5 and the heat removal portion 12, a flow rate sensor 9 detecting the flow rate of the liquid state refrigerant RL flowing into the heat removal portion 12 and a temperature sensor 10 detecting the temperature of the liquid state refrigerant RL flowing into the heat removal portion 12 are provided. The control unit 7 controls the operation of the motor 6 based on a detection result of the flow rate sensor 9, the control unit 17 controls the operation of the motor 16 based on the detection result of the temperature sensor 10, and the control unit 24 controls the operation of the motor 23 based on the detection result of the temperature sensor 10.
In the heat removal portion 12, the heat is removed by making the refrigerant absorb the heat having a quantity Q from the heat removal object HO. At the condensation portion 14 and subcooling portion 21, heats having quantities Q1 and Q2 absorbed by the refrigerant are released. Note that, assuming that there is no heat loss from piping, Q=Q1+Q2 stands.
FIG. 2A to FIG. 2C are diagrams schematically showing the construction of the heat removal portion 12, in which FIG. 2A is a partially see-through perspective view, FIG. 2B is a cross-sectional view taken along a IIb-IIb arrow direction of FIG. 2A, and FIG. 2C is a cross-sectional view seen from an x-direction showing enlarged an area E surrounded by a solid line in FIG. 2A. Note that, for convenience, in some cases the z-direction is expressed as the up and down direction, but the heat removal portion 12 can exhibit a constant heat removal effect when any of the x-direction, y-direction, and z-direction becomes the up and down direction depending on its size or other various conditions.
The heat removal portion 12 has a heat removal use channel 31 provided adjacent to the heat removal object HO and a liquid supply use channel 32 for supplying the liquid state refrigerant to the heat removal use channel 31. Note that the liquid supply use channel 32 or a refrigerant pumping system including the pump 5 etc. in addition to the liquid supply use channel 32 is an example of the liquid supply portion of the present invention.
The heat removal use channel 31 is formed by, for example, a first plate shaped member 34 provided abutting against the heat removal object HO, a second plate shaped member 35 arranged facing the first plate shaped member 34, and two pipes 36 arranged between the first plate shaped member 34 and the second plate shaped member 35 and extending in the flow direction of the heat removal use channel 31 (flow direction of refrigerant, length direction of channel, y-direction) parallel to each other in a region surrounded by these members. Note that the heat removal object may be arranged not only on the first plate shaped member 34 side, but also on the second plate shaped member 35 side. Further, a rectangular duct or other hollow body with an appropriate cross-sectional shape may be used in place of the pipe 36. In the heat removal use channel 31, one end in the flow direction (positive side of the y-direction) is open and connected to the condensation portion 14. The other end of the flow direction is closed by a not shown wall portion.
The first plate shaped member 34, second plate shaped member 35, and pipe 36 may be formed by a metal, plastic, or other appropriate material. The first plate shaped member 34 and second plate shaped member 35 and the pipe 36 may, for example, be joined by using a binder or solder, joined by welding or fusing, or otherwise appropriately joined.
The liquid supply use channel 32 is formed inside the pipe 36 by the pipe 36. The position of the liquid supply use channel 32 may be a position superposed or not superposed on the heat removal object HO when seen in the z-direction. One end portion 36 b of the pipe 36 is open whereby an inflowing port 37 is formed. The end portion 36 b is connected to the pump 5. Note that the other end portion 36 c of the pipe 36 is closed. Further, in the pipe 36, in the wall portion 36 a partitioning the heat removal use channel 31 and the liquid supply use channel 32, communicating holes 38 communicating the heat removal use channel 31 and the liquid supply use channel 32 are provided at a plurality of positions in the flow direction (y-direction) of the heat removal use channel 31. the communicating hole 38 is one example of the refrigerant passage portion of the present invention. The plurality of communicating holes 38 have the same diameters relative to each other and are provided at equal intervals.
In the first plate shaped member 34, groove portions 40 extending in a direction perpendicular to the flow direction of the heat removal use channel 31 (width direction, x-direction) are formed in a surface forming the inner circumferential surface of the heat removal use channel 31. A plurality of groove portions 40 are provided in the flow direction of the heat removal use channel 31. For example, the same number of groove portions 40 as the number of the plurality of communicating holes 38 are provided at the same positions of the plurality of communicating holes 38.
FIG. 3 is a diagram explaining the heat removal method in the heat removal portion 12. In FIG. 3, a plan view is shown on the left side of the sheet surface, and cross-sectional views at the positions y1 to y3 in the plan view are shown on the right side of the sheet surface at the positions of y1 to y3.
In the heat removal portion 12, as indicated by an arrow A1 in FIG. 2A, the liquid state refrigerant RL pumped out by the pump 5 flows into the liquid supply use channel 32 from the inflowing port 37. The liquid state refrigerant RL flowing into the liquid supply use channel 32 flows into the heat removal use channel 31 from the communicating holes 38 as indicated by an arrow A2 in FIG. 2A and an arrow A5 in FIG. 3.
The liquid state refrigerant RL flowing into the heat removal use channel 31 forms a liquid film on the inner circumferential surface on the first plate shaped member 34 side of the heat removal use channel 31. The communicating holes 38 are provided at a plurality of positions in the flow direction of the heat removal use channel 31, therefore the liquid film of the refrigerant RL is formed over the entire flow direction from the upstream side to the downstream side of the heat removal use channel 31.
Then, as indicated by arrows A6 in the cross-sectional views on the right side of the sheet surface of FIG. 3, the heat from the heat removal object HO is transmitted to the first plate shaped member 34 and the liquid film of the refrigerant RL evaporates and becomes the gas state refrigerant RG. In other words, the refrigerant absorbs the heat in an amount approximately corresponding to the latent heat from the heat removal object HO.
The gas state refrigerant RG of the heat removal use channel 31 flows out of an opening end portion and flows into the condensation portion 14 as indicated by an arrow A3 of FIG. 2A. Note that a fan or other exhausting means for exhausting the gas state refrigerant RG may be provided in the channel as well.
For formation of a liquid film in the heat removal use channel 31, the various parameters may be set or control performed as follows.
In the heat removal use channel 31, the following equation (1) stands:
ρ₁ ×dV/dt×(C _pl×(T _s −T _in)+h _fg ×X _out)=Q (1)
where,
Q: Heat removal amount per unit time (W)
ρ₁: Density of liquid state refrigerant (kg/m³)
dV/dt: Supply rate of liquid state refrigerant to heat removal use channel per unit time (m³/s)
C_pl: Specific heat at constant pressure of liquid state refrigerant (J/kgK)
T_s: Saturation temperature of refrigerant in heat removal use channel (K)
T_in: Temperature of liquid state refrigerant when it is supplied to heat removal use channel (K)
h_fg: Evaporation latent heat of refrigerant (J/kg)
X_out: Mass ratio of evaporation flow rate with respect to total flow rate of refrigerant of heat removal use channel
From equation (1), the following equation (2) is obtained:
X _out=((Q/(ρ₁ ×dV/dt)−C _pl×(T _s −T _in))/h _fg (2)
Accordingly, in the heat removal apparatus 1, if various parameters are set so that X_outbecomes the predetermined value, a liquid film can be formed in the heat removal use channel 31. If showing an example of the range of X_outin which the liquid film is preferably formed, the range is 0.2 to 1.
Q is determined according to the heat removal amount required in the heat removal object HO. ρ₁, C_pl, and h_fgcan be adjusted by selection of component ingredients of the refrigerant or selection of the working pressure. dV/dt, T_in, and T_scan be adjusted by structural aspects of the various means at the time of design of the heat removal apparatus 1 and can be adjusted by operations of the various means at the time of the operation of the heat removal apparatus 1.
The X_outat the time of the operation of the heat removal apparatus 1 is, for example, controlled as follows.
dV/dt is detected by the flow rate sensor 9. The control unit 7 controls the operation of the pump 5 via the motor 6 based on the detection value of the flow rate sensor 9 so that dV/dt approaches a predetermined target value. Namely, dV/dt is feedback controlled by the control unit 7, whereby X_outis controlled.
T_inis detected by the temperature sensor 10. The control unit 17 controls the operation of the motor 16 based on the detection value of the temperature sensor 10 so that T_inapproaches a predetermined target value. Further, the control unit 24 controls the operation of the motor 23 based on the detection value of the temperature sensor 10 so that T_inapproaches the predetermined target value. Namely, T_inis feedback controlled by the control unit 17 and control unit 24, whereby X_outis controlled.
Note that the control unit 17 (condensation portion 14) and the control unit 24 (subcooling portion 21) may appropriately play roles in the control of T_in. For example, at the time of start of the operation, T_inis feedback controlled in the condensation portion 14, and the cooling in the subcooling portion 21 is suspended. When the temperature of the refrigerant rises up to the predetermined temperature or more, the speed of the motor 16 is made constant in the condensation portion 14 to make the cooling efficiency constant, and T is feedback controlled in the subcooling portion 21.
T_sis determined according to the pressure in the heat removal use channel 31. Accordingly, T_sis strongly influenced by an amount of the heat dissipation by the fans 15 and 22. However, if the heat transmission at the condensation portion 14 or the subcooling portion 21 is changed by the adjustment of dV/dt, T_scan be indirectly controlled by controlling the expansion ratio etc. of the refrigerant. Further, for example, a pressure sensor may be provided in the heat removal use channel 31, a pressure adjustment valve may be provided in the channel to the condensation portion 14, and the operation of the pressure adjustment valve may be controlled based on the detection result of the pressure sensor.
According to the above embodiment, the liquid state refrigerant RL is supplied to a plurality of positions in the flow direction of the heat removal use channel 31 provided adjacent to the heat removal object HO, and a liquid film of the refrigerant RL is formed over the plurality of positions on the inner circumferential surface of the heat removal use channel 31, therefore the refrigerant can be efficiently evaporated without depleting the liquid state refrigerant RL within a wide range from the upstream side to the downstream side of the heat removal use channel 31. Accordingly, in comparison with the conventional case, the ratio of the heat removal amount by latent heat with respect to the heat removal amount by sensible heat greatly increases, and heat can be removed with a high heat flux from a large area. Also, the flow rate (mass) of the refrigerant can be reduced, and a reduction of size of the heat removal apparatus 1 and the heat removal use channel 31 can be achieved. The flow rate is kept low, the pressure loss is smaller than that in Patent Document 1 due to vapor running through the main channel, and the pump capability given by a product of the two is greatly reduced. The liquid state refrigerant RL removes heat by the latent heat. Therefore, in comparison with the case of heat removal by sensible heat or boiling as in the conventional case, the heat transmission is very good. The temperature of the refrigerant RL need not be very low with respect to a permissible temperature (target temperature after heat removal) of the heat removal object HO. For this reason, the cooling capability demanded from the condensation portion 14 and subcooling portion 21 can be lowered. In the condensation portion 14 and the subcooling portion 21, the temperature difference between the refrigerant flowing in their internal portions and the open air becomes large, so it becomes possible to efficiently cool the refrigerant. Therefore the condensation portion 14 and the subcooling portion 21 can be reduced in size. The invention is based on running a gas state refrigerant through the heat removal use channel 31, therefore the various problems which occur when running a liquid state refrigerant through the heat removal use channel do not occur. For example, the merging of the flow of the sub channel with that of the main channel and resultant unstable flow of the main channel as in Patent Document 1 will not occur. It is not necessary to provide a member or device for bursting the les generated in the main channel either.
The heat removal apparatus 1 has the liquid supply use channel 32 extending along the heat removal use channel 31 and allowing the liquid state refrigerant RL to pass therethrough. Communicating holes 38 communicating the heat removal use channel 31 and the liquid supply use channel 32 are provided at a plurality of positions in the flow direction of the heat removal use channel 31 in the wall portion 36 a partitioning the heat removal use channel 31 and the liquid supply use channel 32. Therefore, while the construction is simple, the liquid film can be formed by supplying the refrigerant to a plurality of positions in the flow direction of the heat removal use channel 31.
At the inner circumferential surface of the heat removal use channel 31, the groove portions 40 extending in the direction perpendicular to the heat removal use channel 31 are provided, therefore the liquid film easily spreads in the direction perpendicular to the heat removal use channel 31, and the depletion of the refrigerant at a position away from the liquid supply use channel 32, that is, the center side position of the heat removal use channel 31, is suppressed. Note that the principle of the spread of the liquid state refrigerant by the groove portions 40 is as follows. The liquid state refrigerant RL sticks to the side surfaces (inclined surfaces) of each groove portion 40 due to surface tension, so the surface of the liquid state refrigerant RL in each groove portion 40 is concave. Although the contact angles formed by the surface of the refrigerant RL and the side surfaces of the groove portion 40 is equivalent between the center side of the heat removal use channel 31 and the side portion side (liquid supply use channel 32 side), the refrigerant becomes depleted the more toward the center side and the amount of the refrigerant RL is smaller. Therefore, the curvature of the concave surface becomes larger toward the center side. For this reason, the force causing the refrigerant RL to shrink becomes stronger toward the center side, and a state of balance with a high gas pressure is exhibited. However, the magnitude of the gas state refrigerant RG covering the surface of the refrigerant RL is equivalent between the center side and the side portion side. For this reason, the refrigerant RG of the liquid automatically flows to the center side since a negative pressure gradient is caused from the side portion side to the center side.
FIG. 4A to 4C are diagrams explaining the effects of the heat removal apparatus 1 of the present embodiment grasped from another viewpoint.
FIG. 4A shows a situation of the refrigerant in the conventional heat removal use channel 501. In the conventional heat removal use channel 501, the liquid state refrigerant RL flows into the heat removal use channel 501 from one end (arrow 7A) and flows toward the other end. Accordingly, a length L501 of the flow direction of the heat removal use channel 501 becomes a heating length of heating of the refrigerant. When the length L501 exceeds a constant length, the liquid state refrigerant RL evaporates to become the gas state refrigerant RG and is discharged from the downstream side of the heat removal use channel 501 (arrow A8). Namely, on the downstream side of the heat removal use channel 501, a dry out phenomenon occurs and the inner circumferential surface is depleted of the refrigerant RL, so the cooling capability is remarkably lowered.
However, as shown in FIG. 4B, in the heat removal use channel 31 of the present embodiment, the liquid state refrigerant RL is supplied from both sides of the heat removal use channel 31 to the direction perpendicular to the flow direction, therefore the heating length becomes a length L1 of half of the width of the heat removal use channel 31. Accordingly, if the liquid state refrigerant RL is supplied in an amount by which the refrigerant RL is not depleted for the period where it flows through the length L1, the cooling capability can be exhibited over the entire surface of the heat removal use channel 31. In other words, the influence of the length of the heat removal use channel 31 in the flow direction exerted upon the depletion of the refrigerant RL is remarkably reduced, and the degree of freedom in setting the length of the flow direction is improved.
Note that, as shown in FIG. 4C, in the heat removal use channel 31 of the present embodiment as well, if the width of the heat removal use channel 31 becomes large and a heating length (L2) becomes long with respect to the amount of supply of the liquid state refrigerant RL, the liquid state refrigerant RL is depleted at the center side of the heat removal use channel 31. Accordingly, it is necessary to appropriately set the width of the heat removal use channel 31 and the amount of supply of the liquid state refrigerant RL.
FIG. 5A to FIG. 5D are diagrams explaining modifications of the method of supply of the liquid to the heat removal use channel from the viewpoint of the heating length explained with reference to FIG. 4A to FIG. 4C. Note that, in FIG. 5A to FIG. 5D, as indicated by the arrows A9 in FIG. 5A, a case where the heat removal use channel is heated from both surfaces in the up and down direction of the sheet surface (corresponding to the first plate shaped member 34 side and second plate shaped member 35 side of the heat removal use channel 31) is exemplified.
FIG. 5A shows a modification of the supply of the liquid refrigerant from both sides of a rectangle as indicated by arrows A10 in a heat removal use channel 41 having a rectangular cross-section. In this modification, the heating length becomes a length L4 of the half of the width of the heat removal use channel 41.
FIG. 5B shows a modification of the supply of the liquid refrigerant from two facing points of a circle as indicated by the forked arrows A11 in a heat removal use channel 42 having a circular cross-section. In this modification, the heating length becomes a length L5 of ¼ of the circumference of the heat removal use channel 42.
FIG. 5C shows a modification of the supply of the liquid refrigerant from one point of a circle as indicated by a forked arrow A12 in a heat removal use channel 43 having a circular cross-section. In this modification, the heating length becomes a length L6 of ½ of the circumference of the heat removal use channel 43.
FIG. 5D shows a modification of the supply of the liquid refrigerant from four points equally arranged around the circumference as indicated by the forked arrows A13 in a heat removal use channel 44 having a circular cross-section. In this modification, the heating length becomes a length L7 of ⅛ of the circumference of the heat removal use channel 44.
As shown in FIG. 5A to FIG. 5D, if supply ports of the liquid are increased, the heating length becomes shorter. This is advantageous for preventing the depletion of the refrigerant. However, if the supply ports increase, there is an apprehension that the number of parts and number of manufacturing steps may increase. Accordingly, the cross-sectional shape of the heat removal use channel and the positions and number of supply ports of the liquid state refrigerant are preferably set considering various conditions such as a saturation temperature of the refrigerant, size of the heat removal object, and amount of heat generated by the heat removal object. Note that FIG. 5A to FIG. 5D are examples of combinations of the cross-sectional shapes of the heat removal use channel and the position and number of the supply ports. Various modifications are possible other than these.
FIG. 6A to FIG. 6D are cross-sectional views showing modifications of the method of supply of the liquid to the heat removal use channel. Note that, in FIG. 6A to FIG. 6D, the heat removal object is provided on at least one side between the positive side and the negative side of the z-direction of the channel, and the flow direction of the heat removal use channel is the y-direction.
FIG. 6A shows a modification wherein a wall portion 47 is provided in a channel having a rectangular cross-section to divide the channel into a heat removal use channel 45 and a liquid supply use channel 46. The wall portion 47 is provided with not shown communicating holes at a plurality of positions in the flow direction (y-direction) of the heat removal use channel 45. The liquid state refrigerant is supplied to the heat removal use channel 45 from the liquid supply use channel 46 via the communicating holes as indicated by the arrows A15. Note that, in this modification, by providing the wall portion 47, the heat removal use channel 45 and the liquid supply use channel 46 can be easily constructed.
FIG. 6B shows a modification wherein nozzles 50 are provided on both sides of the heat removal use channel 49. The nozzles 50 are provided at a plurality of positions in the flow direction (y-direction) of the heat removal use channel 49. The liquid state refrigerant is supplied to the heat removal use channel 49 by the nozzles 50 as indicated by the arrows A17. In this modification, the supply direction of the liquid can be adjusted by the adjustment of the orientations of the nozzles 50, while the supply position of the liquid can be adjusted by adjusting the position of the front ends 50 a of the nozzles 50 in the direction perpendicular to the flow direction of the heat removal use channel 49 (x-direction). The orientations, positions, and flow rates of the plurality of nozzles 50 may be set different from each other as well. Accordingly, change of settings in accordance with a usage environment etc. of the heat removal apparatus is easy.
FIG. 6C shows a modification wherein pipes 51 are provided at both ends of the internal portion of a rectangular channel, a heat removal use channel 52 is formed outside the pipes 51, and liquid supply use channels 53 are formed inside the pipes 51. In this modification, in the same way as the embodiment shown in FIG. 2A, the liquid refrigerant is supplied from a plurality of communicating holes formed in the pipes 51 to the heat removal use channel 52 (arrows A19). In this modification, by just inserting the pipes 51 into the rectangular channel, the heat removal use channel 52 and the liquid supply use channels 53 can be constructed. Further, the pipes 51 contribute to reinforcement of the structural strength of the rectangular channel.
FIG. 6D shows a modification wherein a wall portion 55 made of a porous member is provided in the rectangular channel to form a heat removal use channel 56 and liquid supply use channels 57. The porous member will be explained later.
FIG. 6E shows a modification wherein a liquid supply use channel 60 having a width equivalent to that of the heat removal use channel 59 is made to run parallel to the heat removal use channel 59 while being superposed on it. Note that, in the modification of FIG. 6E, the heat removal object is arranged on a lower side of the sheet surface of the heat removal use channel 59. In the heat removal use channel 59 and the liquid supply use channel 60, not shown communicating holes communicating the two are formed at both sides of the channels. A plurality of communicating holes are provided in the flow direction (y-direction) of the heat removal use channel 59. The liquid state refrigerant of the liquid supply use channel 60 is supplied via the communicating holes to the heat removal use channel 59 as indicated by the arrow A21s. In this modification, the heat removal use channel 59 and the liquid supply use channel 60 are stacked up, so reduction of the width, ensuring the flow rate of the liquid supply use channel 60, and reduction of the temperature difference between the heat removal use channel 59 and the liquid supply use channel 60 are achieved.
FIG. 6F shows a modification wherein a nozzle 62 protruding into the heat removal use channel 49 is provided at the center of the heat removal use channel 49 in addition to the modification of FIG. 6B. In this modification, the heat removal object is provided on a lower side of the sheet surface of the heat removal use channel 49, and the nozzle 62 protrudes into the heat removal use channel 49 from an upper side of the sheet surface of the heat removal use channel 49. There is a possibility of depletion of the liquid state refrigerant from the nozzle 50 before arriving at the center of the width direction. Therefore, in this modification, the liquid state refrigerant is supplied to the center of the heat removal use channel 49 by the nozzle 62 to prevent the depletion at the center in the width direction of the heat removal use channel 49. Further, the liquid state refrigerant is supplied to the center by the nozzle 62. Therefore, by making the front end position of the nozzle 62 approach the surface on the side heated by the heat removal object (surface on the lower side of the sheet surface), the liquid film can be reliably formed on the surface.
FIG. 6G shows a modification wherein nozzles 65 protruding into the heat removal use channel 59 from the liquid supply use channel 60 are provided at a plurality of positions in the width direction of the heat removal use channel 59 in place of communicating holes on the two sides in the modification shown in FIG. 6E. The liquid state refrigerant of the liquid supply use channel 60 is supplied via the nozzles 65 to the heat removal use channel 59. In this modification, the heating length becomes the distance between nozzles 65. Accordingly, the depletion of the liquid state refrigerant can be prevented by making the heating length further shorter than the width of the heat removal use channel 59. In other words, extension of the heat removal use channel 59 to the width direction is possible. Further, by making the front end positions of the nozzles 65 approach the surface on the side heated by the heat removal object (surface on the lower side of the sheet surface), the liquid film can be reliably formed on the surface.
FIG. 7A to FIG. 7D are diagrams explaining patterns of flows in the liquid supply use channel and the heat removal use channel. In FIG. 7A to FIG. 7D, solid arrows indicate the flow directions of the liquid state refrigerant, and the broken line arrows indicate the flow directions of the gas state refrigerant.
In the liquid supply use channel, as in a liquid supply use channel 74 of FIG. 7A, the liquid state refrigerant may flow in from one end 74 a of a heat removal use channel 73 in the flow direction (y-direction) and the liquid state refrigerant may flow out of the other end 74 b. Alternatively, as in the liquid supply use channel 68 of FIG. 7B and the liquid supply use channel 71 of FIG. 7C, the other ends 68 b and 71 b may be closed and only communicating holes (not shown) with the heat removal use channels 67 and 70 may be provided as outflow ports of the liquid state refrigerant. Further, as shown in FIG. 7D, an inflowing port 77 a may be provided at an appropriate position in the middle of the flow direction of a heat removal use channel 76. The liquid state refrigerant may flow toward one end 77 b and the other end 77 c of this flow direction as well. In this case, as shown in FIG. 7D, the one end 77 b and the other end 77 c of the liquid supply use channel 77 may be closed and only communicating holes with the heat removal use channel 76 may be provided as outflow ports of the refrigerant, or the refrigerant may flow out from one of the one end 77 b and the other end 77 c. Further, when both ends of the liquid supply use channel are opened as in FIG. 7A, both may be used as inflowing ports.
In the heat removal use channel, the liquid state refrigerant may be supplied from one end 73 a as in the heat removal use channel 73 of FIG. 7A or the liquid state refrigerant may be supplied from only the liquid supply use channel as in the heat removal use channels of FIG. 7B to FIG. 7D. Further, in the heat removal use channel, the gas state refrigerant may flow out from only one end side of the flow direction as in the heat removal use channel 67 of FIG. 7B, or the gas state refrigerant may flow out to both sides of the flow direction as in the heat removal use channel 70 of FIG. 7C and the heat removal use channel 76 of FIG. 7D.
As shown in FIG. 7C and FIG. 7D, the refrigerant can be discharged from both end sides of the heat removal use channel in the flow direction, because the heat is removed by evaporation of the liquid film formed in the heat removal use channel and the gas state refrigerant is discharged from the heat removal use channel. Namely, as in the conventional one, in the technique basically removing the heat by the sensible heat of the liquid state refrigerant or usual boiling, it is necessary to run a large amount of liquid state refrigerant through the heat removal use channel. As a result, as shown in FIG. 14, a structure of running the liquid state refrigerant from one end to the other end of the heat removal use channel is employed. If assuming that the channel of the refrigerant is set as in FIG. 7C in the prior art, a flow with a sufficient flow rate cannot be formed in the heat removal use channel, and a sufficient heat removal effect cannot be obtained. In the present embodiment, however, it is enough to supply a sufficient amount of refrigerant for the formation of the liquid film, therefore it is not necessary to use one end of the heat removal use channel as the inflowing port of the liquid state refrigerant, so both ends of the heat removal use channel can be utilized as outflow ports of the refrigerant. Note that by using both ends as the outflow ports, the refrigerant is quickly exhausted from the heat removal use channel and an excessive increase of the exhaust speed can be suppressed.
Further, as shown in FIG. 7D, it is possible to provide an inflowing port of the liquid supply use channel at an optional position and direct the liquid state refrigerant toward both sides in the flow direction (y-direction), because the apparatus is constructed to remove the heat by the evaporation of the liquid film formed in the heat removal use channel and discharge the gas state refrigerant from the heat removal use channel. Namely, the conventional construction separated the flow of the liquid state refrigerant to flows of the main channel and the sub channel, then made them merge, so the flow of the main channel and the flow of the sub channel had to become the same direction. In the present embodiment, however, the gas state refrigerant flows in the heat removal use channel, and the liquid state refrigerant flows in the liquid supply use channel, therefore the flow directions can be freely set with respect to each other.
Accordingly, in the present embodiment, various flow patterns as shown in FIG. 7A to FIG. 7D are possible, and the degree of freedom of design is improved. Note that FIG. 7A to FIG. 7D are examples. The liquid state refrigerant and gas state refrigerant may be run in various patterns other than those as well.
The improvement of the degree of freedom of design of the heat removal use channel and liquid supply use channel as explained in FIG. 7A to FIG. 7D makes three-dimension extension of the patterns of flow in the liquid supply use channel and heat removal use channel possible as well. FIG. 8A to FIG. 8F are diagrams showing modifications of three-dimensionally extending patterns of flow in the liquid supply use channel and heat removal use channel. In FIG. 8A to FIG. 8F, the solid arrows indicate flow directions of the liquid state refrigerant, and the broken line arrows indicate flow directions of the gas state refrigerant.
FIG. 8A is a plan view showing a modification wherein the liquid state refrigerant is supplied in a direction (z-direction) perpendicular to the heat removal object in addition to the modification shown in FIG. 7D, while FIG. 8B is a cross-sectional view seen from the lower portion of the sheet surface of FIG. 8A. In this modification, the heat removal object is provided on the lower side of the sheet surface of FIG. 8B. At the position of the center in the width direction of the heat removal use channel 76, a liquid supply use channel 79 extended along the flow direction of a heat removal use channel 76 is provided. The liquid supply use channel 79 has, for example, the same shape as that of the liquid supply use channel 77, but is slightly smaller. An inflowing port 79 a through which the liquid state refrigerant is supplied is provided on the upper side of the sheet surface, and a plurality of communicating holes (not shown) for supplying the liquid state refrigerant to the heat removal use channel 76 are provided along the heat removal use channel 76 on the lower side of the sheet surface. The modification is effective for preventing depletion of liquid at the center of the heat removal use channel 76 in the same way as the modification shown in FIG. 6F.
FIG. 8C is a modification wherein a plurality of liquid supply use channels 79 shown in FIG. 8A are arranged in the width direction of a heat removal use channel 81, while FIG. 8D is a cross-sectional view seen from the lower side of the sheet surface of FIG. 8C. In this modification, in the same way as the modification shown in FIG. 6G, extension to the width direction of the heat removal use channel 81 is made possible. Note that, as apparent from FIG. 8C, in the heat removal use channel of the present invention, the flow direction does not have to be the longitudinal direction.
FIG. 8E is a modification wherein discharge ports 83 a for discharging the gas state refrigerant are provided in the direction perpendicular to the longitudinal direction and the width direction of the heat removal use channel 83, while FIG. 8F is a cross-sectional view seen from the lower side of the sheet surface of FIG. 8E. In this modification, the heat removal object is provided on the lower side of the sheet surface of FIG. 8F, and the discharge ports 83 a are formed on the opposite side to the heat removal object in the inner circumferential surface of the heat removal use channel 83. Note that, in the heat removal use channel 83, both ends in the longitudinal direction (flow direction of the liquid supply use channel 84) are closed, and the outflow port of the gas state refrigerant is only the discharge port 83 a. A plurality of discharge ports 83 a are provided along, for example, the flow direction of the liquid supply use channel 84. In this modification, the evaporated refrigerant can be quickly discharged while being not run to the other region of the surface along the heat removal object. Note that, in FIG. 8E, it is possible to say that the end face of the channel is arranged along the heat removal object. In other words, the heat removal use channel of the present invention does not have to be a channel through which the gas state refrigerant flows in the direction (y-direction) along the heat removal object. The gas state refrigerant discharged from the discharge ports 83 a flows into, for example, a pipe or rectangular duct and flows to the condensation portion and subcooling portion.
FIG. 9A to FIG. 9E are perspective views showing modifications of the wall portion partitioning the heat removal use channel and the liquid supply use channel (see wall portion 47 of FIG. 6A, wall portion 55 of FIG. 6D, etc.) and communicating holes.
In the modification of FIG. 9A, a plurality of communicating holes 86 are formed in a flat plate shaped wall portion 85. For example, holes are formed by punching a metal plate or plastic plate. In this modification, the wall portion having communicating holes can be easily formed, and change of design of positions (for example, intervals of the plurality of communicating holes), sizes, and shapes of the communicating holes is easy.
In the modification of FIG. 9B, a wall portion 88 is formed by a porous member. The porous member is, for example, a sintered metal. A filtration size of the porous member can be appropriately set according to, for example, the amount of supply to the heat removal use channel. It is, for example, 1 μm to 200 μm. Note that, in the conventional technique of running a liquid state refrigerant through the heat removal use channel, even when the main channel and the sub channel are partitioned by a porous member, a sufficient amount of the liquid state refrigerant cannot be supplied from the sub channel to the main channel. Note that a pore portion of the porous member is an example of the refrigerant passage portion of the present invention.
In the modification of FIG. 9C, one slit 90 is provided extending along the longitudinal direction of a wall portion 89. In this modification, by supplying the liquid state refrigerant into the heat removal use channel within a predetermined range of the flow direction of the heat removal use channel by the slit 90 and forming a liquid film over a predetermined range, the same effects as those by the case of supplying the liquid state refrigerant to a plurality of positions are obtained.
As shown in FIG. 9A, where communicating holes are formed by punching etc., the sizes, shapes, and arrangement positions of the communicating holes can be appropriately changed. For example, the sizes, shapes, and positions of the communicating holes may be made uneven, unequal, and so on. The positions and numbers of communicating holes and grooves formed in the inner circumferential surface of the heat removal use channel in the direction perpendicular to the channel do not have to be the same. In the modification shown in FIG. 9D, in a liquid supply use channel 91, a plurality of communicating holes 92 are provided from one end 91 a, through which the liquid state refrigerant is poured, to the other end 91 b. These communicating holes 92 are formed so that their diameters become larger toward the other end 91 b side. There are cases that the liquid state refrigerant can be supplied to the heat removal use channel with a uniform flow rate over the entire length from the upstream side to the downstream side of the liquid supply use channel 91 by this.
Further, in the modification shown in FIG. 9E, communicating holes 95 are formed so that the pitch of the communicating holes 95 becomes smaller toward the end portion 94 a and end portion 94 b sides of the liquid supply use channel 94. There are cases that the liquid state refrigerant can be supplied to the heat removal use channel with a uniform flow rate over the entire length from the upstream side to the downstream side of the liquid supply use channel 94 by this.
FIG. 15A and FIG. 15B are diagrams explaining the amount of supply of the liquid state refrigerant from the liquid supply use channel to the heat removal use channel.
The upper side diagram of FIG. 15A is a plan view showing in a general manner the heat removal use channels 31, 73, and 67 shown in FIG. 2A to FIG. 2C, FIG. 7A, and FIG. 7B. The lower side diagram of FIG. 15A is a diagram showing a pressure P1 of the liquid supply use channel and a pressure P2 of the heat removal use channel at positions in the flow direction in the upper side diagram of FIG. 15A. The upper side diagram of FIG. 15B is a plan view showing in a general manner the heat removal use channel 76 shown in FIG. 7D. The lower side diagram of FIG. 15B is a diagram showing the pressure P1 of the liquid supply use channel and the pressure P2 of the heat removal use channel at positions in the flow direction in the upper side diagram of FIG. 15B.
In the supply of the liquid state refrigerant from the liquid supply use channel (32, 77, etc.) to the heat removal use channel (31, 76, etc.), if it is assumed that a flow resistance of the channel communicating the two (refrigerant passage portion; for example, communicating holes (86, FIG. 9A), a pore portion of a wall portion constructed by a sintered metal or other porous member (88, FIG. 9B), a slit (90, FIG. 9C), or nozzles (65, FIG. 6G)) is uniform along the heat removal use channel, the amount of supply of the liquid flowing in the refrigerant passage portion is determined according to a pressure difference ΔP between the two channels of the liquid supply use channel and the heat removal use channel. Namely, for the inflow of the liquid from the liquid supply use channel to the heat removal use channel, it is indispensable that the pressure of the liquid supply use channel be higher than the pressure of the heat removal use channel. Further, the distribution of flow rates from the liquid supply use channel to the heat removal use channel is determined according to the distribution of pressures of the liquid supply use channel and the heat removal use channel.
A pressure gradient in the liquid supply use channel (32, 77, etc.) is gradually lowered since the flow rate in the liquid supply use channel decreases due to the inflow of the liquid to the heat removal use channel (31, 76, etc.) On the other hand, in the heat removal use channel, the flow rate keeps on increasing. In addition, the single liquid phase changes to the gas and liquid two phases due to the heating. Therefore, the pressure gradient conversely increases.
Accordingly, the pressure difference ΔP between the liquid supply use channel (32, 77, etc.) and the heat removal use channel (31, 76, etc.) is small in the upstream portion of the heat removal use channel, but becomes large in the downstream portion where parallel channels are assumed, therefore the amount of supply from the liquid supply use channel to the heat removal use channel in the upstream portion becomes small, and dry out sometimes easily occurs in the upstream portion.
In order to solve this, it may be considered to change the dimensions, pitch, etc. of the opening portion to make the flow resistance of the channel (refrigerant passage portion) communicating the liquid supply use channel (32, 77, etc.) and the heat removal use channel (31, 76 etc.) small in the upstream portion of the heat removal use channel and large in the downstream portion, and make the amount of liquid supply to the heat removal use channel uniform.
FIG. 16A to FIG. 16F show examples in which the flow resistance of the refrigerant passage portion located at a boundary of the liquid supply use channel and the heat removal use channel is made smaller in the upstream portion of the heat removal use channel and larger in the downstream portion as described above.
FIG. 16A shows a case where the liquid supply use channel and the heat removal use channel of FIG. 15A are communicated by communicating holes 131. The communicating holes 131 are set so that the diameter becomes larger toward the upstream side (right side of the sheet surface) of the liquid supply use channel and the heat removal use channel, so the flow resistance becomes smaller toward the upstream side.
FIG. 16B shows a case where the liquid supply use channel and the heat removal use channel of FIG. 15A are communicated by communicating holes 133. The communicating holes 133 are set so that the pitch becomes smaller toward the upstream side (right side of the sheet surface) of the liquid supply use channel and the heat removal use channel, so the flow resistance becomes smaller toward the upstream side.
FIG. 16C shows a case where the liquid supply use channel and the heat removal use channel of FIG. 15A are communicated by a slit 135. The slit 135 is set so that the width becomes larger toward the upstream side (right side of the sheet surface) of the liquid supply use channel and the heat removal use channel, so the flow resistance becomes smaller toward the upstream side.
FIG. 16D shows a case where the liquid supply use channel and the heat removal use channel of FIG. 15B are communicated by communicating holes 137. The communicating holes 137 are set so that the diameter becomes larger toward the upstream side (center side of the liquid supply use channel 77) of the liquid supply use channel and the heat removal use channel, so the flow resistance becomes smaller toward the upstream side.
FIG. 16E shows a case where the liquid supply use channel and the heat removal use channel of FIG. 15B are communicated by communicating holes 139. The communicating holes 139 are set so that the pitch becomes smaller toward the upstream side (center side of the liquid supply use channel 77) of the liquid supply use channel and the heat removal use channel, so the flow resistance becomes smaller toward the upstream side.
FIG. 16F shows a case where the liquid supply use channel and the heat removal use channel of FIG. 15B are communicated by a slit 141. The slit 141 is set so that the width becomes larger toward the upstream side (center side of the liquid supply use channel 77) of the liquid supply use channel and the heat removal use channel, so the flow resistance becomes smaller toward the upstream side. However, the flow resistance is made relatively larger a little in the center portion where the pressure of the liquid supply use channel locally becomes high due to collision of the inflowing liquid.
Note that, there also exists a case where dry out is caused in the downstream portion where the amount of passage of the generated vapor is large. In this case, the method of increasing the flow rate in the downstream portion as shown in FIG. 9D and FIG. 9E becomes effective.
FIG. 10A to FIG. 10F are diagrams explaining patterns of the inner circumferential surface of the heat removal use channel. In FIG. 10A to FIG. 10D, the liquid state refrigerant is supplied from the liquid supply use channel etc. to the left and right direction of the sheet surface (x-direction). Note that, FIG. 10A is a diagram corresponding to the embodiment shown in FIG. 2A to FIG. 2C.
In the modification of FIG. 10B, in addition to the groove portions 40, a plurality of groove portions 96 extending in a direction perpendicular to the groove portions 40 are provided. By these groove portions 96, the liquid state refrigerant becomes easy to spread also in the direction in which the groove portions 96 are extended, and the liquid film becomes easy to be formed over the entire heat removal use channel. In particular, in a case where the supply positions of the liquid state refrigerant are separated from each other, for example, the case where the liquid state refrigerant is supplied from communicating holes formed in the liquid supply use channel, the refrigerant easily is depleted between the supply positions. However, the liquid state refrigerant is spread also between the supply positions by the groove portions 96, therefore depletion is prevented.
Note that it is also possible to provide only the groove portions 96 without providing the groove portions 40 or possible to provide groove portions obliquely extending with respect to the flow direction and spread the liquid state refrigerant to both of the flow direction and the direction perpendicular to the channel by the groove portions. Zigzag groove portions may be provided as well. Note that the groove portions 40 or groove portions obliquely extending with respect to the channel are examples of groove portions traversing the channel. The groove portions traversing the channel may be ones extended from one sideward end of the channel to the other sideward end or may be ones extended within an appropriate range in the middle between sideward ends.
In the modification of FIG. 10C, a net shaped sheet 98 is adhered to the inner circumferential surface of the heat removal use channel. The sheet 98 is an example of the sheet permeated with the liquid state refrigerant of the present invention. The sheet 98 is formed by, for example, a metal, ceramic, plastic, or fiber. The size and knitted form of the mesh may be appropriately selected in accordance with the type of the refrigerant etc. In this modification, the refrigerant is sucked into the sheet 98 and spreads on the inner circumferential surface of the heat removal use channel. Due to this, the liquid film is evenly formed over the entire inner circumferential surface.
In the modification of FIG. 10D, a sheet 100 formed by a porous member is adhered to the inner circumferential surface of the heat removal use channel. The sheet 100 is an example of a sheet permeated with the liquid state refrigerant of the present invention. The sheet 100 is constructed by for example a sintered metal. In the sheet 100 as well, the same effect as that of the sheet 98 is obtained.
In place of the arrangement of the sheet 100, the inner circumferential surface of the heat removal use channel may be coated, polished, or otherwise roughened so as to roughen the inner circumferential surface and give a liquid film retention function.
FIG. 10E and FIG. 10F show examples of the cross-sectional shapes of the groove portions 40 and groove portions 96. The groove portions 102 shown in FIG. 10E have V-shaped cross-sections, while groove portions 103 shown in FIG. 10F have rectangular cross-sections. FIG. 10E and FIG. 10F are examples. The groove portions 40 and groove portions 96 may be given a U-shape or other various shapes as well.
FIG. 11A to FIG. 11C show a modification of extension of the heat removal use channel to the width direction of the channel, in which FIG. 11A is a perspective view of an outer appearance of a heat removal portion 105, FIG. 11B is a cross-sectional view taken along an XIb-XIb arrow direction of FIG. 11A, and FIG. 11C is a cross-sectional view taken along an XIc-XIc arrow direction of FIG. 11A.
In the heat removal portion 105 in FIG. 11A to FIG. 11C, pipes 107A, 107B, and 107C (hereinafter, simply referred to as “pipes 107”, these sometimes not discriminated) having branch portions are inserted in a rectangular cross-section hollow body 106 at the two sides and center to separate it into sections where by two heat removal use channels 109A and 109B (hereinafter, simply referred to as “heat removal use channels 109”, these sometimes not discriminated) are formed. Further, in the pipes 107A, 107B, and 107C, liquid supply use channels 110A, 110B, and 110C (hereinafter, simply referred to as “liquid supply use channels 110”, these sometimes not discriminated) are formed in their internal portions. The pipes 107 are provided with a plurality of not shown communicating holes communicating the heat removal use channels 109 and the liquid supply use channels 110 along the flow direction of the heat removal use channels 109.
In the each heat removal use channel 109, in the same way as the heat removal use channels shown in FIG. 2A etc., the liquid state refrigerant is supplied from the liquid supply use channels 110 arranged on the two sides of the heat removal use channel 109 via not shown communicating holes, whereby a liquid film of the refrigerant is formed. Note, the liquid supply use channel 110B at the center supplies the liquid state refrigerant to both of the heat removal use channels 109A and 109B on the two sides thereof. The gas state refrigerant evaporated in the heat removal use channels 109 is discharged from the heat removal use channels 109, then merged.
In the modification of FIG. 11A to FIG. 11C, the heat removal use channel is divided into a plurality of heat removal use channels 109 in the width direction of the channel, therefore the heating length in the width direction becomes shorter, and the depletion of the liquid state refrigerant is prevented. In other words, it becomes possible to extend the heat removal use channel to the width direction. In the two heat removal use channels 109A and 109B, the liquid supply use channel 110B is shared, so the number of parts is decreased. The two heat removal use channels 109A and 109B are partitioned by the liquid supply use channel 110B, so the influences of the heat removal use channels 109A and 109B on each other are eased.
FIG. 12A to FIG. 12C show a modification wherein the heat removal use channel is enlarged in the flow direction, in which FIG. 12A is a perspective view of the outer appearance of a heat removal portion 112, FIG. 12B is a cross-sectional view taken along an XIIb-XIIb arrow direction of FIG. 12A, and FIG. 12C is a cross-sectional view taken along an XIIc-XIIc arrow direction of FIG. 12A.
In the heat removal portion 112 in FIG. 12A to FIG. 12C, pipes 115A, 115B, and 115C (hereinafter, simply referred to as “pipes 115”, these sometimes not discriminated) having pluralities of branch portions are inserted in a rectangular cross-section hollow body 114 at the two sides and center to separate it into sections where by two heat removal use channels 116A and 116B (hereinafter, simply referred to as “heat removal use channels 116”, these sometimes not discriminated) are formed. Further, in the pipes 115A, 115B, and 115C, liquid supply use channels 117A, 117B, 117C (hereinafter, simply referred to as “liquid supply use channels 118”, these sometimes not discriminated) are formed in their internal portions. The pipes 115 are provided with a plurality of not shown communicating holes communicating the heat removal use channels 116 and the liquid supply use channels 117 along the flow direction of the heat removal use channels 116.
The heat removal use channels 116 are partitioned into pluralities of sections D1, D2, and D3 in the flow direction (y-direction). The plurality of sections D1 to D3 are provided with discharge ports 119A, 119B, and 119C which are opened sideward in the channels, for example, to the opposite side of the heat removal object HO, to discharge the refrigerant in the gas state. In each section, a liquid film is formed by the refrigerant supplied from the liquid supply use channels 117, and the evaporated refrigerant is discharged from discharge ports 119A to 119C. Note that, the liquid supply use channels 117 may be communicated over all sections D1 to D3 as shown in FIG. 12B, or may be partitioned into pluralities of sections in the same way as the heat removal use channels 116.
In this modification, by partitioning the heat removal use channels 116 in the flow direction, the heat removal efficiency of the sections D1 to D3 is raised by enabling the discharge of the evaporated refrigerant in an early period, and the influences of the sections on each other can be eased. In other words, the heat removal use channel, i.e., heat removal surface, can be made long without limit. In addition, it is not necessary to partition the liquid supply use channels 117 matching with the sections D1 to D3, so no design change is required. Note that, in the technique of running the liquid state refrigerant as in the conventional case, the pressure loss was large if the heat removal use channel was partitioned in the flow direction, the load of the pump increased, and also a drop of the cooling efficiency was caused, therefore the extension to the flow direction was difficult.
FIG. 13 is a diagram showing a modification of the overall construction of the heat removal apparatus. Note that the same notations are attached to common portions to those of the heat removal apparatus 1 of FIG. 1. In the heat removal apparatus of FIG. 13, the gas and liquid phase separator 19 and the subcooling portion 21 are omitted. Accordingly, the evaporated refrigerant completely returns to the liquid inside the condensation portion 14, and the heat quantity Q from the heat removal object will be completely released to the atmosphere in the condensation portion 14.
FIG. 17 is a diagram showing an example of application of the present invention.
An automobile 151 has a power controller 153 as the heat removal object and a heat removal apparatus 155.
The heat removal apparatus 155 has a construction resembling that of the heat removal apparatus 1 explained above. Specifically, the heat removal apparatus 155 has an auxiliary liquid tank 157 (corresponding to the storage tank 3) storing the liquid state refrigerant, a pump 159 (corresponding to the pump 5) pumping out the liquid state refrigerant, a heat removal portion 161 (corresponding to the heat removal portion 12) removing the heat of the power controller 153 by the liquid state refrigerant pumped out by the pump 159, a radiator 163 (corresponding to the condensation portion 14) condensing the gas state refrigerant flowing out of the heat removal portion 161, and a gas and liquid phase separator 165 (corresponding to the gas and liquid phase separator 19) separating the refrigerant flowing out of the radiator 163 to the gas state refrigerant and the liquid state refrigerant. The liquid state refrigerant separated by the gas and liquid phase separator 165 is pumped out by the pump 159. The liquid state refrigerant pumped out by the pump 159 is controlled in the flow rate to the auxiliary liquid tank 157 and heat removal portion 161 by a flow rate control unit 160.
The heat removal portion 161 has, although not particularly shown, a heat removal use channel provided adjacent to the power controller 153 in the same way as the heat removal portion 12. At a plurality of positions (within a predetermined range) in a predetermined direction of the heat removal use channel, the liquid state refrigerant is supplied into the heat removal use channel, whereby a liquid film of the refrigerant is formed over the plurality of positions (predetermined range) on the inner circumferential surface of the heat removal use channel. The power controller 153 is cooled by the evaporation of the liquid film.
At the time of application to an automobile, the temperature difference between a permissible temperature of the power controller (about 100° C.) and a temperature of open air to which a waste heat is released (about 30° C.) is small, and the required temperature difference of the heat removal portion can be kept smaller than that by the usual boiling cooling by liquid film evaporation, therefore the heat removal capability of the overall cooling system can be raised.
FIG. 18 is a diagram showing another example of application of the present invention.
A power transformation system 171 is a system provided in, for example, a generating station or factory for transforming voltage etc. The power transformation system 171 has a plurality of power elements 173 as the heat removal object and a heat removal apparatus 175.
The heat removal apparatus 175 has a construction resembling that of the heat removal apparatus 121 explained above. Specifically, the heat removal apparatus 175 has a pump 177 (corresponding to the pump 5) pumping out the liquid state refrigerant, a plurality of heat removal portions 179 (corresponding to the heat removal portion 12) removing the heat of the plurality of power elements 173 by the liquid state refrigerant pumped out by the pump 177, and an air cooling unit 181 (corresponding to the condensation portion 14) condensing the gas state refrigerant flowing out of the heat removal portions 179. The refrigerant flowing out of the air cooling unit 181 is pumpede out by the pump 177.
The plurality of power elements 173 and plurality of heat removal portions 179 construct a power element cooling train 183 by alternately stacking of one heat removal portion 179 and two power elements 173. A plurality of power element cooling trains 183 are thereby provided. In each power element cooling train 183, power elements 173 are arranged on both sides of one heat removal portion 179, so heat removal of two power elements 173 by one heat removal portion 179 becomes possible.
The plurality of power element cooling trains 183 and the plurality of heat removal portions 179 in the power element cooling trains 183 are connected parallel to each other. Namely, the heat removal apparatus is constructed so that the liquid state refrigerant pumped out from the pump 177 is separated and flows into each power element cooling train 183 and is further separated in each power element cooling train 183 and flows to each heat removal portion 179.
Each heat removal portion 179 has, although not particularly shown, a heat removal use channel provided adjacent to the power element 173 in the same way as the heat removal portion 12. At a plurality of positions (within a predetermined range) in a predetermined direction of the heat removal use channel, the liquid state refrigerant is supplied into the heat removal use channel, whereby a liquid film of the refrigerant is formed over the plurality of positions (predetermined range) on the inner circumferential surface of the heat removal use channel. The power element 173 is cooled by the evaporation of the liquid film.
FIG. 19A and FIG. 19B are graphs explaining effects of the present invention. FIG. 19A is a graph showing a heat transmission characteristic obtained by experiments in the heat removal apparatus of an example of the present invention. FIG. 19B is a graph showing the heat transmission characteristic of FIG. 19A in comparison with the heat transmission characteristic in the prior art. In FIG. 19A and FIG. 19B, the abscissas indicate temperature differences ΔT (K) between the heat removal object surface (one surface constructing the heat removal use channel) of the heat removal object and the liquid state refrigerant flowing into the heat removal use channel, while the ordinates indicate heat fluxes q (W/cm²) on the heat removal object surface of the heat removal object. Further, heat transmission ratios a (W/m²K) are shown in graphs.
In FIG. 19A and FIG. 19B, circular marks M1 indicate values at the upstream position in the flow direction and the center position in the width direction of the heat removal use channel in the heat removal apparatus as an example of the present invention, rectangular marks M2 indicate values at the center position in the flow direction and the center position in the width direction of the heat removal use channel in the heat removal apparatus as an example of the present invention, and triangular marks M3 indicate values at the downstream position in the flow direction and the center position in the width direction of the heat removal use channel in the heat removal apparatus as an example of the present invention.
In the heat removal use channel of the heat removal apparatus as an example of the present invention, grooves are formed in the inner circumferential surface. Further, a heat spreader is not provided. The subcooling of the liquid (difference from the saturation temperature) at an inlet of the heat removal use channel is 15K. A volume flow rate of the liquid refrigerant is 4.5 liters/min. One side of the liquid supply use channel is closed. A void width (clearance between the heat removal object surface and the facing heat insulation surface) of the heat removal use channel is 5 mm. The width of the heat removal use channel×length (flow direction) is 30 mm×150 mm.
As understood from FIG. 19A and FIG. 19B, in the heat removal apparatus of the example of the present invention, even in the case where a heat spreader is not provided, cooling with a heat flux higher by 1 order than that by the water cooling system equipped with a heat spreader is accomplished. In addition, a heat generating area which can be cooled is larger by 2 orders, and a high heat transmission ratio is obtained by the liquid film evaporation, therefore the temperature difference between the heat removal object surface and the fluid is sufficiently small.
The present invention is not limited to the above embodiments and modifications and may be executed in various ways.
The heat removal object need only have a higher temperature than the saturation temperature of the refrigerant, may be a heat generating object releasing heat such as a power element, motor, or battery, or may be a heat transmission object transmitting the heat of a heat generating object such as a heat spreader. It may be any of a gas, liquid, or solid.
The heat removal use channel may be formed by using an appropriate material, shape, and dimensions so far as it is provided adjacent to the heat removal object. Whatever the case, the heat is transmitted to the heat removal use channel from the heat removal object so far as the heat removal use channel is adjacent to the heat removal object. This means that the channel is thermally connected to the heat removal object.
The plurality of positions at which the supply of the liquid state refrigerant to the heat removal use channel is made are not limited to ones aligned in the flow direction. So far as the liquid state refrigerant is supplied to the plurality of positions and a liquid film is formed over the plurality of positions, the plurality of positions may be provided in a direction perpendicular to the channel as well. Note that, it is preferable that a portion where the depletion of liquid occurs is not formed within the range over the plurality of positions. However, even if the depletion occurs at a portion, it can be said that a liquid film is formed over the plurality of positions if the liquid state refrigerant is supplied to the plurality of positions, and a state where the liquid state refrigerant is filled in the range over the plurality of positions (the liquid state refrigerant is filled in the heat removal use channel) as in the conventional technique of running the liquid state refrigerant is not exhibited.

Claims

1. A heat removal method comprising removing heat of a heat removal object by supplying a liquid state refrigerant into a heat removal use channel, which is provided to extend along the heat removal object and has a longer channel length than width of a surface along the heat removal object, from an opening, which opens towards inside of the heat removal use channel in a side wall of the heat removal channel at a side of a plate shaped member forming the surface along the heat removal object of the heat removal use channel and abutting against the heat removal object, in a predetermined range in the flow direction of the heat removal use channel, forming a liquid film of the refrigerant over the predetermined range on the inside surface of the plate shaped member, making the liquid film evaporate by the heat from the heat removal object, and discharging the evaporated refrigerant from the heat removal use channel.

2. A heat removal method as set forth in claim 1, supplying the liquid state refrigerant at a plurality of positions over the predetermined range.

3. A heat removal method comprising removing heat of a heat removal object by supplying a liquid state refrigerant into a heat removal use channel, which is provided adjacent to the heat removal object, in a predetermined range of a flow direction of said heat removal use channel, forming a liquid film of the refrigerant over the predetermined range on an inside surface of a plate shaped member forming said heat removal use channel and abutting against the heat removal object, making the liquid film evaporate by the heat from the heat removal object, and discharging the evaporated refrigerant from the heat removal use channel, wherein

In said supplying the liquid state refrigerant into the heat removal use channel, the refrigerant is supplied from an opening formed at an outer circumference, which sticks out into the heat removal use channel toward the plate shaped member, of a liquid supply channel, which extends along the heat removal channel, and opening towards inside surface of the plate shaped member.

4. A heat removal apparatus comprising:

a heat removal use channel provided to extend along a heat removal object and having a longer channel length than width of a surface along the heat removal use channel; and

a liquid supply portion constructed to supply a liquid state refrigerant into the heat removal use channel from an opening, which opens towards inside of the heat removal use channel in a side wall of the heat removal channel at a side of a plate shaped member forming the surface along the heat removal object of the heat removal use channel and abutting against the heat removal object, in a predetermined range in the flow direction of the heat removal use channel, form a liquid film of the refrigerant over the predetermined range on the inside surface of the plate shaped member, make the liquid film evaporate by the heat from the heat removal object, and discharge the evaporated refrigerant from the heat removal use channel.

5. A heat removal apparatus as set forth in claim 4, wherein the opening opens at a position nearer the plate shaped member than the surface of the heat removal use channel facing the plate shaped member.

6. A heat removal apparatus as set forth in claim 4, wherein said opening is provided at each of two side walls facing each other, and

said liquid supply portion can also supply the liquid state refrigerant from a second opening, which opens towards the plate shaped member, of a projecting part projecting out from a surface facing the plate shaped member of the heat removal use channel toward the plate shaped member between the two side walls.

7. A heat removal apparatus as set forth in claim 4, wherein a mass ratio of a flow rate of the evaporated refrigerant with respect to the total flow rate of the refrigerant in the heat removal use channel is equal to or larger than 0.2.

8. A heat removal apparatus as set forth in claim 7, comprising:

a control unit controlling a rate of supply of the liquid state refrigerant to the heat removal use channel to approach a target value set so that the mass ratio becomes equal to or larger than 0.2.

9. A heat removal apparatus as set forth in claim 4, wherein the liquid supply portion supplies the liquid state refrigerant at a plurality of positions over the predetermined range.

10. A heat removal apparatus as set forth in claim 4, wherein the liquid supply portion has a liquid supply use channel which extends along said heat removal use channel at a side of the plate shaped member and is partitioned from said heat removal use channel by said side wall, and the opening is constructed to allow passage of the liquid state refrigerant from the liquid supply use channel to the heat removal use channel.

11. A heat removal apparatus as set forth in claim 4, wherein the heat removal use channel is partitioned to a plurality of sections in the flow direction, and the plurality of sections each are provided with discharge ports discharging the gas state refrigerant.

12. A heat removal apparatus as set forth in claim 4, wherein the heat removal use channel has discharge ports of the refrigerant provided at both ends in the flow direction.

13. A heat removal apparatus as set forth in claim 4, wherein the inside surface of the plate shaped member is provided with groove portions to which the liquid state refrigerant is stuck by surface tension to spread the film of the refrigerant to the inside surface.

14. A heat removal apparatus as set forth in claim 13, wherein the groove portions extend in a direction traversing the heat removal use channel.

15. A heat removal apparatus as set forth in claim 13, wherein the groove portions extend in a direction along the heat removal use channel.

16. A heat removal apparatus as set forth in claim 4, wherein the inside surface of the plate shaped member is lined by a sheet through which the liquid state refrigerant can permeate and spreading the film of the refrigerant to the inside surface.

17. A heat removal apparatus as set forth in claim 4, wherein the inside surface of the plate shaped member is roughened.

18. A heat removal apparatus comprising:

a heat removal use channel provided adjacent to a heat removal object; and

a liquid supply portion constructed to supply a liquid state refrigerant into the heat removal use channel in a predetermined range of a flow direction of the heat removal use channel and form a liquid film of the refrigerant over the predetermined range at an inside surface of a plate shaped member forming the heat removal use channel and abutting against said heat removal object, wherein

said liquid supply portion has a liquid supply use channel extending along said heat removal use channel, having an outer circumference sticking out into the heat removal use channel toward the plate shaped member, being formed with an opening which opens toward the plate shaped member in the outer circumference, and supplying liquid state refrigerant from the opening to the heat removal use channel.