JP2008016613A - Cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling system which degrades no heat radiation performance even if a microchannel is miniaturized, and has a high heat transfer coefficient. <P>SOLUTION: The cooling system comprises: a first main flow channel thermally connected to a first heat generator 1; a second main flow channel connected to a downstream side of the first main flow channel and thermally connected to a second heat generator; a plurality of fins 3 thermally connected to the inner wall of the first main flow channel by leaving a space; a plurality of fins 3 thermally connected to the inner wall of the second main flow channel by leaving a space; and a first refrigerant outflow channel 5 formed in the vicinity of the connection part of the fin 3 of the first main flow channel and making a part of the refrigerant flow in the first main flow channel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cooling device for cooling a heating element.

Conventionally, there is a liquid cooling type cooling device that cools a semiconductor device (heating element) mounted on a wiring board with a large computer or the like (Patent Document 1). In this liquid cooling type cooling device, a microchannel is formed in a flow path for introducing a refrigerant, and the refrigerant flowing out through the flow path collides with a wall surface through a single space. The refrigerant is introduced into and discharged from another flow path in which the microchannel is formed.

Non-Patent Document 1 describes a technique in which heat transfer is increased from the wall surface constituting the microchannel to the refrigerant when the microchannel is formed in the flow path. When the flow path becomes narrower, the temperature boundary layer becomes thinner, so a high heat transfer coefficient can be realized, and the fin surface area that comes into contact with the refrigerant per unit cross-sectional area of the flow path by forming thin fins for forming microchannels Therefore, the heat transfer rate can be further improved.
JP 2003-318343 A DBTuckerman, RFPease, High Performance Heat Sinking for VLSI, 1981, IEEE EDL-2 (5), pp.126-129.

When the microchannel is provided in the flow path through which the refrigerant flows, the heat transfer coefficient can be improved.

However, as described above, when the number of fins is increased to increase the fin surface area in contact with the refrigerant per unit cross-sectional area of the flow path, and as a result, the fin spacing is reduced, the surface of the fin is compared with the ability to transfer heat to the fins. Therefore, the so-called fin efficiency is reduced, and a temperature gradient is generated in which the temperature of the refrigerant flowing near the fin connection is higher than the temperature of the refrigerant flowing further away. The temperature gradient of the refrigerant in the flow path has a problem that the heat transfer coefficient from the fin to the refrigerant is lowered.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a cooling device having a high heat transfer rate without reducing heat dissipation performance even when the microchannel is miniaturized.

In order to solve the above problem, the present invention includes a first main flow channel thermally connected to the first heating element,
A second main channel connected to the downstream side of the first main channel and thermally connected to a second heating element;
A plurality of fins that are thermally connected to the inner wall of the first main flow path and spaced apart from each other;
A plurality of fins that are thermally connected to the inner wall of the second main flow path at a distance from each other;
A cooling device, comprising: a first refrigerant outflow passage formed near the fin connection portion of the first main flow path and allowing a part of the refrigerant flowing through the first main flow path to flow out. provide.

At this time, a refrigerant inflow path formed near the fin connection portion of the second main flow path and allowing the refrigerant to flow into the second main flow path may be provided.

A second refrigerant outflow path formed in the vicinity of the fin connection portion of the second main channel on the downstream side of the refrigerant inflow channel and allowing a part of the refrigerant flowing through the second main channel to flow out; You may have.

Moreover, it further comprises a heat exchanger,
The first refrigerant flowing through the first refrigerant outflow path and the second refrigerant outflow path is merged and flows into the heat exchanger, and the second refrigerant from the second main flow path is the first refrigerant. You may flow in into the said heat exchanger from the downstream rather than a refrigerant | coolant.

Moreover, you may comprise the thermoelectric element formed in the position into which the said 1st refrigerant | coolant of the said heat exchanger flows in.

The heating element is a semiconductor element, and a direction in which the refrigerant flows in the first main flow path and the second main flow path is in a direction along a substrate surface that electrically connects the semiconductor element. It may be provided.

The present invention can provide a cooling device with high thermal conductivity without reducing heat dissipation performance by relaxing the temperature distribution of the refrigerant flowing through the flow path.

Hereinafter, detailed embodiments of the invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and can be used in various ways without departing from the spirit of the present invention.

  FIG. 1 shows a block diagram of a cooling device according to an embodiment of the present invention.

  FIG. 1A is a view of the flow channel as viewed from above, and FIG. 1B is a view as viewed from the side.

As shown in FIG. 1, the cooling device includes a semiconductor element 1 that is a heating element, and the semiconductor element 1.
And a heat receiving portion 2 which is a main flow path connected to the. Fins 3 are connected to the inner wall of the heat receiving portion 2 with a space therebetween to form a microchannel. A refrigerant outlet 5 and a refrigerant inlet 6 are formed in the vicinity of the connection portion between the fin 3 and the heat receiving portion 2.

The white arrows in FIG. 1 indicate the direction in which the refrigerant flows, and the refrigerant outlet 5 is located upstream of the refrigerant inlet 6 with respect to the main flow path. A substrate 7 for electrical input / output is connected to the semiconductor element 1. The refrigerant outlet 5 and the refrigerant inlet 6 are provided at the bottom of the heat receiving portion 2 to which the semiconductor element 1 is attached, and a flow path is formed through the substrate 17.

The direction in which the refrigerant flows in the main flow path is provided in a direction along the surface of the substrate 17 that electrically connects the semiconductor element 1. By doing so, the substrate to which the cooling device is attached can be provided as a flat plate-like module, and the effect of reducing the substrate interval when a plurality of substrates are used side by side can be achieved.

In this cooling device, a plurality of semiconductor elements 1 are connected in series to a flow path (heat receiving portion 2) having a microchannel structure therein. In the flow path (heat receiving part 2), the upstream side is the first main flow path 20 and the downstream side is the second main flow path 21.

Inside the first main flow path 20 and the second main flow path 21 of the heat receiving section 2, fins 3 are arranged at the bottom so as to have a thickness of 10 to several hundred micrometers and a gap of 10 to several hundred micrometers. It is connected. The heat receiving portion 2 is made of a metal having high thermal conductivity such as a copper alloy or an aluminum alloy, and the fins 3 are integrally formed with the heat receiving portion 2 by wire cutting or etching.

Here, the semiconductor element 1, which is a heating element, is thermally connected to the bottom of the heat receiving unit 2. For example, water flows as a refrigerant in the main flow path of the heat receiving unit 2, and heat generated in the semiconductor element 1 is given to the refrigerant via the fins 3.

As described above, the refrigerant outlet 5 is provided at the root of the fin 3 downstream of the first main channel 20, and the refrigerant inlet 6 is provided at the root of the fin 3 upstream of the second main channel 21. ing. From the refrigerant outlet 5, the refrigerant whose temperature has risen through the vicinity of the roots of the fins 3 of the first main flow path 20 (the portion whose temperature is higher than the refrigerant flowing in the upper part of the main flow path) is the heat receiving portion 2. The refrigerant having a low temperature flows into the second main channel 21 from the refrigerant inlet 6 instead.

Although the fin base side is expressed as “down” and the fin tip is expressed as “up”, this represents the top and bottom of the figure regardless of the direction of gravity, and the cooling device may be installed in any direction with respect to gravity.

FIG. 2 is a graph obtained by simulating the temperature distribution of the refrigerant by the cooling device shown in FIG. The horizontal axis indicates the position in the height direction where the root of the fin 3 is 0.0 and the tip of the fin 3 is 1.0 (cm), and the vertical axis indicates the refrigerant at the entrance (broken line) of the second main channel 21. The temperature rise of the refrigerant with respect to the temperature, and the temperature rise of the fins 3 (thin solid line) in the first main flow path 20 and the fins 3 (thick solid line) in the second main flow path 21 are the calorific values of the semiconductor element 1 that is a heating element. Plotted as divided values.

The fin 3 was made of copper having a thickness of 200 μm, a pitch of 400 μm, and a height of 10 mm. Also,
Water is used as the refrigerant, and the refrigerant flow rate is 500 cc / min. The area of the fin 3 corresponding to the upstream semiconductor element 1 (area of the first main flow path 20) is the first stage, and the area of the fin 3 corresponding to the downstream semiconductor element 1 (area of the second main flow path 21). ) Is marked as the second stage. The temperature of the fin 3 is the average temperature at each height of the fin 3 of the first stage (thin solid line) and the second stage (thick solid line) corresponding to each semiconductor element 1, and the flow rate of the refrigerant is the height of the fin 3. It is assumed that the direction is constant. The temperature on the base side of the fin 3 increases along with the temperature of the refrigerant that passes through the first-stage fin 3 and flows into the second-stage fin 3, and the temperature decreases toward the tip of the fin 3.

FIG. 3 is a graph showing the result of simulation under the same conditions as in FIG. 2 in the cooling device having the refrigerant outlet 5 and the refrigerant inlet 6 as shown in FIG. In the configuration shown in FIG. 11, the same parts as those in FIG.

In the simulation of FIG. 2, 80% of the amount of refrigerant is the first main channel 20 of the heat receiving unit 2.
The refrigerant whose temperature has risen from the refrigerant outlet 5 flows out by 20%, and the refrigerant whose temperature has not risen from the refrigerant inlet 6 flows by 20%.

Here, in the simulation of FIG. 2, 80% of the refrigerant flows into the first main flow path 20 of the heat receiving unit 2, and 20% of the refrigerant whose temperature has increased from the refrigerant outlet 5 flows out. 20% of the same amount of refrigerant whose temperature has not risen is introduced from the inlet 6.

In the simulation of FIG. 3, 100% of the refrigerant flows into the heat receiving unit 2.

That is, in the simulations of FIG. 2 and FIG. 3, the total flow rate of the refrigerant flowing into the heat receiving unit 2 is made the same.

As shown in the graphs of FIGS. 2 and 3, the root of the fin 3 at the first stage (thin solid line, horizontal axis is 0.0).
The temperature rise at the position of FIG. 2 is substantially the same as 0.155 K / W in FIG. 2 and 0.154 K / W in FIG. The temperature rise at the base of the second-stage fin 3 (thick solid line, position where the horizontal axis is 0.0) is 0 in FIG.
176 K / W, FIG. 3 is 0.202 K / W, and FIG. 2 is smaller than FIG.

2 and FIG. 3, the average value of the temperature rise at the roots of the fins 3 in the first and second stages (the position where the horizontal axis is 0) is calculated as 0.168 K / W in FIG. It can be seen that 0.178 K / W and FIG. 2 are smaller.

Thus, it can be seen that the cooling device shown in FIG. 1 has a higher average cooling performance and at the same time the maximum value of the root temperature of the fin 3 is lower.

FIG. 4 shows the fins 3 of the first main flow path 20 and the second main flow path 21 when the amount of refrigerant exchanged in the refrigerant outlet 5 and the refrigerant inlet 6 is changed in the cooling device shown in FIG.
It is the graph which plotted the change of the average value of the temperature rise of the root of. The horizontal axis represents the refrigerant replacement amount at the refrigerant outlet 5 and the refrigerant inlet 6, and the vertical axis represents the inlet of the heat receiving unit 2 (first main flow path 20
The value obtained by dividing the average of the temperature rise of the refrigerant and the temperature rise of the fins 3 with respect to the refrigerant temperature at the inlet) is divided by the amount of heat generated per semiconductor element 1 as a heating element.

As described with reference to FIGS. 2 and 3, the refrigerant replacement rate was changed so that the total flow rate of the refrigerant was constant. The refrigerant replacement rate of 20% is the same as that simulated in FIG.
Further, for example, when the refrigerant replacement rate is 10%, 90% of the refrigerant flows in from the first main flow path, 10% of the refrigerant flows out of the refrigerant outlet 5 and 10% from the refrigerant inlet 6 It is set as a condition that a constant (100%) amount of refrigerant always flows into the heat receiving section 2 so that a% amount of refrigerant flows.

As shown in FIG. 4, it can be seen that the temperature rise value has a minimum value when the refrigerant replacement amount is in the vicinity of 20 to 30%.

Moreover, although FIG. 1 demonstrated the case where the semiconductor element 1 which is a heat generating body was located in a line in series,
More than three semiconductor elements 1 may be arranged. At this time, the refrigerant outlet 5 and the refrigerant inlet 6 may be provided for each semiconductor element 1 or every plural semiconductor elements 1.

  Next, FIG. 5 shows a block diagram of a cooling device according to another embodiment of the present invention.

In FIG. 1, the outflow and inflow directions of the refrigerant outlet 5 and the refrigerant inlet 6 are defined as the substrate 1 of the semiconductor element 1.
7 is different from that of FIG. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 5, the fin 3 is provided corresponding to each of the plurality of semiconductor elements 1 that are heating elements. When the distance between the plurality of semiconductor elements 1 is large, the surface temperature tends to decrease not only in the height direction of the fin 3 but also in the lateral direction (the direction in which the refrigerant in the main channel flows).

Therefore, as shown in FIG. 5, even if the length of the fin 3 is shorter than that of FIG. On the other hand, the pressure loss of the refrigerant flowing through the flow path can be reduced by reducing the length of the fin 3.

Further, since the refrigerant outlet 5 and the refrigerant inlet 6 are attached to the surface of the substrate 17 substantially in parallel, there is an advantage that it is not necessary to provide a hole in the substrate 17. Further, a wall 23 is formed between the refrigerant outlet 5 and the refrigerant inlet 6 so that the high-temperature refrigerant flowing through the first main flow path 20 and the low-temperature refrigerant supplied from the refrigerant inlet 6 are unlikely to be mixed. is doing.

  Next, FIG. 6 shows a block diagram of a cooling device according to another embodiment of the present invention.

In FIG. 1, the first main flow path 20 and the second main flow path 21 are connected by a pipe 22, and the outflow and inflow directions of the refrigerant outlet 5 and the refrigerant inlet 6 are defined as the first main flow path 20 and the second main flow path 21. The point provided in the direction along 2 main flow paths differs. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 6, this cooling device is provided with one heat receiving portion 2 for each semiconductor element 1 which is a heating element. Thus, there is an advantage that it is not necessary to design the heat receiving part 2 according to the arrangement of the semiconductor element 1 by individually assigning the heat receiving part 2 to the semiconductor element 1 and connecting the heat receiving parts 2 between the pipes 22.

FIG. 7 is an overall view of the system of the cooling device. Inside the cooling system, water or an antifreeze liquid in which ethylene glycol or the like is mixed with water to prevent freezing flows as a refrigerant by a pump 11.

In this cooling device system, the low temperature drainage 8 that has passed through the upper layer portion that is not near the root of the fin 3 of the first main flow path 20 flows into the second main flow path 21, and further flows into the low temperature heat exchanger 10. Yes. Further, the high temperature waste water 7 that has passed through the vicinity of the roots of the fins 3 of the first main flow path 20 and the second main flow path 21 flows into the high temperature heat exchanger 9.

The high-temperature heat exchanger 9 and the low-temperature heat exchanger 10 are cooled by the fan 13, and the refrigerant discharged therefrom is temporarily stored in the tank 12. The refrigerant discharged from the tank 12 flows into the first main channel 20 and the second main channel 21 through the pump 11 at a predetermined rate.

The tank 12 serves as a buffer that compensates for the evaporation of the water circulating in the cooling system and absorbs the volume change of the water due to the temperature change.

Further, in this cooling system, the low-temperature waste water 8 discharged through the low temperature portion of the fin 3 inside the heat receiving section 2 is mixed with the water that has passed through the high-temperature heat exchanger 9, and the low-temperature heat exchanger 10 is supplied. pass. Both the high temperature heat exchanger 9 and the low temperature heat exchanger 10 are cooled by blowing air from a fan 13. By doing so, the high temperature heat exchanger 9 can be moved efficiently because the difference between the cooling air temperature sent by the fan 13 and the surface temperature of the high temperature heat exchanger 9 becomes large.

Here, if the heat radiation amount by the high temperature heat exchanger 9 and the low temperature heat exchanger 10 is Q, the temperature rise of the surface of the high temperature heat exchanger 9 with respect to the cooling air is ΔT1, and the temperature rise of the surface of the low temperature heat exchanger 10 is ΔT2, Q = C1ΔT1 + C2ΔT2
Is established. C1 and C2 are often the surface area of the heat exchanger directly connected to the size of the heat exchanger,
This coefficient depends on the air flow rate.

As can be seen from this equation, when ΔT1 is larger than ΔT2, even if the total value of C1 and C2 is the same, Q can be increased by making C1 larger than C2. That is, by making the high-temperature heat exchanger 9 larger than the low-temperature heat exchanger 10, the performance can be improved while maintaining the combined size of the two heat exchangers.

Next, FIG. 8 is an overall system diagram of a cooling device according to another embodiment. The same parts as those in FIG. 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 8, in this cooling system, a thermoelectric element 14 is attached to a pipe line instead of the high temperature heat exchanger 9 described in FIG. The thermoelectric element 14 is heated on one side by the high-temperature drainage 7 and cooled on the other side by the air-cooling fins 15 so that thermoelectric power generation is performed and electric energy can be recovered. By using high temperature drainage, thermoelectric element 1
The temperature difference between the four sides increases, and the amount of power generation can be increased.

FIG. 9 is a detailed view of a portion where the thermoelectric element 14 described with reference to FIG.

As shown in FIG. 9, a thermoelectric element 14 and air cooling fins 15 are attached to the surface of a flat rectangular channel 16. Fins (not shown) are provided inside the rectangular channel 16 to promote heat transfer between the water flowing inside and the channel.

As described above, one side of the thermoelectric element 14 is heated by the high temperature waste water 7 and the other side is cooled by the air cooling fins 15 to generate power. The obtained electrical energy can also be used to drive the fan 13 and the pump 11.

  Next, FIG. 10 shows a block diagram of a cooling device according to another embodiment of the present invention.

1 differs from FIG. 1 in that the refrigerant outlet 5 is formed in the first main channel 20 but the refrigerant inlet 6 is not formed. The same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 10, in this refrigerant device, the relatively low-temperature refrigerant that has flowed through the upper layer portion of the first main channel 20 in the vicinity of the refrigerant outlet 5 flows down to the lower layer unit of the second main channel 21. A down blow fin 24 is provided so as to achieve this. In this way, the relatively high-temperature refrigerant that has flowed through the lower layer of the first main flow path 20 is taken out from the refrigerant outlet 5, and the refrigerant that has flowed through the portion away from the fin 3 root is slightly low. The cooling performance in the second main flow path 21 can be improved by spreading to the base side of the fin 3 downstream of the refrigerant outlet 5.

The block diagram of the cooling device which concerns on embodiment of this invention. The graph which simulated the fin and refrigerant | coolant temperature in the cooling device which concerns on embodiment of this invention. The graph which simulated the fin and refrigerant | coolant temperature in a cooling device. The graph which simulated fin base temperature when changing the refrigerant inflow ratio in the cooling device concerning the embodiment of the present invention. The block diagram of the cooling device which concerns on embodiment of this invention. The block diagram of the cooling device which concerns on embodiment of this invention. The figure for demonstrating the whole system of the cooling device which concerns on embodiment of this invention. The figure for demonstrating the whole system of the cooling device which concerns on embodiment of this invention. The perspective view which shows the electric power generating element and heat exchanger which are used for the system of the cooling device which concerns on embodiment of invention. The block diagram of the cooling device which concerns on embodiment of this invention. The block diagram of a cooling device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor element 2 which is a heat generating body ... Heat receiving part 3 ... Fin 4 ... Refrigerant flow 5 ... Refrigerant outlet 6 ... Refrigerant inlet 7 ... High temperature waste water 8 ... Low temperature waste water 9 ... High temperature heat exchanger 10 ... Low temperature heat exchanger DESCRIPTION OF SYMBOLS 11 ... Pump 12 ... Tank 13 ... Fan 14 ... Thermoelectric element 15 ... Air cooling fin 16 ... Rectangular flow path 17 ... Substrate 20 ... First main flow path 21 ... Second main flow path 22 ... Pipe 23 ... Wall 24 ... For down blow fin

Claims (6)

A first main channel thermally connected to the first heating element;
A second main channel connected to the downstream side of the first main channel and thermally connected to a second heating element;
A plurality of fins that are thermally connected to the inner wall of the first main flow path and spaced apart from each other;
A plurality of fins that are thermally connected to the inner wall of the second main flow path at a distance from each other;
A cooling device, comprising: a first refrigerant outflow passage formed near the fin connection portion of the first main flow passage and allowing a part of the refrigerant flowing through the first main flow passage to flow out. The cooling device according to claim 1, further comprising: a refrigerant inflow passage formed in the vicinity of the fin connection portion of the second main flow path to allow a refrigerant to flow into the second main flow path. A second refrigerant outflow path formed in the vicinity of the fin connection portion of the second main flow path on the downstream side of the refrigerant inflow path, through which a part of the refrigerant flowing through the second main flow path flows out. The cooling device according to claim 2. A heat exchanger,
The first refrigerant flowing through the first refrigerant outflow path and the second refrigerant outflow path is merged and flows into the heat exchanger, and the second refrigerant from the second main flow path is the first refrigerant. The cooling device according to claim 3, wherein the cooling device flows into the heat exchanger from a downstream side of the refrigerant. The cooling device according to claim 4, further comprising a thermoelectric element formed at a position where the first refrigerant flows into the heat exchanger. The heating element is a semiconductor element, and a direction in which the refrigerant flows in the first main flow path and the second main flow path is provided in a direction along a substrate surface that electrically connects the semiconductor elements. The cooling device according to any one of claims 1 to 5, wherein the cooling device is provided.

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