WO2006134659A1

WO2006134659A1 - Liquid-type cooling method and cooling device using latent heat material

Info

Publication number: WO2006134659A1
Application number: PCT/JP2005/011114
Authority: WO
Inventors: Hiroki Uchida; Hideshi Tokuhira; Minoru Ishinabe; Hiroaki Date; Jun Taniguchi
Original assignee: Fujitsu Limited
Priority date: 2005-06-17
Filing date: 2005-06-17
Publication date: 2006-12-21
Also published as: JPWO2006134659A1

Abstract

A liquid-type cooling method includes installing on a heat production body (61) a circulation channel (10) having a heat reception section (11) for receiving heat from the heat production body (61) and also having a heat radiation section (12) for radiating the received heat, and also includes transferring heat of the heat reception section (11) to the heat radiation section (12) by always circulating, as long as the heat production section (61) radiates heat, latent heat storage substances (41A, 41B) in the circulation channel (10).

Description

Specification

Liquid cooling type cooling method and cooling device using latent heat material

Technical field

TECHNICAL FIELD [0001] The present invention relates to a liquid cooling type cooling method and a cooling apparatus for circulating a cooling liquid containing a latent heat material.

Background art

[0002] In natural heat dissipation, an electronic device having an overheated electronic component requires forced cooling. For example, a personal computer will not operate properly unless the installed CPU is cooled to keep the temperature within an appropriate range. In general, electronic equipment uses air-cooled forced cooling.

[0003] In recent years, a liquid cooling method that is superior in cooling capacity as compared with an air cooling method has attracted attention as a method of forced cooling in electronic devices. The liquid cooling method here is a method in which a circulation flow path is provided that passes through a heat receiving portion that receives heat from the heating element and a heat radiating portion that dissipates heat, and the coolant is circulated forcibly by a pump.

[0004] Japanese Unexamined Patent Application Publication No. 2003-314936 discloses a cooling method using a cooling liquid containing a latent heat storage material for liquid cooling forced cooling in electronic equipment. Inclusion of a latent heat storage material increases the heat storage capacity of the coolant and slows the temperature rise of the coolant. The cooling method disclosed in the above publication utilizes this action to minimize the operation of the pump. That is, the temperature TJ of the heat generating part is monitored, and the pump is operated only when the temperature TJ of the heat generating part is higher than the set temperature T1. The set temperature T1 is lower than the upper limit of the allowable temperature range of the component and higher than the melting point Tm of the latent heat storage material. According to this cooling method, the energy consumption of the pump can be reduced.

Patent Document 1: Japanese Patent Laid-Open No. 2003-314936

Disclosure of the invention

[0005] However, in the above cooling method that controls the pump on / off, when the temperature TJ of the heat generating part is higher than the melting point Tm of the latent heat storage material but the pump is off, that is, the temperature TF of the cooling liquid is the latent heat storage. When the melting point of the substance is higher than Tm and lower than the set temperature T1 In this case, only the phase change of the latent heat storage material from the solid phase to the liquid phase occurs, but not the reverse phase change. The pump is not turned on unless all the latent heat storage materials are in the liquid phase and the coolant temperature TF exceeds the set temperature T1. In other words, at the time when forced cooling starts, the heat storage action of the latent heat storage material in which the temperature TF of the coolant is higher than the melting point Tm of the latent heat storage material cannot be used. This means that a heat dissipating part with a high heat dissipating capacity that can sufficiently cope with the sudden increase in calorific value is required.

[0006] The cooling method described above requires a sensor for detecting the temperature TJ of the heat generating portion. In addition, some users have to consider that the human power that makes the pump's operating noise or power feel uncomfortable rather than the operating noise always.

[0007] An object of the present invention is to increase the degree of freedom in the heat radiation design of the circulation flow path through which the cooling liquid flows, in addition to the liquid cooling type forced cooling using the cooling liquid containing the latent heat material.

[0008] A cooling method for achieving the object of the present invention is a liquid cooling method for cooling a heat generating body using a cooling liquid containing a latent heat storage material, and the heat generating element Arranging a circulation channel having a heat receiving part for receiving heat from the body and a heat radiating part for dissipating the received heat, and circulating the latent heat storage material in the circulation channel to radiate the heat of the heat receiving part. Including the transfer to the part. A more preferable cooling method is that the melting point of the latent heat storage material is an upper limit of the allowable operating environment temperature of the heating element, and the temperature of the cooling liquid when the heating value of the heating element is maximum. The difference from the melting point of the latent heat storage material is less than 10 ° C.

[0009] The temperature of the operating environment of the heating element is the upper limit of the allowable range, and the heating value of the heating element is the maximum when the maximum cooling capacity is required for the operation of the heating element. In the cooling method of the present invention, the efficiency of heat reception and heat dissipation in the coolant at this time can be maximized.

[0010] When the temperature of the operating environment is TA, the temperature of the coolant is TF, and the amount of heat received from the heating element is Q, the thermal resistance Rh of the heat dissipation part is expressed by the following equation.

[0011] Rh = (TF-TA) / Q

Transforming this equation yields TF = Rh X Q + TA. That is, the temperature TF of the coolant can be obtained from the thermal resistance Rh, the amount of heat Q, and the temperature TA of the operating environment. Thermal resistance Rh is This is the sum of the thermal resistance R2 of heat conduction from the coolant to the heat radiating part and the thermal resistance R3 of heat conduction from the heat radiating part to the atmosphere, and is an eigenvalue determined by the configuration of the cooling device. The amount of heat Q is an eigenvalue determined by the configuration of the heating element. The operating environment temperature TA is an indefinite force In the above calculation, the upper limit of the temperature range that guarantees the operation of the heating element should be used.

[0012] By selecting a latent heat storage material having a melting point Tm, which is equal to or close to the estimated temperature TF of the coolant obtained by calculation, the solid-state to liquid phase at the heat-receiving unit is selected. It is possible to realize an efficient heat exchange in which the phase change and the phase change from the liquid phase to the solid phase in the heat radiating section are evenly generated. Although it is most desirable that the temperature TF of the coolant and the melting point Tm are equal, U, some differences that need not be exactly equal in practice should be tolerated. Specifically, the use of a latent heat storage material having a melting point Tm within a range of ± 10 ° C. with respect to the temperature TF of the coolant obtained by calculation is included in the present invention.

Brief Description of Drawings

FIG. 1 is a diagram showing a configuration of a cooling device according to the present invention.

FIG. 2 is a diagram schematically showing a phase change of a latent heat storage material in a heat receiving part and a heat radiating part.

FIG. 3 is a diagram showing a relationship between a plurality of temperatures related to cooling and melting points of latent heat storage materials.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] The present invention can be applied to forced cooling of electrical circuit components that generate a large amount of heat, such as integrated circuit chips typified by microprocessors, power transistors, laser diodes, transformers, and lamps.

FIG. 1 shows a configuration of a cooling device 1 according to the present invention. The cooling device 1 is a liquid cooling type forced cooling means including a circulation flow path 10, an air supply fan 20, and a power supply circuit 30. The cooling device 1 is assembled in a device having the electric circuit board 60 and cools the circuit components 61 mounted on the electric circuit board 60. For example, the cooling device 1 is built in a notebook or desktop personal computer, and prevents overheating of circuit components called heat sources such as a CPU including a microprocessor, an arithmetic processor, and a high-speed memory.

The circulation flow path 10 includes a heat receiving part 11, a heat radiating part 12, a reserve tank 13, a pump 14, and pipes 15, 16, 17, and 18. In the cooling device 1, the cooling accommodated in the circulation channel 10 The reject liquid 40 has a latent heat storage function.

[0017] The heat receiving section 11 is made of a metal heat exchange unit having a flow path of a predetermined length inside, and is connected to the circuit component 61 and the heat through a heat conducting material such as silicon grease for reducing heat resistance. Connected. In the heat receiving portion 11, heat is transferred from the circuit component 61 to the coolant 46.

The heat radiating unit 12 is composed of a heat exchange unit including metal fins 121. In the heat dissipating part 12, heat is dissipated from the coolant 40 to the atmosphere.

The reserve tank 13 fills the inside of the heat receiving part 11 and the heat radiating part 12 with the coolant 40 and plays a role of preventing damage to the circulation flow path 10 due to the volume change of the coolant 40.

[0020] The pump 14 is a centrifugal micropump with a built-in DC motor, and forcibly causes the coolant 40 to flow.

[0021] Pipe 15 connects heat receiving part 11 and heat radiating part 12, pipe 16 connects heat radiating part 12 and reserve tank 13 and pipe 17 connects reserve tank 13 and pump 14, and pipe 18 Connects the pump 14 and the heat receiving part 11. As these, a flexible tube made of rubber or other resin, or a hard bag represented by a copper bar can be used.

The blower fan 20 forcibly convects the atmosphere around the fins 121 in order to improve the heat dissipation performance of the heat dissipation unit 12. In addition, when a desired heat dissipation capability can be obtained by natural heat dissipation, the blower fan 20 can be omitted, and the cooling device 1 can have a fanless configuration with excellent silence.

[0023] The power supply circuit 30 supplies predetermined drive power to each of the pump 14 and the blower fan 20. The value of the drive power supplied is fixed, and the pump 14 and the blower fan 20 perform a certain operation according to the amount of power supplied. The power supply by the power supply circuit 30 is linked with the power supply circuit 65 for supplying power to the circuit component 61, and the pump 14 and the blower fan 20 are always operated while the power is supplied to the circuit component 61. In other words, while the circuit component 61 is operating, the pump 14 causes the coolant 40 to flow at a constant speed, and the blower fan 20 is constant toward the fins 121 regardless of the amount of heat generated (corresponding to the power consumption). Create a flow of air at a flow rate.

In the cooling device 1 configured as described above, the coolant 40 continues to circulate and return to the heat receiving unit 11 through the heat receiving unit 11, the heat radiating unit 12, the reserve tank 13, and the pump amount 14 in the order of description. Carries the heat of part 61 to heat dissipation part 12. [0025] In order to increase the efficiency of heat transport, the cooling liquid 40 is mixed with latent heat microcapsules as a latent heat material. That is, the cooling liquid 40 is a mixed liquid in which latent heat microcapsules are dispersed in water or antifreeze. A latent heat microcapsule is a fine particle having a particle size of 2 or less, in which a latent heat storage material is coated with a heat-resistant synthetic resin. Commercially available products include latent heat microcapsules in which norafine is coated with melamine resin. By using a capsule-like latent heat material, the latent heat storage material is less likely to be deteriorated and restrictions on the material of the dispersion medium are smaller than simply mixing the latent heat storage material.

FIG. 2 schematically shows a phase change of the latent heat material in the heat receiving part and the heat radiating part.

[0027] The coolant 40 circulating in the circulation channel 10 includes two types of latent heat microcapsules 41A and 41B in different states. One latent heat microcapsule 41A is composed of a solid phase latent heat storage material 43A and a resin film 42 covering it. The other latent heat microcapsule 41B includes a liquid phase latent heat storage material 43B and a resin film 42 covering the latent heat storage material 43B.

[0028] The latent heat microcapsule 41A flows into the heat receiving part 11 from the pipe 18. This latent heat microphone mouth capsule 41A absorbs the heat of the dispersion medium and changes to latent heat microcapsule 41B. That is, the solid phase latent heat storage material 43A melts to become a liquid phase latent heat storage material 43B. In the process, latent heat is stored by the latent heat storage material.

[0029] The stored latent heat microcapsule 41B flows from the heat receiving portion 11 to the heat radiating portion 12. In the heat radiating section 12, the latent heat microcapsule 41B returns to the latent heat microcapsule 41A. That is, the heat stored in the latent heat storage material 43B is released to the atmosphere through the dispersion medium, and the solid phase latent heat storage material 43B changes into a solid phase latent heat storage material 43A. The latent heat microcapsule 41A that has released the heat is sent to the heat receiving unit 11 again.

FIG. 2 shows a case where the entire latent heat storage material in one latent heat microcapsule undergoes a phase change. However, in reality, some of the latent heat storage materials may change phase, and the proportion of the phase change portion varies among many latent heat microcapsules.

In such liquid cooling type forced cooling using latent heat, the latent heat storage material in all the latent heat microcapsules is in a solid phase at the time of flowing into the heat receiving unit 11, and from the heat receiving unit 11. Latent heat storage material in all latent heat microcapsules at the time of outflow The cooling efficiency is maximized when is in the liquid phase. In other words, maximum heat storage is performed under the condition that the circulation flow rate is constant, and heat dissipation corresponding to the heat storage is performed. At this time, the temperature of the cooling liquid 40 is almost equal to the melting point of the latent heat storage material.

The cooling device 1 is configured so that the cooling efficiency is maximized in the harshest situation in use. Specifically, a latent heat storage material having an optimum melting point is mixed in the coolant 40. The procedure for selecting the latent heat storage material is as follows. Assuming that a coolant that does not contain latent heat storage materials is used, the circulation channel 10 is configured to determine how many times the temperature of the coolant flowing through the circulation channel 10 at a predetermined speed is the most severe. It is obtained by calculation based on the thermal property data of the part to be used or by experiment. Use a latent heat storage material with a melting point equal to or close to the temperature found in this way. For example, when selecting the line-up power of latent heat storage materials that can select the melting point in increments of 5 ° C up to 60 ° C, if there is one with a melting point that matches the determined temperature Select it, if not, select the one with the melting point closest. In practice, if the temperature is controlled from room temperature to about 100 ° C, a difference of about ± 10 ° C is acceptable for the obtained temperature.

[0033] Here, the most severe situation is a situation in which the environmental temperature is the upper limit of the environmental temperature range determined by the specifications of the equipment including the circuit component 61, and the amount of heat generated by the circuit component 61 is the maximum. is there. For example, if the device is a computer, the ambient temperature range is -10 ° C to 40 ° C, and the circuit component 61 is a CPU, the ambient temperature is 40 ° C and the CPU operating rate is 100%. The situation is the most severe.

FIG. 3 shows the relationship between a plurality of temperatures related to cooling and the melting point of the latent heat storage material.

[0035] In the most severe situation described above, the heat (heat quantity Qmax) generated by the circuit component 61 is transferred to the atmosphere (temperature TAmax) through the coolant 40 and the heat radiating section 12. Therefore, there is a thermal resistance Rl between the circuit component 61 and the coolant 40, a thermal resistance R2 between the coolant 40 and the radiator 12, and a thermal resistance R3 between the radiator 12 and the atmosphere. Therefore, the surface temperature T Jmax of the circuit component 61, the temperature TF of the coolant 40, the temperature TF of the heat dissipating part 12, and the temperature TAmax of the atmosphere

, Figure's Tori Ding]! 11 &> Ding? > 1¾> Dinghachi 111 & relationship arises.

[0036] As described above, in the cooling device 1, the melting point Tm of the latent heat storage material is selected so as to maximize the cooling efficiency in the harshest situation, and the melting point Tm is the temperature TF (strictly speaking, the temperature of the coolant 40). Equal to the estimated value).

[0037] In the above embodiment, the configuration of the cooling device 1 can be changed as appropriate within the spirit of the present invention. There are no limitations on the material, shape, heat capacity, and thermal characteristics of the components of the circulation channel 10. The heat source may be single or plural. The type and capacity of pump 14 can also be selected according to the application. When a variable capacity pump is used, the power supplied to the pump can be increased or decreased so that the coolant circulates at an appropriate flow rate according to the heat generation amount of the heating element and the thermal characteristics of the circulation flow path. The ventilation output of the blower fan 20 may be variable.

Industrial applicability

[0038] The present invention can be used for forced cooling of a heating element, and is particularly suitable for local cooling in a device used in a normal temperature region such as an information processing device such as a personal computer or a server computer. is there.

Claims

The scope of the claims

[1] A liquid cooling method for cooling a heating element using a cooling liquid containing a latent heat storage material,

With respect to the heating element, a circulation channel having a heat receiving part for receiving heat from the heating element and a heat radiating part for radiating the received heat is arranged,

While the heat generating element is generating heat, the latent heat storage material is circulated in the circulation channel to transfer the heat of the heat receiving part to the heat radiating part.

A cooling method characterized by that.

[2] The melting point of the latent heat storage material is the upper limit of the allowable operating environment temperature of the heating element, and the temperature of the coolant and the melting point of the latent heat storage material when the heating value of the heating element is maximum. Is less than ± 10 ° C

The cooling method according to claim 1.

[3] The circulation rate of the coolant containing the latent heat storage material is constant.

The cooling method according to claim 1 or 2.

[4] A liquid cooling type cooling device that cools the heating element using a cooling liquid containing a latent heat storage material,

A circulation flow path including a heat receiving portion and a heat radiating portion;

A cooling liquid containing a latent heat storage material that stores heat in the heat receiving section and transfers the heat to the heat radiating section in the circulation flow path.

A cooling device characterized by that.

[5] The cooling liquid is a liquid containing a capsule-like latent heat material in which a latent heat storage material is coated with a resin.

The cooling device according to claim 4.