JP2013160420A - Self-excited vibration heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-excited vibration heat pipe that has high starting characteristics without performing alteration of a flow passage structure, addition of a component and the like.SOLUTION: There is provided a self-excited vibration heat pipe 1 that includes: a heat pump body part 12 having a working fluid channel 10 arranged between a heating part 14 and a cooling part 16; and a refrigerant charged in the working fluid channel 10; wherein the refrigerant includes two or more kinds of immiscible refrigerants.

Description

  The present invention relates to a self-excited vibration heat pipe.

  For example, a technique is known in which heat of a heat generating component such as a microprocessor, an inverter, a motor, an internal combustion engine and a secondary battery is cooled by radiating heat from a heat receiving member such as a heat sink or a heat sink through a self-excited vibration heat pipe. ing.

  A self-excited vibration heat pipe is one in which a refrigerant is sealed in a working fluid channel disposed between a heating unit in contact with a heat generating unit and a cooling unit in contact with a heat receiving member, and one end of the channel is heated by the heating unit. When the other end of the flow path is cooled by the cooling unit, self-excited refrigerant vibration occurs due to the interaction between pressure fluctuation and void ratio change, etc., and heat is transferred from the heating unit to the cooling unit. .

  For example, in Patent Documents 1 to 4 and Non-Patent Document 1, self-excitation is performed by changing the flow path structure, adding components of a self-excited vibration heat pipe, etc. to perform vibration / circulation flow formation and vibration control of the refrigerant. The performance of the vibration heat pipe is improved.

JP 2008-298342 A JP 2007-333246 A JP 2003-302180 A JP 2002-364991 A

Toshihiro Fukuda et al., Proceedings of the 45th Japan Heat Transfer Symposium, 2008

  By the way, at the time of starting the self-excited vibration heat pipe, since the boiling of the refrigerant on the heating unit side, the pressure fluctuation in the flow path due to evaporation, the void ratio change, etc. hardly occur, there is a problem that the starting characteristics at low temperature are poor. . The self-excited vibration heat pipe of Patent Document 4 employs a method of forcibly oscillating the refrigerant. However, there is a concern that external power or the like may be required or the system may be complicated. The

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a self-excited vibration heat pipe having high starting characteristics without changing the flow path structure or adding components.

  The present invention is a self-excited vibration heat pipe comprising a heat pump main body having a working fluid channel disposed between a heating unit and a cooling unit, and a refrigerant sealed in the working fluid channel, wherein the refrigerant Includes two or more incompatible refrigerants.

  In the self-excited vibration heat pipe, the two or more incompatible refrigerants include at least a first refrigerant and a second refrigerant with a smaller amount of sealing than the first refrigerant, and the second refrigerant includes the second refrigerant It is preferable that the boiling point is lower than one refrigerant.

  In the self-excited vibration heat pipe, it is preferable that the second refrigerant has a larger saturation vapor pressure difference than the first refrigerant.

  The second refrigerant is preferably a fluorinated refrigerant.

  The first refrigerant is preferably at least one of water, ethanol, and acetone.

  According to the present invention, it is possible to provide a self-excited oscillating heat pipe having high starting characteristics without changing the flow channel structure or adding components.

It is a schematic cross section which shows an example of a structure of the self-excited vibration heat pipe which concerns on this embodiment. It is a cross-sectional schematic diagram of the working fluid flow path for demonstrating the state of the 1st refrigerant | coolant enclosed in the flow path, and a 2nd refrigerant | coolant. It is a cross-sectional schematic diagram of the working fluid flow path for demonstrating the state of 1 type of refrigerant | coolant enclosed in the flow path. It is a figure which shows the relationship between the temperature and surface tension of a 1st and 2nd refrigerant | coolant. It is a figure which shows the relationship between the temperature of a 1st and 2nd refrigerant | coolant, and a saturated vapor pressure curve. It is a figure which shows the boiling curve of the refrigerant | coolant enclosed in a flow path.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a self-excited vibration heat pipe according to the present embodiment. As shown in FIG. 1, the self-excited vibration heat pipe 1 includes a heat pipe main body 12 in which a working fluid channel 10 is formed, and a refrigerant sealed in the working fluid channel 10. The heat pipe main body 12 is a plate-like member made of a metal such as aluminum, copper, or stainless steel, a heat resistant resin, or the like. The heat pipe body 12 includes a heating unit 14 that is in contact with an external heat source having a high temperature and a cooling unit 16 that is in contact with a heat receiving member having a low temperature. In the heat pipe body 12, a working fluid flow path 10 disposed between the heating part 14 and the cooling part 16 is formed. The flow path pattern of the working fluid flow path 10 may be any pattern as long as it is disposed between the heating unit 14 and the cooling unit 16. For example, the working fluid flow path 10 shown in FIG. 1 connects the linear portions A linearly extending between the heating portion 14 and the cooling portion 16 and the straight portions A on the heating portion 14 side and the cooling portion 16 side. The turn section B and the folded section C formed on the cooling section 16 side are closed loop flow paths that meander between the heating section 14 and the cooling section 16. The heat pipe main body 12 shown in FIG. 1 is produced by, for example, joining two plate-like members on which flow path patterns are formed. For example, the heat pipe main body 12 is a heating unit. It may be a pipe-like member arranged in a meandering manner by reciprocating a plurality of times between 14 and the cooling unit 16. In this case, the inside of the pipe-shaped member becomes the working fluid flow path 10.

  The heat pipe main body 12 is provided with a refrigerant sealing port 18 for enclosing a refrigerant in the working fluid flow path 10 from the outside. The refrigerant is sealed by, for example, injecting the refrigerant into the working fluid channel 10 from the refrigerant sealing port 18 after the inside of the working fluid channel 10 is vacuum degassed, and sealing the refrigerant sealing port 18. In the present embodiment, two or more incompatible refrigerants are enclosed in the working fluid channel 10.

  Below, operation | movement of the self-excited vibration heat pipe 1 of this embodiment is demonstrated. In this embodiment, an example of a self-excited vibration heat pipe in which two types of refrigerants, a first refrigerant and a second refrigerant, are enclosed in a flow path will be described, but the present invention is not limited to this, and an incompatible relationship In this case, a plurality of refrigerants such as a third refrigerant may be enclosed in the flow path. Although the type and physical properties of the refrigerant will be described in detail later, the first refrigerant is, for example, water (boiling point 100 ° C.), and the second refrigerant is, for example, a fluorine-based refrigerant that is incompatible with the first refrigerant ( For example, a boiling point of 60 ° C.) is used.

  FIG. 2 is a schematic cross-sectional view of the working fluid flow path for explaining the states of the first refrigerant and the second refrigerant sealed in the flow path. FIG. 3 is a schematic cross-sectional view of a working fluid channel for explaining the state of one type of refrigerant sealed in the channel.

  As shown in FIG. 3, when one kind of refrigerant is sealed in the working fluid flow path 10, the working fluid flow path 10 has a liquid plug 20 made of refrigerant and a vapor plug made of refrigerant vapor. 22 are distributed. That is, the surface tension at both ends of the liquid plug 20 has the same value (σ1) unless a temperature difference occurs.

  On the other hand, as shown in FIG. 2, when the first and second refrigerants are sealed in the working fluid channel 10, the first liquid plug 24 mainly composed of the first refrigerant and The connection liquid plug 28 having the second liquid plug 26 mainly composed of the second refrigerant and the vapor plug 30 composed of the vapors of the first and second refrigerants are distributed. That is, the surface tension at one end of the connecting liquid plug 28 is the surface tension σ1 of the first liquid plug 24, and the surface tension at the other end of the connecting liquid plug 28 is the surface tension σ2 of the second liquid plug 26. It will be.

In the present embodiment, in order to efficiently form the liquid plugs (24, 26, 28) and the vapor plug 30 as described above in the working fluid channel 10, the inner diameter in the working fluid channel 10 is set to the refrigerant (first It is set to a Laplace diameter or less with respect to the refrigerant (second refrigerant). The Laplace diameter is determined by the following formula (1).
D = 1.84 [σ / (g · (ρL−ρv))] ^0.5 (1)
D: Laplace diameter σ: Refrigerant surface tension g: Gravity acceleration ρL: Liquid density ρv: Vapor density

  Normally, in the self-excited vibration heat pipe 1, when the heating unit 14 is heated by an external heating source and the cooling unit 16 is cooled by the heat receiving member, the pressure rise due to refrigerant evaporation in the heating unit 14 and the vapor in the cooling unit 16. The refrigerant moves between the heating unit 14 and the cooling unit 16 oscillating between the heating unit 14 and the cooling unit 16 due to the interaction between the pressure change in the flow path due to the pressure drop due to condensation and the change in the void ratio (volume ratio of gas and liquid). Is called. Therefore, in the self-excited vibration heat pipe in which one kind of refrigerant is sealed in the working fluid flow path 10, in the initial heating stage of the heating unit 14, specifically, in the low temperature range around the boiling point of the refrigerant, The interaction between the pressure change and the void ratio change hardly occurs, and there is room for improvement in the starting characteristics of the self-excited vibration heat pipe.

  On the other hand, in the case where the first and second refrigerants are enclosed in the working fluid flow path 10, when the heating unit 14 is heated by the external heating source and the cooling unit 16 is cooled by the heat receiving member, the vicinity of the heating unit 14 The surface tensions σ1 and σ2 acting on both ends of the connecting liquid plug 28 that is stationary in the working fluid flow path 10 change. FIG. 4 is a diagram illustrating the relationship between the temperature and the surface tension of the first and second refrigerants. For example, when the first refrigerant is water and the second refrigerant is a fluorine-based refrigerant, the difference between the surface tensions σ1 and σ2 further increases as the temperature of each refrigerant increases, and the balance of forces acting on both ends of the connecting liquid plug 28 is increased. The refrigerant starts to oscillate, and moves between the heating unit 14 and the cooling unit 16. When one kind of refrigerant is sealed in the working fluid flow path 10, the surface tension at both ends of the liquid plug 20 is the same (σ1), so the heating unit 14 is heated, and the refrigerant in the vicinity of the heating unit 14 is heated. Even if there is a temperature change, there is usually almost no temperature difference between both ends of the liquid plug 20 (because there is almost no difference in surface tension between both ends), so that the vibration of the refrigerant hardly occurs. Therefore, since the self-excited vibration heat pipe 1 using two kinds of incompatible refrigerants is more susceptible to vibration of the refrigerant than the self-excited vibration heat pipe using one kind of refrigerant, even when the amount of heating is small, It becomes possible to improve the starting characteristics of the heat pipe in a low temperature region or the like.

  In the self-excited vibration heat pipe 1 in which the first refrigerant and the second refrigerant are sealed in the working fluid flow path 10, when the heating amount in the heating unit 14 further increases, the saturated vapor of the refrigerant in the heating unit 14 and the cooling unit 16. The pressure difference becomes large, and a pump effect due to a pressure change in the flow path acts between the heating unit 14 and the cooling unit 16 to promote the vibration of the refrigerant. FIG. 5 is a diagram showing the relationship between the temperatures of the first and second refrigerants and the saturated vapor pressure curve, and the slope of the saturated vapor pressure curve is the saturated vapor pressure difference. In particular, as shown in FIG. 5, when the saturation vapor pressure difference of the second refrigerant is larger than that of the first refrigerant, the pump is caused by the pressure change in the flow path as compared with the self-excited vibration heat pipe in which only the first refrigerant is sealed. Since the effect acts greatly, it is possible to greatly improve the starting characteristics of the self-excited vibration heat pipe 1 in a low temperature region or the like. And when the temperature reaches the temperature at which the second refrigerant in the flow path starts to boil, the pressure change and the void ratio change in the flow path become large, and vibrations spread throughout the flow path. Furthermore, since the second refrigerant having a boiling point lower than that of the first refrigerant or having a large saturation vapor pressure difference boils before the first refrigerant, the pressure in the flow path near the heating unit 14 increases. The surface superheat degree at which the refrigerant begins to boil is reduced. As a result, the start of boiling of the connecting liquid plug 28 or the first liquid plug 24 in the working fluid flow path 10 is promoted, and vibration of the gas-liquid plug group in the flow path is started at a lower temperature and a lower heat flow rate condition.

  In the case of a self-excited vibration heat pipe in which only the second refrigerant having a boiling point lower than that of the first refrigerant is enclosed in the working fluid flow path 10, vibration of the refrigerant due to the difference in surface tension at both ends of the liquid plug 20 can hardly be expected. Until the temperature reaches the temperature at which the refrigerant begins to boil, vibration in the flow path hardly occurs, and the starting characteristics of the self-excited vibration heat pipe using one type of refrigerant use two or more types of incompatible refrigerants. The result is inferior to the starting characteristic of the self-excited vibration heat pipe 1.

  Hereinafter, the types and physical properties of the first and second refrigerants will be described.

  Examples of the first refrigerant include natural refrigerants such as water and ammonia, alcohol solvents such as methanol and ethanol, ketone refrigerants such as acetone, and ethylene glycol. In particular, the first refrigerant is preferably selected as a main refrigerant responsible for heat transport of the self-excited vibration heat pipe 1 according to the temperature range of the installation site of the self-excited vibration heat pipe 1, and the temperature of the installation site is room temperature. In the vicinity of the temperature range, water, ethanol, acetone and the like are preferable, and it is more preferable to select water having good thermal properties in the self-excited vibration heat pipe 1. In addition, as long as the 1st refrigerant | coolant is compatible refrigerant | coolants, the refrigerant | coolant etc. which mixed water and ethanol are also contained, for example. The second refrigerant is not particularly limited as long as it is an incompatible solvent with respect to the first refrigerant, and examples thereof include a fluorine-based refrigerant and a hydrocarbon-based refrigerant. For example, when water or the like is used as the first refrigerant, it is preferable to use a fluorine-based refrigerant from the viewpoint of incompatibility with water, the boiling point with water or the saturated vapor pressure, and the like. Examples of the second refrigerant include fluorocarbon refrigerants such as fluorinate, Freon refrigerants such as HCFC123 and HFC134a, hydrocarbon refrigerants such as butane, and the like. Similarly to the first refrigerant, the second refrigerant includes mixed refrigerants as long as they are compatible refrigerants. The above-mentioned substances of the first refrigerant and the second refrigerant are exemplifications and are not limited to these. If the first refrigerant and the second refrigerant are incompatible with each other, they can be applied to a self-excited vibration heat pipe. All refrigerants can be used.

  Incompatible in this specification is not limited to the case where there is no complete compatibility. In the connection liquid plug 28 formed in the flow path, the first liquid plug 24 and the second liquid plug 26 Between the first liquid plug 24 and the second liquid plug 26 contains a small amount of the second refrigerant, or the second liquid plug 26 contains a small amount of the first refrigerant. Or you may. Moreover, it is preferable to consider the solubility with respect to a solvent for the incompatibility of a 1st refrigerant | coolant and a 2nd refrigerant | coolant.

  The ratio of the enclosed amount of the first refrigerant and the second refrigerant is such that, when a refrigerant with good thermal characteristics is used as the first refrigerant, the amount of heat transported by the self-excited oscillating heat pipe 1 can be mainly assigned to the first refrigerant. Since it is desirable, it is preferable to enclose the second refrigerant in a smaller proportion (amount) than the first refrigerant. And when the enclosure ratio of a 2nd refrigerant | coolant is smaller than a 1st refrigerant | coolant, it is preferable to select a refrigerant | coolant whose 2nd refrigerant | coolant is lower than the boiling point of a 1st refrigerant | coolant. The second refrigerant is preferably a refrigerant having a larger saturation vapor pressure difference than the first refrigerant. Thus, if the second refrigerant with a small amount of sealing has a low boiling point or a large saturated vapor pressure difference, the saturated vapor pressure difference between the refrigerant in the heating unit 14 and the cooling unit 16 becomes large, and the heating unit 14 and the cooling Since the pump effect due to the pressure change in the flow path acts greatly between the portions 16, it is possible to improve the heat transport rate. As a result, the starting characteristics of the self-excited vibration heat pipe can be improved. As a combination satisfying the relationship between the boiling point and the saturated vapor pressure as described above, it is preferable to use water as the first refrigerant and use a fluorine-based refrigerant as the second refrigerant.

  FIG. 6 is a diagram showing a boiling curve of the refrigerant sealed in the flow path. As shown in FIG. 6, normally, the higher the pressure is, the lower the surface superheat degree at which the refrigerant starts boiling. Accordingly, the second refrigerant having a lower boiling point or a larger saturated vapor pressure difference than the first refrigerant boils first, so that the pressure in the flow path in the vicinity of the heating unit 14 increases, and therefore the connecting liquid plug 28 or the first liquid The degree of surface superheat at which boiling of the plug 24 starts is lowered, and the start of boiling of the connecting liquid plug 28 or the first liquid plug 24 in the working fluid flow path 10 is promoted. As a result, the self-excited vibration of the gas-liquid plug group in the flow path is started under a low temperature / low heat flow rate condition.

  The self-excited vibration heat pipe of this embodiment can be used for a heat radiating device for heat-generating parts such as a microprocessor, an inverter, a motor, an internal combustion engine, and a secondary battery, various temperature control devices, and the like.

  DESCRIPTION OF SYMBOLS 1 Self-excited vibration heat pipe, 10 Working fluid flow path, 12 Heat pipe main-body part, 14 Heating part, 16 Cooling part, 18 Refrigerant enclosure port, 20 liquid plug, 22 Steam plug, 24 1st liquid plug, 26 2nd liquid Plug, 28 connecting fluid plug, 30 steam plug.

Claims (5)

A self-excited oscillating heat pipe comprising a heat pipe body having a working fluid channel disposed between a heating unit and a cooling unit, and a refrigerant sealed in the working fluid channel,
The self-excited vibration heat pipe, wherein the refrigerant includes two or more kinds of incompatible refrigerants.   The two or more incompatible refrigerants include at least a first refrigerant and a second refrigerant with a smaller amount of sealing than the first refrigerant, and the second refrigerant has a lower boiling point than the first refrigerant. The self-excited vibration heat pipe according to claim 1.   The self-excited vibration heat pipe according to claim 2, wherein the second refrigerant has a larger saturated vapor pressure difference than the first refrigerant.   The self-excited vibration heat pipe according to any one of claims 1 to 3, wherein the second refrigerant is a fluorine-based refrigerant.   The self-excited vibration heat pipe according to any one of claims 1 to 4, wherein the first refrigerant is at least one of water, ethanol, and acetone.

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