JPS62284191A - Heat pipe - Google Patents

Abstract

PURPOSE:To enable the feed of a proper amount of condensed liquid, responding to a vaporizing amount, to a vaporizing part, by providing a detecting means which detects a factor fluctuated according to a fluctuation in amount of liquid present in the capillary structure part of the vaporizing part. CONSTITUTION:According to an instruction from a control means 27, a heater 25 is actuated, a capillary 21 is wholly heated, and the temperature of an interface between steam and liquid is decreased occasioned by vaporization of liquid in the capillary 21. The decreased in temperature is monitored by means of a sensor 23 formed with plural thermocouples, and is inputted as a position signal for the capillary 21 to the control means 27. By means of the signal, the control means 27 computes a difference PV-PL between a steam pressure PV and a liquid pressure PL. In this case, it is decided that a pressure difference between the liquid pressure PL and the steam pressure PV exceeds a maximum capillary force when rotation of a pump 17 is low despite of that vaporization in a line 5 for steam is brisk and the liquid pressure PL is a specified value or more lower than the steam pressure PV as compared with each other, and a signal for increase in the number of revolutions of a pump is outputted from the control means 27 to the pump 17.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Object of the Invention] (Field of Industrial Application) The purpose of the present invention is to provide a heat pipe suitable for transporting a large heat source.

(Prior art) Conventionally, the capillary structure of a heat pipe is composed of groups, wire mesh, etc., and generates capillary force to transport the condensed liquid to the evaporation part, and uses this capillary force to transport the liquid to the condensation part. It has two functions: as a passageway for movement. By the way, the size of the gap in the capillary structure has contradictory characteristics: it is better to have a smaller gap size for generating capillary force, but it is better to have a larger gap size for the liquid passage. The gap size is set to balance the conflicting characteristics mentioned above.For this reason, conventional heat pipes cannot increase the maximum flow rate of condensate very much, and their heat transport ability is limited. .

In response to this, capillary pumps, monogroup heat pipes, and the like have been developed in which the capillary structure has only a surface for generating capillary force, and a separate passage for condensate movement is provided.

This capillary pump and monogroup heat pipe are
It is characterized by the fact that an external pump movement horn is not required to drive the working liquid, and that it has a self-control property in that only evaporated liquid is supplied. However, since the fluid driving force relies on capillary force, the increase in liquid transport capacity is not so large, and it is insufficient for transporting a large amount of heat over long distances.

Therefore, it is conceivable to use a mechanical pump to drive the production fluid. In this case, if the amount of liquid m that has evaporated and decreased in the evaporation section is not supplied to the evaporation section, a so-called dryout will occur, and if more than the amount of liquid m that has decreased by evaporation is supplied, there will be an excessive amount of liquid, and any This also prevents a decrease in heat transfer coefficient. Therefore, it is necessary to accurately supply the amount of liquid to the evaporator, and the biggest problem is how to control the amount of liquid supplied.

As a method of controlling the amount of liquid supplied to the evaporation section,
For example, there is a device that uses an ultrasonic sensor to detect the amount of liquid remaining in the liquid path of the evaporator, opens a liquid supply valve based on this detection signal, and supplies the liquid by driving a pump, etc.
esign and T esto [a Tw
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(See page 2 of IAA-85-0918)
.

However, such a structure has the following problems. In other words, when the flow rate in the liquid path of the evaporation section decreases to a predetermined Φ, the ultrasonic sensor detects this and issues a liquid supply command, which starts and stops the pump and opens and closes the pulp. etc. must be done frequently and intermittently.

For this reason, the control II mechanism and system become complicated, and reliability and durability decrease. Furthermore, if the amount of liquid in the liquid path of the evaporator decreases, a gap will occur between the liquid on the evaporation surface and the evaporation surface, which may cause dryout. In order to prevent this, a capillary structure that communicates the liquid path with the evaporation surface is required in addition to the capillary structure provided on the evaporation surface.

(Problems to be Solved by the Invention) As described above, conventional heat pipes cannot increase the maximum flow of condensate and have a limited heat transport ability. In addition, capillary pumps, monogroup heat pipes, etc. rely on capillary force for liquid driving force, and are therefore insufficient for transporting large amounts of heat over long distances. Furthermore, if the liquid level in the evaporator is detected by an ultrasonic sensor, the liquid supply valve is opened based on this detection signal, and the liquid is supplied by driving a pump, etc., what is the control mechanism and system? ! There are problems such as increased complexity and reduced reliability and durability.

Therefore, this invention was devised in view of the above-mentioned conventional problems, and is suitable for transporting a large amount of heat over long distances by driving a pump, while controlling the amount of evaporation in the evaporator section through continuous control. The purpose of the present invention is to provide a heat pipe that can supply an appropriate amount of condensate depending on the amount of condensate.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention includes an evaporation section having a capillary structure, a condensation section communicating with the evaporation section,
It consists of a liquid transport pipe for returning the condensate from the condensing part to the evaporation part, and a pump installed in this liquid transport pipe to give driving force to the condensate. a detection means for detecting a factor that changes according to an increase or decrease in the amount; and a control means for controlling the flow rate of the liquid transport pipe so that the amount of liquid present in the capillary structure is appropriate based on the output of the detection means. The configuration includes the following.

(effect) Condensate driving force is provided by a pump.

When the amount of liquid present in the capillary structure of the evaporation section decreases due to evaporation, the detection means detects a factor that changes due to this decrease. Based on this detection, the control means increases the flow rate of the liquid transport pipe. When the amount of liquid present in the capillary structure exceeds a certain amount due to this increase in volume, the flow rate is controlled to decrease based on the detection by the detection means as described above.

(Example of the invention) The present invention will be described in detail below.

FIG. 1 shows a schematic configuration diagram of a heat pipe according to a first embodiment. This heat pipe has an evaporation section 1 that absorbs heat from an electronic device and evaporates the working fluid, and a condensation section 3 that radiates heat to a space such as the atmosphere.

The evaporating section 1 and the condensing section 3 have a steam line 5.7 and a production line 9,11. The steam conduit 5 and the production conduit 9 of the evaporation section 1, or the steam conduit 7 and the production conduit 11 of the condensation section 3, are formed to have the same length in the axial direction, and have the same length in the circumferential direction. A part of the shaft is connected in communication throughout the axial direction.

Although not shown in the steam pipe line 5 of the evaporation section 1,
It has a capillary structure composed of a circumferential group and an axial group. The circumferential group is provided along the entire inner circumferential direction of the steam pipe line 5, and its end portion communicates with the production pipe line 9. Further, a plurality of circumferential groups are provided at predetermined intervals in the axial direction of the steam pipe line 5. The axial groups are provided across the axial direction of the steam pipe line 5, and are provided on the entire inner surface at predetermined intervals in the circumferential direction. The axial group and the circumferential group are in cross communication with each other.

The steam pipe line 5 of the evaporating section 1 and the steam pipe line 7 of the condensing section 3 are connected to each other through a steam transport pipe 13. Further, the formation pipe line 9 of the evaporation section 1 and the formation pipe line 11 of the condensation section 3 are connected to each other by a liquid transport pipe 15. This liquid transport pipe 15 is for returning the condensed liquid from the condensing section 3 to the evaporating section 1, and a pump 17 that provides a driving force to the condensed liquid is interposed in the middle.

On the other hand, the evaporation section 1 is provided with a detection means 19. This detection means 19 detects a factor that changes according to an increase or decrease in the amount of liquid present in the capillary structure of the evaporation section 1, and in this embodiment, the pressure of the steam in the steam pipe 5, It is configured to detect the difference between the pressure of the liquid in the legal pipe line 9 and the pressure of the liquid. That is, this detection means 19 is
It consists of a thin tube 21 erected almost vertically and a sensor 23 that detects the position of the liquid within this thin tube 21. The thin tube 21 has one end connected to the steam portion in the steam pipe 5 and the other end connected to the liquid portion in the legal pipe 9. The sensor 23 is composed of a plurality of thermocouples arranged in series along the thin tube 21. Roughly, the thin tube 21
A heater 25 for heating the thin tube 21 is provided along the tube.

These sensors 23 and heaters 25 are connected to the control means 2.
7, and the pump 17 is connected to this control means 27.

The control means 27 is composed of, for example, a microcomputer, and controls the rotational speed of the pump 17 to control the flow rate of the liquid transport pipe 15 based on the output of the detection means 19 so that the amount of liquid present in the capillary structure is appropriate. ffi i
! The iIl m is configured.

Next, the operation of the first embodiment will be explained.

First, let's talk about the general operation of this heat pipe.
In the capillary structure of the evaporator 1, an appropriate amount of liquid is retained from within the legal conduit 9 by capillary force. That is, the working fluid in the legal pipe line 9 is lifted up by the plurality of circumferential groups in the steam pipe line 5, and by the plurality of axial groups communicating with the circumferential group,
The lifted liquid spreads in the axial direction.

Then, the working fluid in the steam pipe 5 evaporates due to heat absorption when cooling the electronic equipment, etc., and the steam is introduced into the steam pipe 7 of the condensing section 3 via the steam transport pipe 13. . Condensation occurs in the steam pipe 7 due to heat radiation to the atmosphere, and the condensed liquid reaches the liquid phase pipe 11 . The condensate in the liquid phase pipe 11 is given driving force by the pump 17, and the evaporator 1
is returned to the forehead conduit 9.

In this case, if the steam pressure in the steam pipe 5 is PV, the liquid pressure in the forehead pipe 9 is PL1, and the maximum capillary force in the steam pipe 5 is ΔPcap −l1lax, then PV−PL<Δ
Pcap-wax ・(1) pv-PL>
O・<2) must be satisfied. That is, the above (1)
If the condition of the formula (2) is not satisfied, the liquid in the steam pipe 5 will be pushed out into the forehead pipe 9, resulting in a so-called dry-out condition, and if the condition of the above formula (2) is not satisfied,
The liquid pressure PL is higher than the vapor pressure Pv, and the liquid flows from the forehead pipe 9 into the steam pipe 5 to perform normal evaporation in the vapor pipe 5. Because it will disappear.

The conditions of the above equations (1) and (2) are maintained by the control of the control means 27.

Therefore, the control by the control means 27 will be explained using the flowchart shown in FIG.

Along with the action of the heat pipe as described above, step S
1, the position of the liquid in the thin tube 21, that is, the position of the interface between vapor and liquid is read. Reading of the position of this boundary surface is performed as follows.

That is, the heater 25 is activated by a command from the control means 27, and the thin tube 21 is heated entirely. The evaporation of the liquid within this thin tube 21 lowers the temperature at the interface between the vapor and the liquid. This temperature drop at the interface is monitored by a sensor 23 composed of multiple thermocouples.
The signal is input to the control means 27 as a position signal with respect to the thin tube 21 .

The control means 27 uses the signal from the sensor 23 to calculate the difference between the vapor pressure Pv and the liquid pressure PL, pv -1'L, in step $2. In this case, the interface between liquid and vapor within the thin tube 21 is determined by the capillary force Δp ca
It is determined on the condition that the difference between p and the head ΔPH due to the weight of the liquid in the thin tube 21 is balanced by the pressure difference between the liquid pressure Pv and the vapor pressure PL. That is, the relational expression ΔpCap-8PH=to pv-PL-(3) holds true.

Here, if the diameter of the capillary tube 2 is constant, the capillary force △p c
ap is constant, and the pressure difference between the vapor pressure Pv and the liquid pressure PL can be determined by the position of the liquid head ΔPH1, that is, the interface between the liquid and the vapor.

Next, in step S3, it is determined whether the condition of equation (1) above is satisfied. In this case, even though evaporation in the steam pipe line 5 is active, the rotation of the pump 17 is low, and if the liquid pressure PL is smaller than a certain level compared to the steam pressure Pv, the pressure difference between the two is the maximum capillary. Force Δp c
It is determined that the value is larger than ap max, and the process proceeds to step S4.
Move to. In step S4, a signal to increase the number of revolutions of the pump 17 is sent from the control means 27, and the number of revolutions of the pump 17 is increased by a predetermined constant number of revolutions.

Then, the process returns to step S3, and the above equation (1) is again judged. In this case, if the pressure difference pv -PL is larger than the maximum capillary force ΔPcap -max even though the pump rotation speed is increased in step S4, an increase signal is issued again in step S4, and steps 83 and 84 are repeated. .

In step S3, the pressure difference PV-PL is △Pcap ・+X
If it is determined that it is smaller than aX, the process moves to step S5. In step S5, the above equation (2) is determined. In this case, if the pump rotational speed is greater than a certain level with respect to the evaporation action and the liquid pressure PL is greater than a certain level compared to the vapor pressure pv, the difference between the two, Pv-PL, becomes negative, so the process moves to step S6. . In this step S6, a pump rotation speed reduction signal is issued to the pump 17, and the rotation speed of the pump 17 is decreased by a predetermined constant rotation speed. Then, return to step S5 again and perform the above (2).
The expression is evaluated. In this case, if the pressure difference Pv-PL is O or smaller even though the pump rotation speed has decreased, step S6 is repeated again. If it is determined in step S5 that the pressure difference pv-PL is positive, the heat pipe is operating normally, and the process returns to step S1.

By repeating each of the above steps, the steam pressure PV and liquid pressure PL are maintained appropriately, and an appropriate amount of working liquid is present in the capillary structure in the steam pipe 5, resulting in a high heat transfer force. The heat pipe is operated by

In this way, in this first embodiment, from the condensing section 3 to the evaporating section 1
Since the condensate is returned to the pump 17 by driving the pump 17, it is suitable for long-distance, high-temperature heat transport. Also, the pump 17 is not under intermittent i control, but its rotation speed is continuously 1 lil! Since the control structure and system are very simple, reliability and durability are improved. In addition, the control means 2
Since the control by 7 is performed according to the increase or decrease of the working fluid present in the capillary structure in the steam pipe 5,
The capillary structure will not dry out or become overfilled. Furthermore, since the sensor 23 detects the position of the liquid within the m-tube 21, it can easily detect the differential pressure Pv-PL, which is a factor that changes depending on the increase or decrease of the working liquid present in the capillary structure. can do. Furthermore, since the position of the liquid is detected by detecting the position at which the evaporation temperature decreases on the liquid surface, it can be detected accurately. In addition, in order to detect the differential pressure PV-PL in this first embodiment, a differential pressure gauge using a strain gauge or a bellows may be used. Although not shown, the flow control of the liquid transport pipe 15 can also be performed by throttling control of a valve or the like. Furthermore, the heating of the m-tube 21 can be performed directly on the entire tube,
In this case, the heat flow rate can be kept constant, allowing more accurate detection.

FIG. 3 shows a modification of the thin tube of the first embodiment, in which the thin tube 29 is a tapered tube. These two capillary tubes are used in a zero gravity field such as outer space, and when comparing the cases where the boundary surfaces are at positions 31 and 33, the capillary force at position 33 is larger than that at position 31. It is something. therefore,
In this case as well, the relational expression ΔPcap=
The differential pressure Pv-PL can be calculated from pv-PL by detecting the position of the boundary surface. Therefore, in this case, the same effect as in FIG. 1 can be achieved in a zero gravity field.

FIG. 4 shows a second embodiment of the present invention, in which a detection means 35 detects the heat transfer coefficient α of the evaporator 1. That is, this detection means 35 consists of thermocouples 37 and 39 provided in the evaporator 1, an orifice 41 provided in the steam transport pipe 13, and a differential pressure gauge 43. The thermocouple 37 measures the temperature T of the outer wall surface of the steam pipe line 5 of the evaporation section 1.
The thermocouple 39 is used to detect the steam temperature Tv in the steam pipe 5. The thermocouples 37 and 39 and the differential pressure gauge 43 are connected to a control means 45.

Next, the operation of this second embodiment will be described.

The basic operation of the heat pipe is the same as in the first embodiment. Control by the control means 45 will be explained using the flowchart of FIG. First step S5
1, the pressure difference before and after the orifice 41 is read from the output signal of the differential pressure gauge 43.

Next, the process moves to step S52, and the steam flow ff1G is calculated based on the pressure difference read in step 851. Next, the process moves to step S53, and the wall surface temperature T of the steam pipe line 5 is
Load V. This wall surface temperature UTw is based on the signal from the thermocouple 37. In step 854, the steam temperature TV in the evaporator 1 is read. This steam temperature TV is thermocouple 39
It is based on the input signal from . When the above reading is completed, the heat transfer coefficient α of the evaporator 1 is calculated in step S55. In this case, the heat transfer coefficient α is (TV −
TV) given in AV. Here, γ is the latent heat of vaporization, and Ay is the evaporation area.

In step S56, a comparison is made between the previously calculated heat transfer coefficient αn-1 and the current heat transfer coefficient αn. If it is determined by this comparison that αn is 1 - αn, this indicates that the heat transfer coefficient α is gradually increasing during operation of the heat pipe, and the process returns to step 851 to repeat the above steps.

If it is determined in step S56 that αn-+≧αn, this indicates that the heat transfer coefficient α is decreasing or stagnant. Therefore, in this case, it is necessary to control the rotational speed of the pump, and the process moves to step S57, where it is determined whether or not the heat transfer coefficient α is rapidly decreasing. If it is determined in step S57 that the decrease in the heat transfer coefficient α is sudden, the decrease in the heat transfer coefficient α is due to the fact that the working fluid in the steam pipe line 5 in the evaporator 1 has decreased below the appropriate level. It is determined that this is the case, and the process moves to step 858, where the control means 45 issues a signal to increase the number of rotations of the pump 17. Therefore, the pump 17 is controlled to increase by a predetermined number of rotations, and the amount of condensed liquid supplied to the evaporator 1 is increased. In step 357, if it is determined that the decrease in the heat transfer coefficient α is gradual, it is determined that the decrease in the heat transfer coefficient α is due to excessive working fluid being supplied into the steam pipe line 5. The determination is made, and the process moves to step S59, where a pump rotation speed reduction signal is issued. Therefore, the pump 17 rotates at a reduced speed by a predetermined number of rotations, and the amount of condensed liquid supplied to the evaporator 1 is reduced.

By repeating the above steps, an appropriate amount of working fluid is retained in the capillary structure within the steam pipe line 5, and the heat pipe can be operated while maintaining a high heat transfer coefficient. Further, in this second embodiment, since control is performed by determining the heat transfer coefficient, more direct control is possible. In addition, this embodiment provides the same effects as the first embodiment.

FIG. 6 shows a third embodiment of the invention. In this third embodiment, another small steam pipe 47 communicating with the steam pipe 5 of the evaporator 1 and a small wave pipe 49 communicating with the liquid pipe 9 are provided.

The small steam conduit 47 has a capillary structure having a capillary size larger than that of the capillary structure of the steam conduit 5. A thermal lightning pair 51.53 corresponding to the thermal lightning pair 37.39 attached to the steam pipe 5 is also attached and connected to the control means 55. And this third
This embodiment basically operates in the same manner as the second embodiment shown in FIG. 4, but the judgment at step 857 in the flow chart shown in FIG. This is done while monitoring the heat transfer coefficient of the steam pipe line 47. That is, if the heat transfer coefficient of the evaporation surface of the small steam pipe 47, which has a large capillary size, decreases first, it is determined that there is a liquid shortage, and if the heat transfer coefficients of both decrease at the same time, it is determined that there is an excess of liquid. Therefore, in addition to producing substantially the same effects as the second embodiment, it is possible to accurately determine whether the decrease in the heat transfer coefficient is due to a lack of liquid or an excess of liquid.

In this third embodiment, one small steam pipe 47 was provided in addition to the steam pipe 5 to monitor the change in heat transfer coefficient between the two. A similar effect can be obtained by providing two pipes, each with a capillary structure having a different capillary size, and by monitoring changes in the heat transfer coefficient between the two.

FIG. 7 shows a fourth embodiment of the invention. In this embodiment, in contrast to the second embodiment, a small steam pipe 57 and five small wave pipes are provided, and this small steam pipe 57 is provided with a thermal lightning pair 61, 63 and a heater 65. It is. Therefore, in this fourth embodiment, the calculation of the heat transfer coefficient α is performed by (Tw - Tv) A. However, Q is heater 65
, and A is the evaporation area of the part where the heater is installed. Therefore, this fourth embodiment also provides substantially the same effects as the second embodiment, and the steam transport pipe 13 can be simplified.

[Effects of the Invention] As is clear from the above, according to the configuration of the present invention, since the driving force for the condensate is provided by the pump, it can be used over long distances.
It is possible to transport a large amount of heat.

Furthermore, since factors that vary depending on the increase or decrease of the liquid ports present in the capillary structure of the evaporator are detected and controlled, it is possible to supply the evaporator with an appropriate amount of condensed liquid according to the amount of evaporation. Also, since this control is performed by continuous flow control of the condensate, compared to the case where it operates intermittently,
The control 11 mechanism and system become simpler to use, and reliability and durability are significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a heat pipe according to a first embodiment of the present invention and a second embodiment, FIG. 5 is a flowchart of the same, and FIG. 6 is a schematic diagram of a heat pipe according to a third embodiment. FIG. 7 is a schematic diagram of a heat pipe according to a fourth embodiment. 1... Evaporation section 3... Condensation section 17... Pump 19.35... Detection means 27.45.55... Control means 21.29... Thin tube 23... Sensor

Claims (7)

[Claims] (1) An evaporation section having a capillary structure, a condensation section communicating with the evaporation section, a liquid transport pipe for returning the condensate from the condensation section to the evaporation section, and a condensate connected to the liquid transport pipe. a pump that provides a driving force to the capillary structure of the evaporation section, a detection means that detects a factor that changes according to an increase or decrease in the amount of liquid present in the capillary structure of the evaporation section, and a A heat pipe comprising: a control means for controlling the flow rate of the liquid transport pipe so that the amount of liquid present is appropriate. (2) The heat pipe according to claim 1, wherein the detection means detects a pressure difference between steam and condensate. (3) The heat pipe according to any one of claims 1 to 2, wherein the detection means is provided in the evaporation section. (4) The detection means comprises a thin tube having one end connected to a steam portion and the other end connected to a liquid portion, and a sensor for detecting the position of the liquid within this thin tube.
The heat pipe according to items 3 to 3. (5) The heat pipe according to claim 4, wherein the thin tube is a tapered tube. (6) The heat pipe according to claim 1, wherein the detection means detects the heat transfer coefficient of the evaporation section. (7) The evaporation unit includes evaporation surfaces having different capillary dimensions, and the control means controls the flow rate of the pump based on the difference in heat transfer coefficient between these evaporation surfaces. The heat pipe according to item 6.