JPH0631704B2 - Heat pipe - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat pipe, and particularly to a long-distance heat transfer or a large heat transfer capability which is difficult in a conventional heat pipe due to a limit of a heat transfer distance. The present invention relates to a heat pipe suitable for use under the high heat load required.

[Conventional technology]

As a heat pipe that generates a large driving pressure for the conventional long-distance heat transport or the supply of the condensate required for a heat pipe having a small diameter, U.S. Pat.
Nos. 52 and 367737 have been proposed.

[Problems to be solved by the invention]

By the way, in the above-mentioned conventional heat pipe structure, there is a problem that the heat transfer performance is poor because the pressure loss at the inlet and outlet of the permeation membrane is large. Therefore, conventional heat pipes have been limited to applications such as cooling the onboard electronics of aircraft (especially fighters) that require large drive pressures to supply the condensate.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a heat pipe capable of long-distance heat transport and having heat transfer performance.

[Means for solving problems]

In the heat pipe of the present invention, the condensate passage and the vapor passage are independently configured, and the inlet end of the condensate passage is partitioned by a permeable membrane and the outlet end of the condensate passage is partitioned by a wick, and a solvent is placed around the permeable membrane. In addition, a mixed solution of a solute and a solvent is contained in the osmotic membrane, and the above-described object is achieved.

[Action]

According to the present invention, the solvent is arranged around the osmotic membrane, and since the mixed solution of the solute and the solvent is contained in the osmotic membrane,
The pressure loss can be greatly reduced, and a large driving pressure of the condensate is generated due to the osmotic pressure.

〔Example〕

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a heat pipe according to the present invention. The present embodiment is a loop heat pipe having a structure in which a condensate passage 1 and a vapor passage 2 which are independent of each other are connected. The passage tube wall is made of copper or aluminum having high thermal conductivity.

A permeation membrane partition 3 is provided at the inlet of the condensate passage 1, a solvent 5 is arranged around the permeation membrane partition 3, and a mixed solution 4 of a solute and a solvent is provided in the permeation membrane partition 3. It is enclosed. In the present embodiment, it is premised on use on the ground, and the power direction is the downward direction of the paper as shown in FIG.
The combination of solute and solvent is water and NaCl.
(Salt), water and C ₁₂ H ₂₂ O ₁₁ (sucrose), water and an alkali metal borate (for example, NaBO ₂ ) and the like are suitable.
As the permeable membrane, an acetyl cellulose membrane, a cellulose-based or nylon-based hollow membrane is suitable. All of the above permeable membranes must be used at 90 ° C or lower. If it is used at higher temperature, it will generate zeolite (WmZnO _2n・ sH ₂
It is advisable to use a semipermeable membrane obtained by heating and removing water of crystallization such as O; W is Na, Cl, K, and Z is Si + Al, and a liquid other than water (for example, Freon) may be used as a solvent.

Furthermore, when an ultrafine powder of a metal having a particle number of about 30 to 4000 atoms (particle diameter of 10 to 50Å) is used, almost all combinations of solutes and solvents can be used at high temperatures.

The condensate passage 1 and the vapor passage 2 are respectively provided with a steam heating unit 8
And a condensing / cooling unit 7 are provided and configured to perform heat transport.

Next, the operation of the heat pipe according to this embodiment will be described. An osmotic pressure due to the concentration difference between the solvent 5 and the mixed solution 4 of the solute and the solvent is generated through the osmotic membrane partition wall 3, and the solvent 5 flows into the condensate passage 1 side through the osmotic membrane partition wall 3. Inflowing solvent 5
The amount of the mixed liquid 4 corresponding to the amount is evaporated by the evaporation heating unit 8. Here, the wick 6 has a function of uniformly distributing the mixed liquid on the heating wall surface in order to promote evaporation in the evaporation heating unit. In addition, since the droplets of the mixed liquid 4 generated during evaporation fall by gravity and return to the mixed liquid 4 side,
Only the vapor of the solvent 5 passes through the vapor passage 2. The vapor is condensed in the condensing cooling unit 7 and then returns to the solvent 5 to radiate the latent heat of condensation to the cooling unit 7 for heat transfer. The driving pressure due to osmotic pressure is, for example, about 5 kg / cm ^{2 in} the case of 5% saline solution, so the conventional wick type heat pipe (driving pressure is about 0.
It is possible to operate in the top heat mode (upper heating, lower heating) with a head drop of 50 m, which is impossible with 002 kg / cm ² ).

Further, the conventional osmotic pressure heat pipe is a single tube type, and the condensate passage and the vapor passage are separated by the osmosis membrane,
Although it was difficult to reduce the diameter of the heat pipe, in the present embodiment, since the condensate passage 1 and the vapor passage 2 are independent of each other, it is easy to reduce the diameter. Moreover, since the condensation cooling is performed directly from the pipe wall, the heat exchange performance is excellent. Further, the gas-liquid separation membrane is not required at the outlet of the condensate passage 1, and the permeation membrane is formed in a pleated shape as shown in FIG. 1, so that the permeation membrane area can be increased. ,
The pressure loss can be significantly reduced. Further, since the osmotic membrane partition on the outlet side of the condensate passage 1 can be eliminated, the pressure loss can be further reduced. For this reason, a large driving pressure of the condensate is generated due to the osmotic pressure, and not only the heat exchange performance is excellent, but also the pressure loss is small. Further, since the heat exchange performance is large, even when the flow rate of the condensate increases and the pressure loss increases, it is possible to use it under a high heat load that requires sufficient supply of the condensate.

FIG. 2 shows an embodiment of the present invention in which a plurality of hollow permeation membranes 3 ′ having an outer diameter of about 1 mm are inserted in the cylindrical case 9. With such a structure, when the permeation membrane 3'having a diameter of 3 cm and a length of 20 cm is bundled into a cylindrical shape, the total surface area becomes about 1000 cm ² . Therefore, the flow velocity in each hollow permeation membrane 3'is extremely low, and the pressure loss is small. Hollow permeation membrane 3'bundled in a cylindrical shape
Both ends of are bonded with a synthetic resin material. On the inflow side 10 of the solvent condensate, the opening of the hollow permeation membrane 3'is adhered, but on the outlet side 11 of the mixed solution of solute and solvent, the opening of the permeation membrane 3'is not adhered. .

The solvent flowing in from the solvent condensation inlet 2'flows in from the outer peripheral portion of the permeation membrane 3 ', passes through the inside of the hollow permeation membrane 3', and is sent out to the condensate passage 1 side. Here, the solvent that has permeated is thoroughly mixed with the mixed liquid 4 in the wide space immediately after the outlet side 11 and then sent out to the condensate passage 1, and the flow velocity in the hollow permeation membrane 3'is It is a very slow flow. Therefore, the diffusion speed of the mixed liquid becomes sufficiently high, and the condensed liquid can be stably sent out even if the flow rate increases due to a high heat load. The permeation membrane 3'has a structure with very small holes of 10 to 50 Å and is easily clogged, but since the condensed clean solvent always flows in from the outside and flows inside, it has a cleaning action, Hard to clog. However, when impurities are present on the inner wall surface of the container, the outer surface of the permeable membrane 3'is clogged, pressure loss increases, and heat transfer efficiency decreases. In this way, the replacement lid 12 is provided in the present embodiment so that the permeable membrane can be easily replaced even when clogging occurs.

FIG. 3 is a diagram showing the relationship between the osmotic pressure, which is the drive pressure source for the condensate, and the concentration of the mixture. As shown in the figure, the osmotic pressure is about 3.5 kg / cm ² even with saline solution of seawater concentration,
The drive pressure for supplying condensed water can be increased. The driving pressure of the conventional heat pipe utilizing the surface tension of the wick type is 0.02 to 0.05 kg / cm ² , so the difference is large.

As described above, in the osmotic pressure heat pipe, the driving pressure of the condensate is large, and even if the heat pipe is thinned to increase the pressure loss, a sufficient driving pressure is generated. Suitable for cooling electronic devices with

Table 1 shows an example of specifications of a conventional wick type thin heat pipe developed for use in cooling electronic devices (outer diameter
3.1mm, length 30cm).

In the table, No. 1 is a standard diameter heat pipe (outer diameter 4.7 mm) for comparison, and No. 2 is a small diameter heat pipe for cooling electronic equipment. Both heat pipes are made of copper inside. 1
A wire mesh wick of 00 mesh is enclosed. 4 (a) and 4 (b) are actual measurement examples of the heat transfer amount of the heat pipes of No. 1 and No. 2, and when the diameter of the heat pipe is reduced from FIG. The heat transport capacity is
It turns out that it falls extremely. The maximum heat transport capacity when the outer diameter is reduced to 3.1 mm is about 2 W, and this diameter seems to be a practical limit. When the outer diameter is 3.1 mm, the influence of the pressure loss inside the wick is dominant, so the influence of the installation angle of the heat pipe on the maximum heat transfer amount does not appear so significantly, but the heat pipe of the standard diameter Therefore, the influence of the installation angle appears significantly, and it can be seen that the use of the wick type in the top heat mode in which the condensate is supplied against gravity is extremely disadvantageous.

Table 2 is a table showing a comparison between the osmotic pressure type heat pipe of the present invention and the conventional heat pipe. In each heat pipe, the cross-sectional area and length of the condensate passing portion corresponded to an inner diameter of 5 mm and a length of 1 m.

As shown in the table, due to the effect of increasing the driving pressure and reducing the pressure loss due to the osmotic pressure of the present invention, a conventional wick type or loop type low pressure loss type heat pipe having a wick at the inlet and outlet ends of the condensation passage can be provided. In comparison, it can be seen that the heat transport capacity of the heat pipe of the present invention is significantly improved.

Similarly, Table 3 compares the heat transport distance of 200 W with an inner diameter of 5 mm.

From the table, it can be seen that the effect of improving the heat transport distance according to the present invention is remarkable.

As described above, the present invention is suitable for reducing the diameter of the heat pipe.

FIGS. 5A and 5B show another embodiment of the present invention, which is an example applied to cooling a high density integrated circuit. In the cooling plate 13, the mixed liquid passage 14 is conducted and cooled, flows into the gas-liquid separation chamber 16 from the vapor outlet 15, is condensed in the condensing cooling unit 17, and the condensed liquid is discharged from the outside of the hollow permeation membrane 3 '. It permeates and is supplied to the mixed liquid passage 14 through the inside. The cooling plate 13 is fixed to the upper surface of the centipede type high-density integrated circuit 18 with a heat conductive adhesive and is configured to radiate heat to the cooling plate 13. The mixed liquid passage 14 has a two-phase flow in which vapor and liquid are mixed, resulting in a large pressure loss, but since the driving pressure itself is large, it has a sufficient heat transport capacity.

FIG. 6 shows a cooling plate 13 'according to still another embodiment of the present invention.
Is made into one large plate, and the mixed liquid passage 14 'is provided inside thereof.
Is an example in which is provided. The cooling plate 13 'covers a large number of flat package type high density integrated circuits 18', and the circuit board 1 '
9 is fastened together with the screw 9 and screwed to fix the flat package type high density integrated circuit 18 'and allow it to cool from the contact surface to the cooling plate 13'. With such a structure, maintenance and inspection of the circuit becomes easy.

FIG. 7 shows another embodiment of the present invention, which is applied to the cooling of space equipment. In the weightless environment of the universe, the mixed liquid 4 easily flows out by an external force at the exit end of the condensate passage 1,
The structure is such that it is closed with a wick 6. Furthermore, since the droplets scattered when the mixed liquid 4 is boiled by the wick 6 easily move to the vapor passage 2 as well, the spiral guide vane 20
Is provided so that the vapor flow is given a rotational motion, and the liquid droplets are collected on the wall surface by the centrifugal force and collected in the portion of the dam plate 21. The stored mixed liquid is returned to the wick 6, which is an evaporation section, by a wick passage 22 for reflux, which connects the vicinity of the damming plate 21 and an opening provided in the wick 6. In FIG. 7, reference numeral 3 indicates a permeable membrane partition wall, and 5 indicates a solvent.

FIG. 8 shows still another embodiment of the present invention. In this embodiment, since the heat load is very small and the flow velocity of steam is slow, a measure is taken when the mixed liquid 4 moves to the solvent 5 side due to a large external force applied during the operation in which the centrifugal force is small. is there. The wick passage 22 'for reflux has a structure in which the solvent 5 side and the evaporation side wick 6 are connected.
That is, an opening is provided on the upstream side of the permeable membrane partition wall 3 and the wick 6, and these openings are connected by the wick passage 22 '.

In the structure of this embodiment, the condensate is mainly concentrated in the condensate passage 1 during normal use, in which the concentration difference between the mixed liquid 4 and the solvent 5 is large.
It is carried to the evaporation section through the. However, when the solute gradually moves to the solvent 5 side, the concentration difference between the solvent 5 and the mixed solution 4 decreases, and the osmotic pressure decreases, the solvent 5 having a higher concentration evaporates through the reflux wick passage 22 '. Since the mixed solution 4 is returned to the side wick 6 and diluted with the condensate, the mixed solution 4 returns to its original state in which the difference in concentration of the solvent 5 has been restored. In the figure, reference numeral 2 is a steam passage.

It is desirable that space cooling equipment be light in weight and have excellent heat transport capability. As a measure of its performance, FIG. 9 compares the products of the amount of heat transported per unit weight and the transport distance for each heat exchange device. As shown in the figure, the heat pipe of the present invention has a larger heat transport amount per unit weight than the conventional wick type heat pipe. In addition, since heat exchange equipment is used, compared with heat transportation by pump drive, pressure loss in the permeation membrane is added, so long-range transportation capacity is inferior, or a heavy pump is not required, so heat dissipation equipment The present invention excels in short-distance heat transport capacity, which is in high demand.

〔The invention's effect〕

As described above, according to the heat pipe of the present invention, the condensate passage and the vapor passage are independently configured, the condensate passage inlet end is partitioned by the osmotic membrane, and the condensate passage outlet end is partitioned by the wick. Moreover, since the solvent is arranged around the permeation membrane and the mixed solution of the solute and the solvent is accommodated in the permeation membrane, it becomes possible to reduce the pressure loss as compared with the conventional one. It has an effect that the heat transfer performance can be improved. Further, since the heat exchange in the condensing portion is directly performed through the tube wall, there is an effect that the heat transport efficiency can be improved. In addition, if the present heat pipe is used in a long-distance heat transport system that is supplied by a pump or the like, moving parts such as a pump and a valve are not required, so that the reliability of the heat transport system can be improved. Further, since the driving pressure of the condensate is high and the pressure loss is small, it is possible to use a heat pipe having a small diameter and reduce the weight. For this reason, it is suitable for applications such as aircrafts and spacecrafts where the weight of loaded equipment is required to be small.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a heat pipe according to the present invention, FIG. 2 is a partially cutaway perspective view showing another embodiment of the present invention, and FIG. 3 is a mixture liquid concentration and osmotic pressure. Diagram showing the relationship,
4 (a) and 4 (b) are views showing the performance of the wick type heat pipe, and FIGS. 5 (a), 5 (b) and 6 are schematic configurations showing other embodiments of the heat pipe of the present invention. Figure,
FIG. 7 and FIG. 8 are schematic configuration diagrams showing still another embodiment of the heat pipe of the present invention, and FIG. 9 is a diagram showing the relationship between the heat transport distance and the heat transport amount per unit gravity. 1 ... Condensate passage, 2 ... Vapor passage, 3 ... Permeation membrane partition wall, 3 '... Hollow permeation membrane, 4 ... Mixed liquid, 5 ... Solvent, 6 ... Wick, 20 ... Guide vane , 21 ……
Dams, 22, 22 '... Wick passages.

Claims (4)

[Claims] 1. A condensate passage and a vapor passage are formed independently of each other, an inlet end of the condensate passage is partitioned by a permeable membrane, an outlet end of the condensate passage is partitioned by a wick, and a solvent is arranged around the permeable membrane. A heat pipe characterized in that a mixed solution of a solute and a solvent is contained in the osmotic membrane. 2. The heat pipe according to claim 1, wherein the permeable membrane is formed in a pleated shape. 3. A spiral vane for imparting a swirling motion to the steam flow is provided on the wall surface of the steam passage, and a damming plate having an opening at the center is provided on the downstream side of the vane.
In order to recirculate the liquid accumulated in the dam plate, openings are provided in the vicinity of the dam plate and the wick partition wall, and a reflux passage is formed by connecting these openings with a flow path having a wick inside. The heat pipe according to claim 1 or 2, which is characterized. 4. A reflux passage, wherein openings are provided on the upstream side of the permeation membrane where the solvent condensate is collected and on the wick partition, and these openings are connected by a passage having a wick inside. The heat pipe according to claim 1 or 2.