JPS599831B2 - Heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in heat exchangers using heat pipes.

2. Description of the Related Art Conventionally, heat exchangers using heat pipes have been used in air conditioning and various industrial processes, for example, as a means for recovering waste heat.

In this heat exchanger, the heat pipe is arranged in the direction of gravity or inclined with respect to the direction of gravity, and the boiling side of the heat pipe (
High-temperature gas is passed through and in contact with the condensing side (heat receiving part) of the same pipe.
The structure is such that low-temperature gas is brought into contact with the heat dissipating section) to exchange heat between the gases.

Recently, heat exchangers have been developed that further improve the performance of heat exchangers by attaching fins all around the outer surface of the heat pipe to improve the heat transfer performance of the heat pipe. ing.

However, this type of heat exchanger has the following problems.

In other words, the heat transfer performance of the heat pipe is improved because the fins are attached to the entire outer circumference of the heat pipe, but on the heat receiving part side of the heat pipe, the vapor of the working fluid inside the pipe is heated too much, resulting in a so-called dry state. Outs are likely to occur.

When dryout occurs, the heat transfer performance of the heat pipe decreases, and impurities in the working fluid are deposited on the inner surface of the heat pipe, which may lead to corrosion of the heat pipe.

In addition, since the fins are attached all around the outer surface of the heat pipe, the resistance to gas passing through the outer surface of the heat pipe increases, which causes problems such as an increase in the capacity of the heat exchanger's blower. there were.

The present invention has been made in consideration of the above circumstances, and its purpose is to not only improve the heat transfer performance of the heat pipe, but also to prevent dryout within the heat pipe, and to reduce ventilation resistance. It is an object of the present invention to provide a heat exchanger that can be made smaller to reduce blower capacity and the like.

In other words, the present invention provides fins located on the outer peripheral surface of a heat pipe disposed in the direction of gravity or inclined with respect to the direction of gravity, in a direction opposite to the flow direction of the fluid that is brought into flow contact with the heat pipe as the center. By placing it on one side,
The aim was to achieve the above objective.

The details of this invention will be explained below with reference to illustrated embodiments.

FIG. 1 is a schematic cross-sectional view showing the schematic configuration of one embodiment.

In the figure, 1 is a rectangular cylinder forming a ventilation duct, and this rectangular cylinder 1
is arranged so that its axis line is inclined by approximately 4 degrees with respect to the direction of gravity A.

A partition plate 2 is provided inside the rectangular cylinder 1 to divide the inside of the rectangular cylinder 1 into two, and the partition plate 2 forms a hot air passage 1a and a cold air passage 1b.

Furthermore, inside the rectangular cylinder 1, a large number of heat pipes 3 are arranged at regular intervals in the direction along the passage and in the direction orthogonal to the above direction, as shown in FIG. has been done.

As shown enlarged in FIG. 3, semicircular plate-shaped fins 4a and 4b are attached to the outer peripheral surface of each heat pipe 3, respectively.

That is, a large number of fins 4b are attached to the so-called lower surface of the heat receiving portion X of the heat pipe 3 at regular intervals along the axial direction of the heat pipe 3.

High-temperature gas such as waste heat is introduced into the hot-air passage 1a from diagonally below by a blower or the like (not shown), and low-temperature gas such as room-temperature air is introduced into the cold-air passage 1b from diagonally above. .

With such a configuration, when high-temperature gas is blown into the hot-air passage 1a and low-temperature air is blown into the cold-air passage 1b, the high-temperature gas first hits the fins 4a of the heat receiving section X when passing through the passage 1a. It takes away the heat.

That is, the heat of the high-temperature gas is transferred to the fins 4a of the heat receiving section X.

The heat transferred to the fins 4a is then transferred to the working liquid 5 within the heat pipe 3.

Therefore, in the heat receiving part X of the heat pipe 3, as shown in FIG.
As shown in the figure, the working liquid 5 collected downward by gravity is heated by the action of the fins 4a and partially evaporates to form a vapor 6.
becomes.

This steam 6 moves upward and further moves to the heat radiation part Y of the heat pipe 3.

At this time, since the steam 6 always exists above the heat pipe 3, that is, on the side where the fins 4a are not attached, the steam 6 is not overheated and dry-out is less likely to occur.

Further, since heating by hot air is mainly performed via the working liquid 5, the heat transfer performance of the heat pipe 3 is almost unchanged compared to the case where there are fins on the upper surface.

゛ On the other hand, on the heat radiation part Y side of the heat pipe 3,
As shown in the figure, the steam 6 rising due to evaporation reaches the fin 4b.
The heat is removed from the liquid, cooled, and condensed above the heat pipe 3 to form a liquid 5.

This liquid 5 moves downward along the inner surface of the heat pipe 3 due to gravity, and further moves to the heat receiving section X side of the heat pipe 3.

In this case, the liquid film on the inner surface of the portion of the heat dissipating section Y where the fins 4b are located is always thin, and cooling by cold air is mainly achieved through the vapor 6 of the working liquid 5. The condensation action of the steam 6 is performed without deteriorating the heat transfer performance of the heat pipe 3.

Further, at this time, the liquid film is thick in the lower part of the heat dissipating part Y, that is, in the part where the fins 4b are not provided, so that almost no condensation action is performed.

Therefore, the heat transfer performance of the heat pipe 3 hardly deteriorates compared to a heat pipe that also has fins at the bottom.

In this way, the working liquid 5 within the heat pipe 3 repeatedly evaporates and condenses and circulates within the pipe 3, resulting in heat exchange between the hot air and the cold air.

As described above, in this embodiment, the fins 4a are attached only to the so-called lower surface of the heat receiving part X of the heat pipe 3, which is arranged at an angle with respect to the direction of gravity, so that fluid can flow around the heat pipe 3. The heat receiving part X is biased in the opposite direction.
It has side fins.

Therefore, dryout due to excessive heating of the vapor 6 of the working liquid 5 in the heat pipe 3 can be prevented.

Further, since the part of the heat receiving part X of the heat pipe 3 that particularly contributes to heat transfer is the lower surface side, the ventilation resistance can be reduced without reducing the heat transfer performance of the heat pipe 3, and the blower capacity can be reduced.

That is, the heat transfer performance of the heat pipe can be improved for the same blower capacity.

Furthermore, in the heat dissipation part Y of the heat pipe 3, the fins 4b are provided only on the so-called upper surface side, but since the part of the heat dissipation part Y that contributes to heat transfer is almost only on the upper surface side, the heat transfer performance of the heat pipe 3 is There are advantages such as being able to further reduce ventilation resistance without lowering it.

In the above-described embodiment, the heat pipe 3 is arranged at an angle of 45 degrees with respect to the direction of gravity, but even if the heat pipe 3 is arranged along the direction of gravity, the above-mentioned effect, that is, dryout, does not occur. Effects such as improving the heat transfer performance of the heat pipe 3 and reducing the blower capacity can be obtained.

According to experiments conducted by the present inventors, using three types of human pipes: a vertical full-circumference fin P1, a vertical half-circumference fin Q, and a 45° inclined half-circumference fin R, the specific heat transfer coefficient P1 on the heat receiving part side of these
, Q1, R1 and the specific heat transfer coefficient P2, Q2 on the heat radiation part side
1 R2 was measured, and the results shown in FIGS. 5 and 6 were obtained, respectively.

In FIG. 5, the horizontal axis shows the specific heat flux (non-dimensional heat exchange amount), and the vertical axis shows the specific heat transfer coefficient (non-dimensional boiling heat transfer coefficient).

As is clear from this figure, dryout occurs in the vertical full-circumference fin P when the specific heat flux is 1.1, but dryout does not occur in the vertical half-circumference fin Q until the specific heat flux reaches twice that.

That is, it can be seen that the vertical half-circumference fin Q can be used up to a higher specific heat flux than the vertical full-circumference fin P.

Furthermore, the effect was even greater with the 45° inclined half-circumferential fin R.

Similarly, regarding the heat dissipation part, as shown in FIG. 6, the specific heat transfer coefficient (dimensionalized condensation heat transfer coefficient) of the vertical half-circumference fin Q was improved by 70 points compared to the vertical full-circumference fin P.

Furthermore, in the 45° inclined half-circumference fin R, the vertical full-circumference fin P
Its specific heat transfer coefficient has been improved by more than twice that of the previous one.

In addition, when the fin-side heat transfer coefficient with respect to pressure loss per row was measured for full-circumference fins and half-circumference fins,
As shown in FIG. 7, the curve T showing the heat transfer coefficient of the half circumference fin is higher than the curve S showing the heat transfer coefficient of the full circumference fin.

This shows that for the same pressure loss, half-circumference fins have a higher heat transfer coefficient than full-circumference fins.Conversely, to obtain the same heat transfer coefficient, half-circumference fins are better than full-circumference fins. This results in a small pressure drop, which means a small blower capacity.

As described above, it is most preferable that the heat pipe 3 having the half-circumference fins be installed at an angle with respect to the direction of gravity, but even if it is installed along the direction of gravity, the heat pipe 3 having the half-circumference fins is not as good as the conventional full-circumference fins. This will give you a great effect.

Note that this invention is not limited to the embodiments described above.

For example, the fins may be provided on the downstream side of the heat pipe where the fluid to be brought into contact with the heat pipe flows due to manufacturing reasons. It needs to be made smaller.

Moreover, it goes without saying that the shape, material, etc. of the fins may be determined as appropriate depending on the specifications.

Furthermore, the inclination angle of the heat pipe can also be changed according to specifications.

In addition, various modifications can be made without departing from the gist of the invention.

As described in detail above, according to the present invention, the fins of the heat pipe disposed in the direction of gravity or inclined with respect to the direction of gravity are arranged in the direction of flow of the fluid that is caused to flow into contact with the heat pipe, respectively, with the heat pipe as the center. To provide a heat exchanger which not only improves the heat transfer performance within the heat pipe but also prevents dry-out from occurring and reduces the blower capacity because the heat exchanger is installed offset in the opposite direction. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an embodiment of the present invention, FIG. 2 is a view taken along the arrow B-B in FIG. 1, and FIG. 3 is a perspective view showing the main configuration of the above embodiment. , FIGS. 4a and 4b are diagrams for explaining the effects of the above-mentioned embodiment, and FIGS. 5 to 7 are diagrams for explaining the effects of the present invention. FIG. Characteristic diagram showing the specific heat transfer coefficient of the side, No. 6
The figure is a characteristic diagram showing the specific heat transfer coefficient on the heat radiation part side with respect to (1/specific heat flux), and FIG. 7 is a characteristic diagram showing the heat transfer coefficient with respect to pressure loss. 1... Square tube body, 2... Partition plate, 3...
... Heat pipe, 4a, 4b ... Fin, 5 ... Working liquid, 6 ... Steam, X.
... Heat receiving section, Y ... Heat dissipating section.

Claims (1)

[Claims] 1. A high temperature fluid is passed through and brought into contact with a heat receiving part located below a heat pipe having fins attached to the outer peripheral surface thereof, and a low temperature fluid is brought into contact with a heat radiating part located above the heat pipe. In the heat exchanger for exchanging heat between the respective fluids, the fluid is caused to flow and contact at least one of the fins of the heat pipe located on the outer peripheral surface of the heat receiving part with the heat pipe as the center. A heat exchanger characterized by being installed offset in the opposite direction. 2. Claim 1, wherein the heat pipe is arranged obliquely with respect to the direction of gravity.
Heat exchanger as described in section. 3. Claim 1, characterized in that the fins located on the heat receiving part side and the heat radiating part side of the heat pipe are provided offset in a direction opposite to the flow direction of the fluid to be brought into contact with the heat pipe. Heat exchanger as described.