JPH0535353B2 - - Google Patents

Description

Detailed Description of the Invention: Industrial Application Field This invention transports heat as the latent heat of vaporization of the working fluid by evaporating and liquefying a condensable working fluid sealed inside a sealed tube and circulating it in the vertical direction. This relates to a thermosyphon that performs.

BACKGROUND TECHNOLOGY A thermosiphon basically consists of evacuating a non-condensable gas such as air from the inside of a sealed tube and then sealing in a condensable fluid such as water as a working fluid.
The working fluid is evaporated by applying heat to the lower end of the sealed tube, which is installed almost vertically.
At the same time, by removing heat from the upper end of the sealed tube,
The working fluid vapor is condensed and liquefied at the upper end of the closed tube,
Furthermore, the liquefied working fluid is caused to flow down along the inner surface of the sealed tube, and as a result, heat is transferred as latent heat of vaporization of the working fluid. Therefore, thermosiphons are simple in construction and can transport heat without requiring external power, making it possible to collect geothermal heat or extract heat from underground to store cold heat underground. It can be considered to be used for such purposes.

However, in the general thermosiphon described above, the working fluid is configured to flow down the inner surface of a sealed tube, so the condensed and liquefied working fluid is distributed over the entire inner circumferential surface of the evaporator where heat is input from the outside. It is not always possible to sufficiently disperse the working fluid, and the flow direction of the working fluid and the working fluid vapor are opposite, resulting in opposing flows. There is a problem in that the heat is scattered by the steam flow, resulting in a shortage of working fluid in the evaporator, which limits the amount of heat transport. A thermosiphon having the configuration shown in FIG. 4 has been proposed as a thermosiphon capable of solving such problems.
This has a heat dissipation/liquid reservoir part 3 with fins 2 attached to the upper end of the sealed tube 1, and a distribution pipe 4 with many small holes formed in the peripheral wall at the bottom of the heat dissipation/liquid reservoir part 3. At the same time, the lower end side of the distribution pipe 4 is drawn in from the outside of the sealed tube 1 to the inside through the peripheral wall, and non-condensable gas such as air is evacuated from the inside of the sealed tube 1. In this state, a condensable fluid such as water is sealed as a working fluid. A thermosyphon with such a configuration applies heat Q to the lower end of the sealed tube 1 that is vertically erected with the heat dissipation/liquid reservoir section 3 on the upper side, and removes heat Q from the heat dissipation/liquid reservoir section 3. For example, the working fluid vapor flows upward inside the sealed tube 1 to the heat dissipation/liquid reservoir section 3.
The resulting working fluid flows down through the distribution pipe 4 and is distributed and supplied to the entire inner circumferential surface of the sealed pipe 1.

Problems to be Solved by the Invention However, in the conventional thermosiphon shown in FIG. There were manufacturing problems such as difficulty in pulling the device into the interior of the device and fixing it in the desired position.

Therefore, the present applicant and others developed a thermosiphon that separates a working fluid flow path and a steam flow path using an inner tube in which a large number of ventilation holes are formed. Although this thermosiphon can sufficiently disperse and supply the working fluid,
When the vent hole is made circular due to processing considerations, depending on the opening diameter, it may obstruct the flow of working fluid vapor, or conversely, it may become impossible to perform gas-liquid separation reliably. .

This invention was made in view of the above circumstances, and it is possible to reliably separate the working fluid flow and its vapor flow.
Further, it is an object of the present invention to provide a thermosiphon with good heat transport properties.

Means for Solving the Problems In order to achieve the above object, the present invention provides an outer tube of a closed structure, which is arranged vertically and whose lower end serves as a heating section and whose upper end serves as a heat dissipation section. Inside the outer tube is an inner tube which encloses only a condensable working fluid and which is smaller in diameter and shorter than the outer tube, has at least an open upper end, and has a large number of ventilation holes. In _a vertical thermosiphon _inserted and arranged concentrically in It is characterized by having holes. Here, σ is the surface tension of the liquid-phase working fluid, g is the gravitational acceleration, ρ _l is the density of the liquid-phase working fluid, and ρ _v is the density of the gas-phase working fluid.

Function: Also in the thermosiphon of the present invention, the working fluid evaporates and flows toward the upper end, and then radiates heat and liquefies, thereby transporting heat as the latent heat of evaporation of the working fluid. In this case, in this invention, since the working fluid is liquefied and flows down along the inner surface of the outer tube, there is a large flow resistance to the working fluid vapor between the outer tube and the inner tube, and as a result, the working fluid vapor flows into the inner tube. It enters the inner circumferential side of the inner tube through the vent hole formed in the tube and flows toward the upper end of the inner circumferential side of the inner tube. Furthermore, since the vent hole is the long hole described above, a film formed by the working fluid is formed partially, so that passage of the working fluid is prevented, and passage of the working fluid vapor is facilitated. Therefore, in the present invention, the liquid-phase working fluid and the gas-phase working fluid are well separated.

Embodiments Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention, in which an outer tube 10 having a closed structure is installed with its axis facing in the vertical direction, and inside the outer tube 10 there is a tube with a diameter smaller than that of the outer tube 10. In addition, a short inner tube 11 is inserted and arranged concentrically, and a non-condensable gas such as air that does not condense at the intended operating temperature is evacuated inside the outer tube 10. A condensable fluid such as water or ethyl alcohol is sealed as a working fluid 12. Furthermore, approximately the lower half of the outer tube 10 is a heating section 13 into which heat is input from the outside.
Further, the upper end portion serves as a heat radiating portion 14 from which heat is removed to the outside, and a heat insulating portion 15 from which heat does not enter or exit is set between the two. The inner tube 11 is open at least at its upper end, and has a large number of ventilation holes 16 formed in a portion corresponding to the heating section 13, and a simple cylindrical portion corresponding to the heat insulating section 15. ing. As shown in an enlarged view in FIG. 2, the ventilation hole 16 is a long hole inclined at an angle of, for example, 30 to 60 degrees with respect to the axis of the inner tube 11, and its length 1 is such that a film of hydraulic fluid is spread over the entire surface. The width W is set to be longer than the Taylor wavelength λ (specifically, about 3 times) so that the width W is smaller than the Taylor wavelength λ. Here, the Taylor wavelength λ is a critical dimension in which a liquid film occurs, and is defined by the following equation.

λ=2π√( _l − _v ) where σ is the surface tension of the liquid phase working fluid, g is the gravitational acceleration, ρ _l is the density of the liquid phase working fluid, and ρ _v is the density of the gas phase working fluid.

The above-mentioned thermosiphon is used facing upward and downward as shown in Fig. 1, and when heat Q is applied to the heating section 13, the working fluid 12 evaporates, and the evaporation flows to the heat dissipation section 14 where the pressure is low. It radiates heat there and condenses. That is, heat is transported as latent heat of the working fluid 12. Working fluid 12 condensed in heat radiation section 14
flows down along the inner wall surface of the outer tube 10 and also adheres to the outer wall surface of the inner tube 11, but the ventilation hole 16 formed in the inner tube 11 allows the Taylor wavelength λ to
Since the hole is longer and has a width less than the Taylor wavelength λ, the working fluid 12 in the liquid phase passes through the vent hole 16 to the extent that a liquid film is partially formed on the vent hole 16 and reaches the inner periphery of the inner tube 11. There is no active flow into the side,
Therefore, the working fluid flows between the outer tube 10 and the inner tube 11 to the heating section 13 side. In addition, the working fluid vapor is not completely closed off by the liquid film, but is partially open, and the resistance between the outer tube 10 and the inner tube 11 is large, so the working fluid vapor does not flow through the vent hole 16. 16 and flows into the inner peripheral side of the inner tube 11, and flows there as a flow path toward the heat radiating part 14. That is, in the above thermosiphon, the flow path of the vapor flow toward the heat radiation section 14 and the liquid flow returning to the heating section 13 can be reliably separated, and as a result, the heat transport characteristics can be improved. can.

Note that the working fluid that forms a liquid film on the vent hole 16 is
It evaporates due to the heat input to the heating section 13, and therefore the liquid film in the vent hole 16 is repeatedly formed and disappears.

In the embodiment described above, the vent hole 16 is inclined with respect to the axis of the inner tube 11, but the vent hole in the present invention is not limited to the configuration shown in the above embodiment. As shown, it may be a long hole along the axial direction.

Effects of the Invention As explained above, in the thermosiphon of the present invention, the vent hole formed in the inner tube is a long hole with a length longer than the Taylor wavelength and a width less than the Taylor wavelength. In addition, the hydraulic fluid does not pass through the vent hole and actively flow into the inner circumferential side of the inner pipe. Therefore, in this invention, the hydraulic fluid and its vapor can be reliably separated. , the reflux of the working fluid and the flow of the working fluid vapor can be smoothed, and the heat transport ability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a thermosiphon according to the present invention, FIG. 2 is an enlarged diagram showing the shape of its ventilation hole, FIG. 3 is a schematic diagram showing another example of the present invention, and FIG. FIG. 1 is a schematic diagram showing an example of a conventional thermosiphon. 10... Outer tube, 11... Inner tube, 12... Working fluid, 13... Heating section, 14... Heat radiation section, 16...
Vent hole, l... Length of the vent hole, W... Width of the vent hole.

Claims (1)

[Claims] 1. An outer tube that is arranged vertically and has a closed structure with a lower end serving as a heating section and an upper end serving as a heat dissipating section, in which substantially only a condensable working fluid is supplied. In a vertical thermosiphon, an inner tube, which is enclosed and has a smaller diameter and shorter length than the outer tube, is open at least at its upper end, and has a large number of ventilation holes, is inserted concentrically into the outer tube. A gas-liquid separation type vertical thermosiphon characterized in that the pores are elongated holes with a length longer than the Taylor wavelength λ and a width less than the Taylor wavelength λ defined by the following formula. λ=2π√( _l − _v ) where σ is the surface tension of the liquid phase working fluid g is the gravitational acceleration ρ _l is the density of the liquid phase working fluid ρ _v is the density of the gas phase working fluid