JPH02197793A - Horizontal evaporating tube for heat exchanger - Google Patents

Abstract

PURPOSE:To permit the obtaining of a horizontal evaporating tube, easy in removing dust, in manufacturing of a thin cylindrical body, to be inserted into the evaporating tube, and in attaching the cylindrical body to the inside of the evaporating tube, and improved remarkably in evaporating heat transfer rate in the tube, by inserting the thin cylindrical body, having a specified thickness, into the tube. CONSTITUTION:A thin cylindrical body 6, having a diameter slightly smaller than the inner diameter of a horizontal evaporating tube 1, the lower part thereof is contacted with the tube 1 closely, the gap 7 thereof between the inner wall of the tube 1 is increased gradually toward the upper part of the tube 1 and provided with a slit type steam flowing passage 8 continuously from the end of the cylindrical body 6 to the other end of the same body 6, is inserted into the horizontal evaporating tube 1. In this case, the inside lower part 10 of the thin cylindrical body 6 and the outside lower part 11 of the thin cylindrical body 6 become a communicating port in the reservoir of operating liquid. The operating liquid in the outside lower part 11 is pushed upward by the surface tension of the operating liquid to increase a contact area between the inner wall of the evaporating tube and the outer wall of the cylindrical body while the gap 7 is increased gradually toward the upper part of the tube and, therefore, generated bubbles and vapor are pushed up without any resistance while being heated further whereby a high heat transfer rate may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a horizontal evaporation tube of a heat exchanger applying the principle of a heat pipe.

[Conventional technology]

A heat pipe is a sealed tube that is evacuated and filled with working fluid.
It heats one end to evaporate the working fluid, and condenses it at the other end to release heat.It has excellent heat transfer properties and is also called a transcendental conductor.

Applying this principle, a heat exchanger has been developed in which a closed circuit is formed by connecting the evaporation tube and the condensation tube with a steam tube and a condensate tube, the inside is evacuated, and the working fluid is sealed. It has been used for various purposes.

The heat transfer coefficient in the evaporation tube accounts for a large proportion of the amount of heat exchanged in such a heat exchanger.In particular, in the tube that involves evaporation, a gas phase and a liquid phase are formed, and the heat transfer coefficient in the gas phase is Very low ℃・
Therefore, the evaporator tubes are installed vertically to form an annular flow in order to improve the heat transfer coefficient. However, since the effective length of the annular flow is short compared to the length of the evaporator tube, the heat transfer coefficient is not very high. Furthermore, when a heat source containing dust such as exhaust gas is used for heating, the dust adheres to the outer surface of the evaporation tube, reducing the heat transfer coefficient on the outer surface of the tube.

Therefore, it is necessary to remove this dust, but since fins are provided on the outer surface of the tube to increase the heat transfer area, it has been extremely difficult to remove the dust.

In view of this, as a result of various studies, the inventors of the present invention first developed a heat exchanger that could easily take measures against dust and obtain a high heat transfer coefficient in the pipes.
I proposed it as No. 150.

As roughly shown in Figure 2, this heat exchanger has an evaporator tube (1) arranged horizontally, and a condensing tube (2) and an evaporator tube fl) connected to a steam tube (
3) is connected to the condensate pipe (4), the inside is evacuated and the working fluid (5) is sealed, and a certain amount of the working fluid (5) can be held in the evaporation pipe (1). It is. According to this heat exchanger, dust adhering to the outer surface of the evaporator tube +1) can be easily removed by water washing and/or a shot cleaning system.

[Problem that the invention seeks to solve]

The above heat exchanger using horizontal evaporator tubes not only makes it easy to remove dust, but also provides a heat transfer coefficient that is almost equal to or higher than that of the heat exchanger using vertical evaporator tubes, but the heat transfer coefficient is not as high. , - layer improvement is desired.

In addition, in order to obtain a high heat transfer coefficient, it has been proposed that a tubular body with a drum-shaped cross section is attached inside the evaporation tube (Utility Model Publication No. 49-6746), but it is difficult to manufacture the tubular body and attach it to the evaporation tube. This is difficult, and there are problems such as high steam flow resistance.

[Means for solving problems]

As a result of further investigation into the above-mentioned problems, the present inventors have developed a horizontal evaporation tube that is easy to manufacture and provides a high heat transfer coefficient.
In an evaporation tube that heats and evaporates the internal working fluid from the outside, the lower part of the tube is in close contact with the limb canal, and the upper part gradually increases in the upward direction between the inner wall of the limb pipe and the upper axial direction. A thin cylindrical body having continuous or discontinuous slit-shaped vapor flow ports is inserted into the cylindrical body.

That is, the present invention has a thin cylindrical body (6) with a diameter somewhat smaller than the inner diameter of the limb tube (1), which is installed in the evaporation tube (1) installed horizontally as shown in FIGS. The upper part of the thin-walled cylindrical body (6) is arranged so that the lower part is in close contact with the limb canal, and the upper part is arranged so that a slit (7) gradually increases between the upper part and the inner wall of the limb canal (1). One thin-walled cylindrical body (6
) is inserted. In this case, the inner lower part α1 of the thin-walled cylindrical body (6) and the outer lower part αυ of the thin-walled cylindrical body (6) serve as reservoirs of hydraulic fluid and flow ports. The above is a thin cylindrical body (6
), the slit-shaped vapor flow port (8) is provided continuously from one end of the cylinder (6) to the other in the upper axial direction, but the invention is not limited to this. A steam vent may be provided.

The above is a case where the evaporation tube is relatively short. Furthermore, if the evaporation tube is long, a plurality of hydraulic fluid reservoirs are installed in the axial direction of the lower hydraulic fluid reservoir of the cylindrical body (6) in order to facilitate the flow of the working fluid from the inner lower part α [to the outer lower aυ] of the cylindrical body (6). A hole (not shown) may be provided to serve as a hydraulic fluid flow port. In addition, in the figure (9)
indicates the fins provided on the outer surface of the tube to increase the heat transfer area.

[For production]

A thin-walled cylindrical body (6) with a somewhat small diameter is inserted into the horizontal evaporation tube (1) to form a slit (7) that gradually increases upward between the inner wall of the evaporation tube and the outer wall of the thin-walled cylinder. As a result, 00 parts of the working fluid is pushed upward by the surface tension of the working fluid, increasing the contact area between the inner wall of the evaporator tube and the outer wall of the cylindrical body, and the slit gradually increases upward. As the bubbles and steam generated are further heated, they are pushed upwards, resulting in a high heat transfer coefficient, and the smaller the slit, the more effective it is.Also, if the horizontal evaporation tube is short, , the working fluid inside the cylinder (6) θG can be supplied from the openings at both ends of the cylinder (6) to the liquid reservoir aυ outside the cylinder (6), but if the horizontal evaporation pipe is long, In this case, the supply of working fluid from the inside 11 of the thin-walled cylinder to the outside θυ becomes insufficient, causing dryout.

In this case, a plurality of holes are appropriately provided in the axial direction of the lower hydraulic fluid reservoir of the thin-walled cylindrical body to serve as hydraulic fluid flow ports to ensure a sufficient supply of hydraulic fluid.

〔Example〕

A stainless steel tube with an outer diameter of 60.5 mm, a wall thickness of 1.5 mm, an inner diameter of 57.5 mm, and a length of 132C1+x has a height of 12.7 mm on the outer periphery.
Tomo, horizontal evaporation tube with radial fins of pitch 4.5, fin light diameter 27,113+m, fin outer diameter 51
．． Using a condensing tube made of 25111 fin tube,
The thermal cycle shown in Figure 2 is formed, and the first
As shown in figures (a) and (b), the outer diameter is 45mm, 52y1
m, 57IIIm, length 1000+nm, wall thickness 1.2
Width 15+++mS20mm, 30m111 over the entire length in the upper axial direction of each of the stainless steel tubes of mm
A cylindrical body with a slit-shaped vapor flow opening of 40 mm was inserted into the evaporation tube, and the evaporative heat transfer coefficient within the tube was measured and compared with a case in which the cylindrical body was not inserted into the evaporation tube.

As a result, the evaporative heat transfer coefficient in a is 1 when no cylindrical body is inserted.
500-3000 Kcal/mh″C,
When inserting the cylindrical body, 4000-7000Kcal/ih
improved to 'c. In addition, the evaporative heat transfer coefficient within the tube increases as the outer diameter of the inserted cylinder increases, and the narrower the slit width, the higher the evaporative heat transfer coefficient becomes. was gotten.

〔Effect of the invention〕

According to the present invention, it is easy to remove dust adhering to the outer surface, it is easy to manufacture a thin-walled cylindrical body to be inserted into the evaporation tube, and it is easy to insert it into the evaporation tube, and the evaporation heat transfer coefficient inside the tube is significantly improved. 1- It has a remarkable effect of improving the performance of the heat exchanger.

[Brief explanation of the drawing]

Figures 1 (A) and (B) show an example of the horizontal evaporation tube of the present invention, where (A) is a side sectional view, (ol is a sectional view taken along line A-A of (A), and Figure 2 is a horizontal evaporation tube). It is a conceptual diagram showing an example of a heat exchanger using evaporation tubes. 1... Horizontal evaporation tube, 2... Condensing tube, 3... Steam tube,
4... Condensate pipe, 5... Working fluid, 6... Thin cylindrical body, 7... Slit, 8... Steam flow port, 9... Fin, 1.0, II. Operation Liquid reservoir section, distribution section. Patent applicant Furukawa Electric Co., Ltd.

Claims (2)

[Claims] (1) An evaporation tube that is installed horizontally in the evaporation section of a heat exchanger and heats the internal working fluid from the outside to evaporate it. 1. A horizontal evaporation tube for a heat exchanger, characterized in that a single thin-walled cylindrical body is inserted into which a slit gradually increases between the inner wall and a continuous or discontinuous slit-shaped vapor flow port is formed in the upper axial direction. (2) A plurality of holes are provided in the axial direction of the hydraulic fluid reservoir in the lower part of the thin-walled cylindrical body to form a hydraulic fluid flow port.Claim 1
Horizontal evaporation tube for heat exchanger as described in Section 1.