JPS5810677B2 - Forced heat exchange method - Google Patents

Description

[Detailed description of the invention] (Technical field of invention) The present invention relates to a forced heat exchange method.

More specifically, the present invention relates to a heat exchange method for efficiently exchanging heat using an eccentric double-tube heat exchanger.

(Technical background) To heat or cool a fluid (gas or liquid),
Many of the heat exchangers currently in common use are equipped with a large number of fins (fin plates) to improve heat exchange efficiency.

Its general structure is conceptually illustrated in FIGS. 1 and 2.

FIG. 1 is a front view, and FIG. 2 is a sectional view taken along line A--A in FIG. 1.

As shown in the figure, a heat exchange pipe 3 passes through a large number of fins 2 attached to a frame 1.

The fluid to be heated or cooled usually flows in a direction parallel to the fins 2, as indicated by the arrows in FIG.

The fluid to be heated or cooled receives heat on the surfaces of the fins 2 and the heat exchange pipes 3.

In the heat exchanger having the above structure, the heat exchange pipe 3 is a single-walled pipe whose cross section is circular, oval, or oval.

Oval or elliptical pipes have a larger surface area than circular pipes with the same cross-sectional area, and because they impede the flow of the fluid to be heated or cooled to a lesser extent, they receive less heat on the surface of the heat exchange pipe. There is an advantage that there are many pipes, and the heat exchange efficiency is improved compared to circular pipes.

In recent years, there has been a demand for a heat exchanger with excellent performance without increasing the installation area of the heat exchanger or by minimizing the occupied volume, in other words, for a compact and high-performance heat exchanger. It's increasing.

On the other hand, with the spread of refrigerated and frozen foods, many forced fan systems have been adopted to achieve rapid cooling. There are disadvantages such as being short,
A heat exchanger that can rapidly cool stored items while preventing them from drying out has been long-awaited.

(Prior Art) The following are known as double pipe type heat exchange pipes.

(1) A cooling medium is passed between the outside of the outer tube and the inside of the inner tube of the double tube, and the liquid to be cooled is circulated in the space between the two tubes, so that the cooling medium is circulated between the outer surface of the outer tube and the inner surface of the inner tube. Double cooling tube designed to exchange heat (Japanese Utility Model Publication No. 10711/1989) (2) Water is passed through the inner tube of the double tube, air is circulated outside the outer tube, and the space between the two tubes is A double-pipe heat exchange pipe that circulates the liquid to be cooled.

(Utility Model Publication No. 42-700, Utility Model Number 43-15886
(3) By providing a large number of fins protruding from the inner tube of the double tube and making the upper fins of the inner tube longer than the lower fins, the inner tube is eccentrically positioned downward from the center of the outer tube. A double-pipe heat exchange pipe that circulates air outside the outer tube, circulates water inside the inner tube, and circulates the liquid to be cooled in the space between the two tubes.

(Japanese Utility Model Publication No. 47-27230) All of the above-mentioned known double-tube heat exchange pipes circulate the liquid to be cooled through the space between the outer tube and the inner tube and use a cooling medium such as air and/or water. This is a method in which the water is distributed between the outside of the outer tube and the inside of the inner tube.

These known heat exchange pipes therefore have the disadvantage that a large amount of medium (for example air and/or water) must be passed through them in order to cool or heat a certain amount of fluid.

(Objective of the Invention) The present invention provides a method for exchanging heat using a double-pipe heat exchanger, in which the interference effect on the flow of fluid is as slight as possible and is supported on the surface of the heat exchange pipe. Using heat exchange pipes with increased heat capacity,
It is an object of the present invention to provide a heat exchange method that efficiently exchanges heat.

(Structure of the Invention) First, the structure of the heat exchange pipe used in the method of the invention will be described.

The heat exchange pipe used in this invention has a double wall structure by inserting and fixing a thin pipe whose cross section is the same or similar to that of the thick pipe into a thick pipe. Both ends of the pipe are closed to form a hollow cylindrical body, and when the cross section of the hollow cylindrical body is circular, it is fixed so that the center of the cross section does not coincide with the center of the cross section of the thick pipe, In addition, when the cross section of the hollow cylindrical body is not circular, the eccentric double wall is fixed so that the center of the cross section is on the long axis of the cross section of the thick pipe and does not coincide with the center of the cross section of the thick pipe. It's a pipe.

In this eccentric double wall pipe, when the cross section of the pipe is oval or oval, the ratio of the length of the major axis to the length of the minor axis is:
The thicker the pipe (that is, the flatter the cross-sectional shape), the larger the surface area compared to the volume of the pipe and the better the efficiency of heat exchange, but if the pipe is made too flat, the pipe may break. Since it becomes easy to bend and also makes it difficult to manufacture the pipe, an appropriate range should be selected in consideration of various circumstances.

As a general guideline for the appropriate range, it is preferable that the length of the major axis is about 1.5 to 3.5 times the length of the minor axis.

Within this range, a particularly suitable range is that the length of the major axis is about 2.0 to 2.5 times the length of the minor axis.

The thin pipe inside the heat exchange pipe used in this invention (hereinafter referred to as "inner pipe").

) has a cross-sectional shape similar to that of the outer thick pipe (hereinafter referred to as the "outer pipe").
It is written as

) has the same cross-sectional shape (however, the dimensions are different, so they are similar shapes).

), but it doesn't have to be an exact similar shape as long as it has a similar shape.

Preferably, the length of the inner tube is approximately equal to the length of the outer tube in the longitudinal direction.

This is because if the length of the inner tube is insufficient, the purpose of using the inner tube will not be fully achieved, and if the length of the inner tube is too long, it will be difficult to connect the outer tubes to each other, and the heat exchange pipes will be damaged. This is because it increases the flow resistance of the flowing heat medium and ultimately reduces the heat exchange efficiency.

Next, an operation method for exchanging heat according to the present invention using the above-mentioned heat exchange pipe will be explained.

In the heat exchange method of the present invention, a heating medium or a cooling medium is caused to flow through the gap formed between the outer tube and the inner tube (ie, the hollow cylindrical body) of the eccentric double-walled pipe.

The fluid to be heated or the fluid to be cooled flows outside the eccentric double-walled pipe.

However, when using an eccentric double-walled pipe, the wide side of the gap formed between the outer pipe and the inner pipe (i.e., the flow path for the heating medium or cooling medium) is directed toward the upstream direction of the fluid to be heated or cooled. There must be.

Utility Model Publication No. 6-10711, Utility Model Publication No. 42-700, Utility Model Number 43-15886, and Utility Model Number 47-
In the double cooling pipe described in Japanese Patent No. 27230, the fluid to be cooled flows through the gap formed between the outer pipe and the inner pipe, but in the present invention, the fluid to be heated or the fluid to be cooled flows through the gap formed between the outer pipe and the inner pipe. Since the fluid flows outside the outer tube,
In the present invention, the method of using heat exchange pipes is completely new.

Furthermore, in the heat exchange pipe used in the present invention, the inner tube is installed only inside the straight portion of the outer tube, so the present invention is also completely new in this respect.

Furthermore, in the heat exchange pipe used in the present invention, both ends of the inner tube are closed, so no fluid flows inside the inner tube.

In this respect as well, the novelty of the present invention is extremely remarkable.

(Examples) In order to further facilitate understanding of the present invention, embodiments of the present invention will be described below with reference to the drawings, but it is noted that the present invention is not limited only to the following examples. Needless to say.

FIG. 3 shows the relative position and fixed state of the inner tube and outer tube in an eccentric double-walled heat exchange pipe.

In the drawings, 4 indicates an outer tube, 5 indicates an inner tube, and 6 indicates a support piece for the inner tube.

In these embodiments, both the outer tube and the inner tube are circular or oval shaped.

Further, although the support piece 6 is formed in a plate shape, it does not necessarily have to be in a plate shape, and may be in the shape of a rod or a block as long as it functions to fix the position of the inner tube.

However, since the support piece 6 is installed in the heat medium passage, it is preferable that the support piece 6 has a shape that has as little resistance to fluid flow as possible.

In addition, Fig. 3 shows three support pieces 6 for a circular pipe shape and five support pieces 6 for an oval shape pipe, but if the inner pipe has the function of fixing the inner pipe in a predetermined position, the number of support pieces 6 can be reduced. It can be changed as appropriate.

The heating medium flows through the gap 1 formed by the outer tube and the inner tube in FIG. 3, and the fluid to be cooled or heated flows in the direction of the arrow in FIG.

FIG. 4 is an explanatory diagram of the connected state of the outer tube and the closed state of the end of the inner tube.

A lid 9 is welded 10 to both ends of the inner tube 5. At this time, the air inside the inner tube 5 is heated and expanded and is exhausted to some extent, so when the welding work is finished and the temperature returns to room temperature, the inner tube The hollow part 8 of the inner tube 5 is under negative pressure, so that the heat capacity of the entire inner tube 5 is smaller than that of a mere hollow pipe, and the efficiency of heat exchange is improved accordingly.

The heat medium M flows in the direction of the arrow.

FIG. 5 is a conceptual diagram of a heat exchanger suitable for use in the heat exchange method of the present invention, in which 3 is a heat exchange pipe;
3' is the cross section of the heat exchange pipe.

FIG. 6 is a conceptual diagram when the heat exchange method of the present invention is applied to a radiator of an automobile, and if the rotation direction of the fan motor 11 is changed depending on the mounting position of the radiator, air is blown out (FIG. 6a) or sucked out. Since the wind (Figure 6b)
The eccentric positions of the outer tube and the inner tube are reversed between a and b, and the cooling air flows in the direction of the arrow to cool the hot water W.

(Operations and Effects of the Invention) In the present invention, a thin inner tube with both ends closed is inserted off-center into an outer tube that is thicker than a single-ply pipe, and a heat exchange pipe is also used. Since the method is also limited to special cases, it has the following effects.

(b) If the amount of heat medium in the eccentric double pipe heat exchange pipe is approximately the same as that in the single pipe method, the effective heat exchange surface area can be obtained without increasing the overall size of the heat exchanger. increases, heat exchange efficiency increases, and power consumption decreases.

(b) Since the center of the inner tube is shifted from the center of the outer tube,
By applying the heat exchange fluid to the side of the heat exchange pipe where the amount of heat medium is large, heat exchange efficiency is increased and power consumption is reduced.

(c) If adopted in a general refrigerator (refrigeration temperature 3°C to 8°C), the number of fins can be reduced because the heat exchange efficiency is high.

Therefore, more of the water droplets adhering to the fins connect with each other and fall before they start freezing, reducing adhesion and further promoting heat exchange.

Compared to the single-vibration method, the cooling time to the same temperature is 1/2 to 2/3.

In the case of general refrigerators (freezing temperature -15°C to -25°C), it is common to defrost with an electric heater, so the power consumption is 3 to 4 times the power consumption of the compressor. If defrosting is performed using the hot gas method using the double pipe method of this invention, an electric heater is not required.

(b) Since the inner tube with both ends closed has a negative pressure inside, the heat capacity of the inner tube becomes smaller and the heat exchange efficiency is significantly improved.

Furthermore, if a hot gas method is used for defrosting, the heat of the hot gas will not be wasted by the tape, and the defrosting time will be shortened due to the high thermal efficiency.

(e) Since the heat exchange capacity is improved, the spacing between the fins can be wider than in the case of a single-vibration system, which makes it difficult for dust to adhere to the fins, preventing a decrease in heat exchange capacity, and reducing power consumption. Contribute to reduction.

(c) The heat exchange method of the present invention can be used in both a condenser and an evaporator of a heat exchanger.

The evaporator can be used for both heating and cooling; hot water or steam can be passed through it for heating, and high-pressure Freon gas can be passed through it for cooling.

[Brief explanation of drawings]

Fig. 1 is a schematic front view of a conventional heat exchanger, Fig. 2 is a sectional view taken along line A-A in Fig. 1, Figs. 3 to 6 show embodiments of the present invention, and Fig. 3 is an eccentric Sectional view of wall heat exchange pipe, No. 4
The figure is an explanatory diagram showing the connection of the outer tube and the closed state of the inner tube end, FIG. 5 is a schematic diagram of a heat exchanger equipped with an eccentric double-wall heat exchange pipe, and FIGS. 6 a and b are FIG. 2 is an explanatory diagram of the structure, blowing air, and suction air when an eccentric double-wall heat exchange pipe is used for a radiator of an automobile. The symbols in the drawings represent the following, respectively. DESCRIPTION OF SYMBOLS 1... Frame, 2... Fin, 3... Heat exchange pipe, 3'... Same sectional view, 4... Outer tube, 5... Inner tube,
6... Support piece, 7... Gap, 8... Hollow part of inner tube, 9... Lid of inner tube, 10... Welded part, 11... Fan motor, M... Heat medium, W...hot water.

Claims (1)

[Claims] 1 A thin pipe with both ends closed is fixed and enclosed inside a thick pipe, and if the pipe is circular, the center of the thin pipe is offset from the center of the thick pipe, and if the pipe is oval or oval, the center of the thin pipe is offset from the center of the thick pipe. The center of the pipe is on the long axis of the thick pipe, and the heat medium is circulated in the gap between the inner and outer tubes of a heat exchanger using eccentric double pipes. A forced heat exchange method characterized by forcibly bringing a fluid to be heat exchanged into fluid contact with the outer surface of the outer tube on the side with a wider distance from the outer tube.