JPH0631692B2 - Heat exchanger - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a heat exchanger, and more particularly to a heat exchanger suitable for being incorporated in a heater of a Stirling engine.

[Technical background of the invention and its problems]

Recently, as a part of energy saving, the Stirling engine has been reviewed and eager research has been conducted. There are various types of Stirling engines, for example,
Taking the two-piston type as an example, the regenerative heat exchangers are connected in a closed flow path configuration between the power cylinders with built-in power pistons, and the flow between one end of the regenerative heat exchanger and one power cylinder is The passage is heated by a heater, and the passage between the other end of the regenerative heat exchanger and the other power cylinder is cooled by a cooler. This institution
It has the characteristic that theoretical heat efficiency is high and that any heat source can be used.

By the way, the output of the Stirling engine is affected by the maximum space volume due to piston movement in the cylinder, temperature ratio, mechanical efficiency, etc., but is also affected by the dead space volume (dead space) in the heater, etc. The smaller the value, the more the output can be increased.
Therefore, the heat exchanger incorporated in the heater of the engine is desired to have a dead space as small as possible. On the other hand, on the other hand, the higher the heating temperature of the heater, the higher the efficiency. Therefore, it is also a necessary condition that the heat exchanger incorporated in the heater of this engine has a sufficiently large heat transfer area. Become.

For this reason, conventionally, as a heat exchanger incorporated in a heater of a Stirling engine, it has been proposed to use a large number of thin heat transfer tubes having an inner diameter of about 1 to 4 mm to form the heat exchanger. However, in the heat exchanger having such a configuration, since it is necessary to connect a large number of thin heat transfer tubes to the head of the cylinder, there are many welding spots, which not only makes the welding work very troublesome but also has many welding spots. Due to this, the working fluid easily leaks and the reliability of the device is lacking.

Therefore, in order to solve such a problem, Japanese Patent Laid-Open No. 58-58
As disclosed in Japanese Patent No. 167863, the heat transfer area is increased by using a large diameter heat transfer tube.
In addition, in order to suppress the increase of dead space caused by using a large diameter heat transfer tube, a core material is inserted in the heat transfer tube and the flow width (or thickness) in the same direction as the direction of heat transfer
Proposals have also been made for heat exchangers that reduce the heat dissipation. In the heat exchanger having such a structure, unlike the one using a thin heat transfer tube, the number of welding points can be significantly reduced. However, in order to further increase the heat transfer area, it is necessary to use a larger diameter heat transfer tube or to increase the number of heat transfer tubes, and it is necessary to increase the heat transfer area in a limited space. There was a limit.

Furthermore, what can be said in common to the above-mentioned two types of heat exchangers is how to prevent corrosion of the heat transfer tube due to the lubricating oil that has entered the working space through the gap between the cylinder and the piston. Is. That is, the heat transfer tube of the heat exchanger incorporated in the heater of the Stirling engine is usually heated to several hundred degrees Celsius. The lubricating oil that has entered the working space decomposes when heated to the above temperature, and the decomposed components accelerate corrosion of the heat transfer tubes. Therefore, it was necessary to solve the countermeasure against this corrosion.

[Object of the Invention]

The present invention has been made in view of such circumstances, and an object thereof is to simplify welding work, prevent leakage of working fluid, and increase a heat transfer area in a limited space. Another object of the present invention is to provide a heat exchanger that has a good corrosion resistance.

[Outline of Invention]

According to the present invention, the outer heat transfer tube whose one end is closed, the heat transfer core material inserted in the outer heat transfer tube, and the heat transfer core material inserted between the outer heat transfer tube and the outer heat transfer tube A return fluid passage is formed between the outer heat transfer tube and the heat transfer core member and extends from the other end side of the outer heat transfer tube toward the one end side, and then returns at the one end side and extends toward the other end side. An inner heat transfer tube to be formed, and the inner heat transfer tube and the outer heat transfer tube of the folded fluid passage formed integrally with the outer surface of the inner heat transfer tube at a height close to the inner surface of the outer heat transfer tube. A plurality of first ridges that divide the portion located between them into a plurality in the circumferential direction,
Of the inner heat transfer tube of the folded fluid passage and the inner heat transfer tube of the folded fluid passage, which is provided integrally with either the inner surface of the inner heat transfer tube or the outer surface of the heat transfer core at a height close to the other. A plurality of second ridges that divide the portion located between them into a plurality in the circumferential direction, and plating provided on the inner surface of the outer heat transfer tube, the inner and outer surfaces of the inner heat transfer tube, and the outer surface of the heat transfer core material, respectively. A heat exchanger with layers is provided.

〔The invention's effect〕

According to the present invention, when the outer surface of the outer heat transfer tube is brought into contact with the high temperature fluid and the low temperature fluid is caused to flow through the above-mentioned folded fluid passage, the heat of the high temperature fluid is transferred from the outer surface of the outer heat transfer tube to the outer heat transfer tube.
Inner surface of outer heat transfer tube-first path made of low temperature fluid, and outer surface of outer heat transfer tube-outer heat transfer tube-inner surface of outer heat transfer tube-first
-Inner heat transfer tube-Inner and outer surfaces of inner heat transfer tube-Second path consisting of low temperature fluid and outer surface of outer heat transfer tube-Outer heat transfer tube-Inner surface of outer heat transfer tube-First projection-Inner transfer The heat is transmitted to the low temperature fluid through three paths including the heat pipe, the second ridge, the heat transfer core, the outer surface of the heat transfer core, and the third path including the low temperature fluid. Therefore, if the inner diameters of the outer heat transfer tubes are the same, the heat transfer area can be more than doubled compared to the case where the core material is inserted and the folded flow paths are simply formed in the heat transfer tubes. Therefore, the heat exchange efficiency can be improved while the overall size is reduced. Further, by selecting the heights of the first and second protrusions, the width (or thickness) in the same direction as the heat transmission direction in the folded fluid passage can be made sufficiently small without reducing the heat transfer area so much. Therefore, it is possible to provide a structure having a small space that can be a dead space. In addition, the inner surface of the outer heat transfer tube. Since a plating layer is provided on the inner and outer surfaces of the inner heat transfer tube and the outer surface of the heat transfer core material, even if a corrosive component enters the folded fluid passage by selecting the material of this plating layer, This makes it possible to prevent the constituent members from being corroded. In this way, the heat transfer area can be wide enough, the space that can become a dead space can be narrowed, and the corrosion resistance can be improved. Therefore, it is possible to obtain a heat exchanger suitable for being incorporated in a heater of a Stirling engine or the like. You can

Example of Invention

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical sectional view of a two-piston type Stirling engine in which a heat exchanger according to an embodiment of the present invention is incorporated in a heater.

That is, the Stirling engine is roughly divided into a power cylinder 1 (hereinafter referred to as an expansion cylinder) used for expanding a working fluid, and a power piston 2 slidably mounted in the expansion cylinder 1. (Hereinafter referred to as an expansion piston), a power cylinder 3 used for compressing a working fluid (hereinafter referred to as a compression cylinder), and a power piston 4 slidably mounted in the compression cylinder 3. (Hereinafter referred to as the compression piston), the heater 5, the regenerative heat exchanger 6 and the cooler 7 provided between the expansion cylinder 1 and the compression cylinder 3, the expansion piston 2 and the compression piston 4, respectively, the connecting rod 8, 9, and an output shaft 12 connected via crankshafts 10 and 11.

The heater 5 has a combustion chamber 15 formed by disposing a heat insulating material 14 so as to surround the head 13 of the expansion cylinder 1.
And a plurality of heat exchangers 16 arranged in the combustion chamber 15.
And a burner 17 arranged so as to face the combustion chamber 15,
It is composed of a preheater 18 that preheats air required for combustion with combustion gas.

Each of the heat exchangers 16 has a rod-shaped outer shape, and one end of each fluid passage communicates with the top of the expansion cylinder 1 and the other end communicates with a manifold 19 formed in the head 13. And are arranged so as to form a funnel as a whole. Each heat exchanger 16 is specifically configured as shown in FIGS. 2 and 3. That is, the heat exchanger 16 is roughly divided into an outer heat transfer tube 21 which is closed at one end and opened at the other end, and an inner heat transfer tube which is concentrically inserted into the outer heat transfer tube 21 and whose both ends are open. 22 and a heat transfer core member 23 concentrically inserted in the inner heat transfer tube 22. The outer heat transfer tube 21 is
It is made of a material with good thermal conductivity and high heat resistance and pressure resistance. Its inner surface is nickel-plated, and its outer peripheral surface is on the tip side, that is, the closed side. Is provided with a plurality of fins 24. The inner heat transfer tube 22 has a better thermal conductivity than the outer heat transfer tube 21, and is made of, for example, copper so as to be longer than the outer heat transfer tube 21 by a predetermined length, and one end portion 25 is a predetermined distance from the closing wall of the outer heat transfer tube 21. The other end 26 is inserted into the outer heat transfer tube 21 in such a manner that the other end 26 projects from the outer heat transfer tube 21. The outer surface of the inner heat transfer tube 22 has a third
As shown in the figure, the protrusions 27 extending in the axial direction are integrally formed at four locations in the circumferential direction. The ridges 27 are formed at such a height that they are in close contact with the inner surface of the outer heat transfer tube 21 when the inner heat transfer tube 22 is inserted into the outer heat transfer tube 21 as shown in FIG. The inner and outer surfaces of the inner heat transfer tube 22 are nickel-plated. Heat transfer core material 2
3 is made of copper or the like and is slightly longer than the inner heat transfer tube 22. This heat transfer core 23 has one end 2
8 is separated from the closed wall of the outer heat transfer tube 21 by a predetermined distance and protrudes from the end 25 of the inner heat transfer tube 22 by a predetermined distance, and the other end 29 is flush with the end 26 of the inner heat transfer tube 22, and will be described later. The protruding ridge 30 is inserted into the inner heat transfer tube 22 in a state of overlapping with the position where the protruding ridge 27 is provided. As shown in FIG. 3, on the outer surface of the heat transfer core member 23, there are integrally formed ridges 30 extending axially at four circumferential positions. This ridge 30 is
When the heat transfer core material 23 is inserted into the inner heat transfer tube 22 as shown in FIG. 2, the heat transfer core material 23 is formed so as to come into close contact with the inner surface of the inner heat transfer tube 22. The outer surface of the heat transfer core material 23 is nickel-plated.

Each heat exchanger 16 constructed as described above is welded to the head 13 so that the end 26 of the inner heat transfer tube 22 communicates with the top of the expansion cylinder 1 as shown in FIG. The open end 31 of the heat tube 21 is welded to the head 13 so that the open end 31 communicates with the manifold 19.

The manifold 19 is then connected to the regenerative heat exchanger 6 via the connecting pipe 32, which is connected to the top of the compression cylinder 3 via the cooler 7 constituted by the heat exchanger. ing. And the space surrounded by the expansion cylinder 1 and the expansion cylinder 2, each heat exchanger 16, the manifold 19, the connecting pipe 32, the regenerative heat exchanger 6, the cooler 7,
He as a working fluid is enclosed in a closed space formed by a space surrounded by the compression cylinder 3 and the compression piston 4.

In FIG. 1, 33 is a crank chamber in which lubricating oil is stored to a predetermined level, 34 and 35 are linear bearings, and 36 is a pipe for guiding the refrigerant of the cooler 7.

With such a configuration, when the output shaft 12 is temporarily rotated by an external power source while the burner 17 is ignited and the refrigerant is flowing through the pipe 36, the crankshaft 10 , 11, the expansion piston 2 and the compression piston 4, which are connected via connecting rods 8 and 9, reciprocate with a certain phase difference. When the expansion piston 2 moves to the compression stroke due to this reciprocal movement, He in the expansion cylinder 1 is transferred to each heat exchanger 16, manifold 19, connection pipe 3
2, compression cylinder 3 via regenerative heat exchanger 6 and cooler 7
Most of He flows into the compression cylinder 3 when the expansion piston 2 reaches the top dead center. At this time, He is deprived of the heat retained by the regenerative heat exchanger 6 while passing through the regenerative heat exchanger 6, and is further cooled while passing through the cooler 7. When the compression piston 4 starts moving from the bottom dead center to the top dead center with the rotation of the output shaft 12, the low temperature He in the compression cylinder 3 is compressed,
It flows into the expansion cylinder 1 by a route opposite to the conventional one.
At this time, He absorbs heat while passing through the regeneration heat exchanger 6 and is heated to a high temperature, and is further heated while passing through each heat exchanger 16. The high temperature He flowing into the expansion cylinder 1 expands and pushes down the expansion piston 2. After that, the above-described operation is repeated, the output shaft 12 continues to rotate even when the external power source is cut off, and the function as the Stirling engine is exhibited.

By the way, He moves between the expansion cylinder 1 and the compression cylinder 3 as described above, and when this He passes through each heat exchanger 16, it passes through the following paths.
That is, taking the case where He flows from the manifold 19 toward the expansion cylinder 1 as an example, the open end 31 of the outer heat transfer tube 21 of each heat exchanger 16 communicates with the manifold 19,
Since the end portion 26 of the inner heat transfer tube 22 communicates with the top of the expansion cylinder 1, He is located between the outer heat transfer tube 21 and the inner heat transfer tube 22 as indicated by the solid arrow in FIG. In addition, due to the presence of the ridges 27, the passages 41 formed in four sections in the circumferential direction flow toward the closed wall side of the outer heat transfer tube 21 along the axis, are folded back near the closed wall, and then the inner heat transfer tube 2
After flowing along the axial center line in the passage 42 divided into four in the circumferential direction between the heat transfer core member 23 and the heat transfer core member 23, it flows to the expansion cylinder 1. Each heat exchanger 16
Is located in the combustion chamber 15. Therefore, when He flows through the heat exchanger 16 through the above path, the He is heated, but in this case, since each heat exchanger 16 is configured as described above, it can be efficiently heated. . That is, the heat generated in the combustion chamber 15 includes the first path formed by the inner surface of the outer heat transfer tube 21 to He, the outer surface of the outer heat transfer tube 21 to the inner surface of the outer heat transfer tube 21, the ridge 27, and the inner heat transfer tube 22. Outer surface to second path consisting of He and inner surface of outer heat transfer tube 21 to outer heat transfer tube 21-projection ridge 27-inner heat transfer tube 22-inner surface of inner heat transfer tube 22-projection ridge 30-heat transfer core material 23-transfer Hot core material 23
The outer surface of the He ~ He in three paths with the third path consisting of He
Be transmitted to. Therefore, the heat transfer area can be expanded several times as compared with the case where a heat transfer tube having the same inner diameter as the outer heat transfer tube 21 is used and a core material is inserted in the heat transfer tube to form a simple folded passage. Therefore, the exchange efficiency of the heat exchanger 16 can be improved and the overall size can be reduced. In addition, ridge 2
The height Y of the passages 41 and 42 can be reduced in the same direction as the heat transfer area by reducing the height of 7, 30 and the heat transfer area is hardly reduced. As a result, it is most preferable for the Stirling engine. A heat exchanger, that is, a heat exchanger having a small dead space can be realized. Also, since the inner surface of the outer heat transfer tube 21, the inner and outer surfaces of the inner heat transfer tube 22 and the outer surface of the heat transfer core material 23 are nickel-plated, even if lubricating oil enters during operation, Also, it is possible to prevent the constituent material of the heat exchanger from being corroded due to the presence of the plating layer, and in the end, it is possible to exert the above-mentioned effects.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified. That is, although the ridge 30 is provided on the heat transfer core member 23 in the above embodiment, it may be provided integrally on the inner surface of the inner heat transfer tube 22. Further, the plating layer is not limited to the nickel plating layer, and may be selected in relation to the lubricating oil used. Also,
The use of the heat exchanger according to the present invention is not limited to the Stirling engine, and it is needless to say that it can be used for heat exchange between various fluids. In addition, various modifications can be made without departing from the scope of the present invention.

[Brief description of drawings]

1 is a longitudinal sectional view of a Stirling engine incorporating a heat exchanger according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a heat exchanger incorporated in a heater of the engine, and FIG. FIG. 3 is a view of the heat exchanger taken along line XX in FIG. 2 and viewed in the direction of the arrow. 1 ... Expansion cylinder, 2 ... Expansion piston, 3 ... Compression cylinder, 4 ... Compression piston, 5 ... Heater, 6 ... Regenerative heat exchanger, 7 ... Cooler, 16 ... Heat exchanger, 21 ... Outer heat transfer tube,
22 ... Inner heat transfer tube, 23 ... Heat transfer core material, 24 ... Fins, 2
7, 30 ... Ridges, 41, 42 ... Passages forming folded fluid passages.

Front page continuation (72) Inventor Tsutomu Sakuma 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Stock company, Toshiba Home Appliances Technology Laboratory (72) Inventor Shigemi Nagatomo 8 Shinsita-cho, Isogo-ku, Yokohama, Kanagawa Toshiba Home Appliances Technology Laboratory

Claims (3)

[Claims] 1. An outer heat transfer tube whose one end is closed, a heat transfer core member inserted in the outer heat transfer tube, and the outer side inserted between the heat transfer core member and the outer heat transfer tube. A return fluid passage is formed between the heat transfer tube and the heat transfer core member, extending from the other end side of the outer heat transfer tube toward the one end side, and then folded back at the one end side to extend toward the other end side. An inner heat transfer tube,
A portion formed integrally with the outer surface of the inner heat transfer tube and at a height close to the inner surface of the outer heat transfer tube and located between the inner heat transfer tube and the outer heat transfer tube of the folded fluid passage in the circumferential direction. A plurality of first ridges that are divided into a plurality of sections, and the folding fluid provided integrally with either the inner surface of the inner heat transfer tube or the outer surface of the heat transfer core at a height close to the other. A plurality of second ridges for partitioning a portion of the passage located between the inner heat transfer tube and the heat transfer core material into a plurality in the circumferential direction, an inner surface of the outer heat transfer tube, and inner and outer surfaces of the inner heat transfer tube And a plating layer provided on the outer surface of the heat transfer core material, respectively. 2. The heat exchanger according to claim 1, wherein the inner heat transfer tube and the heat transfer core material are made of a material having a higher thermal conductivity than that of the outer heat transfer tube. 3. The heat exchanger according to claim 1, wherein the plating layer is a nickel plating layer.