JP2001280864A - Heat exchanger and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger for combustible fluid in which mixing of a heating side fluid and a heated side fluid is suppressed. SOLUTION: In a multi-tube tubular heat exchanger, heat transfer tubes are formed in double tube structure and inert gas flows through the gap channel between the inner and outer tubes. The outer tubes are coupled each other, on the surface thereof, through a thermally conductive member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger suitable for safely exchanging heat for a fluid such as a flammable substance or a poison that is not desired to leak from a flow path.

[0002]

2. Description of the Related Art As a prior art, a heat exchanger for exchanging heat between flammable liquefied natural gas (hereinafter referred to as LNG) and compressed air is disclosed in Japanese Patent Application Laid-Open No. Hei 10-47080. . In this prior art, in order to avoid an unexpected event due to leakage, it is proposed that heat is exchanged through a nonflammable intermediate refrigerant. Also, JP-A-9-279132
In Japanese Patent Application Laid-Open Publication No. H11-115, studies are made on nonflammable refrigerants for exchanging heat with LNG.

[0003]

In the above two prior arts, a nonflammable intermediate refrigerant is assumed for heat exchange with flammable LNG. However, a flammable substance such as LNG or a toxic substance is used as a heat exchange medium. For heat exchangers that use such heat exchangers, there is a risk that the leakage of the medium or the mixing of the fluid on the heated side and the fluid on the heated side may lead to events such as combustion, explosion, and contamination. It was desired to be considered.

[0004] The present invention has been made in view of the above points, and an object of the present invention is to provide a heat exchanger that suppresses mixing of a heat exchange medium.

[0005]

In order to achieve the above object, a heat exchanger according to the present invention comprises a heat transfer tube group including a plurality of heat transfer tubes, a body accommodating the heat transfer tube group, and a heat transfer tube. A heat exchanger comprising: a tube plate provided at each end of the heat tube group to hold the ends of the heat transfer tube group; and a baffle plate provided to form a flow path in the body internal space. In the above, the heat transfer tube is constituted by an inner tube and an outer tube, and a part of an outer surface of the inner tube and a part of an outer surface of the outer tube are directly or thermally conductive members. Are formed so as to be in contact with each other via

[0006]

FIG. 4 shows an embodiment of a gas turbine power generation system utilizing the LNG cold energy, provided with a heat exchanger according to the present invention. The main components of this embodiment include:
A compressor 51 for compressing air to a high pressure;
A combustor 5 for burning fuel such as NG; a gas turbine 7 driven by expansion of a high-temperature, high-pressure combustion gas; a generator 8 arranged on the same axis as the gas turbine 7;
The regenerative heat exchanger 9 recovers the heat of the exhaust gas. Further, in the present embodiment, a heat exchanger 70 for exchanging heat between the LNG supplied from the LNG storage tank 43 via the pipe 40 and the intake air of the compressor 51 is provided.

FIG. 1 is a longitudinal sectional view of a heat exchanger according to an embodiment of the present invention. FIG. 1 is a view showing a detailed structure of a heat exchanger 70 shown in FIG. 4, and FIG. It is shown. In this embodiment, as shown in FIG. 1 and FIG.
And the outer tube 24 are connected to each other by plate-like fins 22 made of an aluminum alloy having a surface perpendicular to the tube axis. Inner tube 2 of these double tubes
3 communicates with the header 26, and the nozzle 12
It is connected to the. The flow path formed in the gap between the outer tube 24 and the inner tube 23 communicates with the nozzle 13 via a space partitioned by the tube sheet 27. A steel baffle plate 31 is arranged on the surface of the outer tube 24 and mixed with the plate-like fins 22. The baffle plate has a nozzle 11
Has an opening to form a flow path in which the flow of air flowing in the body 30 via the plate-like fins flows along the surface of the plate-shaped fin in a meandering manner inside the body 30.

In this embodiment shown in FIG. 1, the air introduced to the heat exchanger 70 as the intake air of the compressor is
In the process of meandering the inside of the body 30 in which the double pipe 33 is installed from a, the heat exchanges with the cold heat of the LNG flowing through the inner pipe 23 of the double pipe 33, and is then supplied to the compressor from the nozzle 11b.
In addition, LNG guided from the nozzle 12a to the header 26a
Is heated by heat exchange with air through the inner tube 23 and then supplied to the outside via the header 26b and the nozzle 12b. Further, the inert gas guided from the nozzle 13a passes through a gap flow path formed between the inner pipe 23 and the outer pipe 24, and is then guided to the outside from the nozzle 13b.

FIG. 5 shows the configuration of the safety system of this heat exchanger.
Shown in A nitrogen gas supply device 76 that supplies nitrogen gas as an inert gas to the heat exchanger 70 is connected to a nozzle 13a of the heat exchanger 70 via a gas pressure control valve 75. The nozzle 13 b has a pressure gauge 81 and a gas detector 8.
2 is installed, and in the unlikely event that a failure occurs in the flow path of natural gas (hereinafter referred to as NG), NG leaks into the flow path of the inert gas, that is, the gap flow path between the inner pipe and the outer pipe. In this case, the shut-off valves 85a to 85d are designed to be automatically closed by a command from the control circuit 83. In addition, a rupture disk 86 that opens automatically when the pressure rises above a certain limit is installed in the flow path of the inert gas, and the other end of the rupture disk 86 is connected to a flare stack 88 by a pipe 87. I have.

[0010] The method of manufacturing this heat exchanger is first described in FIG.
As shown in (A), an inner tube 23 whose outer diameter is smaller than the minimum inner diameter of the outer tube 24 is inserted into a copper outer tube 24 having a groove formed on the inner surface. The material of the inner tube was stainless steel in consideration of weldability to the header. Next, an inward mechanical force is applied from the outer surface of the outer tube 24 by a rolling mill or the like to reduce the outer diameter of the outer tube 24. As a result, the outer surface of the inner tube 23 and the protrusion on the inner surface of the outer tube 24 come into mechanical and thermal contact with each other, and the air and LNG are separated between the inside of the inner tube 23 and the outside of the outer tube 24. Heat exchange becomes possible. Further, a gap is formed in a region sandwiched between the inner tube 23 and the outer tube 24, so that an inert gas or the like can flow.

Further, a required number of the double tubes 33 are arranged, and plate-like fins 22 that have been punched in advance are sequentially pressed into the outer surface of the double tube from the tube end. The hole shape of the plate-like fins 22 is cut to make it easier to press-fit.
It is desirable to have elasticity. At a necessary interval, a baffle plate 31 that has been punched in advance is also inserted. The baffle plate is drilled in the same way, but the baffle plate is
The baffle plate is provided to restrict the direction of the flow in the body and does not necessarily require a heat transfer function. Therefore, elastic holes or packing such as Teflon may be provided in the hole of the baffle plate. In that case, the airtightness can be improved.

In this example, the required number of double tubes 33 are fixed, and the plate-like fins 22 and the baffle plate 31 are sequentially press-fitted from the end of the tube.
The double tubes 33 may be inserted one after another by aligning and fixing a necessary number of the tubes 1. When the number of double tubes 33 is small, the former method has the advantage that the force required for press-fitting is small, and when the number of double tubes 33 is large, the latter method has the advantage that it can be press-fitted with smaller force.

Next, the tube sheet 27 is attached to the outer surface of the outer tube 24 made of copper. The joining method is brazing or welding in an inert gas. Next, the header 26 is attached to the end of the stainless steel inner tube 23 by welding. These are housed in the body 30, and the nozzles 11, 12, 13,
Attach etc. Although not shown, it is desirable that bellows or the like be attached to the body 30 to reduce stress due to thermal expansion.

The operation of this embodiment will be described with reference to FIGS. An air blower 8 is provided in the nozzle 11a of the heat exchanger 70.
At 0, suction air at normal temperature and about atmospheric pressure is supplied as a heating-side fluid, and LNG at a temperature of about -150 ° C. and a pressure of about 5 MPa is supplied to the nozzle 12a as a heated-side fluid. The intake air flowing in from the nozzle 11a divides the space in the body 30 partitioned by the baffle plate 31 into the plate-like fins 2.
In parallel with the surface of No. 2, the heat flows by the forced convection with the fins and flows toward the nozzle 11b. Due to the effect of the baffle plate 31, the flow is rectified in parallel to the members of the plate-like fins 22, and the intake air moves meandering in the body 30, so that the movement distance becomes longer and the temperature efficiency of heat exchange can be increased. I can do it. Further, since the flow path is restricted, there is an effect that the flow velocity increases and the heat transfer coefficient also increases. Furthermore, since the surface heat transfer area of the plate-like fin is very large and the fin efficiency is high because it is made of an aluminum alloy, it is convenient for heat exchange of low-density intake air.

The LNG at -150 ° C. supplied from the nozzle 12a branches from the header 26a into the inner pipe 23 of the double pipe 33 and flows therein. Since this fluid has a high density and a high thermal conductivity, the heat transfer coefficient in the tube is high. The entire heat transfer path includes forced convection heat transfer between the air and the plate-like fins 22, heat conduction inside the plate-like fins, contact heat transfer between the plate-like fins and the outer tube 24, heat conduction in the tube material of the outer tube, There are contact heat transfer between the protrusion on the inner wall surface of the outer tube and the outer wall surface of the inner tube 23, heat conduction in the tube material of the inner tube, and forced convection heat transfer between the inner surface of the inner tube and the LNG. The greatest thermal resistance in this path is forced convection heat transfer between low-density air and plate-like fins. However, as in the present embodiment, plate-like fins are arranged outside the outer tube to reduce the heat transfer coefficient. Means for increasing the heat transfer area of a portion having a small diameter can improve the overall heat transmission coefficient.

When the intake air flows out of the nozzle 11b by the action of the heat exchange, it is cooled to about -130 ° C., and NG is passed through the header 26b to the nozzle 12b.
As it flows out, it is heated to -10 ° C.

The intake air cooled to -130 ° C. is compressed to about 15 atm by the action of the compressor 51. At this time, since the air that has been cooled and has a high density is compressed, the air can be compressed with less than half the power as compared with the case where the normal temperature air is compressed to about 15 atm. Although the temperature of the compressed air rises to about 70 ° C., the regenerated heat exchanger 9
Heat exchange with the gas turbine exhaust gas
The fuel is heated to about ° C. and burned in a combustor 5 together with a fuel 50 such as LNG. In the gas turbine 7, the generator 8 is driven by the expansion force of the high-temperature and high-pressure combustion gas to generate electric power. The exhaust gas of the gas turbine 7 is recovered by the regenerative heat exchanger 9 and discharged from the stack 55 to the atmosphere. The feature of this system is that by utilizing the cold energy possessed by LNG, usually 50 to 6
The power of the air compressor that consumes 0% can be greatly reduced, and as a result, the power generation output can be greatly increased.

Next, with reference to FIGS. 1 and 5, an operation in the case where a leak occurs in the heat exchanger 70 in this embodiment will be described. In this embodiment, as described above, air at normal temperature and about atmospheric pressure flows through the air flow path 18. In the natural gas flow path 19 (the internal flow path of the inner pipe 23),
Pressurized LNG is supplied and heated by heat exchange with air to become NG. The nitrogen gas flow path 20 (the inner pipe 23)
The nitrogen gas supply device 76
Is supplied with nitrogen gas. With the operation of the heat exchanger 70, the supplied nitrogen gas is also cooled and the volume is reduced, so that the nitrogen gas pressure in the nitrogen gas flow path 20 is reduced to about atmospheric pressure by automatic control of the gas pressure control valve 75. Control so that When the operation is stopped and the temperature of the entire heat exchanger 70 rises, the pressure of the nitrogen gas flow path 20 rises. Therefore, the nitrogen gas discharge valve 77 is operated to reduce the pressure to about atmospheric pressure. Control.

Here, it is assumed that any part of the natural gas passage 19 through which NG flows is damaged. As shown in FIG. 1, the natural gas flow path 19 is
~ Header 26a ~ inner tube 23 ~ header 26b ~ nozzle 12
This is the path b. The outer surface of this path is the nitrogen gas flow path 20, that is, the space covered by the nozzle 13a to the tube sheet 27b, the body 30, and the lid 32b to the space covered by the outer tube 24 to the tube sheet 27a, the body 30, and the lid 32a. To the nozzle 13b. Therefore, if any of the natural gas passages 19 is damaged, NG having a relatively high pressure inevitably flows out to the nitrogen gas passage 20. Since the air as the heating-side fluid flows through the air flow path 18, that is, the path from the nozzle 11a to the body 30 to the nozzle 11b, even if such an event occurs, the NG may not mix with the combustion-supporting air. No safety is ensured.

As shown in FIG. 5, a pressure gauge 81 and a gas detector 82 are installed in the nitrogen gas flow path 20. By detecting a change in pressure and a change in gas concentration, a control circuit 83 is controlled. The shutoff valves 85a to 85d are closed by the command. Further, when the pressure of the nitrogen gas flow path 20 rises above a set limit, the rupture disk 86 automatically ruptures and opens, and the NG flare through the pipe 87 while mixing with the inert gas nitrogen. Led to the stack 88,
Unburned gas is safely discharged outside the system while burning. These events correspond to the shutoff valves 85a and 85b of the heat exchanger 70.
As soon as all of the NG existing inside the is released, the process ends promptly.

In the present embodiment, when forming the double pipe, an outer pipe whose inner surface is grooved or protruded is used to obtain a double pipe as shown in FIG. 3 (A). An inner tube having grooves or protrusions may be used, in which case it has a double tube shape as shown in FIG. If the processing is not easy, such as when the material of the inner tube 23 is stainless steel, the method of FIG. 3A is advantageous. It is relatively easy to make large irregularities on the outside of the pipe by machining, etc.
When it is desired to increase the area of the annular flow path through which the inert gas flows, the method shown in FIG. 3B is advantageous.

Further, as shown in FIG.
3 and the inner surface of the outer tube 24 may be grooved or protruded. The advantage in that case is that a large flow area for the inert gas can be used, but the production cost is high.

As shown in FIG. 3D, the heat conductive wire 35 is connected to the inner tube 2 without forming grooves or protrusions.
The double pipe may be formed after being inserted between 3 and the outer pipe 24. In this case, there is an advantage that the groove processing or the projection processing is not required, but a means for holding a large number of wires 35 at appropriate positions during the processing is required.

In addition, as a method of assembling the double tube 33, in the above-described embodiment, a method of reducing the diameter by applying a mechanical force to the outer tube 24 from the outside has been exemplified, but another assembling method will be described below. I do.

First, the necessary number of plate-like fins 22 made of aluminum alloy, which have been pre-drilled, are aligned so that the positions of the holes are aligned. The hole shape of the plate-like fin 22 is
The edge portion is folded into a collar shape so that the minimum inner diameter of the hole is slightly larger than the outer diameter of the outer tube 24.
At a necessary interval, a baffle plate 31 that has been punched in advance is also inserted. The hole of the baffle plate may have the same color shape, but similarly to the above-described embodiment, elastic rubber or packing such as Teflon may be provided. In that case, the airtightness can be improved.

The outer tube 24 made of copper and having a groove formed on the inner surface is formed in the aligned portion of the hole of the fin and the baffle plate.
Insert At the time of insertion, there is a slight gap between the outer tube 24 and the hole of the fin.
And expand the outside diameter of the tube. Alternatively, a temporary pipe may be connected to the end of the outer pipe 24 and expanded by applying a fluid force such as water pressure. Since the copper outer tube 24 is rich in extensibility, it can be expanded relatively easily, and the plate-like fin 22 and the outer tube 24 are mechanically and thermally joined. At this time, tube sheet 2
If the tubes 7a and 27b are also inserted in advance, the tube sheet and the outer tube 24 can be joined by expanding the tube. If there is a problem with the strength in the joining by expansion, joining of the tube sheet and the outer tube is performed by a usual method such as brazing or welding.

Next, a copper inner tube 23 whose outer diameter is smaller than the minimum inner diameter of the outer tube 24 is inserted into each of the outer tubes 24. Further, the inner tube 23 is expanded by applying a mandrel or water pressure in the same manner, and the projection on the inner surface of the outer tube 24 and the outer surface of the inner tube 23 are mechanically and thermally joined. At this time, if the tube sheet portions in the headers 26a and 26b are also inserted in advance, the header and the outer tube 24 can be joined by expanding the tube. However, when there is a problem in strength in the joining by pipe expansion, joining is performed by a normal method such as brazing or welding. These are housed in the body 30 and the nozzles 11, 12, 13,
Attach etc. In addition, similarly to the above, the trunk 30 includes
It is desirable to attach bellows or the like to reduce stress due to thermal expansion.

The advantage of this assembling method is that, unlike the first embodiment, no special mechanical device such as reducing the diameter of the outer tube or press-fitting the double tube is required.

In the example described above, the outer tubes 24 are sequentially inserted after the necessary number of plate-like fins 22 and baffle plates 31 are aligned so that the positions of the holes are aligned. The tube 24 may be fixed, and the plate-like fin 22 and the baffle plate 31 may be sequentially inserted into the tube end. As in the case of the previous embodiment, an advantageous method can be selected in terms of the frictional force generated during insertion.

In this embodiment, when forming a double pipe, an outer pipe having an inner surface with groove processing or projection processing is used to obtain a double pipe as shown in FIG. 3 (A). As described in the example, the case where the double tube shown in FIG. 3B, FIG. 3C, or FIG. It is needless to say that each is the same as the above-mentioned embodiment.

The embodiment of the method for manufacturing a heat exchanger according to one embodiment of the present invention and the gas turbine power generation system utilizing an LNG cold heat provided with a heat exchanger have been described above. The present invention is also applicable to all systems utilizing LNG cryogenic heat, such as an LNG cryogenic liquid air production system.

According to the heat exchanger of the present embodiment, the heat transfer tube having the double tube structure is formed, and the inert gas is caused to flow through the gap flow path between the outer tube and the inner tube of the double tube, so that the flammability can be improved. In the case of heat exchange of fluids that are not desired to leak, such as substances and poisons, it is possible to suppress the direct mixing of the heating fluid and the heated fluid even if the heat transfer tube leaks. It becomes possible.

Further, by connecting the outer surface of the outer tube of the double heat transfer tube to the outer surfaces of the other outer tubes by a heat conductive member, the heat transfer area outside the tube is increased, and the flow rate is increased. And the heat transfer coefficient can be increased, and the efficiency of the entire heat exchanger can be increased.

Further, on one side of the body, a first tube sheet and a second tube sheet are provided, and the first tube sheet is connected to a tube end of the outer tube of the double heat transfer tube, Since the second tube sheet is connected to the tube end of the inner tube of the double heat transfer tube, even if leakage occurs in the header portion, the direct connection between the heated fluid and the heated fluid is prevented. Mixing can be prevented.

As described above, according to the present embodiment, it is possible to safely and efficiently exchange heat for a fluid such as a flammable substance or a poison that is not desired to leak from the flow path. Therefore, by applying the heat exchanger of the present embodiment to the heat exchanger of the LNG cold energy utilization system, a safe and highly efficient LNG cold energy utilization system can be provided.

[0036]

An object of the present invention is to suppress the mixing of the fluid on the heated side and the fluid on the heated side in a heat exchanger for exchanging heat with a fluid that is not desired to leak, such as a flammable substance or a poison. To provide a heat exchanger that can be used.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a heat exchanger according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a heat transfer tube portion of the heat exchanger according to one embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a double pipe portion of the heat exchanger according to one embodiment of the present invention.

FIG. 4 is a schematic view of an LNG cold-heat utilization type gas turbine power generation system according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a safety mechanism according to one embodiment of the present invention.

[Explanation of symbols]

5: Combustor, 7: Gas turbine, 8: Generator, 9: Regeneration heat exchanger, 11, 12, 13 ... Nozzle, 18: Air flow path, 19: Natural gas flow path, 20: Inactive gas flow path , 22
... plate-like fins, 23 ... inner tube, 24 ... outer tube, 26 ... header, 27 ... tube plate, 30 ... trunk, 31 ... baffle plate, 32 ...
Lid, 33: double pipe, 35: wire, 40, 87: pipe, 43: LNG storage tank, 51: air compressor, 55
... stack, 70 ... heat exchanger, 75 ... gas pressure control valve,
76: nitrogen gas supply device, 77: nitrogen gas discharge valve, 80
... air blower, 81 ... pressure gauge, 82 ... gas detector, 83
... control circuit, 85 ... shut-off valve, 86 ... rupture disk, 88 ... flare stack.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koichi Chino 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi, Ltd. Electric Power & Electric Development Laboratory 3L103 AA44 CC21 CC22 CC26 DD08 DD18 DD33 DD38 DD42 DD62

Claims (11)

[Claims] 1. A heat transfer tube group constituted by a plurality of heat transfer tubes, a body accommodating the heat transfer tube group, and a heat transfer tube group provided at both ends of the heat transfer tube group. In a heat exchanger including a tube plate to be held and a baffle plate installed so as to form a flow path in the inner space of the body, the heat transfer tube includes an inner tube and an outer tube. A part of the outer surface of the inner tube and a part of the outer surface of the outer tube are formed so as to be in contact with each other directly or via a heat conductive member. . 2. A heat transfer tube group constituted by a plurality of heat transfer tubes, a body accommodating the heat transfer tube group, and end portions of the heat transfer tube group provided at both ends of the heat transfer tube group. In a heat exchanger comprising: a tube sheet to be held; and a baffle plate installed so as to form a flow path in the body inner space, the heat transfer tube includes an inner tube, an outer peripheral surface of the inner tube, An outer tube arranged so as to have a gap, wherein a part of the outer surface of the inner tube and a part of the inner surface of the outer tube are directly or through a heat conductive member. Characterized by being formed so as to be in contact with each other. 3. A heat transfer tube group constituted by a plurality of heat transfer tubes through which a first fluid flows, a body accommodating the heat transfer tube group, and a heat transfer tube group provided at both ends of the heat transfer tube group. A tube plate that holds each end of the heat tube group; and a baffle plate that is installed so as to form a flow path that allows a second fluid to flow through the outer peripheral portion of the heat transfer tube group in the body internal space. In the heat exchanger, the heat transfer tube is constituted by an inner tube and an outer tube, and an outer peripheral surface of the inner tube and an outer tube are formed so that a third fluid flows between the inner tube and the outer tube. A predetermined gap between the inner surface of the inner tube and a portion of the outer surface of the inner tube and a portion of the inner surface of the outer tube are formed so as to be in contact with each other directly or via a heat conductive member. A heat exchanger. 4. The heat transfer tube according to claim 1, wherein an outer surface of the outer tube is connected to an outer surface of another outer tube of the heat transfer tube by a heat conductive member. The heat exchanger according to any one of the above. 5. A second heat transfer tube having an outer diameter smaller than a minimum inner diameter of the first heat transfer tube is inserted into a tube of the first heat transfer tube having an inner surface subjected to groove processing or projection processing. By applying an inward mechanical force from the outer surface of the second heat transfer tube to reduce the outer diameter of the second heat transfer tube, the outer surface of the formed double tube was pre-drilled. A method for manufacturing a heat exchanger, comprising press-fitting fins. 6. A first heat transfer tube having a groove or a projection formed on an inner surface thereof is inserted into a plate-shaped fin which has been previously drilled, and fluid pressure or mechanical force is inserted into the first heat transfer tube. To expand the tube, join the plate-like fins and the first heat transfer tube, and provide a second heat transfer tube having an outer diameter smaller than the minimum inner diameter of the first heat transfer tube in the first heat transfer tube. Insert the heat tube and the second
Expand the pipe by applying fluid pressure or mechanical force to the heat transfer pipe of
A method for manufacturing a heat exchanger, comprising forming a double tube. 7. A method of manufacturing a heat exchanger, comprising the steps of: forming a first pipe having a groove or a projection formed on an inner surface thereof when manufacturing a double pipe;
The method for manufacturing a heat exchanger according to claim 5, wherein a second heat transfer tube whose outer surface is grooved or protruded is used instead of using the heat transfer tube. 8. The method of manufacturing a heat exchanger according to claim 1, wherein when the double pipe is manufactured, the first surface having a groove or a projection formed on an inner surface thereof is formed.
The method for manufacturing a heat exchanger according to claim 5, wherein a second heat transfer tube whose outer surface is grooved or protruded is used in addition to using the heat transfer tube. 9. The method for manufacturing a heat exchanger according to claim 1, wherein when the double pipe is manufactured, the first surface having a groove or a projection formed on an inner surface thereof is formed.
The heat exchanger according to claim 5 or 6, wherein a heat conductive member is inserted in an annular region between the first heat transfer tube and the second heat transfer tube instead of using the heat transfer tube of (1). Production method. 10. The method for manufacturing a heat exchanger according to claim 1, wherein in the step of press-fitting the fins pre-drilled into the outer surface of the double pipe, at least one pre-drilled baffle is mixed with the fins. The method for manufacturing a heat exchanger according to claim 5, wherein the plate is press-fitted. 11. The method for manufacturing a heat exchanger according to claim 1, wherein in the step of inserting the heat transfer tube into the fins that have been pre-drilled, at least one baffle plate that has been pre-drilled is mixed in the fins. The method for manufacturing a heat exchanger according to claim 6, wherein: