JP6029686B2 - Double tube heat exchanger and refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a double pipe heat exchanger that forms two flow paths by combining circular pipes having different pipe diameters and a refrigeration cycle apparatus using the double pipe heat exchanger.

  A double-pipe heat exchanger has a circular pipe with a small diameter (hereinafter referred to as an inner pipe) inserted into a circular pipe with a large diameter (hereinafter referred to as an outer pipe), and the inside of the inner pipe as the first flow path. The portion outside the inner tube and inside the outer tube is the second flow path, and heat exchange is performed between the first fluid in the first flow path and the second fluid in the second flow path.

  Moreover, in this double tube heat exchanger, as a device for improving the heat transfer performance, for example, there is a configuration disclosed in Patent Document 1. That is, in Patent Document 1, a heat transfer area expansion tube having a multi-leaf cross section is inserted into an annular second flow channel between the outside of the cylindrical inner tube and the inside of the cylindrical outer tube. And the method of improving heat-transfer performance by the expansion effect of a heat-transfer area is proposed.

JP 2012-063067 A

  Patent Document 1 described above merely discloses a device for expanding the heat transfer area. Here, the present inventors pay attention to performing heat transfer suitably in exchanging heat of the two-phase refrigerant.

  This invention is made in view of this, and when a two-phase flow flows through a 2nd flow path, it aims at providing the double pipe type heat exchanger etc. which can improve heat exchange performance. To do.

  In order to achieve the above-mentioned object, the double-tube heat exchanger of the present invention is inserted into the outer tube and the inner side of the outer tube, forms an annular region between the outer tube and the inner side. An inner pipe that forms one flow path, and a heat transfer area expansion pipe that has irregularities in the radial direction, is arranged inside the outer pipe and outside the inner pipe, and forms a second flow path in the annular region An inner surface of the portion of the heat transfer area expansion tube that is in close contact with the inner surface of the outer tube of the inner surface of the heat transfer area expansion tube, and an outer surface of the heat transfer area expansion tube of the inner surface of the outer tube The portions defining the second flow path in cooperation with each other are defined as non-groove formation ranges, the non-groove formation ranges are non-groove surfaces, and the groove formation candidate ranges are the inner surfaces of the heat transfer area expansion tubes. A portion of the second pipe defining the second flow path in cooperation with the outer surface of the inner tube, and a portion excluding the groove non-forming range, and the heat transfer A part of the outer surface of the product expansion pipe that cooperates with the inner surface of the outer pipe to define the second flow path, and a part of the outer surface of the inner pipe that cooperates with the inner surface of the heat transfer area expansion pipe. A groove extending in the flow direction is formed in at least a part or all of the groove formation candidate range.

  According to the present invention, heat exchange performance can be enhanced when a two-phase flow flows in the second flow path.

It is a figure which shows the internal structure of the double pipe | tube type heat exchanger which concerns on Embodiment 1 of this invention in the direction orthogonal to a pipe axis. It is sectional drawing of the double tube | pipe type heat exchanger by the II-II line | wire of FIG. It is a figure which expands and shows the 2nd flow path in FIG. It is a figure which isolate | separates and shows an outer tube | pipe, a heat-transfer area expansion tube, and an inner tube | pipe for the part of FIG. It is a figure which shows Example 1 of the refrigerating-cycle apparatus which uses a double tube type heat exchanger. It is a figure which shows Example 2 of the refrigerating-cycle apparatus which uses a double tube type heat exchanger. It is a figure which shows Example 3 of the refrigerating-cycle apparatus which uses a double tube type heat exchanger. It is a figure which shows Example 4 of the refrigerating-cycle apparatus using a double tube type heat exchanger. It is a figure of the same aspect as FIG. 3 regarding this Embodiment 2. FIG. It is a figure of the same aspect as FIG. 3 regarding this Embodiment 3. FIG.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

Embodiment 1 FIG.
FIG. 1 is a view showing the internal structure of a double-pipe heat exchanger according to Embodiment 1 of the present invention in a direction orthogonal to the tube axis, and FIG. 2 is a double view taken along line II-II in FIG. It is sectional drawing of a tubular heat exchanger. In addition, priority is given to the clarity of the figure, and in FIG. The double tube heat exchanger 1 has a double tube structure in which an inner tube 5 that is a relatively small diameter circular tube is inserted concentrically inside an outer tube 3 that is a relatively large diameter circular tube. have. The inner space of the inner tube 5 functions as the first flow path 7. On the other hand, a heat transfer area expansion tube 11 is accommodated in an annular region 9 outside the inner tube 5 and inside the outer tube 3.

  The heat transfer area expansion tube 11 has a plurality of convex portions 13 and a plurality of concave portions 15 as relative irregularities in the radial direction. As shown in the cross section of FIG. 2, the plurality of convex portions 13 are provided radially so as to protrude outward in the radial direction of the heat transfer area expansion tube 11. Further, the plurality of convex portions 13 are arranged at substantially equal intervals in the circumferential direction. On the other hand, each of the plurality of recesses 15 is located between the circumferential directions of the corresponding pair of protrusions 13. These recesses 15 are also located at substantially equal intervals in the circumferential direction. Accordingly, when viewed as a whole of the heat transfer area expansion tube 11, the plurality of convex portions 13 and the plurality of concave portions 15 are alternately positioned in the circumferential direction.

  In the present invention, various forms of the convex shape of the convex portion and the concave shape of the concave portion seen in the cross section of FIG. 2 relating to the heat transfer area expansion tube can be considered, but as an example, the first embodiment is as follows. is there. The heat transfer area expansion tube 11 includes a plurality of outer contact portions 17, a plurality of inner contact portions 19, and a plurality of continuous portions 21. As shown in FIG. 2, the outer surface 17a of the outer contact portion 17 of the heat transfer area expansion tube 11 and the inner surface 3b of the outer tube 3 are in close contact, and in this example, the outer surface 17a and the inner surface 3b are in surface contact. doing. That is, the outer surface 17 a of the outer contact portion 17 of the heat transfer area expanding tube 11 has substantially the same curvature as the inner surface 3 b of the outer tube 3. Similarly, the inner surface 19b of the inner contact portion 19 of the heat transfer area expanding tube 11 and the outer surface 5a of the inner tube 5 are in close contact, and in particular, in this example, the inner surface 19b and the outer surface 5a are in surface contact. That is, the inner surface 19 b of the inner contact portion 19 of the heat transfer area expanding tube 11 has substantially the same curvature as the outer surface 5 a of the inner tube 5. The same curved state may be obtained in the single state of each of the outer tube 3, the inner tube 5, and the heat transfer area expansion tube 11, or the center side or the radial direction of the double tube heat exchanger 1. You may obtain in the state which the assembly process accompanied by provision of some force from the outer side was completed.

  Each of the continuous portions 21 is located between the adjacent outer close contact portion 17 and the inner close contact portion 19. In the present embodiment, the plurality of outer contact portions 17 are positioned at equal intervals in the circumferential direction, and the plurality of inner contact portions 19 are also positioned at equal intervals in the circumferential direction. When viewed through the entire heat transfer area expansion tube 11, the arrangement pattern of the outer contact portion 17, the continuous portion 21, the inner contact portion 19, and the continuous portion 21 is repeated in the circumferential direction. Note that the convex portion 13 and the concave portion 15 do not have a clear boundary, and the convex portion 13 is constituted by an outer contact portion 17 and a portion closer to the outer side in the radial direction of the continuous portion 21, and the concave portion 15 is an inner contact portion. 19 and a portion closer to the inside in the radial direction of the continuous portion 21.

  In the annular region 9 described above, the inside of the convex portion 13 and the outside of the concave portion 15 function as the second flow path 23. That is, the second flow path 23 is defined in the annular region 9 by the heat transfer area expanding tube 11.

  More specifically, the second flow path 23 includes two portions, and the first portion includes the inner surface 17b of the outer contact portion 17 and the corresponding inner surfaces 21b of the pair of continuous portions 21. And the outer surface 5a of the inner tube 5. Moreover, the part of a 2nd aspect is demarcated by the outer surface 19a of the inner side contact | adherence part 19, the outer surface 21a of a corresponding pair of continuous part 21, and the inner surface 3b of the outer tube | pipe 3. As shown in FIG. The parts of the first aspect and the parts of the second aspect are alternately arranged in the circumferential direction.

  In such a configuration, the first fluid is circulated in the first flow path 7, and the second fluid is circulated in the second flow path 23. The first fluid and the second fluid have different temperatures, and heat exchange is performed between the first fluid and the second fluid via the heat conduction of the inner tube 5 and the heat transfer area expansion tube 11.

  In general, there is a relationship represented by the equation (1) among the exchange heat quantity Q, the heat transfer area A, the heat transfer coefficient K, and the temperature difference dT between the first fluid and the second fluid.

  Moreover, the heat transfer coefficient K can be represented by Formula (2).

  The meaning of each notation is as follows. α1: heat transfer coefficient of fluid 1, d1: hydraulic diameter of flow path 1, α2: heat transfer coefficient of fluid 2, d2: hydraulic diameter of flow path 2, λ: thermal conductivity of inner pipe, dio: inner pipe Outer diameter, doi: inner diameter of inner tube, R: thermal resistance

  Since the heat transfer area expansion tube 11 described above acts as a fin by contacting the inner tube 5, the heat transfer area can be expanded, and the exchange heat amount of the first fluid and the second fluid can be increased. .

  Here, the flow state of the refrigerant when the gas-liquid two-phase flow flows in the second flow path 23 will be described with reference to FIGS. 3 and 4 as well. FIG. 3 is a view of the same mode as FIG. 2 and is an enlarged view of the second flow path, and FIG. 4 relates to the portion of FIG. It is a figure which isolate | separates and shows. Here, in general, in the two-phase flow, the liquid refrigerant having a high heat transfer coefficient is in close contact with the tube wall, and the gas refrigerant having a low heat transfer coefficient flows through a portion away from the tube wall. That is, the liquid refrigerant is concentrated on the wall surfaces indicated by reference numerals 3b, 5a, 17b, 19a, 21a, and 21b shown in FIG.

  Therefore, in the present invention, the following groove non-formation range and groove formation candidate range are set, the groove non-formation range is a groove-free surface, and at least part or all of the groove formation candidate range is along the flow direction. A groove extending in the direction is formed. The first embodiment is an example in which grooves are formed in the entire groove formation candidate range.

  Details of the groove non-forming range and the groove forming candidate range will be described. Specifically, the inner surface (the inner surface 17b of the outer contact portion 17) of the portion of the heat transfer area expanding tube 11 that is in close contact with the inner surface 3b of the outer tube 3 in the inner surface of the heat transfer area expanding tube 11 is within the groove non-forming range. is there. Furthermore, the part which demarcates the 2nd flow path 23 in cooperation with the outer surface of the heat-transfer area expansion tube 11 among the inner surfaces 3b of the outer tube 3 is also a groove | channel non-formation range. A groove 25 described later is not formed in each of these groove non-formation ranges.

  Further, the groove formation candidate range is from the portion defining the second flow path 23 in cooperation with the outer surface 5a of the inner tube 5 in the inner surface of the heat transfer area expanding tube 11 to the aforementioned groove non-forming range (outer contact portion 17). Of the heat transfer area expanding tube 11 and the portion defining the second flow path 23 in cooperation with the inner surface 3b of the outer tube 3 (continuous). The outer surface 21a of the portion 21 and the outer surface 19a of the inner contact portion 19) and the portion of the outer surface 5a of the inner tube 5 that defines the second flow path 23 in cooperation with the inner surface of the heat transfer area expansion tube 11.

  In the first embodiment, as described above, no groove is formed in the non-groove formation range, and the groove is formed in the entire groove formation candidate range, and more specifically, as follows. A portion of the outer surface 5a of the inner tube 5 that defines the second flow path 23 in cooperation with the outer contact portion 17 and the pair of continuous portions 21, and an outer surface 19a of the inner contact portion 19 of the heat transfer area expanding tube 11 are continuous. Grooves 25 are formed in the outer surface 21 a and the inner surface 21 b of the part 21. Further, the inner surface 17b of the outer contact portion 17 and the inner surface 3b portion of the outer tube 3 that defines the second flow path 23 in cooperation with the inner contact portion 19 and the pair of continuous portions 21 are set as groove-free surfaces. . Although not particularly limited as the present invention, in the first embodiment, the outer surface 17a of the outer contact portion 17 of the heat transfer area expansion tube 11 and the inner surface 3b of the outer tube 3 that is in close contact with the outer surface 17a. The portion is a grooveless surface, and the inner surface 19b of the inner contact portion 19 and the outer surface 5a portion of the inner tube 5 that is in close contact with the inner surface 19b are grooveless surfaces.

  The groove 25 is formed so as to extend along the flow direction in order to smoothly flow the refrigerant in the flow direction. Note that the grooves in FIGS. 3 and 4 are schematically drawn, and in FIG. 2, the illustration of the grooves is omitted for the sake of clarity of the drawings.

  In addition, since it is possible to shape | mold the heat-transfer area expansion pipe | tube 11 by press molding or a drawing process, in order to simplify a process, the groove | channel 25 is shape | molded simultaneously at the time of a press molding or a drawing process. Further, the heat transfer area expansion tube 11 is configured such that the heat transfer area expansion tube 11 in which the groove 25 is formed is inserted into the annular region 9 between the outer tube 3 and the inner tube 5 to contract the outer tube 3. Or it is supported by the outer tube 3 and the inner tube 5 depending on whether the inner tube 5 is expanded.

  Alternatively, a mode in which the inner pipe 5 and the outer pipe 3 and the heat transfer area expansion pipe 11 are brought into close contact with each other is preferably joined by brazing the respective contact surfaces. Specifically, after assembling the heat transfer area expanding tube 11 to the outer tube 3 and the inner tube 5, a brazing material is applied to the contact surface, the brazing material is melted by brazing in a furnace, etc. You may braze. In addition, when it is difficult to apply the brazing material after the heat transfer area expansion tube 11 is assembled to the inner tube 5 and the outer tube 3, a clad material in which the brazing material is previously applied to the heat transfer area expansion tube 11 is used. You can braze it.

  According to the double tube heat exchanger 1 configured as described above, the following excellent advantages can be obtained. The predetermined portion of the outer surface 5a of the inner tube 5 and the outer surface 19a of the inner contact portion 19 are portions that are extremely close to the first flow channel 7 among the portions that define the second flow channel 23, and have an effectiveness as a heat transfer surface. The highest part. Moreover, the continuous part 21 exists between the part of the 1st aspect mentioned above of the 2nd flow path 23, and the part of the 2nd aspect, and the inner and outer surfaces of the continuous part 21 give the effect of a fin to the continuous part 21. It is a heat transfer surface that is effective when heat exchange is performed between the second fluid between the portion of the first embodiment and the portion of the second embodiment (internal relationship of the second flow path 23). . Therefore, the groove 25 is formed as described above, so that the predetermined portion of the outer surface 5a of the inner tube 5 near the first flow path 7, the outer surface 19a of the inner contact portion 19 that is in close contact with the inner tube 5, and the continuous portion. The liquid refrigerant can be actively collected on the inner and outer surfaces of 21. In addition, the predetermined portion of the inner surface 3b of the outer tube 3 and the inner surface 17b of the outer contact portion 17 which are less effective as a heat transfer surface far from the first flow path 7 are relatively groove-less surfaces. The liquid refrigerant is less likely to collect than the predetermined portion of the outer surface 5a and the outer surface 19a, and as a reaction effect, it assists the liquid refrigerant to collect on the predetermined portion of the outer surface 5a, the outer surface 19a and the inner and outer surfaces of the continuous portion 21. . That is, a large amount of liquid refrigerant having a high heat transfer rate is supplied to the predetermined portion of the inner surface 3b of the outer tube 3 and the inner surface 17b of the outer contact portion 17 which are less effective as the heat transfer surface, and accordingly, the heat transfer surface is increased accordingly. As described above, the supply amount of the liquid refrigerant to the predetermined portion of the outer surface 5a having high effectiveness, the outer surface 19a, and the inner and outer surfaces of the continuous portion 21 is suppressed from decreasing. As described above, according to the present embodiment, even when a gas-liquid two-phase flow flows in the second flow path, the heat exchange performance can be enhanced by effectively utilizing the heat transfer surface.

  In addition, in the first embodiment, the outer surface 17a of the outer contact portion 17 of the heat transfer area expanding tube 11 and the inner surface 3b portion of the outer tube 3 that is in close contact with the outer surface 17a are formed as groove-free surfaces. Likewise, the inner surface 19b of the inner contact portion 19 and the outer surface 5a portion of the inner tube 5 that is in close contact with the inner surface 19b are formed as non-grooved surfaces. The adhesiveness with the expansion tube 11 can be maintained high, and not only that, but the heat transfer efficiency by the heat transfer area expansion tube 11 is particularly high due to the high adhesion between the inner tube 5 and the heat transfer area expansion tube 11. And the presence of the heat transfer area expansion pipe 11 can be efficiently utilized.

  Next, an embodiment of a refrigeration cycle apparatus to which the above-described double tube heat exchanger 1 is applied will be described with reference to FIGS.

  As a first embodiment of the refrigeration cycle apparatus, a refrigeration cycle apparatus 101 shown in FIG. 5 includes a compressor 103, a condenser 105, an expansion valve 107, an evaporator 109, and the double pipe heat exchanger 1 described above. It has as a main component. In the double-pipe heat exchanger 1, the refrigerant (second fluid) of the high-pressure liquid from the outlet of the condenser 105 (before flowing into the inlet of the expansion valve 107) and the refrigerant 109 (flowing into the inlet of the compressor 103) Heat exchange is performed with the refrigerant (first fluid) of the low-pressure gas of the previous). By using the double-pipe heat exchanger 1 in this way, the inlet temperature of the condenser 105 increases, so that the capacity during heating is improved and the COP (value obtained by dividing the capacity by the input) is improved. It is possible to prevent the liquid refrigerant from returning.

  Next, as Example 2 of the refrigeration cycle apparatus, the refrigeration cycle apparatus 201 illustrated in FIG. 6 includes the compressor 103, the condenser 105, the first expansion valve 207a, the second expansion valve 207b, the evaporator 109, and the above-described components. The double tube heat exchanger 1 is provided as a main circuit component. The compressor 103, the condenser 105, the first expansion valve 207a, and the evaporator 109 form a basic refrigeration cycle circuit as in the first embodiment. The refrigeration cycle apparatus 201 is further provided with a bypass path 211, which is connected between the outlet of the condenser 105 and the inlet of the first expansion valve 207a at the first connection point 213a. The second connection point 213b is connected between the outlet of the evaporator 109 and the inlet of the compressor 103. The second expansion valve 207b is provided in the bypass passage 211.

  In the double-pipe heat exchanger 1, high-pressure liquid refrigerant (first fluid) from the outlet of the condenser 105 (before reaching the first connection point 213a) and from the outlet of the second expansion valve 207b of the bypass passage 211 Heat exchange is performed with a medium-pressure gas-liquid two-phase refrigerant (second fluid). The medium-pressure gas refrigerant after heat exchange in the double-tube heat exchanger 1 is sucked into the compressor 103. By using the double pipe heat exchanger in this way, the refrigerant circulation amount downstream from the first expansion valve 207a can be reduced, so that pressure loss can be reduced and COP can be improved.

  Next, as Example 3 of the refrigeration cycle apparatus, the refrigeration cycle apparatus 301 shown in FIG. 7 includes a compressor 303, a condenser 105, a first expansion valve 207a, a second expansion valve 207b, an evaporator 109, and the above-described components. The double tube heat exchanger 1 is provided as a main circuit component. The compressor 303, the condenser 105, the first expansion valve 207a, and the evaporator 109 constitute a basic refrigeration cycle circuit as in the first embodiment.

  In the double-pipe heat exchanger 1, high-pressure liquid refrigerant (first fluid) from the outlet of the condenser 105 (before reaching the first connection point 213a) and from the outlet of the second expansion valve 207b of the bypass passage 211 Heat exchange is performed with a medium-pressure gas-liquid two-phase refrigerant (second fluid). Then, the medium-pressure gas refrigerant after the heat exchange in the double-tube heat exchanger 1 is bypassed to the middle of the compressor section of the compressor 303. By using the double pipe heat exchanger in this way, the amount of refrigerant circulating downstream from the first expansion valve 207a can be reduced and the compression process can be performed in multiple stages. Input can be reduced and COP can be improved.

  Furthermore, the refrigeration cycle apparatus 401 shown in FIG. 8 uses the double-pipe heat exchanger 1 as a condenser itself of a basic refrigeration cycle circuit. The refrigeration cycle apparatus 401 includes a refrigerant (second fluid) of a normal condenser of a refrigeration cycle circuit and a fluid (first fluid) such as water or brine fed by a pump 415 in the double-tube heat exchanger 1. Is an example of an apparatus that supplies hot water by exchanging heat.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. FIG. 9 is a diagram of the same mode as FIG. The second embodiment is the same as the first embodiment described above except for the parts described below, and it is also the same that the refrigeration cycle apparatus of FIGS. 5 to 8 can be configured and implemented.

  The double-pipe heat exchanger 51 is an example in which the groove 25 extending along the flow direction is formed in at least a part of the groove formation candidate range. That is, in the second embodiment, among the predetermined portion of the outer surface 5a of the inner tube 5, the outer surface 19a of the inner contact portion 19, and the inner and outer surfaces of the continuous portion 21, which are groove formation candidate ranges, are shown in FIG. As shown, the groove 25 is formed only on the inner and outer surfaces of the continuous portion 21. In the second embodiment as well, as in the first embodiment, the liquid refrigerant can be efficiently collected on the inner and outer surfaces of the continuous portion 21 having high effectiveness as the heat transfer surface, and the gas and liquid are collected in the second flow path. Even when a two-phase flow flows, the heat exchange performance can be improved by effectively utilizing the heat transfer surface.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described. FIG. 10 is a diagram of the same mode as FIG. The third embodiment is the same as the above-described first embodiment except for the parts described below, and it is also the same that the refrigeration cycle apparatus of FIGS. 5 to 8 can be configured and implemented.

  The double tube heat exchanger 61 is also an example in which the groove 25 extending along the flow direction is formed in at least a part of the groove formation candidate range. In the third embodiment, as shown in FIG. 10, among the predetermined portion of the outer surface 5 a of the inner tube 5, the outer surface 19 a of the inner contact portion 19, and the inner and outer surfaces of the continuous portion 21, which are groove formation candidate ranges. Further, a groove 25 is formed only in the predetermined portion of the outer surface 5 a of the inner tube 5 and the outer surface 19 a of the inner contact portion 19. Also in this third embodiment, as in the first embodiment, even when a gas-liquid two-phase flow flows in the second flow path, the heat exchange surface is effectively utilized to enhance the heat exchange performance. be able to.

  Although the contents of the present invention have been specifically described with reference to the preferred embodiments, various modifications can be made by those skilled in the art based on the basic technical idea and teachings of the present invention. It is self-explanatory.

  For example, in the first embodiment described above, it is possible to modify the outer surface 17a of the outer contact portion 17 of the heat transfer area expansion tube 11 so that the groove 25 is formed. By modifying in this way, the groove 25 is provided as a uniform process on the entire outer surface of the heat transfer area expansion tube 11, and the manufacturing can be simplified due to the uniformity of the process. Moreover, even if it modifies in that way, the outer surface 17a of the outer side contact | adherence part 17 of the heat-transfer area expansion tube 11 closely_contact | adhered with the outer tube | pipe 3 is low in importance as a heat-transfer surface, and is used from a viewpoint of utilization of a heat-transfer surface. It does not reduce the effectiveness of the present invention. That is, it is possible to improve the ease of manufacturing while suitably maintaining the effective utilization of the heat transfer surface in the present invention.

  1, 51, 61 Double tube heat exchanger, 3 outer tube, 5 inner tube, 7 first flow path, 9 annular region, 11 heat transfer area expansion tube, 23 second flow channel, 25 grooves, 101, 201, 301,401 Refrigeration cycle apparatus.

Claims (8)

An outer tube,
An inner tube that is inserted inside the outer tube, forms an annular region with the outer tube, and forms a first flow path on the inner side;
It has unevenness in the radial direction, and is disposed inside the outer tube and outside the inner tube, and includes a heat transfer area expansion tube that forms a second flow path in the annular region,
In cooperation with the inner surface of the heat transfer area expansion tube portion of the inner surface of the heat transfer area expansion tube that is in close contact with the inner surface of the outer tube, and the outer surface of the heat transfer area expansion tube of the inner surface of the outer tube Each of the portions defining the second flow path is a groove-free surface,
Chi sac wall to form said second passage, from the outer surface in cooperation with the portion defining said second flow path in the inner tube of the inner surface of the front Kiden'netsu area larger tube except for the ungrooved surface A portion defining the second flow path in cooperation with the inner surface of the outer tube of the outer surface of the heat transfer area expanding tube, and the inner surface of the heat transfer area expanding tube of the outer surface of the inner tube and the portion defining the second passage cooperate to part or all of the double-pipe heat exchanger in which the groove is formed. The groove extends along a flow direction;
The double-tube heat exchanger according to claim 1. Of the inner surface of the outer tube, a portion that is in close contact with the outer surface of the heat transfer area expansion tube, a portion of the outer surface of the heat transfer area expansion tube that is in close contact with the inner surface of the outer tube, and an outer surface of the inner tube Of these, the portion that is in close contact with the inner surface of the heat transfer area expanding tube and the portion of the inner surface of the heat transfer area expanding tube that is in close contact with the outer surface of the inner tube are non-grooved surfaces,
The double-tube heat exchanger according to claim 1 or 2. After the groove is formed in the heat transfer area expansion tube, the heat transfer area expansion tube is inserted into the annular region between the outer tube and the inner tube, and the outer tube is contracted or the inner tube is expanded. By expanding the tube, the heat transfer area expansion tube is supported by the outer tube and the inner tube.
The double-pipe heat exchanger according to any one of claims 1 to 3. The inner tube and the outer tube, and the heat transfer area expansion tube are brazed,
The double-pipe heat exchanger according to any one of claims 1 to 4. The heat transfer area expansion tube is a clad material whose surface is coated with a brazing material,
The double-tube heat exchanger according to claim 5. The double pipe heat exchanger according to any one of claims 1 to 6,
In the double tube heat exchanger, heat exchange is performed between the refrigerants,
Refrigeration cycle equipment. The double pipe heat exchanger according to any one of claims 1 to 6,
In the double tube heat exchanger, heat exchange is performed between the refrigerant and water or brine.
Refrigeration cycle equipment.

Images