JP2019113222A - Double-pipe heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double tube heat exchanger having fins which have good heat exchange efficiency, are easy to bend, and can follow deformation of a bending portion without damage. SOLUTION: The outer pipe 2 is composed of an inner pipe 3 inserted inside the outer pipe, a first flow path 5 is formed between the outer pipe and the inner pipe, and a second flow is formed inside the inner pipe. In the double tube type heat exchanger 1 in which the path 6 is formed, the central portion 12 extending inside the inner tube 3 along the central axis of the inner tube 3 and being curved or bent at two or more points, and the inner tube 3 A metal fin 4 having a cross-sectional shape including both end portions 13 in contact with the inner surface of the crosspiece and elastically deformable in the cross-sectional shape is inserted. [Selection diagram] Fig. 2

Description

  The present invention relates to a double pipe heat exchanger provided with an outer pipe and an inner pipe.

  An internal heat exchanger that improves the cooling efficiency of the evaporator by causing the car air conditioner to exchange heat between the high temperature liquid refrigerant from the condenser that constitutes the refrigeration cycle and the low temperature gas refrigerant from the evaporator that likewise constitutes the refrigeration cycle. May be used. This internal heat exchanger comprises an outer pipe and an inner pipe disposed in the outer pipe, and a flow path of high temperature liquid refrigerant from the condenser is formed between the outer pipe and the inner pipe, It is a double-pipe heat exchanger in which a low temperature gas refrigerant flow path from an evaporator is formed inside.

  In the double-pipe heat exchanger, since heat exchange is performed via the inner and outer wall surfaces of the inner pipe, the refrigerant flowing near the inner surface of the inner pipe contributes to heat exchange, but the refrigerant flowing in the central portion It is hard to say that it contributes. Conventionally, it has been proposed to arrange fins inside the inner pipe in order to make the refrigerant flowing in the center of the inner pipe also contribute to heat exchange.

  For example, in Patent Document 1, a heat transfer fin formed of a corrugated tube having a radial cross section in the inner pipe is disposed in contact with the inside of the pipe wall of the inner pipe, and fluid preferentially flows inside the heat transfer fin. In order to prevent this, a double-tube heat exchanger is described in which a column forming an annular orifice is provided inside the heat transfer fins. In this double-pipe heat exchanger, the fluid flowing in the inner pipe is forced to be guided to the heat transfer fins by the columns, and the contact efficiency between the heat transfer fins and the fluid is said to be improved. The pressure drop is large due to the presence of the column inside. Moreover, although a double heat exchanger may be suitably bent according to the space of an installation place, when there are a heat-transfer fin and a column, there exists a problem that bending will become difficult.

Patent Document 2 describes a double-pipe heat exchanger in which a heat transfer promoter for an inner pipe comprising a screw tape, a static mixer or the like is inserted into an inner pipe. In this double-pipe heat exchanger, the refrigerant flowing in the inner pipe is accelerated by the heat transfer promoting member for the inner pipe, and it is said that the heat transfer is promoted by the turbulent flow. Similarly, bending is difficult due to the presence of twisted heat transfer enhancers.

  In Patent Document 3, as in Patent Document 1, a corrugated fin including a wave top, a wave bottom and a connecting portion is disposed in the inner pipe, and a plurality of louvers forming refrigerant passing holes in the connecting portion of the fin are arranged. A dual-tube heat exchanger is described which is provided and having a torsion plate disposed inside the wave bottom of the fins. In this double-pipe heat exchanger, the fluid flowing in the inner pipe is stirred by the refrigerant passage hole and the refrigerant is deflected to the fins by the torsion plate to improve the heat exchange efficiency. The pressure loss is large due to the presence of the plate. Further, there is a problem that bending is difficult due to the presence of the corrugated fins and the torsion plate.

Unexamined-Japanese-Patent No. 11-183062 JP 2001-201275 A JP, 2014-224670, A

  The present invention has been made in view of the problems of the prior art, and has a high heat exchange efficiency, is easy to bend, and has a double-pipe heat exchange having fins which can follow deformation of a bent portion without breakage. The task is to provide

  As means for solving the above problems, the present invention comprises an outer pipe and an inner pipe inserted into the outer pipe, and a first flow path is formed between the outer pipe and the inner pipe. In the double-pipe heat exchanger, in which the second flow path is formed inside the inner pipe, the inside of the inner pipe extends along the central axis of the inner pipe, and bending or bending at two or more places It has a cross-sectional shape which consists of the center part which carried out, and the both-ends which contact the inner surface of the above-mentioned inner pipe, and metal fins which can be elastically deformed in the above-mentioned cross section are inserted.

  In the present invention, heat exchange between the first fluid and the second fluid is performed via the inner wall of the inner pipe. In the case where the first fluid at high temperature and high pressure flows in the first channel between the outer pipe and the inner pipe and the second fluid at low temperature and low pressure flows in the second channel inside the inner pipe, In addition to heat transfer from the inner surface of the wall to the second fluid of the inner tube, heat conduction from the inner surface of the inner tube wall to both ends of the fin to the central portion, and second from the surface of the central portion of the fin Heat transfer to the fluid transfers heat to the second fluid flowing through the central portion of the inner tube. Since the central portion of the fin is curved or bent at two or more points, the heat transfer area with the central portion of the second fluid can be made larger, so that the second fluid flowing in the central portion of the inner pipe and Heat exchange is performed efficiently. Further, since the fins inserted into the inner pipe can be elastically deformed within the cross section, the double pipe heat exchanger can be easily bent depending on the installation location. Furthermore, the fins should maintain contact with the inner surface of the inner pipe without breakage, following the compression direction and the expansion direction, even in the case of uneven deformation of the inner pipe caused by bending. Can.

  The fin has an S-shaped central portion in cross-sectional shape.

  The fins are formed with notches at constant intervals in the axial direction of the inner pipe at both end portions of the cross-sectional shape.

  The fins consist of a plurality of fins divided in the central axis direction of the inner pipe, and each of the plurality of fins is inserted out of phase around the central axis of the inner pipe.

  Both end portions of the fin are in contact with the inner surface of the inner pipe by the elasticity of the fin.

  The edge of the both ends of the fin is in contact with the inner surface of the inner pipe with an edged surface.

  According to the present invention, since the fins inserted into the inner pipe are curved or bent at two or more central portions, the heat transfer area with the central portion of the second fluid can be further increased. The heat exchange with the second fluid flowing through the central portion of the inner pipe is efficiently performed. Further, since the fins inserted into the inner pipe can be elastically deformed within the cross section, the double pipe heat exchanger can be easily bent depending on the installation location. Furthermore, the fins should maintain contact with the inner surface of the inner pipe without breakage, following the compression direction and the expansion direction, even in the case of uneven deformation of the inner pipe caused by bending. Can.

BRIEF DESCRIPTION OF THE DRAWINGS The longitudinal cross-sectional view of the double-pipe-type heat exchanger which concerns on 1st Embodiment of this invention. The expanded cross-sectional view of the II-II line of FIG. FIG. 2 is a perspective view showing an outer pipe, an inner pipe and fins of the double-pipe heat exchanger of FIG. 1. The expanded cross-sectional view of the fin before inserting in an inner pipe. The perspective view which shows the state which bent the double pipe | tube type heat exchanger of FIG. The perspective view of the double pipe | tube type heat exchanger which concerns on 2nd Embodiment of this invention. The perspective view of the double pipe | tube type heat exchanger which concerns on 3rd Embodiment of this invention. FIG. 8 is an enlarged cross-sectional view of the double-pipe heat exchanger of FIG. 7; The expanded cross-sectional view of the double-pipe type heat exchanger which shows the modification of the fin for inner tubes. The expanded cross-sectional view of the double pipe | tube type heat exchanger which shows the other modification of the fin for inner pipes.

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

  FIG. 1 shows a double-pipe heat exchanger 1 according to a first embodiment of the present invention. The double-pipe heat exchanger 1 includes an outer pipe 2, an inner pipe 3 inserted into the outer pipe 2, and an inner pipe fin 4 inserted into the inner pipe 3. In the present embodiment, the double-pipe heat exchanger 1 is an internal heat exchanger for a car air conditioner, and the first flow path 5 between the outer pipe 2 and the inner pipe 3 is a liquid refrigerant of high temperature and high pressure Flow, the low-temperature low-pressure gas refrigerant flows through the second flow path 6 in the inner pipe 3 and both refrigerants are described as counterflows, but conversely, the low-temperature low-pressure gas The high temperature and high pressure refrigerant may flow through the second flow path 6, or both may be parallel flows.

  As shown in FIG. 2, the outer tube 2 is made of an extruded aluminum material having a circular cross section, and a plurality of ribs 7 extending in the longitudinal direction on the inner surface are formed at equal intervals in the circumferential direction. Both ends of the outer pipe 2 are joined to the outer surface of the inner pipe 3 and closed. The outer pipe 2 is formed with an outer pipe inlet 8 into which the high temperature and high pressure liquid refrigerant flows, and an outer pipe outlet 9 from which the liquid refrigerant having exchanged heat with the gaseous refrigerant in the inner pipe 3 flows out.

  The inner pipe 3 is made of an aluminum extruded section having a circular cross section, and has an outer diameter inscribed in or close to the tip of the rib 7 of the outer pipe 2. One end of the inner pipe 3 is an inner pipe inlet 10 where a low temperature low pressure gas refrigerant flows in, and an inner pipe flow out of which the gas refrigerant having completed heat exchange with the liquid refrigerant between the outer pipe 2 and the inner pipe 3 flows out And an outlet 11.

  The inner tube fins 4 extend along the central axis of the inner tube 3 as shown in FIG. 3 and have a length substantially equal to at least the length of the heat exchange area between the outer tube 2 and the inner tube 3 . The inner tube fins 4 are formed of a metal material having a high thermal conductivity such as stainless steel or aluminum. As shown in FIG. 2, the inner tube fin 4 has a cross-sectional shape including a central portion 12 curved at two points and both end portions 13 contacting the inner surface of the inner tube 3, and both sides in the cross section It is elastically deformable against the force acting on the end 13. In addition, the inner pipe fins 4 can be elastically deformed even when bending with the axial center line of the inner pipe 3 as the neutral axis. The tips 13 a of the both side ends 13 of the cross section of the inner tube fin 4 are bent so as not to damage the inner surface of the inner tube 3. Moreover, the contact area with the inner surface of the inner tube 3 becomes large by the edge bending of this front-end | tip 13a, and heat conductivity improves. The central portion 12 of the cross section of the inner pipe fin 4 is formed to be curved in an S-shape in which two semicircles are continuous, and is continuous with the both end portions 13. The inner tube fins 4 can be formed by pressing a metal plate material. The thickness of the material of the inner tube fins 4 is preferably 0.3 mm, but is not limited thereto.

  As shown in FIG. 4, the inner pipe fins 4 are formed so that the dimension between the tips 13 a and 13 a of the both side ends 13 and 13 is larger than the inner diameter of the inner pipe 3 before insertion into the inner pipe 3. ing. As shown in FIG. 3, when inserting the inner pipe fins 4 into the inner pipe 3, the both side ends 13, 13 are held down, and the dimension between the tips 13 a, 13 a of the both side ends 13, 13 is the inner pipe Insert from the tip while reducing the inner diameter of 3. Thereby, as shown in FIG. 2, in the both-sides 13 of the inner tube fin 4, the surface of the edge 13 a of the edge 13 is elastically contacted with the inner surface of the inner tube 3. The central portion 12 of the cross section of the inner tube fin 4 is a region not affected by the heat transfer with the inner surface of the inner tube 3 and has a diameter of about 3/4 of the inner diameter of the inner tube 3. The region inside (the region surrounded by the dashed dotted line circle in FIG. 2).

  Next, the operation of the double-pipe heat exchanger 1 will be described. In FIG. 2, the heat held by the high-temperature high-pressure liquid refrigerant flowing in the first flow path 5 between the outer pipe 2 and the inner pipe 3 is transferred to the outer surface of the inner wall of the inner pipe 3. In addition to the heat conduction in the tube wall and the heat transfer from the inner surface of the tube wall of the inner tube 3, the heat conduction from the inner surface of the tube wall of the inner tube 3 to the inner tube fin 4 and the surface of the inner tube fin 4 The heat transfer is conducted to the low temperature low pressure gaseous refrigerant flowing in the second flow path 6 of the inner pipe 3.

  As a result, heat is generated between the high temperature / high pressure liquid refrigerant flowing in the first flow path 5 between the outer pipe 2 and the inner pipe 3 and the low temperature / low pressure gas refrigerant flowing in the second flow path 6 in the inner pipe 3. The high temperature and high pressure liquid refrigerant in the first flow passage 5 between the outer pipe 2 and the inner pipe 3 is cooled, and the low temperature and low pressure gaseous refrigerant in the second flow path 6 in the inner pipe 3 is heated. Ru. In particular, since the heat transfer area of the central portion 12 curved in an S-shape is larger than the heat transfer area of the both end portions 13 of the inner tube fin 4, the gas flowing in the vicinity of the central portion 12 of the second flow passage 6 of the inner tube 3 The refrigerant also contributes to the heat exchange, and the heat exchange efficiency is good.

  The inner tube fin 4 is a double tube as shown in FIG. 5 since the central portion 12 is curved in an S shape and elastically deformable in the cross section and also elastically deformable in bending. The heat exchanger 1 can be easily bent depending on the installation location. Furthermore, the inner tube fins 4 contact the inner surface of the inner tube 3 without breakage, following the compression direction as well as the extension direction with respect to the uneven deformation of the inner tube caused by bending. Can be held.

  FIG. 6 shows a double-pipe heat exchanger 1a according to a second embodiment of the present invention. The double-pipe heat exchanger 1a is the same as the first embodiment except that rectangular notches 14 are formed at regular intervals in the axial direction of the inner pipe 3 at both end portions 13 of the inner pipe fin 4 It is the same as that of the double-pipe type heat exchanger 1 which concerns, the same code is attached to the corresponding part, explanation is abbreviated.

  The shape of the notch 14 is not limited to a rectangular shape, and may be triangular, semicircular, semielliptical, or in the form of a slit. The depth of the notch 14 of the inner tube fin 4 may be from the tip 13 a of the both end 13 to the bending start point of the S-shaped central portion 12. The pitch of the plurality of notches 14 in the axial direction of the inner pipe 3 of the inner pipe fin 4 is preferably the same degree as the inner diameter of the inner pipe 3.

  As described above, since the notches 14 are provided at both side ends 13 of the inner pipe fin 4, the tips 13 a of the both ends 13 of the inner pipe fin 4 and the inner pipe 3 when the inner pipe fin 4 is inserted into the inner pipe 3. The resistance due to friction with the inner surface of the inner tube is reduced, and the inner tube fins 4 can be easily inserted. In addition, the bending rigidity of the inner pipe fins 4 is lowered, and the bending of the double pipe heat exchanger 1a becomes easier. Furthermore, the inner tube fins 4 contact the inner surface of the inner tube 3 without breakage, following the compression direction as well as the extension direction with respect to the uneven deformation of the inner tube caused by bending. Can be held.

  FIG. 7 shows a double-pipe heat exchanger 1b according to a third embodiment of the present invention. This double-pipe heat exchanger 1b is a double-pipe heat exchanger according to the first embodiment except that the inner pipe fins 4 are composed of a plurality of fins 4a and 4b divided in the central axis direction of the inner pipe. It is the same as 1 and attaches the same numerals to corresponding parts and omits the explanation.

  Each of the plurality of fins 4 a and 4 b is inserted out of phase around the central axis of the inner pipe 3. The length of the fins 4a and 4b is preferably 5 to 7 times the inner diameter of the inner tube 3. For example, when the inner diameter of the inner tube 3 is 16 mm, the length of the fins 4a and 4b is preferably 80 to 112 mm. The phases of the fins 4a and 4b adjacent to each other in the axial direction of the inner pipe 3 may be shifted by 90 ° as shown in FIG. 8, but may be shifted by 60 °, and they may be shifted to any phase. .

  As shown in FIG. 8, the flow of the gas refrigerant flowing through the second flow passage 6 inside the inner pipe 3 is divided into a flow along one surface of the inner pipe fins 4b and a flow along the other surface, but adjacent When flowing into the downstream inner pipe fin 4a, the upstream part flows along one surface of the inner pipe fin 4b, and the other side of the Because it mixes with a part of the heat exchange bias, heat exchange efficiency is enhanced.

  Further, since the plurality of inner pipe fins 4a and 4b are separated in the axial direction of the inner pipe 3, the bending rigidity is lowered, and the bending of the double pipe heat exchanger 1b is further facilitated. Furthermore, the inner tube fins 4a and 4b follow the compression direction and the extension direction without being damaged, even with the uneven deformation of the inner tube generated by the bending process, and with the inner surface of the inner tube 3. Can hold contact with

  The present invention is not limited to the above embodiments, and various modifications can be made. For example, if the shape of the central portion 12 of the cross section of the inner tube fin 4 is a shape having two or more curved portions or bent portions so that the heat exchange area of the central portion 12 becomes larger than the both end portions 13 , S-shaped is not limited. For example, it may be in the form of Ω as shown in FIG. 9 or in the form of zigzag as shown in FIG.

  In addition, although the inner pipe fin 4 of each of the embodiments extends straight along the central axis of the inner pipe 3, at least a portion other than both side ends and the edge bending surface of the inner pipe fin 4 is the inner pipe. A louver may be provided by being inclined with respect to the central axis of 3 or formed into a waveform in the central axis direction of the inner pipe 3 or by cutting. Furthermore, although the surface of the inner tube fin 4 in each of the above embodiments is smooth in the central axis direction of the inner tube 3, the heat transfer area may be increased by performing concavo-convex processing such as dimple processing.

1, 1a, 1b: Double-pipe heat exchanger 2. Outer tube 3. Inner tube 4. Fin for inner tube 5. First channel 6. Second channel 7. Rib 8 Outer tube inlet 9. Outer Tube outlet 10: Inner tube inlet 11: Inner tube outlet 12: Center portion 13: Both ends 13a: Tip 14: Notch

Claims (6)

An outer pipe and an inner pipe inserted into the outer pipe, a first flow path is formed between the outer pipe and the inner pipe, and a second flow path is formed in the inner pipe. In a dual-tube heat exchanger,
Inside of the inner pipe, it has a cross-sectional shape that is formed along the central axis of the inner pipe and includes two or more curved or bent central portions and both side ends that contact the inner surface of the inner pipe. A double-pipe heat exchanger characterized in that elastically deformable metal fins are inserted in the cross section.   The double-pipe heat exchanger according to claim 1, wherein the fin has an S-shaped central portion in a cross-sectional shape.   The double-pipe heat exchanger according to claim 1 or 2, wherein the fins are formed with notches at regular intervals in the axial direction of the inner pipe at both end portions of the cross-sectional shape. .   The fins are composed of a plurality of fins divided in the central axis direction of the inner pipe, and each of the plurality of fins is inserted out of phase around the central axis of the inner pipe. The double pipe heat exchanger according to any one of claims 1 to 3.   The double-pipe heat exchanger according to any one of claims 1 to 4, wherein both ends of the fin are in contact with the inner surface of the inner pipe by the elasticity of the fin. The double-pipe heat exchanger according to any one of claims 1 to 5, wherein the edge of each side end of the fin is in contact with the inner surface of the inner pipe with an edged surface.

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