JP2008175449A - Multiple pipe-type heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiple pipe-type heat exchanger capable of reducing probability of electric corrosion, and detecting water leakage before electric corrosion. <P>SOLUTION: This multiple pipe-type heat exchanger is composed of a copper inner pipe 1 provided with a leakage detecting groove 4 on its outer surface, an aluminum outer pipe 2 covering an outer wall of the inner pipe 1 and composed of a number of refrigerant flow channels 3, an outer pipe terminal portion 5 disposed at a longitudinal end portion of the outer pipe 2 and having an inner peripheral part close to the inner pipe 1, and longer than an outer peripheral part of the outer pipe 2, and a branch portion 7 having a circular passage 6 corresponding to the refrigerant flow channels 3 and joined to the outer pipe terminal portion 5. A longitudinal end portion of the inner pipe 1 is longer than a longitudinal end portion of the outer pipe 2, a boundary between a tip of the outer pipe terminal portion 5 and the end portion of the inner pipe 1 is covered by a stretch heat shrinkable tube 8, and the leakage detecting groove 4 is formed by the halfway of the part covered by the heat shrinkable tube 8, thus the probability of electric corrosion of the aluminum outer pipe can be reduced, and the probability of flowing of components of refrigerating machine oil and the like existing in a CO<SB>2</SB>refrigerant flow channel into a water side can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a carbon dioxide (CO ₂ ) refrigerant and a multi-tube heat exchanger that exchanges heat between the refrigerant mixture and water, and in particular, a heat pump in which the pressure on the high-pressure side is equal to or higher than the critical pressure of the refrigerant. The present invention relates to a multi-tube heat exchanger applied to a supercritical heat pump type hot water supply apparatus or a supercritical heat pump type air conditioner that heats hot water or heating brine in a cycle.

  Conventionally, this type of multi-tube heat exchanger is composed of a copper inner tube and an aluminum outer tube covering the outer wall of the inner tube and closely contacting the outer wall of the inner tube. There are cylindrical multi-hole pipes in which a large number of refrigerant flow paths are formed, and the multi-hole flow path formed in the outer pipe is a carbon dioxide gas flow path and the inner pipe is a water flow path (for example, Patent Document 1).

  FIG. 3 shows a conventional multi-tube heat exchanger described in Patent Document 1. As shown in FIG. 3, the inner tube 1 is made of copper and the outer tube 2 is made of aluminum. The outer tube 2 is formed by forming a plurality of refrigerant flow paths 3 by extrusion. The outer surface of the inner tube 1 has a leak detection groove 4 that is grooved, and the end of the leak detection groove 4 is open to the outside air.

  The operation of the multi-tube heat exchanger configured as described above will be described below.

First, water flows in the inner pipe 1, and CO ₂ refrigerant flows in the refrigerant flow path 3 of the outer pipe 2 so as to face each other. After the inner tube 1 is inserted into the outer tube 2, the inner tube 1 is expanded in diameter so that the inner tube 1 and the outer tube 2 are brought into close contact with each other, molded to a predetermined length, and the terminal portion is joined. It constitutes an exchanger. Since the pressure of the CO ₂ refrigerant becomes equal to or higher than the critical pressure, the hole diameter is reduced by making the refrigerant flow path a multi-hole flow path, and the outer pipe is aluminized to reduce the cost. .

  On the other hand, when corrosion progresses from the inner surface of the copper inner pipe 1 that is a water flow path and reaches the contact portion with the aluminum outer pipe 2, water is discharged from the end of the leakage detection groove 4 to the outside. Can be discharged.

If the operation of the system is stopped by detecting the water, it is possible to avoid the danger that CO ₂ refrigerant, refrigeration oil, and the like generated by further progress of corrosion flow into the water side.
JP 2002-213895 A

  However, in the above conventional configuration, the end of the leak detection groove is open to the outside air, so moisture in the atmosphere enters from the end through the leak detection groove, and the copper inner tube and the aluminum There was a problem that battery corrosion occurred between the outer tube and electric corrosion.

  The present invention solves the above-described conventional problems, and is a multi-tube heat exchanger that achieves both reduction of the possibility of electrolytic corrosion and detection of water leakage before electrolytic corrosion. The purpose is to provide.

  In order to solve the above-described conventional problems, a multi-tube heat exchanger according to the present invention includes an inner tube, an outer wall that covers the outer wall of the inner tube, is in close contact with the outer wall of the inner tube, and includes a plurality of refrigerant channels. A tube, a leakage detection groove formed on the outer surface of the inner tube, and an outer tube having an inner peripheral portion adjacent to the inner tube at a longitudinal end of the outer tube that is longer than an outer peripheral portion of the outer tube A terminal portion and a branch portion having an annular passage corresponding to the refrigerant flow path and joined to the outer tube terminal portion, the longitudinal end portion of the inner tube being more than the longitudinal end portion of the outer tube Long, the boundary between the tip of the outer tube terminal and the end of the inner tube is covered with a stretchable coating, and the leak detection groove is provided halfway through the portion covered with the coating. is there.

  As a result, the end of the leak detection groove is covered with a coating and is not open to the outside air, so that moisture in the atmosphere can be prevented from entering the leak detection groove, and the copper inner tube and aluminum It is possible to reduce the possibility of electrolytic corrosion of the manufactured outer tube.

  Furthermore, even if corrosion progresses from the inner surface of the copper inner tube, which is the flow path of water, and reaches the close contact portion with the aluminum outer tube, the coating provided at the end of the leak detection groove is elastic. Since it has, the covering can be expanded by the water pressure applied to the end of the leakage detection groove, and the water itself can form a flow path and be discharged to the outside.

The multi-tube heat exchanger according to the present invention can reduce the possibility of electrolytic corrosion of an aluminum outer tube, and can also detect the leakage of water before electrolytic corrosion and the refrigerating machine oil present in the CO ₂ refrigerant flow path. It is possible to reduce the possibility that components such as these will flow into the water side.

The invention according to claim 1 is formed on the outer surface of the inner tube, the outer tube which covers the outer wall of the inner tube and is in close contact with the outer wall of the inner tube and which has a large number of refrigerant flow paths. A leakage detection groove, an outer tube end portion in which an inner peripheral portion adjacent to the inner tube at a longitudinal end portion of the outer tube is longer than an outer peripheral portion of the outer tube, and an annular shape corresponding to the refrigerant flow path A branch portion having a passage and joined to the outer tube terminal portion, and a longitudinal end portion of the inner tube is longer than a longitudinal end portion of the outer tube, and a tip end of the outer tube terminal portion and the inner tube By covering the boundary with the end of the tube with a stretchable coating and providing the leakage detection groove partway through the coating, moisture in the atmosphere can enter the leakage detection groove. Infiltration can be reduced, and the possibility of electrolytic corrosion of the copper inner tube and the aluminum outer tube can be reduced. Furthermore, even if corrosion progresses from the inner surface of the copper inner tube, which is the water flow path, and reaches the contact portion with the aluminum outer tube, the coating provided at the end of the leak detection groove is elastic. Because it has, the cover can be spread with the water pressure applied to the end of the leak detection groove, the water itself can make a flow path and drain it to the outside, and let the water leak be detected before electric corrosion The possibility that components such as refrigerating machine oil present in the CO ₂ refrigerant flow path will flow into the water side can be reduced.

  According to a second aspect of the present invention, in the first aspect of the invention, the coating is made of a material having a very small moisture permeation, thereby suppressing the penetration of moisture in the atmosphere from the surface to the inside of the coating. As a result, moisture becomes less likely to intervene at the boundary between the copper inner tube and the aluminum outer tube, and the possibility of electrolytic corrosion can be further reduced.

  According to a third aspect of the present invention, in the invention according to the first or second aspect, the covering is a tube-shaped resin molded product having heat-shrinkability, so that the tube-shaped resin molded product is heated after being inserted. By doing so, shrinkage is brought into close contact, and the gap can be further reduced.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the covering is made of an electrically insulating material, so that the outer tube end portion made of aluminum and the inner portion made of copper are made. The possibility of electrolytic corrosion at the boundary with the end of the tube can be reduced.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the refrigerant flow path formed in the outer pipe is a carbon dioxide flow path, and water flows in the inner pipe. By using the channel, it can be applied to a multi-tube heat exchanger of a supercritical heat pump (for example, a hot water supply device or an air conditioner) using carbon dioxide gas.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the same reference numerals are given to the same configurations as those of the conventional example or the above-described embodiments, and detailed description thereof will be omitted. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a side sectional view showing an end portion of a multi-tube heat exchanger according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of the multi-tube heat exchanger when refrigerant or water leaks in the same embodiment. It is a side cross-sectional enlarged view which shows an edge part.

1 and 2, a multi-tube heat exchanger 100 is made of an aluminum made of a copper inner tube 1 and an aluminum wall that covers the outer wall of the inner tube 1 and is in close contact with the outer wall of the inner tube 1, and is composed of a number of refrigerant flow paths 3. The outer tube 2 is formed with a leak detection groove 4 formed on the outer surface of the inner tube 1 in the tube axis direction. A refrigerant (for example, CO ₂ refrigerant) flows in the refrigerant flow path 3, and water flows in the inner pipe 1. The outer pipe 2 made of aluminum has a shape and thickness of the refrigerant flow path 3 having a strength that can sufficiently withstand even when the CO ₂ refrigerant reaches a critical pressure or higher. Also in the copper inner pipe 1, a thickness having corrosion resistance that does not cause a problem in actual use is secured, and an inner grooved pipe is preferable.

  In addition, the end of the multi-tube heat exchanger 100 is located at the end in the longitudinal direction of the outer tube 2, and the outer tube terminal portion 5 in which the inner peripheral portion adjacent to the inner tube 1 is longer than the outer peripheral portion of the outer tube 2. A branch portion 7 having an annular passage 6 corresponding to the refrigerant flow path 3 and joined to the outer tube terminal portion 5, and the longitudinal end portion of the inner tube 1 is longer than the longitudinal end portion of the outer tube 2. It is getting longer. The heat-shrinkable tube 8 is a covering material having elasticity that covers the boundary between the tip of the outer tube terminal 5 and the end of the inner tube 1, and leak detection grooves to the middle of the portion covered with the heat-shrinkable tube 8. 4 is provided.

  The operation and action of the multi-tube heat exchanger configured as described above will be described below.

  First, an outer tube 2 having a plurality of refrigerant flow paths 3 formed by aluminum extrusion is prepared, and a copper inner tube 1 is inserted inside the outer tube 2 so that liquid is preferably applied to the inner tube 1. The inner tube 1 is expanded until the inner tube 1 and the outer tube 2 are firmly brought into close contact with each other.

In rare cases, even when corrosion progresses from the inner surface of the copper inner tube 1 that is a water flow path and the water reaches the close contact portion with the outer tube 2 made of aluminum, electric current is generated between copper and aluminum. Before the erosion occurs and the aluminum pitting suddenly and reaches the refrigerant flow path 3 of the CO ₂ refrigerant, water is discharged from the leakage detection groove 4 to the outside of the multi-tube heat exchanger 100 and the water is detected. If the operation of the system is stopped, the possibility that components such as refrigerating machine oil existing in the CO ₂ refrigerant flow channel flow into the water side can be reduced.

  At this time, in the configuration of the conventional multi-tube heat exchanger, the end of the leak detection groove 4 is open to the outside air, so that moisture in the atmosphere constantly enters the inside from the end of the leak detection groove 4. The galvanic corrosion (electric corrosion) due to the battery action may gradually occur between the copper inner tube and the aluminum outer tube.

  Therefore, the boundary between the tip of the outer tube terminal 5 and the end of the inner tube 1 is covered with the heat shrink tube 8 and the leak detection groove 4 is provided partway through the heat shrink tube 8 (from the middle of the heat shrink tube 8). The leakage detection groove 4 is not provided up to the tip of the inner tube 1), so that the end of the leakage detection groove 4 is not opened to the outside air and moisture in the atmosphere can be prevented from entering the leakage detection groove 4. .

  In addition, since the heat shrinkable tube 8 has elasticity, when water reaches the close contact portion with the aluminum outer tube 2 due to the progress of corrosion, the water pressure applied to the end of the leakage detection groove 4 The heat-shrinkable tube 8 can be pushed outward and water is discharged to the outside (see FIG. 2). That is, by covering the end of the leak detection groove with a stretchable coating, it prevents the intrusion of moisture in the atmosphere, and the water has reached the close contact portion with the aluminum outer tube due to the progress of corrosion. In this case, the heat shrinkable tube 8 can be pushed outward by water pressure, and water can be discharged to the outside.

  In addition, by applying a material with extremely low moisture permeation to the heat-shrinkable tube 8, it is possible to suppress the water that permeates the heat-shrinkable tube 8, and to further prevent moisture from entering the leak detection groove 4. it can.

  Furthermore, the heat-shrinkable tube 8 is made of a highly electrically insulating coating that does not conduct electricity (preferably a thin film of polyester, polyethylene, or the like and has a thickness of 0.01 mm to 1 mm), so that the tip of the outer tube terminal portion 5 made of aluminum And electrolytic corrosion occurring at the boundary between the copper inner tube 1 and the end of the copper inner tube 1 can be prevented.

  Further, the heat shrinkable tube 8 is a tube-shaped resin material (preferably Sumitube) that shrinks when heated, so that the resin material itself contracts with the outer tube terminal portion 5 simply by heating after mounting. The gap through which moisture passes through the boundary of the end portion of the inner tube 1 is reduced, so that the inner tube 1 can be more closely attached and the workability is improved.

Therefore, it is possible to prevent the outer pipe made of aluminum from being eroded, and to reduce the possibility that components such as refrigeration oil existing in the CO ₂ refrigerant flow channel will flow into the water side by detecting leakage of water before erosion. It is possible to achieve both compatibility.

  In the present embodiment, the heat-shrinkable tube 8 is formed in a tube shape, but it goes without saying that it has the same effect as a tape winding.

  Further, in the present embodiment, the leakage detection groove 4 is provided on the outer surface of the inner tube 1, but it goes without saying that the leakage detecting groove 4 has the same function even if provided on the inner surface of the outer tube 2.

  As described above, the multi-tube heat exchanger according to the present invention can reduce the possibility of electrolytic corrosion of an aluminum tube, and can detect water leakage before electrolytic corrosion. It is applicable also to the use of a multi-tube heat exchanger such as for a hot water supply device or a heat pump type air conditioner.

Side sectional view which shows the edge part of the multipipe heat exchanger in Embodiment 1 of this invention The side cross-section enlarged view which shows the edge part of the multiple tube type heat exchanger at the time of the refrigerant | coolant or water leakage in the same embodiment Sectional view of a conventional multi-tube heat exchanger

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner pipe | tube 2 Outer pipe | tube 3 Refrigerant flow path 4 Leak detection groove 5 Outer pipe | tube terminal part 6 Annular flow path 7 Branching part 8 Heat shrinkable tube (covering material)
100 Multi-tube heat exchanger

Claims (5)

  An inner tube, an outer tube that covers the outer wall of the inner tube and is in close contact with the outer wall of the inner tube, and includes a plurality of refrigerant channels; a leak detection groove formed on an outer surface of the inner tube; and the outer tube An outer tube terminal portion having an inner peripheral portion adjacent to the inner tube that is longer than an outer peripheral portion of the outer tube, an annular passage corresponding to the refrigerant flow path, and the outer tube terminal A longitudinal end of the inner tube is longer than a longitudinal end of the outer tube, and the boundary between the distal end of the outer tube end and the end of the inner tube is expanded and contracted. A multi-tube heat exchanger in which the leakage detection groove is provided halfway along the portion covered with the covering material.   The multi-tube heat exchanger according to claim 1, wherein the covering is made of a material having extremely small moisture permeation.   The multi-tube heat exchanger according to claim 1 or 2, wherein the covering is a tubular resin molded product having heat shrinkability.   The multi-tube heat exchanger according to any one of claims 1 to 3, wherein the covering is an electrically insulating material that does not conduct electricity.   5. The multi-tube heat exchanger according to claim 1, wherein the refrigerant flow path formed in the outer pipe is a carbon dioxide gas flow path, and the inner pipe is a water flow path.