JP2008145068A - Refrigerant piping for heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide refrigerant piping for a heat exchanger, hardly causing stress corrosion cracks in the case where refrigerant piping such as refrigerant piping of a heat exchanger for supplying hot water is coated with heat insulating material where urea remains and used. <P>SOLUTION: In this copper-made refrigerant pipings 3A, 3B for the heat exchanger, piping material is made of phosphorous-deoxidized copper, and the pipings are coated with heat insulating material having urea remaining as residue. The pipings are used under the condition that tensile stress is applied by internal pressure in circulation of a refrigerant. The pipings are formed of oxygen-free copper, which will not cause corrosion crack due to tensile stress. Thus, when the oxygen-free copper not causing stress corrosion crack is adopted, stress corrosion crack of copper-made refrigerant pipings 3A, 3B in which the pipe material is formed of phosphorous-deoxidized copper, and the pipings are coated with heat insulating material having urea remaining as residue, and which is used under the condition that tensile stress is applied by internal pressure in circulation of the refrigerant, can be restrained as much as possible, so that the reliability of a product can be improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a configuration of a refrigerant pipe for a heat exchanger that does not cause corrosion cracking due to tensile stress.

  As a heat exchanger used for a heat exchanger for a water heater such as a heat pump type water heater, which is well known from the past, a double pipe composed of an inner pipe through which water flows and an outer pipe through which refrigerant flows. Thus, there is a double-pipe heat exchanger in which a heat exchanger body is configured by superimposing a large number of stages by winding this into an oval shape.

  In the case of such a double-pipe heat exchanger, if a hole is formed due to corrosion in the inner pipe through which water flows, water and refrigerant are mixed together. It was necessary to stop operation. Therefore, as a countermeasure, a leak detection pipe having a leak detection groove for guiding water leaked from the inner pipe is provided outside the inner pipe, so that the leakage of the water is quickly detected. Therefore, in this configuration, the heat exchanger is substantially constituted by a triple tube of an inner tube, a leak detection tube, and an outer tube. Therefore, in the case of the same configuration, there is a problem that it is difficult to bend into an oval shape and the number of parts is large, so that the manufacturing process is complicated and the increase in cost is difficult to avoid.

  Therefore, as a heat exchanger for a water heater as described above, a capillary tube having a smaller outer diameter (passage diameter) than the core tube forming the refrigerant passage is formed on the outer periphery of the long core tube forming the water passage on the inside. Two outer tubes made of a wound tube are spirally wound at a predetermined pitch, and these are wound into, for example, an oval shape, stacked in a number of stages, and then subjected to brazing or the like to form an integral shape, There has been proposed one in which the core tube side is a water passage and the outer tube side is a refrigerant passage (see Patent Document 1).

  According to such a configuration, even if there is a hole in the core tube forming the water passage, there is no risk that water will enter the refrigerant passage side unless there is a hole in the outer tube side. Since the leakage of water can be easily detected from the leakage state of the water on the outer peripheral surface of the core tube, the leakage detection tube as described above becomes unnecessary.

Japanese Patent No. 3587189 (Specification, second page, FIG. 1)

  However, a refrigerant pipe such as a heat exchanger for hot water supply that is made of phosphorous deoxidized copper, covered with a heat insulating material, and used under a condition in which a tensile stress acts due to internal pressure during refrigerant circulation, is as described above. There is a problem that stress corrosion cracking occurs due to the ammonia generated from the mixing of foaming urea and water remaining in the heat insulating material during the period of use, and cracks and refrigerant leakage occur in a short period of time.

  The present invention has been made to solve such problems. As described above, the refrigerant pipe for the heat exchanger is made of phosphorous deoxidized copper and is covered with a heat insulating material containing urea. In such a case, use oxygen-free copper that does not cause stress corrosion cracking or a copper alloy with a high stress corrosion cracking resistance as a constituent material to prevent the above-described corrosion cracking caused by tensile stress. It aims at providing the refrigerant | coolant piping for exchangers.

  The present invention has been made in order to achieve the above object, and includes the following effective problem solving means.

(1) First problem-solving means The first problem-solving means of the present invention is made of phosphorous deoxidized copper, covered with a heat insulating material in which urea remains as a residue, and tensile stress is applied by internal pressure during refrigerant circulation. It is copper refrigerant | coolant piping 3A, 3B for heat exchangers used on the conditions to perform, Comprising: It formed by the oxygen-free copper which does not produce the corrosion crack by tensile stress.

  In this way, when oxygen-free copper that does not cause stress corrosion cracking is used, heat exchange is performed under conditions in which urea remains as a residue and where tensile stress acts due to internal pressure during refrigerant flow Stress corrosion cracking of the dexterous copper refrigerant pipes 3A and 3B is suppressed as much as possible, and the reliability of the product is improved.

(2) Second Problem Solving Means The second problem solving means of the present invention is made of phosphorous deoxidized copper, covered with a heat insulating material in which urea remains as a residue, and tensile stress is applied by internal pressure during refrigerant circulation. The copper refrigerant pipes 3A and 3B for heat exchangers used under such conditions are characterized by being formed of a copper alloy having a high resistance to corrosion cracking due to tensile stress.

  As described above, when a copper alloy having a high resistance to corrosion cracking due to tensile stress is employed, it is covered with a heat insulating material in which urea remains as a residue, and is used under a condition in which tensile stress acts due to internal pressure during refrigerant flow. Stress corrosion cracking of the copper refrigerant pipes 3A and 3B for the heat exchanger is suppressed as much as possible, and the reliability of the product is improved.

(3) Third Problem Solving Means The third problem solving means of the present invention is the configuration of the first or second problem solving means, wherein the heat exchanger has a water passage pipe 1. The refrigerant pipes 3A and 3B are wound around the outer peripheral surface of the water passage pipe 1 and have a passage cross-sectional area smaller than the passage cross-sectional area of the water passage pipe 1. It is characterized by.

  Thus, the heat exchanger is configured to have the water passage pipe 1, and the refrigerant pipes 3 </ b> A and 3 </ b> B are wound around the outer peripheral surface of the water passage pipe 1. When the pipe 1 is configured to have a passage cross-sectional area smaller than the passage cross-sectional area, particularly when a tensile stress is employed in the refrigerant pipe, corrosion cracking due to the stress is likely to occur. The configuration of the problem solving means is effective.

(4) Fourth Problem Solving Means According to a fourth problem solving means of the present invention, in the configuration of the first, second or third problem solving means, the refrigerant flowing in the refrigerant pipes 3A, 3B is a CO ₂ refrigerant. It is characterized by being.

As described above, the copper heat exchanger in which the refrigerant flowing in the refrigerant pipes 3A and 3B is a high-temperature and high-pressure CO ₂ refrigerant (for example, 120 ° C., around 10K) has a large internal pressure during refrigerant circulation, and the refrigerant is at the same pressure. Since stress corrosion cracking of the piping portion is likely to occur, the configuration of the first, second, or third problem solving means works effectively.

As a result of the above, according to the present invention, the problem of stress corrosion cracking in the refrigerant pipe of the hot water supply heat exchanger using CO ₂ as the refrigerant and the high pressure side refrigerant pipe of the heat exchanger using R 410 as the refrigerant can be solved almost certainly. The reliability of the product can be greatly improved.

  FIG. 1 and FIG. 2 show, as an example, the configuration of a heat exchanger according to the best embodiment of the present invention suitable for configuring a heat exchanger for a hot water heater and refrigerant piping for the heat exchanger. .

  As shown in the drawing, the hot water supply heat exchanger has an outer diameter (passage diameter) smaller than that of the core tube 1 that forms the refrigerant passages 4A and 4B on the outer periphery of the long core tube 1 that forms the water passage 2 inside. Two outer tubes 3A and 3B made of a wound tube such as a capillary tube are spirally wound at a predetermined pitch, and this is wound into, for example, an oval shape and overlapped by a number of stages, and then brazed, etc. As a result, the core pipe 1 side is used as the water passage 2 and the outer pipes 3A and 3B are used as the refrigerant passages 4A and 4B. And the outer periphery is comprised and covered with the heat insulating material made to foam using urea as a foaming agent.

In this configuration, for example, a high-temperature (120 ° C.) and high-pressure (10 K) CO ₂ refrigerant is employed as the refrigerant flowing through the refrigerant pipes 4A and 4B. The outer tubes 3A and 3B are made of brittle phosphorous deoxidized copper (Cu = 99.5%) from which O ₂ (oxygen) is removed (deoxidized) by mixing P (phosphorus). .

  According to such a configuration, even if a hole is formed on the core tube 1 side forming the water passage 2, water enters the refrigerant passages 4A and 4B unless the hole is formed on the outer tubes 3A and 3B. There is no fear, and the leakage of water can be easily detected from the leakage state of water on the outer peripheral surface of the core tube 1 between the outer tubes 3A and 3B, and the leakage detection tube is not necessary.

In the case of such a configuration, as already described, the outer tubes 3A and 3B have a small diameter and at the same time, a predetermined tensile stress is generated by winding, and this tensile stress is a high temperature (120 ° C. during operation). ), And the diameter of the pipe is further increased by the circulation of the high-pressure (10K) refrigerant (CO ₂ ).

  Thus, the hot water supply used under the condition that the material of the piping is brittle phosphorous deoxidized copper and is covered with a heat insulating material in which urea as a foaming agent remains, and tensile stress acts on the internal pressure. The outer tubes (refrigerant pipes) 3A and 3B of the heat exchanger for use are subject to stress corrosion cracking due to ammonia generated from the heat insulating material during the period of use (performed by the reaction of surrounding water with urea remaining in the foamed part). There is a problem that occurs and causes cracks and refrigerant leakage in a short period of time.

  Therefore, in the present embodiment, in order to avoid such a problem, as described above, the outer tubes 3A and 3B are covered with a heat insulating material in which urea as a foaming agent remains as a residue and generates ammonia by reaction with water. In the case of being used, it is configured using oxygen-free copper that does not cause stress corrosion cracking or a copper alloy having a high stress corrosion cracking resistance as a material constituting the material.

  Thus, the outer pipe 3A, which is a copper refrigerant pipe of a heat exchanger for hot water supply, which is covered with a heat insulating material in which urea remains as a residue and is used under a condition in which a tensile stress acts due to an internal pressure during refrigerant circulation, When 3B is made of oxygen-free copper that does not cause corrosion cracking due to tensile stress, even if ammonia is generated from the heat insulating material during the period of use, stress corrosion cracking due to this will be suppressed as much as possible. Reliability is improved.

  On the other hand, in addition to oxygen-free copper, when using a copper alloy that has a high resistance to corrosion cracking due to tensile stress, stress corrosion cracking is suppressed as much as possible, and the product Reliability is improved.

  Like the hot water supply heat exchanger shown in the above embodiment, the heat exchanger is configured to have the core tube 1 as the water passage piping, and the outer tubes 3A and 3B as the refrigerant piping are the same. When wound around the outer peripheral surface of the core tube 1 and the passage cross-sectional area of the outer pipes 3A and 3B is configured to have a passage cross-sectional area smaller than the passage cross-sectional area of the core tube 1 In particular, when tensile stress is applied to the copper refrigerant pipes 3A and 3B as the refrigerant pipe, the above-described configuration is particularly effective because corrosion cracking due to the stress is likely to occur.

Furthermore, in the case of the above configuration, the refrigerant flowing through the outer pipes 3A and 3B, which are refrigerant pipes, is a high-temperature, high-pressure CO ₂ refrigerant.

As described above, the copper heat exchanger in which the refrigerant flowing in the outer pipes 3A and 3B, which are refrigerant pipes, is a high-temperature and high-pressure CO ₂ refrigerant is liable to generate a greater stress, and stress corrosion cracking of the refrigerant pipe portion is likely to occur. Therefore, the above configuration works particularly effectively.

As a result, according to the heat exchanger refrigerant pipe of the present embodiment, the conventional stress corrosion cracking problem in a hot water heat exchanger or the like using CO ₂ as a refrigerant can be solved almost certainly. Can be improved as much as possible.

  In addition, although it is necessary for the outer pipes 3A and 3B to be covered with a heat insulating material, the outer pipes 3A and 3B are suitable for use in an environment where moisture coexists.

  Further, the outer tubes 3A and 3B may be brazed (see the M portion in FIG. 2).

  The brazing may be performed by brazing in a furnace or other methods.

It is a partially cutaway perspective view showing the configuration of the hot water supply heat exchanger according to the best mode of the present invention. It is a cross-sectional view of the principal part of the heat exchanger for hot water supply.

Explanation of symbols

  1 is a core tube, 2 is a water passage, 3A and 3B are outer tubes, 4A and 4B are water passages, and M is a brazing part.

Claims (4)

  Copper refrigerant pipe (3A) for a heat exchanger (3A), which is made of phosphorous-deoxidized copper, covered with a heat insulating material in which urea remains as a residue, and used under conditions in which tensile stress acts due to internal pressure during refrigerant flow 3B)... A refrigerant pipe for a heat exchanger, which is formed of oxygen-free copper that does not cause corrosion cracking due to tensile stress.   Copper refrigerant pipe (3A) for a heat exchanger (3A), which is made of phosphorous-deoxidized copper, covered with a heat insulating material in which urea remains as a residue, and used under conditions in which tensile stress acts due to internal pressure during refrigerant flow 3B)... A refrigerant pipe for a heat exchanger, which is made of a copper alloy having a high resistance to corrosion cracking due to tensile stress.   The heat exchanger has a water passage pipe (1), and the refrigerant pipes (3A), (3B)... Are wound around the outer peripheral surface of the water passage pipe (1). The refrigerant pipe for a heat exchanger according to claim 1 or 2, wherein the refrigerant pipe is configured to have a passage cross-sectional area smaller than a passage cross-sectional area of the water passage pipe (1). Refrigerant pipe (3A), the heat exchanger refrigerant pipe according to claim 1, 2 or 3, wherein the a refrigerant CO ₂ refrigerant flowing through the (3B) ···.

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