JP2007218461A - Double tube type heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double tube type heat exchanger of high heat exchanging efficiency by preventing deposition of scale components. <P>SOLUTION: This double tube type heat exchanger comprises a small diameter tube 7 in which a first fluid flows, and a large diameter tube 8 disposed outside of the small diameter tube 7 to allow a second fluid to flow between the small diameter tube 7 and the large diameter tube 8. The small diameter tube 7 has the spiral shape, and pitch lengths of the spiral shape are various at an upstream side and a downstream side of the first fluid, so that the pitch length of the spiral shape is long at a place where the scale components are often deposited to reduce resistance of a flow channel, thus the scale components are hardly deposited, and heat transfer coefficient can be improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a double-pipe heat exchanger that exchanges heat between water and a refrigerant in a heat pump type hot water heater.

  FIG. 4 is a configuration diagram of a conventional heat pump type hot water heater. In FIG. 4, the heat pump type hot water heater includes a heat pump cycle in which a compressor 101, a hot water supply heat exchanger 102, a decompressor 103, and a heat source heat exchanger 104 are sequentially connected by a refrigerant pipe 105, a hot water storage tank 106, and a circulation pump 107. The hot water supply heat exchanger 102 is constituted by a hot water supply cycle in which the liquid pipes 108 are sequentially connected, and the hot water supply heat exchanger 102 performs heat exchange between the high-temperature refrigerant and the water to generate hot water. As such a hot water supply heat exchanger 102, a double-pipe heat exchanger configured by a plurality of inner tubes and outer tubes and having an inner tube formed in a spiral shape is used (for example, see Patent Document 1). ).

5A and 5B are configuration diagrams of a double-pipe heat exchanger of a conventional heat pump type hot water heater. In such a double-pipe heat exchanger, in order to increase the heat exchange efficiency between the first fluid flowing through the inner pipe and the second fluid flowing through the outer pipe, the pitch length of the spiral shape is reduced. is doing. Decreasing the pitch length of the spiral shape means increasing the number of spirals per unit length, and in addition to increasing the contact factor between fluids, turbulence is formed in the flow path of the second fluid. Therefore, the heat exchange efficiency is increased.
Japanese Patent Laying-Open No. 2005-221087

  However, although the heat exchange efficiency is improved, scale components (for example, calcium carbonate) are deposited in the second fluid during the heat exchange, and the resistance of the flow path is of course reduced. It had a problem of making it happen.

  The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a double-pipe heat exchanger that prevents precipitation of scale components and has high heat exchange efficiency.

  In order to solve the above-described conventional problems, a double-pipe heat exchanger according to the present invention is provided between a small-diameter pipe through which a first fluid flows and an outer side of the small-diameter pipe. A large-diameter pipe through which a second fluid flows, wherein the small-diameter pipe has a spiral shape, and the pitch length of the spiral shape is changed on the upstream side and the downstream side of the first fluid. is there.

  This makes it possible to reduce the flow path resistance by increasing the helical pitch length in places where scale components are likely to precipitate, making it difficult for the scale components to precipitate and improving the heat transfer coefficient. it can.

  It is possible to provide a double-pipe heat exchanger that prevents precipitation of scale components and has high heat exchange efficiency.

The first invention includes a small-diameter pipe through which a first fluid flows, and a large-diameter pipe provided outside the small-diameter pipe and through which a second fluid flows between the small-diameter pipe and the small-diameter pipe Is a spiral shape, and by changing the pitch length of the spiral shape on the upstream side and the downstream side of the first fluid, the pitch length of the spiral shape can be increased in places where scale components are likely to precipitate, The channel resistance can be reduced, the scale component is less likely to precipitate, and the heat transfer rate can be improved.

  In the second invention, in particular, in the first invention, the first fluid is a high-temperature fluid and the second fluid is a low-temperature fluid, so that the high-temperature fluid is circulated in the inner pipe, so that the heat dissipation loss is reduced to the maximum. And efficiently transfer heat to the cryogenic fluid.

  In the third invention, particularly in the second invention, the first fluid and the second fluid are in an alternating current, and the pitch length of the spiral shape is larger on the upstream side of the first fluid than on the downstream side. Thus, by increasing the pitch length of the second fluid outlet side, that is, the first fluid inlet side (upstream side), where the scale component is most likely to be generated, the scale component is hardly deposited.

  In a fourth aspect of the invention, particularly in the first or second aspect of the invention, the small-diameter pipe and the large-diameter pipe have a straight portion and a bent portion, and the helical pitch length of the bent portion is the pitch length of the straight portion. By making the length larger than this, the bent portion is more likely to disturb the flow than the straight portion, and the scale component is likely to be deposited. .

  In the fifth aspect of the invention, in particular, in the first to fourth aspects of the invention, by providing a plurality of small-diameter pipes, the route through which the high-temperature fluid passes increases, so that the heat transfer is more easily performed.

  In the sixth invention, in particular, in the second to fifth inventions, since carbon dioxide is used as the high-temperature fluid, the pressure is increased to a critical pressure or more, so heat is taken away by the water in the hot water heat exchanger. Therefore, it does not condense even when the temperature drops, and it becomes easy to form a temperature difference between the refrigerant and water in the entire area of the heat exchanger for hot water supply, so that hot water can be obtained and the heat exchange efficiency can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a configuration diagram of a double-pipe heat exchanger according to the first embodiment of the present invention. In FIG. 1, the double-pipe heat exchanger has two small-diameter tubes 7 in a spiral shape and is inserted into a large-diameter tube 8. In the present embodiment, carbon dioxide of high-temperature and high-pressure refrigerant discharged from the compressor, which is the first fluid, flows in the small-diameter pipe 7 and is formed between the large-diameter pipe 8 and the small-diameter pipe 7. Water, which is a second fluid that exchanges heat with high-temperature and high-pressure carbon dioxide, flows in the space. In order to perform efficient heat exchange, the refrigerant and water exchange with each other.

  The first fluid (refrigerant) flows in the direction of arrow A, the second fluid (water) flows in the direction of arrow B, and the helical pitch length P2 on the upstream side of the first fluid (refrigerant) is Further, the pitch length P1 is formed larger than the downstream helical pitch length P1. Usually, calcium carbonate, which is a scale component, has a property that it is difficult to dissolve at higher temperatures, and scale components are likely to be generated on the high temperature side (upstream side) of the first fluid (refrigerant). If the spiral pitch length P2 on the side (upstream side) is formed larger, the flow path resistance can be reduced, so that precipitation of scale components is suppressed and heat transfer is improved.

Carbon dioxide is used as the refrigerant in the heat pump cycle, and in the double pipe heat exchanger, the refrigerant is pressurized above the critical pressure, so heat is taken away by the water in the double pipe heat exchanger. Even if the temperature drops, it does not condense and it is easy to form a temperature difference between the refrigerant and water in the entire area of the double-pipe heat exchanger, so that hot water can be obtained and heat exchange is achieved. High efficiency can be achieved. Furthermore, since carbon dioxide is relatively inexpensive and stable, it is possible to reduce product cost and improve reliability. In addition, since the ozone depletion coefficient is zero and the global warming coefficient is as low as about 1700 of the alternative refrigerant HFC-407C, a product that is friendly to the global environment can be provided.

  In the present embodiment, the two pitch lengths P1 and P2 have been described. However, as shown in FIG. 2, the pitch length is higher on the higher temperature side (upstream side) of the first fluid (refrigerant). In this case, the pitch length is not limited to the two pitch lengths P1 and P2, but P1, P2,..., Pn (P1 <P2 <.. .. <Pn) The pitch length may be changed as appropriate. By setting it as such a structure, since the pitch length becomes long toward the higher temperature side (upstream side) of the first fluid (refrigerant), the spiral shape is configured using the two pitch lengths P1 and P2. As compared with the above, a fine pitch length interval can be set, and the heat transfer rate is not greatly impaired.

  As described above, in the present embodiment, the higher the high temperature side (upstream side) of the first fluid (refrigerant), the larger the pitch length of the small-diameter pipes, thereby suppressing the precipitation of scale components and thus heat. The transmission rate can be improved.

(Embodiment 2)
FIG. 3 is a configuration diagram of a double-pipe heat exchanger according to the second embodiment of the present invention. In FIG. 3, the double-pipe heat exchanger has two small-diameter pipes 7 in a spiral shape and is inserted into a large-diameter pipe 8. In the present embodiment, carbon dioxide of high-temperature and high-pressure refrigerant discharged from the compressor, which is the first fluid, flows in the small-diameter pipe 7 and is formed between the large-diameter pipe 8 and the small-diameter pipe 7. Water, which is a second fluid that exchanges heat with high-temperature and high-pressure carbon dioxide, flows in the space. In order to perform efficient heat exchange, the refrigerant and water exchange with each other. Further, in the present embodiment, the small diameter tube 7 and the large diameter tube 8 have a straight portion 10 and a bent portion 11.

  In the double pipe heat exchanger configured as described above, in the straight portion 10, the small diameter tube 7 has a helical shape with a pitch length P1, and in the bent portion 11, the small diameter tube 7 has a pitch length. A spiral shape is formed by the length P2. Further, there is a relationship of P1 <P2 between the pitch length P1 and the pitch length P2. This is because the flow of fluid is more turbulent in the bent portion 11 than in the straight portion 10, and therefore, a scale component is easily generated. Therefore, in order to suppress the generation of the scale component, the fluid flow is not disturbed as much as possible. As described above, the pitch length in the bent portion 11 is made larger than the pitch length in the straight portion 10.

  Carbon dioxide is used as the refrigerant in the heat pump cycle, and in the double pipe heat exchanger, the refrigerant is pressurized above the critical pressure, so heat is taken away by the water in the double pipe heat exchanger. Even if the temperature drops, it does not condense and it is easy to form a temperature difference between the refrigerant and water in the entire area of the double-pipe heat exchanger, so that hot water can be obtained and heat exchange is achieved. High efficiency can be achieved. Furthermore, since carbon dioxide is relatively inexpensive and stable, it is possible to reduce product cost and improve reliability. In addition, since the ozone depletion coefficient is zero and the global warming coefficient is as low as about 1700 of the alternative refrigerant HFC-407C, a product that is friendly to the global environment can be provided.

  As described above, in this embodiment, the pitch length of the spiral shape of the first fluid is formed larger at the bent portion than at the straight portion, thereby suppressing the precipitation of the scale component and thus the heat transfer coefficient. Can be improved.

  As described above, the double-pipe heat exchanger according to the present invention includes an integrated heat pump type hot water heater in which a heat pump cycle and a hot water supply cycle are integrally configured, a separate heat pump type hot water heater configured separately, and a hot water source. It can be applied to water-refrigerant heat exchangers of various heat pump water heaters such as a direct hot water heat pump type water heater that can discharge hot water heated by a heat exchanger for a bath. It is applicable also to the heat pump apparatus which has this.

Sectional drawing of the double-pipe heat exchanger in Embodiment 1 of this invention Sectional drawing of the double-pipe heat exchanger in the same embodiment Sectional drawing of the double-pipe heat exchanger in Embodiment 2 of this invention Configuration diagram of conventional heat pump water heater (A) Configuration of a conventional water-refrigerant heat exchanger (b) Cross-sectional view of a conventional water-refrigerant heat exchanger

Explanation of symbols

7 Small-diameter pipe 8 Large-diameter pipe 10 Bent part 11 Linear part 101 Compressor 102 Heat exchanger for hot water supply 103 Depressurizer 104 Heat exchanger for heat source 105 Refrigerant pipe 106 Hot water tank 107 Circulation pump 108 Liquid pipe

Claims (6)

A small-diameter pipe through which the first fluid flows; and a large-diameter pipe provided outside the small-diameter pipe and through which the second fluid flows between the small-diameter pipe, the small-diameter pipe having a spiral shape, A double-pipe heat exchanger, wherein the pitch length of the spiral shape is changed between the upstream side and the downstream side of the first fluid. The double-tube heat exchanger according to claim 1, wherein the first fluid is a high-temperature fluid and the second fluid is a low-temperature fluid. The double pipe according to claim 2, wherein the first fluid and the second fluid are used as an alternating current, and the pitch length of the spiral shape is larger on the upstream side of the first fluid than on the downstream side. Type heat exchanger. The small-diameter pipe and the large-diameter pipe have a straight portion and a bent portion, and the pitch length of the spiral shape of the bent portion is larger than the pitch length of the straight portion. The double pipe heat exchanger as described. The double pipe heat exchanger according to any one of claims 1 to 4, wherein a plurality of small diameter pipes are provided. The double-pipe heat exchanger according to any one of claims 2 to 5, wherein carbon dioxide is used as the high-temperature fluid.

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