JP2008175450A - Heat exchanger - Google Patents

Abstract

[PROBLEMS] To reduce the cross-sectional area of the water flow path and increase the flow velocity by a simple method that does not require high precision or large equipment, or increase the heat transfer area of the inner pipe by increasing the pipe length. Even if not, a double-pipe heat exchanger having excellent heat exchange performance is provided.
A copper pipe 10 made of copper having a small cross-sectional shape is wound around the outer surface of an outer pipe 3 of the refrigerant pipe 2 in a spiral manner so as to be spaced apart in the axial direction and the circumferential direction of the refrigerant pipe 2. 2 can be provided on the outer surface of the outer pipe 3 so as to be spaced apart in the axial direction or the circumferential direction of the refrigerant pipe 2, causing discrete shear flow in the direction perpendicular to the outer wall surface. While keeping the flow resistance near the outer wall as small as possible, the temperature boundary layer formed by the hot water flowing near the outer wall and the relatively low temperature water flowing relatively far from the outer wall can be disturbed. .
[Selection] Figure 6

Description

  The present invention relates to a heat exchanger for exchanging heat between a fluid such as water and two fluids such as a refrigerant in a device such as an air conditioner and a hot water supply, particularly a heat pump type hot water heater.

  Conventionally, as this type of heat exchanger, an inner pipe having a refrigerant flow path formed therein, an outer pipe provided outside the inner pipe and having a water flow path formed between the inner pipe, There is one in which a double tube composed of is formed (see, for example, Patent Document 1).

  FIG. 13 is a plan view of a conventional heat exchanger described in Patent Document 1, and FIG. 14 is a cross-sectional view of the conventional heat exchanger described in Patent Document 1.

  As shown in FIGS. 13 and 14, this heat exchanger 101 is a double-pipe heat exchanger, and is provided outside the inner tube 103, an inner tube 103 in which a refrigerant channel 102 is formed. A copper outer tube 105 having a water flow path 104 formed between the inner tube 103 and the inner tube 103 is provided with two inner tubes 103. The inner pipe 103 is composed of a copper refrigerant pipe 106 and a copper leak detection pipe 107 provided on the outer periphery of the refrigerant pipe 106, and the refrigerant pipe 106 is expanded or the leak detection pipe 107 is contracted. As a result, the refrigerant pipe 106 and the leak detection pipe 107 are in close contact with each other. A large number of leak detection grooves 108 are formed along the piping direction on the inner surface of the leak detection pipe 107, and an air layer is formed in the leak detection groove 108. Further, the leak detection groove 108 is connected to a leak detection sensor (not shown) provided outside, and the refrigerant or water leaking from the inner tube 103 or the outer tube 105 leaks to the outside through the leak detection groove 108. However, it is detected by a leak detection sensor.

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

The heat exchanger 101 is formed by a double pipe of an inner pipe 103 and an outer pipe 105, and heat is passed through a refrigerant pipe 106 and a leak detection pipe 107 in which the refrigerant and water are made of copper having good thermal conductivity and are in close contact with each other. Since they are exchanged, the inner tube 103 has a large contact area with water, and the heat exchange efficiency can be improved. In addition, even if a hole or a crack is generated in the refrigerant pipe 106 or the leak detection pipe 107 due to corrosion or the like and the refrigerant or water leaks, the leak can be reliably detected through the leak detection groove 108. The refrigerant wall 106 and the leakage detection pipe 107 form a double boundary wall between the refrigerant and water, and even if a defect such as a hole or a crack occurs in one of the refrigerant and water, the refrigerant and water There is no risk of mixing with each other. Therefore, the reliability of the heat exchanger 101 can be maintained high. In addition, since the heat exchanger 101 is a double tube type, bending can be easily performed, manufacturing costs can be reduced, and compactness can be achieved.
JP-A-2005-69620

  However, in the above-described conventional configuration, the outer surface of the inner tube 103 that contacts heat and transfers heat is a smooth round tube made of copper. Therefore, the velocity boundary layer (or temperature boundary layer) is easily developed, and the heat exchange capability is improved. In order to improve, it has been necessary to increase the flow velocity, increase the tube length of the heat exchanger 101, and increase the heat transfer area of the inner tube 103.

  For this reason, in the above-described method, first, when the diameter of the outer pipe 105 is reduced and the cross-sectional area of the water flow path 104 is reduced in order to increase the flow velocity, mineral components such as calcium (Ca) are contained in the tap water. Therefore, when heated and the temperature of water rises, the solubility of calcium decreases and calcium dissolved in water precipitates, and the precipitated calcium adheres to the outer wall of the inner tube 103 and the inner wall of the outer tube 105, There was a problem that the heat flow path 104 is clogged and the heat exchanger 101 does not function. Further, when the tube length of the heat exchanger 101 is increased, there is a problem that the size of the heat exchanger 101 is increased or the weight is increased.

  The present invention solves the above-mentioned conventional problems, without reducing the cross-sectional area of the water flow path to increase the flow velocity, or without increasing the pipe length to increase the heat transfer area of the inner pipe, The object is to provide a double-pipe heat exchanger with high accuracy and a simple construction method that does not require large-scale equipment and excellent heat exchange performance.

  In order to solve the above-described conventional problems, the heat exchanger according to the present invention includes a first pipe through which a fluid A flows and a second pipe through which the fluid B flows. Is provided in the first tube, and the outer surface of the second tube is formed with irregularities in the tube axis direction or the circumferential direction of the second tube.

  Thereby, due to the unevenness of the outer surface of the second tube, a difference occurs in the shear force of the water flowing near the outer wall surface of the second tube, and a shear flow perpendicular to the outer wall surface is generated. Heat transferability can be improved by disturbing and mixing the temperature boundary layer formed by the high-temperature water flowing near the outer wall surface and the relatively low-temperature water flowing relatively far from the outer wall surface. At the same time, the heat exchange area between the refrigerant and water can be increased.

  The double-pipe heat exchanger of the present invention is a water flow system in which a temperature boundary layer formed by high-temperature water near the outer wall surface and relatively low-temperature water separated from the outer wall surface is disturbed and mixed. The heat exchange performance of the heat exchanger can be improved without reducing the cross-sectional area of the path to increase the flow velocity or increasing the pipe length to increase the heat transfer area of the inner pipe.

  The invention according to claim 1 includes a first pipe through which fluid A flows and a second pipe through which fluid B flows, and the second pipe is disposed in the first pipe. In this configuration, the outer surface of the second tube is formed with irregularities in the tube axis direction or the circumferential direction of the second tube, so that the water flowing near the outer wall surface of the second tube is sheared. Due to the difference in force and the generation of shear flow perpendicular to the outer wall, it was formed by hot water flowing near the outer wall and relatively cold water flowing relatively far from the wall. When the temperature boundary layer is disturbed and mixed, heat transfer can be improved, and heat exchange performance of the heat exchanger can be improved.

  According to a second aspect of the present invention, in the first aspect of the present invention, convex portions are formed on the outer surface of the second tube so as to be spaced apart from each other in the tube axis direction or the circumferential direction of the second tube. As a result, the shear flow generated on the outer wall surface of the second pipe can be generated separately in the pipe axis direction or the circumferential direction of the second pipe, and the flow resistance in the vicinity of the outer wall surface of the second pipe can be increased. It can be kept low.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the outer surface of the second tube is formed by spirally winding a plate-like fin around the outer surface of the second tube. No need for large manufacturing equipment that performs rolling to provide unevenness directly on the tube, and by making the spiral spacing close or rough, the tube of the second tube on the outer surface of the second tube Large irregularities in the axial direction or circumferential direction or large convex portions separated from each other can be provided, and formed by high temperature water flowing near the outer wall surface and relatively low temperature water flowing relatively far from the outer wall surface. The temperature boundary layer can be disturbed.

  The invention according to claim 4 is the invention according to claim 1 or 2, wherein a small-diameter wire is spirally wound around the outer surface of the second pipe, thereby forming an outer surface of the second pipe. It does not require a large-scale manufacturing facility that directly performs rolling to provide unevenness, and furthermore, positioning for raising the fins, technology for performing the winding strength with high accuracy, simple construction method that does not require equipment, and low cost By making the spiral spacing close or rough with a simple facility, the outer surface of the second tube can be provided with convexities that are uneven or spaced apart in the tube axis direction or circumferential direction of the second tube. The temperature boundary layer formed by high temperature water flowing near the outer wall surface and relatively low temperature water flowing relatively far from the outer wall surface while keeping the flow resistance near the outer wall surface of the second pipe low Can be disturbed.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein a plurality of the second tubes are spirally twisted together to form a plurality of the second tubes. The twisting pitch is gentler than the pitch of the fin or the small-diameter wire wound around the second pipe in a spiral manner, so that the hot water flowing near the outer wall surface flows away from the outer wall surface. The temperature boundary layer formed by the relatively low temperature water can be disturbed. Further, the flow of the fluid A is turbulently disturbed as a swirl flow in the entire fluid A in the first tube, and heat is diffused in the entire fluid A in the first tube, thereby improving the heat transfer coefficient. Further, a gap is formed between the plurality of twisted second pipes by fins or small-diameter wires, and the entire area around the plurality of second pipes can be made an effective contact area with the fluid A.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the second pipe is thermally formed with a gap between at least a part of the outer pipe and the inner pipe. It is configured to be able to detect leakage of fluid A or fluid B by leaking fluid A or fluid B through the gap while keeping the thermal resistance small by being a close double tube. In this case, the fluid A and the fluid B are difficult to mix with a double wall, and the leakage is detected to the outside through a gap, so that safety is improved.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the fluid A and the fluid B are opposed to each other, and the fluid B passes through the second pipe. By heating the fluid A, the average temperature difference between the fluid A and the fluid B can be increased and the amount of heat exchange can be increased.

  According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the outer surface of the second pipe on the outflow side of the fluid A compared to the inflow side of the fluid A. Since the provided convex portions are further separated in the tube axis direction, when the fluid A is heated by the fluid B, calcium contained in water is precipitated on the outflow side where the temperature becomes high, and the second on the outflow side. Since the convex portions that are likely not to adhere to the outer surface of the tube become sparse, it is possible to prevent the calcium scale from growing and sealing the flow of water without stopping the heat exchange. In addition, since the flow rate of water is not reduced, a decrease in heat transfer coefficient with the second pipe can be suppressed as much as possible, and a decrease in heat transfer coefficient as a whole heat exchanger can be suppressed as much as possible.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the fluid A is water and the fluid B is carbon dioxide, so that water for a heat pump water heater is used. High heat pump efficiency can be obtained by using it as a refrigerant heat exchanger.

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

(Embodiment 1)
1 is a plan view of a heat exchanger according to Embodiment 1 of the present invention, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 3 is a perspective view of a main part of the heat exchanger according to the same embodiment. It is.

  1 to 3, the heat exchanger body 1 has a double wall 2a in which an outer tube 3 and an inner tube 4 having a leak detection groove 5 on the inner surface are in close thermal contact with each other. A copper refrigerant pipe 2 in which carbon dioxide flows, and a copper water pipe 6 that is substantially coaxial with the refrigerant pipe 2 and that has the refrigerant pipe 2 therein and in which water flows through a substantially annular portion between the refrigerant pipe 2 and It is composed. The outer surface of the outer tube 3 of the refrigerant tube 2 is spirally wound so that the copper fins 7 having a thin cross-sectional shape are in close contact with each other so as to be separated in the tube axis direction and the circumferential direction of the refrigerant tube 2.

  In addition, the carbon dioxide inlet 8a and outlet 8b of the refrigerant pipe 2 and the water inlet 9a and outlet 9b of the water pipe 6 are provided so that their flows face each other.

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

  First, carbon dioxide flows inside the refrigerant pipe 2, water flows oppositely through the annular portion between the water pipe 6 and the refrigerant pipe 2, and the carbon dioxide passes through the double wall 2 a of the outer pipe 3 and the inner pipe 4. Carbon and water exchange heat.

  Here, between carbon dioxide and water, it has a leakage detection groove 5 on the inner surface, and carbon dioxide and water leak through the leakage detection groove 5 and can be detected by a detection sensor (not shown). Therefore, in order to ensure a sufficient contact area while providing the double wall 2a for ensuring safety, high thermal conductivity is obtained through the double wall 2a of the outer tube 3 and the inner tube 4.

  Furthermore, since the carbon dioxide in the refrigerant pipe 2 and the water between the water pipe 6 and the refrigerant pipe 2 are opposed to each other, efficient heat exchange can be realized, and as a water refrigerant heat exchanger for a heat pump water heater By using it, high heat pump efficiency can be obtained.

  Then, a thin plate-like fin 7 is spirally wound around the outer surface of the outer tube 3 of the refrigerant tube 2, so that an advanced processing technique and rolling for processing the fin on the outer surface of the outer tube 3 of the refrigerant tube 2 are performed. The large shearing force of water flowing in the vicinity of the outer wall surface of the outer pipe 3 of the refrigerant pipe 2 can be provided without the need for a large-scale manufacturing facility for carrying out, and can be provided with a large convex portion separated in the pipe axis direction or circumferential direction of the refrigerant pipe 2 The high-temperature water flowing in the vicinity of the outer wall surface of the outer tube 3 of the refrigerant pipe 2 and the outer wall surface are relatively generated while causing a shear flow in a direction perpendicular to the outer wall surface in a discrete manner and suppressing flow resistance to a low level. It is possible to disturb the temperature boundary layer formed by the relatively low-temperature water flowing away from each other, and heat transfer can be improved by mixing.

  In addition, by making the spiral interval close or rough, it is possible to easily set large irregularities in the tube axis direction or the circumferential direction of the refrigerant tube 2 or large convex portions separated from each other. Various performances of the water-side pressure loss and the heating capacity of the heat exchanger 1 can be designed with good balance.

  In the embodiment of the present invention, the fan 7 has a thin plate shape, but the same effect can be obtained by using a needle shape or a corrugated plate shape.

  In the embodiment of the present invention, the material of the outer tube 3, the inner tube 4, the water tube 6 and the fin 7 of the refrigerant tube 2 is made of copper, but the same applies to brass, SUS, corrosion-resistant iron, aluminum alloy, and the like. The effect can be obtained.

  In the embodiment of the present invention, carbon dioxide is used as the refrigerant flowing through the refrigerant pipe 2. However, the same effect can be obtained with a refrigerant such as R410A.

(Embodiment 2)
4 is a plan view of a heat exchanger according to Embodiment 2 of the present invention, FIG. 5 is a cross-sectional view taken along the line BB of FIG. 4, and FIG. 6 is a cutaway perspective view of the main part of the heat exchanger according to the same embodiment. It is. In addition, about the same structure as Embodiment 1, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  4 to 6, the copper wire 10 having a small cross-sectional shape is spirally wound around the outer surface of the outer tube 3 of the refrigerant tube 2 so as to be separated in the tube axis direction and the circumferential direction of the refrigerant tube 2. Yes.

  The operation of the heat exchanger 1 configured as described above will be described below.

  Technology for performing high-precision positioning and winding strength for raising fins without the need for large-scale manufacturing equipment that performs rolling to provide irregularities directly on the outer surface of the outer pipe 3 of the refrigerant pipe 2 With a simple construction method and inexpensive equipment that does not require an apparatus, the outer surface of the outer pipe 3 of the refrigerant pipe 2 can be provided with convex portions spaced apart in the pipe axis direction or circumferential direction of the refrigerant pipe 2, and discretely A shear flow in a direction perpendicular to the outer wall surface is caused, and the flow resistance in the vicinity of the outer wall surface of the refrigerant pipe 2 is suppressed as much as possible, while the high-temperature water flowing in the vicinity of the outer wall surface and the water flowing relatively away from the wall surface The temperature boundary layer formed by the low temperature water can be disturbed.

  In the present embodiment, the wire 10 has a circular cross-sectional shape, but the same effect can be obtained even when the wire 10 has a quadrangular shape, a polygonal shape, or a different diameter.

(Embodiment 3)
FIG. 7 is a plan view of the heat exchanger according to the third embodiment of the present invention, and FIG. 8 is a part of part C (water inflow side) of FIG. 7 showing the main part of the heat exchanger according to the same embodiment. FIG. 9 is a partial plan view in which a part of a portion D (water outflow side) in FIG. 7 showing a main part of the heat exchanger in the same embodiment is cut out. In addition, about the same structure as Embodiment 1, 2, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  7 to 9, the copper wire 11 having a small cross-sectional shape on the outer surface of the outer tube 3 of the refrigerant tube 2 on the water outflow side is further separated in the tube axis direction or the circumferential direction than the water inflow side. Arranged.

  The operation of the heat exchanger 1 configured as described above will be described below.

  In the case of water heated by carbon dioxide, the wire 11 with respect to the tube axis direction of the refrigerant tube 2 is loosely wound on the outflow side where the temperature is high. Since a convex part becomes sparse, it can suppress that a calcium scale grows and does not seal the flow of water, and stops heat exchange. In addition, since the flow rate of water is not reduced, a decrease in heat transfer coefficient with the refrigerant pipe 2 can be suppressed as much as possible, and a decrease in heat transfer coefficient as a whole can be suppressed as much as possible.

(Embodiment 4)
10 is a plan view of a heat exchanger according to Embodiment 4 of the present invention, and FIG. 11 is a cross-sectional view taken along line EE of FIG. FIG. 12 is a plan view of a main part of the heat exchanger according to the same embodiment. In addition, about the same structure as Embodiment 1, 2, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  10 to 12, the two refrigerant tubes 2X are spirally twisted with each other, and the twist pitch of the two refrigerant tubes 2X is spirally wound around the outer surface of the outer tube 3 of the refrigerant tube 2X. It is gentler than the pitch of the small-diameter copper wire 10.

  The operation of the heat exchanger 1 configured as described above will be described below.

  First, high-temperature water flowing near the outer wall surface of the outer tube 3 of the refrigerant tube 2X flows away from the outer wall surface by a small-diameter wire 10 spirally disposed on the outer surface of the outer tube 3 of the refrigerant tube 2X. The temperature boundary layer formed by the relatively low temperature water can be disturbed. Further, the entire water in the water pipe 6 is swirled to disturb the flow, and heat is diffused throughout the water, thereby improving the heat transfer coefficient.

  Furthermore, a gap is formed by the wire 10 between the two twisted refrigerant pipes 2X, and almost the entire periphery of the two refrigerant pipes 2X can be made an effective contact area with water.

  In the embodiment of the present invention, the number of the refrigerant pipes 2X is two, but the same effect can be obtained with three or more.

  In the present embodiment, the small-diameter wire 10 is wound around the refrigerant pipe 2X, but the same effect can be obtained by winding plate-like fins around the refrigerant pipe 2X.

  As described above, since the heat exchanger according to the present invention can improve the heat exchange performance, heat pump equipment such as a heat pump water heater, household, commercial air conditioner, heat pump washing and drying machine, It can also be applied to uses such as fuel cells.

The top view of the heat exchanger in Embodiment 1 of this invention AA sectional view of FIG. Cutaway perspective view of the main part of the heat exchanger in the same embodiment The top view of the heat exchanger in Embodiment 2 of this invention BB sectional view of FIG. Cutaway perspective view of the main part of the heat exchanger in the same embodiment The top view of the heat exchanger in Embodiment 3 of this invention The fragmentary top view which excised a part of C section (water inflow side) of FIG. 7 which shows the principal part of the heat exchanger in the embodiment The partial top view which excised a part of D section (water outflow side) of FIG. 7 which shows the principal part of the heat exchanger in the same embodiment The top view of the heat exchanger in Embodiment 4 of this invention EE sectional view of FIG. Cutaway plan view of the main part of the heat exchanger in the same embodiment Plan view showing a conventional heat exchanger Sectional view showing a conventional heat exchanger

Explanation of symbols

1 Heat exchanger 2, 2x Refrigerant pipe (second pipe)
2a Double wall 3 Outer pipe 4 Inner pipe 5 Leakage detection groove 6 Water pipe (first pipe)
7 Fin 10, 11 Small diameter wire rod

Claims (9)

  A first pipe through which fluid A flows, and a second pipe through which fluid B flows, wherein the second pipe is disposed in the first pipe, The heat exchanger which formed the unevenness | corrugation in the pipe-axis direction of the said 2nd pipe | tube, or the circumferential direction on the outer surface of this pipe | tube.   The heat exchanger according to claim 1, wherein convex portions are formed on the outer surface of the second pipe so as to be spaced apart from each other in the pipe axis direction or the circumferential direction of the second pipe.   The heat exchanger according to claim 1 or 2, wherein a plate-like fin is spirally wound around the outer surface of the second tube.   The heat exchanger according to claim 1 or 2, wherein a small-diameter wire is spirally wound around the outer surface of the second tube.   A plurality of the second tubes are spirally twisted with each other, and the twisting pitch of the plurality of the second tubes is the same as that of the fins or the small-diameter wire rods spirally wound around the second tubes. The heat exchanger according to any one of claims 1 to 4, wherein the heat exchanger is gentler than the pitch.   The heat exchanger according to any one of claims 1 to 5, wherein the second pipe is a double pipe in which the outer pipe and the inner pipe are in thermal contact with each other with a gap in at least a part thereof.   The heat exchanger according to any one of claims 1 to 6, wherein the fluid A and the fluid B are opposed to each other, and the fluid B heats the fluid A through the second pipe.   The convex part provided in the outer surface of the said 2nd pipe | tube by the outflow side of the said fluid A compared with the inflow side of the said fluid A is further spaced apart in the pipe-axis direction. The heat exchanger as described in.   The heat exchanger according to any one of claims 1 to 8, wherein the fluid A is water and the fluid B is carbon dioxide.

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