JP2013079763A - Supercooler heat-transfer tube and super cooler using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercooler heat-transfer tube configured to perform predetermined heat exchange and to achieve miniaturization, and to provide a supercooler using the same.SOLUTION: The double tube-type supercooler 10 is configured as follows. A main circuit is configured by sequentially connecting a compressor, a condenser, a main expansion mechanism, and an evaporator. A double tube-type supercooler is connected between the condenser and the main expansion mechanism. A portion between the condenser and the double tube-type supercooler is connected to a suction side of the compressor and is connected to a bypass circuit with a bypass expansion mechanism connected thereto, to constitute a refrigerant circuit. The double tube-type supercooler 10 is formed of an inner tube 12 and an outer tube 13. A main-stream refrigerant 25 flows from condenser to the main expansion mechanism, in a ring-shaped gap 14 between the inner tube 12 and the outer tube 13. On the inside of the inner tube 12, a bypass-stream refrigerant 26 whose pressure is reduced by the bypass expansion mechanism of the bypass circuit, flows from the condenser, opposite the main-stream refrigerant 25. A spiral fin 15 is formed on the outer surface of the inner tube 12. A spiral groove 16 is formed on the inner surface of the inner tube 12.

Description

  The present invention relates to a double-tube supercooler incorporated in a refrigeration cycle of an air conditioner, and more particularly to a supercooler heat transfer tube used for an inner tube of the double-tube supercooler and a supercooling using the same. It is about a vessel.

  In an air conditioner, particularly a building multi-air conditioner, air conditioning of the entire building is covered by a single outdoor unit, and therefore, the refrigerant pipe connected to each indoor unit may be as long as 100 m or longer. The longer the refrigerant pipe, the lower the pressure of the refrigerant liquid flowing through it. When the saturation temperature of the refrigerant at that pressure falls to a pressure at which the refrigerant liquid temperature is equal to or lower than the temperature of the refrigerant liquid, the refrigerant liquid is vaporized by its own heat in the middle of the refrigerant pipe. In such a state, the air conditioner cannot be operated normally. In order to prevent this, it is effective to lower the temperature of the refrigerant liquid coming out of the outdoor unit. For this reason, a double-tube supercooler for cooling the refrigerant liquid is installed in the outdoor unit (Patent Document 1).

  FIG. 7 shows an air conditioner in which a double-pipe supercooler is installed in the outdoor unit shown in Patent Document 1.

  The refrigerant circuit 30 of this air conditioner is connected to an accumulator 32 on the suction side of the compressor 31 from the discharge side of the compressor 31 through a four-way valve 33 that switches between cooling and heating, and a condenser 34 and a double-pipe subcooler 35. A main circuit 38 in which a main expansion mechanism 36 and an evaporator 37 are connected in order, a branch point 39 between the condenser 34 and the double-tube supercooler 35 and a junction 40 of the accumulator 32 are connected to each other. A bypass circuit 42 is connected and configured to depressurize a part of the refrigerant 34 by the bypass expansion mechanism 41 and flow to the double-tube supercooler 35.

  The compressor 31, the accumulator 32, the four-way valve 33, the condenser 34, the double pipe supercooler 35, the main expansion mechanism 36, and the bypass expansion mechanism 41 are accommodated in the outdoor unit 43, and the evaporator 37 is connected to the indoor unit 44. The outdoor unit 43 and the indoor unit 44 are connected by refrigerant pipes 45 and 46.

  During cooling, the compressed refrigerant gas from the compressor 31 flows from the four-way valve 33 to the condenser 34 to be condensed, passes through the outer pipe 35o of the double pipe type supercooler 35, is decompressed by the main expansion mechanism 36, and is evaporated. Vaporizer 37 evaporates and returns to compressor 31 from four-way valve 33 via accumulator 32 and circulates.

  At this time, a part of the refrigerant condensed by the condenser 34 flows from the branch point 39 to the bypass circuit 42, is decompressed by the bypass expansion mechanism 41, flows to the inner pipe 35 i of the double-tube supercooler 35, and is compressed. Return to the suction side of the machine 31. As a result, the refrigerant passing through the inner pipe 35i of the double-pipe supercooler 35 cools the condensed refrigerant passing through the outer outer pipe 35o and enters a supercooled state, and the refrigerant liquid pressure drops while passing through the refrigerant pipe 45. The refrigeration capacity of the evaporator 37 is improved.

  During heating, the four-way valve 33 is switched so that the refrigerant from the compressor 31 is changed from the indoor heat exchanger (evaporator 37) to the main expansion mechanism 36, the double-pipe subcooler 35, and the outdoor heat exchanger. (Condenser 34) is circulated from the four-way valve 33 to the compressor 31 via the accumulator 32.

  As shown in FIG. 6, the double-tube supercooler 35 includes an inner tube 35i and an outer tube 35o provided concentrically so as to cover the inner tube 35i. The bypass-flow refrigerant flowing through the inner pipe 35i and the main-flow refrigerant flowing through the outer pipe 35o are configured as a counter-flow heat exchanger that flows in opposite directions across the pipe wall of the inner pipe 35i having heat conductivity.

Japanese Patent Laid-Open No. 10-054616

  By the way, a smooth tube is used as a heat transfer tube for the inner tube in the double tube type supercooler. Since the outer surface of the inner tube is smooth, the heat transfer area is small, and the mainstream refrigerant flowing outside the inner tube is not stirred. Therefore, there is a problem that the heat transfer performance between the mainstream refrigerant and the outer wall surface of the inner pipe is low.

  Therefore, in order to obtain a predetermined heat exchange, there is a problem that the double-tube supercooler must be enlarged.

  Accordingly, an object of the present invention is to solve the above-described problems, and to provide a heat exchanger tube for a subcooler that can perform predetermined heat exchange and can be downsized, and a supercooler using the same.

  In order to achieve the above object, the invention of claim 1 comprises a main circuit in which a compressor, a condenser, a main expansion mechanism, and an evaporator are sequentially connected, and a double-pipe type filter is connected between the condenser and the main expansion mechanism. Connecting a cooler, connecting a bypass circuit to which a bypass expansion mechanism is connected between the condenser and the double-tube supercooler, and connecting the suction side of the compressor to form a refrigerant circuit, The double pipe type supercooler is composed of an inner pipe and an outer pipe, and a main flow refrigerant from the condenser to the main expansion mechanism flows through an annular gap between the inner pipe and the outer pipe, and the condenser is placed inside the inner pipe. A double-tube supercooler in which a bypass-flow refrigerant decompressed by a bypass expansion mechanism of a bypass circuit is caused to flow in a counter-flow with the main-stream refrigerant, and a helical fin is provided on the outer surface of the inner pipe, A heat transfer tube for a supercooler, wherein a spiral groove is provided on the inner surface of the tube.

  In the invention of claim 2, the double pipe type supercooler is arranged vertically, the bypass flow refrigerant flows from below the inner pipe, and the main flow refrigerant is above the annular gap between the inner pipe and the outer pipe. The heat transfer tube for a subcooler according to claim 1, wherein the heat transfer tube flows downward from the bottom.

  In the invention of claim 3, the outer diameter of the inner tube is 8 to 12 mm, the height of the helical fin on the outer surface of the inner tube is 0.5 to 0.9 mm, the helical pitch is 0.4 to 0.8 mm, the inner surface The supercooling according to claim 1 or 2, wherein the helical groove has a depth of 0.1 to 0.2 mm, a twist angle of 12 to 20 °, and an outer diameter of the outer tube of 14 to 18 mm. It is a heat transfer tube.

  A fourth aspect of the present invention is a supercooler using the subcooler heat transfer tube according to any one of the first to third aspects.

  The present invention exhibits an excellent effect that the heat exchange performance of the double-tube supercooler can be improved by providing a spiral fin on the outer surface of the inner tube and providing a spiral groove on the inner surface of the inner tube. To do.

It is detailed sectional drawing which shows one Embodiment of the heat exchanger tube for supercoolers of this invention. It is sectional drawing which shows one Embodiment of the double tube | pipe supercooler using the heat exchanger tube for supercoolers of FIG. In this invention, it is the schematic of the double tube | pipe supercooler for testing the heat transfer performance of a double tube | pipe supercooler. In this invention, it is a piping diagram for testing the heat transfer performance of a double-tube supercooler. It is a figure which shows the result of having tested the heat-transfer performance of the double tube | pipe supercooler of this invention, a prior art example, and a comparative example. It is sectional drawing of the conventional double pipe type supercooler. It is a figure which shows the refrigerant circuit in which the double tube | pipe supercooler was integrated. It is a figure which shows the external appearance of the heat exchanger tube as a comparative example used when the heat transfer performance of the double tube | pipe supercooler was tested. It is a figure which shows the various dimensions of the heat exchanger tube as a comparative example shown in FIG.

  A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows a cross-sectional view of a heat transfer tube for a supercooler according to the present invention, FIG. 1 (a) is an enlarged front cross-sectional view, FIG. 1 (b) is an enlarged cross-sectional view of the main part, and FIG. These are sectional drawings of the double pipe type supercooler using the heat exchanger tube for supercoolers.

  In FIG. 1 and FIG. 2, an outer tube 13 is provided concentrically with the inner tube 12 so as to cover the outer periphery of the inner tube 12, thereby forming a double-tube supercooler 10.

  An annular gap 14 is formed between the inner tube 12 and the outer tube 13. Helical fins 15 are provided on the outer surface of the inner tube 12. A spiral groove 16 is provided on the inner surface of the inner tube 12.

  The outer diameter of the inner tube 12 is 8 to 12 mm, the height of the helical fin on the outer surface of the inner tube 12 is 0.5 to 0.9 mm, the helical pitch is 0.4 to 0.8 mm, and the helical groove on the inner surface The depth of 16 is 0.1 to 0.2 mm, the twist angle is 12 to 20 °, and the outer diameter of the outer tube 13 is 14 to 18 mm.

  The double-tube supercooler 10 is connected to the same position as the double-tube supercooler 35 of the refrigerant circuit 30 described with reference to FIG. 7 and is disposed vertically in the outdoor unit 43.

  In this double-tube supercooler 10, the bypass flow refrigerant 26 is condensed in the condenser, branches from the main flow refrigerant 25 reaching the main expansion mechanism, flows into the bypass circuit, and is depressurized by the bypass expansion mechanism. The inside of the pipe 12 flows from the bottom to the top as indicated by the arrow in the figure and evaporates, and the evaporated bypass flow refrigerant 26 flows to the suction side of the compressor via the accumulator together with the main flow refrigerant 25 evaporated by the evaporator. .

  The main flow refrigerant 25 is condensed by the condenser, flows into the annular gap 14 from the upper inlet 17, flows from the upper part to the lower part of the annular gap 14, and bypasses the bypass flow refrigerant 26 via the tube wall of the inner pipe 12. The refrigerant is converted into a supercooled refrigerant by heat exchange, and flows from the outlet 18 to the main expansion mechanism. Further, as described above, the bypass flow refrigerant 26 is evaporated by heat exchange with the main flow refrigerant 25 through the tube wall of the inner tube 12.

  The heat exchange between the main flow refrigerant 25 and the bypass flow refrigerant 26 increases the heat transfer area by the spiral fins 15 on the outer surface of the inner pipe 12, and is stirred when the main flow refrigerant 25 flows over the fins 15. The heat transfer performance between 25 and the outer wall surface of the inner tube 12 can be increased. Further, since the groove 16 is formed in the inner pipe 12, the heat transfer performance between the bypass refrigerant 26 and the inner wall surface of the inner pipe 12 can be improved.

  Therefore, the double-tube supercooler 10 that performs predetermined heat exchange can be reduced in size.

  Next, Table 1 shows the specifications of the test tubes of the inner tube and the outer tube when the cooling performance of the double tube supercoolers of the examples of the present invention, the conventional example, and the comparative example is tested.

  In Table 1, the length of the heat transfer section is the distance between the centers of the mainstream refrigerant inlet 17 and outlet 18 shown in FIG.

  The inner tube as the heat transfer tube of the conventional example in Table 1 was a smooth tube, and the inner tube as the heat transfer tube of the comparative example was the one shown in FIG. In addition to a shape in which a spiral concave portion is formed on the outer peripheral surface of the tube and a spiral convex portion is formed on the corresponding inner peripheral surface (that is, a corrugated shape), The fin shape similar to that of the present invention is formed.

  FIG. 9 shows a cross-sectional configuration of the comparative example in which fins are provided in the corrugated shape, and various dimensions shown in Table 1 are shown in FIG. Since the inner tube of this comparative example has an outer diameter of 14 mm, the outer tube is larger than the inner tube of the present invention and the conventional example. Used was 19.05 mm.

  Using the test tubes shown in Table 1, as shown in FIG. 3, the inner tube 12 and the outer tube 13 are arranged vertically, and the wet steam of the R410A refrigerant is used as a bypass flow refrigerant from the lower portion of the inner tube 12. The refrigerant liquid of R410A refrigerant was flowed as the main refrigerant from above to below the annular gap 14 between the pipe 12 and the outer pipe 13. The conventional example was also flowed in the same state. Further, the temperature, pressure, and flow rate of each refrigerant at that time were measured with a thermometer T, a pressure gauge P, and a flow meter F connected to each pipe as shown in FIG.

  Inside the inner pipe, a low-temperature and low-pressure refrigerant wet steam adjusted to a predetermined temperature, pressure and quality was flowed. The flow rate was adjusted by the expansion valve 27 so as to achieve a predetermined outlet superheat degree (5K). A high-temperature and high-pressure refrigerant liquid adjusted to a predetermined temperature (44.9 ° C.) was passed through the annular gap.

  Table 2 shows the experimental conditions.

  Although there are no standards for the test conditions of the subcooler for multi air conditioners for buildings, it is generally considered from the air conditioner cycle. The condition of the annular gap flow rate of 363 kg / h assumes the rated operation state of the subcooler.

  FIG. 5 shows the relationship between the refrigerant flow rate and the heat exchange amount when the refrigerant flow rate is changed and the refrigerant flow rate and the heat exchange amount are measured. In FIG. A square is a comparative example.

  However, in the case of the example, since the capability exceeds the measurable range of the experimental apparatus, the flow rate of the annular gap is set to 288 kg / h or less.

  As shown in FIG. 5, in the conventional example, the heat exchange amount is 0.5 kW or less even if the refrigerant flow rate is changed, but in the example, it was confirmed that the heat exchange amount increases as the refrigerant flow rate increases. . Moreover, although the comparative example is what provided the fin in the corrugated shape, the result in which the heat exchange amount of the Example was higher was obtained. It is considered that this is because the heat exchange performance can be improved more than the corrugated shape by forming a spiral groove on the inner surface of the inner tube.

  Although the outer pipe | tube of an Example is smaller than the outer diameter of a comparative example, this does not give doubt to the performance of this invention. This is because, when attempting to reduce the weight and reduce the thickness, the pressure resistance requirement is reduced at the same flow rate, so the wall thickness can be reduced, but if the performance per unit area in the cross section is the same, the transmission of the small diameter is reduced. This is because the total cross-sectional area of the heat pipe is smaller, and the performance is usually lowered.

  The performance of the examples is improved under the same flow rate despite the small diameter, and the effect of the present invention is clear.

10 Double tube type supercooler 12 Inner tube 13 Outer tube 14 Annular gap 15 Fin 16 Groove

Claims (4)

  A main circuit is formed by connecting a compressor, a condenser, a main expansion mechanism, and an evaporator in sequence, and a double-tube supercooler is connected between the condenser and the main expansion mechanism. A refrigerant circuit is configured by connecting a bypass circuit to which a bypass expansion mechanism is connected between the cooler and the suction side of the compressor, and the double-tube supercooler includes an inner tube and an outer tube. A bypass flow refrigerant configured to flow a main flow refrigerant from the condenser to the main expansion mechanism through an annular gap between the inner pipe and the outer pipe and decompressed from the condenser by a bypass expansion mechanism of a bypass circuit inside the inner pipe In the double-tube supercooler in which the main flow refrigerant flows in a counter flow, a spiral fin is provided on the outer surface of the inner tube, and a spiral groove is provided on the inner surface of the inner tube. Heat transfer tube for supercooler.   The double pipe type supercooler is arranged vertically, so that the bypass flow refrigerant flows from the bottom to the top of the inner pipe, and the main flow refrigerant flows from the top to the bottom of the annular gap between the inner pipe and the outer pipe. The heat exchanger tube for a supercooler according to claim 1.   The outer diameter of the inner tube is 8-12mm, the height of the helical fin on the outer surface of the inner tube is 0.5-0.9mm, the helical pitch is 0.4-0.8mm, the depth of the helical groove on the inner surface The heat transfer tube for a supercooler according to claim 1 or 2, wherein the length is 0.1 to 0.2 mm, the twist angle is 12 to 20 °, and the outer diameter of the outer tube is 14 to 18 mm.   A supercooler using the heat transfer tube for a supercooler according to any one of claims 1 to 3.