JP2010014311A - Supercooler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact supercooler by providing the outer surface of a heat transfer tube with a groove. <P>SOLUTION: The supercooler 9 is used for an air conditioner 1 constituted by connecting a compressor 2, a condenser 3, a main expansion mechanism 4 and an evaporator 5 sequentially to constitute a refrigerant circuit 8, connecting the supercooler 9 formed of a double tube between the condenser 3 and the main expansion mechanism 4 to allow a condensed refrigerant 11 from the condenser 3 to the main expansion mechanism 4 to flow through an outer tube 12 of the supercooler 9, and connecting a by-pass circuit 13 to a heat transfer tube 10 inside the supercooler 9. The by-pass circuit reduces the pressure of the condensed refrigerant 11 from the condenser 3 to flow to the heat transfer tube 10 and returns the condensed refrigerant to the compressor 2 side, and the outer surface of the heat transfer tube 10 has the groove 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a double-tube supercooler used in an air conditioner.

  The thing of patent document 1 is known as a refrigerant circuit of an air conditioner. As shown in FIG. 3, the refrigerant circuit 8 is configured to convert the refrigerant from the compressor 2 into a condenser 3, a double-tube supercooler 20, a main expansion mechanism 4, an evaporator 5, a four-way switching valve 6, and The main circuit 21 that flows in the order of the accumulator 7, the main circuit 21 branches between the condenser 3 and the subcooler 20, passes through the bypass expansion mechanism 14 and the subcooler 20, and is connected to the four-way switching valve 6 and the accumulator 7. And a bypass circuit 13 that merges with the main circuit 21 therebetween. The refrigerant discharged from the compressor 2 is condensed by, for example, the condenser 3 that radiates heat to outdoor air, and then branched into the main circuit 21 and the bypass circuit 13. The bypass flow refrigerant flowing in the bypass circuit 13 is decompressed by the bypass expansion mechanism 14 and then flows to the subcooler 20, and the main flow refrigerant flowing in the main circuit 21 flows to the subcooler 20 as well as the bypass flow refrigerant and heat. It is replaced and supercooled.

  The supercooler 20 is formed in a double tubular shape having a heat transfer tube and an outer tube provided concentrically on the outer side of the heat transfer tube, and allows the main refrigerant to flow between the outer tube and the heat transfer tube, A bypass flow refrigerant is allowed to flow in the heat transfer tube. The supercooler is composed of a counter-flow heat exchanger, and is set so that the main-flow refrigerant and the bypass-flow refrigerant flow in directions opposite to each other across the tube wall of the heat transfer tube having heat transfer properties. Further, the heat transfer tube and the outer tube are smooth tubes.

Japanese Patent Laid-Open No. 10-054616

  By the way, since the outer surface of the heat transfer tube is smooth, the heat transfer area for the mainstream refrigerant is small and the heat transfer coefficient is also low. Therefore, in order to perform predetermined heat exchange, the subject that the subcooler had to be enlarged occurred.

  Then, the objective of this invention is solving the said subject and providing a compact supercooler.

  In order to solve the above problems, the present invention forms a refrigerant circuit by sequentially connecting a compressor, a condenser, a main expansion mechanism, and an evaporator, and a supercooling comprising a double pipe between the condenser and the main expansion mechanism. Connect the condenser, flow the condensed refrigerant from the condenser to the main expansion mechanism through the outer pipe of the supercooler, depressurize the condensed refrigerant from the condenser to the heat transfer pipe inside the supercooler, and flow it to the heat transfer pipe In addition, the subcooler is used in an air conditioner connected to a bypass circuit that returns to the compressor side, and a groove is provided on the outer surface of the heat transfer tube.

  This groove increases the heat transfer area for the mainstream refrigerant. This groove stirs the mainstream refrigerant and increases the heat transfer coefficient. Therefore, the supercooler for performing predetermined heat exchange can be made small.

  The groove may be a spiral groove.

  The heat transfer tube may be made of copper.

  According to the present invention, the supercooler can be made compact.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 3, the air conditioner 1 includes a refrigerant circuit (main circuit) 8 that sequentially connects a compressor 2, a condenser 3, a main expansion mechanism 4, an evaporator 5, a four-way switching valve 6, and an accumulator 7. Prepare. The four-way switching valve 6 is connected between the discharge side of the compressor 2 and the inflow side of the accumulator 7, and the refrigerant discharged from the compressor 2 by switching is either the condenser 3 or the evaporator 5. It is configured to flow in one side and allow refrigerant to flow in from the other.

  As shown in FIGS. 2 and 3, a supercooler 9 composed of a double pipe is connected between the condenser 3 and the main expansion mechanism 4, and a condenser is connected to an outer pipe 12 of the supercooler 9. Condensed refrigerant (mainstream refrigerant) 11 from 3 to the main expansion mechanism 4 is flowed, and the condensed refrigerant 11 from the condenser 3 is depressurized and flows to the heat transfer pipe 10 in the heat transfer pipe 10 inside the subcooler 9. A bypass circuit 13 returning to the compressor 2 side is connected. The bypass circuit 13 is connected to the heat transfer tube 10 so that the flow direction of the condensed fluid 11 is reversed between the outer tube 12 and the heat transfer tube 10. A bypass expansion mechanism 14 is connected to the bypass circuit 13 upstream of the heat transfer tube 10. The subcooler 9 includes a heat transfer tube 10 that forms a flow path for the bypass flow refrigerant 15 and an outer tube that is provided concentrically outside the heat transfer tube 10 and forms a flow path for the condensed refrigerant 11 between the heat transfer tube 10. 12 and is configured such that heat exchange between the bypass refrigerant 15 and the condensed refrigerant 11 is performed via the tube wall 16 of the heat transfer tube 10.

  As shown in FIGS. 1A and 1B, the heat transfer tube 10 is made of copper, and a spiral groove 17 for increasing heat transfer efficiency is provided on the outer surface of the heat transfer tube 10. The spiral groove 17 increases the heat transfer area with the condensed refrigerant 11 on the outer surface of the heat transfer tube 10. Further, since the condensed refrigerant 11 is agitated by the spiral groove 17, the heat transfer coefficient between the outer surface of the heat transfer tube 10 and the condensed refrigerant 11 is increased. For this reason, the efficiency of heat exchange between the bypass refrigerant 15 and the condensed refrigerant 11 is increased, and the supercooler 9 for performing predetermined heat exchange can be reduced.

  Next, the point which can make the supercooler 9 small by using the heat exchanger tube 10 which has the above-mentioned spiral groove 17 is demonstrated using a type | formula.

  The ratio of the length of the supercooler between the case where the spiral groove 17 is provided on the outer surface of the heat transfer tube and the case where the outer surface of the heat transfer tube is smooth as in the prior art is expressed by Equation 1.

Where d _c is the inner diameter of the heat transfer tube, d _h is the outer diameter of the heat transfer tube, α _c is the heat transfer coefficient in the tube of the heat transfer tube, α _h is the heat transfer coefficient outside the tube of the heat transfer tube, and 1 is the length of the subcooler The subscript 1 represents a smooth heat transfer tube, and the subscript 2 represents a heat transfer tube having a spiral groove 17.

  The external heat transfer coefficient of the heat transfer tube having a smooth outer surface is given by Equation 2.

Here, D is the inner diameter of the outer tube, D _e is hydraulic equivalent diameter of the annular gap between the heat transfer tube and the outer tube, f is the pipe friction factor, Re is Reynolds number, Pr is Prandtl number, v is the flow velocity, lambda is the thermal Conductivity, ν is kinematic viscosity.

  It is assumed that the heat transfer coefficient outside the tube having the spiral groove 17 on the outer surface is given by Equation 3.

  Here, h is the depth of the groove 17, p is the pitch in the tube axis direction of the groove 17, and β is the twist angle of the groove 17.

  Next, the effect of the spiral groove 17 on the outer surface of the heat transfer tube is calculated under the actual conditions shown in Table 1.

  The result of Formula 4 was obtained by calculation under this condition.

  That is, by providing the spiral groove 17 on the outer surface of the heat transfer tube, the length of the supercooler can be shortened by about 44%.

  In addition, when calculating with h = 0.2 under the above conditions, the length ratio of the heat transfer tubes is

When calculating with h = 1.0, the length ratio of the heat transfer tubes is

It is.

  Furthermore, when calculating with β = 40 (p = 1.81), the length ratio of the heat transfer tubes is

When calculating with β = 60 (p = 0.875), the length ratio of the heat transfer tubes is

It is.

  Thus, by providing the groove 17 on the outer surface of the heat transfer tube 10 of the supercooler 9 used in the air conditioner 1, the length of the supercooler 9 can be shortened, the supercooler 9 can be made compact, The harmony machine 1 can be made compact.

  Since the groove 17 is spiral, it can be satisfactorily stirred without forming stagnation in the condensed refrigerant 11 and can be easily processed.

  Since the heat transfer tube 10 is made of copper, heat exchange between the refrigerants 11 and 15 can be performed efficiently.

(A) is principal part side sectional drawing of the subcooler which shows suitable embodiment of this invention, (b) is front sectional drawing. It is a sectional side view of a supercooler. It is a refrigerant circuit diagram of an air conditioner in which a supercooler is used.

Explanation of symbols

1 Air Conditioner 2 Compressor 3 Condenser 4 Main Expansion Mechanism 5 Evaporator 8 Refrigerant Circuit 9 Supercooler 10 Heat Transfer Tube 11 Condensed Refrigerant 12 Outer Tube 13 Bypass Circuit 17 Groove

Claims (3)

  A compressor circuit, a condenser, a main expansion mechanism, and an evaporator are connected in order to form a refrigerant circuit. A double-tube supercooler is connected between the condenser and the main expansion mechanism. Condensed refrigerant from the condenser to the main expansion mechanism flows through the pipe, and a bypass circuit is connected to the heat transfer pipe inside the subcooler to reduce the condensed refrigerant from the condenser and flow it to the heat transfer pipe and return it to the compressor side A supercooler used for an air conditioner, wherein a groove is provided on an outer surface of the heat transfer tube.   The supercooler according to claim 1, wherein the groove is a spiral groove.   The supercooler according to claim 1 or 2, wherein the heat transfer tube is made of copper.

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