Air conditioner and method for manufacturing heat exchanger

Abstract

To prevent refrigerant leakage.SOLUTION: An air conditioner comprises a heat exchanger having a heat transfer tube, where the heat transfer tube has an inner tube through which refrigerant flows, and an outer tube provided radially outside the inner tube, a portion of the outer tube is in contact with the inner tube, and an outer groove is formed between the outer tube and the inner tube to allow leaked refrigerant to flow.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an air conditioner and a method for manufacturing a heat exchanger. [Background technology]

[0002] The HFC refrigerants used in air conditioners have a high global warming potential, and it has been decided that they will be gradually reduced in order to prevent global warming. As a next-generation refrigerant, propane refrigerant is a candidate because it has a low global warming potential and is highly efficient. However, propane is flammable, and therefore there is a safety issue when it leaks indoors. To solve this problem, Patent Document 1 discloses an air conditioner that includes a cover that covers refrigerant that has leaked due to poor welding of heat transfer tubes of a heat exchanger, and an exhaust flow path for exhausting the refrigerant inside the cover. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-292066 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, refrigerant leakage is not limited to welded parts. Refrigerant leakage caused by defects or corrosion of heat transfer tubes is also a problem.

[0005] The present invention has been made in consideration of such problems, and has an object to prevent refrigerant leakage. [Means for solving the problem]

[0006] The present invention is an air conditioner comprising a heat exchanger having a heat transfer tube, the heat transfer tube having an inner tube through which a refrigerant flows and an outer tube provided radially outside the inner tube, a portion of the outer tube being in contact with the inner tube, and an outer groove being formed between the outer tube and the inner tube to allow leaked refrigerant to flow. Effect of the Invention

[0007] According to the present invention, refrigerant leakage can be prevented. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is an external configuration diagram of the air conditioner. [Diagram 2] FIG. 2 is a diagram showing a refrigerant circuit. [Diagram 3] FIG. 2 is a schematic diagram illustrating the internal configuration of an indoor heat exchanger. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 13 is a diagram showing the relationship between the bonding ratio and the heat transfer ratio. [Figure 8] FIG. 13 is a graph showing the relationship between the bonding ratio and the heat transfer coefficient ratio. [Figure 9] FIG. 4 is an explanatory diagram of a manufacturing method of a heat transfer tube. [Figure 10] FIG. 6 is a schematic configuration diagram of a heat transfer tube according to a second embodiment. [Figure 11] FIG. 11 is an external view of an indoor unit according to a second embodiment. [Figure 12] 6A to 6C are explanatory diagrams of a method for manufacturing a heat exchanger according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (First embodiment) Fig. 1 is an external configuration diagram showing an air conditioner 1 according to an embodiment. The air conditioner 1 performs air conditioning by circulating a refrigerant in a refrigeration cycle (heat pump cycle). As shown in Fig. 1, the air conditioner 1 includes an indoor unit 10 installed indoors (conditioned space), an outdoor unit 20 installed outdoors (outdoors), and a remote control 30 operated by a user.

[0010] The indoor unit 10 includes a remote control communication unit 11. The remote control communication unit 11 receives a signal from the remote control 30 by infrared communication or the like. The remote control communication unit 11 may also transmit a predetermined signal to the remote control 30. For example, the remote control communication unit 11 receives signals such as an on / off command, a change in the set temperature, a change in the operation mode, and a timer setting from the remote control 30. The remote control communication unit 11 may also transmit a detected value of the indoor temperature to the remote control 30. Although omitted in FIG. 1, the indoor unit 10 and the outdoor unit 20 are connected via a refrigerant pipe and also via a communication line.

[0011] Fig. 2 is a diagram showing a refrigerant circuit Q of the air conditioner 1 according to the embodiment. Note that the solid arrows shown in Fig. 2 indicate the flow of the refrigerant during heating operation. Also, the dashed arrows shown in Fig. 2 indicate the flow of the refrigerant during cooling operation.

[0012] The indoor unit 10 includes an indoor heat exchanger 12 and an indoor fan 13 in addition to the remote control communication unit 11. In the indoor heat exchanger 12, heat exchange occurs between the refrigerant flowing through its heat transfer tube and the indoor air sent in by the indoor fan 13. The indoor heat exchanger 12 operates as a condenser or an evaporator by switching a four-way valve 25 described below. The indoor fan 13 is installed near the indoor heat exchanger 12. The indoor fan 13 sends indoor air to the indoor heat exchanger 12.

[0013] The outdoor unit 20 includes a compressor 21, an outdoor heat exchanger 22, an outdoor fan 23, an expansion valve 24, and a four-way valve 25. The compressor 21 compresses a low-temperature, low-pressure gas refrigerant and discharges it as a high-temperature, high-pressure gas refrigerant. In the outdoor heat exchanger 22, heat exchange occurs between the refrigerant flowing through its heat transfer tube and outside air sent in by the outdoor fan 23. The outdoor heat exchanger 22 operates as a condenser or an evaporator by switching the four-way valve 25.

[0014] As shown in Fig. 1, the outdoor fan 23 is installed near the outdoor heat exchanger 22. Outside air is sent to the outdoor heat exchanger 22 by the outdoor fan 23. The expansion valve 24 has a function of reducing the pressure of the refrigerant condensed in the "condenser" (one of the outdoor heat exchanger 22 and the indoor heat exchanger 12). The refrigerant reduced in pressure in the expansion valve 24 is guided to the "evaporator" (the other of the outdoor heat exchanger 22 and the indoor heat exchanger 12). The four-way valve 25 is a valve that switches the flow path of the refrigerant depending on the operation mode of the air conditioner 1.

[0015] 3 is a schematic diagram of the inside of the indoor heat exchanger 12. The indoor heat exchanger 12 has a heat transfer tube 15 and fins 16. The heat transfer tube 15 is a serpentine tube in which tubes are connected via a U-bend. A plurality of fins 16 are connected to the periphery of the heat transfer tube 15. The plurality of fins 16 are arranged at equal intervals along the longitudinal direction of the heat transfer tube 15.

[0016] Furthermore, in this embodiment, the heat transfer tube 15 is provided with a double tube. Fig. 4 is a cross-sectional view of the heat transfer tube 15. The heat transfer tube 15 has an inner tube 151 and an outer tube 152. The outer tube 152 is provided on the radial outside of the inner tube 151, i.e., around the inner tube 151. Fig. 5 is a development view of the inner wall of the inner tube 151. Fig. 6 is a development view of the inner wall of the outer tube 152. Arrow A indicates the axial direction of the heat transfer tube 15, i.e., the direction in which the refrigerant flows.

[0017] As shown in FIG. 5, the inner pipe 151 is formed with a plurality of inner grooves 1511 for increasing the contact area between the refrigerant and the wall. The inner grooves 1511 extend along a direction inclined from the axial direction A. As shown in FIG. 6, the outer pipe 152 is formed with a plurality of outer grooves 1521 for flowing the leaked refrigerant leaked from the inner pipe 151. As shown in FIG. 4, the convex surface 1522 provided between the outer grooves 1521 is joined to the outer wall of the inner pipe 151. As shown in FIG. 6, the outer grooves 1521 extend along the axial direction A. Since it is the leaked refrigerant that flows through the outer grooves 1521, it is desirable that it be discharged quickly. Therefore, the outer grooves 1521 are formed in parallel to the axial direction A. In this way, the outer pipe 152 is formed so as to cover the inner pipe 151, and the outer pipe 152 is formed with the outer grooves 1521 that serve as a flow path for leading the leaked refrigerant to the discharge port.

[0018] 3, the outer pipe 152 is formed to extend to the outside of the room, and the two ends 1522a, 1522b of the outer pipe 152 are disposed outside of the room, and the leaking refrigerant is discharged to the outside of the room at the ends 1522a, 1522b. That is, the ends 1522a, 1522b function as an outlet for the leaking refrigerant.

[0019] In this way, the heat transfer tube 15 is provided in a double layer, and the leaking refrigerant flows through the outer tube 152 and is discharged to the outside. Therefore, even if the refrigerant leaks due to a defect or corrosion of the inner tube 151, the refrigerant can be prevented from leaking into the room.

[0020] The number and width of the outer grooves 1521 arranged along the circumference of the outer pipe 152 are not particularly limited. However, the joining ratio (joining rate) is preferably 80% or less. Here, the joining ratio is the ratio of the area (range of the convex surface 1522) where the outer pipe 152 contacts the entire circumference of the outer wall of the inner pipe 151. If the joining ratio is too high, a flow path for the leaking refrigerant cannot be secured. Therefore, by setting the joining ratio to 80% or less, a flow path for the leaking refrigerant can be secured.

[0021] Furthermore, the joining ratio is preferably 33% or more. This point will be explained. FIG. 7 is a diagram showing the relationship between the joining ratio and the overall heat transfer ratio. FIG. 8 is a diagram showing a graph of the joining ratio and the overall heat transfer ratio. The graph shown in FIG. 8 corresponds to the table shown in FIG. 7. The horizontal axis of the graph indicates the joining ratio, and the vertical axis indicates the overall heat transfer ratio. Here, the overall heat transfer ratio is the ratio of the overall heat transfer ratio when the outer tube 152 is joined to the outer periphery of the inner tube 151 at each joining ratio, and is the ratio when the overall heat transfer ratio when the outer tube 152 is joined to the entire circumference of the outer wall of the inner tube 151 is set to 100%. The overall heat transfer ratio is defined by (Equation 1). The table in FIG. 7 and the graph in FIG. 8 show the ratio of the overall heat transfer ratio defined by (Equation 1) obtained by simulation by changing the joining ratio.

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[0022] Fig. 9 is an explanatory diagram of a manufacturing method of a double-tube heat transfer tube 15. First, as shown in the upper part of Fig. 9, an inner tube 151 having an inner groove 1511 formed therein is inserted into an outer tube 152 having an outer groove 1521 formed therein. Next, as shown in the lower part of Fig. 9, pressure is applied from the inside of the inner tube 151 to expand the inner tube 151. This allows the outer wall of the inner tube 151 to be tightly attached to the inner wall (convex portion) of the inner tube 151.

[0023] Second embodiment Next, the heat transfer tube 15 according to the second embodiment will be described mainly with respect to differences from the heat transfer tube 15 according to the first embodiment. FIG. 10 is a schematic diagram of the heat transfer tube 15 according to the second embodiment. The heat transfer tube 15 according to this embodiment includes a plurality of hairpin pipes 153 and a return pipe 154 that connects two adjacent hairpin pipes 153. Here, the hairpin pipes 153 and the return pipe 154 are examples of a bent portion and a connecting portion, respectively. The hairpin pipe 153 has a double structure including an inner pipe 151 and an outer pipe 152, similar to the heat transfer tube 15 according to the first embodiment. On the other hand, the return pipe 154 is a single pipe and is connected to the inner pipe 151 of the hairpin pipe 153. Therefore, at the end of the hairpin pipe 153, the leaking refrigerant flows out from the end 1523 of the outer pipe 152. Therefore, in order to prevent the leaking refrigerant from leaking into the room, a cover unit 17 is provided to cover the end 1523 of the outer pipe 152.

[0024] Fig. 11 is an external view of an indoor unit 10 according to a second embodiment. The diagram on the left side of Fig. 11 is a diagram of the indoor unit 10 viewed from the front, and the diagram on the right side of Fig. 11 is a diagram of the indoor unit 10 viewed from the right side. As described above, the cover unit 17 is disposed on the right side of the main body of the indoor unit 10, and an exhaust pipe 18 extends from the cover unit 17 to the outside of the room. Leaked refrigerant accumulated inside the cover unit 17 is exhausted to the outside of the room through the exhaust pipe 18.

[0025] Fig. 12 is an explanatory diagram of a manufacturing method of the indoor heat exchanger 12 according to the second embodiment. With the hairpin pipe 153 passing through a through hole (not shown) provided in the fin 16, a plug 200 for expanding the tube is inserted into the inner tube 151 as shown in Fig. 12. This makes it possible to simultaneously carry out the step of bringing the inner tube 151 and the outer tube 152 into close contact with each other and the step of bringing the outer wall of the outer tube 152 into close contact with the fin 16.

[0026] It should be noted that the present invention is not limited to the specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims, for example, by applying a modified example of one embodiment to another embodiment.

[0027] As such a modified example, the outdoor heat exchanger 22 may also have a double structure in which the heat transfer tube has an inner tube and an outer tube, similar to the indoor heat exchanger 12. [Explanation of symbols]

[0028] 1. Air conditioner 10 Indoor unit 11 Remote control communication unit 12 Indoor heat exchanger 13 Indoor fan 15 Heat transfer tube 16 Finn 17 Cover unit 18 Discharge pipe 20 Outdoor unit 21 Compressor 22 Outdoor heat exchanger 23 Outdoor fan 24 Expansion valve 25 Four-way valve 151 Inner tube 152 Outer tube 153 Hairpin Pipe 154 Return pipe 1511 Inner Ditch 1521 Outer ditch 1522a, 1522b end

Claims

1. An air conditioner, A heat exchanger having a heat transfer tube, The heat transfer tube is an inner pipe through which a refrigerant flows; an outer tube provided radially outside the inner tube; having A portion of the outer tube is in contact with the inner tube, An outer groove for allowing leaked refrigerant to flow is formed between the outer pipe and the inner pipe.

2. The air conditioner according to claim 1 , wherein the outer groove is formed parallel to an axial direction of the heat transfer tube.

3. The heat exchanger includes: A plurality of the heat transfer tubes are provided, The heat transfer tube has a bent portion, an end of the outer tube is provided at a position corresponding to a connection portion that connects the heat transfer tubes to each other; a cover for covering the end of the outer tube; The air conditioner according to claim 1 , wherein the cover is connected to a discharge pipe that discharges the refrigerant to the outside of the room.

4. The air conditioner according to claim 1 , wherein a joining rate at which the inner pipe and the outer pipe are in contact with each other is 33% or more.

5. The air conditioner according to claim 1 , wherein a joining rate at which the inner pipe and the outer pipe are in contact with each other is 80% or less.

6. A method for manufacturing a heat exchanger having a heat transfer tube, comprising the steps of: providing an outer pipe radially outside an inner pipe through which a refrigerant flows; expanding the inner tube to bring the inner tube into contact with the outer tube and to fix the outer tube to a fin; A method for manufacturing a heat exchanger, comprising:

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