EP3770535A1

EP3770535A1 - Heat exchanger, refrigeration cycle device, and air conditioning device

Info

Publication number: EP3770535A1
Application number: EP18911206.3A
Authority: EP
Inventors: Yuki UGAJIN
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2018-03-20
Filing date: 2018-03-20
Publication date: 2021-01-27
Also published as: EP3770535A4; WO2019180817A1; CN111886459A; JPWO2019180817A1; JP6925508B2

Abstract

A heat exchanger according to the present disclosure includes: heat transfer tubes each of which allow fluid to flow therethrough and has an inner surface provided with grooves that are recessed parts spirally extending in a direction of a tube axis of each heat transfer tube; and heat exchanger bodies including fins that are in contact with the heat transfer tubes to promote heat exchange of the fluid. In the case where of the heat transfer tubes, heat transfer tubes that allow the fluid to flow from an inlet of the heat exchanger to an outlet of the heat exchanger have a flow passage length L of 10 m or less, the grooves of the inner surface of each of those heat transfer tubes are formed such that a lead angle θ between the tube axis and an extending direction of the grooves falls within a range of 25 degrees to 45 degrees, and in the case where the heat transfer tubes that allow the fluid to flow from the inlet of the heat exchanger to the outlet of the heat exchanger have a flow passage length L of greater than 10 m, the grooves of the inner surface of each of those heat transfer tubes are formed such that the lead angle θ is 5 degrees or more and less than 25 degrees.

Description

Technical Field

The present disclosure relates to a heat exchanger for heat exchange, a refrigeration cycle apparatus, and an air-conditioning apparatus. More specifically, the present disclosure relates to a heat exchanger that includes a heat transfer tube having an inner surface provided with grooves.

Background Art

In an existing heat exchanger for use in a refrigeration cycle apparatus such as a refrigeration apparatus, an air-conditioning apparatus, or a heat pump, in general, heat transfer tubes each having an inner surface provided with grooves are provided to extend through through-holes formed in fins arranged at predetermined intervals. The heat transfer tubes serve as part of a refrigerant circuit in the refrigeration cycle apparatus, and fluid, such as refrigerant, flows in the heat transfer tubes. The following description is made on the premise that the fluid is refrigerant.
The refrigerant that flows in such heat transfer tubes as described above exchanges heat with, for example, air that flows outside the transfer pipes to change in phase (condense or evaporate). In order to efficiently change the phase of the refrigerant, grooves are formed based on set parameters, and the heat transfer performance of the heat transfer tubes is improved by an increase in a surface area in the pipes, an effect of string fluid with grooves, and an effect of holding a liquid film between the grooves because of capillary action (see, for example, Patent Literature 1).

Citation List

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2004-301495

Summary of Invention

Technical Problem

However, the grooves of the heat transfer tube described in Patent Literature 1 are not shaped in accordance a flow passage of the heat transfer tube. It is therefore likely that in a heat exchanger, heat exchanger bodies are mounted at a high density, the performance of the heat transfer tube will be reduced.
The present disclosure is applied to solve the above problem, and relates to a heat exchanger, a refrigeration cycle apparatus, and an air-conditioning apparatus that are formed suitable for flow passages of heat transfer tubes.

Solution to Problem

A heat exchanger according to an embodiment of the present disclosure includes heat transfer tubes each of which allow fluid to flow therethrough and has an inner surface provided with grooves that are recessed parts spirally extending in a direction along a tube axis of each heat transfer tube; and heat exchanger bodies including fins that are in contact with the heat transfer tubes to promote heat exchange of the fluid. In the case where of the heat transfer tubes, heat transfer tubes that allow the fluid to flow from an inlet of the heat exchanger to an outlet of the heat exchanger have a flow passage length L of 10 m or less, the grooves of the inner surface of each of those heat transfer tubes are formed such that a lead angle θ between the tube axis and an extending direction of the grooves falls within a range of 25 degrees to 45 degrees, and in the case where the heat transfer tubes that allow the fluid to flow from the inlet of the heat exchanger to the outlet of the heat exchanger have a flow passage length L of greater than 10 m, the grooves of the inner surface of each of those heat transfer tubes are formed such that the lead angle θ is 5 degrees or more and less than 25 degrees. Advantageous Effects of Invention
In the heat exchanger according to the embodiment of the present disclosure, grooves are formed such that the lead angle is set to a value that varies in accordance with the flow passage length L from the inlet of the heat exchanger to the outlet of the heat exchanger. Thus, the heat exchanger is formed suitable for the length of a flow passage. It is therefore possible to increase heat exchange efficiency and increase an annual performance factor (APF) of an air-conditioning apparatus. Brief Description of Drawings

[Fig. 1] Fig. 1 schematically illustrates a configuration of a heat exchanger 1 according to Embodiment 1 of the present disclosure.
[Fig. 2] Fig. 2 schematically illustrates a configuration of a heat exchanger body 10 according to Embodiment 1 of the present disclosure.
[Fig. 3] Fig. 3 is a view for explaining an inner surface of part of a heat transfer tube 12 that extends in a direction parallel to a tube axis n the heat exchanger 1 according to Embodiment 1 of the present disclosure.
[Fig. 4] Fig. 4 is a view for explaining an inner surface of part of the heat transfer tube 12 that extends in a direction perpendicular to the tube axis in the heat exchanger 1 according to Embodiment 1 of the present disclosure.
[Fig. 5] Fig. 5 illustrates a correlation between a lead angle θ at the heat transfer tube 12 and the performance of the heat transfer tube 12 according to Embodiment 1 of the present disclosure.
[Fig. 6] Fig. 6 schematically illustrates a correlation between the lead angle θ at the heat transfer tube 12 and an APF according to Embodiment 1 of the present disclosure.
[Fig. 7] Fig. 7 indicates a correlation between a groove height h of the heat transfer tube 12 and the performance of the heat transfer tube 12 according to Embodiment 2 of the present disclosure.
[Fig. 8] Fig. 8 schematically indicates a correlation between the groove height h of the heat transfer tube 12 and the APF in Embodiment 2 of the present disclosure.
[Fig. 9] Fig. 9 illustrates a configuration of a refrigeration cycle apparatus according to Embodiment 3 of the present disclosure.

Description of Embodiments

A heat exchanger and other components according to embodiments of the present disclosure will be described with reference to the accompanying drawings. In each of the figures in the drawings, components which are the same as or equivalent to those in a previous figure are denoted by the same reference signs. The same is true of the entire text of the "Description of Embodiments" section. Also, in the figures, relationships in size between components may be different from actual relationships between the components. The configurations of the components are described by way of example in the entire specification, and are not limited to those described in the specification. In particular, in the case where components are combined, it is not limited to the case where components according to the same embodiment are combined. A component in an embodiment can be applied to another embodiment as appropriate. Also, the levels of temperature, pressure, etc., are not determined in relation to absolute values, that is, they are relatively determined in accordance with the state and operation of the apparatus, for example. In addition, with respect to a plurality of components that are of the same type and distinguished from each other by suffixes, in the case where they do not particularly need to be identified or distinguished from each other, the suffixes may be omitted.

Embodiment 1

Fig. 1 schematically illustrates a configuration of a heat exchanger 1 according to Embodiment 1 of the present disclosure. Referring to Fig. 1, the heat exchanger 1 is a fin-tube heat exchanger that includes a plurality of heat exchanger bodies 10 and a flow passage pipe 20. As described later, refrigerant that flows from a heat exchanger inlet 1A passes through heat transfer tubes 12 in each of the heat exchanger bodies 10 and exchanges heat with air that flows between fins 11. The refrigerant that has exchanged heat with the air flows out from a heat exchanger outlet 1B. The flow passage pipe 20 connects the plurality of heat exchanger bodies 10 and serve as a flow passage through which refrigerant flows. The flow passage pipe 20 has branches such as a single pipe, a T pipe, and a bulge three-way pipe.
Fig. 2 schematically illustrates a configuration of a heat exchanger body 10 according to Embodiment 1 of the present disclosure. The heat exchanger body 10 includes a plurality of fins 11 and a plurality of heat transfer tubes 12. The fins 11 are substantially rectangular plate-like fins that are arranged at regular intervals. The fins 11 have through-holes that are formed such that the heat transfer tubes 12 inserted through the through-holes intersect the fins 11 in contact with the fins 12. As described later, the heat transfer tubes 12 are part of a flow passage in a refrigerant circuit of a refrigeration cycle apparatus, and refrigerant flows in the heat transfer tubes 12. The fins 11 receive heat of refrigerant that flows in the heat transfer tubes 12 and heat of air that flows outside the heat transfer tubes 12. Because of provision of the fins 11, a heat transfer area is increased, and heat exchange is efficiently performed between the refrigerant and the air.
Fig. 3 is a view for explaining an inner surface of part of a heat transfer tube 12 that extends in a direction parallel to a tube axis 15 in the heat exchanger 1 according to Embodiment 1 of the present disclosure. Fig. 4 is a view for explaining an inner surface of part of the heat transfer tube 12 that extends in a direction perpendicular to the tube axis 15 in the heat exchanger 1 according to Embodiment 1 of the present disclosure.
The heat transfer tubes 12 of the heat exchanger 1 according to Embodiment 1 each have an inner surface provided with a plurality of grooves 14 that are recesses extending spirally. The grooves 14 serve as part of a flow passage for refrigerant, which is fluid. Because of provision of the grooves 14, for example, a surface area of the inner surface of the heat transfer tube 12 is increased, the fluid is stirred, and a liquid film is held by capillary action, thereby promoting heat transfer between the heat transfer tube 12 and refrigerant that flows in the heat transfer tube 12. The grooves 14 are formed in the inner surface of the heat transfer tube 12 such that an imaginary line that extends in the direction along the tube axis 15 and an imaginary line that extends in a direction in which the grooves 14 spirally extend form a certain angle. This angle will be hereinafter referred to as a lead angle θ. Also, because of provision of the grooves 14, recessed parts and raised parts are formed at the inner surface of the heat transfer tube 12. Although the recessed parts correspond to the grooves 14, the height of the raised parts corresponds to the height h of the grooves 14 in Embodiment 1 as described later.
Next, a relationship between the lead angle θ in heat transfer tubes 12 and a flow passage length L of the heat transfer tubes 12 in the heat exchanger 1 according to Embodiment 1 will be described. To be more specific, in the heat exchanger 1 according to Embodiment 1, in heat transfer tubes 12, in the case where a flow passage length L is 10 m or less (L≤10 m), grooves 14 are formed such that the lead angle θ falls within the range of 25 degrees to 45 degrees (25°≤θ≤45°). On the other hand, in the heat transfer tubes 12, in the case where the flow passage length L is greater than 10 m (L>10 m), the grooves 14 are formed such that the lead angle θ is 5 degrees or more and less than 25 degrees (5≤θ<25°). The flow passage length L is the length of heat transfer tubes 12 that extends from the heat exchanger inlet 1A to the heat exchanger outlet 1B to allow refrigerant to flow from the heat exchanger inlet 1A to the heat exchanger outlet 1B. Referring to Fig. 1, the sum of lengths L1, L2, and L3 of heat transfer tubes 12 of heat exchanger bodies 10 located on a path of the flow passage pipe 20 indicated by solid lines in Fig. 1 is the flow passage length L.

Fig. 5 indicates a correlation between the lead angle θ at the heat transfer tube 12 and the performance of the heat transfer tube 12 according to Embodiment 1 of the present disclosure. In Fig. 5, the performance of the heat transfer tube 12 is expressed by in-pipe heat transfer coefficient αi. In the case where refrigerant flows at a constant flow rate in the heat transfer tube 12, when the lead angle θ increases, the in-pipe heat transfer coefficient αi increases while the value by which the in-pipe heat transfer coefficient αi increases decreases. Furthermore, in-pipe refrigerant pressure loss ΔPref monotonically increases. In general, the greater the in-pipe heat transfer coefficient αi and the smaller the in-pipe refrigerant pressure loss ΔPref, the higher the efficiency of the heat exchange. Therefore, the optimum shape of the grooves 14 depends on the type of the heat exchanger 1.
Fig. 6 schematically indicates a correlation between the lead angle θ at the heat transfer tube 12 and an annual performance factor (APF) in Embodiment 1 of the present disclosure. The annual performance factor (APF) is an indicator indicative of annual performance of an air conditioner. The greater the flow passage length L, the greater the influence of the in-pipe refrigerant pressure loss ΔPref. As described above, in the case where the lead angle θ is small, the in-pipe refrigerant pressure loss ΔPref is small. Thus, when the lead angle θ is reduced, the APF tends to be improved. By contrast, the smaller the flow passage length L, the greater the influence of the in-pipe heat transfer coefficient αi. As described above, in the case where the lead angle θ is great, the in-pipe heat transfer coefficient αi is also great. Thus, when the lead angle θ is increased, the APF tends to be improved.
For example, a test of a room air conditioner was conducted regarding the case where the flow passage length L is 10 m or less (L≤10 m) and the case where the flow passage length L is greater than 10 m (L>10 m). According to the result of the test, it was found that a threshold value of the APF lies at a lead angle θ of 25 degrees, as illustrated in Fig. 6. In view of this, in the case where the flow passage length L is 10 m or less (L≤10 m), preferably, the above associated heat transfer tubes 12 should be formed to have grooves 14 having a lead angle θ that falls within the range of 25 degrees to 45 degrees (25°≤α ≤45°), and in the case where the flow passage length L is more than 10 m (L>10 m), preferably, the heat transfer tubes 12 should be formed to have grooves 14 having a lead angle θ that is 5 degrees or more and less than 25 degrees (5°≤θ<25°).
In general, a heat transfer tube 12 tends to be formed such that the smaller the outside diameter, the smaller the inside diameter. Therefore, as the outside diameter of the heat transfer tube 12 decreases, the inside diameter decreases, as a result of which the in-pipe refrigerant pressure loss ΔPref increases. It should be noted that for example, at present, many room air conditioners employ heat transfer tubes each having an outside diameter of ϕ7.0 or ϕ6.35. On the other hand, in the heat transfer tube 12 according to Embodiment 1, the outside diameter and the inside diameter can be made smaller while maintaining the in-pipe refrigerant pressure loss ΔPref. For example, it is possible to use a heat transfer tube 12 having an outside diameter of ϕ5.0 or less, in which the in-pipe refrigerant pressure loss ΔPref is approximately two or more times greater than in a heat transfer tube having an outside diameter of ϕ7.0. Furthermore, by reducing the diameter of the heat transfer tube 12, an in-pipe volume thereof can be reduced. It is therefore possible to reduce the amount of refrigerant that is required for the entire refrigerant circuit. In particular, it should be noted that in the case where flammable refrigerant is used, the safety of the apparatus can be further improved by reducing the amount of the refrigerant.
As described above, in the heat exchange 1 according to Embodiment 1, regarding associated ones of the heat transfer tubes 12 through which refrigerant passes, in the case where the flow passage length L is 10 m or less (L≤10 m), grooves 14 are formed such that the lead angle θ falls within the range of 25 degrees to 45 degrees (25°≤θ≤45°), and in the case where the flow passage length L is greater than 10 m (L>10 m), the grooves 14 are formed such that the lead angle θ is 5 degrees or more and less than 25 degrees (5≤θ<25). It is therefore possible to increase the APF of an air-conditioning apparatus.

Embodiment 2

Embodiment 2 will be described by referring manly to the differences between the heat transfer tubes 12 according to Embodiments 1 and 2. The heat transfer tubes 12 according to Embodiment 2 basically have a similar configuration to the heat transfer tubes 12 according to Embodiment 1, and each have an inner surface in which a plurality of spiral grooves 14 are formed. It should be noted that regarding Embodiment 1, the groove height h of the grooves 14 is not described above in detail. In Embodiment 2, the heat transfer tube 12 is formed such that in the case where the flow passage length L is 10 m or less (L ≤10 m), the grooves 14 are formed in the inner surface to have a groove height h of 0.06 mm or more (h≥0.06 mm), and in the case where the flow passage length L is more than 10 m (L>10 m), the grooves 14 are formed in the inner surface to have a groove height h of more than 0.06 mm (0.06<h).

Fig. 7 indicates a correlation between the groove height h of the heat transfer tube 12 and the performance of the heat transfer tube 12 according to Embodiment 2 of the present disclosure. In Fig. 7, the performance of the heat transfer tube 12 is expressed by in-pipe heat transfer coefficient αi. In the case where refrigerant flows at a constant flow rate in the heat transfer tube 12, when the groove height h increases, the in-pipe heat transfer coefficient αi increases while the value by which the in-pipe heat transfer coefficient αi increases decreases. The in-pipe refrigerant pressure loss ΔPref monotonically increases. As also described regarding Embodiment 1, in general, the greater the in-pipe heat transfer coefficient αi and the smaller the in-pipe refrigerant pressure loss ΔPref, the higher the efficiency of the heat exchange.
Fig. 8 schematically indicates a correlation between the groove height h of the heat transfer tube 12 and the APF in Embodiment 2 of the present disclosure. As described regarding Embodiment 1, the greater the flow passage length L, the greater the influence of the in-pipe refrigerant pressure loss ΔPref. Therefore, in this case, when the groove height h is small, the APF tends to be improved. By contrast, the smaller the flow passage length L, the greater the influence of the in-pipe heat transfer coefficient αi. Therefore, in this case, when the groove height h is great, the APF tends to be improved.
For example, a test of the room air conditioner was conducted regarding the case where the flow passage length L is 10 m or less (L≤10 m) and the case where the flow passage length L is greater than 10 m (L>10 m). According to the result of the test, it was found that a threshold value of the APF lies at a groove height h of 0.06 mm, as illustrated in Fig. 8. Therefore, in heat transfer tubes 12, in the case where the flow passage length L is 10 m or less (L≤10 m), preferably, grooves 14 should be formed such that the groove height h is 0.06 mm or more (h≥0.06 mm), and in the case where the flow passage length L is greater than 10 m (L>10 m), preferably, the grooves 14 should be formed such that the groove height h is greater than 0.06 mm (0.06<h).
As described above, in the above heat transfer tubers 12 of the heat exchanger 1 according to Embodiment 2, in the case where the flow passage length L is 10 m or less (L≤10 m), grooves 14 are formed in the inner surfaces of the heat transfer tubes 12 to have a groove height h of 0.06 mm or more (h≥0.06 mm), and in the case where the flow passage length L is more than 10 m (L>10 m), the grooves 14 are formed in the inner surfaces of the heat transfer tubes 12 to have a groove height h of more than 0.06 mm (0.06<h). It is therefore possible to the APF of the air-conditioning apparatus. Furthermore, the amount of refrigerant that is required for the entire refrigerant circuit can be reduced by reducing the diameter of the heat transfer tube 12 and also reducing the in-pipe volume of the heat transfer tube 12. In particular, it should be noted that in the case where flammable refrigerant is used, the safety of the apparatus can be further improved by reducing the amount of the refrigerant. The grooves 14 may be formed in such a manner as to satisfy both the conditions concerning the lead angle θ as described regarding Embodiment 1 and the conditions concerning the groove height h of the grooves 14 regarding Embodiment 2.

Embodiment 3

Fig. 9 illustrates a configuration of a refrigeration cycle apparatus according to Embodiment 3 of the present disclosure. An air-conditioning apparatus 50 that cools or heats an air-conditioned space will be described as an example of the refrigeration cycle apparatus. The air-conditioning apparatus is an apparatus that air-conditions the air-conditioned space by circulating refrigerant while changing in phase the refrigerant from liquid refrigerant to gas refrigerant and from gas refrigerant to liquid refrigerant through steps of evaporation, compression, condensation, and expansion and thus transferring heat to and from the refrigerant.
The air-conditioning apparatus 50 as illustrated in Fig. 9 includes an outdoor unit 200 and an indoor unit 100. A compressor 210, a four-way valve 220, a heat-source-side heat exchanger 230, and an expansion device 240 of the outdoor unit 200, and a load-side heat exchanger 110 of the indoor unit 100 are connected by a gas refrigerant pipe 300 and a liquid refrigerant pipe 400, whereby a refrigerant cycle circuit is formed. In Fig. 9, the flow of refrigerant during cooling operation is indicated by solid line arrows, and flow of refrigerant during heating operation is indicated by dotted line arrows.
The outdoor unit 200 includes the compressor 210, the four-way valve 220, the heat-source-side heat exchanger 230, the expansion device 240, and a heat-source-side fan 250. The compressor 210 compresses sucked refrigerant and discharges the compressed refrigerant. The compressor 210 may be, but is not limited to, a compressor whose capacity (the amount of refrigerant to be fed per unit time) is changed by causing, for example, an inverter circuit to change an operating frequency of the compressor. The four-way valve 220 is a valve that switches the flow of refrigerant, for example, in accordance with whether an operation mode is the cooling operation or the heating operation.
The heat-source-side heat exchanger 230 according to Embodiment 3 causes heat exchange to be performed between refrigerant and air (outdoor air). For example, during the heating operation, the heat-source-side heat exchanger 230 operates as an evaporator that evaporates and gasifies refrigerant. During the cooling operation, the heat-source-side heat exchanger 230 operates as a condenser that condenses and liquefies refrigerant. The heat-source-side fan 250 sends air to the heat-source-side heat exchanger 230. The heat-source-side fan 250 is controlled by a controller 60A.
The expansion device 240 such as an expansion valve (flow-amount control unit) reduces refrigerant in pressure to expand the refrigerant. For example, in the case where the expansion device 240 is an electronic expansion valve, the opening degree of the expansion device 240 is adjusted in response to an instruction from the controller 60A.
The indoor unit 100 includes the load-side heat exchanger 110 and a load-side fan 120. For example, the load-side heat exchanger 110 causes heat exchange to be performed between air to be air-conditioned and refrigerant. During the heating operation, the load-side heat exchanger 110 operates as a condenser that condenses and liquefies refrigerant. During the cooling operation, the load-side heat exchanger 110 operates as an evaporator that evaporates and gasifies refrigerant. In this case, the heat exchanger 1 according to Embodiment 1 or Embodiment 2 is used as the load-side heat exchanger 110. This, however, is not limiting. The heat exchanger 1 according to Embodiment 1 or Embodiment 2 may be used as the heat-source-side heat exchanger 230. That is, the heat exchanger 1 according to Embodiment 1 or Embodiment 2 is used as at least one of a heat exchanger that operates as a condenser and a heat exchanger that operates as an evaporator. By using the heat exchanger 1 as the load-side heat exchanger 110, an air conditioner having a high heat exchange efficiency and high performance can be provided. The load-side fan 120 sends air to the load-side heat exchanger 110. The load-side fan 120 is controlled by a controller 60A.
The controller 60A and the controller 60B are connected to the compressor 210, the four-way valve 220, the expansion device 240, the heat-source-side fan 250, the load-side fan 120, various sensors, etc. The controller 60A and the controller 60B control operation of devices such as the compressor 210 in response to signals supplied from the various sensors. The controller 60A and the controller 60B switch the operation between the cooling operation and the heating operation by switching the flow passage of the four-way valve 220.
First, the flow of refrigerant in the air-conditioning apparatus 50 during the cooling operation will be described. High-pressure, high-temperature gas refrigerant discharged from the compressor 210 flows into the heat-source-side heat exchanger 230 through the four-way valve 220 and exchanges heat with outside air supplied by the heat-source-side fan 250 to condense and change into high-pressure liquid refrigerant, and the high-pressure liquid refrigerant then flows out from the heat-source-side heat exchanger 230. The high-pressure liquid refrigerant that has flowed out of the heat-source-side heat exchanger 230 flows into the expansion device 240 and changes into low-pressure two-phase gas-liquid refrigerant. The low-pressure two-phase gas-liquid refrigerant that has flowed out of the expansion device 240 flows into the load-side heat exchanger 110 and exchanges with indoor air supplied by the load-side fan 120 to evaporate and change into low-pressure gas refrigerant, and the low-pressure gas refrigerant then flows out of the load-side heat exchanger 110. The low-pressure gas refrigerant that has flowed out of the load-side heat exchanger 110 is sucked into the compressor 210 through the four-way valve 220.
Next, the flow of refrigerant in the air-conditioning apparatus 50 during the heating operation will be described. High-pressure, high-temperature gas refrigerant discharged from the compressor 210 flows into the load-side heat exchanger 110 through the four-way valve 220. At the load-side heat exchanger 110, the refrigerant exchanges heat with indoor air supplied by the load-side fan 120 to condense and change into high-pressure liquid refrigerant, and the high-pressure liquid refrigerant then flows out of the load-side heat exchanger 110. The high-pressure liquid refrigerant that has flowed out of the load-side heat exchanger 110 flows into the expansion device 240 and change into low-pressure two-phase gas-liquid refrigerant. After flowing out of the expansion device 240, the low-pressure two-phase gas-liquid refrigerant flows into the heat-source-side heat exchanger 230 and exchanges heat with outdoor air supplied by the heat-source-side fan 250 to evaporate and change into low-pressure gas refrigerant, and the low-pressure gas refrigerant then flows out of the heat-source-side heat exchanger 230. The low-pressure gas refrigerant that has flowed out of the heat-source-side heat exchanger 230 is sucked into the compressor 210 through the four-way valve 220.
As refrigerating machine oil for use in the compressor 210, preferably, immiscible oil such as HAB oil should be used in terms of solubility of refrigerant in the refrigerating machine oil and replacement of a unit with a new one. To reduce the remaining amount of refrigerating machine oil in the heat transfer tubes in the heat exchanger, it is preferable to use the heat transfer tube 12 in which in-pipe pressure loss is small. Therefore, an air-conditioning apparatus 50 employing the heat exchanger 1 according to either Embodiment 1 or Embodiment 2 can have high performance and high quality.
In the case where the air-conditioning apparatus 50 is used as a room air conditioner, in general, R32 is used as refrigerant for use in the air-conditioning apparatus 50. In consideration of an environment, etc., it is preferable that refrigerant having lower GWP (global warming potential) be used. As such refrigerant, R290 can be applied. However, in the case of using R290, the in-pipe refrigerant pressure loss ΔPref is larger than in the case of using R32. In addition, R290 is highly flammable refrigerant, and thus if a large amount of 290 is applied, it may burn. On this point, the heat exchanger 1 according to Embodiment 1 or Embodiment 2 is advantageous, that is, can compensate for the in-pipe refrigerant pressure loss ΔPref of R290. Furthermore, the in-pipe volume of the heat exchanger 1 can be reduced, and the amount of the refrigerant can thus be reduced. It is therefore possible to provide a refrigeration cycle apparatus having high performance and high quality. Reference Signs List
1 heat exchanger 1A heat exchanger inlet 1B heat exchanger outlet 10 heat exchanger body 11 plate-shaped fin 12 heat transfer tube 14 groove 15 tube axis 20 flow passage pipe 50 air- conditioning apparatus 60A, 60B controller 100 indoor unit 110 load-side heat exchanger 120 load-side fan 200 outdoor unit 210 compressor 220 four-way valve 230 heat-source-side heat exchanger 240 expansion device 250 heat-source-side fan 300 gas refrigerant pipe 400 liquid refrigerant pipe

Claims

A heat exchanger comprising:
heat transfer tubes each of which allow fluid to flow therethrough and has an inner surface provided with grooves that are recessed parts spirally extending in a direction along a tube axis of each heat transfer tube; and

heat exchanger bodies including fins that are in contact with the heat transfer tubes to promote heat exchange of the fluid,

wherein in a case where of the heat transfer tubes, heat transfer tubes that allow the fluid to flow from an inlet of the heat exchanger to an outlet of the heat exchanger have a flow passage length L of 10 m or less, the grooves of the inner surface of each of the heat transfer tubes having the flow passage length L are formed such that a lead angle θ between the tube axis and an extending direction of the grooves falls within a range of 25 degrees to 45 degrees, and in a case where the heat transfer tubes that allow the fluid to flow from the inlet of the heat exchanger to the outlet of the heat exchanger have a flow passage length L of greater than 10 m, the grooves of the inner surface of each of the heat transfer tubes having the flow passage length L are formed such that the lead angle θ is 5 degrees or more and less than 25 degrees.
The heat exchanger of claim 1, wherein in the case where the heat transfer tubes that allow the fluid to flow from the inlet of the heat exchanger to the outlet of the heat exchanger have the flow passage length L of 10 m or less, the associated grooves are formed to have a groove height h of 0.06 mm or more, and in the case where the heat transfer tubes that allow the fluid to flow from the inlet of the heat exchanger to the outlet of the heat exchanger have the flow passage length L of greater than 10 m, the associated grooves are formed to have a groove height h of less than 0.06 mm.
A heat exchanger comprising:
heat transfer tubes each of which allows fluid to flow therethrough and has an inner surface provided with grooves that are recessed parts spirally extending in a direction of a tube axis of each transfer tube; and

exchanger bodies including fins that are in contact with the heat transfer tubes to promote heat exchange of the fluid,

wherein in a case where of the heat transfer tubes, heat transfer tubes that allow the fluid to flow from an inlet of the heat exchanger to an outlet of the heat exchanger have a flow passage length L of 10 m or less, the grooves of the inner surface of each of the heat transfer tubes having the flow passage length L are formed to have a groove height h of 0.06 mm or more, and in a case where the heat transfer tubes that allow the fluid to flow from the inlet of the heat exchanger to the outlet of the heat exchanger have a flow passage length L of greater than 10 m, the grooves of the inner surface of each of the heat transfer tubes having the flow passage length L are formed to have a groove height of less than 0.06 mm.
The heat exchanger of any one of claims 1 to 3, wherein the heat transfer tubes each have an outside diameter of ϕ5.0 or less.
The heat exchanger of any one of claims 1 to 4, further comprising a flow passage pipe that connects ones of the heat exchanger bodies that are located from the inlet of the heat exchanger to the outlet of the heat exchanger.
A refrigeration cycle apparatus comprising:
a compressor configured to compress sucked refrigerant;

a condenser configured to cause the refrigerant to be subjected to heat exchange, thereby condensing the refrigerant;

an expansion device configured to reduce a pressure of the condensed refrigerant; and

an evaporator configured to cause the refrigerant the pressure of which is reduced, to be subjected to heat exchange, thereby evaporating the refrigerant,

wherein the compressor, the condenser, the expansion device, and the evaporator are connected by pipes, whereby a refrigerant circuit configured to circulate the refrigerant is provided, and

wherein the heat exchanger of any one of claims 1 to 5 is used as at least one of the condenser and the evaporator.
The refrigeration cycle apparatus of claim 6, wherein refrigerating machine oil is oil that is immiscible with the refrigerant.
The refrigeration cycle apparatus of claim 6 or 7, wherein the refrigerant is R290.
An air-conditioning apparatus that cools or heats an air-conditioned space with the refrigeration cycle apparatus of any one of claims 6 to 8.