JP6698196B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner equipped with a highly efficient heat exchanger.

  In the heat exchanger of the air conditioner, the flow velocity of the refrigerant in the heat transfer tube is optimized to optimize the balance between the pressure loss on the refrigerant side and the heat transfer coefficient, thereby enhancing the performance of the heat exchanger. That is, in order to exert the heat exchanger performance, the design is performed in consideration of the flow passage inner diameter of the heat transfer tube and the number of refrigerant flow passages.

  In a heat exchanger in which three rows of heat transfer tubes are arranged, the heat transfer tube diameter D1 on the most windward side is made the smallest and D1=3 to 4 mm, and the heat transfer tube diameter D2 in the middle and leeward. It has been proposed that the relationship with the side heat transfer relationship D3 is D1<D2=D3, 4 mm≦D3≦10 mm, and 0.6≦D1/D2<1 (see, for example, Patent Document 1). With this configuration, the heat exchange performance is improved while suppressing an increase in pressure loss.

  Further, the heat transfer tube of the fin connected to the liquid side distributor or the gas side distributor is reciprocated once, and the heat transfer tube is branched and connected to two heat transfer tubes of adjacent fins, and one path of the heat transfer tube is constituted by two reciprocations. It has also been proposed (see, for example, Patent Document 2). With this configuration, by increasing the flow velocity on the liquid side, the pressure loss in the heat transfer tube increases, while the surface heat transfer coefficient improves.

JP, 2011-122819, A JP, 2010-78287, A

  However, the configuration described in Patent Document 1 requires a manufacturing apparatus for each different diameter of the heat transfer tube, so that the number of manufacturing steps of the heat exchanger increases. Furthermore, in the row on the windward side where the heat transfer tubes of small diameter are arranged, the heat transfer area inside the heat transfer tubes is reduced, and the overall performance of the heat exchanger is reduced.

  Further, when the heat exchanger disclosed in Patent Document 2 acts as a condenser, heat conduction through fins between vertically adjacent heat transfer tubes influences the temperature change in the supercooling region. The internal heat exchange causes heat loss in the supercooled region.

  The present invention has been made in view of the above problems, and an object thereof is to provide an air conditioner including a high-performance heat exchanger.

  In order to solve the above problems, an air conditioner according to an aspect of the present invention is an air conditioner including a heat exchanger that has a plurality of heat transfer tubes through which a refrigerant flows and exchanges heat with air. The heat exchanger has one end and the other end, and the plurality of heat transfer tubes have the one end and the other end in a state of being aligned in a direction intersecting with a direction in which air flows. The rows of the plurality of heat transfer tubes that are arranged so as to reciprocate and are arranged in the intersecting direction are configured to be arranged in at least two rows along the direction in which the air flows, and the two rows have the air It has a first row located at the most upstream in the flowing direction and a second row located next to the first row in the direction in which the air flows, and the plurality of heat transfer tubes are mutually arranged in the second row. An adjacent first heat transfer tube and a second heat transfer tube are provided, and the first heat transfer tube and the second heat transfer tube respectively extend from the other end to the one end, and the one end Are joined together to form a first joint pipe, and the first joint pipe is configured to make one round trip between the one end portion and the other end portion in the uppermost row, and the first joint pipe is connected to the plurality of transmission pipes. The heat pipe further includes a third heat transfer pipe and a fourth heat transfer pipe that are adjacent to each other in the second row, and the third heat transfer pipe and the fourth heat transfer pipe include the first heat transfer pipe and the first heat transfer pipe. 2 is arranged adjacent to the heat transfer tube, extends the second row from the other end portion to the one end portion, respectively, and is joined at the one end portion to form a second joining pipe, wherein the second joining pipe is A portion of the uppermost row configured to reciprocate between the one end portion and the other end portion, and a portion of the first coupling pipe extending from the other end portion to the one end portion, and the second portion. A portion of the coupling pipe that extends from the other end to the one end is arranged so as to be adjacent to each other.

  In order to solve the above problems, an air conditioner according to an aspect of the present invention is an air conditioner including a heat exchanger that has a plurality of heat transfer tubes through which a refrigerant flows and exchanges heat with air. The heat exchanger has one end and the other end, and the plurality of heat transfer tubes have the one end and the other end in a state of being aligned in a direction intersecting with a direction in which air flows. The rows of the plurality of heat transfer tubes that are arranged so as to reciprocate and are arranged in the intersecting direction are configured to be arranged in at least two rows along the direction in which the air flows, and the two rows have the air It has a first row located at the most upstream in the flowing direction and a second row located next to the first row in the direction in which the air flows, and the plurality of heat transfer tubes are mutually arranged in the second row. An adjacent first heat transfer tube and a second heat transfer tube are provided, and the first heat transfer tube and the second heat transfer tube respectively extend from the other end to the one end, and the one end And a single heat transfer tube, the one heat transfer tube is configured to make one round trip between the one end and the other end in the first row, and the refrigerant is R32 or a refrigerant containing 70% by weight or more of R32.

  According to the present invention, it is possible to provide an air conditioner including a high-performance heat exchanger.

1 shows a refrigeration cycle of an air conditioner according to the present invention. It is the figure which showed the refrigeration cycle at the time of heating operation when R410A was used as a refrigerant and when R32 was used as a refrigerant on the Mollier diagram. It is a figure which shows the influence on the pressure loss of a heat transfer tube of a refrigerant|coolant circulation amount. It is a figure which shows the influence of the circulating amount of a refrigerant|coolant on the surface heat transfer coefficient of a heat transfer tube. It is a cross-sectional view of a ceiling-embedded indoor unit. It is a longitudinal cross-sectional view of a ceiling-embedded indoor unit. It is a figure which shows the structure of the heat transfer tube and fin of an indoor heat exchanger. It is a longitudinal cross-sectional view of an indoor heat exchanger. FIG. 9 is a sectional view taken along line IX-IX in FIG. 8. It is a figure which shows the structure of the heat transfer tube and the fin of the conventional indoor heat exchanger. It is a figure which shows the relationship between the subcooling degree of an indoor heat exchanger at the time of heating operation, and COP. It is a figure which shows the influence on the COP of the subcooling degree at the time of heating operation in the air conditioner which used R32 for a refrigerant. It is a figure which shows the influence on the COP of the subcooling degree at the time of heating operation in the air conditioner which used R410A as a refrigerant. It is a figure which shows the influence on the COP of the amount of refrigerant circulation at the time of cooling operation in the air conditioner which uses R32 as a refrigerant. It is a figure which shows the influence on the COP of the refrigerant|coolant circulation amount at the time of cooling operation in the air conditioner which uses R410A as a refrigerant. It is a figure which shows the relationship between the mass flux at the time of evaporation, the heat transfer coefficient in a pipe, and a pressure loss. It is a figure which shows the relationship between the mass flux at the time of condensation, a heat transfer coefficient in a pipe, and a pressure loss. It is explanatory drawing of the performance influence of an air conditioner by a heat transfer tube outer diameter. It is explanatory drawing of the performance influence of the air conditioner by the up-down pitch of the heat transfer tubes of a heat exchanger. It is explanatory drawing of the performance influence of the air conditioner by the horizontal pitch of the heat exchanger tubes of a heat exchanger. It is explanatory drawing of the performance influence of the air conditioner by fin plate thickness t of a heat exchanger, and fin pitch Pf. It is a figure which shows the modification of the row structure of the heat transfer tube of an indoor heat exchanger. It is an external view which shows a three-pronged vent. It is a figure which shows the other example of a change of the row structure of the heat transfer tube of an indoor heat exchanger. It is a figure which shows the case where the row structure of the heat transfer tube of an indoor heat exchanger is two rows. It is a figure which shows the case where the row configuration of the heat transfer tubes of an indoor heat exchanger is 4 rows.

  Hereinafter, an air conditioner according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a refrigeration cycle of an air conditioner 1 according to an embodiment of the present invention.

  The air conditioner 1 includes an outdoor unit 10 and an indoor unit 20. The outdoor unit 10 and the indoor unit 20 are connected by the gas connection pipe 2 and the liquid connection pipe 3. In the present embodiment, the outdoor unit 10 and the indoor unit 20 are connected in a one-to-one manner, but a plurality of outdoor units may be connected to one indoor unit, or one outdoor unit. Alternatively, a plurality of indoor units may be connected.

  The outdoor unit 10 includes a compressor 11, a four-way valve 12, an outdoor heat exchanger 13, an outdoor fan 14, an outdoor expansion valve 15, and an accumulator 16. Further, the outdoor heat exchanger 13 is provided with an outdoor gas side refrigerant distributor 17 and an outdoor liquid side refrigerant distributor 18.

  The compressor 11 compresses the refrigerant and discharges it into the pipe. By switching the four-way valve 12, the flow of the refrigerant changes, and the cooling operation and the heating operation are switched. The outdoor heat exchanger 13 exchanges heat between the refrigerant and the outside air. The outdoor fan 14 supplies outside air to the outdoor heat exchanger 13. The outdoor expansion valve 15 reduces the pressure of the refrigerant to a low temperature. The accumulator 16 is provided to store the liquid return during the transition and adjusts the refrigerant to an appropriate dryness.

  The indoor unit 20 includes an indoor heat exchanger 21, an indoor fan 22, and an indoor expansion valve 23. The indoor heat exchanger 21 exchanges heat between the refrigerant and the inside air. The indoor fan 22 supplies outside air to the outdoor heat exchanger 21. The indoor expansion valve 23 can change the flow rate of the refrigerant flowing through the indoor heat exchanger 21 by changing the throttle amount. Further, the indoor heat exchanger 21 is provided with an indoor gas side refrigerant distributor 24 and an indoor liquid side refrigerant distributor 25.

  In the air conditioner 1 according to the present embodiment, R32 is used alone (100% by weight) or R32 is 70 as a refrigerant that is enclosed in the refrigeration cycle and has a function of carrying thermal energy during the cooling operation and the heating operation. A mixed refrigerant containing more than wt% is used.

  Next, the operation of the refrigeration cycle of the air conditioner 1 will be described.

  First, the cooling operation in the air conditioner 1 will be described. In the cooling operation, the four-way valve 12 connects the discharge side of the compressor 11 and the outdoor heat exchanger 13 and connects the suction side of the compressor 11 and the gas connection pipe 2 as shown by the solid line.

  The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 passes through the four-way valve 12 and flows into the outdoor heat exchanger 13. The high-temperature gas refrigerant that has entered the outdoor heat exchanger 13 exchanges heat with the outdoor air supplied by the outdoor fan 14 and is condensed to become a liquid refrigerant. The liquid refrigerant passes through the outdoor expansion valve 15 and the liquid connection pipe 3 and flows into the indoor unit 20. The liquid refrigerant that has flowed into the indoor unit 20 is decompressed by the indoor expansion valve 22 and becomes a low-temperature low-pressure gas-liquid mixed refrigerant. The low-temperature low-pressure refrigerant flows into the indoor heat exchanger 21, is heat-exchanged with the indoor air supplied by the indoor fan 22, and is evaporated to become a gas refrigerant. At this time, the indoor air is cooled by the latent heat of vaporization of the refrigerant, and cold air is sent indoors. After that, the gas refrigerant is returned to the outdoor unit 10 through the gas connection pipe 2.

  The gas refrigerant returned to the outdoor unit 10 passes through the four-way valve 12 and the accumulator 16, is sucked into the compressor 11, and is compressed by the compressor 11 again, thereby forming a series of refrigeration cycles.

  Next, the heating operation in the air conditioner 1 will be described. In the heating operation, the switching valve 12 makes the discharge side of the compressor 11 communicate with the gas connection pipe 2 and the suction side of the compressor 11 communicates with the outdoor heat exchanger 13 as shown by the dotted line.

  The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 is sent to the gas connection pipe 2 through the four-way valve 12 and flows into the indoor heat exchanger 21 of the indoor unit 20. The high-temperature and high-pressure gas refrigerant flowing into the indoor heat exchanger 21 exchanges heat with the indoor air supplied by the indoor fan 23 and condenses to become a high-pressure liquid refrigerant. At this time, the indoor air is heated by the refrigerant, and warm air is sent indoors. After that, the liquefied refrigerant passes through the indoor expansion valve 22 and the liquid connection pipe 3 and is returned to the indoor unit 10.

  The liquid refrigerant that has returned to the outdoor unit 10 is decompressed by the outdoor expansion valve 15 and becomes a low-temperature low-pressure gas-liquid mixed refrigerant. The depressurized refrigerant flows into the outdoor heat exchanger 13, exchanges heat with the outside air supplied by the outdoor fan 14, is evaporated, and becomes a low-pressure gas refrigerant. The gas refrigerant flowing out of the outdoor heat exchanger 13 passes through the accumulator 16 and is sucked into the compressor 11 and compressed by the compressor 11 again to form a series of refrigeration cycles.

  Next, the characteristics of R32 used in the air conditioner 1 of the present embodiment will be described. Specifically, the difference in the use of these refrigerants due to the difference in the refrigerant physical properties between R32 and R410A will be described. FIG. 2 is a diagram showing on the Mollier diagram the refrigeration cycle during the heating operation when R410A (broken line) is used as the refrigerant and when R32 (solid line) is used as the refrigerant. Note that R410A is a refrigerant that has been used conventionally, and has a higher GWP (Global Warming Potential) than R32.

  Since R32 has a characteristic that the latent heat of vaporization is larger than that of R410A, the specific enthalpy difference in the evaporator or condenser indicated by Δhe_R32 and Δhc_R32 of R32 is larger than Δhe_R410A and Δhc_R410A of R410A. Therefore, R32 can reduce the refrigerant circulation amount required to generate the same capacity as R410A.

  Here, Δhe represents a specific enthalpy difference in the evaporator, Δhc represents a specific enthalpy difference in the condenser, and subscripts _R410A and _R32 represent the states of the refrigerants R410A and R32.

  When R32 is used as the refrigerant, the refrigerant circulation amount can be reduced, so that the pressure loss when the refrigerant passes through the flow paths of the heat exchangers 13 and 21 is reduced, and the differential pressure between the high pressure and the low pressure is reduced. .. Therefore, the required compression power in the compressor 11 can be reduced, and there is an effect of improving the COP (Coefficient of Performance) of the air conditioner 1. On the other hand, due to the decrease in the refrigerant flow velocity in the heat transfer tubes of the heat exchangers 13 and 21, the surface heat transfer coefficient on the refrigerant side may decrease, and the efficiency of the heat exchangers 13 and 21 may decrease.

  FIG. 3 is a diagram showing the influence of the refrigerant circulation amount on the pressure loss of the heat transfer pipe, and FIG. 4 is a diagram showing the influence of the refrigerant circulation amount on the surface heat transfer coefficient of the heat transfer pipe.

  As shown in FIGS. 3 and 4, when R32 is used in the condenser rather than in the evaporator, the pressure loss becomes relatively smaller and the surface heat transfer coefficient becomes smaller. Therefore, in the air conditioner 1 that switches between cooling and heating to be used, the refrigerant circulation amount per one flow path (one heat transfer pipe 26 (FIG. 7)) of the heat exchangers 13 and 21 is set for both cooling and heating. It is necessary to set the flow rate with good balance.

  In order to adjust the refrigerant circulation amount per flow path of the heat exchangers 13 and 21, for example, at the refrigerant inlet of the indoor heat exchanger 21, the indoor gas side refrigerant distributor 24 and the indoor liquid side refrigerant distributor 25 (FIG. 7). Is used. The distributors 24 and 25 are branched into a plurality of flow paths (a plurality of heat transfer tubes 26) so that the refrigerant flows in the indoor heat exchanger 21.

  Next, the configuration of the ceiling-embedded 4-way blowout indoor unit 20 according to the present embodiment will be described in detail. FIG. 5 shows a horizontal cross section of the indoor unit 20 of the air conditioner 1, and FIG. 6 shows a vertical cross section of the indoor unit 20.

  As shown in FIGS. 5 and 6, the indoor heat exchanger 21 and the indoor fan 22 are housed in the housing 28 of the indoor unit 20, and the indoor heat exchanger 21 is arranged so as to surround the indoor fan 22. . As described above, the indoor unit 20 in the present embodiment is a ceiling-embedded four-way blowout indoor unit.

  As shown in FIG. 5, the indoor heat exchanger 21 has a shape that substantially surrounds the indoor fan 22 and surrounds it (a substantially square shape), and has one end 21A and the other end 21B. Therefore, since the length of the indoor heat exchanger 21 becomes long, when the indoor heat exchanger 21 is divided into a plurality of flow paths, branching and gathering are possible only at both ends of the indoor heat exchanger 21, so There are many restrictions on road division. An indoor gas side refrigerant distributor 24 and an indoor liquid side refrigerant distributor 25 are connected to one end 21A of the indoor heat exchanger 21.

  Further, as shown in FIG. 6, the air introduced from the room by the indoor fan 22 exchanges heat in the indoor heat exchanger 21 and is sent to the room through the outlet.

  FIG. 7 shows the configuration of the heat transfer tubes 26 and the fins 27 of the indoor heat exchanger 21 in this embodiment. The arrow in FIG. 7 indicates the flow of the refrigerant flowing through the heat transfer tube 26 during the heating operation. As shown in FIG. 7, the plurality of heat transfer tubes 26 are inserted into a plurality of metal plate-shaped fins 27. The plurality of heat transfer tubes 26 has a row configuration including three rows formed along the airflow direction F in which a plurality of heat transfer tubes 26 are formed side by side in a direction intersecting the airflow direction F of the indoor air.

  With the three-row configuration, when acting as a condenser, the temperature difference between the suction air and the suction air can be kept relatively uniform when the refrigerant passage is formed in the direction opposite to the air flow. Yes, the fins of the heat exchanger can be divided every time the refrigerant temperature level in the first, second, and third rows is different from the air flow in the subcooling area, saturation area, and superheating area. Have an advantage. Furthermore, it is superior in terms of ventilation resistance and mounting space.

  The row configuration includes an uppermost row (first row) L1 located at the uppermost stream in the airflow direction F, a lowermost row (third row) L3 located at the most downstream in the airflow direction F, an uppermost row L1 and a lowermost row L3. And an intermediate row (second row) L2 located between and. Here, the heat transfer tubes forming the bottom row L3 are referred to as heat transfer tubes 26a, the heat transfer tubes forming the middle row L2 are referred to as heat transfer tubes 26b, and the heat transfer tubes forming the top row L1 are referred to as heat transfer tubes 26c. In addition, in each of the rows L1 to L3, the heat transfer tubes 26 are arranged in a row in the vertical direction.

  The heat transfer tubes 26c forming the uppermost row L1 are connected to the indoor liquid side refrigerant distributor 25, and the heat transfer tubes 26a forming the lowermost row L3 are connected to the indoor gas side refrigerant distributor 24. The heat transfer tubes 26a in the lowermost row L3 extend from one end 21A of the indoor heat exchanger 21 to the other end 21B, make a U-turn at the other end 21B, and in the middle row L2, one end of the indoor heat exchanger 21. Return to section 21A. Then, in the one end 21A of the indoor heat exchanger 21, two heat transfer tubes 26b adjacent to each other in the intermediate row L2 are joined, and the joined heat transfer tube 26c is one end in the uppermost row L1. The heat transfer tube 26c that extends back and forth between 21A and the other end 21B and returns to the one end 21A is connected to the indoor liquid-side refrigerant distributor 25.

  In other words, the heat transfer tubes 26 (first heat transfer tubes) extend from one end 21A of the indoor heat exchanger 21 to the other end 21B in the bottom row (third row) L3, and in the middle row (second row) L2. , One end of the indoor heat exchanger 21 that extends from the other end 21B to the one end 21A and is coupled to another heat transfer pipe 26 (second heat transfer pipe) vertically adjacent to each other at the one end 21A. The heat pipe 26 is configured to reciprocate once between the one end 21A and the other end 21B of the indoor heat exchanger 21 in the uppermost row (first row) L1. Further, the three-pronged bend 28 that connects the two heat transfer tubes 26b in the middle row L2 and the heat transfer tubes 26c in the uppermost row L1 is connected with the heat transfer tubes 26c approximately in the vertical direction between the two heat transfer tubes 26b. It has a curved shape. That is, when viewed from the airflow direction F, the heat transfer tube 26c connected to the trifurcated vent 28 is located between the two heat transfer tubes 26b.

  Since the heat transfer tube 26 of the indoor heat exchanger 21 has the above-described configuration, when it functions as a condenser during the heating operation, the refrigerant R32 is an indoor gas side refrigerant distribution as shown by the arrow in FIG. From the container 24, the refrigerant flows into the plurality of heat transfer tubes 26, merges through the lowermost row L3 and the intermediate row L2, and the combined refrigerant makes one round trip in the uppermost row L1 and is discharged to the indoor liquid side refrigerant distributor 25.

  FIG. 8 shows a vertical sectional view of the indoor heat exchanger 21. As shown in FIG. 8, the diameter D of the heat transfer tube 26 is 4≦D≦6 mm, and the vertical pitch Pt (the distance between the centers of the heat transfer tubes 26) of the heat transfer tubes 26 that are vertically adjacent to each other is 11≦Pt≦ It is 17 mm, and the lateral pitch PL of the heat transfer tubes 26 (distance between straight lines passing through the centers of the heat transfer tubes 26 forming each row) is 7≦PL≦11 mm.

  9 is a sectional view taken along line IX-IX in FIG. As shown in FIG. 8, the fin 27 is provided with slits 27A and 27B. The plate thickness t [mm] of the fins 27 and the pitch Pf [mm] of the adjacent fins 27 are set to 0.06≦t/Pf≦0.12. Further, the slit cut-and-raised widths Hs1 and Hs2 [mm] are, for example, 1.2≦Hs1/Hs2≦1., which are slightly different from Pf/3 in consideration of heat transfer performance and ventilation resistance. 6 are configured.

  As described above, the heat transfer tube 26 extends from the one end 21A of the indoor heat exchanger 21 to the other end 21B in the bottom row L3, and from the other end 21B to the one end 21A of the indoor heat exchanger 21 in the middle row L2. And the one heat transfer pipe 26 that is connected to the other heat transfer pipes 26 that are vertically adjacent to each other at one end 21A, and the combined one heat transfer pipe 26 has one end 21A and the other end 21B of the indoor heat exchanger 21 in the uppermost row L1. It is configured to make one round trip between and.

  Therefore, the flow velocity of the refrigerant can be increased and the surface heat transfer coefficient can be increased by merging the refrigerants flowing through the two heat transfer tubes 26 so as to flow through the one heat transfer tube 26.

  Further, in the present embodiment, since R32 is used as the refrigerant, it is possible to reduce the amount of refrigerant circulation used. Therefore, even if the flow velocity of the refrigerant is merged as described above, the flow velocity of the refrigerant is relatively small, and thus the pressure loss can be suppressed.

  On the other hand, in the configuration of the conventional heat exchanger 121 shown in FIG. 10, the heat transfer tube 126 connected to the indoor gas side refrigerant distributor 24 makes a total of 1.5 reciprocations in the rows L1 to L3 to distribute the indoor liquid side refrigerant. It is configured to be connected to the container 25. In this case, when the heat exchanger 121 is used as a condenser, the number of refrigerant passages flowing out from the indoor gas side refrigerant distributor 24 and the number of refrigerant passages flowing into the indoor liquid side refrigerant distributor 25 are the same. Becomes

  Therefore, in order to reduce the number of refrigerant flow paths, it is necessary to reduce the number of heat transfer tubes 126 of the heat exchanger 121, and if the number of heat transfer tubes 126 is reduced, the heat transfer area inside the tubes will decrease. This does not lead to improvement in the performance of the heat exchanger 121.

  Further, as the condensation process progresses from the bottom row L3 to the middle row L2 and the top row L1, the density of the refrigerant increases and the refrigerant flow velocity in the heat transfer tube 126 decreases, so that Since the surface heat transfer coefficient deteriorates, the efficiency of the heat exchanger 121 cannot be maximized.

  Next, the relationship between the degree of supercooling of the indoor heat exchanger 21 that functions as a condenser during heating operation and the COP in the air conditioner 1 using R32 will be described with reference to FIG. 11. For comparison with R32, the relationship between the degree of supercooling of the indoor heat exchanger 21 and COP when R410A is used as the refrigerant of the air conditioner 1 is also shown. It can be seen that in both cases of using R410A and R32, there is a peak in which COP becomes maximum with respect to the degree of supercooling. Then, when the degree of supercooling of R32 is smaller than the peak P1 of COP of R410A, the COP shows peak P2.

  The reason for this is that R32 has a larger specific enthalpy difference, as shown in the refrigeration cycle on the Mollier diagram of FIG.

  The contribution of the condenser outlet supercooling capacity to the capacity is the increment of the specific enthalpy difference indicated by Δhsc_R410A and Δhsc_R32 in FIG. Since R32 has a large specific enthalpy difference Δhc_R32 in the original condenser, the capacity increase rate due to the subcooling Δhsc_R32 tends to be smaller than that of R410A.

  Further, there is a point where the COP decrease exceeds the compression power because it is necessary to increase the compression power by increasing the condensing pressure with respect to the capacity increase by increasing the supercooling degree. Therefore, R32 has the largest COP during heating in that the degree of supercooling is smaller.

  This can exhibit a special effect by using R32 in the configuration of the indoor heat exchanger 21 of the present embodiment shown in FIG. That is, by reducing the degree of supercooling at the outlet of the condenser, it is possible to reduce the temperature difference between the heat transfer tubes 26 adjacent to each other in the uppermost row L1 in which the liquid refrigerant flows in the indoor heat exchanger 21. That is, it is possible to suppress the heat loss between the adjacent heat transfer tubes 26, improve the surface heat transfer coefficient, and improve the performance of the indoor heat exchanger 21.

  Further, as shown in FIG. 11, a larger COP can be obtained when R32 is used than when R410A is used.

  12 and 13 show the results of verifying the above effects. In FIG. 12, the effect of subcooling on COP during heating operation in the air conditioner using R32 as the refrigerant and FIG. 13 using R410A as the refrigerant is shown. Is shown. C1 and C3 in FIGS. 12 and 13 show the influence of the degree of supercooling on COP when R32 and R410A are used in the air conditioner 1 including the indoor heat exchanger 21 of the present embodiment shown in FIG. 7, C2 and C4 show the influence of the degree of supercooling on COP when R32 and R410A are used for the air conditioner including the indoor heat exchanger 121 shown in FIG.

  As shown in FIG. 12, the COP of C1 is high because of the above effect. On the other hand, when R410A is used as the refrigerant in the air conditioner 1 of the present embodiment as shown in FIG. 13, the performance (COP) deteriorates as shown by C3.

  14 and 15 show the influence of the refrigerant circulation amount on the COP during the cooling operation in the air conditioner using R32 or R410A as the refrigerant. C5 and C7 in FIGS. 14 and 15 show the influence of the refrigerant circulation amount on the COP when R32 and R410A are used in the air conditioner 1 including the indoor heat exchanger 21 of the present embodiment shown in FIG. C6 and C8 indicate the influence of the refrigerant circulation amount on the COP when R32 and R410A are used in the air conditioner including the indoor heat exchanger 121 shown in FIG.

  Since there is no heat loss effect in the supercooling region during cooling operation, the effect of the refrigerant flow velocity is dominant. Therefore, due to the difference in the physical properties of R410A and R32, it can be seen that COP is higher in C5 and C7 using R32 and R410A in the air conditioner 1 including the indoor heat exchanger 21 of the present embodiment, particularly in the cooling intermediate capacity range. .

  In order to explain this in detail, the relationship between the mass flux at the time of evaporation, the heat transfer coefficient in the tube, and the pressure loss is shown in FIG. The mass flux, the heat transfer coefficient in the tube, and the pressure loss are shown as average values over the entire length.

  FIG. 16 shows the operating state at the time of intermediate cooling capacity, and shows the pipe heat transfer coefficient and pressure loss due to the mass flux at the time of evaporation by comparing R32 and R410A. Specifically, in both R32 and R410A, the arrangement of the heat transfer tubes 126 in the conventional heat exchanger 121 shown in FIG. 10 (hereinafter referred to as the conventional arrangement) and the heat exchange of the present embodiment shown in FIG. The operating states of the arrangement of the heat transfer tubes 26 in the vessel 21 (hereinafter referred to as the arrangement of the present application) are indicated by dots.

  When the conventional arrangement is changed to the arrangement of the present invention in R410A, the increase of the pressure loss is large, but the increase rate of the heat transfer coefficient is small. However, in R32, the pressure loss when the same capacity is generated is small, so the arrangement of the present invention is changed. Even in such cases, the rate of increase in pressure loss is small and the rate of increase in heat transfer rate is large. Therefore, it can be said that it is more effective in improving the performance of R32 during cooling.

  In addition, in FIG. 17, the heat transfer coefficient and pressure loss in the tube due to the mass flux at the time of condensation are shown by comparison between R32 and R410A. Although the absolute value of the degree of influence of the change in mass flux during condensation is the same as that during evaporation, it can be said that using the array of the present invention for R32 is more effective in improving the performance during heating.

  Further, as described above, since the outer diameter D of the heat transfer tube 26 is 4≦D≦6 mm, as shown in FIG. 18, the increase in ventilation resistance is suppressed and the heat transfer tube pitch (Pt, PL) is reduced. Therefore, the efficiency of the air conditioner 1 (APF: Annual Performance Factor year-round energy efficiency) can be improved. That is, the decrease from the peak of APF can be suppressed within 3%.

  Further, the vertical pitch Pt of the heat transfer tubes 26 that are vertically adjacent to each other is 11≦Pt≦17 mm. Within this range, the efficiency of the air conditioner 1 can be improved while reducing the heat loss effect of the upper and lower heat transfer tubes due to the heat conduction of the fins as shown in FIG.

  That is, the smaller the upper and lower pitch Pt, the larger the loss due to heat conduction of the fins. FIG. 19 shows the effect of the vertical pitch on the APF. When the vertical pitch is 11 mm or less, the effect of heat conduction through the fins is large, so the APF decreases, and conversely, when the vertical pitch is 17 mm or more, the heat transfer tube The reduction in the number of 26 mounted reduces the heat transfer area in the pipe and the fin efficiency, resulting in a decrease in APF. Therefore, it is desirable that the range of the vertical pitch Pt that can secure the reduction rate within 3% from the peak of APF is 11 mm≦Pt≦17 mm.

  Moreover, since the lateral pitch PL of the heat transfer tubes 26 is 7≦PL≦11 mm, the efficiency of the air conditioner 1 can be improved by optimizing the balance between the heat transfer area and the ventilation resistance as shown in FIG. it can. That is, the decrease from the peak of APF can be suppressed within 3%.

Further, the thickness t of the fin 27 [mm], since the relation between the fin pitch Pf [mm] is 0.06 ≦ t / Pf ≦ 0.12, the reduction of heat loss in the supercooling region, as shown in FIG. 21 The APF of the air conditioner 1 can be increased while obtaining the effect. That is, as the fins 27 are thicker and the number of fins is larger, the heat loss effect on the adjacent heat transfer tubes 26 due to the heat conduction effect through the fins 27 is more likely to occur. Loss effect is mitigated. In consideration of this effect, if t/Pf is small when the fin pitch Pf is constant, performance is deteriorated due to a decrease in fin efficiency, and if t/Pf is large, the effect of heat loss is large. Therefore, it is desirable to set 0.06≦t/Pf≦0.12 as a range in which the APF of the air conditioner 1 is within 3% from the peak.

  Further, since the fins 27 are provided with the slits 27A and 27B, the surface heat transfer coefficient becomes high and the fin efficiency becomes relatively low, so that the heat conduction effect to the adjacent heat transfer tubes 26 can be suppressed.

  The present invention is not limited to the above embodiment. Those skilled in the art can make various additions and changes within the scope of the present invention.

  For example, the effect of the path of the heat transfer tubes 26 of the indoor heat exchanger 21 is particularly large in the ceiling-embedded indoor unit 20 because of the large influence of the supercooling region in heating and the degree of freedom of arrangement of the heat transfer tubes 26. large. That is, in the ceiling-embedded indoor unit, as shown in FIGS. 5 and 6, the indoor heat exchanger 21 is arranged around the blower (indoor fan 22) so as to surround the indoor heat exchanger 21 substantially once. There is a limit in depth and height. Therefore, it is effective to improve the performance of the indoor heat exchanger 21 by arranging the heat transfer tubes 26 at a high density, and in addition to the refrigerant passage of the present embodiment that can reduce the mounting space of the refrigerant distributors 24 and 25, By setting the pipe diameter, the vertical pitch, and the lateral pitch within the above ranges, it is possible to realize the high-performance air conditioner 1 that maximizes the characteristics of R32.

  However, the effect can be exhibited even when used in other indoor forms or the outdoor unit 10, and the form is not limited. Therefore, the configuration of the path of the heat transfer tube 26 may be used for other indoor forms or the outdoor heat exchanger 13 of the outdoor unit 10.

  Further, although the fins 27 are provided with the slits 27A and 27B, louvers may be provided. Further, in the above embodiment, the case where R32 is used alone as the refrigerant has been described, but the same effect can be obtained by using a mixed refrigerant containing 70% by weight or more of R32.

  Further, the row configuration of the heat transfer tubes of the indoor heat exchanger may be the row configuration of the heat transfer tubes 26 shown in FIG. That is, as shown in FIG. 22, two heat transfer tubes 26b1 and 26b2 in the middle row L2 and the heat transfer tubes 26c1 in the uppermost row L1 located above the heat transfer tubes 26b1 may be connected. .. The two heat transfer tubes 26b3, 26b4 adjacent to the two heat transfer tubes 26b1, 26b2 and the heat transfer tube 26c3 in the uppermost row L1 are connected in the same manner as in the above-described embodiment. Here, the three-pronged vent 128 connecting the two heat transfer tubes 26b1 and 26b2 and the heat transfer tube 26c1 has the position connected to the heat transfer tube 26c1 in the uppermost row L1 at the middle row L2 as shown in FIG. It is configured to be above the position where it is connected to the two heat transfer tubes 26b. Further, the three-pronged vent 128 is configured such that the refrigerant collides with the branch portion at the branch portion during the air conditioning transporter and is branched, so that the gas-liquid two-phase flow is substantially evenly distributed.

  In the heat transfer tubes (first coupling tubes) 26c1 and 26c2 in which the two heat transfer tubes 26b1 and 26b2 are connected, the heat transfer tube 26c1 extends from one end 21A (FIG. 5) to the other end 21B (FIG. 5). A heat transfer tube 26c2 is arranged below the heat transfer tube 26c1 so as to extend from the other end 21B to the one end 21A. Further, the heat transfer tubes (second coupling tubes) 26c3, 26c4 in which the two heat transfer tubes 26b3, 26b4 are connected are such that the heat transfer tube 26c3 extends from one end 21A to the other end 21B, and the heat transfer tube 26c3 is above the heat transfer tube. 26c4 is arranged so as to extend from the other end 21B to one end 21A. Therefore, the heat transfer tube 26b2 and the heat transfer tube 26b4 extending from the other end portion 21B to the one end portion 21A are arranged so as to be adjacent to each other.

  Therefore, in the row configuration of the heat transfer tubes 26 shown in FIG. 22, since the heat transfer tubes 26b2 and 26b4 extending from the other end 21B to the one end 21A are arranged adjacent to each other, the supercooled refrigerant is Since is continuous up and down, heat loss is less likely to occur at temperatures close to each other. This has the effect of further halving the heat loss, and the APF of the air conditioner 1 can be further increased.

  The row configuration of the heat transfer tubes of the indoor heat exchanger may be the row configuration of the heat transfer tubes 26 shown in FIG. As shown in FIG. 24, in the heat transfer tubes 26c5 and 26c6 to which the plural sets of two heat transfer tubes 26b of the intermediate row L2 are respectively coupled, the heat transfer extending from one end 21A (FIG. 5) to the other end 21B (FIG. 5). The heat pipes 26c5 are gathered and arranged on the upper side, and the heat transfer pipes 26c6 extending from the other end 21B to the one end 21A are gathered and arranged on the lower side. In other words, the heat transfer tubes 26c5 extending from the one end 21A to the other end 21B are arranged adjacent to each other, and the heat transfer tubes 26c6 extending from the other end 21B to the end 21A are arranged adjacent to each other.

  According to this configuration, in addition to the row configuration of the heat transfer tubes 26 shown in FIG. 22, it is possible to further reduce the heat loss between the heat transfer tubes 26 adjacent to each other in the vertical direction in the supercooling region when acting as a condenser. The indoor heat exchanger 21 having higher efficiency can be provided, and the APF of the air conditioner 1 can be increased.

  In the above embodiment, the case where the row configuration of the heat transfer tubes of the indoor heat exchanger is configured in three rows has been described. However, as shown in FIG. 25, the uppermost row in the air flow direction F (first row) ) Even with a two-row configuration consisting of only the heat transfer tubes 26b and 26c of L1 and the intermediate row (second row) L2, the effect of reducing heat loss in the supercooling region when acting as a condenser and the flow velocity on the liquid side The effect of this embodiment that the heat transfer coefficient is improved by the increase can be exhibited. That is, the bottom row L3 may be omitted and only the top row L1 and the middle row L2 may be arranged. In this case, the indoor gas side refrigerant distributor 24 is provided on the other end side 21A of the indoor heat exchanger 21. Further, in the two-row air conditioner, which has a relatively small capacity, the balance between performance and cost can be optimized.

  Further, as shown in FIG. 26, the heat transfer tubes of the indoor heat exchanger may be arranged in four rows. That is, the additional row L4 may be provided downstream of the lowermost row L3 in the airflow direction F. The heat transfer tubes 26d that form the additional row L4 are connected to the indoor liquid-side refrigerant distributor 25, respectively, and extend in the additional row L4 from the other end 21B of the indoor heat exchanger 21 to the one end 21A. , And is connected to the heat transfer tube 26a forming the lowermost row L3. With such a configuration as well, it is possible to achieve the effects of the present embodiment that the influence of heat loss in the supercooling region when acting as a condenser is reduced and the heat transfer coefficient is improved by increasing the flow velocity on the liquid side. When the heat transfer tubes 26 are arranged in four rows or more, the heat transfer area can be increased, so that further performance improvement can be realized.

1: Air conditioner, 20: Indoor unit, 21: Indoor heat exchanger, 21A: One end, 21B: The other end, 26: Heat transfer tube, 27: Fin, 27A, 27B: Slit, L1: Top row, L2 : Middle row, L3: Bottom row

Claims (4)

A first row in which heat transfer tubes are arranged side by side in a direction intersecting the air passage, and a heat transfer tube is arranged in a direction intersecting the air passage on a downstream side of the air passage from the first row. A second row that is provided, and includes a heat exchanger that exchanges heat with the refrigerant by causing a refrigerant to flow in a flow path formed by connecting the heat transfer tubes,
The first heat transfer tube and the second heat transfer tube adjacent to each other in the second row,The refrigerant that has been connected to the one heat transfer tube in the first row at one end and has flowed into the one heat transfer tube isIn the first row, with the one endThe other endIt is configured to make one round trip to and from
  The refrigerant is, R32,
When the heat exchanger acts as a condenser, the subcooling degree is smaller than that at the time when the COP shows a peak in the relationship between the subcooling degree when R410A is used as a refrigerant and the COP (Coefficient of Performance). Driven byAir conditioner. It has a ceiling-embedded cassette type indoor unit,
The air conditioner according to claim 1, wherein the heat exchanger is used in the indoor unit.   The air conditioner according to claim 1 or 2, wherein a distance between centers of the heat transfer tubes adjacent to each other in the intersecting direction in each row is 11 mm or more and 17 mm or less.   The air conditioner according to any one of claims 1 to 3, wherein a distance between straight lines passing through the centers of the heat transfer tubes forming each row is 7 mm or more and 11 mm or less.

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