CN114812010B - Air conditioner and heat exchanger - Google Patents

Abstract

The invention provides an air conditioner and a heat exchanger, which aim to improve heat exchange performance when a non-azeotropic mixed refrigerant is used as a refrigerant for exchange. An air conditioner using a non-azeotropic refrigerant mixture includes a heat exchanger capable of operating as an evaporator and a condenser, wherein a plurality of heat transfer pipes are formed on an evaporator inlet side of a refrigerant inlet side in a case where the heat exchanger operates as an evaporator in a direction of air flow, and a plurality of heat transfer pipes are formed on an evaporator outlet side of a refrigerant outlet side in a case where the heat exchanger operates as an evaporator in a direction of air flow, and the direction of the refrigerant flow on the evaporator inlet side is parallel to the direction of the air flow.

Description

Air conditioner and heat exchanger

Technical Field

The present invention relates to an air conditioner and a heat exchanger.

Background

In an air conditioner, in order to prevent global warming, it is necessary to use a refrigerant having a low GWP (Global Warming Potential: global warming potential). As a low GWP refrigerant, a non-azeotropic mixed refrigerant is proposed in many cases. The non-azeotropic refrigerant mixture is different from the single refrigerant in that it has a temperature gradient depending on the boiling point of each constituent, and therefore, the temperature increases as the dryness increases under the same pressure. Therefore, when the refrigerant and the air are caused to flow in the reverse direction according to the condenser standard and are used as the evaporator, it is difficult to obtain the temperature difference between the air and the refrigerant. In view of this, patent document 1 discloses the following technique: when the heat exchanger is used as an evaporator or a condenser, the heat transfer pipe is provided with a heat transfer pipe that causes the flow of the refrigerant to be parallel flow and a heat transfer pipe that causes the flow of the refrigerant to be reverse flow with respect to the flow of the air.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2002-195675

Disclosure of Invention

Problems to be solved by the invention

In the technique of patent document 1, in a section where the heat exchanger is a reverse flow when operating as an evaporator, the refrigerant temperature is lowered with respect to the heat exchanger row on the leeward side when the evaporation pressure is the same with respect to the heat exchanger row on the windward side, and the refrigerant and the air have a temperature difference, so that a decrease in heat exchange performance can be suppressed. However, in the section that becomes the reverse flow when operating as the evaporator, the heat exchanger becomes the parallel flow when operating as the condenser. Therefore, when the air having heat exchanged between the heat exchanger row on the windward side and the refrigerant gas passes through the heat exchanger row on the leeward side, the temperature difference between the refrigerant and the air may not be ensured. In addition, the following possibilities exist: the air heat-exchanged with the two-phase refrigerant in the heat exchange line on the upwind side cannot be cooled by a single refrigerant because the air cannot be cooled by heat exchange with the refrigerant having low dryness in the heat exchange line on the downwind side. Thus, there are the following problems: the heat exchange performance is greatly reduced, possibly resulting in a reduction in the overall performance of the air conditioner.

The present invention has been made in view of such a problem, and an object of the present invention is to improve heat exchange performance in a case where a zeotropic refrigerant mixture is used as a refrigerant for heat exchange.

Means for solving the problems

The present invention provides an air conditioner using a non-azeotropic refrigerant mixture, comprising a heat exchanger capable of operating as an evaporator and a condenser, wherein a plurality of heat transfer pipes are provided on an evaporator inlet side of a refrigerant inlet side in a case where the heat exchanger operates as the evaporator in an air flow direction, a plurality of heat transfer pipes are provided on an evaporator outlet side of a refrigerant outlet side in a case where the heat exchanger operates as the evaporator in an air flow direction, and a refrigerant flow path is formed such that the direction of the refrigerant flow on the evaporator inlet side is parallel to the air flow direction.

Another aspect of the present invention is a heat exchanger capable of operating as an evaporator and a condenser and using a non-azeotropic refrigerant mixture, wherein a plurality of heat transfer pipes are formed on an evaporator inlet side of a refrigerant inlet side in a case where the heat exchanger operates as the evaporator in an air flow direction, and a single heat transfer pipe is formed on an evaporator outlet side of a refrigerant outlet side in a case where the heat exchanger operates as the evaporator in an air flow direction, and the direction of the refrigerant flow on the evaporator inlet side is parallel to the air flow direction.

Effects of the invention

According to the present invention, heat exchange performance in the case where a zeotropic refrigerant mixture is used as a refrigerant for heat exchange can be improved.

Drawings

Fig. 1 is an overall view of an air conditioner.

Fig. 2 is a schematic diagram showing a heat exchanger.

FIG. 3 is a diagram showing a p-h diagram.

Fig. 4 is a graph showing a change in temperature of the refrigerant in the heat transfer pipe.

Fig. 5 is a graph showing a relationship between the ratio of the heat transfer areas of the two rows and the efficiency increase rate.

Fig. 6 is a diagram schematically showing a heat exchanger according to a second modification.

Fig. 7 is a diagram schematically showing a heat exchanger according to a third modification.

Fig. 8 is a diagram schematically showing a heat exchanger according to a third modification.

Fig. 9 is an explanatory view of flow passage areas in a heat exchanger using flat tubes.

Fig. 10 schematically shows a heat exchanger according to a sixth modification.

In the figure:

1-air conditioner, 10-outdoor unit, 11-compressor, 12-four-way valve, 13-accumulator, 14-outdoor heat exchanger, 15-outdoor fan, 16-outdoor expansion valve, 20-indoor unit, 21-indoor heat exchanger, 22-indoor fan, 23-indoor expansion valve, 30, 40, 41, 42, 43, 44-heat exchanger, 31-heat transfer tube, 32-fin, 311-first refrigerant inlet and outlet, 312-second refrigerant inlet and outlet.

Detailed Description

Fig. 1 is an overall view of 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) system. In the air conditioner 1 of the present embodiment, a non-azeotropic refrigerant mixture is used as the refrigerant for heat exchange. As shown in fig. 1, the air conditioner 1 includes an outdoor unit 10 installed outdoors (outdoors) and an indoor unit 20 installed indoors (in a space where air is conditioned).

The outdoor unit 10 includes a compressor 11, a four-way valve 12, a receiver 13, an outdoor heat exchanger 114, an outdoor fan 15, and an outdoor expansion valve 16. The compressor 11 compresses a low-temperature low-pressure gas refrigerant and discharges a high-temperature high-pressure gas refrigerant. In the outdoor heat exchanger 14, heat exchange is performed between the refrigerant circulating in the refrigeration cycle and the outside air sent from the outdoor fan 15. The outdoor heat exchanger 14 operates as a condenser and an evaporator by switching the four-way valve 12.

The indoor unit 20 has an indoor heat exchanger 21 and an indoor fan 22. In the indoor heat exchanger 21, heat exchange is performed between the refrigerant circulating in the refrigeration cycle and the indoor air sent from the indoor fan 22. The indoor heat exchanger 21 operates as a condenser and an evaporator by switching the four-way valve 12. Further, as another example, when the air conditioner 1 is a multi-unit air conditioner for a building or the like, the indoor unit 20 may further include an indoor expansion valve 23 connected to the refrigerant pipe 2 extending from the indoor heat exchanger 21 and the refrigerant pipe 2 extending from the outdoor expansion valve 16.

In the cooling operation, as indicated by solid arrows, the high-temperature and high-pressure gas refrigerant discharged from the compressor 11 is sent to the outdoor heat exchanger 14, and is condensed into a high-pressure liquid refrigerant by heat exchange with the outdoor air by driving the outdoor fan 15 attached to the outdoor heat exchanger 14. The liquid refrigerant passes through the fully opened outdoor expansion valve 16 and is sent to the indoor unit 20 through the refrigerant pipe 2. Then, the liquid refrigerant is heat-exchanged with the indoor air in the indoor heat exchanger 21 by driving the attached indoor fan 22, and is returned to the compressor 11 through the four-way valve 12 and the accumulator 13 as a low-pressure low-temperature gas refrigerant.

On the other hand, during the heating operation, as indicated by the broken-line arrow, the high-pressure gas refrigerant compressed in the compressor 11 passes through the four-way valve 12, passes through the refrigerant pipe 2, and is supplied to the indoor heat exchanger 21 of the indoor unit 20. The gas refrigerant condenses while heating the indoor air in the indoor heat exchanger 21 to become a liquid refrigerant, and returns to the outdoor unit 10 through the refrigerant pipe 2. Thereafter, the refrigerant passes through the outdoor expansion valve 16, is evaporated by heat exchange with the outdoor air in the outdoor heat exchanger 14, becomes a gas refrigerant, passes through the four-way valve 12 and the accumulator 13, and returns to the compressor 11.

Fig. 2 is a schematic view of a heat exchanger 30 used as the outdoor heat exchanger 14 and the indoor heat exchanger 21. In addition, the X-axis direction (depth direction of the drawing sheet) in the three-dimensional coordinates shown in fig. 2 is defined as the lateral direction of the heat exchanger 30, the Y-axis direction (longitudinal direction of the drawing sheet) is defined as the vertical direction (upper side of the drawing sheet) of the heat exchanger 30, and the Z-axis direction (lateral direction of the drawing sheet) is defined as the depth direction of the heat exchanger 30. The heat exchanger 30 is provided in the outdoor unit 10 and the indoor unit 20 so that the vertical direction of the heat exchanger 30 is along the vertical direction. The direction of the flow of air by the fans (the outdoor fan 15 and the indoor fan 22) is indicated by an arrow a. On the paper surface, the left side in the heat exchanger 30 is the windward side, and the right side is the leeward side.

The heat exchanger 30 has a plurality of heat transfer pipes 31 and a plurality of fins 32. The fins 32 are arranged with their plane direction perpendicular to the X-axis. Only one fin 32 is shown in fig. 2, but a plurality of fins 32 are arranged at constant intervals in the X-axis direction. The plurality of heat transfer pipes 31 are provided so as to pass through the fins 32.

Further, two rows of heat transfer tubes 31 are arranged in the air flow direction a in the region below the heat exchanger 30. A row of heat transfer tubes 31 is disposed in the upper region of the heat exchanger 30 along the air flow direction a. Hereinafter, the region in which two rows of heat transfer tubes are arranged is referred to as two rows of portions 322, and the region in which one row of heat transfer tubes is arranged is referred to as one row of portions 321. The windward row of the two rows 322 is referred to as an windward row 331, and the leeward row is referred to as a leeward row 332. The heat transfer tubes 31 of the one row 321 use heat transfer tubes having a larger inner cross-sectional area M1 than the inner cross-sectional area M2 of the heat transfer tubes 31 of the two rows 322.

All the heat transfer tubes 31 and the fins 32 of the two rows 322 and the one row 321 in the heat exchanger 30 are formed integrally. However, as another example, the heat exchanger 30 may be formed by combining a plurality of units such as a unit of the one row 321, a unit of the upwind row 331, and a unit of the downwind row 332.

The first refrigerant inlet/outlet 311 of the heat transfer pipe 31 is provided on the upstream side, and is connected to an expansion valve (outdoor expansion valve 16) via the refrigerant pipe 2. The second refrigerant inlet/outlet 312 of the heat transfer pipe 31 is provided above the row 321, and is connected to the compressor 11 via the four-way valve 12 and the accumulator 13. In the heat exchanger 30, the first refrigerant inlet and outlet 311 and the second refrigerant inlet and outlet 312 of the heat transfer tube 31 are respectively a refrigerant inlet and a refrigerant outlet when the heat exchanger 30 operates as an evaporator. Hereinafter, the refrigerant inlet and the refrigerant outlet when the evaporator is operated are referred to as an evaporator inlet and an evaporator outlet, respectively.

When the heat exchanger 30 operates as an evaporator, the following refrigerant paths are formed: from the evaporator inlet (first refrigerant inlet/outlet 311) toward the leeward side, from the end 313 of the two rows of parts 322, into the lower end 314 of the one row of parts 321, and toward the evaporator outlet (second refrigerant inlet/outlet 312) through the one row of parts 321. When the heat exchanger 30 operates as a condenser, the refrigerant flows in the refrigerant flow path in a direction opposite to that in the case where the heat exchanger 30 operates as an evaporator.

In such a refrigerant flow path, when the heat exchanger 30 operates as a condenser, the flow of the refrigerant is reversed with respect to the flow of the air at the evaporator inlet side, that is, at the two-row portion 322. Therefore, the heat exchange efficiency when the condenser is operated can be improved. In addition, in the case where the evaporator outlet side is a reverse flow when the heat exchanger 30 is operated as an evaporator as in the conventional example, the flow of the refrigerant at the evaporator outlet side is a parallel flow when the heat exchanger 30 is operated as a condenser, and the heat exchange efficiency is lowered. In contrast, in the present embodiment, the evaporator outlet side is provided as a single row of heat transfer pipes, and thus, the performance as a condenser can be prevented from being degraded.

In the heat exchanger 30, the cross-sectional area M2 of the heat transfer pipe 31 of the two-row portion 322 is designed so that a temperature decrease due to pressure loss is superior to a temperature increase due to a temperature gradient of the zeotropic refrigerant mixture, in order to prevent a decrease in performance as an evaporator. Here, the temperature gradient means that the start temperature and the end temperature of evaporation or condensation in the heat exchanger are different. When the pressure loss becomes large, the temperature decrease due to the pressure loss is advantageous over the temperature increase due to the temperature gradient. In this way, the pressure loss has the advantage that the temperature of the refrigerant gradually decreases as it flows in the heat transfer tube from the evaporator inlet. That is, from the evaporator inlet, the temperature of the refrigerant decreases along the air flow. This makes it possible to make the temperature difference between the air and the refrigerant equal in the direction from the windward side to the leeward side. Therefore, the heat transfer pipes on both windward and leeward sides are effectively used for heat exchange, and the heat exchange efficiency can be improved.

As the heat transfer tubes of the one row 321, heat transfer tubes having a cross-sectional area M1 larger than a cross-sectional area M2 of the two rows 322 are used. That is, the flow path area of the first row portion 321 is larger than the flow path area of the second row portion 322. Thus, in the single row 321, the flow rate of the refrigerant is reduced, and the pressure loss is reduced. Therefore, the temperature rise due to the temperature gradient of the zeotropic refrigerant mixture is more advantageous than the temperature rise due to the pressure loss in the line portion 321, and the decrease in the heat exchange performance as the evaporator due to the increase in the pressure loss in the line portion 321 can be prevented.

FIG. 3 is a diagram showing a p-h diagram. The horizontal and vertical axes of the graph represent specific enthalpy and pressure, respectively. The solid line schematically shows the refrigeration cycle of the present embodiment. In addition, T1, T2 are part of isotherms. Each state of the refrigeration cycle in the figure will be described. In the figure, H1 denotes a compressor suction, H2 denotes a compressor discharge and a condenser inlet, H3 denotes a condenser outlet, H4 denotes an evaporator inlet, and H5 denotes an intermediate portion between an evaporator inlet portion and an evaporator outlet. The refrigerant state changes in this order, and a refrigeration cycle is formed. A non-azeotropic mixed refrigerant is used as the refrigerant for heat exchange, and thus the temperature rises when the refrigerant evaporates with the pressure constant. However, as described above, at the evaporator inlet side, the temperature is reduced because the pressure loss is advantageous with respect to the temperature gradient of the zeotropic refrigerant mixture. The range S1 in fig. 3 is a region on the evaporator inlet side where the temperature of the refrigerant gradually decreases due to the pressure loss. The range S1 corresponds to the heat transfer tubes 31 of the two rows 322 that are parallel-flow when the heat exchanger 30 operates as an evaporator. In addition, the range of S2 is a region on the evaporator outlet side where the temperature gradient of the zeotropic refrigerant mixture is advantageous over the pressure loss and the temperature of the refrigerant gradually rises. The range of S2 corresponds to the heat transfer tubes 31 of the one row 321.

Fig. 4 is a graph showing a change in temperature of the refrigerant in the heat transfer tube due to the flow of the refrigerant. The horizontal and vertical axes of the graph shown in fig. 4 represent the heat transfer pipe length and the temperature of the refrigerant in the heat transfer pipe, respectively. Here, the heat transfer pipe length is a distance of the refrigerant flow path from the evaporator inlet. As shown in fig. 4, in the range (S1) corresponding to the two-row portion 322, the temperature of the refrigerant in the heat transfer pipe gradually decreases from the temperature T11 of the refrigerant at the evaporator inlet due to the pressure loss. Thereafter, the temperature gradient of the zeotropic refrigerant mixture has an advantage in that the temperature of the refrigerant in the heat transfer tube is switched from decreasing to increasing, and in the range (S2) corresponding to the one-row portion 321, the temperature of the refrigerant in the heat transfer tube is gradually increased from the lowest temperature T12 at the two-row portion 322 to the temperature T13 of the refrigerant at the evaporator outlet.

That is, since the temperature of the air decreases from the windward side to the leeward side in the array portion 321 as described above, the temperature change of the refrigerant in the heat transfer pipe can be made the same as the temperature change of the air. This can improve the heat exchange efficiency.

In the present embodiment, as shown in fig. 4, the heat transfer tube 31 (the flow path area of the heat transfer tube 31) is designed such that the refrigerant temperature T13 at the evaporator outlet is higher than the refrigerant temperature T12 at the switching point between the first row 321 and the second row 322 and lower than the temperature Ta of the air. By setting the refrigerant temperature of the line 321 to be higher than T12 in this way, the pressure loss at the line 321 can be reduced, and the suction pressure can be prevented from excessively decreasing. Further, by setting the refrigerant temperature of the row 321 to a temperature lower than the temperature Ta of the air, it is possible to prevent the heat exchange efficiency from decreasing. The temperature of the air is the temperature of the air subjected to heat exchange by the heat exchanger 30, and the temperature of the heat exchanged air varies due to weather or the like. Therefore, in practice, the temperature difference between the temperatures Ta and T12 of the air may be designed to be larger than the temperature difference between T13 and T12 under all the temperature conditions available in the region where the air conditioner 1 is installed.

Furthermore, the heat exchanger 30 is preferably designed such that the evaporator inlet and the evaporator outlet are at equal temperatures. By designing the flow passage areas of the heat transfer tubes of the first row portion 321 and the second row portion 322, the temperatures of the evaporator inlet and the evaporator outlet can be equalized. In this way, by equalizing the temperatures of the evaporator inlet and the evaporator outlet, the heat exchange efficiency of the entire heat exchanger 30 can be improved.

The heat exchanger 30 is formed such that the heat transfer area corresponding to the two rows 322 is equal to or smaller than the heat transfer area corresponding to the one row 321. Here, the heat transfer area of the two rows 322 is the surface area of the fins 32 of the two rows 322, and the heat transfer area of the one row 321 is the surface area of the fins 32 of the one row 321.

The relationship between the heat transfer areas will be described below. Fig. 5 is a graph showing a relationship between the ratio of the heat transfer areas of the two rows and the efficiency increase rate. The horizontal axis represents the ratio of the heat transfer areas of the two rows, and the vertical axis represents the efficiency increase rate. Here, the ratio of the heat transfer areas of the two rows is a ratio of the heat transfer areas of the two rows to the heat transfer area of the entire heat exchanger 30. The efficiency increase rate is an energy efficiency increase rate of a heat exchanger in which the evaporator inlet side is made to flow in parallel as in the present embodiment, with reference to a heat exchanger in which the evaporator inlet side and the evaporator outlet side are both made to flow in reverse. The same zeotropic refrigerant mixture was used as the refrigerant. As the energy efficiency, the value of APF (Annual Performance Factor: annual energy consumption efficiency) was used.

Line Q shown in fig. 5 shows a change in the efficiency increase rate obtained by simulation when a certain zeotropic refrigerant mixture is used. Similarly, simulation and experiments were performed using a plurality of zeotropic refrigerant mixtures having different temperature gradients. As a result of these simulations and experiments, it was found that a significant increase in efficiency was observed in the range of 10% to 50% of the heat transfer area of the two-row portion. It is also known that the range in which the efficiency increase rate takes the highest value is the range in which the ratio of the heat transfer areas of the two rows is 20% to 35%.

From the above, the heat exchanger 30 is preferably formed such that the heat transfer area of the two rows 322 is equal to or smaller than the heat transfer area of the one row 321. It is more preferable that the ratio of the two-row portion heat transfer area is within a range P1 of 10% to 50%. Further, it is more preferable that the heat exchanger 30 is formed such that the ratio of the heat transfer area of the two rows is within a range P2 of 15% to 40%. The range of 15% to 40% is a range in which the efficiency increase rate is maximized, and the range includes a margin.

In the case where the length of the fin 32 in the width direction is constant regardless of the position of the fin 32 in the up-down direction, the ratio of the heat transfer area is equal to the ratio of the fin 32 in the height direction. Here, the width direction is a direction corresponding to the direction a in which the air flows.

Further, it is preferable that the width of the fins 32 in the one-row portion 321 is equal to the width of the fins 32 in the two-row portion 322. Here, the lateral width of the fin 32 is the width (length) of the fin 32 along the air flow direction a. By making the width of the fins 32 in the first row 321 equal to the width of the fins 32 in the second row 322 in this manner, it is possible to compensate for a decrease in heat exchange efficiency of the first row 321 caused by the fact that the number of heat transfer tubes 31 included in the first row 321 is smaller than the predetermined height of the second row 322.

Further, for example, in the case where the width of the fins 32 of the one row portion 321 is smaller than the width of the fins 32 of the two row portion 322, the heat exchange performance at the one row portion 321 is lowered. On the other hand, in the case where the width of the fins 32 of the first row 321 is larger than the width of the fins 32 of the second row 322, frost adheres to the fins 32 of the first row 321 at a portion longer than the fins 32 of the second row 322, and there is a possibility that defrosting is not possible and breakage of the heat exchanger 30 is caused. Therefore, the difference in the width of the fins 32 of the first row 321 and the width of the fins of the second row 322 does not cause a decrease in heat exchange performance or a degree of frost.

When the upwind row 331 and the downwind row 332 of the two rows 322 are formed as separate units, the total value of the width of the fins of the upwind row 331 and the width of the fins of the downwind row is set to the width of the fins of the two rows 322, and the width of the fins of the two rows 322 and the width of the fins of the one row are set to be equal. When the heat transfer tubes are formed of a plurality of cells, the total value of the widths of the fins of the cells is set to the width of the fins in the heat transfer tubes.

The zeotropic refrigerant mixture used in the air conditioner 1 of the present embodiment is preferably a refrigerant having a temperature gradient of 2 ℃ or higher at the time of heat exchange. By using a non-azeotropic refrigerant mixture having a temperature gradient of 2 ℃ or higher, heat exchange can be efficiently performed even in a region where the temperature gradient is advantageous over the pressure loss when the evaporator is operated. The zeotropic refrigerant mixture is preferably a refrigerant having a temperature gradient of 7 ℃ or less during heat exchange. This is because if the temperature gradient exceeds 7 ℃, the possibility of frost adhering to the heat exchanger 30 increases due to a decrease in the temperature of the refrigerant at the time of heat exchange. That is, by using a non-azeotropic refrigerant mixture having a temperature gradient of 7 ℃ or less, the adhesion of frost can be prevented. Examples of the zeotropic mixed refrigerant include a refrigerant such as R32 or R125 for securing heat exchange performance, and a mixed refrigerant such as HFO-1234yf, HFO-1234ze (E), HFO-1123, HFO1132a, HFO-1132 (E) R744, R290, R600a, or CF3I (trifluoroiodomethane) having a low GWP. In the mixed refrigerant of these refrigerants, the mixing ratio is adjusted so as to fall within the above temperature gradient range.

As shown in fig. 2, the evaporator outlet of the heat exchanger 30 is provided above the evaporator inlet in the vertical direction in a state of being provided in the outdoor unit 10 and the indoor unit 20. In the heat exchanger 30, frost may adhere to the fins 32. In this case, the heat exchanger 30 is operated as a condenser, and defrosting is performed. In the case of defrosting, on the condensation inlet side (evaporator outlet side), the refrigerant is difficult to flow, and the frost is difficult to melt. On the other hand, the flow rate on the condensation outlet side (evaporator inlet side) is high, and the refrigerant easily flows, so that the frost easily melts. In the heat exchanger 30 of the present embodiment, the evaporator outlet side is provided above the evaporator inlet side in the vertical direction as described above so that the flow rate at the evaporator inlet side is higher than the flow rate at the evaporator outlet side. This can prevent frost from remaining without melting during defrosting at the lower side of the heat exchanger 30. Further, ice growth at a drain pan (not shown) for receiving condensed water and a drain port (not shown) for condensed water can be prevented from being increased at the lower side of the heat exchanger 30, and water generated by defrosting can not be drained.

As described above, in the heat exchanger 30 used as the outdoor heat exchanger 14 and the indoor heat exchanger 21 of the air conditioner 1 of the present embodiment, one row of heat transfer tubes is provided on the evaporator inlet side, and two rows of heat transfer tubes are provided on the evaporator outlet side. When the heat exchanger 30 is operated as an evaporator, the flow of the refrigerant on the inlet side of the evaporator is parallel, and the flow passage area of the two rows is larger than that of the one row. Thus, the heat exchanger 30 can prevent the heat exchange performance from being lowered, both when operating as an evaporator and when operating as a condenser. That is, the heat exchange performance of the heat exchanger in the case where the zeotropic mixed refrigerant is used as the refrigerant for heat exchange can be improved.

In the present embodiment, the heat exchanger 30 is used as the outdoor heat exchanger 14 and the indoor heat exchanger 21, but as a first modification, the heat exchanger 30 may be used for at least one of the outdoor heat exchanger 14 and the indoor heat exchanger 21.

Next, as a second modification, the flow passage area of the heat transfer pipe 31 designed to be the one row portion 321 may be larger than the flow passage area of the two row portions 322, and the specific configuration used for this is not limited to the embodiment. For example, the number of refrigerant channels (passages) in the first row 321 may be larger than the number of passages in the second row 322. Fig. 6 schematically shows a heat exchanger 40 according to a second modification. In the heat exchanger 40, heat transfer tubes 31 having equal inner cross-sectional areas are used in the first row portion 321 and the second row portion 322. In the heat exchanger 40, two refrigerant paths (two paths) are branched from the end 313 of the single row 321. One of the two refrigerant flow paths flows from the upper end 314a to the second refrigerant inlet/outlet 312a in the one row 321, and the other flows from the lower end 314b to the refrigerant outlet 312b in the one row 321. In this way, in addition to the use of heat transfer tubes having the same cross-sectional areas for the first row 321 and the second row 322, the flow passage area of the first row 321 can be made larger than the flow passage area of the second row 322 by increasing the number of passages of the first row 321.

In the case of using the heat transfer tubes 31 having the same cross-sectional area, the number of passages in the single row 321 may be three or more. As another example, the cross-sectional area of the heat transfer tube 31 in the first row 321 may be larger than the cross-sectional area of the heat transfer tube 31 in the second row 322, and the number of passages in the second row 322 may be larger than the number of passages in the first row, so that both the cross-sectional area of the heat transfer tube and the number of passages may be used as parameters to achieve the target pressure loss.

As a third modification, the shape of the heat transfer pipe is not limited to a round pipe having a circular cross section as shown in fig. 2. For example, a flat tube having a flat cross section may be used as the heat transfer tube. As another example, a groove may be formed inside the pipe like a pipe with an inner surface groove. Fig. 7 is a view showing a heat exchanger 41 including flat tubes. By using a flat tube as the heat transfer tube 401, more heat transfer tubes can be arranged at the same height than in the case of using a round tube having a flow path area equal to that of the flat tube. Further, the use of flat tubes can shorten the distance from the heat transfer tube to the windward and leeward ends 402a, 402b of the fins 402, and thus can improve the heat exchange efficiency as compared with round tubes. In this case, the two rows of flat tubes may be formed by fixing two rows of flat porous tubes, or the two rows of flat tubes may be integrally formed. The heat exchanger 41 may be formed by fixing a unit of one row and a unit of two rows in the vertical direction, or the heat exchanger 41 may be formed integrally with the unit of one row and the unit of two rows.

In addition, in the case of a round tube other than a flat tube, the heat transfer tubes may be formed such that the tube width of the heat transfer tubes of the first row 321 is longer than the tube width of the heat transfer tubes of the second row 322. Here, the tube width is the width of the heat transfer tube in the direction along the direction a of the air flow. In the example of fig. 7, the heat transfer tubes 401 of the first row 321 have a tube width N1, and the heat transfer tubes 401 of the second row 322 have a tube width N2. By forming the heat transfer tubes such that the tube width of the first row 321 is longer than the tube width of the second row 322 in this way, it is possible to prevent a decrease in heat exchange efficiency caused by a longer distance from the heat transfer tube 401 to the ends 402a, 402b of the fin 402 in the first row 321.

In the heat exchanger using the flat tube, the cross-sectional area of the heat transfer tube and the number of branch passages may be designed as parameters so as to have a flow path area corresponding to the target pressure loss. As shown in fig. 8, in the heat exchanger 42, the flow passage area can be adjusted by using flat tubes and using branch headers 421a and 421b. In the heat exchanger 42 using the flat porous tube, the flat tube 422 and the fins 423 are integrally formed, and branch headers 421a, 421b are arranged at both ends thereof. In the heat exchanger 42, the refrigerant can be branched to a plurality of refrigerant tubes (flat tubes) at a time by using the branch headers 421a and 421b. In this way, not only the cross-sectional area of the heat transfer tube to be used but also the total flow path area, that is, the pressure loss can be designed to be a target value by adjusting the number of branches. The number of branched heat transfer tubes is increased on the outlet side of the evaporator than on the inlet side of the evaporator, so that the flow velocity in the heat transfer tubes can be reduced, and the pressure loss can be reduced. In addition, by sequentially increasing the number of heat transfer tubes on the outlet side of the evaporator, the pressure loss can be reduced in the same manner.

As a fourth modification, the number of heat transfer tubes at the lower side of the heat exchanger is not limited to two, as long as the number is plural. As another example, the heat exchanger may have, for example, three rows of heat transfer tubes. Fig. 9 is a diagram showing a heat exchanger 43 including three rows of heat transfer tubes 431. Fig. 9 shows an example in which the heat transfer tube is a flat tube. In this case, the refrigerant flow path is also connected to a row of heat transfer tubes from the evaporator inlet via refrigerant tubes on the windward side, the center, and the leeward side in this order. This makes it possible to make the direction of the flow of the refrigerant on the inlet side of the evaporator parallel to the flow of the air.

As a fifth modification, the positional relationship between the evaporator outlet and the evaporator inlet in the X-axis direction and the Z-axis direction is not limited to the embodiment, as long as the evaporator outlet is provided above the evaporator inlet in the vertical direction. For example, the upper portion of the heat exchanger 30 may be inclined upward, and the evaporator outlet may be provided upward from the evaporator inlet.

As a sixth modification, as in the heat exchanger 44 shown in fig. 10, the cross-sectional areas of the heat transfer tubes of the first row 321 and the second row 322 may be made equal. In this case, by providing the evaporator outlet side as a single row of heat transfer pipes, it is possible to prevent the performance as a condenser from being degraded.

The present invention is not limited to the specific embodiment, and various modifications and changes can be made within the scope of the present invention described in the claims by applying the modification of one embodiment to another embodiment, for example.

Claims (13)

1. An air conditioner using a non-azeotropic refrigerant mixture, characterized in that,

Comprises a heat exchanger capable of operating as an evaporator and a condenser,

A plurality of heat transfer tubes are provided on an evaporator inlet side of a refrigerant inlet side in a case where the heat exchanger is operated as the evaporator in a direction along which air flows,

A row of heat transfer pipes is formed on the evaporator outlet side of the refrigerant outlet side in the case where the heat exchanger operates as the evaporator in the air flow direction,

The refrigerant flow path is formed such that the direction of the refrigerant flow at the inlet side of the evaporator is parallel to the air flow,

The evaporator outlet is provided above the evaporator inlet in the vertical direction.

2. The air conditioner according to claim 1, wherein,

The heat exchanger is formed such that the flow path area of the one row of heat transfer pipes is larger than the flow path area of the plurality of rows of heat transfer pipes.

3. An air conditioner according to claim 2, wherein,

A heat transfer tube having a larger cross-sectional area than the plurality of heat transfer tubes is used as the one row of heat transfer tubes.

4. An air conditioner according to claim 2, wherein,

Heat transfer tubes having the same cross-sectional area are used as the one row of heat transfer tubes and the plurality of rows of heat transfer tubes,

The number of refrigerant flow paths in the one row of heat transfer tubes is greater than the number of refrigerant flow paths in the plurality of rows of heat transfer tubes.

5. The air conditioner according to any one of claims 1 to 4, wherein,

The heat exchanger is formed such that a heat transfer area corresponding to the plurality of heat transfer tubes is equal to or smaller than a heat transfer area corresponding to the one heat transfer tube.

6. The air conditioner according to any one of claims 1 to 4, wherein,

The width of the fins corresponding to the one row of heat transfer tubes is equal to the width of the fins corresponding to the plurality of rows of heat transfer tubes.

7. The air conditioner according to claim 1, wherein,

The heat transfer tube is formed such that the temperature of the zeotropic refrigerant at the evaporator outlet is higher than the lowest temperature at the heat transfer tube array and is lower than the temperature of the air which exchanges heat with the zeotropic refrigerant.

8. The air conditioner according to any one of claims 1 to 4, wherein,

The tube width of the one heat transfer tube in the air flow direction is larger than the tube width of the plurality of heat transfer tubes.

9. The air conditioner according to any one of claims 1 to 4, wherein,

The one of the heat transfer tubes is a flat tube.

10. The air conditioner according to any one of claims 1 to 4, wherein,

The heat transfer tubes are flat tubes.

11. The air conditioner according to any one of claims 1 to 4, wherein,

The non-azeotropic refrigerant mixture is a refrigerant having a temperature gradient of 2 ℃ or higher.

12. The air conditioner according to any one of claims 1 to 4, wherein,

The non-azeotropic refrigerant mixture is a refrigerant having a temperature gradient of 7 ℃ or less.

13. A heat exchanger capable of operating as an evaporator and a condenser and using a non-azeotropic refrigerant mixture, characterized in that,

A plurality of heat transfer tubes are formed on an evaporator inlet side of a refrigerant inlet side in a case where the heat exchanger is operated as the evaporator in a direction in which air flows,

A row of heat transfer pipes is formed on the evaporator outlet side of the refrigerant outlet side in the case where the heat exchanger operates as the evaporator in the air flow direction,

The direction of the refrigerant flow at the inlet side of the evaporator is parallel flow with respect to the flow of air,

The evaporator outlet is provided above the evaporator inlet in the vertical direction.