AIR CONDITIONING

Abstract

An air conditioner (100) comprises an outdoor unit (101), an indoor unit (102), and a first line (111) and a second line (112) connecting the outdoor unit (101) to the indoor unit (102). The outdoor unit (101) comprises a first heat exchanger (3), a first expansion valve (41), a compressor (1), and a switching device (2) configured to change between a cooling state and a heating state. The indoor unit (102) comprises a second heat exchanger (6), a second expansion valve (42), and a third heat exchanger (51).The third heat exchanger (51) is configured to exchange heat between the first refrigerant and the second refrigerant when the temperature of the first refrigerant is higher than the temperature of the second refrigerant, and not to exchange heat between the first refrigerant and the second refrigerant when the temperature of the first refrigerant is lower than the temperature of the second refrigerant, wherein the first refrigerant flows between the second expansion valve (42) and the first line (111) and the second refrigerant flows between the second expansion valve (42) and the second heat exchanger (6).

Description

TECHNICAL AREA

[0001] The present disclosure relates to an air conditioning system and in particular to an air conditioning system with a plurality of expansion valves. BACKGROUND ON THE STATE OF THE TECHNOLOGY

[0002] In recent years, with the aim of reducing the overall global warming potential (GWP) and the use of highly flammable refrigerants in air conditioning systems, there has been a growing demand to reduce the amount of refrigerant in such systems. Japanese Patent No. 6878612 (PTL 1), for example, discloses an air conditioning system capable of reducing the total amount of refrigerant. In this system, an expansion valve is installed at each of the upstream and downstream positions of a liquid-side line between the lines connecting an indoor and an outdoor unit. The opening degree of each expansion valve is adjusted to bring the refrigerant in the liquid-side line into a two-phase state, thereby reducing the total amount of refrigerant in the air conditioning system. REFERENCE LIST PATENT LITERATURE

[0003] PTL 1: Japanese Patent No. 6878612 SUMMARY OF THE INVENTIONAL PROBLEM

[0004] In an air conditioning system where expansion valves are provided both upstream and downstream of the liquid-side line between the lines connecting the indoor and outdoor units, the amount of refrigerant in the entire air conditioning system can be reduced by bringing the refrigerant in the liquid-side line into a two-phase state during both cooling and heating conditions.

[0005] At this point, however, the refrigerant, in its two-phase state, flows through the expansion valve located downstream of the liquid-side line, causing a pressure differential before and after this downstream expansion valve. This pressure differential increases the pressure within the liquid-side line, leading to the problem that it is not possible to achieve a sufficient reduction in the refrigerant charge by bringing the refrigerant within the liquid-side line into a two-phase state.

[0006] The present disclosure was made to solve the problem described above, and one objective of it is to reduce the amount of refrigerant within a liquid-side line between lines connecting an indoor unit and an outdoor unit in an air conditioning system in which an expansion valve is provided at each of the upstream and downstream positions of the liquid-side line. SOLUTION TO THE PROBLEM

[0007] An air conditioning system according to the present disclosure comprises: an outdoor unit; an indoor unit; and a first duct and a second duct, each connecting the indoor unit to the outdoor unit. The outdoor unit comprises: a first heat exchanger; a first expansion valve connected between the first heat exchanger and the first duct; a compressor; and a switching device connected between the first heat exchanger, the second duct, and the compressor.The switching device is configured to toggle between a first state and a second state, the first state being a state in which an intake port of the compressor is connected to the second line and an outlet port of the compressor is connected to the first heat exchanger, and the second state being a state in which the intake port of the compressor is connected to the first heat exchanger and the outlet port of the compressor is connected to the second line. The indoor unit comprises: a second heat exchanger connected to the second line; and a second expansion valve connected between the second heat exchanger and the first line. The air conditioning system also comprises at least one of a third heat exchanger in the indoor unit and a fourth heat exchanger in the outdoor unit.The third heat exchanger is configured to exchange heat between a first refrigerant and a second refrigerant when the temperature of the first refrigerant is higher than the temperature of the second refrigerant, and not to exchange heat between the first refrigerant and the second refrigerant when the temperature of the first refrigerant is lower than the temperature of the second refrigerant, wherein the first refrigerant is a refrigerant flowing between the second expansion valve and the first line, and the second refrigerant is a refrigerant flowing between the second expansion valve and the second heat exchanger.The fourth heat exchanger is configured to exchange heat between a third refrigerant and a fourth refrigerant when the temperature of the third refrigerant is higher than the temperature of the fourth refrigerant, and not to exchange heat between the third refrigerant and the fourth refrigerant when the temperature of the third refrigerant is lower than the temperature of the fourth refrigerant, wherein the third refrigerant is a refrigerant flowing between the first expansion valve and the first line, and the fourth refrigerant is a refrigerant flowing between the first expansion valve and the first heat exchanger. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0008] According to the present disclosure, in an air conditioning system in which an expansion valve is provided at each of the upstream and downstream positions of the liquid-side line between the lines connecting the indoor unit and the outdoor unit, the amount of refrigerant in the liquid-side line can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a representation that schematically shows an example of the overall configuration of an air conditioning system according to the present first embodiment. Fig. Figure 2 is a representation that schematically shows an example of the overall configuration of a first comparison example. Fig. Figure 3 is a Mollier diagram that was created during a cooling process in the first comparison example. Fig. Figure 4 is a Mollier diagram that was created during a cooling process in the air conditioning system according to the present first embodiment. Fig. Figure 5 is a Mollier diagram that was created during a heating process in a second comparative example. Fig. Figure 6 is a Mollier diagram that was created during a heating process in the air conditioning system according to the present first embodiment. Fig. Figure 7 is a representation that schematically shows an example of the overall configuration of an air conditioning system according to the present second embodiment. Fig. Figure 8 is a Mollier diagram that was created during a cooling process in the air conditioning system according to the present second embodiment. Fig. Figure 9 is a Mollier diagram that was created during a heating process in the air conditioning system according to the present second embodiment. Fig. Figure 10 is a representation that schematically shows an example of an overall configuration of an air conditioning system according to the present third embodiment. Fig. Figure 11 is a Mollier diagram created during a cooling process in the air conditioning system according to the present third embodiment. Fig. Figure 12 is a Mollier diagram created during a heating process in the air conditioning system according to the present third embodiment. Fig. Figure 13 shows an example of detailed configurations of a third heat exchanger and a fourth heat exchanger. Fig. Figure 14 shows another example of the detailed configurations of the third and fourth heat exchangers. Fig. 15 is a cross-sectional view of an evaporator unit along a line XV-XV in Fig. 14. DESCRIPTION OF THE EXECUTION FORMS

[0009] Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. Although a multitude of embodiments are described below, at the time of filing the present application it was originally intended to combine the configurations described in the embodiments in a suitable manner. In the accompanying drawings, identical or corresponding parts are designated with the same reference numerals, and their description is not repeated. First embodiment

[0010] Fig. Figure 1 is a schematic representation showing an example of the overall configuration of an air conditioner 100 according to the present embodiment. The air conditioner 100 comprises an outdoor unit 101, an indoor unit 102, a first line 111 (a liquid-side connection line), and a second line 112 (a gas-side connection line). The outdoor unit 101 and the indoor unit 102 are connected by a first line 111 and a second line 112. The air conditioner 100 is filled with a refrigerant (R410A, R32, R290, R454, or similar) that undergoes a phase change.

[0011] The outdoor unit 101 comprises a compressor 1, a switching device 2, a first heat exchanger (an outdoor heat exchanger) 3, and a first expansion valve 41. The first expansion valve 41 is connected between the first heat exchanger 3 and the first line 111. The switching device 2 is connected between the first heat exchanger 3, the second line 112, and the compressor 1. In the present embodiment, the switching device 2 consists of a four-way valve.

[0012] The switching device 2 is configured to switch between a cooling state (the first state) and a heating state (the second state). In the cooling state, an intake port of compressor 1 is connected to the second line 112 and an outlet port of compressor 1 is connected to the first heat exchanger 3. In the heating state, the suction port of compressor 1 is connected to the first heat exchanger 3 and the pressure port of compressor 1 is connected to the second line 112. The in Fig. The switching device 2 shown in Figure 1 is in a cooling state.

[0013] The indoor unit 102 contains a second heat exchanger (an indoor heat exchanger) 6 and a second expansion valve 42. The second heat exchanger 6 is connected to the second line 112. The second expansion valve 42 is connected between the second heat exchanger 6 and the first line 111. Specifically, the second heat exchanger 6 and the second expansion valve 42 are arranged in this order from the second line 112 to the first line 111.

[0014] Furthermore, according to the present embodiment, the indoor unit 102 includes a third heat exchanger (refrigerant-refrigerant heat exchanger) 51.

[0015] The third heat exchanger 51 comprises: a heat exchanger unit 51a, arranged in a flow path connecting the second expansion valve 42 and the first line 111; and a heat exchanger unit 51b, arranged in a flow path connecting the second expansion valve 42 and the second heat exchanger 6. The third heat exchanger 51 has a so-called thermal diode function: it transfers heat from heat exchanger unit 51a to heat exchanger unit 51b and it transfers no or less heat from heat exchanger unit 51b to heat exchanger unit 51a. In particular, the third heat exchanger 51 is configured when the temperature of the first refrigerant in heat exchanger unit 51a is higher than that of the second refrigerant in heat exchanger unit 51b, heat is transferred between the heat exchanger units 51a and 51b (i.e.,between the first refrigerant and the second refrigerant) and, if the temperature of the first refrigerant is lower than that of the second refrigerant, not to exchange any heat between the heat exchange units 51a and 51b.

[0016] In the air conditioning system 100 according to the present embodiment, a total sum V1 (= Ve1 + Vp1) of a flow path volume Ve1 within the first heat exchanger 3 and a volume Vp1 of a flow path connecting the first heat exchanger 3 with the first expansion valve 41 (a flow path between points M1 and M2) is greater than a total sum V2 (= Ve2 + Vp2) of the volume Ve2 of a flow path in the second heat exchanger 6 and the volume Vp2 of a flow path connecting the second heat exchanger 6 with the second expansion valve 42 (a flow path between points M6 and M5) (V1 > V2).

[0017] In the air conditioning system 100 according to the present embodiment, the cooling operation and the heating operation can be switched by changing the state of the switching device 2.

[0018] During cooling operation, the switching device 2 is switched to the aforementioned cooling state (the first state), and the compressor 1 is operated. The gaseous refrigerant in the compressor 1 is compressed to a state of high temperature and high pressure and expelled from the compressor 1 to flow through the switching device 2 into the first heat exchanger 3. The gaseous refrigerant flowing into the first heat exchanger 3 exchanges heat and condenses into a liquid refrigerant. The liquid refrigerant flows into the first expansion valve 41 and is expanded by the first expansion valve 41 into a low-pressure, two-phase state (a gas-liquid mixture).The refrigerant, in its two-phase state, flows in this sequence through the first line 111, the heat exchanger unit 51a, the second expansion valve 42, and the heat exchanger unit 51b, then exchanges heat in the second heat exchanger 6, thereby evaporating into a gaseous refrigerant. The gaseous refrigerant then flows through the second line 112 and the switching device 2 in this sequence to be returned to the compressor 1.

[0019] During cooling operation, the refrigerant is decompressed as it flows through the second expansion valve 42. Thus, the pressure of the refrigerant in the heat exchanger unit 51a before it flows through the second expansion valve 42 (this refrigerant is hereinafter also referred to as the "first refrigerant") becomes higher than the pressure of the refrigerant in the heat exchanger unit 51b after it flows through the second expansion valve 42 (this refrigerant is hereinafter also referred to as the "second refrigerant"). Consequently, the temperature of the first refrigerant in the heat exchanger unit 51a becomes higher than the temperature of the second refrigerant in the heat exchanger unit 51b. This allows the heat from heat exchanger unit 51a to be transferred to heat exchanger unit 51b in the third heat exchanger 51.

[0020] During the heating process, the switching device 2 is switched to the aforementioned heating state (the second state) and the compressor 1 is operated. The gaseous refrigerant in the compressor 1 is compressed to a state of high temperature and high pressure and expelled from the compressor 1 to flow via the switching device 2 and the second line 112 into the second heat exchanger 6. The gaseous refrigerant flowing into the second heat exchanger 6 exchanges heat and condenses into liquid refrigerant. The liquid refrigerant flows through the heat exchanger unit 51b into the second expansion valve 42 and is decompressed by the second expansion valve 42 into a low-pressure two-phase state (gas-liquid mixture).The refrigerant in its two-phase state flows in this sequence through the heat exchanger unit 51a, the first line 111, and the first expansion valve 41, then exchanges heat in the first heat exchanger 3, thereby evaporating into gaseous refrigerant. The gaseous refrigerant then flows through the switching device 2 and is returned to the compressor 1.

[0021] During heating operation, the refrigerant is decompressed as it flows through the second expansion valve 42. This causes the pressure of the second refrigerant in the heat exchanger unit 51b, before it flows through the second expansion valve 42, to be higher than the pressure of the first refrigerant in the heat exchanger unit 51a after it has flowed through the second expansion valve 42. Consequently, the temperature of the second refrigerant in the heat exchanger unit 51b is higher than the temperature of the second refrigerant in the heat exchanger unit 51a. However, due to the thermal diode function of the third heat exchanger 51, little or no heat is exchanged from the heat exchanger unit 51b to the heat exchanger unit 51a.

[0022] Fig. Figure 2 is a schematic representation which, as a first comparative example with regard to the present embodiment, shows an example of the overall configuration of an air conditioning system corresponding to the air conditioning system 100 from which the third heat exchanger 51 has been removed.

[0023] Fig. 3 is a Mollier diagram, which is drawn during a cooling process in the Fig. The first comparative example shown in section 2 was obtained. Fig. Figure 4 is a Mollier diagram that was created during a cooling process in the air conditioning system 100 according to the present first embodiment. In each of the Mollier diagrams in the Fig. 3 and Fig. Figure 4 represents the enthalpy (the amount of heat of the refrigerant) on the horizontal axis and the pressure of the refrigerant on the vertical axis. Curve L1 shows a saturated liquid line and curve L2 a saturated vapor line. The values ​​in the Fig. 3 and Fig. The four reference symbols shown, labeled M1 to M6, correspond to the respective reference symbols in the Fig. 1 and Fig. 2. The same applies to the Mollier diagrams described below.

[0024] In the first comparative example, the third heat exchanger 51 is not included. Thus, during cooling operation, as in Fig. Figure 3 shows a pressure difference before and after the second expansion valve 42, so that the pressure in the first line 111 reaches a high value.

[0025] In contrast, in the air conditioning system 100 according to the present embodiment, the third heat exchanger 51 is used for heat exchange between the heat exchanger units 51a and 51b, the dryness of the refrigerant at point M4 decreases, the flow velocity of the refrigerant at the inlet of the second expansion valve 42 decreases, and thus the pressure difference before and after the second expansion valve 42 decreases. Consequently, as in Fig. Figure 4 shows that the pressure in the first line 111 is lower than in the one shown in Fig. The first comparative example shown in Figure 3 is reduced. In this way, in the air conditioning system 100 according to the present embodiment, the third heat exchanger 51 is used to make it possible to reduce the pressure within the first line 111 during cooling operation and thereby increase the proportion of gaseous refrigerant within the first line 111. This allows the amount of refrigerant in the first line 111 to be reduced during cooling operation.

[0026] Fig. Figure 5 is a Mollier diagram obtained during a heating process in a case where the third heat exchanger 51 of the air conditioning system 100 according to the present embodiment is replaced by a simple heat exchanger without a thermal diode function, as a second comparative example in relation to the present embodiment. Fig. Figure 6 is a Mollier diagram that was created during a heating process in the air conditioning system 100 according to the present embodiment.

[0027] In the second comparative example, the third heat exchanger 51 does not have a thermal diode function, so that during heating operation, heat exchange takes place between the heat exchanger units 51a and 51b in the third heat exchanger 51. This causes the temperature of the refrigerant at point M5 to drop and the density of the refrigerant to increase, thus reducing the flow velocity of the refrigerant at the inlet of the second expansion valve 42. This makes it more difficult to decompress the refrigerant at the second expansion valve 42 and therefore impairs the controllability of the second expansion valve 42.

[0028] The refrigerant can also be decompressed through the first expansion valve 41 instead of the second expansion valve 42. However, if the refrigerant is in a two-phase state at the inlet of the first expansion valve 41, the controllability of the first expansion valve 41 deteriorates. If the refrigerant is in a single liquid phase at the inlet of the first expansion valve 41, the first line 111 will be filled with liquid refrigerant, thus significantly increasing the amount of refrigerant in the first line 111.

[0029] In contrast, in the air conditioning system 100 according to the present embodiment, as described in Fig. As shown in Figure 6, due to the thermal diode function of the third heat exchanger 51, no (or less) heat is exchanged from the heat exchanger unit 51b to the heat exchanger unit 51a. This maintains the refrigerant flow velocity at the inlet of the second expansion valve 42 and thus prevents any deterioration in the controllability of the second expansion valve 42. To ensure the degree of subcooling of the refrigerant at the inlet of the second expansion valve 42, a small amount of heat can be exchanged in the third heat exchanger 51.

[0030] In the air conditioning system 100 according to the present embodiment, the pressure in the first line 111 drops during cooling operation, as shown in Fig. 4 shown, and accordingly the amount of refrigerant in the first line 111 is reduced. However, during heating operation, the pressure in the first line 111 does not decrease, as shown in Fig. 6 shown, and accordingly the amount of refrigerant in the first line 111 is not reduced.

[0031] In the air conditioning system 100 according to the present embodiment, however, as described above, the sum V1 of the flow path volume Ve1 in the first heat exchanger 3 and the flow path volume Vp1 between points M1 and M2 is greater than the sum V2 of the flow path volume Ve2 in the second heat exchanger 6 and the flow path volume Vp2 between points M6 and M5 (V1 > V2). In other words, in the air conditioning system 100 according to the present embodiment, the amount of refrigerant required during cooling operation, in which the first heat exchanger 3 acts as a condenser, is greater than the amount of refrigerant required during heating operation, in which the first heat exchanger 3 acts as an evaporator. In such an air conditioning system 100, the third heat exchanger 51 in the indoor unit 102 described above allows for a reduction in the amount of refrigerant required during cooling operation, which requires a larger amount of refrigerant.This allows the amount of refrigerant used to fill the air conditioning system 100 to be reduced accordingly.

[0032] As described above, in the present embodiment of the air conditioning system 100, in which the first expansion valve 41 and the second expansion valve 42 are each provided at the upstream and downstream positions of the first line 111 (the liquid-side connecting line) between the first line 111 and the second line 112, which connect the indoor unit 102 and the outdoor unit 101, the amount of refrigerant in the first line 111 can be reduced. Second embodiment

[0033] Fig. Figure 7 is a representation that schematically shows an example of an overall configuration of an air conditioning unit 100A according to the present second embodiment.

[0034] In the air conditioning system 100 according to the first embodiment described above, the total sum V1 of the flow path volume Ve1 in the first heat exchanger 3 and the flow path volume Vp1 between points M1 and M2 is greater than the total sum V2 of the flow path volume Ve2 in the second heat exchanger 6 and the flow path volume Vp2 between points M5 and M6 (V1 > V2).

[0035] In contrast, in the air conditioning system 100A according to the present second embodiment, the total sum V1 of the flow path volume Ve1 in the first heat exchanger 3 and the flow path volume Vp1 between points M1 and M2 is smaller than the total sum V2 of the flow path volume Ve2 in the second heat exchanger 6 and the flow path volume Vp2 between points M5 and M6 (V1 < V2).

[0036] Furthermore, according to the present second embodiment, the air conditioning system 100A includes a fourth heat exchanger 52 instead of the third heat exchanger 51 described above. The air conditioning system 100A comprises, in particular, an outdoor unit 101A, an indoor unit 102A, a first line 111, and a second line 112.

[0037] The indoor unit 102A is the same as the indoor unit 102 described above, except that the third heat exchanger 51 has been removed. The outdoor unit 101A is the same as the outdoor unit 101 described above, except that a fourth heat exchanger 52 has been added.

[0038] The fourth heat exchanger 52 comprises: a heat exchanger unit 52b, arranged in a flow path connecting the first expansion valve 41 and the first line 111; and a heat exchanger unit 52a, arranged in a flow path connecting the first expansion valve 41 and the first heat exchanger 3. The fourth heat exchanger 52 has a so-called thermal diode function: it transfers heat from the heat exchanger unit 52b to the heat exchanger unit 52a and it transfers no or less heat from the heat exchanger unit 52a to the heat exchanger unit 52b. In particular, the fourth heat exchanger 52 is configured to exchange heat between the heat exchanger units 52b and 52a when the refrigerant in the heat exchanger unit 52b (hereinafter also referred to as the "third refrigerant") has a higher temperature than the refrigerant in the heat exchanger unit 52a (hereinafter also referred to as the "fourth refrigerant")., between the third refrigerant and the fourth refrigerant), and, if the third refrigerant has a lower temperature than the fourth refrigerant, no heat is exchanged between the heat exchange units 52b and 52a.

[0039] Fig. Figure 8 is a Mollier diagram created during a cooling operation in the air conditioning system 100A according to the present second embodiment. During cooling operation in the air conditioning system 100A, due to the thermal diode function of the fourth heat exchanger 52, no (or less) heat is exchanged from the heat exchanger unit 52a to the heat exchanger unit 52b. This maintains the refrigerant flow velocity at the inlet of the first expansion valve 41 and thus prevents a deterioration in the controllability of the first expansion valve 41.

[0040] Fig. Figure 9 is a Mollier diagram created during heating operation in the air conditioning system 100A according to the present second embodiment. During heating operation in the air conditioning system 100A, the fourth heat exchanger 52 is used for heat exchange between the heat exchanger units 52b and 52a. The dryness of the refrigerant at point M3 decreases, the flow velocity of the refrigerant at the inlet of the first expansion valve 41 decreases, and thus the pressure difference before and after the first expansion valve 41 decreases. As a result, as shown in Figure 9, the temperature difference between the refrigerant flow rate and the pressure difference between the refrigerant flow rate and the pressure difference after the first expansion valve 41 decreases. Fig. Figure 9 shows the pressure in the first line 111 being reduced to a lower value.

[0041] In this way, the fourth heat exchanger 52 in the air conditioning system 100A is used to reduce the pressure in the first line 111 during heating operation, thereby increasing the proportion of gaseous refrigerant in the first line 111. This allows the amount of refrigerant in the first line 111 to be reduced during heating operation.

[0042] In the air conditioning unit 100A, the pressure in the first line 111 drops during heating operation, as shown in Fig. Figure 9 shows that the amount of refrigerant in the first line 111 decreases accordingly. However, during cooling operation, the pressure in the first line 111 does not decrease, as shown in Figure 9. Fig. 8 shown, and accordingly the amount of refrigerant in the first line 111 is not reduced.

[0043] In the air conditioning system 100A according to the present second embodiment, however, as described above, the total V1 of the flow path volume Ve1 in the first heat exchanger 3 and the flow path volume Vp1 between points M1 and M2 is less than the total V2 of the flow path volume Ve2 in the second heat exchanger 6 and the flow path volume Vp2 between points M6 and M5 (V1 < V2). In other words, in the air conditioning system 100A according to the present second embodiment, the amount of refrigerant required during heating operation, in which the second heat exchanger 6 acts as a condenser, is greater than the amount of refrigerant required during cooling operation, in which the second heat exchanger 6 acts as an evaporator.In such an air conditioning unit 100A, the fourth heat exchanger 52, as described above and provided in the outdoor unit 101, allows for a reduction in the amount of refrigerant required during heating operation, which requires a larger amount of refrigerant. This allows the amount of refrigerant with which the air conditioning unit 100A is filled to be reduced accordingly. Third embodiment

[0044] Fig. Figure 10 is a schematic representation showing an example of the overall configuration of an air conditioner 100B according to the present third embodiment. The air conditioner 100B according to the present third embodiment comprises the components shown in Fig. 1 indoor unit 102 shown, which is in Fig. Figure 7 shows the outdoor unit 101A, as well as a first line 111 and a second line 112, which connect the indoor unit 102 and the outdoor unit 101A. In other words, the air conditioner 100B according to the present third embodiment includes both the third heat exchanger 51 and the fourth heat exchanger 52, as described above.

[0045] Fig. Figure 11 is a Mollier diagram created during a cooling operation in the air conditioning unit 100B according to the present third embodiment. During cooling operation in the air conditioning unit 100B, the third heat exchanger 51 is used for heat exchange between the heat exchanger units 51a and 51b, so that the pressure difference before and after the second expansion valve 42 decreases. This reduces the pressure in the first line 111 to a lower value, which makes it possible to reduce the amount of refrigerant in the first line 111 during cooling operation.

[0046] Since no heat is exchanged in the fourth heat exchanger 52, the pressure difference before and after the second expansion valve 42 is also reduced. This allows the controllability of the first expansion valve 41 to be maintained.

[0047] Fig. Figure 12 is a Mollier diagram created during a heating operation in the air conditioning system 100B according to the present third embodiment. During heating operation in the air conditioning system 100B, the fourth heat exchanger 52 is used for heat exchange between the heat exchange units 52b and 52a, so that the pressure difference before and after the first expansion valve 41 decreases. This reduces the pressure in the first line 111 to a lower value, which makes it possible to reduce the amount of refrigerant in the first line 111 even during heating operation.

[0048] Since no heat is exchanged in the third heat exchanger 51, the pressure difference before and after the first expansion valve 41 is also reduced. This allows the controllability of the second expansion valve 42 to be maintained. Fourth embodiment

[0049] Fig. Figure 13 shows an example of detailed configurations of the third heat exchanger 51 and the fourth heat exchanger 52 according to the first to third embodiments described above.

[0050] The third heat exchanger 51 is a so-called thermosiphon line. The third heat exchanger 51 comprises, in particular, a heat exchange unit 51a, a heat exchange unit 51b, a sealed vessel covering the heat exchange units 51a and 51b, and a working fluid 70 enclosed in a space within the sealed vessel. The working fluid 70 is water, ethanol, ammonia, or the like.

[0051] If the third heat exchanger 51 as in Fig. 13 shown in relation to the direction of gravity (i.e. when the heat exchange unit 51a is arranged vertically below the heat exchange unit 51b), the amount of enclosed working fluid 70 is adjusted so that at least the heat exchange unit 51a is in contact with the working fluid 70 in liquid state.

[0052] The following describes the operation of the third heat exchanger 51 (a thermosiphon-type conduit). If the temperature of the first refrigerant in heat exchanger 51a is higher than that of the second refrigerant in heat exchanger 51b, the working fluid 70 evaporates into a gas at the surface of heat exchanger 51a. The working fluid 70 rises in its gaseous state and reaches the surface of heat exchanger 51b, where it is cooled and condenses back into a liquid. The liquid working fluid 70 then falls due to gravity and returns to the surface of heat exchanger 51a. This cycle is repeated continuously as long as the first refrigerant in heat exchanger 51a has a higher temperature than the second refrigerant in heat exchanger 51b.In this process, heat is exchanged between the first refrigerant in the heat exchanger unit 51a and the second refrigerant in the heat exchanger unit 51b.

[0053] On the other hand, if the first refrigerant in the heat exchange unit 51a has a lower temperature than the second refrigerant in the heat exchange unit 51b, the working fluid 70 heated in the heat exchange unit 51b does not reach the surface of the heat exchange unit 51a, so that no heat exchange takes place between the first refrigerant in the heat exchange unit 51a and the second refrigerant in the heat exchange unit 51b.

[0054] As described above, the third heat exchanger 51 has a thermal diode function. In other words, the third heat exchanger 51 is configured to exchange heat between the first and second refrigerants when the temperature of the first refrigerant is higher than that of the second refrigerant; and not to exchange heat between the first and second refrigerants when the temperature of the first refrigerant is lower than that of the second refrigerant. In this case, the first refrigerant is located in the heat exchanger unit 51a, which is arranged between the second expansion valve 42 and the first line 111, and the second refrigerant is located in the heat exchanger unit 51b, which is arranged between the second expansion valve 42 and the second heat exchanger 6.

[0055] The fourth heat exchanger 52 can have the same configuration as the third heat exchanger 51. The fourth heat exchanger 52 specifically comprises the heat exchange unit 52a, the heat exchange unit 52b, the sealed vessel enclosing the heat exchange units 52a and 52b, and the working fluid 70 enclosed in a space within the sealed vessel. If the fourth heat exchanger 52 is configured as shown in Fig. 13 shown in relation to the direction of gravity (i.e. when the heat exchange unit 52b is arranged vertically below the heat exchange unit 52a), the amount of enclosed working fluid 70 is adjusted so that at least the heat exchange unit 52a is in contact with the working fluid 70 in liquid state.

[0056] In this configuration, the fourth heat exchanger 52 functions as a thermal diode. In other words, the fourth heat exchanger 52 is configured to exchange heat between the third and fourth refrigerants when the temperature of the third refrigerant is higher than that of the fourth, and not to exchange heat between the third and fourth refrigerants when the temperature of the third refrigerant is lower than that of the fourth. In this case, the third refrigerant is located in the heat exchanger unit 52b, which is arranged between the first expansion valve 41 and the first line 111, and the fourth refrigerant is located in the heat exchanger unit 52a, which is arranged between the first expansion valve 41 and the first heat exchanger 3.

[0057] As described above, the third heat exchanger 51 and the fourth heat exchanger 52, each designed as a thermosiphon heat conduction system, enable a thermal diode function of the third heat exchanger 51 and the fourth heat exchanger 52. Fifth embodiment

[0058] Fig. Figure 14 shows another example of the detailed configurations of the third heat exchanger 51 and the fourth heat exchanger 52 according to the first to third embodiments described above.

[0059] The third heat exchanger 51 is a so-called ring main. The third heat exchanger 51 comprises, in particular, the heat exchange units 51a and 51b, a condenser unit 81 covering the heat exchange unit 51b, an evaporator unit 82 covering the heat exchange unit 51a, and lines 83 and 84 connecting the condenser unit 81 and the evaporator unit 82. The evaporator unit 82 includes a wick 71 made of a porous material, located on the outer circumference of the heat exchange unit 51a.

[0060] Fig. Figure 15 is a cross-sectional view of the evaporator unit 82 along line XV-XV in Fig. 14. Wick 71 contains a liquid groove 72 as an indentation on the outer circumferential surface of the wick 71 and a gas groove 73 as an indentation on the inner circumferential surface of the wick 71. The wick 71, the liquid groove 72 and the gas groove 73 are filled with working fluid 70.

[0061] If the third heat exchanger 51 as in Fig. 14 shown in relation to the direction of gravity (i.e. when the heat exchange unit 51a is arranged vertically below the heat exchange unit 51b), the amount of enclosed working fluid 70 is adjusted so that at least the heat exchange unit 51a is in contact with the working fluid 70 in liquid state.

[0062] The following describes the operation of the third heat exchanger 51 (a closed-loop heat exchanger). If the first refrigerant in heat exchanger unit 51a has a higher temperature than the second refrigerant in heat exchanger unit 51b, heat is transferred from heat exchanger unit 51a to the wick 71, and the working fluid 70 evaporates from a liquid state to a gas at the surface of the gas groove 73. The working fluid 70, now in a gaseous state, flows through line 83 into the condenser unit 81 and is cooled at the surface of heat exchanger unit 51b to condense into a liquid. The working fluid 70, now condensed into a liquid in the condenser unit 81, returns to the evaporator unit 82 via line 84 by gravity and the capillary action generated in the wick 71.This cycle is repeated continuously if the first refrigerant in heat exchanger unit 51a has a higher temperature than the second refrigerant in heat exchanger unit 51b. Heat is exchanged between the first refrigerant in heat exchanger unit 51a and the second refrigerant in heat exchanger unit 51b.

[0063] On the other hand, if the first refrigerant in the heat exchange unit 51a has a lower temperature than the second refrigerant in the heat exchange unit 51b, the working fluid 70 heated in the heat exchange unit 51b does not reach the surface of the heat exchange unit 51a, so that no heat exchange takes place between the first refrigerant in the heat exchange unit 51a and the second refrigerant in the heat exchange unit 51b.

[0064] The fourth heat exchanger 52 can have the same configuration as the third heat exchanger 51. Specifically, the fourth heat exchanger 52 comprises the heat exchange units 52a and 52b, the condenser unit 81, which covers the heat exchange unit 52a, the evaporator unit 82, which covers the heat exchange unit 52b, and the lines 83 and 84, which connect the condenser unit 81 and the evaporator unit 82. The evaporator unit 82 includes a wick 71, which is made of a porous material and is located on the outer circumference of the heat exchange unit 51a. The wick 71 is filled with working fluid 70. When the fourth heat exchanger 52 is configured as in Fig. 14 shown in relation to the direction of gravity (i.e. when the heat exchange unit 52b is arranged vertically below the heat exchange unit 52a), the amount of enclosed working fluid 70 is adjusted so that at least the heat exchange unit 52b is in contact with the working fluid 70 in liquid state.

[0065] In such a configuration, the fourth heat exchanger 52 has a thermal diode function. In other words, the fourth heat exchanger 52 is configured to exchange heat between the third refrigerant in the heat exchange unit 52b and the fourth refrigerant in the heat exchange unit 52a when the third refrigerant has a higher temperature than the fourth refrigerant; and not to exchange heat between the third and fourth refrigerants when the third refrigerant has a lower temperature than the fourth refrigerant.

[0066] As described above, the third and fourth heat exchangers 51 and 52, each designed as a loop heat conduction system, enable a thermal diode function of the third and fourth heat exchangers 51 and 52 as in the case where the third and fourth heat exchangers 51 and 52 are each designed as a thermosiphon-type heat conduction system.

[0067] Furthermore, the third and fourth heat exchangers 51 and 52, each designed as a closed-loop heat transfer system, enable more efficient heat exchange than in the case where the third and fourth heat exchangers 51 and 52 are each designed as a thermosiphon heat transfer system. In other words, in the Fig. In the thermosiphon heat conduction system shown in Figure 13, the path of the working fluid 70 flowing from the vertically lower heat exchange units 51a and 52b to the vertically upper heat exchange units 51b and 52a is located in the same space as the path of the working fluid 70 flowing from the vertically upper heat exchange units 51b and 52a to the vertically lower heat exchange units 51a and 52b. Thus, the movement of the working fluid 70 is opposed by the opposing flows. In the Fig.In contrast, in the circulating heat flow shown in Figure 14, line 83 is provided as a path extending from the vertically lower heat exchanger units 51a and 52b to the vertically upper heat exchanger units 51b and 52a, and line 84 is provided as a path extending from the vertically upper heat exchanger units 51b and 52a to the vertically lower heat exchanger units 51a and 52b, so that the working fluid 70 moves in one direction. This reduces the resistance to the movement of the working fluid 70, allowing for efficient heat exchange.

[0068] It goes without saying that the embodiments disclosed herein are in every respect illustrative and not limiting. The scope of this disclosure is defined by the terms of the claims and not by the above description, and is intended to include all modifications within the meaning and scope that correspond to the terms of the claims. REFERENCE MARK LIST

[0069] 1 Compressor, 2 Switching device, 3 First heat exchanger, 6 Second heat exchanger, 41 First expansion valve, 42 Second expansion valve, 51 Third heat exchanger, 51a, 51b, 52a, 52b Heat exchanger unit, 52 Fourth heat exchanger, 70 Working fluid, 71 Wick, 72 Liquid groove, 73 Gas groove, 81 Condenser unit, 82 Evaporator unit, 83, 84 Line, 100, 100A, 100B Air conditioner, 101 Outdoor unit, 102 Indoor unit, 111 First line, 112 Second line. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 6878612 [0002, 0003]

Claims

[1] Air conditioning system, comprising: an outdoor unit; an indoor unit and a first line and a second line, each connecting the indoor unit to the outdoor unit, wherein the outdoor unit includes: a first heat exchanger; a first expansion valve connected between the first heat exchanger and the first line; a compressor; and a switching device connected between the first heat exchanger, the second line, and the compressor, the switching device being configured to switch a state between a first state and a second state, the first state being a state in which a suction port of the compressor is connected to the second line and an outlet port of the compressor is connected to the first heat exchanger, and the second state being a state in which the suction port of the compressor is connected to the first heat exchanger and the outlet port of the compressor is connected to the second line, the indoor unit includes: a second heat exchanger connected to the second conduit; and a second expansion valve connected between the second heat exchanger and the first line, the air conditioning system further comprises at least one of a third heat exchanger in the indoor unit and a fourth heat exchanger in the outdoor unit, the third heat exchanger is configured to exchange heat between a first refrigerant and a second refrigerant when a temperature of the first refrigerant is higher than a temperature of the second refrigerant, and not to exchange heat between the first refrigerant and the second refrigerant when the temperature of the first refrigerant is lower than the temperature of the second refrigerant, wherein the first refrigerant is a refrigerant flowing between the second expansion valve and the first line, and the second refrigerant is a refrigerant flowing between the second expansion valve and the second heat exchanger, and the fourth heat exchanger is configured to exchange heat between a third refrigerant and a fourth refrigerant when a temperature of the third refrigerant is higher than a temperature of the fourth refrigerant, and not to exchange heat between the third refrigerant and the fourth refrigerant when the temperature of the third refrigerant is lower than the temperature of the fourth refrigerant, wherein the third refrigerant is a refrigerant flowing between the first expansion valve and the first conduit, and the fourth refrigerant is a refrigerant flowing between the first expansion valve and the first heat exchanger. [2] Air conditioning system according to claim 1, wherein a total sum of a volume of the first heat exchanger and a volume of a flow path connecting the first heat exchanger and the first expansion valve is greater than a total sum of a volume of the second heat exchanger and a volume of a flow path connecting the second heat exchanger and the second expansion valve, and the air conditioning system includes the third heat exchanger. [3] The air conditioner according to claim 1, wherein a total sum of a volume of the first heat exchanger and a volume of a flow path connecting the first heat exchanger and the first expansion valve is smaller than a total sum of a volume of the second heat exchanger and a volume of a flow path connecting the second heat exchanger and the second expansion valve, and the air conditioner includes the fourth heat exchanger. [4] The air conditioning system according to claim 1, comprising the third heat exchanger and the fourth heat exchanger. [5] The air conditioner according to claim 1, wherein at least one of the third heat exchanger and the fourth heat exchanger is a thermosiphon type heat pipe. [6] The air conditioner according to claim 1, wherein at least one of the third heat exchanger and the fourth heat exchanger is a cycle heat pipe.

Images