REFRIGERATION CYCLE DEVICE

Abstract

 A refrigeration cycle apparatus includes a compressor (1), a flow path switching device (2), a first heat exchanger (4) having a first heat exchange unit (4a) and a second heat exchange unit (4b), a flow path changing device (10), a first expansion valve (8a), and a second heat exchanger (9). The flow path switching device is configured to switch flow of the refrigerant compressed by the compressor between flow to the first heat exchanger and flow to the second heat exchanger. The flow path changing device is configured to switch flow of the refrigerant among flow successively through the first heat exchange unit and the second heat exchange unit, flow in parallel through the first heat exchange unit and the second heat exchange unit, and flow through any one of the first heat exchange unit and the second heat exchange unit. This allows the flow path changing device to switch between the first heat exchange unit and the second heat exchange unit, controlling the capacity of the first heat exchanger. Thus, the capacity of the heat exchanger can be controlled in accordance with the operation during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating.

Description

TECHNICAL FIELD

[0001] The present invention relates to refrigeration cycle apparatuses.

BACKGROUND ART

[0002] In a conventionally known air conditioner, two unit flow paths are connected in series during cooling operation, and two unit flow paths are connected in parallel during heating operation. Such an air conditioner is described in, for example, Japanese Patent Laying-Open No. 2015-117936 (PTL 1).

CITATION LIST

PATENT LITERATURE

[0003] PTL 1: Japanese Patent Laying-Open No. 2015-117936

SUMMARY OF INVENTION

TECHNICAL PROBLEM

[0004] The air conditioner described in PTL 1 does not assume the operations during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating. Consequently, the capacity of a heat exchanger cannot be controlled in accordance with the operation during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating.

[0005] The present invention has been made in view of the above problem, and has an object to provide a refrigeration cycle apparatus capable of controlling the capacity of a heat exchanger.

SOLUTION TO PROBLEM

[0006] A refrigeration cycle apparatus according to the present invention includes a compressor, a flow path switching device, a first heat exchanger, a flow path changing device, a first expansion valve, and a second heat exchanger. The compressor compresses refrigerant. The flow path switching device is connected to the compressor. The first heat exchanger is connected to the flow path switching device and has a first heat exchange unit and a second heat exchange unit. The flow path changing device connects the first heat exchange unit and the second heat exchange unit to each other. The first expansion valve is connected to the first heat exchange unit and the second heat exchange unit. The second heat exchanger is connected to the first expansion valve and the flow path switching device. The flow path switching device is configured to switch flow of the refrigerant compressed by the compressor between flow through the first heat exchanger and flow through the second heat exchanger. The flow path changing device is configured to switch flow of the refrigerant among flow successively through the first heat exchange unit and the second heat exchange unit, flow in parallel through the first heat exchange unit and the second heat exchange unit, and flow through any one of the first heat exchange unit and the second heat exchange unit.

ADVANTAGEOUS EFFECTS OF INVENTION

[0007] In the refrigeration cycle apparatus of the present invention, the flow path changing device is configured to switch flow of the refrigerant among flow successively through the first heat exchange unit and the second heat exchange unit, flow in parallel through the first heat exchange unit and the second heat exchange unit, and flow through any one of the first heat exchange unit and the second heat exchange unit. Consequently, the flow path changing device can switch between the first heat exchange unit and the second heat exchange unit to control the capacity of the first heat exchanger. Therefore, the capacity of the heat exchanger can be controlled in accordance with the operation during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating.

BRIEF DESCRIPTION OF DRAWINGS

[0008] 

Fig. 1 is a schematic configuration diagram showing a refrigeration cycle apparatus according to Embodiment 1.

Fig. 2 is a schematic configuration diagram showing a flow of refrigerant of a heat exchanger of the refrigeration cycle apparatus according to Embodiment 1 (cooling/heating).

Fig. 3 is a schematic configuration diagram showing arrangements in a column direction and a row direction of the heat exchanger of the refrigeration cycle apparatus according to Embodiment 1.

Fig. 4 is a schematic configuration diagram showing a configuration of the heat exchanger of the refrigeration cycle apparatus according to Embodiment 1.

Fig. 5 is a schematic configuration diagram showing a P-h diagram of a refrigeration cycle according to Embodiment 1.

Fig. 6 shows a relationship of a flow path number ratio (Nb/Na) to an air-refrigerant temperature difference ratio according to Embodiment 1.

Fig. 7 shows a relationship of a heat exchanger capacity ratio (Vb/Va) to an air-refrigerant temperature difference ratio according to Embodiment 1.

Fig. 8 is a schematic configuration diagram showing a modification of a flow path changing device of the refrigeration cycle apparatus according to Embodiment 1.

Fig. 9 is a schematic configuration diagram showing the refrigeration cycle apparatus according to Embodiment 1 in which a position for attaching a first expansion valve is located on an indoor unit side.

Fig. 10 is a schematic configuration diagram showing the refrigeration cycle apparatus according to Embodiment 1 in which the first expansion valve is replaced by a second on-off valve.

Fig. 11 is a schematic configuration diagram showing a difference in the COP peak when the number of paths is made variable during cooling and heating according to Embodiment 1.

Fig. 12 is a schematic configuration diagram showing a refrigeration cycle apparatus according to Embodiment 2.

Fig. 13 is a schematic configuration diagram showing a modification of a flow path changing device of the refrigeration cycle apparatus according to Embodiment 2.

Fig. 14 is a schematic configuration diagram showing a refrigeration cycle apparatus according to Embodiment 3.

Fig. 15 is a schematic configuration diagram showing the refrigeration cycle apparatus according to Embodiment 3 in which a position for attaching an expansion valve is located on an indoor unit side.

Fig. 16 is a schematic configuration diagram showing the refrigeration cycle apparatus according to Embodiment 3 in which a base cooling unit is provided in an intermediate pressure portion.

Fig. 17 is a schematic configuration diagram showing a cross section of the base cooling unit of Fig. 16.

Fig. 18 is a schematic configuration diagram showing a refrigeration cycle apparatus according to Embodiment 4.

Fig. 19 is a schematic configuration diagram showing a modification of a flow path changing device of the refrigeration cycle apparatus according to Embodiment 4.

Fig. 20 is a schematic configuration diagram showing a refrigeration cycle apparatus according to Embodiment 5.

Fig. 21 is a schematic configuration diagram showing a modification of the refrigeration cycle apparatus according to Embodiment 5.

Fig. 22 is a schematic configuration diagram showing a refrigeration cycle apparatus according to Embodiment 6.

Fig. 23 is a schematic configuration diagram showing an example in which an indoor unit is provided with a flow path changing device.

DESCRIPTION OF EMBODIMENTS

[0009] Embodiments of the present invention will now be described with reference to the drawings.

Embodiment 1

[0010] With reference to Fig. 1, a refrigeration cycle apparatus according to Embodiment 1 of the present invention includes a compressor 1, a flow path switching device 2, a first heat exchanger 4 having a first heat exchange unit 4a and a second heat exchange unit 4b, a flow path changing device 10 (a first header 3a, a second header 3b, a first distributor 5a, a second distributor 5b, a first on-off valve 6a, a first check valve 7a, a second expansion valve 8b), a first expansion valve 8a, and a second heat exchanger 9. These components are connected to each other through a pipe to constitute a refrigerant circuit.

[0011] The refrigeration cycle apparatus includes an unshown control device (controller). The control device (controller) is configured to, for example, perform a computation and provide an instruction to control each means, device, and the like of the cooling apparatus. Specifically, the control device (controller) is configured to, for example, control the operations of the valves of flow path switching device 2 and flow path changing device 10.

[0012] With reference to Fig. 1, first heat exchanger 4 is an outdoor-unit heat exchanger, and second heat exchanger 9 is an indoor-unit heat exchanger. With reference to Fig. 1, compressor 1, flow path switching device 2, first heat exchanger 4 having first heat exchange unit 4a and second heat exchange unit 4b, flow path changing device 10 (first header 3a, second header 3b, first distributor 5a, second distributor 5b, first on-off valve 6a, first check valve 7a, second expansion valve 8b), and first expansion valve 8a are provided in an outdoor unit. Second heat exchanger 9 is provided in an indoor unit.

[0013] The refrigeration cycle apparatus has refrigerant flowing through the refrigerant circuit. The refrigerant may be, for example, R410a, R32, or R1234yf.

[0014] Compressor 1 is configured to compress refrigerant. Compressor 1 may be a constant-speed compressor having a constant compression capacity or an inverter compressor having a variable compression capacity. This inverter compressor is configured to variably control the number of rotations. Specifically, the number of rotations of this inverter compressor is adjusted by its driving frequency being changed based on an instruction from the unshown control device (controller). This changes compression capacity. This compression capacity is an amount by which refrigerant is fed per unit time.

[0015] Flow path switching device 2 is connected to compressor 1. Flow path switching device 2 is configured to switch a refrigerant flow between during cooling operation and during heating operation. Flow path switching device 2 is a four-way valve. The four-way valve may be replaced by two three-way valves combined together.

[0016] First heat exchanger 4 is connected to flow path switching device 2. First expansion valve 8a is connected to first heat exchange unit 4a and second heat exchange unit 4b. First expansion valve 8a is configured to expand (decompress) the refrigerant. First expansion valve 8a is, for example, an electronic expansion valve. Second expansion valve 8b or the like, described below, may also be an electronic expansion valve.

[0017] Flow path changing device 10 connects first heat exchange unit 4a and second heat exchange unit 4b to each other. Flow path changing device 10 is configured to switch a flow path for refrigerant flowing through first heat exchange unit 4a and second heat exchange unit 4b. Second heat exchanger 9 is connected to first expansion valve 8a and flow path switching device 2. First heat exchanger 4 and second heat exchanger 9 each serve to perform heat exchange between refrigerant and air. First heat exchanger 4 and second heat exchanger 9 are each formed of, for example, a pipe and a fin.

[0018] Fig. 2 is a schematic configuration diagram showing a relationship between a heat transfer area A and a number of flow paths N of each of first heat exchange unit 4a and second heat exchange unit 4b of the refrigeration cycle apparatus according to Embodiment 1 of the present invention.

[0019] As shown in Fig. 2, first heat exchange unit 4a and second heat exchange unit 4b are connected in series during cooling. The number of flow paths is Na with a large number of flow paths at a gas-rich inlet and is Nb with a small number of flow paths at a liquid-rich outlet.

[0020] During heating, first heat exchange unit 4a and second heat exchange unit 4b are connected in parallel. The number of flow paths is a sum (Na+Nb) of number of flow paths Na of first heat exchange unit 4a and number of flow paths Nb of second heat exchange unit 4b.

[0021] Fig. 3 is a schematic configuration diagram showing the arrangements in a column direction and a row direction of first heat exchange unit 4a and second heat exchange unit 4b shown in Figs. 1 and 2. When first heat exchange unit 4a and second heat exchange unit 4b have an equal number of rows R, for a number of columns C of the heat exchanger, a number of columns Ca of first heat exchange unit 4a and a number of columns Cb of second heat exchange unit 4b have a relationship of Ca>Cb. When first heat exchange unit 4a and second heat exchange unit 4b have an equal number of columns C, for a number of rows R of the heat exchanger, a number of rows Ra of first heat exchange unit 4a and a number of rows Rb of second heat exchange unit 4b have a relationship of Ra>Rb.

[0022] During condensation of refrigerant, the heat exchanger has a higher liquid phase ratio as a flow more tends to be a wake flow and is affected by a positioning head, and thus, the heat exchanger is preferably provided to achieve flow in the direction of gravity. During evaporation of refrigerant, the heat exchanger has a higher gas phase ratio as a flow more tends to be a wake flow and is not affected by the positioning head, and thus, the heat exchanger is preferably provided to achieve flow against the direction of gravity.

[0023] As shown in Fig. 4, heat exchangers equal to each other in heat exchanger capacity and unit flow path may be combined in parallel to constitute first heat exchange unit 4a and second heat exchange unit 4b. Alternatively, heat exchangers different from each other in heat exchanger capacity and unit flow path may be combined together. From the viewpoint of manufacturing, a large number of similar heat exchangers may be preferably produced and combined together.

[0024] Fig. 5 is a schematic configuration diagram showing a P-h diagram of a refrigeration cycle. In the refrigeration cycle apparatus of the present embodiment, the ratio of a liquid portion is smaller than the ratio of a gas and two-phase portion during condensation. Each of first heat exchange unit 4a and second heat exchange unit 4b accordingly has relationships of Aa>Ab, Va>Vb, and Na>Nb, where heat transfer area A is Aa and Ab, heat exchanger capacity V is Va and Vb, and number of flow paths N is Na and Nb. Thus, first heat exchanger 4 (outdoor-unit heat exchanger) is preferably divided such that the gas and two-phase portion with a large pressure loss is mostly or entirely subjected to heat exchange by first heat exchange unit 4a and that the refrigerant flowing through second heat exchange unit 4b is mostly or entirely in a liquid phase.

[0025] Fig. 6 shows a relationship of a flow path number ratio (Nb/Na), which is a ratio of second heat exchange unit 4b to first heat exchange unit 4a, to an air-refrigerant temperature difference of the refrigeration cycle. Fig. 6 reveals that the number of flow paths is preferably made smaller with a decreasing temperature difference.

[0026] Since heat exchange is performed in the heat exchanger, the degree of dryness gradually decreases, and a pressure loss decreases. Consequently, the flow path number ratio is at least smaller than 100%.

[0027] The pressure loss decreases with an increasing liquid ratio due to an increasing density and a decreasing flow rate. Since the heat transfer performance also decreases, the heat transfer performance needs to be improved by increasing a flow rate while providing an equal or lower pressure loss.

[0028] Fig. 7 shows a relationship of a heat exchanger capacity ratio (Vb/Va), which is a ratio of second heat exchange unit 4b to first heat exchange unit 4a, to an air-refrigerant temperature difference of a refrigeration cycle.

[0029] Here, the heat exchanger capacity ratio is within the range of ratios represented by 0% < heat exchanger capacity ratio < 50%.

[0030] Since there is no second heat exchange unit 4b at a heat exchanger capacity ratio of 0%, the heat exchanger capacity ratio is at least greater than 0%. Since the heat exchanger capacity of first heat exchange unit 4a having high heat transfer performance is lower than the heat exchanger capacity of second heat exchange unit 4b, which will serve as a gas and two-phase portion, at a heat exchanger capacity ratio of 50% or more, the performance decreases conversely.

[0031] The above configuration is a minimum element enabling the present invention and cooling and heating operation, and devices such as a gas-liquid branch device, a receiver, an accumulator, and a high/low pressure heat exchanger may be connected to constitute a refrigeration cycle apparatus.

[0032] Each of first heat exchanger (outdoor-unit heat exchanger) 4 and second heat exchanger (indoor-unit heat exchanger) 9 may be any of, for example, a plate fin heat exchanger, a fin and tube heat exchanger, a flat tube (multi-hole tube) heat exchanger, and a corrugated heat exchanger.

[0033] A heat exchange medium subjected to heat exchange with refrigerant may be air, as well as water or antifreeze solution (e.g., propylene glycol, ethylene glycol).

[0034] The type of a heat exchanger, the shape of a fin, or the like of the outdoor-unit heat exchanger and the indoor-unit heat exchanger may be identical to or different from each other. For example, the outdoor-unit heat exchanger may be a flat tube, and the indoor-unit heat exchanger may be a fin and tube heat exchanger.

[0035] Although the embodiment of the present invention describes only a case in which the outdoor unit includes first heat exchange unit 4a and second heat exchange unit 4b, the indoor unit may include a similar circuit configuration and may be formed such that parallel connection is provided during cooling and series connection is provided during heating. Since the outdoor unit and the indoor unit replace their roles between during cooling and during heating, series connection and series connection are replaced accordingly.

[0036] Although the outdoor-unit heat exchanger is divided into two parts, namely, first heat exchange unit 4a and second heat exchange unit 4b in the embodiment of the present invention, at least any of the indoor-unit heat exchanger and the outdoor-unit heat exchanger may be divided into three or more parts. For example, the heat exchanger capacity and the number of flow paths of each of the indoor-unit heat exchanger and the outdoor-unit heat exchanger may be changed for each of gas phase, two-phase, and liquid phase.

[0037] With reference to Fig. 8, in flow path changing device 10 of the present embodiment, first distributor 5a and second distributor 5b of Fig. 1 may be replaced by a third header 3c and a fourth header 3d, respectively.

[0038] With reference to Fig. 9, first expansion valve 8a may be provided in the indoor unit in the refrigeration cycle apparatus of the present embodiment.

[0039] With reference to Fig. 10, second expansion valve 8b may be replaced by a second on-off valve 6b in flow path changing device 10 of the present embodiment.

[0040] Description will now be given of an operation of the refrigeration cycle apparatus according to Embodiment 1 which has the above configuration.

[0041] First, a basic operation of the refrigeration cycle apparatus during cooling operation will be described with reference to Fig. 1. During cooling, refrigerant flows from compressor 1 into flow path switching device 2 and flows through first header 3a into first heat exchange unit 4a. The refrigerant condenses in first heat exchange unit 4a and flows through first distributor 5a, first on-off valve 6a, and second header 3b into second heat exchange unit 4b. The refrigerant further condenses in second heat exchange unit 4b and flows through second distributor 5b into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2. That is to say, during cooling, the refrigerant circulates through the refrigeration cycle apparatus as indicated by the solid arrow in Fig. 1.

[0042] Next, a basic operation of the refrigeration cycle apparatus during heating operation will be described. During heating, refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, is branched to a first flow path, in which the refrigerant flows through second distributor 5b, and a second flow path, in which the refrigerant flows through second expansion valve 8b. In the first flow path, the refrigerant flows through second distributor 5b into second heat exchange unit 4b. The refrigerant evaporates in second heat exchange unit 4b and flows through second header 3b and first check valve 7a into first header 3a. In the second flow path, the refrigerant flows through first distributor 5a into first heat exchange unit 4a. The refrigerant evaporates in first heat exchange unit 4a and flows into first header 3a. The refrigerant obtained by confluence at first header 3a returns to compressor 1 through flow path switching device 2. That is to say, during heating, the refrigerant circulates through the refrigeration cycle apparatus as indicated by the broken arrow in Fig. 1. Also in the following figures, a refrigerant flow during cooling is indicated by the solid arrow, and a refrigerant flow during heating is indicated by the broken arrow.

[0043] Next, description will be given of operations of the refrigeration cycle apparatus during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations. If the compressor frequency decreases due to a drop in high pressure and a reduction in capability during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations, a required compression ratio cannot be achieved. Consequently, the degree of supercooling cannot be achieved at an outlet of the condenser due to a drop in high pressure, which may allow two-phase refrigerant to flow into the inlet side of the expansion valve.

[0044] If the refrigeration cycle apparatus exhibits capability more than required even by reducing the compressor frequency, the compressor may frequently repeat start and stop (activation and deactivation).

[0045] To prevent the above operation, the refrigeration cycle apparatus according to Embodiment 1 opens or closes first on-off valve 6a and second expansion valve 8b during high-outside-temperature heating operation, low-outside-temperature cooling operation, and low-capacity cooling/heating operation. This allows the refrigerant to flow into first heat exchange unit 4a alone during cooling and the refrigerant to flow into second heat exchange unit 4b alone during heating. In this manner, a circuit that reduces heat exchanger capacity (AK value) can be formed.

[0046] Specifically, first on-off valve 6a is closed during low-outside-temperature cooling operation and low-capacity cooling operation. Consequently, the refrigerant flows from compressor 1 into flow path switching device 2 and flows through first header 3a into first heat exchange unit 4a. The refrigerant condenses in first heat exchange unit 4a and flows through first distributor 5a and second expansion valve 8b into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2.

[0047] During high-outside-temperature heating operation and low-capacity heating operation, first on-off valve 6a is closed, and second expansion valve 8b (or second on-off valve 6 in Fig. 10) is closed. Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows through second distributor 5b into second heat exchange unit 4b. The refrigerant evaporates in second heat exchange unit 4b, flows through second header 3b and first check valve 7a into first header 3a, and returns to compressor 1 through flow path switching device 2.

[0048] The effects of the refrigeration cycle apparatus according to Embodiment 1 which has the above configuration will now be described.

[0049] In the refrigeration cycle apparatus according to Embodiment 1, flow path changing device 10 is configured to switch flow of the refrigerant among flow successively through first heat exchange unit 4a and second heat exchange unit 4b, flow in parallel through first heat exchange unit 4a and second heat exchange unit 4b, and flow to any one of first heat exchange unit 4a and second heat exchange unit 4b. This allows flow path changing device 10 to switch between first heat exchange unit 4a and second heat exchange unit 4b to control the capacity of first heat exchanger 4. Thus, the capacity of the heat exchanger can be controlled in accordance with the operation during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating.

[0050] In the refrigeration cycle apparatus according to Embodiment 1, when flow path switching device 2 causes the refrigerant compressed by compressor 1 to flow through second heat exchanger 9, flow path changing device 10 is configured to switch flow of the refrigerant between flow in parallel through first heat exchange unit 4a and second heat exchange unit 4b, and flow through second heat exchange unit 4b alone. Thus, during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations, first on-off valve 6a is closed and second expansion valve 8b (or second on-off valve 6b) is closed to reduce a heat exchanger capacity (AK value) and increase a condensation pressure, thereby achieving the compression ratio and the degree of supercooling.

[0051] During high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations, first on-off valve 6a is closed and second expansion valve 8 (or second on-off valve 6b in Fig. 10) is closed, preventing start and stop of compressor 1.

[0052] The operation can be continued even during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations, leading to a wider operation range of the refrigeration cycle apparatus than a conventional range.

[0053] During high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations, open/close of the valve of flow path changing device 10 can be switched to change the capacity of the heat exchanger.

[0054] In the refrigeration cycle apparatus according to Embodiment 1, the first heat exchanger capacity is greater than the second heat exchanger capacity, and the number of the at least one first flow path is greater than the number of the at least one second flow path. Thus, first heat exchange unit 4a and second heat exchange unit 4b are connected in series during cooling and in parallel during heating, and first heat exchange unit 4a is greater than second heat exchange unit 4b in heat exchanger capacity and the number of flow paths, thus providing the number of flow paths optimum for each of cooling and heating. Consequently, the number of flow paths (path number) can be made variable during cooling and heating as shown in Fig. 11.

[0055] Providing an optimum number of flow paths can improve coefficient of performance (COP) and also improve annual performance factor (APF) during each of cooling and heating.

[0056] During cooling, the heat exchanger capacity of first heat exchange unit 4a is made greater than the heat exchanger capacity of second heat exchange unit 4b, thus increasing a liquid-phase region ratio, at which the flow rate of refrigerant flowing into second heat exchange unit 4b becomes slower.

[0057] During cooling operation, the number of flow paths of first heat exchange unit 4a is made greater than the number of flow paths of second heat exchange unit 4b, thus increasing the flow rate of refrigerant flowing into second heat exchange unit 4b.

[0058] The number of flow paths and the heat exchanger capacity of first heat exchange unit 4a are made greater than the number of flow paths and the heat exchanger capacity of second heat exchange unit 4b, improving the heat transfer performance in a liquid-phase region with a small pressure loss while reducing a pressure loss in the gas and two-phase region.

[0059] Improving heat transfer performance can reduce a pressure rise during condensation.

[0060] Reducing a pressure rise during condensation can reduce a pressure input.

[0061] Reducing compression input can improve coefficient of performance (COP).

[0062] During heating, the number of flow paths is made equal to a sum of the number of flow paths of first heat exchange unit 4a and the number of flow paths of second heat exchange unit 4b, thus reducing the length of each flow path.

[0063] During heating, increasing the number of flow paths and reducing the length of the flow path can reduce a pressure drop during evaporation.

[0064] Reducing a pressure drop during evaporation can reduce compression input.

[0065] Reducing compression input can improve coefficient of performance (COP).

Embodiment 2

[0066] A refrigeration cycle apparatus according to Embodiment 2 of the present invention is similar to that of Embodiment 1 in basic configuration but is different therefrom in that first check valve 7a and second expansion valve 8b are replaced by second on-off valve 6b and a third on-off valve 6c (or a first three-way valve 10a, a second thee-way valve 10b in Fig. 13) capable of causing refrigerant to flow bidirectionally. This enables capacity control by selecting any one of first heat exchange unit 4a or second heat exchange unit 4b during cooling and selecting any one of first heat exchange unit 4a and second heat exchange unit 4b during heating. The same components as those of Embodiment 1 will be denoted by the same reference signs, and description thereof will not be repeated. The same applies to Embodiment 3 to Embodiment 6.

[0067] With reference to Fig. 12, the refrigeration cycle apparatus according to Embodiment 2 of the present invention includes compressor 1, flow path switching device 2, first heat exchanger 4 having first heat exchange unit 4a and second heat exchange unit 4b, flow path changing device 10 (first header 3a, second header 3b, first distributor 5a, second distributor 5b, first on-off valve 6a, second on-off valve, third on-off valve 6c), first expansion valve 8a, and second heat exchanger 9.

[0068] With reference to Fig. 13, in flow path changing device 10 of the present embodiment, first on-off valve 6a, second on-off valve 6b, and third on-off valve 6c of Fig. 12 may be replaced by first three-way valve 10a and second three-way valve 10b.

[0069] As in Embodiment 1, first distributor 5a and second distributor 5b of flow path changing device 10 may be replaced by third header 3c and fourth header 3d of Fig. 8.

[0070] Description will now given of an operation of the refrigeration cycle apparatus according to Embodiment 2 which has the above configuration.

[0071] The basic cooling and heating operations are similar to those of Embodiment 1, description of which will not be repeated.

[0072] With reference to Fig. 12, when first heat exchange unit 4a is used during low-outside-temperature cooling operation and low-capacity cooling operation, first on-off valve 6a and third on-off valve 6c are closed, and second on-off valve 6b is opened. Consequently, refrigerant flows from compressor 1 into flow path switching device 2, and then flows through first header 3a into first heat exchange unit 4a. The refrigerant condenses in first heat exchange unit 4a and flows through first distributor 5a and second on-off valve 6b and then into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2.

[0073] When second heat exchange unit 4b is used during low-outside-temperature cooling operation and low-capacity cooling operation, first on-off valve 6a and second on-off valve 6b are closed, and third on-off valve 6c is opened. Consequently, the refrigerant flows from compressor 1 into flow path switching device 2, and flows through first header 3a and second header 3b into second heat exchange unit 4b. The refrigerant condenses in second heat exchange unit 4b and flows through second distributor 5b and then into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2.

[0074] When first heat exchange unit 4a is used during high-outside-temperature heating and low-capacity heating, first on-off valve 6a and third on-off valve 6c are closed, and second on-off valve 6b is opened. Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows through second on-off valve 6b and first distributor 5a into first heat exchange unit 4a. The refrigerant evaporates in first heat exchange unit 4a and returns to compressor 1 through first header 3a and flow path switching device 2.

[0075] When second heat exchange unit 4b is used during high-outside-temperature heating and low-capacity heating, first on-off valve 6a and second on-off valve 6b are closed, and third on-off valve 6c is opened. Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows through second distributor 5b into second heat exchange unit 4b. The refrigerant evaporates in second heat exchange unit 4b and returns to compressor 1 through second header 3b, first header 3a, and flow path switching device 2.

[0076] With reference to Fig. 13, when first heat exchange unit 4a is used during low-outside-temperature cooling operation and low-capacity cooling operation, first three-way valve 10a is switched to the heating mode (broken line), and second three-way valve 10b is switched to the cooling mode (solid line). Consequently, the refrigerant flows from compressor 1 into flow path switching device 2, and then flows through first header 3a into first heat exchange unit 4a. The refrigerant condenses in first heat exchange unit 4a, and flows through first distributor 5a and first three-way valve 10a and then into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2.

[0077] When second heat exchange unit 4b is used during low-outside-temperature cooling operation and low-capacity cooling operation, first three-way valve 10a is switched to the cooling mode (solid line), and second three-way valve 10b is switched to the heating mode (broken line). Consequently, the refrigerant flows from compressor 1 into flow path switching device 2 and flows through first header 3a, second three-way valve 10b, and second header 3b into second heat exchange unit 4b. The refrigerant condenses in second heat exchange unit 4b, and flows through second distributor 5b and then into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2.

[0078] When first heat exchange unit 4a is used during high-outside-temperature heating and low-capacity heating, first three-way valve 10a is switched to the heating mode (broken line), and second three-way valve 10b is switched to the cooling mode (solid line). Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and then flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows through first three-way valve 10a and first distributor 5a into first heat exchange unit 4a. The refrigerant evaporates in first heat exchange unit 4a and returns to compressor 1 through first header 3a and flow path switching device 2.

[0079] When second heat exchange unit 4b is used during high-outside-temperature heating and low-capacity heating, first three-way valve 10a is switched to the cooling mode (solid line), and second three-way valve 10b is switched to the heating mode (broken line). Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and then flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows through second distributor 5b into second heat exchange unit 4b. The refrigerant evaporates in second heat exchange unit 4b and returns to compressor 1 through second header 3b, second three-way valve 10b, first header 3a, and flow path switching device 2.

[0080] The effects of the refrigeration cycle apparatus according to Embodiment 2 which has the above configuration will now be described.

[0081] In the refrigeration cycle apparatus according to Embodiment 2, flow path changing device 10 is configured to, when flow path switching device 2 causes refrigerant to flow through first heat exchanger 4, switch flow of the refrigerant by selecting any one of first heat exchange unit 4a and second heat exchange unit 4b. Also, flow path changing device 10 is configured to, when flow path switching device 2 causes the refrigerant to flow to second heat exchanger 9, switch flow of the refrigerant by selecting any one of first heat exchange unit 4a and second heat exchange unit 4b. Thus, selecting any one of first heat exchange unit 4a and second heat exchange unit 4b enables capacity control of the heat exchanger.

[0082] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can change the heat exchanger by selecting a heat exchanger with a different heat exchanger capacity.

[0083] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can increase the condensing pressure at multiple stages by the number of heat exchangers that have at least divided the heat exchanger capacity (AK value).

[0084] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can increase the condensing pressure at multiple stages by the number of divided heat exchangers that have divided the heat exchanger capacity (AK value), thereby preventing an excessive pressure rise.

[0085] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can prevent start and stop of compressor 1.

[0086] Allowing operation to be continued even during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations results in a wider operating range of the refrigeration cycle apparatus than a conventional operating range.

[0087] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can change the capacity of the heat exchanger by the number of heat exchangers that have divided the capacity of the heat exchanger.

Embodiment 3

[0088] A refrigeration cycle apparatus according to Embodiment 3 of the present invention is similar to that of Embodiment 1 in basic configuration but is different therefrom in that it includes a third expansion valve 8c. Consequently, a region in which pressure is always brought into the intermediate state during cooling and heating can be provided. Also, the refrigeration cycle apparatus according to Embodiment 3 of the present invention differs from that of Embodiment 1 in that at least one temperature sensing means (not shown) is provided between the outlet of first heat exchange unit 4a and the outlet of first header 3a, between second heat exchange unit 4b and the outlet of second header 3b, and between second heat exchanger 9 and the inlet of compressor 1 to adjust the degree of superheat at and downstream of the outlet of the indoor-unit heat exchanger during cooling and adjust the degree of superheat at and downstream of the outlet of the heat exchanger of each outdoor-unit heat exchanger during cooling.

[0089] With reference to Fig. 14, the refrigeration cycle apparatus according to Embodiment 3 of the present invention includes compressor 1, flow path switching device 2, first heat exchanger 4 having first heat exchange unit 4a and second heat exchange unit 4b, flow path changing device 10 (first header 3a, second header 3b, first distributor 5a, second distributor 5b, first on-off valve 6a, first check valve 7a, second expansion valve 8b, third expansion valve 8c), first expansion valve 8a, and second heat exchanger 9. Second expansion valve 8b is connected between first heat exchange unit 4a and first expansion valve 8a. Third expansion valve 8c is connected between second heat exchange unit 4b and first expansion valve 8a.

[0090] With reference to Fig. 15, in the refrigeration cycle apparatus of the present embodiment, first expansion valve 8a may be provided in the indoor unit.

[0091] With reference to Fig. 16, an intermediate pressure region is formed among first expansion valve 8a, second expansion valve 8b, and third expansion valve 8c. A base cooling unit 11 may be provided in this intermediate pressure region. Base cooling unit 11 is attached to a pipe in the intermediate pressure region. Base cooling unit 11 is configured to perform heat exchange through contact with the base that issues signals to control the refrigeration cycle apparatus and activate and deactivate the refrigeration cycle apparatus.

[0092] Fig. 17 shows a schematic configuration diagram of a cross section of base cooling unit 11 as an example. Another form may be provided as long as similar effects can be achieved.

[0093] An operation of the refrigeration cycle apparatus according to Embodiment 3 which has the above configuration will now be described.

[0094] The basic cooling and heating operations are similar to those of Embodiment 1, description of which will not be repeated.

[0095] During low-outside-temperature cooling operation and low-capacity cooling/heating operation, first on-off valve 6a and third expansion valve 8c are closed, and second expansion valve 8b is opened. Consequently, the refrigerant flows from compressor 1 into flow path switching device 2, and flows through first header 3a into first heat exchange unit 4a. The refrigerant condenses in first heat exchange unit 4a, and flows through first distributor 5a and second expansion valve 8b and then into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2.

[0096] When first heat exchange unit 4a is used during high-outside temperature heating and low-capacity heating, first on-off valve 6a and third expansion valve 8c are closed, and second expansion valve 8b is opened. Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows through second expansion valve 8b and first distributor 5a into first heat exchange unit 4a. The refrigerant evaporates in first heat exchange unit 4a and returns to compressor 1 through first header 3a and flow path switching device 2.

[0097] When second heat exchange unit 4b is used during high-outside-temperature heating and low-capacity heating, first on-off valve 6a and second expansion valve 8b are closed, and third expansion valve 8c is opened. Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows through third expansion valve 8c and second distributor 5b into second heat exchange unit 4b. The refrigerant evaporates in second heat exchange unit 4b and returns to compressor 1 through second header 3b, second check valve 7b, first header 3a, and flow path switching device 2.

[0098] The effects of the refrigeration cycle apparatus according to Embodiment 3 which has the above configuration will now be described.

[0099] In the refrigeration cycle apparatus according to Embodiment 3, flow path changing device 10 includes second expansion valve 8b connected between first heat exchange unit 4a and first expansion valve 8a and third expansion valve 8c connected between second heat exchange unit 4b and first expansion valve 8a. Thus, an intermediate pressure region (intermediate pressure portion) can be formed among first expansion valve 8a, second expansion valve 8b, and third expansion valve 8c.

[0100] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating and low-capacity cooling/heating operations can change the heat exchanger by selecting a heat exchanger with a different thermal capacity.

[0101] Switching open/close of the valve of flow path changing device 10 during low-outside-temperature heating and low-capacity cooling operations can reduce heat exchanger capacity.

[0102] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating and low-capacity heating operations can increase the condensing pressure at multiple stages by the number of heat exchangers that have at least divided the heat exchanger capacity (AK value).

[0103] Switching open/close of the valve of flow path changing device 10 during low-outside-temperature cooling and low-capacity cooling operations can reduce heat exchanger capacity (AK value) to increase condensing pressure.

[0104] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can prevent start and stop of compressor 1.

[0105] Allowing the operation to be continued even during high-outside-temperature heating, low-outside temperature cooling, and low-capacity cooling/heating operations results in a wider operating range of the refrigeration cycle apparatus than a conventional operating range.

[0106] Forming an intermediate pressure portion can always set an intermediate temperature in the refrigeration cycle apparatus capable of switching between cooling and heating.

[0107] The refrigeration cycle apparatus according to Embodiment 3 includes base cooling unit 11 provided among first expansion valve 8a, second expansion valve 8b, and third expansion valve 8c. Thus, base cooling unit 11 is provided among first expansion valve 8a, second expansion valve 8b, and third expansion valve 8c, allowing dissipation of the heat of the base to the refrigerant.

[0108] Dissipating the heat of the base to the refrigerant in base cooling unit 11 can reduce the temperature of the base.

[0109] At least one temperature sensing means (not shown) is provided between the outlet of first heat exchange unit 4a and the outlet of first header 3a, between second heat exchange unit 4b and the outlet of second header 3b, and between second heat exchanger 9 and the inlet of compressor 1 to adjust the degree of superheat at and downstream of the outlet of the indoor-unit heat exchanger and adjust the degree of superheat at and downstream of the outlet of each outdoor-unit heat exchanger.

Embodiment 4

[0110] A refrigeration cycle apparatus according to Embodiment 4 of the present invention is similar to that of Embodiment 3 in basic configuration but is different therefrom in that first check valve 7a is replaced by third on-off valve 6c allowing refrigerant to flow bidirectionally. Consequently, first heat exchange unit 4a or second heat exchange unit 4b is selected during cooling, and first heat exchange unit 4a or second heat exchange unit 4b is selected during heating, thus enabling capacity control of the heat exchanger.

[0111] With reference to Fig. 18, the refrigeration cycle apparatus according to Embodiment 4 of the present invention includes compressor 1, flow path switching device 2, first heat exchanger 4 having first heat exchange unit 4a and second heat exchange unit 4b, flow path changing device 10 (first header 3a, second header 3b, first distributor 5a, second distributor 5b, third on-off valve 6c, second expansion valve 8b, third expansion valve 8c, fourth expansion valve 8d), first expansion valve 8a, and second heat exchanger 9.

[0112] With reference to Fig. 19, fourth expansion valve 8d of Fig. 18 may be replaced by first on-off valve 6a.

[0113] First expansion valve 8a may be provided indoors or outdoors.

[0114] In order to detect frost formation occurring during heating, the temperature sensing means (not shown) may be provided in the outdoor-unit heat exchanger, and the defrosting mode for switching an operation to a defrosting operation may be provided. The temperature sensing means is preferably provided as low as possible, and is further preferably provided at the lowermost portion to detect root ice.

[0115] An operation of the refrigeration cycle apparatus according to Embodiment 5 which has the above configuration will now be described.

[0116] The basic cooling and heating operations are similar to those of Embodiment 1, description of which will not be repeated.

[0117] When first heat exchange unit 4a is used during low-outside-temperature cooling operation and low-capacity cooling operation, the operation is similar to that of Embodiment 3, description of which will not be repeated.

[0118] With reference to Fig. 19, when second heat exchange unit 4b is used during low-outside-temperature cooling operation and low-capacity cooling operation, first on-off valve 6a and second expansion valve 8b are closed, and third expansion valve 8c and third on-off valve 6c are opened. Consequently, the refrigerant flows from compressor 1 into flow path switching device 2, and flows through first header 3a, third on-off valve 6c, and second header 3b into second heat exchange unit 4b. The refrigerant condenses in second heat exchange unit 4b and flows through second distributor 5b and third expansion valve 8c and then into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, flows into second heat exchanger 9. The refrigerant evaporates in second heat exchanger 9 and returns to compressor 1 through flow path switching device 2.

[0119] The operations during high-outside-temperature heating and low-capacity heating operations are similar to those of Embodiment 3, description of which will not be repeated.

[0120] With reference to Fig. 18, a frost formation prevention circuit will be described. During heating, second on-off valve 6b and second expansion valve 8b are closed, and the degrees of opening of first expansion valve 8a, third expansion valve 8c, and fourth expansion valve 8d are adjusted. Consequently, the refrigerant flows from compressor 1 through flow path switching device 2 into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9 and flows into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, forms an intermediate pressure of 0°C or higher in third expansion valve 8c and then flows through second distributor 5b into second heat exchange unit 4b. The refrigerant evaporates in second heat exchange unit 4b, flows through second header 3b, and evaporates again in fourth expansion valve 8d. The refrigerant subsequently flows through first distributor 5a, evaporates in first heat exchange unit 4a, and returns to compressor 1 through first header 3a and path switching device 2.

[0121] The effects of the refrigeration cycle apparatus according to Embodiment 4 which has the above configuration will now be described.

[0122] Switching open/close of the valve of flow path changing device 10 during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can change the heat exchanger by selecting a heat exchanger with a different heat exchanger capacity and can also form an intermediate pressure portion among first expansion valve 8a, second expansion valve 8b, and third expansion valve 8c.

[0123] The heat exchanger provided at the lower portion is set to an intermediate pressure upon detection of frost formation during heating, thus preventing root ice.

Embodiment 5

[0124] A refrigeration cycle apparatus according to Embodiment 5 of the present invention is similar to that of Embodiment 1 in basic configuration, but is different therefrom in that flow path switching device 2 is provided with first four-way valve 2a and second four-way valve 2b to form a circuit.

[0125] With reference to Fig. 20, the refrigeration cycle apparatus according to Embodiment 5 of the present invention includes compressor 1, flow path switching device 2 having first four-way valve 2a and second four-way valve 2b, first heat exchanger 4 having first heat exchange unit 4a and second heat exchange unit 4b, flow path changing device 10 (first on-off valve 6a, second on-off valve 6b, third on-off valve 6c, second expansion valve 8b, third expansion valve 8c), first expansion valve 8a, and the second heat exchanger. First four-way valve 2a is connected to first heat exchange unit 4a. Second four-way valve 2b is connected to second heat exchange unit 4b. First four-way valve 2a is connected to second four-way valve. The second expansion valve is connected between second heat exchange unit 4b and third on-off valve 6c.

[0126] With reference to Fig. 21, in the refrigeration cycle apparatus according to the present embodiment, second expansion valve 8b may be connected between second heat exchange unit 4b and second on-off valve 6b.

[0127] First expansion valve 8a may be provided between the branch points of second expansion valve 8b and third expansion valve 8c on the outdoor unit side.

[0128] First header 3a, second header 3b, first distributor 5a, and second distributor 5b (or third header 3c, fourth header 3d of Fig. 8), which are unshown, may be provided upstream and downstream of first heat exchange unit 4a and second heat exchange unit 4b.

[0129] Base cooling unit 11 of Fig. 16 may be provided among first expansion valve 8a, second expansion valve 8b, and third expansion valve 8c.

[0130] Description will now be given of an operation of the refrigeration cycle apparatus according to Embodiment 5 which has the above configuration.

[0131] During cooling, first four-way valve 2a and second four-way valve 2b are switched to the cooling mode (solid line). Also, first on-off valve 6a and second on-off valve 6b are opened, third on-off valve 6c is closed, third expansion valve 8c is closed, and second expansion valve 8b is opened. Consequently, first heat exchange unit 4a and second heat exchange unit 4b are connected in series. This allows the refrigerant to flow from compressor 1 into second four-way valve 2b and flow into first heat exchange unit 4a. The refrigerant condenses in first heat exchange unit 4a and flows through first on-off valve 6a and second on-off valve 6b into second heat exchange unit 4b. The refrigerant further condenses in second heat exchange unit 4b, flows through second expansion valve 8b, and expands in first expansion valve 8a. The refrigerant subsequently evaporates in second heat exchanger 9 and returns to compressor 1 through first four-way valve 2a.

[0132] During heating, first four-way valve 2a and second four-way valve 2b are switched to the heating mode (broken line). Also, first on-off valve 6a, second on-off valve 6b, and third on-off valve 6c are opened, third expansion valve 8c is opened, and second expansion valve 8b is closed. Consequently, first heat exchange unit 4a and second heat exchange unit 4b are connected in parallel. This allows the refrigerant to flow from compressor 1 through first four-way valve 2a into second heat exchanger 9. The refrigerant condenses in second heat exchanger 9, flows through first expansion valve 8a and third expansion valve 8c, and is then branched to first on-off valve 6a and second on-off valve 6b. The refrigerant that has flowed through first on-off valve 6a evaporates in first heat exchange unit 4a and returns to compressor 1 through second four-way valve 2b. The refrigerant that has flowed through second on-off valve 6b evaporates in second heat exchange unit 4b and returns to compressor 1 through third on-off valve 6c and first four-way valve 2a.

[0133] When first heat exchange unit 4a is used during low-outside-temperature cooling operation and low-capacity cooling operation, first four-way valve 2a and second four-way valve 2b are switched to the cooling mode (solid line). Also, first on-off valve 6a is opened, second on-off valve 6b and third on-off valve 6c are closed, second expansion valve 8b is closed, and third expansion valve 8c is opened. Consequently, the refrigerant flows from compressor 1 through second four-way valve 2b into first heat exchange unit 4a. The refrigerant condenses in first heat exchange unit 4a, and flows through first on-off valve 6a and third expansion valve 8c and then into first expansion valve 8a. The refrigerant expands in first expansion valve 8a, and subsequently, evaporates in second heat exchanger 9 and returns to compressor 1 through first four-way valve 2a.

[0134] When second heat exchange unit 4b is used during low-outside-temperature cooling operation and low-capacity cooling operation, first four-way valve 2a is switched to the cooling mode (solid line), and second four-way valve 2b is switched to the heating mode (broken line). Also, first on-off valve 6a is closed, second on-off valve 6b and third on-off valve 6c are opened, second expansion valve 8b is closed, and third expansion valve 8c is opened. Consequently, the refrigerant flows from compressor 1 through first four-way valve 2a and third on-off valve 6c into second heat exchange unit 4b. The refrigerant condenses in second heat exchange unit 4b, flows through second on-off valve 6b and third expansion valve 8c, and expands in first expansion valve 8a. The refrigerant subsequently evaporates in second heat exchanger 9, and returns to compressor 1 through first four-way valve 2a. At this time, first heat exchange unit 4a enters the low pressure state by second four-way valve 2b being switched to the heating mode (broken line).

[0135] When first heat exchange unit 4a is used during high-outside-temperature heating and low-capacity heating, first four-way valve 2a and second four-way valve 2b are switched to the heating mode (broken line). Also, first on-off valve 6a is opened, second on-off valve 6b, third on-off valve 6c, and second expansion valve 8b are closed, and third expansion valve 8c is opened. Consequently, the refrigerant flows from compressor 1 through first four-way valve 2a, condenses in second heat exchanger 9, and expands in first expansion valve 8a. The refrigerant subsequently flows through third expansion valve 8c and first on-off valve 6a, evaporates in first heat exchange unit 4a, and returns to compressor 1 through second four-way valve 2b.

[0136] When second heat exchange unit 4b is used during high-outside-temperature heating and low-capacity heating, first four-way valve 2a and second four-way valve 2b are switched to the heating mode (broken line). Also, first on-off valve 6a is closed, second on-off valve 6b and third on-off valve 6c are opened, second expansion valve 8b is closed, and third expansion valve 8c is opened. Consequently, the refrigerant flows from compressor 1 through first four-way valve 2a, condenses in second heat exchanger 9, and expands in first expansion valve 8a. The refrigerant subsequently flows through third expansion valve 8c and second on-off valve 6b, evaporates in second heat exchange unit 4b, and returns to compressor 1 through first four-way valve 2a. At this time, first heat exchange unit 4a enters the low pressure state by second four-way valve 2b being switched to the heating mode (broken line).

[0137] The effects of the refrigeration cycle apparatus according to Embodiment 5 which has the above configuration will now be described.

[0138] Switching open/close of the valve of flow path changing device during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operations can change the heat exchanger by selecting a heat exchanger with a different heat exchanger capacity and can also form an intermediate pressure portion among first expansion valve 8a, second expansion valve 8b, and third expansion valve 8c.

[0139] The circuit configuration shown in Fig. 21 allows an expansion valve to be provided upstream of each outdoor-unit heat exchanger during heating.

[0140] Providing the expansion valve upstream of each outdoor-unit heat exchanger enables adjustment of the refrigerant amount flowing into each outdoor-unit heat exchanger.

[0141] In the refrigeration cycle apparatus according to Embodiment 5, switching between first four-way valve 2a and second four-way valve 2b causes one of first heat exchange unit 4a and second heat exchange unit 4b, which is not used, to enter the low pressure state when the other of first heat exchange unit 4a and second heat exchange unit 4b is used. That is to say, switching between first four-way valve 2a and second four-way valve 2b allows the unused heat exchange unit to enter the low pressure state during capacity control in which any one of first heat exchange unit 4a and second heat exchange unit 4b is used. For example, an unused heat exchange unit (first heat exchange unit 4a) can be brought to the low pressure state during capacity control in which second heat exchange unit 4b alone is used.

[0142] The heat exchanger through which no refrigerant flows is brought to the low pressure state, thus preventing condensation of refrigerant due to natural heat dissipation without physically interrupting a circuit (e.g., closing second on-off valve 6b, third on-off valve 6c, and second expansion valve 8b).

[0143] Preventing the condensation of refrigerant due to natural heat dissipation can prevent the refrigerant from remaining in the heat exchanger.

[0144] Preventing the refrigerant from remaining in the heat exchanger can prevent a lack of refrigerant during capacity control.

Embodiment 6

[0145] A refrigeration cycle apparatus according to Embodiment 6 of the present invention is similar to that of Embodiment 1 in basic configuration but is different therefrom in that at least one outdoor unit and at least one indoor unit are combined to form a circuit such that the number of any one of them is greater than unity. In the refrigeration cycle apparatus according to Embodiment 6 of the present invention, at least any one of first heat exchanger 4 and second heat exchanger 9 may be divided into two or more parts.

[0146] With reference to Fig. 22, the refrigeration cycle apparatus according to Embodiment 6 of the present invention includes a first outdoor unit, a second outdoor unit, a first indoor unit, and a second indoor unit.

[0147] The first outdoor unit includes first compressor 1a, first four-way valve 2a, first heat exchanger 4 having first heat exchange unit 4a and second heat exchange unit 4b, and flow path changing device 10 (first header 3a, second header 3b, first distributor 5a, second distributor 5b, first on-off valve 6a, first check valve 7a, second expansion valve 8b, third expansion valve 8c).

[0148] The second outdoor unit includes second compressor 1b, second four-way valve 2b, first heat exchanger 4 having a third heat exchange unit 4c and a fourth heat exchange unit 4d, and flow path changing device 10 (third header 3c, fourth header 3d, a third distributor 5c, a fourth distributor 5d, second on-off valve 6b, second check valve 7b, a fifth expansion valve 8e, a sixth expansion valve 8f).

[0149] The first indoor unit includes first expansion valve 8a and a second heat exchanger 9a. The second indoor unit includes fourth expansion valve 8d and second heat exchanger 9b.

[0150] At least one outdoor unit and at least one indoor unit may be provided such that the number of any one of them is greater than unity: for example, a first indoor unit to an N-th indoor unit are provided for one first outdoor unit, or a first indoor unit is provided for a first outdoor unit to an N-th outdoor unit.

[0151] For the flow path changing device, not only the configuration shown in Fig. 22, but also a flow path changing device described in any other embodiment may be used depending on a use. The components for the flow path changing device may be combined to form a flow path changing device as long as similar effects can be achieved.

[0152] The intermediate pressure portion may be provided with unshown base cooling unit 11 (see Fig. 16).

[0153] Fig. 23 is a schematic configuration diagram showing a configuration including a similar flow path changing device also in an indoor-unit heat exchanger. The configuration is made such that a parallel connection is provided during cooling and a series connection is provided during heating, and that a first indoor-unit heat exchanger 9a' is greater than a second indoor-unit heat exchanger 9" in heat exchanger capacity and flow path.

[0154] Also for the indoor unit, not only the configuration shown in Fig. 23, but also a flow path changing device described in any other embodiment may be used depending on a use. The components for the flow path changing device may be combined to form a flow path changing device as long as similar effects can be achieved. Alternatively, the configuration shown in Fig. 23 may be used to form an indoor unit in Embodiments 1 to 5.

[0155] Description will now be given of an operation of the refrigeration cycle apparatus according to Embodiment 6 which has the above configuration.

[0156] A basic operation is similar to that of Embodiment 3, description of which will not be repeated.

[0157] An operation of allowing only the first outdoor unit or the second outdoor unit to operate may be performed depending on the capability required for the indoor unit.

[0158] When the heat exchanger capacity is changed, for example, the capacity may be changed by combining first heat exchange unit 4a and third heat exchange unit 4c or combining second heat exchange unit 4b and fourth heat exchange unit 4d.

[0159] The effects of the refrigeration cycle apparatus according to Embodiment 6 which has the above configuration will now be described.

[0160] In the refrigeration cycle apparatus according to Embodiment 6, at least any one of first heat exchanger 4 and second heat exchanger 9 is divided into two or more parts. Consequently, heat exchange can be performed by first heat exchangers 4 or second heat exchangers 9. This improves heat exchange performance.

[0161] Switching open/close of the valve of the flow path changing device during high-outside-temperature heating, low-outside-temperature cooling, and low-capacity cooling/heating operation can change the heat exchanger by selecting a heat exchanger with a different thermal capacity, and can also form an intermediate pressure portion among first expansion valve 8a, second expansion valve 8b, third expansion valve 8c, fourth expansion valve 8d, fifth expansion valve 8e, and sixth expansion valve 8f.

[0162] Providing a region, which is set to an intermediate pressure even by combining at least one outdoor unit and at least one indoor unit such that the number of any one of them is greater than unity, allows control of a refrigerant amount flowing through each indoor unit such as the first outdoor unit or second outdoor unit. Thus, the refrigerant can be distributed evenly.

[0163] The above embodiments can be combined as appropriate.

[0164] It should be construed that the embodiments disclosed herein are given by way of illustration in all respects, not by way of limitation. It is therefore intended that the scope of the present invention is defined by claims, not only by the embodiments described above, and encompasses all modifications and variations equivalent in meaning and scope to the claims.

REFERENCE SIGNS LIST

[0165] 1 compressor, 2 flow path switching device, 2a first four-way valve, 2b second four-way valve, 3a first header, 3b second header, 4 first heat exchanger, 4a first heat exchange unit, 4b second heat exchange unit, 5a first distributor, 5b second distributor, 6a first on-off valve, 6b second on-off valve, 7a first check valve, 8a first expansion valve, 8b second expansion valve, 9 second heat exchanger, 10 flow path changing device, 11 base cooling unit.

Claims

1. A refrigeration cycle apparatus comprising:

a compressor configured to compress refrigerant;

a flow path switching device connected to the compressor;

a first heat exchanger connected to the flow path switching device and having a first heat exchange unit and a second heat exchange unit;

a flow path changing device connecting the first heat exchange unit and the second heat exchange unit to each other;

a first expansion valve connected to the first heat exchange unit and the second heat exchange unit; and

a second heat exchanger connected to the first expansion valve and the flow path switching device,

the flow path switching device being configured to switch flow of the refrigerant compressed by the compressor between flow to the first heat exchanger and flow to the second heat exchanger,

the flow path changing device being configured to switch flow of the refrigerant among flow successively through the first heat exchange unit and the second heat exchange unit, flow in parallel through the first heat exchange unit and the second heat exchange unit, and flow through any one of the first heat exchange unit and the second heat exchange unit.

2. The refrigeration cycle apparatus according to claim 1, wherein
the first heat exchange unit has a first heat exchanger capacity and at least one first flow path,
the second heat exchange unit has a second heat exchanger capacity and at least one second flow path,
the first heat exchanger capacity is greater than the second heat exchanger capacity, and
a number of the at least one first flow path is greater than a number of the at least one second flow path.

3. The refrigeration cycle apparatus according to claim 1 or 2, wherein the flow path changing device is configured to
when the flow path switching device causes the refrigerant compressed by the compressor to flow through the first heat exchanger, switch flow of the refrigerant between flow successively through the first heat exchanger unit and the second heat exchanger unit and flow through the first heat exchange unit alone, and
when the flow path switching device causes the refrigerant compressed by the compressor to flow through the second heat exchanger, switch flow of the refrigerant between flow in parallel through the first heat exchange unit and the second heat exchange unit and flow through the second heat exchange unit alone.

4. The refrigeration cycle apparatus according to claim 1 or 2, wherein the flow path changing device is configured to
when the flow path switching device causes the refrigerant compressed by the compressor to flow through the first heat exchanger, switch flow of the refrigerant between flow successively through the first heat exchanger unit and the second heat exchanger unit and flow through any one of the first heat exchange unit and the second heat exchange unit by selecting one heat exchange unit, and
when the flow path switching device causes the refrigerant compressed by the compressor to flow through the second heat exchanger, switch flow of the refrigerant between flow in parallel through the first heat exchange unit and the second heat exchange unit and flow through any one of the first heat exchange unit and the second heat exchange unit by selecting one heat exchange unit.

5. The refrigeration cycle apparatus according to any one of claims 1 to 4, wherein the flow path changing device comprises
a second expansion valve connected between the first heat exchange unit and the first expansion valve, and
a third expansion valve connected between the second heat exchange unit and the first expansion valve.

6. The refrigeration cycle apparatus according to claim 5, further comprising a base cooling unit provided among the first expansion valve, the second expansion valve, and the third expansion valve.

7. The refrigeration cycle apparatus according to any one of claims 1 to 6, wherein
the flow path switching device has a first four-way valve and a second four-way valve,
the first four-way valve is connected to the first heat exchange unit,
the second four-way valve is connected to the second heat exchange unit and the first four-way valve,
by switching between the first four-way valve and the second four-way valve, one of the first heat exchange unit and the second heat exchange unit which is not used has low pressure when the other of the first heat exchange unit and the second heat exchange unit is used.

8. The refrigeration cycle apparatus according to any one of claims 1 to 7, wherein at least one of the first heat exchanger and the second heat exchanger is divided into two or more parts.

Drawing