GB2578533A

GB2578533A - Refrigeration cycle device

Info

Publication number: GB2578533A
Application number: GB1918816.8A
Authority: GB
Inventors: Okamoto Kei; Mieno Jun; Fujimoto Hajime
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-08-03
Filing date: 2017-08-03
Publication date: 2020-05-13
Anticipated expiration: 2037-08-03
Also published as: JP6861821B2; JPWO2019026234A1; GB2578533B; WO2019026234A1; GB201918816D0

Abstract

This refrigeration cycle device has: a plurality of refrigerant circuits, each having a compressor, heat source-side heat exchanger, and decompression device, which are connected to each other; and a heat medium circuit having a plurality of heat medium heat exchangers, which are provided to the refrigerant circuits, respectively, and which exchange heat between a refrigerant and a heat medium. The heat medium circuit is provided with a flow channel switching device that performs switching between a series flow channel wherein the heat medium heat exchangers are connected in series, and a parallel flow channel wherein the heat medium heat exchangers are connected in parallel.

Description

DESCRIPTION Title of Invention

REFRIGERATION CYCLE APPARATUS

Technical Field

[0001] The present invention relates to a refrigeration cycle apparatus that exchanges heat between a heat medium, such as water and brine, and refrigerant heated or cooled by a refrigeration cycle, and supplies cooling or heating energy to a load side flow passage.

Background Art

[0002] As an example of a refrigeration cycle apparatus that supplies cooling and heating energy to a load side flow passage, a cooler having a condenser, and two evaporators connected in parallel to the condenser is disclosed (for example, refer to Patent Literature 1). In the cooler disclosed Patent Literature 1, a pipe is installed through which a heat medium for exchanging heat with refrigerant in the two evaporators flows in such a manner that the two evaporators are connected in series. The heat medium is cooled by the two evaporators stepwise. In this cooler, among the two evaporators connected in series, the evaporating temperature of the evaporator in the first step is set to higher than the evaporating temperature of the evaporator in the second step so that operation having high refrigerating efficiency is performed. Citation List Patent Literature [0003] Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2006-329601

Summary of Invention

Technical Problem [0004] In the cooler disclosed in Patent Literature 1, a pressure loss received by the heat medium is increased as the number of evaporators connected in series, through which the heat medium passes, is increased. The amount of the pressure loss depends on the viscosity and the speed of the heat medium. In a case in which the viscosity of the heat medium is high, connecting a plurality of evaporators in series leads to an increase in a load on a pump. On the other hand, it is conceivable to dispose a plurality of evaporators in parallel. However, the refrigerating efficiency in a configuration in which a plurality of evaporators are connected in parallel is reduced by several percent compared to that in a configuration in which a plurality of evaporators are connected in series.

[0005] The present invention has been made to solve the aforementioned problem, and provides a refrigeration cycle apparatus in which influence of a pressure loss is reduced, and operating efficiency is improved.

Solution to Problem [0006] A refrigeration cycle apparatus according to an embodiment of the present invention has a plurality of refrigerant circuits each having a compressor, a heat source side heat exchanger, and a pressure reducing device connected to each other; and a heat medium circuit having a plurality of heat medium heat exchangers each provided to the corresponding one of the plurality of refrigerant circuits, the plurality of heat medium heat exchangers being each configured to exchange heat between refrigerant and a heat medium. The heat medium circuit includes a flow switching device configured to switch between a series flow passage in which the plurality of heat medium heat exchangers are connected in series, and a parallel flow passage in which the plurality of heat medium heat exchangers are connected in parallel.

Advantageous Effects of Invention [0007] According to an embodiment of the present invention, a flow passage having higher operating efficiency among a series flow passage and a parallel flow passage can be formed in a heat medium circuit, and therefore it is possible to improve operating efficiency as a whole apparatus.

Brief Description of Drawings

[0008] [Fig. 1] Fig. 1 is a diagram illustrating a configuration example of a refrigeration cycle apparatus of Embodiment 1 of the present invention [Fig. 2] Fig. 2 is a function block diagram illustrating a configuration example of a controller illustrated in Fig. 1.

[Fig. 3] Fig. 3 is a diagram illustrating a configuration in which a series flow passage is formed in a heat medium circuit illustrated in Fig. 1.

[Fig. 4] Fig. 4 is a diagram illustrating a configuration in which a parallel flow passage is formed in the heat medium circuit illustrated in Fig. 1.

[Fig. 5] Fig. 5 is a diagram illustrating a configuration in which a partial system flow passage is formed in the heat medium circuit illustrated in Fig. 1.

[Fig. 6] Fig. 6 is a diagram illustrating a configuration in which another partial system flow passage different from the partial system flow passage illustrated in Fig. 5 is formed.

[Fig. 7] Fig. 7 is a flowchart illustrating an example of a procedure of a flow passage selection performed by the controller illustrated in Fig. 2.

[Fig. 8] Fig. 8 is a diagram illustrating a configuration example of a refrigeration cycle apparatus of Embodiment 2 of the present invention.

Description of Embodiments

[0009] Embodiment 1 A configuration of a refrigeration cycle apparatus of Embodiment 1 will be described. Fig. 1 is a diagram illustrating a configuration example of a refrigeration cycle apparatus of Embodiment 1 of the present invention. As illustrated in Fig. 1, a refrigeration cycle apparatus 1 has refrigerant circuits 2a and 2b, and a heat medium circuit 30 including heat medium heat exchangers 6a and 6b, each of the heat medium heat exchangers 6a and 6b being configured to exchange heat between a heat medium and refrigerant that circulates in the corresponding one of the refrigerant circuits 2a and 2b. In the refrigeration cycle apparatus 1, a controller 40 is provided.

The heat medium circuit 30 is connected to a load side unit 60. The heat medium that circulates between the load side unit 60 and the heat medium circuit 30 is water or brine.

[0010] The refrigerant circuits 2a and 2b each supply heat generated in its refrigeration cycle to the heat medium circuit 30. The refrigerant circuit 2a has a compressor 3a, a heat source side heat exchanger 4a, and a pressure reducing device 5a. To the heat source side heat exchanger 4a, a fan 7a that supplies outdoor air to the heat source side heat exchanger 4a is provided. The refrigerant circuit 2a is connected to the heat medium heat exchanger 6a. The refrigerant circuit 2b has a compressor 3b, a heat source side heat exchanger 4b, and a pressure reducing device 5b. To the heat source side heat exchanger 4b, a fan 7b that supplies outdoor air to the heat source side heat exchanger 4b is provided. The refrigerant circuit 2b is connected to the heat medium heat exchanger 6b. The refrigerant circuits 2a and 2b have the same configuration, and therefore the configuration of the refrigerant circuit 2a will be described.

[0011] The compressor 3a compresses refrigerant to discharge the compressed refrigerant. The compressor 3a is an inverter compressor that controls a rotation frequency by an inverter, and changes capacity by the rotation frequency. The compressor 3a may be a compressor that has a constant rotation frequency, and changes capacity by another method. The heat source side heat exchanger 4a exchanges heat between refrigerant and air, and is, for example, a plate fin heat exchanger. The heat source side heat exchanger 4a is used as a condenser of the refrigerant circuit 2a. The pressure reducing device 5a expands refrigerant. The pressure reducing device 5a may be an electronic expansion valve capable of adjusting an opening degree, or may be a capillary tube.

[0012] The capacity control of each of the compressors 3a and 3b is not limited to rotation frequency control by an inverter, and other control may be used. For example, capacity control of mechanically changing stroke volume of each of the compressors 3a and 3b may be used. A plurality of compressors 3a may be provided in each of the refrigerant circuits 2a and 2b, and the number of the compressors 3a that are operated is changed so that the capacity control of the compressor may be performed. In these cases, operation of each of compressors 3a and 3b is controlled similarly to the case in which the rotation frequency is controlled by the inverter so that balanced operation of the refrigeration cycles of the refrigerant circuits 2a and 2b can be achieved, and it is possible to achieve highly efficient refrigeration cycle operation.

[0013] The configurations of the heat source side heat exchangers 4a and 4b are not limited to plate fin heat exchangers, and may be, for example, other heat exchangers such as corrugated fin heat exchangers. In each of the heat source side heat exchangers 4a and 4b, an object to be heat-exchanged with refrigerant is not limited to air, and may be other medium such as water.

[0014] The heat medium circuit 30 exchanges heat between the heat medium and the refrigerant that circulates in each of the refrigerant circuits 2a and 2b, and then supplies, to the load side unit 60, the heat medium obtained after the heat exchange. To a heat medium inflow port of the heat medium circuit 30, a pipe 31 for returning the heat medium from the load side unit 60 to the heat medium circuit 30 is connected.

To a heat medium outflow port of the heat medium circuit 30, a pipe 32 for supplying the heat medium from the heat medium circuit 30 to the load side unit 60 is connected. The pipe 31 is branched into a pipe 33 that passes through the heat medium heat exchanger 6a, and a pipe 34 that passes through the heat medium heat exchanger 6b. The pipe 33 and the pipe 34 are joined and connected to the pipe 32.

[0015] The load side unit 60, the pipe 31, and the pipe 32 are connected, so that a load side flow passage in which the heat medium circulates is configured. In the pipe 31, a heat medium delivery device 8 is provided as power to circulate the heat medium in the load side unit 60. The heat medium delivery device 8 is a pump.

While Fig. 1 illustrates a case in which the heat medium delivery device 8 is provided outside the refrigeration cycle apparatus 1, the heat medium delivery device 8 may be provided inside the refrigeration cycle apparatus 1.

[0016] The heat medium circuit 30 has a plurality of the heat medium heat exchangers 6a and 6b. The heat medium heat exchanger 6a exchanges heat between the refrigerant that circulates in the refrigerant circuit 2a, and the heat medium, and is, for example, a plate heat exchanger. The heat medium heat exchanger 6a is used as an evaporator of the refrigerant circuit 2a. The heat medium heat exchanger 6b exchanges heat between the refrigerant that circulates in the refrigerant circuit 2b, and the heat medium, and is, for example, a plate heat exchanger The heat medium heat exchanger 6b is used as an evaporator of the refrigerant circuit 2b. [0017] The configurations of the heat medium heat exchangers 6a and 6h are not limited to the plate heat exchangers, and may be other heat exchangers. The heat medium heat exchangers 6a and 6b may be, for example, shell-tube or double pipe heat exchangers. The heat medium that circulates between the heat medium circuit 30 and the load side unit 60 is not limited to water or brine, and may be other medium as long as the medium receives heat through sensible heat.

[0018] In Embodiment 1, the heat medium heat exchanger 6a and the heat medium heat exchanger 6b each have a configuration in which the refrigerant and the heat medium flow in directions opposite to each other The heat exchange is performed in a state in which the refrigerant and the heat medium flow in directions opposite to each other, and therefore efficiency of the heat exchange is improved.

[0019] In Embodiment 1, the heat medium heat exchanger 6a and the heat medium heat exchanger 6b are each a single heat exchanger. However, the heat medium heat exchanger 6a and the heat medium heat exchanger 6b may be formed integrally.

In this case, in the refrigeration cycle apparatus 1, it is possible to reduce an installation area occupied by the heat medium heat exchanger, and save space. [0020] In the configuration illustrated in Fig. 1, the heat source side heat exchangers 4a and 4b are used as condensers, and the heat medium heat exchangers 6a and 6b are used as respective evaporators of the refrigerant circuits 2a and 2b. However, the heat source side heat exchangers 4a and 4b may be used as evaporators. In this case, the refrigerant circuits 2a and 2b each provide heating energy for the heat medium circuit 30.

[0021] The heat medium circuit 30 has the flow switching device 50 that switches a series flow passage in which the heat medium heat exchangers 6a and 6b are connected in series, and a parallel flow passage in which the heat medium heat exchangers 6a and 6b are connected in parallel, and a partial system flow passage in which the refrigerant flows through the heat medium heat exchanger 6a or 6b. The flow switching device 50 has a pipe 35 connecting the downstream port of the heat medium heat exchanger 6b and the upstream port of the heat medium heat exchanger 6a, a first valve 9 that controls inflow of the heat medium to the heat medium heat exchanger 6a and the pipe 35, and a second valve 11 that control outflow of the heat medium from the heat medium heat exchanger 6b. In Embodiment 1, a third valve 10 is provided in the pipe 35. The first valve 9, the second valve 11, and the third valve 10 are each, for example, a solenoid valve. [0022] The first valve 9 is provided in a portion of the pipe 33 that is between the pipe 31 and the heat medium heat exchanger 6a and provided upstream of a place at which the pipe 35 is connected to the pipe 33. The second valve 11 is provided in a portion of the pipe 34 that is between the heat medium heat exchanger 6b and the pipe 32 and provided downstream of a place at which the pipe 35 is connected to the pipe 34. The pipe 35 is connected to a portion of the pipe 33 that is between the first valve 9 and the heat medium heat exchanger 6a, and is connected to a portion of the pipe 34 that is between the second valve 11 and the heat medium heat exchanger 6b.

The first valve 9, the second valve 11, and the third valve 10 are two-way valves, and control the flow of the heat medium by opening and closing. A three-way valve may be provided in place of the first valve 9 and the third valve 10. A three-way valve may be provided in place of the second valve 11 and the third valve 10.

[0023] As illustrated in Fig. 1, the refrigeration cycle apparatus 1 has an inlet pressure sensor 12 that measures the inlet pressure of the heat medium that flows into the heat medium circuit 30, and an outlet pressure sensor 13 that measures the outlet pressure of the heat medium that flows out of the heat medium circuit 30. In the configuration example illustrated in Fig. 1, the inlet pressure sensor 12 is provided in the pipe 31, and the outlet pressure sensor 13 is provided in the pipe 32. A flowmeter 45 that measures the flow rate of the heat medium that flows into the pipe 32 is provided in the pipe 32.

[0024] Fig. 2 is a function block diagram illustrating a configuration example of the controller illustrated in Fig. 1. The controller 40 illustrated in Fig. 1 is, for example, a microcomputer The controller 40 has a memory that stores a program, and a central processing unit (CPU) that executes a process in accordance with the program. In Fig. 2, illustration of the memory and the CPU is omitted.

[0025] The controller 40 is connected to the inlet pressure sensor 12, the outlet pressure sensor 13, and the flowmeter 45 by signal lines. The controller 40 is connected to the compressors 3a and 3b, the fans 7a and 7b, and the pressure reducing devices 5a and 5b by signal lines. The controller 40 is connected to the flow switching device 50 by a signal line. More specifically, the controller 40 is connected to the first valve 9, the second valve 11, and the third valve 10 by signal lines. The controller 40 is connected to the heat medium delivery device 8 by a signal line. In Embodiment 1, a case will be described in which a wired communication is used to communicate with devices, sensors, and the controller 40 each other. However, a wireless communication may also be used.

[0026] As illustrated in Fig. 2, the controller 40 has a refrigeration cycle control unit 41, an efficiency calculation unit 42, and a flow passage determination unit 43 The refrigeration cycle control unit 41 controls the operation frequencies of the compressors 3a and 3b, the rotation frequencies of the fans 7a and 7b, the opening degrees of the pressure reducing devices 5a and 5b, and the rotation frequency of the heat medium delivery device 8, in accordance with a heat quantity required by the load side unit 60. When the operation of the refrigerant circuits 2a or 2b is stopped, the refrigeration cycle control unit 41 transmits operation stop information including the information of the refrigerant circuit whose operation is stopped to the flow passage determination unit 43 through the efficiency calculation unit 42. The refrigeration cycle control unit 41 controls a refrigeration cycle in accordance with the flow passage formed in the heat medium circuit 30.

[0027] The efficiency calculation unit 42 calculates a pressure difference between the inlet pressure and the outlet pressure of the heat medium circuit 30 as a pressure loss in the heat medium circuit 30. The efficiency calculation unit 42 may calculate a pressure loss by use of the flow rate measured by the flowmeter 45. The efficiency calculation unit 42 calculates a value used for determination of flow passage selection by use of the calculated pressure loss. The flow passage determination unit 43 compares the value calculated by the efficiency calculation unit 42 with a set value, and selects the flow passage to be formed in the heat medium circuit 30 from the series flow passage and the parallel flow passage. When the flow passage determination unit 43 receives the operation stop information from the refrigeration cycle control unit 41 through the efficiency calculation unit 42, the flow passage determination unit 43 selects one flow passage among two of the partial system flow passages in accordance with the operation stop information. The flow passage determination unit 43 controls the flow switching device 50 in accordance with the selected flow passage. The flow passage determination unit 43 notifies the refrigeration cycle control unit 41 of the selected flow passage.

[0028] A case in which the series flow passage is formed in the heat medium circuit 30 illustrated in Fig. 1 will be described below. Fig. 3 is a diagram illustrating a configuration in which the series flow passage is formed in the heat medium circuit illustrated in Fig. 1. In Fig. 3, the direction in which the heat medium flows is illustrated by the arrows. The flow passage determination unit 43 sets the first valve 9 to a closed state, sets the third valve 10 to an open state, and sets the second valve 11 to a closed state. Consequently, the heat medium heat exchanger 6b and the heat medium heat exchanger 6a are connected in series. At this time, the pipe 35 is used as a connection flow passage in which the heat medium heat exchangers 6a and 6b are connected in series.

[0029] In the configuration illustrated in Fig. 3, the heat medium flows into the pipe 34 from the pipe 31, and flows through the heat medium heat exchanger 6b to flow out to the pipe 35. Then, the heat medium flows into the pipe 33 from the pipe 35, and flows through the heat medium heat exchanger 6a to flow out of the pipe 33 to the pipe 32. Thus, the series flow passage in which the heat medium sequentially flows through the heat medium heat exchanger 6b, the connection flow passage, and the heat medium heat exchanger 6a is formed in the heat medium circuit 30.

[0030] A case in which the parallel flow passage is formed in the heat medium circuit 30 illustrated in Fig. 1 will be described below. Fig. 4 is a diagram illustrating a configuration in which the parallel flow passage is formed in the heat medium circuit illustrated in Fig. 1. The flow passage determination unit 43 sets the first valve 9 to an open state, sets the third valve 10 to a closed state, and sets the second valve 11 to an open state. Consequently, the heat medium heat exchanger 6b and the heat medium heat exchanger 6a are connected in parallel.

[0031] In the configuration illustrated in Fig. 4, the heat medium is divided into the pipes 33 and 34 from the pipe 31. The heat medium that flows in the pipe 33 flows through the heat medium heat exchanger 6a. On the other hand, the heat medium that flows in the pipe 34 flows through the heat medium heat exchanger 6b. The heat medium that flows in the pipe 33, and the heat medium that flows in the pipe 34 merge and flow out to the pipe 32. Thus, the parallel flow passage including the flow passage in which the heat medium flows in the heat medium heat exchanger 6a, and the flow passage in which the heat medium flows in the heat medium heat exchanger 6b is formed in the heat medium circuit 30.

[0032] A case in which the partial system flow passage is formed in the heat medium circuit 30 illustrated in Fig. 1 will be described below. Fig. 5 is a diagram illustrating a configuration in which the partial system flow passage is formed in the heat medium circuit illustrated in Fig. 1. Fig. 5 illustrates a case in which while the refrigerant circuit 2b of the refrigerant circuits 2a and 2b is operated, the refrigerant circuit 2a stops operation. The flow passage determination unit 43 sets the first valve 9 and the third valve 10 to the closed states, and sets the second valve 11 to the open state.

In the configuration illustrated in Fig. 5, the heat medium flows into the pipe 34 from the pipe 31, and flows through the heat medium heat exchanger 6b, and then flows out of the pipe 34 to the pipe 32. Thus, the partial system flow passage in which the heat medium does not flow through the heat medium heat exchanger 6a, but flows through the heat medium heat exchanger 6b is formed in the heat medium circuit 30.

[0033] Fig. 6 is a diagram illustrating a configuration in which another partial system flow passage different from the partial system flow passage illustrated in Fig. 5 is formed. Fig. 6 illustrates a case in which while the refrigerant circuit 2a of the refrigerant circuits 2a and 2b is operated, the refrigerant circuit 2b stops operation.

The flow passage determination unit 43 sets the first valve 9 to the open state, and sets the second valve 11 and the third valve 10 to the closed states. In the configuration illustrated in Fig. 6, the heat medium flows into the pipe 33 from the pipe 31, and flows through the heat medium heat exchanger 6a, and then flows out of the pipe 33 to the pipe 32. Thus, the partial system flow passage in which the heat medium does not flow through the heat medium heat exchanger 6b, but flows through the heat medium heat exchanger 6a is formed in the heat medium circuit 30. [0034] A case in which the controller 40 selects a flow passage to be formed in the heat medium circuit 30 will be described below. The flow passage determination unit 43 compares refrigerating efficiency with power efficiency of the heat medium delivery device 8 that are different between the flow passages formed in the heat medium circuit 30, and selects a flow passage having higher operating efficiency.

[0035] A coefficient of performance (COP) of the refrigeration cycle is typically represented by COP = (usable heat quantity [kW]/input to a compressor [kW]). On the basis of this expression of the coefficient of performance, a ratio of a usable heat quantity to the power efficiency of the heat medium delivery device 8 is used as the coefficient of performance, and is calculated for each of the flow passages. A coefficient of series performance that is a coefficient of performance in a case of the series flow passage is denoted by COPs, and a coefficient of parallel performance that is a coefficient of performance in a case of the parallel flow passage is denoted by COPp.

[0036] A heat quantity generated by the refrigerant circuits 2a and 2b in the case of the series flow passage is denoted by Qs, and a heat quantity generated by the refrigerant circuits 2a and 2b in the case of the parallel flow passage is denoted by Op. In Embodiment 1, the heat quantities Qs and Op are values when the refrigerant circuits 2a and 2b are operated in a fixed condition. However, the refrigeration cycle control unit 41 may calculate the heat quantities Qs and Op. A reciprocal E of the power efficiency of the heat medium delivery device 8 is expressed by E = (pressure loss AP/power consumption W). The pressure loss AP is a pressure loss, which is the pressure difference between the inlet and the outlet of the heat medium circuit 30. A reciprocal Es in the case of the series flow passage is expressed by Es = (pressure loss APs/power consumption Ws). A reciprocal Ep in the case of the parallel flow passage is expressed by Ep = (pressure loss APp/power consumption Wp).

[0037] The COPs is expressed by COPs = (Qs/Es) by use of these values. The COPp is expressed by COPp = (Qp/Ep). A value of COPs/COPp is used as a system improvement ratio U. The set value that is a reference of flow passage selection to the system improvement ratio U is denoted by Uref. The set value Uref is a value to determine that the operating efficiency in the series flow passage is higher than the operating efficiency in the parallel flow passage when the system improvement ratio U is larger than the set value Uref. The controller 40 stores values of the heat quantities Qs and Op, and the set value Uref.

[0038] Fig. 7 is a flowchart illustrating an example of the procedure of flow passage selection performed by the controller illustrated in Fig. 2. The efficiency calculation unit 42 causes the flow switching device 50 to set the series flow passage in the heat medium circuit 30 (Step ST101). The efficiency calculation unit 42 acquires information of power consumption Ws of the heat medium delivery device 8 from the refrigeration cycle control unit 41. The efficiency calculation unit 42 calculates a pressure difference between inlet pressure measured by the inlet pressure sensor 12 and outlet pressure measured by the outlet pressure sensor 13 (Step ST102). The calculated pressure difference is used as pressure loss APs. Then, the efficiency calculation unit 42 causes the flow switching device 50 to set the parallel flow passage in the heat medium circuit 30 (Step 5T103). The efficiency calculation unit 42 acquires information of power consumption Wp of the heat medium delivery device 8 from the refrigeration cycle control unit 41. Then, the efficiency calculation unit 42 calculates a pressure difference between inlet pressure and outlet pressure (Step 51104). The calculated pressure difference is used as pressure loss APp. [0039] The efficiency calculation unit 42 calculates the coefficient COPs of performance of the series flow passage by use of the power consumption Ws of the heat medium delivery device 8, the heat quantity Qs, and the pressure loss APs. Additionally, the efficiency calculation unit 42 calculates the coefficient COPp of performance of the parallel flow passage by use of the power consumption Wp of the heat medium delivery device 8, the heat quantity Op, and the pressure loss APp (Step 51105). Then, the efficiency calculation unit 42 calculates the system improvement ratio U by use of the COPs and the COPp, and notifies the flow passage determination unit 43 of the calculated system improvement ratio U. [0040] The flow passage determination unit 43 compares the system improvement ratio U received from the efficiency calculation unit 42 with the set value Uref (Step 51106). When the system improvement ratio U is larger than the set value Uref, the flow passage determination unit 43 selects the series flow passage as the flow passage to be formed in the heat medium circuit 30 (Step 51107). When the system improvement ratio U is less than or equal to the set value Uref in the determination of Step ST106, the flow passage determination unit 43 selects the parallel flow passage as the flow passage to be formed in the heat medium circuit 30 (Step ST108). Subsequently, the flow passage determination unit 43 causes the flow switching device 50 to form the flow passage selected in the determination of Step ST106 in the heat medium circuit 30.

[0041] The case in which the efficiency calculation unit 42 calculates the pressure difference in the case of the series flow passage before the pressure difference in the case of the parallel flow passage is described with reference to Fig. 7, either the above pressure difference calculation may be performed first. In the procedure illustrated in Fig. 7, power consumption Ws = power consumption Wp may be satisfied. In this case, in arithmetic processing of the system improvement ratio U, variables are only the pressure losses APs and APp, and the system improvement ratio U = COPs/COPp = (Qs/APs)/(Qp/APp) is satisfied. The efficiency calculation unit 42 can more smoothly calculate the system improvement ratio U. [0042] The case in which the pressure values measured by the inlet pressure sensor 12 and the outlet pressure sensor 13 are used is described as an example.

However, the flow passage determination unit 43 may switch the flow passages by use of the flow rate of the heat medium that flows through the heat medium circuit 30.

[0043] The efficiency calculation unit 42 calculates the pressure loss for each of the series flow passage and the parallel flow passage by use of a physical property values of the heat medium and the flow rate measured by the flowmeter 45. The pressure loss AP is calculated from the following Expression 1.

AP = A (V) x p^3/ 4 x p."1/4... (1) [0044] In Expression (1), AP [kPa] denotes a pressure loss generated when the heat medium passes through the heat medium heat exchangers 6a and 6b. A (V) denotes a coefficient intrinsic to the heat medium heat exchanger, and a value that depends on the flow velocity V. The flow velocity V in the case of the series flow passage and the flow velocity V in the case of the parallel flow passage are different. p [kg/m3] denotes the density of the heat medium, and u [mPa-s] denotes a viscosity coefficient of the heat medium. The controller 40 stores these physical property values.

[0045] In Step ST101 to ST104 illustrated in Fig. 7, the efficiency calculation unit 42 calculates the pressure losses APs and APp by use of the flow rate measured by the flowmeter 45, and Expression (1). Subsequently, as described with reference to Fig. 7, the efficiency calculation unit 42 calculates the system improvement ratio U (Step ST105). As described with reference to Fig. 7, the flow passage determination unit 43 compares the system improvement ratio U with the set value Uref (Step 5T106), and determines a flow passage to be formed in the heat medium circuit 30 in accordance with a comparison result (Step 5T107 or Step 5T108). In this case, power consumption Ws = power consumption Wp may also be satisfied.

[0046] Furthermore, the flow passage determination unit 43 may switch the flow passages by use of the kinematic viscosity of the heat medium. This flow passage switching is effective when the pressure of the heat medium at each of the inlet and the outlet of the heat medium circuit 30, and the flow rate of the heat medium that flows through the heat medium circuit 30 are unknown.

[0047] The power of the heat medium delivery device 8 largely depends on the kinematic viscosity of the heat medium. In most cases, when the viscosity of the heat medium is less than or equal to 10 [mPa-s], the viscosity hardly influences the power of the pump. However, when the viscosity of the heat medium is higher than or equal to 100 [mPa.s], the viscosity seriously influences the power of the pump. As a threshold value that is the selection reference of the flow passage regarding the viscosity, for example, 30 [mPa.s] is stored in the controller 40. In this case, when the viscosity of the heat medium to be used is higher than or equal to the threshold value, the flow passage determination unit 43 selects the parallel flow passage, and when the viscosity of the heat medium is less than the threshold value, the flow passage determination unit 43 selects the series flow passage. Additionally, the value of the viscosity of the heat medium to be used may be input to the controller 40 by an operator Consequently, the controller 40 compares the influence of the pressure loss on the operating efficiency, for each of the flow passages, and selects a flow passage having higher operating efficiency [0048] A case in which whether or not it is determined that the controller 40 causes the flow switching device 50 to switch the partial system flow passages when the series flow passage or the parallel flow passage is formed in the heat medium circuit 30 will be described below. The flow passage determination unit 43 determines whether or not any refrigerant circuit among the refrigerant circuits 2a and 2b stops the refrigeration cycle. When the refrigeration cycle of any one of the refrigerant circuits 2a and 2b is stopped, the flow passage determination unit 43 controls the flow switching device 50 in such a manner that the heat medium does not flow into the heat medium heat exchanger connected to the refrigerant circuit of the refrigeration cycle that stops.

[0049] Herein, as an example, a case in which the refrigeration cycle of the refrigerant circuit 2a is stopped will be described. The flow passage determination unit 43 causes the flow switching device 50 not to allow the heat medium to flow into the heat medium heat exchanger 6a connected to the refrigerant circuit 2a. More specifically, the flow passage determination unit 43 causes the flow switching device 50 to set the first valve 9 to the closed state, set the third valve 10 to the closed state, set the second valve 11 to the open state. Consequently, the partial system flow passage in which the heat medium flows through the heat medium heat exchanger 6b is formed in the heat medium circuit 30.

[0050] In some refrigeration cycle apparatus having a plurality of refrigerant circuits, when the heat load is reduced, operation of the compressor of at least one of the refrigerant circuits is stopped, but the heat medium continues flowing to the evaporator of the refrigerant circuit in which the compressor is stopped, and therefore an unnecessary pressure loss is generated. On the other hand, in Embodiment 1, as described above, the heat medium does not flow in the heat medium heat exchanger connected to the refrigerant circuit that does not operate, among a plurality of the refrigerant circuits. It is therefore possible to prevent increase of an unnecessary pressure loss, and improve efficiency of the operation of the apparatus. [0051] The case in which the refrigeration cycle control unit 41 stops the operation of the compressor 3a of the refrigerant circuit 2a connected to the heat medium heat exchanger 6a when the heat medium does not flow in the heat medium heat exchanger 6a is described. However, the operation frequency of the compressor 3a may be reduced instead of the stop of the compressor 3a. From the viewpoint of the reduction of power consumption, the compressor 3a is desirably stopped. However, the refrigeration cycle control unit 41 causes the compressor 3a to continue operation with reduction of ability. In this case, freezing of refrigerant in the refrigerant circuit 2a having the compressor 3a whose ability is reduced is suppressed, and temperature irregularity between the refrigerant circuits 2a and 2b, occurring when the ability of the compressor 3a is returned to the normal operation, is reduced.

[0052] In a case in which the series flow passage is formed, the refrigeration cycle control unit 41 may set the rotation frequency of the compressor 3b of the refrigerant circuit 2b connected to the heat medium heat exchanger 6b to a value higher than the rotation frequency of the compressor 3a of the refrigerant circuit 2a connected to the heat medium heat exchanger 6a. The refrigeration cycle control unit 41 may make the opening degree of the pressure reducing device 5b larger than the opening degree of the pressure reducing device 5a instead of increasing the rotation frequency of the compressor 3b. In this case, the flow rate of the refrigerant of the refrigerant circuit 2b that is provided to an upstream portion of the heat medium circuit 30, among the refrigerant circuits 2a and 2b, is increased, so that it is possible to improve efficiency of the operation of the refrigeration cycle apparatus 1.

[0053] In the case in which the series flow passage is formed, the refrigeration cycle control unit 41 may cause the heat medium delivery device 8 to reduce the flow rate of the heat medium compared to the case in which the parallel flow passage is formed. In this case, the flow velocity of the heat medium is reduced, the heat medium of each of the heat medium heat exchanger 6b and the heat medium heat exchanger 6a is sufficiently exchanged heat with the refrigerant in this order. As a result, a difference between the temperature of the heat medium that flows into the heat medium circuit 30, and the temperature of the heat medium that flows out of the heat medium circuit 30 is increased. This control is effective, for example, when the heat load is large such as when the refrigeration cycle apparatus 1 is being started and when the temperature difference of the heat medium need to be large.

[0054] The controller 40 may switch the flow passages in accordance with load.

When the heat load is large such as when the refrigeration cycle apparatus 1 is being started, a temperature difference between the temperature of the heat medium that flows into the heat medium circuit 30, and the temperature of the heat medium that flows out of the heat medium circuit 30 needs to be increased. To this end, when the heat load is large, the flow passage determination unit 43 selects the series flow passage. Subsequently, in the normal operation in which the refrigeration cycle apparatus 1 stably operates, the flow passage determination unit 43 selects the parallel flow passage or the partial system flow passage to reduce the power consumption of the heat medium delivery device 8. Thus, it is possible to improve the operating efficiency of the refrigeration cycle apparatus 1.

[0055] The first valve 9, the second valve 11, and the third valve 10 each may be a ball valve manually operated by an operator. The procedure illustrated in Fig. 7 may be performed by an operator to set the flow passage in the heat medium circuit 30.

In accordance with the viscosity of the heat medium, the operator may set the flow passage in the heat medium circuit 30. For example, when the heat medium is changed from brine having high viscosity to brine having low viscosity, the operator is only required to operate the flow switching device 50 to switch the parallel flow passage formed in the heat medium circuit 30 into the series flow passage. On the other hand, when the heat medium is changed from brine having low viscosity to brine having high viscosity, the operator may operate the flow switching device 50 to switch the series flow passage formed in the heat medium circuit 30 into the parallel flow passage.

[0056] Furthermore, the case in which the number of the refrigerant circuits provided in the refrigeration cycle apparatus 1 is two is described in Embodiment 1, but the number of the refrigerant circuits is not limited to two. The number of the refrigerant circuits provided in the refrigeration cycle apparatus 1 may be three or more. Also, in this case, a plurality of the heat medium heat exchangers are configured to be switched between series connection and parallel connection, so that it is possible to improve the efficiency of the operation of the refrigeration cycle apparatus 1. [0057] In the refrigeration cycle apparatus 1 of Embodiment 1, the flow switching device 50 switches between the series flow passage in which the plurality of heat medium heat exchangers 6a and 6b are connected in series, and the parallel flow passage in which the plurality of heat medium heat exchangers 6a and 6b are connected in parallel, in the heat medium circuit 30.

[0058] According to Embodiment 1, it is possible to form a flow passage having higher operating efficiency, among the series flow passage and the parallel flow passage.

As a result, it is possible to improve operating efficiency as the whole apparatus. [0059] The viscosity of brine used in a brine cooler is about 4.0 to 100.0 [mPa.s], and markedly varies compared to water (0.8 [mPa-s]). The flow rate and the viscosity of the brine used are different depending on environment in which the brine is used.

For example, in a region in which prevention of freezing of a heat medium in winter is needed, the brine having high viscosity is used as the heat medium. In this case, a pressure loss due to series connection of a plurality of the evaporators markedly influences the operating efficiency, and therefore a configuration in which a plurality of the evaporators are connected in parallel is suitable.

[0060] On the other hand, in a case in which the brine having low viscosity is used as the heat medium, the pressure loss due to series connection of a plurality of the evaporators sometimes less influences the operating efficiency Even in such a case, some refrigeration cycle apparatus in which the brine is used as the heat medium, in consideration of the degree of variation of the viscosity, a configuration in which a plurality of the evaporators are connected in parallel is employed. On the other hand, in Embodiment 1, the flow passage determination unit 43 determines a flow passage having higher operating efficiency in accordance with the viscosity of the heat medium.

The operating efficiency of the refrigeration cycle apparatus 1 is therefore improved.

[0061] The viscosity of the brine used is sometimes changed from the brine having high viscosity to the brine having low viscosity. In this case, in a configuration in which a plurality of the evaporators are connected in parallel, the refrigeration cycle apparatus is operated in a state in which the refrigerating efficiency is reduced. The refrigeration cycle apparatus 1 of Embodiment 1 switches between the series flow passage and the parallel flow passage. Even after installation of the refrigeration cycle apparatus 1, one of the series flow passage and the parallel flow passage is formed in the heat medium circuit 30 in accordance with the viscosity of the heat medium. As a result, it is possible to optimize a connection configuration of the plurality of evaporators.

[0062] Embodiment 2 Fig. 8 is a diagram illustrating a configuration example of a refrigeration cycle apparatus of Embodiment 2 of the present invention. In Embodiment 2, the same components as those of Embodiment 1 are denoted by the same reference signs, and the detailed description will be omitted. As illustrated in Fig. 8, in a refrigeration cycle apparatus la of Embodiment 2, compared to the configuration illustrated in Fig. 1, a flow regulator 20 is provided at a position of the third valve 10.

[0063] The flow regulator 20 regulates a flow rate of a heat medium that flows in a pipe 35. The flow regulator 20 has a motor-operated valve capable of regulating an opening degree, and a reduced-diameter part that cannot regulate an opening degree. A connection flow passage in which the flow regulator 20 is provided has larger flow passage resistance than a flow passage in which the heat medium heat exchanger 6a is provided, and a flow passage in which the heat medium heat exchanger 6b is provided. When the series flow passage is formed in the heat medium circuit 30, the flow velocity of the heat medium is therefore reduced.

[0064] In the heat medium circuit 30, the flow velocity of the heat medium is reduced, so that heat exchange between refrigerant and the heat medium is more reliably performed, and therefore it is possible to increase the range of temperature change of the heat medium. The flow passage resistance of the connection flow passage in which the flow regulator 20 is provided is large, and therefore even when the parallel flow passage is formed, it is difficult for the heat medium to flow in the connection flow passage. It is difficult for the heat medium to flow because of the reduced-diameter part of the flow regulator 20, or the pipe 35.

[0065] In a case in which the parallel flow passage is formed, a portion of the heat medium flows in the connection flow passage in which the flow regulator 20 is provided. In such a configuration, in the connection flow passage, freezing of the heat medium is suppressed. Furthermore, when the parallel flow passage is formed, a portion of the heat medium flows in the connection flow passage in which the flow regulator 20 is provided, and therefore, for example, when the flow switching device 50 switches the parallel flow passage to the series flow passage, it is possible to reduce occurrence of temperature irregularity in the heat medium that flows out of the heat medium circuit 30.

[0066] A case in which the third valve 10 is provided in the pipe 35 is described in Embodiment 1, and a case in which the flow regulator 20 is provided in the pipe 35 is described in Embodiment 2. However, a valve and a flow regulator may not be provided in the pipe 35. When any valve and any flow regulator are not be provided in the pipe 35, it is possible to reduce cost of the apparatus.

[0067] For example, in Fig. 8, when the flow regulator 20 is not provided in the pipe 35, the heat medium that flows through the pipe 34 largely changes the flow direction, and enters the pipe 35, and the heat medium flows through the pipe 33 in such a manner that the flow direction is parallel to the heat medium heat exchanger 6b again. In a case in which the series flow passage is formed, even when the flow regulator 20 is not provided in the pipe 35, the heat medium passes through the pipe 35, so that the flow velocity of the heat medium as the whole of the heat medium circuit 30 is reduced. In the heat medium circuit 30, the flow velocity of the heat medium is reduced, so that heat exchange between the refrigerant and the heat medium is more reliably performed. In a case of the parallel flow passage, even when the heat medium flows in the pipe 35, the flow velocity of the heat medium is low, and therefore the flow rate of the heat medium that flows in the pipe 35 is reduced, and influence on heat exchange efficiency is reduced.

Reference Signs List [0068] 1, la refrigeration cycle apparatus 2a, 2b refrigerant circuit3a, 3b compressor 4a, 4b heat source side heat exchanger 5a, 5b pressure reducing device 6a, 6b heat medium heat exchanger 7a, 7b fan 8 heat medium delivery device 9 first valve 10 third valve 11 second valve 12 inlet pressure sensor 13 outlet pressure sensor 20 flow regulator 30 heat medium circuit 31 to 35 pipe 40 controller 41 refrigeration cycle control unit 42 efficiency calculation unit 43 flow passage determination unit 45 flowmeter 50 flow switching device 60 load side unit