WO2024100832A1

WO2024100832A1 - Heat source system

Info

Publication number: WO2024100832A1
Application number: PCT/JP2022/041865
Authority: WO
Inventors: 智典小島; 大亮松▲崎▼; 圭岡本; 洋貴佐藤; 寛也石原
Original assignee: 三菱電機株式会社
Priority date: 2022-11-10
Filing date: 2022-11-10
Publication date: 2024-05-16

Abstract

This heat source system has: a first heat medium heat exchanger and a second heat medium heat exchanger that are connected in parallel to a load; a first heat source machine and a second heat source machine; a first pump that causes a heat medium to circulate through a heat medium circuit that includes the first heat medium heat exchanger; a second pump that causes the heat medium to circulate through a heat medium circuit that includes the second heat medium heat exchanger; and a controller. The controller has: a machine internal resistance calculation means that derives the respective machine internal resistances of the first heat medium heat exchanger and the second heat medium heat exchanger; a machine external resistance calculation means that calculates a first machine external resistance using the machine internal resistance of the first heat medium heat exchanger and calculates a second machine external resistance using the machine internal resistance of the second heat medium heat exchanger; and a pump control means that controls an operating frequency F2 of the second pump so that the second machine external resistance approaches the first machine external resistance.

Description

Heat Source System

This disclosure relates to a heat source system having a heat medium circuit.

As an example of a conventional heat source system, Patent Document 1 discloses a heat source system in which multiple heat source units are connected in parallel to a heat medium circuit.

In a conventional heat source system, each of the multiple heat source machines is connected to a supply water header pipe and a return water header pipe via water piping. Each of the multiple heat source machines is provided with a refrigeration cycle circuit in which a refrigerant circulates. The refrigeration cycle circuit is provided with a load side heat exchanger that exchanges heat between the refrigerant and water flowing through the water piping. A flow rate adjustment pump is provided on the water piping connected to each of the multiple heat source machines. Each of the multiple flow rate adjustment pumps circulates water from the return water header pipe to the load side heat exchanger via the water piping, and then sends it to the supply water header pipe. The water that has exchanged heat with the refrigerant in each of the multiple load side heat exchangers circulates through the load device via the supply water header pipe, and then returns to the return water header pipe.

Currently, HFC refrigerants such as R410A or R404A are the mainstream refrigerants used in refrigeration cycle circuits. However, due to growing environmental awareness, there is a trend toward refrigerants with lower Global Warming Potential (GWP) values. In order to replace currently used refrigerants with refrigerants with lower GWP, development is underway for refrigerant equipment used in refrigeration cycle circuits that improves thermal efficiency in accordance with the refrigerants to be replaced.

International Publication No. 2017/068631

The load side heat exchanger installed in the heat source unit of a conventional heat source system may have different piping specifications for the old model corresponding to the refrigerant currently in use and the new model corresponding to the refrigerant to be replaced. For example, the head loss of the load side heat exchanger of the old model may differ from the head loss of the load side heat exchanger of the new model. Also, depending on the convenience of the owner of the heat source system, it may be difficult to change all of the multiple heat source units to heat source units having new model load side heat exchangers at once. In this case, a single heat source system will have a mixture of old model load side heat exchangers and new model load side heat exchangers.

In the heat source system disclosed in Patent Document 1, if an older model load side heat exchanger and a new model load side heat exchanger are mixed, a flow rate difference will occur between the water flowing through the older model load side heat exchanger and the water flowing through the new model load side heat exchanger. If the flow rate difference between multiple parallel water circuits is large, there is a problem in that the stability of the temperature of the water supplied to the load device decreases.

The present disclosure has been made to solve the problems described above, and provides a heat source system that can stabilize the temperature of the fluid supplied to the load even if multiple heat medium heat exchangers connected in parallel have different head losses.

The heat source system according to the present disclosure includes a first heat medium heat exchanger connected in series to a load and exchanging heat between a refrigerant and a heat medium, a second heat medium heat exchanger connected in parallel to the first heat medium heat exchanger to the load and exchanging heat between the refrigerant and the heat medium, a first heat source unit connected to the first heat medium heat exchanger and including a refrigerant circuit through which the refrigerant circulates, a second heat source unit connected to the second heat medium heat exchanger and including a refrigerant circuit through which the refrigerant circulates, a first pump connected in series to the first heat medium heat exchanger and circulating the heat medium in a heat medium circuit including the first heat medium heat exchanger and the load, and a second pump connected in series to the second heat medium heat exchanger and including the second heat medium heat exchanger and the The system includes a second pump that circulates the heat medium in a heat medium circuit including a load, and a controller that controls the operating frequencies of the first pump and the second pump. The controller includes an internal resistance calculation means that calculates an internal resistance, which is a head loss of each of the first heat medium heat exchanger and the second heat medium heat exchanger, an external resistance calculation means that calculates a first external resistance using the internal resistance of the first heat medium heat exchanger and calculates a second external resistance using the internal resistance of the second heat medium heat exchanger, and a pump control means that controls the operating frequency of the second pump so that the second external resistance approaches the first external resistance based on the operating frequency of the first pump.

According to the present disclosure, the internal resistance of each of the first heat medium heat exchanger and the second heat medium heat exchanger is calculated for the heat medium circulating through the heat medium circuit, and the external resistance of each heat medium heat exchanger is calculated based on the internal resistance of each heat medium heat exchanger. Then, based on the difference in the external resistance of each heat medium heat exchanger, the operating frequency of the second pump is set so as to reduce the flow rate difference between these heat medium heat exchangers. Since the flow rate difference between the heat medium circulating through the first heat medium heat exchanger and the heat medium circulating through the second heat medium heat exchanger is reduced, the temperature difference between the heat medium circulating through the first heat medium heat exchanger and the heat medium circulating through the second heat medium heat exchanger is suppressed. As a result, the temperature stability of the heat medium supplied to the load side device via the heat medium circuit is improved.

1 is a block diagram showing a configuration example of a heat source system according to a first embodiment. FIG. 2 is a functional block diagram showing a configuration example of a controller of the heat source system according to the first embodiment. 1 is a graph showing the relationship between flow rate and head loss for a number of types of heat transfer media. 2 is a graph showing an example of a total head of the first pump shown in FIG. 1 . 1 is a graph showing an example of external resistance of an old model and a new model. 3 is a hardware configuration diagram showing an example of the configuration of a controller shown in FIG. 2 . 3 is a hardware configuration diagram showing another example of the configuration of the controller shown in FIG. 2. 4 is a flowchart showing an operation procedure of the heat source system according to the first embodiment. 9 is a flowchart showing the operation procedure of steps S14 and S15 shown in FIG. 8 . 1 is a graph showing an example of external resistance of an old model and a new model when the heat medium is water. 1 is a graph showing an example of external resistance of an old model and a new model when the heat medium is brine. FIG. 11 is a block diagram showing a configuration example of a heat source system according to a first modified example. FIG. 11 is a functional block diagram showing a configuration example of a controller of a heat source system according to a second embodiment. 14 is a diagram showing an example of a first table stored in the storage unit shown in FIG. 13 . FIG. 14 is a diagram showing an example of a second table stored in the storage unit shown in FIG. 13 . FIG. 10 is a flowchart showing the operation of step S14 shown in FIG. 8 in the second embodiment.

Embodiment 1.
The configuration of the heat source system according to the first embodiment will be described. Fig. 1 is a block diagram showing a configuration example of the heat source system according to the first embodiment. First, the overall configuration of the heat source system 1 will be described with reference to Fig. 1. The heat source system 1 has a first heat source unit 3a and a second heat source unit 3b, a first heat medium heat exchanger 2a and a second heat medium heat exchanger 2b, a first pump 4a and a second pump 4b, and a controller 5.

The first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b are heat exchangers that exchange heat between a refrigerant and a heat medium. The first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b are, for example, plate-type or double-tube-type heat exchangers. In the first embodiment, the heat exchange efficiency of the second heat medium heat exchanger 2b is greater than that of the first heat medium heat exchanger 2a, and the head loss of the second heat medium heat exchanger 2b is less than that of the first heat medium heat exchanger 2a. For example, the heat transfer area of the second heat medium heat exchanger 2b is greater than that of the first heat medium heat exchanger 2a. Hereinafter, the first heat medium heat exchanger 2a is referred to as an old model heat medium heat exchanger, and the second heat medium heat exchanger 2b is referred to as a new model heat medium heat exchanger.

In addition, in the present embodiment 1, the first heat source unit 3a and the second heat source unit 3b have the same cold heat generation capacity, but the cold heat generation capacity of the first heat source unit 3a and the heat generation capacity of the second heat source unit 3b may be different. The capacity of the first pump 4a and the capacity of the second pump 4b are equal. The first pump 4a and the second pump 4b are connected to the controller 5 via a signal line (not shown).

As shown in FIG. 1, the load device 43 that uses the cold generated by the heat source system 1 is connected to the heat medium piping 53. One end of the heat medium piping 53 is connected to the return fluid header pipe 42, and the other end of the heat medium piping 53 is connected to the forward fluid header pipe 41. The heat medium piping 51 is connected to the forward fluid header pipe 41. The heat medium piping 52 is connected to the return fluid header pipe 42. The forward fluid header pipe 41 and the return fluid header pipe 42 are connected by a bypass piping 54.

The heat medium pipe 52 branches into heat medium pipe 7a and heat medium pipe 7b at branch point 44. Heat medium pipe 7a and heat medium pipe 7b join at junction 45 and are connected to heat medium pipe 51. A first pump 4a and a first heat medium heat exchanger 2a are connected in series to the heat medium pipe 7a. A second pump 4b and a second heat medium heat exchanger 2b are connected in series to the heat medium pipe 7b.

The first pump 4a, the first heat medium heat exchanger 2a, and the load device 43 are connected by

heat medium pipes

7a, 51, 52, and 53 to form a heat medium circuit 6 in which the heat medium circulates. The first pump 4a is built into the heat medium circuit 6 including the first heat medium heat exchanger 2a. The second pump 4b, the second heat medium heat exchanger 2b, and the load device 43 are connected by

heat medium pipes

7b, 51, 52, and 53 to form a heat medium circuit 6 in which the heat medium circulates. The second pump 4b is built into the heat medium circuit 6 including the second heat medium heat exchanger 2b. The heat medium is, for example, water or brine. Brine is a liquid containing a freezing point depressant such as ethylene glycol or propylene glycol.

The first pump 4a and the first heat medium heat exchanger 2a, and the second pump 4b and the second heat medium heat exchanger 2b are connected in parallel in the heat medium circuit 6. In FIG. 1, the flow direction of the heat medium circulating in the heat medium circuit 6 is indicated by dashed arrows. The heat source system 1 is a system in which old model heat medium heat exchangers and new model heat medium heat exchangers are mixed in the heat medium circuit 6.

In the heat medium pipe 7a, a first outlet temperature sensor 8a is provided at the outlet of the first heat medium heat exchanger 2a to detect the outlet temperature Tb, which is the temperature of the heat medium flowing out from the first heat medium heat exchanger 2a. In the heat medium pipe 7b, a second outlet temperature sensor 8b is provided at the outlet of the second heat medium heat exchanger 2b to detect the outlet temperature Tb, which is the temperature of the heat medium flowing out from the second heat medium heat exchanger 2b. The first outlet temperature sensor 8a and the second outlet temperature sensor 8b are connected to the controller 5 via a signal line (not shown).

Next, the configuration of the first heat source unit 3a and the second heat source unit 3b will be described. The first heat source unit 3a has a compressor 11a, a heat source side heat exchanger 12a, an expansion valve 13a, and a fan 14a. The compressor 11a, the heat source side heat exchanger 12a, the expansion valve 13a, and the first heat medium heat exchanger 2a are connected by a refrigerant pipe 15a to form a refrigerant circuit 10a. The compressor 11a, the expansion valve 13a, and the fan 14a are connected to the controller 5 via a signal line (not shown). In FIG. 1, the flow direction of the refrigerant circulating through the refrigerant circuit 10a is indicated by a dashed arrow.

The second heat source unit 3b has a compressor 11b, a heat source side heat exchanger 12b, an expansion valve 13b, and a fan 14b. The compressor 11b, the heat source side heat exchanger 12b, the expansion valve 13b, and the second heat medium heat exchanger 2b are connected by a refrigerant pipe 15b to form a refrigerant circuit 10b. The compressor 11b, the expansion valve 13b, and the fan 14b are connected to the controller 5 via a signal line (not shown). In FIG. 1, the flow direction of the refrigerant circulating through the refrigerant circuit 10b is indicated by a dashed arrow.

Next, the configuration of the first heat source unit 3a will be described. The compressor 11a draws in low-temperature and low-pressure refrigerant, compresses the drawn refrigerant, and discharges it. The compressor 11a is an inverter compressor whose capacity can be adjusted by changing the operating frequency. The heat source side heat exchanger 12a is a heat exchanger that exchanges heat between air and refrigerant. The heat source side heat exchanger 12a functions as a condenser in the refrigerant circuit 10a. The heat source side heat exchanger 12a is, for example, a fin-and-tube type heat exchanger having a heat transfer tube and multiple heat dissipation fins. The expansion valve 13a reduces the pressure of the liquid refrigerant flowing in from the heat source side heat exchanger 12a and expands it. The expansion valve 13a is, for example, an electronic expansion valve. The fan 14a draws in air and supplies the drawn air to the heat source side heat exchanger 12a. The fan 14a is, for example, a propeller fan. The second heat source unit 3b has a similar configuration to the first heat source unit 3a, so a detailed description of it will be omitted.

Next, the configuration of the controller 5 will be described. FIG. 2 is a functional block diagram showing an example of the configuration of the controller of the heat source system according to the first embodiment. The controller 5 is, for example, a microcomputer. The controller 5 has a refrigeration cycle control means 21, a storage means 22, and a heat medium circuit control means 30. The heat medium circuit control means 30 has an internal resistance calculation means 31, an external resistance calculation means 32, and a pump control means 33.

An input means 20 is connected to the controller 5 for inputting values of physical properties such as the density and kinetic viscosity of the heat medium. The input means 20 is, for example, a remote controller (not shown) that is connected for communication with the controller 5, or an information processing terminal (not shown) such as a smartphone that is carried and operated by the worker who installs the heat source system 1.

In the functional block diagram shown in FIG. 2, the information acquired or generated by the refrigeration cycle control means 21 may be stored in the storage means 22. In this case, the heat medium circuit control means 30 may read out the information acquired or generated by the refrigeration cycle control means 21 from the storage means 22. Also, FIG. 2 shows a schematic diagram in which the storage means 22 provides the stored information to the internal resistance calculation means 31 among the means of the heat medium circuit control means 30, but the information may be provided to the external resistance calculation means 32 and the pump control means 33 via the internal resistance calculation means 31.

In addition, in the first embodiment, the input means 20 is connected to the controller 5 so that the operator can input the physical property values of the heat medium, but the input means 20 does not have to be used. For example, if a control board (not shown) mounted on the first heat source unit 3a or the second heat source unit 3b is provided with a switch (DIP switch, rotary switch, etc.) for inputting the physical property values of the heat medium, the operator may input the physical property values of the heat medium to the controller 5 by switching the switch on the control board. Note that the method of inputting the physical property values of the heat medium used in the heat medium circuit 6 to the controller 5 is not limited to the method using the input means 20 and the method by switching a switch provided on the control board (not shown).

The refrigeration cycle control means 21 controls the operating frequency of the

compressors

11a and 11b, the opening of the

expansion valves

13a and 13b, and the rotation frequency of the

fans

14a and 14b so that the outflow temperature Tb received from each of the first outflow temperature sensor 8a and the second outflow temperature sensor 8b falls within a predetermined range based on the set temperature of the load device 43.

The storage means 22 stores information related to head loss for each of the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b when the heat medium is water. The information related to head loss is information on the pipe specifications of the heat medium heat exchangers. The information on the pipe specifications is information such as the length and diameter of the piping in the heat medium heat exchanger.

The storage means 22 also stores a calculation formula for determining the head loss of the heat medium from the kinetic viscosity and specific gravity of the heat medium. The calculation formula is, for example, the Darcy-Weisbach formula or the Brasilius formula. The head loss in the case of water may be calculated using an approximation formula created in advance based on test values. The storage means 22 stores information on the total head of the first pump 4a and the second pump 4b. In the first embodiment, the first pump 4a and the second pump 4b have the same performance, so it is sufficient for the storage means 22 to store information on the total head of either one of the pumps. Usually, the total head of a pump is described in the pump specifications.

When the values of density and kinetic viscosity of the heat medium are input via the input means 20, the internal resistance calculation means 31 uses the density and kinetic viscosity and the information on the pipe specifications stored in the memory means 22 to calculate the internal resistance, which is the head loss of each of the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b, as follows.

The internal resistance calculation means 31 calculates the head loss of the heat medium using the kinetic viscosity of the heat medium, the specific gravity of the heat medium relative to water, and equations (1) to (4). Equation (1) is the Darcy-Weisbach equation. Referring to equation (1), it can be seen that the head loss changes depending on the physical properties of the heat medium.

ΔP on the left side of equation (1) is the pressure loss [kPa], which corresponds to the head loss. In equation (1), L is the length of the piping in the heat medium heat exchanger [m], and D is the diameter of the piping [m]. ρ is the density of the heat medium [kg/l], and u is the flow velocity of the heat medium [m/s]. During turbulent flow (3x10^2<Re<1x10^5), f in equation (1) is calculated using the Brasilius equation shown in equation (2).

Re in formula (2) is calculated by formula (3). In formula (3), u is the flow velocity [m/s], L is the length of the pipe [m], and ν is the kinetic viscosity of the heat medium [m ² /s].

When the flow velocities of the brine and water are equal, the head loss ratio α is expressed by equation (4). In the parameters shown in equation (4), the subscript B means brine, and w means water. α serves as a correction coefficient for calculating the head loss according to the type of heat transfer medium for the head loss shown in equation (1).

Then, the internal resistance calculation means 31 calculates the internal resistance, which is the head loss of each heat medium heat exchanger of the new model and the old model, corresponding to the type of heat medium by multiplying the head loss ratio α calculated using equation (4) by the head loss calculated using equation (1). When the heat medium is water, α = 1.

FIG. 3 is a graph showing the relationship between the flow rate and the head loss for a plurality of types of heat transfer media. The vertical axis of FIG. 3 is the head loss [kPa], and the horizontal axis is the flow rate [m ³ /h] of the heat transfer media circuit. Wg shows the case of water with a kinetic viscosity of 1.79 [mm ² /s] and a specific gravity of 1.00. Bg1 shows the case of brine with a kinetic viscosity of 35.6 [mm ² /s] and a specific gravity of 1.06. Bg2 shows the case of brine (55 wt%) with a kinetic viscosity of 13.7 [mm ² /s] and a specific gravity of 1.08. Bg3 shows the case of brine (40 wt%) with a kinetic viscosity of 5.56 [mm ² /s] and a specific gravity of 1.05. From FIG. 3, it can be seen that the head loss differs even at the same flow rate depending on the physical properties of the heat transfer media. The storage means 22 stores information on the graph of Wg shown in FIG. 3 for each of the old and new model heat medium heat exchangers.

The external resistance calculation means 32 reads information on the total head of the first pump 4a or the second pump 4b from the storage means 22. In this embodiment 1, the capacity of the first pump 4a and the second pump 4b is the same, so the case of the first pump 4a will be described. Figure 4 is a graph showing an example of the total head of the first pump shown in Figure 1.

The total head shown in Fig. 4 is for a pump capacity of 5.5 [kW] and a pump operation frequency F1 of 50 [Hz]. The total head when the frequency changes is calculated from the following formula. For example, if the total head is 34 [m] when the pump operation frequency F1 is 50 [Hz] and the flow rate is 0 [m ³ /h], the external resistance calculation means 32 calculates the total head when the pump operation frequency F1 is 40 [Hz] and the flow rate is 0 [m ³ /h] as 34 [m] x (40 [Hz] / 50 [Hz]) ^ 2 = 21.7 [m]. The vertical axis of Fig. 4 is the total head [m], and the horizontal axis is the flow rate [m ³ /h] of the heat medium circuit.

Then, the external resistance calculation means 32 converts the unit of the total head from [m] to [kPa]. Specifically, the external resistance calculation means 32 performs the conversion using the formula (total head [m] × gravitational acceleration [m/s ² ] × brine specific gravity). The brine specific gravity is the specific gravity of the brine relative to water. When the heat medium is water, this value is 1.0. The external resistance calculation means 32 calculates the difference between the calculated total head and the internal resistance calculated by the internal resistance calculation means 31 for each of the new model and the old model, thereby calculating the external resistance [kPa], which is the external head. In other words, the external resistance calculation means 32 calculates the external resistance for each heat medium heat exchanger of the new model and the old model using the formula (external resistance = total head - internal resistance).

Fig. 5 is a graph showing an example of the external resistance of each of the old model and the new model. The vertical axis of Fig. 5 is the external resistance [kPa], and the horizontal axis is the flow rate [ ^m3 /h] of the heat medium circuit. The solid line shows the external resistance of the heat medium heat exchanger of the new model. The dashed line shows the external resistance of the heat medium heat exchanger of the old model. It can be seen from Fig. 5 that the external resistance of the new model is different from that of the old model.

The pump control means 33 uses the operating frequency F1 of the first pump 4a as a reference to determine the operating frequency F2 of the second pump 4b at which the external resistance of the new model approaches that of the old model. The pump control means 33 controls the second pump 4b to operate at the determined operating frequency F2. The total head of the pump changes depending on the operating frequency of the pump. Since the external resistance calculated by changing the total head also changes with the total head, the pump control means 33 executes control to change the operating frequency F2 of the second pump 4b so that the external resistance of the new model approaches that of the old model when the operating frequency F1 of the first pump 4a changes. For example, in the case of the graph shown in FIG. 5, the pump control means 33 controls to reduce the operating frequency F2 of the second pump 4b so that the solid line indicating the external resistance of the new model overlaps with the dashed line indicating the external resistance of the old model, relative to the flow rate at the current operating frequency F1 of the first pump 4a.

Here, an example of the hardware of the controller 5 shown in FIG. 2 will be described. FIG. 6 is a hardware configuration diagram showing an example of the configuration of the controller shown in FIG. 2. When the various functions of the controller 5 are executed by hardware, the controller 5 shown in FIG. 2 is configured with a processing circuit 90 as shown in FIG. 6. Each function of the refrigeration cycle control means 21, memory means 22, internal resistance calculation means 31, external resistance calculation means 32, and pump control means 33 shown in FIG. 2 is realized by the processing circuit 90.

When each function is executed by hardware, the processing circuit 90 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these. Each of the functions of the refrigeration cycle control means 21, the storage means 22, the internal resistance calculation means 31, the external resistance calculation means 32, and the pump control means 33 may be realized by a separate processing circuit 90. Also, the functions of the refrigeration cycle control means 21, the storage means 22, the internal resistance calculation means 31, the external resistance calculation means 32, and the pump control means 33 may be realized by a single processing circuit 90.

Furthermore, another example of hardware of the controller 5 shown in FIG. 2 will be described. FIG. 7 is a hardware configuration diagram showing another example of the configuration of the controller shown in FIG. 2. When the various functions of the controller 5 are executed by software, the controller 5 shown in FIG. 2 is composed of a processor 91 such as a CPU (Central Processing Unit) and a memory 92, as shown in FIG. 7. The functions of the refrigeration cycle control means 21, the storage means 22, the internal resistance calculation means 31, the external resistance calculation means 32, and the pump control means 33 are realized by the processor 91 and the memory 92. FIG. 7 shows that the processor 91 and the memory 92 are connected to each other so as to be able to communicate with each other via a bus 93.

When each function is executed by software, the functions of the refrigeration cycle control means 21, memory means 22, internal resistance calculation means 31, external resistance calculation means 32 and pump control means 33 are realized by software, firmware or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 92. The processor 91 realizes the functions of each means by reading and executing the programs stored in the memory 92.

For example, non-volatile semiconductor memory such as ROM (Read Only Memory), flash memory, EPROM (Erasable and Programmable ROM), and EEPROM (Electrically Erasable and Programmable ROM) may be used as the memory 92. Volatile semiconductor memory such as RAM (Random Access Memory) may also be used as the memory 92. Furthermore, removable recording media such as magnetic disks, flexible disks, optical disks, CDs (Compact Discs), MDs (Mini Discs), and DVDs (Digital Versatile Discs) may also be used as the memory 92.

In the first embodiment, the first pump 4a and the second pump 4b have the same performance, but the performance may be different. In this case, the storage means 22 stores information on the total head of each of the first pump 4a and the second pump 4b.

Next, the operation of the heat source system 1 of the present embodiment 1 will be described. FIG. 8 is a flowchart showing the operation procedure of the heat source system according to the embodiment 1. FIG. 9 is a flowchart showing the operation procedure of steps S14 and S15 shown in FIG. 8.

Here, the input means 20 will be described as an information processing terminal (not shown) carried by the worker who installs the heat source system 1. The information processing terminal (not shown) is, for example, a tablet such as a PDA (Personal Digital Assistant) equipped with a display.

The operator connects an information processing terminal (not shown) to the controller 5 via a cable. When the controller 5 and the information processing terminal (not shown) are connected so as to be able to communicate with each other, in step S11 shown in FIG. 8, the heat medium circuit control means 30 causes the information processing terminal (not shown) to display a message asking the operator whether the pump is built-in or not. When a response is input via the information processing terminal (not shown) indicating that the pump is not built-in (No in step S11), the heat medium circuit control means 30 ends the process.

If a response is input in the determination process of step S11 that the pump is built-in (Yes in step S11), the heat medium circuit control means 30 displays a message on the information processing terminal (not shown) asking the operator whether the heat medium heat exchangers are a mixture of new and old models (step S12). If a response is input via the information processing terminal (not shown) that the heat medium heat exchangers are not a mixture of new and old models (No in step S12), the heat medium circuit control means 30 ends the process.

In the judgment process of step S12, when a response is input via the information processing terminal (not shown) that a new model heat medium heat exchanger and an old model heat medium heat exchanger are mixed (if Yes in step S12), the heat medium circuit control means 30 judges whether or not the physical properties of the brine have been input (step S13). The method of inputting the physical property values of the heat medium used in the heat medium circuit 6 to the controller 5 is not limited to the method using the input means 20. For example, if a switch (DIP switch, rotary switch, etc.) for inputting the physical property values of the heat medium is provided on the control board (not shown) mounted on the first heat source unit 3a or the second heat source unit 3b, the operator may switch the switch on the control board to input the physical property values of the heat medium to the controller 5. Furthermore, the method of inputting the physical property values of the heat medium used in the heat medium circuit 6 to the controller 5 is not limited to the method using the input means 20 and the method by switching the switch provided on the control board (not shown).

In the judgment process of step S13, if the physical properties of the brine are input via an information processing terminal (not shown) (if Yes in step S13), the heat medium circuit control means 30 controls the operating frequency F2 of the second pump 4b in response to the physical properties of the brine so that the flow rate of the new model approaches the flow rate of the old model (step S14). On the other hand, in the judgment process of step S13, if the physical properties of the brine are not input via the information processing terminal (not shown) (if No in step S13), the heat medium circuit control means 30 controls the operating frequency F2 of the second pump 4b in response to the physical properties of water so that the flow rate of the new model approaches the flow rate of the old model (step S15).

The operations of steps S14 and S15 shown in FIG. 8 will be described in detail with reference to FIG. 9. Here, the process of step S14 will be specifically described in the case where the heat medium is brine.

When the values of the density and kinetic viscosity of the heat medium are input, the internal resistance calculation means 31 calculates the internal resistance of each of the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b based on the density and kinetic viscosity of the heat medium and the information on the pipe specifications (step S101). Specifically, the internal resistance calculation means 31 calculates the internal resistance of each of the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b using the values of the density and kinetic viscosity of the heat medium, the information on the pipe specifications of each of the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b, and formulas (1) to (4).

Next, the external resistance calculation means 32 calculates the external resistance of the first heat medium heat exchanger 2a and the external resistance of the second heat medium heat exchanger 2b from the internal resistance calculated in step S101 and the total head of the pump (step S102). Specifically, the external resistance calculation means 32 calculates the first external resistance, which is the external resistance of the first heat medium heat exchanger 2a, by subtracting the internal resistance of the first heat medium heat exchanger 2a from the total head of the pump. In addition, the external resistance calculation means 32 calculates the second external resistance, which is the external resistance of the second heat medium heat exchanger 2b, by subtracting the internal resistance of the second heat medium heat exchanger 2b from the total head of the pump.

The pump control means 33 determines the operating frequency F2 of the second pump 4b at which the second external resistance approaches the first external resistance, based on the operating frequency F1 of the first pump 4a (step S103). Then, the pump control means 33 controls the second pump 4b to operate at the operating frequency F2 determined in step S103 (step S104).

In the case of step S15, the internal resistance calculation means 31 does not need to calculate equation (4) in the process of step S101. Also, when the heat medium is water, information on the physical properties does not need to be input. This is because the storage means 22 stores information on head loss based on the case where the heat medium is water.

FIG. 10 is a graph showing an example of the external resistance of the old model and the new model when the heat medium is water. FIG. 11 is a graph showing an example of the external resistance of the old model and the new model when the heat medium is brine. The brine shown in this graph is a brine with a concentration of a freezing point depressant such as ethylene glycol or propylene glycol of 70 wt %. The vertical axis of FIG. 10 and FIG. 11 is the external resistance [kPa], and the horizontal axis is the flow rate [m ³ /h] of the heat medium circuit. In FIG. 10 and FIG. 11, the solid line shows the external resistance of the heat medium heat exchanger of the new model. The dashed line shows the external resistance of the heat medium heat exchanger of the old model. FIG. 10 and FIG. 11 show the case where the pump capacity is 2.2 kW, 3.7 kW, and 5.5 kW, and the operating frequency of each of the first pump 4a and the second pump 4b is 50 Hz.

10, for example, for a pump capacity of 5.5 kW, when the external resistance is 0, the flow rate is 42.5 [ ^m3 /h] in the old model, whereas the flow rate is 45.0 [ ^m3 /h] in the new model. By reducing the operating frequency F2 of the second pump 4b from 50 Hz to approximately 48 Hz, it is possible to eliminate any difference in flow rate between the new model and the old model.

For example, in Fig. 11, for a pump capacity of 5.5 kW, when the external resistance is 0, the flow rate is 38.0 [ ^m3 /h] in the old model, whereas the flow rate is 41.5 [ ^m3 /h] in the new model. In the case of brine shown in Fig. 11, as in the case of water, by making the operating frequency F2 of the second pump 4b lower than the operating frequency F1 of the first pump 4a, it is possible to prevent a difference in flow rate between the new model and the old model.

The heat source system 1 of the present embodiment 1 includes a first heat medium heat exchanger 2a and a second heat medium heat exchanger 2b, a first heat source unit 3a and a second heat source unit 3b, a first pump 4a that circulates the heat medium to a heat medium circuit 6 including the first heat medium heat exchanger 2a and a load, a second pump 4b that circulates the heat medium to the heat medium circuit 6 including the second heat medium heat exchanger 2b and a load, and a controller 5 that controls the operating frequency of the first pump 4a and the second pump 4b. The controller 5 includes a storage means 22, an internal resistance calculation means 31, an external resistance calculation means 32, and a pump control means 33.

The internal resistance calculation means 31 calculates the internal resistance, which is the head loss of each of the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b. The external resistance calculation means 32 calculates the first external resistance using the internal resistance of the first heat medium heat exchanger 2a, and calculates the second external resistance using the internal resistance of the second heat medium heat exchanger 2b. The pump control means 33 controls the operating frequency F2 of the second pump 4b based on the operating frequency F1 of the first pump 4a so that the second external resistance approaches the first external resistance.

According to the first embodiment, the internal resistance of each of the first heat medium heat exchanger 2a of the old model and the second heat medium heat exchanger 2b of the new model is calculated for the heat medium flowing through the heat medium circuit 6, and the external resistance of the new model and the old model is calculated based on the internal resistance of each heat medium heat exchanger. Then, based on the difference in the external resistance of each of the heat medium heat exchangers of the new model and the old model, the operating frequency F2 of the second pump 4b on the new model side is set so that the flow rate difference between the new model and the old model is reduced. Since the flow rate difference between the heat medium flowing through the first heat medium heat exchanger 2a of the old model and the heat medium flowing through the second heat medium heat exchanger 2b of the new model is reduced, when the heat medium flowing through the first heat medium heat exchanger 2a and the heat medium flowing through the second heat medium heat exchanger 2b join at the joining point 45, the temperature difference between the heat media is suppressed. As a result, the stability of the temperature of the heat medium supplied to the load side device via the heat medium circuit 6 is improved.

When the fluid in the heat medium circuit 6 is water, the operating frequency F2 of the second pump 4b on the new model side is set so as to reduce the difference in flow rate between the new model and the old model based on the difference in the external resistance of the heat medium heat exchangers of the new model and the old model, which is calculated using the kinetic viscosity and density of water. Also, when the fluid in the heat medium circuit 6 is brine, which has a higher viscosity than water, the operating frequency F2 of the second pump 4b on the new model side is set so as to reduce the difference in flow rate between the new model and the old model based on the difference in the external resistance of the heat medium heat exchangers of the new model and the old model, which is calculated using the kinetic viscosity and density of brine.

Furthermore, according to the first embodiment, when the head loss of the second heat medium heat exchanger 2b of the new model is smaller than the head loss of the first heat medium heat exchanger 2a of the old model, the operating frequency F2 of the second pump 4b is set to a value smaller than the operating frequency F1 of the first pump 4a so as to reduce the flow rate difference between the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b. Therefore, it is possible to prevent the second pump 4b from being operated unnecessarily, and to reduce the power consumption of the second pump 4b.

Furthermore, according to the first embodiment, the worker who installs the heat source system 1 only needs to input the physical properties of the heat medium used in the heat medium circuit 6 into the controller 5 at the location where the heat source system 1 is installed. This saves the worker the trouble of measuring the flow rate of the heat medium flowing through the heat medium pipe 7a and the flow rate of the heat medium flowing through the heat medium pipe 7b, and fine-tuning the operating frequency F2 of the second pump 4b so that there is no difference between these flow rates.

(Variation 1)
A first modified example of the first embodiment will be described. Fig. 12 is a block diagram showing a configuration example of a heat source system according to the first modified example. The heat source system 1a has first heat source units 3a-1 to 3a-4, second heat source units 3b-1 to 3b-4, first heat medium heat exchangers 2a-1 and 2a-2, second heat medium heat exchangers 2b-1 and 2b-2, a first pump 4a, and a second pump 4b. In Fig. 12, the flow direction of the heat medium is indicated by a dashed arrow.

In FIG. 12, of the first heat source units 3a-1 to 3a-4, only the configuration of the first heat source unit 3a-1 is shown, but each of the first heat source units 3a-1 to 3a-4 has the same configuration. Of the second heat source units 3b-1 to 3b-4, only the configuration of the second heat source unit 3b-1 is shown in FIG. 12, but each of the second heat source units 3b-1 to 3b-4 has the same configuration. The first heat medium heat exchangers 2a-1 and 2a-2, which are heat medium heat exchangers of the old model, have the same configuration. The second heat medium heat exchangers 2b-1 and 2b-2, which are heat medium heat exchangers of the new model, have the same configuration.

In Modification 1, the cold heat generation capacity of the first heat source units 3a-1 to 3a-4 is different from the cold heat generation capacity of the second heat source units 3b-1 to 3b-4. The cold heat generation capacity of each of the second heat source units 3b-1 to 3b-4 is greater than the cold heat generation capacity of each of the first heat source units 3a-1 to 3a-4. Below, the second heat source units 3b-1 to 3b-4 are referred to as new model heat source units, and the first heat source units 3a-1 to 3a-4 are referred to as old model heat source units.

The heat medium pipe 7a branches into heat medium branch pipes 7a-1 and 7a-2 on the fluid downstream side of the first pump 4a, and the heat medium branch pipes 7a-1 and 7a-2 merge into the heat medium pipe 7a. The first heat medium heat exchanger 2a-1 is connected to the heat medium branch pipe 7a-1. The first heat source units 3a-1 and 3a-2 are connected to the first heat medium heat exchanger 2a-1. The first heat source units 3a-1 and 3a-2 supply cold heat to the first heat medium heat exchanger 2a-1. The first heat medium heat exchanger 2a-2 is connected to the heat medium branch pipe 7a-2. The first heat source units 3a-3 and 3a-4 are connected to the first heat medium heat exchanger 2a-2. The first heat source units 3a-3 and 3a-4 supply cold heat to the first heat medium heat exchanger 2a-2.

The heat medium pipe 7b branches into heat medium branch pipes 7b-1 and 7b-2 on the fluid downstream side of the second pump 4b, and the heat medium branch pipes 7b-1 and 7b-2 merge into the heat medium pipe 7b. The second heat medium heat exchanger 2b-1 is connected to the heat medium branch pipe 7b-1. The second heat source units 3b-1 and 3b-2 are connected to the second heat medium heat exchanger 2b-1. The second heat source units 3b-1 and 3b-2 supply cold heat to the second heat medium heat exchanger 2b-1. The second heat medium heat exchanger 2b-2 is connected to the heat medium branch pipe 7b-2. The second heat source units 3b-3 and 3b-4 are connected to the second heat medium heat exchanger 2b-2. The second heat source units 3b-3 and 3b-4 supply cold heat to the second heat medium heat exchanger 2b-2.

The first heat source unit 3a-1 has an accumulator 16a in addition to the compressor 11a, heat source side heat exchanger 12a, expansion valve 13a, and fan 14a shown in FIG. 1. The accumulator 16a is connected to the refrigerant suction port side of the compressor 11a. The second heat source unit 3b-1 has an injection circuit 17 and an accumulator 16b in addition to the compressor 11b, heat source side heat exchanger 12b, expansion valve 13b, and fan 14b shown in FIG. 1. The injection circuit 17 is provided with an expansion valve 18. The accumulator 16b is connected to the refrigerant suction port side of the compressor 11b.

In Modification 1, the type of refrigerant circulating through the refrigerant circuit 10b of the new model heat source machine is different from the type of refrigerant circulating through the refrigerant circuit 10a of the old model heat source machine. In the new model heat source machine, an injection circuit 17 is provided so that cold heat can be generated more efficiently by circulating a refrigerant different from the refrigerant of the old model through the refrigerant circuit 10a. Also, in Modification 1, the heat exchange efficiency of the heat source side heat exchanger 12b may be greater than the heat exchange efficiency of the heat source side heat exchanger 12a. For example, as the heat transfer tubes, a circular tube (not shown) may be used for the heat source side heat exchanger 12a, and a flat tube (not shown) may be used for the heat source side heat exchanger 12b.

The pump frequency control of the heat source system 1 described with reference to Figs. 1 to 11 can be applied to the heat source system 1a shown in Fig. 12. Also, as described with reference to Fig. 12, the number of heat source units connected to the heat medium heat exchanger of each of the new model and the old model may be multiple.

Furthermore, the difference between the new model and the old model is not limited to the pipe specifications of the heat medium heat exchanger. The cold heat generation capacity of the heat source machine that supplies cold heat to the heat medium heat exchanger of the old model may be different from the cold heat generation capacity of the heat source machine that supplies cold heat to the heat medium heat exchanger of the new model. Even in the heat source system 1a in which heat source machines with different heat generation capacities are mixed as in variant example 1, by focusing on the difference in the pipe specifications of the heat medium heat exchanger and applying pump frequency control of the heat source system 1, it is possible to improve the stability of the heat medium temperature and reduce power consumption.

Embodiment 2.
The present embodiment 2 is intended to improve the accuracy of the kinetic viscosity used in the pump control described in the embodiment 1. In the present embodiment 2, the same components as those described in the embodiment 1 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, in cases where the components and operations described in the embodiment 1 are similar in the present embodiment 2, detailed descriptions thereof will be omitted.

The configuration of the controller of the heat source system of the second embodiment is described below. Figure 13 is a functional block diagram showing an example of the configuration of the controller of the heat source system of the second embodiment.

In the second embodiment, the storage means 22 stores a first table which is information indicating the viscosity of the heat medium with the outflow temperature Tb and the concentration of the freezing point depressant contained in the heat medium as parameters. The storage means 22 stores a second table which is information indicating the density with the outflow temperature Tb and the concentration of the freezing point depressant contained in the heat medium as parameters.

FIG. 14 is a diagram showing an example of a first table stored in the storage means shown in FIG. 13. FIG. 15 is a diagram showing an example of a second table stored in the storage means shown in FIG. 13. In the first table shown in FIG. 14, viscosity values are recorded corresponding to the outflow temperature Tb and the concentration of the freezing point depressant contained in the heat medium. In the second table shown in FIG. 15, density values are recorded corresponding to the outflow temperature Tb and the concentration of the freezing point depressant contained in the heat medium.

In this second embodiment, compared to the configuration shown in FIG. 2, the heat medium circuit control means 30a has a kinetic viscosity calculation means 34. The kinetic viscosity calculation means 34 refers to the first table and the second table, and selects the viscosity and density corresponding to the outflow temperature Tb detected by the first outflow temperature sensor 8a or the second outflow temperature sensor 8b. The kinetic viscosity calculation means 34 then divides the selected viscosity by the selected density to obtain the kinetic viscosity of the heat medium.

Next, the operation of the heat source system 1 of the present embodiment 2 will be described with reference to Figs. 8 and 16. Descriptions of operations similar to those of the embodiment 1 will be omitted. Fig. 16 is a flowchart showing the operation of step S14 shown in Fig. 8 in the embodiment 2. Note that steps S112 to S115 shown in Fig. 16 are similar to the operations of steps S101 to S104 described with reference to Fig. 9, and therefore detailed descriptions thereof will be omitted.

In this second embodiment, in step S13 shown in FIG. 8, an instruction to select brine is input instead of the physical properties of brine. In step S111 shown in FIG. 16, the kinetic viscosity calculation means 34 calculates the kinetic viscosity using the viscosity and density corresponding to the outflow temperature Tb of the heat medium.

Specifically, when an instruction to select brine is input, the kinetic viscosity calculation means 34 receives the value of the outflow temperature Tb from the first outflow temperature sensor 8a or the second outflow temperature sensor 8b. The kinetic viscosity calculation means 34 then refers to the first table and the second table stored in the storage means 22, and selects the viscosity and density corresponding to the outflow temperature Tb. The kinetic viscosity calculation means 34 then calculates the kinetic viscosity using the selected viscosity and selected density and the formula (kinetic viscosity = viscosity / density).

According to the second embodiment, the kinetic viscosity is calculated accurately in accordance with the type and temperature of the heat medium used in the heat medium circuit 6, improving the accuracy of the flow rate control.

In the second embodiment, the storage means 22 may store a first table and a second table for each of the multiple types of heat media. In this case, when one heat medium is selected from the multiple types of heat media and the kinetic viscosity calculation means 34 receives the outflow temperature Tb from the outflow temperature sensor, the kinetic viscosity calculation means 34 refers to the information stored in the storage means 22 and determines the kinetic viscosity of the selected heat medium. In this case, assuming that the heat medium used in the heat medium circuit 6 is selected from multiple types, the kinetic viscosity is accurately calculated in accordance with the type and temperature of the selected heat medium, improving the accuracy of the flow control.

In addition, in the second embodiment, the heat medium is described as being brine, but the heat medium may be water. Since the physical properties of water also change with temperature, the storage means 22 may store one or both of the first table and the second table for water. In this case, even if the heat medium is water, the effect of improving the accuracy of flow rate control can be obtained.

In the above-mentioned first and second embodiments, the heat source system 1 has been described as generating cold heat, but it may also be a system that generates hot heat. Also, in the above-mentioned first and second embodiments, the information on the total head stored in the storage means 22 has been described as being for the case where the heat medium is water, but information on the total head for each type of brine may also be stored. Since the absolute value of the total head decreases as the kinetic viscosity increases, the total head may differ depending on the type of brine. Therefore, the storage means 22 may store information on the total head corresponding to the type of brine. In this case, the external resistance calculation means 32 reads out from the storage means 22 the value of the total head corresponding to the brine used in the heat medium circuit 6 and calculates the external resistance. This improves the accuracy of the flow control.

1, 1a heat source system, 2a, 2a-1, 2a-2 first heat medium heat exchanger, 2b, 2b-1, 2b-2 second heat medium heat exchanger, 3a, 3a-1 to 3a-4 first heat source unit, 3b, 3b-1 to 3b-4 second heat source unit, 4a first pump, 4b second pump, 5 controller, 6 heat medium circuit, 7a, 7b heat medium piping, 7a-1, 7a-2 heat medium branch piping, 7b-1, 7b-2 heat medium branch piping, 8a first outflow temperature sensor, 8b second outflow temperature sensor, 10a, 10b refrigerant circuit, 11a, 11b compressor, 12a, 12b heat source side heat exchanger, 13a, 13b expansion valve, 14a, 14b fan, 15a, 15b refrigerant piping, 16a, 16b accumulator, 17 injection circuit, 18 expansion valve, 20 input means, 21 refrigeration cycle control means, 22 storage means, 30, 30a heat medium circuit control means, 31 internal resistance calculation means, 32 external resistance calculation means, 33 pump control means, 34 kinetic viscosity calculation means, 41 forward fluid header pipe, 42 return fluid header pipe, 43 load device, 44 branch point, 45 junction point, 51-53 heat medium piping, 54 bypass piping, 90 processing circuit, 91 processor, 92 memory, 93 bus.

Claims

a first heat medium heat exchanger connected in series to the load and exchanging heat between a refrigerant and a heat medium;
a second heat medium heat exchanger connected in parallel to the first heat medium heat exchanger with respect to the load and exchanging heat between the refrigerant and the heat medium;
A first heat source unit connected to the first heat medium heat exchanger and including a refrigerant circuit through which the refrigerant circulates;
A second heat source unit connected to the second heat medium heat exchanger and including a refrigerant circuit through which the refrigerant circulates;
a first pump connected in series with the first heat medium heat exchanger and configured to circulate the heat medium through a heat medium circuit including the first heat medium heat exchanger and the load;
a second pump connected in series with the second heat medium heat exchanger and configured to circulate the heat medium through a heat medium circuit including the second heat medium heat exchanger and the load;
a controller for controlling an operating frequency of the first pump and the second pump;
The controller:
an internal resistance calculation means for calculating an internal resistance which is a head loss of each of the first heat medium heat exchanger and the second heat medium heat exchanger;
an external resistance calculation means for calculating a first external resistance using the internal resistance of the first heat medium heat exchanger and for calculating a second external resistance using the internal resistance of the second heat medium heat exchanger;
and a pump control means for controlling an operation frequency of the second pump based on an operation frequency of the first pump so that the second external resistance approaches the first external resistance.
Heat source system.
The second heat medium heat exchanger is configured such that the head loss of the second heat medium heat exchanger is smaller than the head loss of the first heat medium heat exchanger.
The heat source system according to claim 1 .
The second heat medium heat exchanger has a heat transfer area larger than a heat transfer area of the first heat medium heat exchanger.
The heat source system according to claim 2 .
a storage means for storing information on pipe specifications including lengths and diameters of pipes inside the first heat medium heat exchanger and the second heat medium heat exchanger,
The internal resistance calculation means
determining the internal resistance of each of the first heat medium heat exchanger and the second heat medium heat exchanger based on information on the density and kinetic viscosity of the heat medium and on pipe specifications of each of the first heat medium heat exchanger and the second heat medium heat exchanger;
The heat source system according to any one of claims 1 to 3.
the memory means stores information on the total head of each of the first pump and the second pump;
The external resistance calculation means
calculating the first external resistance by subtracting the internal resistance of the first heat medium heat exchanger from the total head of the first pump, and calculating the second external resistance by subtracting the internal resistance of the second heat medium heat exchanger from the total head of the second pump;
The heat source system according to claim 4.
an outlet temperature sensor provided at an outlet of the heat medium of the first heat medium heat exchanger or the second heat medium heat exchanger for detecting an outlet temperature, which is a temperature of the heat medium flowing out from the outlet;
The storage means includes:
storing a first table which is information indicating the viscosity of the heat medium with the outflow temperature and the concentration of a freezing point depressant contained in the heat medium as parameters, and a second table which is information indicating the density of the heat medium with the outflow temperature and the concentration as parameters;
The controller:
a kinetic viscosity calculation means for calculating the kinetic viscosity of the heat medium by referring to the first table and the second table, selecting the viscosity and the density corresponding to the outflow temperature detected by the outflow temperature sensor, and dividing the selected viscosity by the selected density;
The heat source system according to claim 4 or 5.
the storage means stores information on the total head of each of the first pump and the second pump for each of a plurality of types of heat transfer media;
The external resistance calculation means
When one heat medium is selected from the plurality of types of heat medium, information on the total head of the first pump and the total head of the second pump corresponding to the selected heat medium is read from the storage means, and the first external resistance and the second external resistance are calculated.
The heat source system according to claim 5 .