Heat source system

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

[0001] The present disclosure relates to a heat source system having a heat medium circuit.

[0002] BACKGROUND ART As an example of a conventional heat source system, Patent Document 1 discloses a heat source system in which a plurality of heat source devices are connected in parallel to a heat medium circuit.

[0003] In a conventional heat source system, each of a plurality of heat source machines is connected to a supply water header pipe and a return water header pipe via water piping. Each of the plurality of heat source machines is provided with a refrigeration cycle circuit through which a refrigerant circulates. The refrigeration cycle circuit is provided with a load heat exchanger that exchanges heat between the refrigerant and water circulating through the water piping. A flow control pump is provided on the water piping connected to each of the plurality of heat source machines. Each of the plurality of flow control pumps circulates water from the return water header pipe to the load heat exchanger via the water piping, and then sends the water to the supply water header pipe. The water that has exchanged heat with the refrigerant in each of the plurality of load heat exchangers circulates through the load device via the supply water header pipe and then returns to the return water header pipe.

[0004] Currently, HFC refrigerants such as R410A and 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). 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 replacement refrigerants.

[0005] International Publication No. 2017 / 068631

[0006] The piping specifications of the load-side heat exchangers installed in the heat source units of conventional heat source systems may differ between the old model, which is compatible with the currently used refrigerant, and the new model, which is compatible with the replaced refrigerant. 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. Furthermore, depending on the circumstances of the heat source system owner, it may be difficult to simultaneously replace all of the multiple heat source units with heat source units having new load-side heat exchangers. In this case, a single heat source system may contain a mixture of old and new load-side heat exchangers.

[0007] In the heat source system disclosed in Patent Document 1, when older and newer load-side heat exchangers are mixed, a difference in flow rate occurs between the water flowing through the older load-side heat exchanger and the water flowing through the new load-side heat exchanger. If the difference in flow rate between the multiple parallel water circuits is large, the temperature stability of the water supplied to the load device decreases.

[0008] The present disclosure has been made to solve the above-mentioned problems, and provides a heat source system that can stabilize the temperature of the fluid supplied to the load even if the head losses of multiple heat medium heat exchangers connected in parallel are different.

[0009] A 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 machine connected to the first heat medium heat exchanger and including a refrigerant circuit through which the refrigerant circulates, a second heat source machine 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 a refrigerant circuit through which the refrigerant circulates. 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, wherein 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 based on the operating frequency of the first pump so that the second external resistance approaches the first external resistance.

[0010] According to the present disclosure, the internal resistances of the first and second heat medium heat exchangers for the heat medium circulating through the heat medium circuit are calculated, and the external resistances of each heat medium heat exchanger are calculated based on the internal resistances of each heat medium heat exchanger. The operating frequency of the second pump is then set based on the difference in the external resistances of each heat medium heat exchanger to minimize the difference in flow rate between these heat medium heat exchangers. Since the difference in flow rate 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 reduced. As a result, the temperature stability of the heat medium supplied to the load-side device via the heat medium circuit is improved.

[0011] 14 is a block diagram showing an example of the configuration of a heat source system according to embodiment 1. FIG. 15 is a functional block diagram showing an example of the configuration of a controller of the heat source system according to embodiment 1. FIG. 16 is a graph showing the relationship between flow rate and head loss for a plurality of types of heat medium. FIG. 17 is a graph showing an example of the total head of the first pump shown in FIG. 1. FIG. 18 is a graph showing examples of external resistances of an old model and a new model. FIG. 19 is a hardware configuration diagram showing an example of the configuration of the controller shown in FIG. 2. FIG. 20 is a hardware configuration diagram showing another example of the configuration of the controller shown in FIG. 2. FIG. 19 is a flowchart showing the operation procedure of the heat source system according to embodiment 1. FIG. 19 is a flowchart showing the operation procedure of steps S14 and S15 shown in FIG. 8. FIG. 19 is a graph showing examples of external resistances of an old model and a new model when the heat medium is water. FIG. 19 is a block diagram showing an example of the configuration of a heat source system according to modified example 1. FIG. 19 is a functional block diagram showing an example of the configuration of a controller of the heat source system according to embodiment 2. FIG. 19 is a diagram showing an example of a first table stored in the storage means shown in FIG. 13. FIG. 19 is a diagram showing an example of a second table stored in the storage means shown in FIG. 13. FIG. 19 is a flowchart showing the operation of step S14 shown in FIG. 8 in embodiment 2.

[0012] Embodiment 1. The configuration of a heat source system according to Embodiment 1 will be described. Fig. 1 is a block diagram showing an example of the configuration of a heat source system according to Embodiment 1. First, the overall configuration of the heat source system 1 will be described with reference to Fig. 1. The heat source system 1 includes 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.

[0013] 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-pipe 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 smaller 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 will be referred to as the old-model heat medium heat exchanger, and the second heat medium heat exchanger 2b will be referred to as the new-model heat medium heat exchanger.

[0014] In addition, in the first embodiment, 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).

[0015] As shown in Fig. 1 , the load device 43 that uses the cold energy 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 pipe 54.

[0016] The heat medium pipe 52 branches into a heat medium pipe 7a and a heat medium pipe 7b at a branch point 44. The heat medium pipe 7a and the heat medium pipe 7b join at a junction 45 and are connected to the 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.

[0017] 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 through 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 the heat medium circuit 6 through 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.

[0018] 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 through 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.

[0019] 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 an outlet temperature Tb 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 an outlet temperature Tb 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 signal lines (not shown).

[0020] Next, the configurations 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 dashed arrows.

[0021] 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 Figure 1, the flow direction of the refrigerant circulating through the refrigerant circuit 10b is indicated by dashed arrows.

[0022] Next, the configuration of the first heat source unit 3a will be described. The compressor 11a draws in low-temperature, low-pressure refrigerant, compresses it, and discharges it. The compressor 11a is an inverter compressor whose capacity can be adjusted by changing its 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 heat exchanger having heat transfer tubes and multiple heat dissipation fins. The expansion valve 13a decompresses and expands the liquid refrigerant flowing in from the heat source-side heat exchanger 12a. 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 the same configuration as the first heat source unit 3a, and therefore a detailed description thereof will be omitted.

[0023] Next, the configuration of the controller 5 will be described. Fig. 2 is a functional block diagram showing an example 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.

[0024] An input means 20 for inputting values ​​of physical properties such as the density and kinematic viscosity of the heat medium is connected to the controller 5. The input means 20 is, for example, a remote controller (not shown) that is communicatively connected to 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.

[0025] In the functional block diagram shown in Fig. 2 , 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. In addition, Fig. 2 schematically shows that 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 also be provided to the external resistance calculation means 32 and the pump control means 33 via the internal resistance calculation means 31.

[0026] Furthermore, in the first embodiment, the input means 20 is connected to the controller 5 so that an operator can input the physical property values ​​of the heat medium. However, the input means 20 does not necessarily have to be used. For example, if a control board (not shown) mounted on the first heat source unit 3 a or the second heat source unit 3 b 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 or the method of switching the switch provided on the control board (not shown).

[0027] The refrigeration cycle control means 21 controls the operating frequency of the compressors 11a and 11b, the opening degree of the expansion valves 13a and 13b, and the rotation frequency of the fans 14a and 14b so that the outflow temperatures Tb received from the first outflow temperature sensor 8a and the second outflow temperature sensor 8b, respectively, fall within a predetermined range based on the set temperature of the load device 43.

[0028] The storage means 22 stores information related to head loss for each of the first heat medium heat exchanger 2 a and the second heat medium heat exchanger 2 b 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 pipes in the heat medium heat exchangers.

[0029] The storage means 22 also stores a calculation formula for determining the head loss of the heat medium from the kinematic viscosity and specific gravity of the heat medium. Examples of such calculation formulas include the Darcy-Weisbach formula and the Brasilius formula. The head loss for water may be calculated using an approximate formula created in advance based on test values. The storage means 22 stores information on the total heads 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 the storage means 22 only needs to store information on the total head of one of the pumps. The total head of a pump is usually described in the pump specifications.

[0030] When the values ​​of the 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 pipeline 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 2 a and the second heat medium heat exchanger 2 b, as follows.

[0031] The internal resistance calculation means 31 calculates the head loss of the heat medium using the kinematic 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.

[0032]

[0033] 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 [m] of the piping in the heat medium heat exchanger, and D is the diameter [m] of the piping. ρ is the density [kg / l] of the heat medium, and u is the flow velocity [m / s] of the heat medium. During turbulent flow (3 x 10^2 < Re < 1 x 10^5), f in equation (1) can be calculated using the Brasilius equation shown in equation (2).

[0034]

[0035] 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 kinematic viscosity of the heat transfer medium [m ２ / s].

[0036]

[0037] When the flow rates of 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).

[0038]

[0039] 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, according 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.

[0040] 3 is a graph showing the relationship between the flow rate and the head loss for a plurality of types of heat transfer medium. The vertical axis of FIG. 3 represents the head loss [kPa], and the horizontal axis represents the flow rate of the heat transfer medium circuit [m ３ / h]. Wg is the kinematic viscosity of 1.79 [mm ２ / s] and the specific gravity is 1.00. Bg1 is the case of water with a kinematic viscosity of 35.6 [mm ２ / s] and a specific gravity of 1.06. Bg2 is a brine having a kinematic viscosity of 13.7 [mm ２ / s] and a brine (55 wt%) with a specific gravity of 1.08. Bg3 shows a kinematic viscosity of 5.56 [mm ２ / s] and brine (40 wt%) with a specific gravity of 1.05. From Figure 3, it can be seen that the head loss varies even at the same flow rate depending on the physical properties of the heat medium. The storage means 22 stores information on the Wg graph shown in Figure 3 for each heat medium heat exchanger of the old and new models.

[0041] 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 the first embodiment, the first pump 4a and the second pump 4b have the same capacity, so the explanation will be given for the first pump 4a. Figure 4 is a graph showing an example of the total head of the first pump shown in Figure 1.

[0042] The total head shown in Figure 4 is for a pump capacity of 5.5 kW and an operating frequency F1 of the pump of 50 Hz. The total head when the frequency changes can be calculated using the following formula. For example, when the operating frequency F1 of the pump is 50 Hz and the flow rate is 0 m ３ / h], the total head is 34 [m], the pump operating frequency F1 is 40 [Hz], the flow rate is 0 [m ３ / h], the external resistance calculation means 32 calculates the total head as 34 [m] × (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 of the heat medium circuit [m ３ / h].

[0043] The external resistance calculation means 32 then converts the unit of the total head from [m] to [kPa]. Specifically, the external resistance calculation means 32 calculates the total head [m] × gravitational acceleration [m / s ２] × brine specific gravity). Brine specific gravity is the specific gravity of 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 determined total head and the internal resistance determined by the internal resistance calculation means 31 for each of the new and old models, thereby determining the external resistance [kPa], which is the external head. In other words, the external resistance calculation means 32 determines the external resistance for each heat medium heat exchanger of the new and old models using the formula (external resistance = total head - internal resistance).

[0044] 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 represents the external resistance [kPa], and the horizontal axis represents the flow rate of the heat medium circuit [m ３ / h]. The solid line shows the external resistance of the new model heat medium heat exchanger. The dashed line shows the external resistance of the old model heat medium heat exchanger. From Figure 5, it can be seen that the external resistance of the new model is different from that of the old model.

[0045] 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 varies depending on the operating frequency of the pump. Because the external resistance calculated by changing the total head also varies with the total head, the pump control means 33 executes control to change the operating frequency F2 of the second pump 4b when the operating frequency F1 of the first pump 4a changes so that the external resistance of the new model approaches that of the old model. For example, in the graph shown in FIG. 5 , the pump control means 33 controls the operating frequency F2 of the second pump 4b to be lowered relative to the flow rate at the current operating frequency F1 of the first pump 4a so that the solid line representing the external resistance of the new model overlaps with the dashed line representing the external resistance of the old model.

[0046] Here, an example of 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 by a processing circuit 90 as shown in Fig. 6. The functions of the refrigeration cycle control means 21, storage means 22, internal resistance calculation means 31, external resistance calculation means 32, and pump control means 33 shown in Fig. 2 are realized by the processing circuit 90.

[0047] When each function is performed 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 thereof. The functions of each 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 separate processing circuits 90. Furthermore, the functions of each 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.

[0048] Another example of hardware for the controller 5 shown in Fig. 2 will now 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 configured with 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 communicably connected to each other via a bus 93.

[0049] When each function is executed by software, 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 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.

[0050] The memory 92 may be a non-volatile semiconductor memory such as a read-only memory (ROM), a flash memory, an erasable and programmable ROM (EPROM), or an electrically erasable and programmable ROM (EEPROM). Alternatively, the memory 92 may be a volatile semiconductor memory such as a random access memory (RAM). Alternatively, the memory 92 may be a removable recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disc (CD), a mini disc (MD), or a digital versatile disc (DVD).

[0051] In the first embodiment, the first pump 4a and the second pump 4b have the same performance, but they may have different performances. In this case, the storage unit 22 stores information on the total head of each of the first pump 4a and the second pump 4b.

[0052] Next, a description will be given of the operation of the heat source system 1 according to the present embodiment 1. Fig. 8 is a flowchart showing the operation procedure of the heat source system according to the present embodiment 1. Fig. 9 is a flowchart showing the operation procedure of steps S14 and S15 shown in Fig. 8.

[0053] Here, the case will be described where the input means 20 is an information processing terminal (not shown) carried by a 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.

[0054] 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 a built-in type or not. When a response indicating that the pump is not a built-in type is input via the information processing terminal (not shown) (No in step S11), the heat medium circuit control means 30 ends the processing.

[0055] In the determination process of step S11, if a response indicating that the pump is built-in is input (if Yes in step S11), the heat medium circuit control means 30 causes the information processing terminal (not shown) to display a message asking the operator whether or not new and old models of heat medium heat exchangers are mixed (step S12).If a response indicating that new and old models of heat medium heat exchangers are not mixed is input via the information processing terminal (not shown) (if No in step S12), the heat medium circuit control means 30 ends the process.

[0056] In the determination process of step S12, if a response indicating that new model heat medium heat exchangers and old model heat medium heat exchangers are mixed is input via an information processing terminal (not shown) (if Yes in step S12), the heat medium circuit control means 30 determines whether the physical properties of the brine have been input (step S13). Note that the method of inputting the physical properties of the heat medium used in the heat medium circuit 6 to the controller 5 is not limited to using the input means 20. For example, if a control board (not shown) mounted on the first heat source unit 3 a or the second heat source unit 3 b has a switch (e.g., a DIP switch or a rotary switch) for inputting the physical properties of the heat medium, the operator may input the physical properties of the heat medium to the controller 5 by switching the switch on the control board. Furthermore, the method of inputting the physical properties of the heat medium used in the heat medium circuit 6 to the controller 5 is not limited to using the input means 20 or switching the switch on the control board (not shown).

[0057] In the determination 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 accordance with 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 determination 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 accordance with the physical properties of water so that the flow rate of the new model approaches the flow rate of the old model (step S15).

[0058] 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.

[0059] When the values ​​of the density and kinetic viscosity of the heat medium are input, the in-machine resistance calculation means 31 calculates the in-machine 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 in-machine resistance calculation means 31 calculates the in-machine 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 equations (1) to (4).

[0060] 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. The external resistance calculation means 32 also 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.

[0061] The pump control means 33 determines an 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).

[0062] 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 because the storage means 22 stores information on the head loss based on the case where the heat medium is water.

[0063] FIG. 10 is a graph showing an example of the external resistance of an old model and a new model when the heat medium is water. FIG. 11 is a graph showing an example of the external resistance of an old model and a new model when the heat medium is brine. The brine shown in this graph is brine with a freezing point depressant concentration of ethylene glycol or propylene glycol, etc., of 70 wt %. The vertical axis of FIGS. 10 and 11 represents the external resistance [kPa], and the horizontal axis represents the flow rate [m ３ / h]. In Figures 10 and 11, the solid lines show the external resistance of the new model heat medium heat exchanger. The dashed lines show the external resistance of the old model heat medium heat exchanger. Figures 10 and 11 show the cases where the pump capacities are 2.2 kW, 3.7 kW, and 5.5 kW, and the operating frequencies of the first pump 4a and the second pump 4b are 50 Hz.

[0064] In FIG. 10, for example, when the pump capacity is 5.5 kW, when the external resistance is 0, the flow rate of the old model is 42.5 [m ３ / h], whereas the new model has a flow rate of 45.0 [m ３ / h]. By reducing the operating frequency F2 of the second pump 4b from 50 Hz to approximately 48 Hz, it is possible to eliminate the difference in flow rate between the new model and the old model.

[0065] In FIG. 11, for example, when the pump capacity is 5.5 kW, when the external resistance is 0, the flow rate of the old model is 38.0 [m ３ / h], whereas the new model has a flow rate of 41.5 [m ３ 11, similarly to the case of water, by setting 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.

[0066] The heat source system 1 of the first embodiment 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 through 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 through the heat medium circuit 6 including the second heat medium heat exchanger 2b and a load, and a controller 5 that controls the operating frequencies 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.

[0067] The internal resistance calculation means 31 calculates the internal resistances, which are head losses of the first heat medium heat exchanger 2 a and the second heat medium heat exchanger 2 b. The external resistance calculation means 32 calculates the first external resistance using the internal resistance of the first heat medium heat exchanger 2 a, and calculates the second external resistance using the internal resistance of the second heat medium heat exchanger 2 b. The pump control means 33 controls the operating frequency F2 of the second pump 4 b based on the operating frequency F1 of the first pump 4 a so that the second external resistance approaches the first external resistance.

[0068] According to the first embodiment, the internal resistances of the first heat medium heat exchanger 2a of the old model and the second heat medium heat exchanger 2b of the new model are calculated for the heat medium circulating through the heat medium circuit 6, and the external resistances of the new and old models are calculated based on the internal resistances of the heat medium heat exchangers. The operating frequency F2 of the second pump 4b on the new model side is then set based on the difference in the external resistances of the heat medium heat exchangers of the new and old models to minimize the difference in flow rate between the new and old models. Because the difference in flow rate between the heat medium circulating through the first heat medium heat exchanger 2a of the old model and the heat medium circulating through the second heat medium heat exchanger 2b of the new model is reduced, the temperature difference between the heat medium circulating through the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b is reduced when they merge at the junction 45. As a result, the temperature stability of the heat medium supplied to the load-side device via the heat medium circuit 6 is improved.

[0069] 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 based on the difference in external resistance between the heat medium heat exchangers of the new model and the old model, which is calculated using the kinetic viscosity and density of water, so as to reduce the difference in flow rate between the new model and the old model. 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 based on the difference in external resistance between the heat medium heat exchangers of the new model and the old model, which is calculated using the kinetic viscosity and density of brine, so as to reduce the difference in flow rate between the new model and the old model.

[0070] 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 difference in flow rate between the first heat medium heat exchanger 2a and the second heat medium heat exchanger 2b. This prevents the second pump 4b from being operated unnecessarily, and reduces the power consumption of the second pump 4b.

[0071] Furthermore, according to the first embodiment, the worker installing the heat source system 1 simply inputs the physical properties of the heat medium used in the heat medium circuit 6 into the controller 5 at the installation site of the heat source system 1. This eliminates the need for the worker to measure 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 to fine-tune the operating frequency F2 of the second pump 4b so as to prevent a difference between these flow rates.

[0072] (Variation 1) Variation 1 of the first embodiment will be described. Fig. 12 is a block diagram showing an example configuration of a heat source system according to Variation 1. The heat source system 1a includes 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 dashed arrows.

[0073] 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 the first heat source units 3a-1 to 3a-4 have 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, but the second heat source units 3b-1 to 3b-4 have 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.

[0074] 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. Hereinafter, the second heat source units 3b-1 to 3b-4 will be referred to as new model heat source units, and the first heat source units 3a-1 to 3a-4 will be referred to as old model heat source units.

[0075] 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. A first heat medium heat exchanger 2a-1 is connected to the heat medium branch pipe 7a-1. 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 energy to the first heat medium heat exchanger 2a-1. Furthermore, a first heat medium heat exchanger 2a-2 is connected to the heat medium branch pipe 7a-2. 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 energy to the first heat medium heat exchanger 2a-2.

[0076] 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. A second heat medium heat exchanger 2b-1 is connected to the heat medium branch pipe 7b-1. 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 to the second heat medium heat exchanger 2b-1. In addition, a second heat medium heat exchanger 2b-2 is connected to the heat medium branch pipe 7b-2. 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 to the second heat medium heat exchanger 2b-2.

[0077] 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.

[0078] 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. The new model heat source machine is provided with an injection circuit 17 so that cold 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 heat transfer tubes, circular tubes (not shown) may be used for the heat source-side heat exchanger 12a, and flat tubes (not shown) may be used for the heat source-side heat exchanger 12b.

[0079] The pump frequency control of the heat source system 1 described with reference to Figures 1 to 11 can be applied to the heat source system 1a shown in Figure 12. Furthermore, as described with reference to Figure 12, a plurality of heat source units may be connected to each of the heat medium heat exchangers of the new model and the old model.

[0080] Furthermore, the difference between the new and old models is not limited to the pipe specifications of the heat medium heat exchangers. The cold heat generation capacity of the heat source unit that supplies cold to the heat medium heat exchanger of the old model may be different from the cold heat generation capacity of the heat source unit that supplies cold to the heat medium heat exchanger of the new model. Even in the heat source system 1a in which heat source units with different heat generation capacities are mixed, as in Variation 1, by focusing on the differences in the pipe specifications of the heat medium heat exchangers and applying pump frequency control to the heat source system 1, it is possible to improve the stability of the heat medium temperature and reduce power consumption.

[0081] Embodiment 2. This embodiment 2 improves the accuracy of the kinematic viscosity used in the pump control described in embodiment 1. In this embodiment 2, the same components as those described in embodiment 1 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, in cases where the configurations and operations described in embodiment 1 are similar in this embodiment 2, detailed descriptions thereof will be omitted.

[0082] A description will be given of the configuration of the controller of the heat source system according to Embodiment 2. Fig. 13 is a functional block diagram showing an example of the configuration of the controller of the heat source system according to Embodiment 2.

[0083] In the second embodiment, the storage unit 22 stores a first table containing information indicating the viscosity of the heat medium using as parameters the outflow temperature Tb and the concentration of the freezing-point depressant contained in the heat medium, and a second table containing information indicating the density of the heat medium using as parameters the outflow temperature Tb and the concentration of the freezing-point depressant contained in the heat medium.

[0084] 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. The first table shown in Fig. 14 describes viscosity values ​​corresponding to outflow temperature Tb and the concentration of the freezing-point depressant contained in the heat medium. The second table shown in Fig. 15 describes density values ​​corresponding to outflow temperature Tb and the concentration of the freezing-point depressant contained in the heat medium.

[0085] In the 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 calculates the kinetic viscosity of the heat medium by dividing the selected viscosity by the selected density.

[0086] Next, the operation of the heat source system 1 of the second embodiment will be described with reference to Fig. 8 and Fig. 16. Description of operations similar to those of the first embodiment will be omitted. Fig. 16 is a flowchart showing the operation of step S14 shown in Fig. 8 in the second embodiment. 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 description thereof will be omitted.

[0087] In the second embodiment, an instruction to select brine is input instead of the physical properties of brine in step S13 shown in Fig. 8. In step S111 shown in Fig. 16, the kinematic viscosity calculation means 34 calculates the kinematic viscosity using the viscosity and density corresponding to the outflow temperature Tb of the heat medium.

[0088] Specifically, when an instruction to select brine is input, the kinematic 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. Then, the kinematic viscosity calculation means 34 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. Thereafter, the kinematic viscosity calculation means 34 calculates the kinematic viscosity using the selected viscosity and selected density and the equation (kinematic viscosity = viscosity / density).

[0089] According to the second embodiment, the kinematic viscosity is calculated with high accuracy in accordance with the type and temperature of the heat medium used in the heat medium circuit 6, thereby improving the accuracy of flow rate control.

[0090] In the second embodiment, the storage means 22 may store a first table and a second table for each of a plurality of types of heat medium. In this case, when one heat medium is selected from the plurality of types of heat medium and the outflow temperature Tb is received from the outflow temperature sensor, the kinematic viscosity calculation means 34 refers to the information stored in the storage means 22 and calculates the kinematic viscosity of the selected heat medium. In this case, assuming that the heat medium used in the heat medium circuit 6 is selected from a plurality of types, the kinematic viscosity is accurately calculated corresponding to the type and temperature of the selected heat medium, improving the accuracy of flow rate control.

[0091] Furthermore, in the second embodiment, the heat medium is described as 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.

[0092] In the above-described 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. Furthermore, in the above-described first and second embodiments, the total head information stored in the storage means 22 has been described as being for the case where the heat medium is water, but total head information 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 vary depending on the type of brine. Therefore, the storage means 22 may store total head information 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 flow rate control.

[0093] 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 kinematic viscosity calculation means, 41 forward fluid header pipe, 42 return fluid header pipe, 43 load device, 44 branch point, 45 junction point, 51 to 53 heat medium piping, 54 bypass piping, 90 processing circuit, 91 processor, 92 memory, 93 bus.

Claims

1. 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.

2. 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 .

3. 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 .

4. 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.

5. 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.

6. 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.

7. 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 .