Heat source system

Abstract

This heat source system comprises: a plurality of heat source machines (1, 2) including a variable-speed turbo heat source machine (1); and an operation number control device (3) for controlling the number of the plurality of heat source machines (1, 2) that are being operated. The operation number control device (3) is configured so as to: calculate a load index value of the variable-speed turbo heat source machine (1) by multiplying a relative value of the opening degree of an intake guide vane (16) in the variable-speed turbo heat source machine (1) by a relative value of the rotation speed of a compressor (11) in the variable-speed turbo heat source machine (1); increase the number of the heat source machines that are being operated when the load index value exceeds a first reference value; and reduce the number of the heat source machines that are being operated when the load index value falls below a second reference value.

Description

Heat Source System

[0001] The present invention relates to a heat source system equipped with a plurality of heat source devices for air conditioning and temperature regulation, and in particular to control of the number of operating heat source devices including variable speed turbo heat source devices such as variable speed turbo chillers and variable speed turbo heat pumps.

[0002] Typically, heat source machines are equipped with a function to adjust their output, increasing or decreasing the output in accordance with changes in load, thereby controlling the temperature of the heat transfer medium, such as chilled water, to fall within a predetermined range. However, heat source machines generally have an appropriate load, and when there are multiple heat source machines, it is necessary to maintain the load of each heat source machine within an appropriate range by controlling the number of operating heat source machines according to the total load. Furthermore, if all heat source machines were to operate all the time, the operating time of each heat source machine would be unnecessarily long, maintenance would increase, and power for auxiliary equipment (pumps, fans, etc.) would be wasted, which is undesirable from an energy conservation perspective.

[0003] Therefore, in a heat source system with multiple heat source machines, in addition to controlling the output of each machine, it is necessary to appropriately switch the number of machines in operation according to changes in the load. While switching the number of machines in operation is often done manually, devices that perform this automatically, such as a device for controlling the number of machines in operation, are becoming increasingly common.

[0004] A wide variety of methods have been proposed and are in use for controlling the number of operating units. Typical methods for controlling the number of operating units are as follows. For convenience, the following explanation uses a chilled water (cooling) system as an example, but the same principle applies to heating systems, brine (a sub-zero cold source using antifreeze), and other systems. The names of each control method are given for convenience of explanation and are not universal names.

[0005] (Optimal control method) The optimal control method calculates the power consumption and CO2 according to the number of operating units based on the operating conditions and load state of each heat source unit. ２This method calculates various evaluation indices, such as emissions, and uses these to estimate whether the number of operating units is optimal. It is highly effective in energy conservation, as it can optimize not only the number of operating units but also various other parameters, such as the flow rate of chilled water and cooling water. On the other hand, the optimal control method requires a large amount of information on the characteristics of the heat source equipment, auxiliary equipment (pumps and fans), and facility piping (pressure loss), and collecting and setting this data takes time and money. In addition, the calculation load is high and the cost of equipment is high, and the number of operating units may not be optimal if the characteristics of the heat source equipment change due to external factors such as contamination of the heat source equipment, making it difficult to adopt the optimal control method, especially for small-scale sites.

[0006] (Temperature-based Method) The temperature-based method monitors the outlet temperature of chilled water from each heat source unit, or the temperature after the chilled water from multiple heat source units is combined. If this temperature exceeds an upper reference value, the number of operating units is increased, and if it falls below a lower reference value, the number of operating units is decreased. Generally, heat source units adjust their cooling capacity so that the chilled water outlet temperature reaches a set target temperature. If the load exceeds the maximum cooling capacity of the heat source unit, the chilled water cannot be cooled to the target temperature, and the chilled water outlet temperature exceeds the target temperature. On the other hand, if the load falls below the minimum cooling capacity of the heat source unit, excessive cooling occurs, and the chilled water temperature falls below the target temperature. Therefore, this temperature-based method detects fluctuations in the chilled water outlet temperature and increases or decreases the number of operating units to optimize the total cooling capacity.

[0007] This temperature reference method is the simplest method, but because it cannot determine whether the number of operating units is excessive or insufficient until the chilled water temperature deviates from the target temperature, it can only be used at sites where a certain degree of deviation in chilled water temperature is tolerated.In addition, because chilled water temperature is prone to fluctuations due to sudden increases or decreases in load, false detection can lead to unnecessary increases or decreases in the number of operating units, and the fluctuations in chilled water temperature when the number of operating units increases or decreases can themselves have an effect, causing instability by repeatedly increasing and decreasing the number of operating units.

[0008] (Output standard method) The output standard method calculates the refrigeration output of each heat source unit, and increases the number of operating units when this exceeds the upper limit, and decreases the number when it falls below the lower limit. Because the number of operating units is controlled based on the refrigeration output of each heat source unit, the number of operating units can be increased or decreased before the chilled water outlet temperature deviates, and fluctuations in the chilled water temperature are also small.

[0009] However, the operating conditions of the heat source equipment can sometimes prevent proper control of the number of operating units. In other words, the cooling capacity of a heat source equipment generally varies depending on the temperature of the cooling medium (cooling water for water-cooled equipment, or outdoor air temperature for air-cooled equipment) and the degree of contamination of the heat exchanger. For this reason, the heat source equipment may demonstrate a cooling capacity greater than its rated capacity (increased cooling capacity). Conversely, if contamination accumulates in the heat exchanger or there is a minor malfunction, the maximum cooling capacity may fall short of the rated capacity (decreased cooling capacity). In this case, the number of operating units may be increased even when there is no actual need to increase the number of operating units due to increased cooling capacity. On the other hand, a decrease in cooling capacity may prevent the refrigeration output from reaching the upper limit standard value, resulting in a situation where the number of operating units cannot be increased even when it should be. Furthermore, because refrigeration output is calculated by measuring the chilled water flow rate, equipment costs tend to be high.

[0010] (Control valve opening method) In heat source equipment with a control valve, such as an absorption chiller / heater with a gas control valve, the number of operating units is increased when the opening of the control valve exceeds the upper reference value, and decreased when it falls below the lower reference value. In heat source equipment driven by fuel or steam, such as an absorption chiller / heater or absorption refrigeration unit, the heat source output is controlled by adjusting the fuel (gas control valve) or the amount of steam (steam valve). When the opening of the control valve is at its maximum, the heat source equipment will exhibit the maximum cooling capacity under the operating conditions, and when the opening of the control valve is at its minimum, it will exhibit the minimum cooling capacity. Therefore, the number of operating units can be controlled using the opening of the control valve.

[0011] The advantage of this method is that it allows for reliable adjustments in the number of operating units. In other words, even under conditions where capacity is increasing or decreasing due to factors such as cooling water temperature or contamination, if the load is high the metering valve will always increase to its maximum opening, and if the load is low it will be reduced to its minimum opening. These are also the conditions under which it is actually necessary to increase or decrease the number of operating units. Therefore, when the maximum or minimum capacity of the heat source equipment increases or decreases due to external conditions, there is no unintended increase or decrease in the number of operating units, and the number of operating units can be increased or decreased when necessary, making this a desirable method in that respect.

[0012] However, this metering valve opening method can only be used with heat source equipment that uses a single metering valve to increase or decrease refrigeration capacity.For example, in the case of a fixed-speed centrifugal chiller, the opening of the compressor's suction guide vanes can be regarded as the metering valve opening and similar control can be performed, but in the case of a variable-speed centrifugal chiller, there are two parameters, the compressor rotational speed and the opening of the compressor's suction guide vanes, and this method cannot be used.

[0013] JP 2012-52719 A

[0014] As mentioned above, there are various control methods for controlling the number of operating units, each with its own advantages and disadvantages. However, if control stability (reliability) is a priority, the metering valve position control method is preferable. However, with variable-speed centrifugal chillers, there are two control items—the suction guide vane opening and the compressor rotational speed—which makes it difficult to apply the metering valve position control method. For this reason, when using variable-speed centrifugal chillers, other methods must be used. In this case, to ensure reliability, it is possible to combine two or more control methods, such as using a capacity-based control method while also using a temperature-based control method as a backup. However, even with this combination method, drawbacks remain, such as increasing the number of operating units when it is not actually necessary, or unintentional deviation of the chilled water temperature from the target temperature.

[0015] Therefore, the present invention provides a heat source system that can appropriately control the number of operating units by using a new index that indicates the load of a variable speed turbo heat source unit such as a variable speed turbo chiller.

[0016] In one aspect, a heat source system for temperature regulation is provided, comprising a plurality of heat source machines including a variable speed turbo heat source machine, and an operating unit number control device that controls the number of operating units of the plurality of heat source machines, wherein the variable speed turbo heat source machine comprises a compressor that compresses refrigerant gas and an inverter that varies the rotational speed of the compressor, and the compressor comprises suction guide vanes that adjust the suction flow rate of refrigerant gas into the compressor, and the operating unit number control device calculates a load index value of the variable speed turbo heat source machine by multiplying the relative value of the opening of the suction guide vane by the relative value of the rotational speed of the compressor, and is configured to increase the number of operating heat source machines when the load index value exceeds a first reference value, and to decrease the number of operating heat source machines when the load index value falls below a second reference value.

[0017] The load index value accurately indicates the load of a variable-speed turbo heat source unit, which has two control parameters: the suction guide vane opening and the compressor rotation speed. Therefore, the operating unit number control device can appropriately control the number of operating units based on the load index value. The calculation formula for the load index value is simple, and controlling the number of operating units using the load index value is not complicated. This allows the technology of the present invention to be retrofitted to many sites, including existing units. Even if the cooling or heating capacity of a heat source unit increases or decreases due to operating conditions or machine contamination, the operating unit number control device can reliably control the number of operating units based on the load index value. When cooling or heating capacity increases, the heat source unit can be operated at or above its rated thermal output, reducing the number of operating units and the increase in operating time, thereby reducing the frequency of maintenance. Even in heat source systems that include different types of heat source units, such as absorption chillers, fixed-speed turbo chillers, and positive displacement compression chillers, in addition to variable-speed turbo heat source units, the operating unit number control device can use the load index value to control the number of operating units of these multiple heat source units.

[0018] In one aspect, the control device for the number of operating units is configured to increase the number of operating heat source machines when the average value of the load index values ​​exceeds a first reference value, and to decrease the number of operating heat source machines when the average value of the load index values ​​falls below a second reference value. The control device for the number of operating units can perform efficient control of the number of operating units based on the average operating state indicated by the load index values. In one aspect, the control device for the number of operating units is configured to increase the number of operating heat source machines when the maximum value of the load index values ​​exceeds a first reference value, and to decrease the number of operating heat source machines when the minimum value of the load index values ​​falls below a second reference value. The control device for the number of operating units can perform stable control of the number of operating units based on the minimum or maximum value of the load index values. In one aspect, the relative value of the opening degree of the suction guide vane is calculated by the following equation: Relative value of the opening degree of the suction guide vane=(current opening degree of the suction guide vane−minimum opening degree of the suction guide vane) / (maximum opening degree of the suction guide vane−minimum opening degree of the suction guide vane), and the relative value of the rotational speed of the compressor is calculated by the following equation: Relative value of the rotational speed of the compressor=(current rotational speed of the compressor−minimum rotational speed of the compressor) / (maximum rotational speed of the compressor−minimum rotational speed of the compressor).

[0019] The load index value accurately indicates the load of a variable-speed turbo heat source unit, which has two control parameters: the suction guide vane opening and the compressor rotation speed. Therefore, the operating unit number control device can appropriately control the number of operating units based on the load index value. The calculation formula for the load index value is simple, and controlling the number of operating units using the load index value is not complicated. This allows the technology of the present invention to be retrofitted to many sites, including existing units. Even if the cooling or heating capacity of a heat source unit increases or decreases due to operating conditions or machine contamination, the operating unit number control device can reliably control the number of operating units based on the load index value. When cooling or heating capacity increases, the heat source unit can be operated at or above its rated thermal output, reducing the number of operating units and the increase in operating time, thereby reducing the frequency of maintenance. Even in heat source systems that include different types of heat source units, such as absorption chillers, fixed-speed turbo chillers, and positive displacement compression chillers, in addition to variable-speed turbo heat source units, the operating unit number control device can use the load index value to control the number of operating units of these multiple heat source units.

[0020] Fig. 4 is a schematic diagram showing an embodiment of a heat source system for temperature regulation. Fig. 5 is a schematic diagram showing an embodiment of a variable speed turbo chiller. Fig. 6 is a schematic diagram showing an embodiment of an absorption chiller / heater. Fig. 7 is a graph showing an example of changes in the opening degree and rotation speed of an inlet guide vane with respect to refrigeration output when the cooling water temperature is high and when the cooling water temperature is low. Fig. 8 is a graph showing the graph of Fig. 4 in another form.

[0021] Embodiments of the present invention will now be described with reference to the drawings. Fig. 1 is a schematic diagram showing one embodiment of a heat source system for temperature regulation. The heat source system shown in Fig. 1 includes a plurality of heat source units 1 and 2, including three variable speed centrifugal chillers 1 and two absorption chiller-heaters 2, and an operating unit number control device 3 that controls the number of operating units of the plurality of heat source units 1 and 2. The heat source units 1 and 2 include heat source unit control units 5 and 6, which are connected to the operating unit number control device 3 via a communication line 8.

[0022] Each variable speed turbo chiller 1 includes a compressor 11 and an inverter 12 that varies the rotation speed of the compressor 11. The variable speed turbo chiller 1 is an example of a variable speed turbo heat source machine. Another example of a variable speed turbo heat source machine is a variable speed turbo heat pump. The multiple heat source machines included in the heat source system may include a variable speed turbo heat pump instead of or in addition to the variable speed turbo chillers. Furthermore, the heat source system may include an absorption chiller instead of or in addition to the absorption chiller-heater machine 2. The number of variable speed turbo chillers 1 and the number of absorption chiller-heater machines 2 are not limited to those in the embodiment shown in FIG. 1 .

[0023] The control device for the number of operating vehicles 3 includes a storage device 3a in which a program is stored and an arithmetic device 3b that executes calculations in accordance with instructions included in the program. The control device for the number of operating vehicles 3 is composed of at least one computer. The storage device 3a includes a main storage device such as a random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) or a solid state drive (SSD). Examples of the arithmetic device 3b include a central processing unit (CPU), a graphic processing unit (GPU), a programmable logic controller (PLC), and a field programmable gate array (FPGA). However, the specific configuration of the control device for the number of operating vehicles 3 is not limited to these examples.

[0024] 2 is a schematic diagram showing one embodiment of a variable speed turbo chiller 1. The variable speed turbo chiller 1 includes a compressor 11 that compresses refrigerant gas, a condenser 15 that condenses the compressed refrigerant gas to produce refrigerant liquid, an evaporator 18 that evaporates the refrigerant liquid to produce refrigerant gas, an inverter 12 that varies the rotation speed of the compressor 11, and a heat source unit controller 5 that controls the refrigeration output of the variable speed turbo chiller 1.

[0025] The suction port of the compressor 11 is connected to the evaporator 18 via refrigerant piping 14A. The discharge port of the compressor 11 is connected to the condenser 15 via refrigerant piping 14B. An expansion valve 20 is attached to refrigerant piping 14C extending from the condenser 15 to the evaporator 18. The expansion valve 20 has an adjustable opening and is implemented, for example, by a variable opening motor-operated valve. To improve efficiency, variable speed centrifugal chillers may be equipped with a subcooler (subcooler) that subcools the refrigerant liquid condensed in the condenser, or an economizer that lowers the temperature by vaporizing part of the refrigerant liquid. To compress the refrigerant evaporated in the intercooler, some compressors have an intermediate suction port or two compressors are combined to perform two-stage compression. In any case, these can be treated in the same way as the variable speed centrifugal chiller 1 of this embodiment.

[0026] The compressor 11 includes an impeller 21 and an electric motor 23 that rotates the impeller 21. The impeller 21 may be a single-stage impeller or a multi-stage impeller. The inverter 12 is connected to the electric motor 23 and supplies variable frequency power to the electric motor 23, thereby changing the rotational speed of the electric motor 23 and the impeller 21 (i.e., the rotational speed of the compressor 11).

[0027] Suction guide vanes 16 are arranged at the suction port of the compressor 11 to adjust the suction flow rate of refrigerant gas into the compressor 11. The suction guide vanes 16 are located on the suction side of the impeller 21. The suction guide vanes 16 are arranged radially. The suction guide vanes 16 are rotated synchronously around their own axes by a predetermined angle by a vane actuator 25, thereby changing the opening degree (angle) of the suction guide vanes 16. Refrigerant gas sent from the evaporator 18 passes through the suction guide vanes 16 and is then pressurized by the rotating impeller 21. The refrigerant gas pressurized by the compressor 11 is sent to the condenser 15 through the refrigerant piping 14B.

[0028] The inverter 12 and the vane actuator 25 are electrically connected to the heat source machine control unit 5, and the operation of the inverter 12 and the vane actuator 25, i.e., the rotational speed of the compressor 11 and the opening degree of the suction guide vane 16, are controlled by the heat source machine control unit 5.

[0029] The evaporator 18 produces a refrigerating effect by evaporating the refrigerant liquid by removing heat from cold water (a fluid to be cooled). The compressor 11 compresses the refrigerant gas produced in the evaporator 18, and the condenser 15 cools and condenses the compressed refrigerant gas with cooling water (a cooling fluid) to produce refrigerant liquid. The refrigerant liquid is decompressed by passing through an expansion valve 20. The decompressed refrigerant liquid is sent to the evaporator 18.

[0030] FIG. 3 is a schematic diagram showing one embodiment of the absorption chiller / heater 2. As shown in FIG. 3, the absorption chiller / heater 2 includes a regenerator 31, a condenser 32, an evaporator 33, and an absorber 34. The absorption chiller / heater 2 is configured to generate chilled water by circulating a refrigerant with a solution (absorption liquid) while undergoing a phase change, thereby transferring heat. In this embodiment, an aqueous LiBr solution is used as the solution, and water (H ２ However, the present invention is not limited to this, and other combinations of refrigerants and solutions (absorption liquids) may also be used.

[0031] A partition wall 36 is provided between the regenerator 31 and the condenser 32, and the condenser 32 and the regenerator 31 communicate with each other above the partition wall 36. In one embodiment, the regenerator 31 and the condenser 32 may both be formed in a single can body as a shell-and-tube type.

[0032] The regenerator 31 includes a burner 41 that burns gas supplied from a gas line 40, and a gas control valve 43 that serves as a metering valve for adjusting the flow rate of gas supplied to the burner 41 through the gas line 40. The solution is transferred from the absorber 34 to the regenerator 31 through a diluted solution transfer pipe 45. The gas combusted by the burner 41 forms a flame, and the heat of the flame evaporates the refrigerant contained in the solution in the regenerator 31, generating refrigerant gas. As a result, the solution is concentrated in the regenerator 31. The concentrated solution is transferred to the absorber 34 through a solution transfer pipe 46. The refrigerant gas flows into the condenser 32. The gas control valve 43 is connected to the heat source machine control unit 6, and the operation of the gas control valve 43, i.e., the intensity of the flame formed by the burner 41, is controlled by the heat source machine control unit 6.

[0033] The refrigeration output of the absorption chiller-heater 2 is changed by the aperture of a gas control valve 43, which serves as a metering valve for adjusting the flow rate of gas supplied to the burner 41. That is, as the aperture of the gas control valve 43 increases, the refrigeration output of the absorption chiller-heater 2 increases, and as the aperture of the gas control valve 43 decreases, the refrigeration output of the absorption chiller-heater 2 decreases.

[0034] In one embodiment, the regenerator 31 may include a heating pipe through which a heating fluid such as steam flows, instead of the burner 41. In this configuration, the refrigerant contained in the solution in the regenerator 31 is heated by the heating fluid in the heating pipe and evaporates to become a refrigerant gas. The flow rate of the heating fluid flowing through the heating pipe is regulated by a heating fluid flow control valve serving as a metering valve connected to the heating pipe. In other words, the refrigeration output of the absorption chiller-heater is changed by the aperture of the heating fluid flow control valve serving as a metering valve. Note that there are also so-called double-effect and triple-effect absorption chiller-heaters that reheat the absorption solution with refrigerant vapor evaporated in the regenerator, but these generally have only one metering valve and may be treated in the same way as the absorption chiller-heater 2 of this embodiment.

[0035] The condenser 32 is configured to condense the refrigerant gas that flows in from the regenerator 31. The condenser 32 is provided with a condenser cooling water pipe 47 through which cooling water flows. The condenser cooling water pipe 47 is arranged inside the condenser 32. One end of the condenser cooling water pipe 47 is connected to an absorber cooling water pipe 50 in the absorber 34 via a pipe 48. The refrigerant gas that flows in from the regenerator 31 is condensed by being cooled by the cooling water flowing through the condenser cooling water pipe 47. The condensed refrigerant is supplied from the condenser 32 to the evaporator 33 through a refrigerant supply pipe 51.

[0036] A partition wall 53 is provided between the evaporator 33 and the absorber 34, and the evaporator 33 and the absorber 34 communicate with each other above the partition wall 53. In one embodiment, the evaporator 33 and the absorber 34 may both be formed in a single can body as a shell-and-tube type.

[0037] The evaporator 33 is configured to evaporate the refrigerant condensed in the condenser 32 using cold water to cool the cold water. The evaporator 33 is equipped with a cold water pipe 62 through which cold water flows, and a refrigerant spray nozzle 63 that sprays the refrigerant toward the cold water pipe 62. One end of a refrigerant transfer pipe 65 is connected to the bottom of the evaporator 33, and the other end of the refrigerant transfer pipe 65 is connected to the refrigerant spray nozzle 63. A refrigerant pump 66 is disposed in the refrigerant transfer pipe 65 to pressure-feed the refrigerant through the refrigerant transfer pipe 65 to the refrigerant spray nozzle 63.

[0038] The refrigerant sprayed from the refrigerant spray nozzles 63 comes into contact with the cold water pipes 62 through which cold water flows and evaporates. The evaporator 33 cools the cold water flowing through the cold water pipes 62 by the heat of vaporization generated when the refrigerant evaporates. The refrigerant gas generated in the evaporator 33 flows into the absorber 34 from above the partition wall 53. The refrigerant remaining in the evaporator 33 without evaporating is stored in the bottom of the evaporator 33.

[0039] The absorber 34 is equipped with an absorber cooling water pipe 50 through which cooling water flows, and a solution spray nozzle 71 that sprays a solution toward the absorber cooling water pipe 50. The absorber cooling water pipe 50 is connected to the condenser cooling water pipe 47 of the condenser 32 via a pipe 48. The cooling water flows through the absorber cooling water pipe 50 and then flows to the condenser cooling water pipe 47 via the pipe 48. The solution spray nozzle 71 is configured to spray the concentrated solution produced by the regenerator 31. The concentrated solution is diluted by absorbing the refrigerant gas that flows in from the evaporator 33. The diluted solution is stored in the bottom of the absorber 34.

[0040] A dilute solution pump 74 is disposed in the dilute solution transfer pipe 45, which pumps the diluted solution to the regenerator 31. The diluted solution is transferred by the dilute solution pump 74 through the dilute solution transfer pipe 45 to the regenerator 61. In this way, chilled water is produced while the refrigerant circulates. When heating is performed with the absorption chiller / heater, a switching valve (not shown) in a communication pipe that sends refrigerant vapor generated in the regenerator to the evaporator is opened, so that the refrigerant vapor is sent to the evaporator, and the condensation heat is used to heat chilled water (hot water during heating). The condensed refrigerant liquid passes through a dilution valve (not shown) and returns to the absorber.

[0041] 1 includes an absorption chiller / heater 2, but may include an absorption chiller instead of or in addition to the absorption chiller / heater 2. The configuration of the absorption chiller is basically the same as that of the absorption chiller / heater 2, except that it does not have the aforementioned connecting pipe used during heating.

[0042] Next, the operation of the operating units number control device 3 will be described. The operating units number control device 3 is configured to control the number of operating heat source units 1 and 2 of the heat source system shown in Fig. 1 based on a load index value described below. More specifically, the operating units number control device 3 is configured to receive from the heat source unit control unit 5 of one operating variable speed centrifugal chiller 1 of the three variable speed centrifugal chillers 1 in the heat source system shown in Fig. 1 the opening value of the suction guide vanes 16 of that variable speed centrifugal chiller 1 and the rotational speed value of the compressor 11 of that variable speed centrifugal chiller 1, calculate the relative values ​​of the opening value of the suction guide vanes 16 and the relative value of the rotational speed of the compressor 11, and calculate the load index value of the variable speed centrifugal chiller 1 by multiplying the relative value of the opening value of the suction guide vanes 16 by the relative value of the rotational speed of the compressor 11. Furthermore, the number-of-operating-units control device 3 is configured to increase the number of operating heat source machines when the load index value exceeds a first reference value, and to decrease the number of operating heat source machines when the load index value falls below a second reference value. The first reference value is a value greater than the second reference value.

[0043] The load index value is expressed by the following formula: Load index value=Relative value of the opening degree of the suction guide vane 16×Relative value of the rotation speed of the compressor 11

[0044] The relative value of the opening of the suction guide vane 16 and the relative value of the rotational speed of the compressor 11 are expressed by the following equations: Relative value of the opening of the suction guide vane 16=(current opening of the suction guide vane 16-minimum opening of the suction guide vane 16) / (maximum opening of the suction guide vane 16-minimum opening of the suction guide vane 16) Relative value of the rotational speed of the compressor 11=(current rotational speed of the compressor 11-minimum rotational speed of the compressor 11) / (maximum rotational speed of the compressor 11-minimum rotational speed of the compressor 11)

[0045] The rotation speed (including the maximum rotation speed and the minimum rotation speed) corresponds to the rotation speed of the compressor 11, the rotation speed of the electric motor 23, or the drive frequency of the electric motor 23. The minimum rotation speed of the compressor 11 is the minimum rotation speed determined by electrical or mechanical limitations of the electric motor 23, the inverter 12, or the compressor 11, and is usually 20 to 40% of the rated rotation speed. In calculating the load index value, the minimum rotation speed of the compressor 11 may be set to 0 for convenience.

[0046] The opening of the suction guide vanes 16 can be expressed as an angle (degrees) from the fully closed position, and is handled in this manner in the present embodiment. In this case, the maximum opening is generally the angle at which the compression capacity of the compressor is maximized, and is approximately 90 to 120 degrees. In practice, the minimum opening is often not 0 degrees to avoid operating the compressor 11 in a shutoff state, but for convenience, the minimum opening of the suction guide vanes 16 may be set to 0 degrees.

[0047] Controlling the number of operating units based on the load index value is described in detail below. The variable speed centrifugal chiller 1 adjusts the refrigeration output of the variable speed centrifugal chiller 1 by changing the opening of the suction guide vanes 16 at the inlet of the compressor 11 and the rotational speed of the compressor 11. More specifically, the heat source unit control unit 5 first adjusts the refrigeration output by increasing or decreasing the rotational speed of the compressor 11, and then further adjusts the refrigeration output by changing the opening of the suction guide vanes 16. Generally, increasing the rotational speed of a centrifugal chiller increases the refrigeration output, and decreasing it decreases the refrigeration output. When adjusting the refrigeration output using the rotational speed, the opening of the suction guide vanes 16 is set to its maximum.

[0048] In variable-speed turbo chiller 1, reducing the rotational speed of the compressor 11 too much can cause surging, so the rotational speed cannot be reduced below a certain lower limit. This lower limit is determined by the minimum work required to increase the refrigerant pressure from the pressure in the evaporator 18 to the pressure in the condenser 15. Therefore, the lower limit of the rotational speed of the compressor 11 is referred to here as the "work rotation speed." The work rotation speed is determined by calculation based on the pressure in the condenser 15 or the pressure in the condenser 15 and the pressure in the evaporator 18. Because the work rotation speed varies depending on the pressure in the condenser 15, i.e., the cooling water temperature, the range in which the refrigeration output can be changed by the rotational speed of the compressor 11 alone varies depending on the cooling water temperature. The work rotation speed may also be determined by calculation based on the cooling water temperature.

[0049] When the rotation speed of the compressor 11 decreases and reaches the workpiece rotation speed, the heat source machine control unit 5 then adjusts the refrigeration output by increasing or decreasing the opening of the suction guide vanes 16. At this time, the rotation speed of the compressor 11 is maintained at the workpiece rotation speed. The reason for this is that changing the rotation speed often results in less loss than changing the opening of the suction guide vanes 16, and therefore it is highly efficient to reduce the rotation speed as much as possible and make up for the shortfall by controlling the opening of the suction guide vanes 16.

[0050] The suction guide vanes 16 swirl the refrigerant gas sucked into the compressor 11, thereby reducing the relative speed between the refrigerant gas and the impeller of the compressor 11, thereby changing the characteristics of the compressor 11, reducing the compressed air volume and lowering the refrigeration output. The suction guide vanes 16 can change the compressed air volume without significantly reducing the efficiency of the compressor 11.

[0051] Next, we will explain how the behavior of the variable speed centrifugal chiller 1 changes when the cooling water temperature drops. First, when the cooling water temperature drops, the pressure inside the condenser 15 decreases, which reduces the head of the compressor 11, increasing the air volume and refrigeration output. Generally, the rated output (100% output) of a chiller is set when the cooling water temperature is high, so when the cooling water temperature drops, the maximum output of the variable speed centrifugal chiller 1 exceeds 100% of the rated output. Meanwhile, because the workpiece rotation speed decreases, the range over which refrigeration output can be controlled by rotation speed becomes wider.

[0052] On the other hand, the lowering of the head of the compressor 11 increases the minimum refrigeration output, further narrowing the range in which the refrigeration output can be controlled by the opening of the suction guide vanes 16. Although the correlation between the rotation speed of the compressor 11 and the opening of the suction guide vanes 16 and the refrigeration output is not linear, there is a positive correlation, and therefore the direction of increase or decrease in the rotation speed of the compressor 11 and the opening of the suction guide vanes 16 coincides with the direction of increase or decrease in the refrigeration output.

[0053] 4 is a graph showing an example of changes in the opening degree of the suction guide vane 16 and the rotational speed of the compressor 11 with respect to the refrigeration output when the cooling water temperature is high and when the cooling water temperature is low. In FIG. 4, the horizontal axis represents the relative value (%) of the refrigeration output when the rated refrigeration output is set to 100%, and the vertical axis represents the relative value (%) of the opening degree of the suction guide vane 16 and the relative value (%) of the rotational speed of the compressor 11.

[0054] Figure 5 is a graph that expresses the graph of Figure 4 in a different form, and schematically shows how the opening of the suction guide vanes 16 and the rotation speed of the compressor 11 are controlled within a range of refrigeration output from minimum to maximum when the cooling water temperature is high and when the cooling water temperature is low. In Figure 5, the refrigeration output when the refrigeration capacity is increased when the cooling water temperature is low is defined as "maximum refrigeration output," and the refrigeration output is expressed as a relative value to this. In Figures 4 and 5, "high temperature" and "low temperature" mean that the cooling water temperature is relatively high or low within the operable range of the heat source machine, and do not mean that the temperature is absolutely high or low.

[0055] When the refrigeration output is low, the refrigeration output is controlled by the opening of the suction guide vanes 16, and when the refrigeration output is high, the refrigeration output is controlled by the rotational speed of the compressor 11. Hereinafter, control by the opening of the suction guide vanes 16 will be referred to as vane opening control, and control by the rotational speed of the compressor 11 will be referred to as rotational speed control.

[0056] During vane opening control, the rotational speed of the compressor 11 is maintained at the work rotational speed, and the opening of the suction guide vanes 16 varies within a range of 0 to 100%. During rotational speed control, the opening of the suction guide vanes 16 is maintained at 100%, and the rotational speed of the compressor 11 varies within a range from the work rotational speed to 100% rotational speed.

[0057] In this embodiment, the heat source machine control unit 5 of the variable speed centrifugal chiller 1 calculates the workpiece rotation speed based on the pressure ratio between the condenser 15 and the evaporator 18 and a table stored in a storage device (not shown) of the heat source machine control unit 5. The rotation speed of the compressor 11 is then varied between the workpiece rotation speed and the maximum rotation speed, controlling the rotation speed so that the outlet chilled water temperature of the chiller 1 reaches a set target value. At this time, the opening of the suction guide vanes 16 is set to the maximum opening (100%) (rotational speed control mode). The table is created as follows: Surging is intentionally induced multiple times while varying the rotation speed of the compressor 11 during actual operation of the variable speed centrifugal chiller 1. Multiple observed values ​​of the rotation speed of the compressor 11 when surging occurs and the ratio of the pressure in the condenser 15 to the pressure in the evaporator 18 (hereinafter referred to as the pressure ratio) are obtained, and a table showing the correlation between the rotation speed of the compressor 11 and the pressure ratio when surging occurs is created. The table created in this manner is stored in a storage device (not shown) of the heat source machine control unit 5.

[0058] If the refrigeration output does not decrease to the required level even when the rotational speed of the compressor 11 is reduced to the work rotational speed, the heat source machine control unit 5 changes the opening of the suction guide vane 16 within a range from the maximum opening to the minimum opening while maintaining the rotational speed of the compressor 11 at the work rotational speed, thereby controlling the outlet cold water temperature of the heat source machine 1 to the target value (vane opening control mode).

[0059] Here, the load index value will be explained. In the rotational speed control range, the opening of the suction guide vanes 16 is always 100%. Therefore, the opening of the suction guide vanes 16 alone cannot be used as the load index value. Meanwhile, during vane opening control, the rotational speed of the compressor 11 is constant at the workpiece rotational speed. However, the rotational speed does not change from 0 to 100%, but rather changes within the range from the workpiece rotational speed to 100% rotational speed.

[0060] Therefore, during rotation speed control, the rotation speed (%) of the compressor 11 is used as the load index value, and during vane opening control, the load index value is the work rotation speed (%) multiplied by the opening (%) of the suction guide vane 16. The opening of the suction guide vane 16 is 0 to 100%. Since the work rotation speed during vane opening control is the actual rotation speed, the actual rotation speed, not the work rotation speed, can be used to calculate the load index value. In this way, since the opening of the suction guide vane 16 is always 100% during rotation speed control, the mathematical formula is the same. In other words, by always using the above formula, the load index value can be calculated without changing the calculation method for vane opening control and rotation speed control. This indicates that the formula for calculating the load index value is free of discontinuities and has favorable characteristics as a control index.

[0061] Below are examples of calculation of the load index value for several specific cases. (1) In rotation speed control mode (when cooling water temperature is high) When the work rotation speed is 90%, the relative value of the rotation speed is 95%, and the relative value of the opening of the suction guide vane 16 is 100%, the load index value = 100% x 95% = 95% (2) In rotation speed control mode (when cooling water temperature is low) When the work rotation speed is 70%, the relative value of the rotation speed is 80%, and the relative value of the opening of the suction guide vane 16 is 100%, the load index value = 100% x 80% = 80% (3) When controlling the opening of the suction guide vane 16 (when cooling water temperature is high) When the work rotation speed is 90%, the relative value of the rotation speed is 90%, and the relative value of the opening of the suction guide vane 16 is 80%, the load index value = 80% x 90% = 72% (4) When controlling the opening of the suction guide vane 16 (when cooling water temperature is low) When the work rotation speed is 70%, the relative value of the rotation speed is 70%, and the relative value of the opening of the suction guide vane 16 is 60%, the load index value = 70% x 60% = 42%

[0062] In the above cases (1) and (2), the rotational speed control mode is in effect, so the relative value of the rotational speed of the compressor 11 is equal to or greater than the work rotational speed, and the relative value of the opening of the suction guide vane 16 is 100%. In the above cases (3) and (4), the vane opening control mode is in effect, so the relative value of the rotational speed of the compressor 11 is equal to the work rotational speed, and the opening of the suction guide vane 16 is between 0 and 100%.

[0063] In the heat source system shown in FIG. 1 , when only variable speed centrifugal chiller 1 is operating, the number of operating units control device 3 increases the number of operating units if the load index value of variable speed centrifugal chiller 1 during operation exceeds a first reference value, and decreases the number of operating units if the load index value falls below a second reference value.

[0064] In one embodiment, the control device for number of operating units 3 increases the number of operating units when the average value of the load index values ​​of variable speed centrifugal chillers 1 during operation exceeds a first reference value, and decreases the number of operating units when the average value of the load index values ​​falls below a second reference value. Every time a predetermined time (e.g., 10 seconds) elapses, the control device for number of operating units 3 compares the average value of the load index values ​​within the predetermined time with a first reference value and a second reference value. The first reference value is greater than the second reference value. The control device for number of operating units 3 can efficiently control the number of operating units based on the average operating state indicated by the load index values.

[0065] In another embodiment, the control device for the number of operating units 3 increases the number of operating units when the maximum load index value of the variable speed centrifugal chillers 1 in operation exceeds a first reference value, and decreases the number of operating units when the minimum load index value falls below a second reference value. Every time a predetermined time (e.g., 10 seconds) elapses, the control device for the number of operating units 3 compares the maximum load index value within the predetermined time with the first reference value and compares the minimum load index value within the predetermined time with the second reference value. The first reference value is greater than the second reference value. When the maximum and minimum values ​​are used instead of the average value, the control device for the number of operating units 3 can stably control the number of operating units based on the maximum or minimum load index value even in cases where there is a large variation in the load index values ​​due to differences in capacity between heat source units, for example.

[0066] The absorption chiller-heater 2 controls the aperture of the gas control valve 43 (see FIG. 3 ), which is a metering valve, and adjusts the gas combustion in the burner 41 to adjust the refrigeration output so that the chilled water outlet temperature is the target temperature. If the regenerator 31 shown in FIG. 3 is equipped with a heating pipe through which a heating fluid (e.g., steam) flows instead of the burner 41, the absorption chiller-heater 2 controls the aperture of the heating fluid flow control valve, which is a metering valve, so that the chilled water outlet temperature is the target temperature, and adjusts the refrigeration output by adjusting the flow rate of the heating fluid flowing through the heating pipe with the heating fluid flow control valve. Because the absorption chiller-heater 2 basically controls the refrigeration output only by the aperture of the metering valve (e.g., the gas control valve 43 or the heating fluid flow control valve), it does not have a vane aperture control mode or rotation speed control mode like the variable speed turbo chiller 1.

[0067] The control device for controlling the number of operating units 3 monitors the states of the heat source units 1 and 2 via communication line 8, and can switch the heat source units 1 and 2 between operation and stop, or change their operating states, via communication line 8. The control device for controlling the number of operating units 3 can, for example, limit the heat source units to be operated depending on the season, or change the operation priority. For example, it is possible to operate only the absorption chiller / heater unit 2 in heating mode in winter, and to operate the turbo chiller 1 preferentially in summer, and to operate the absorption chiller / heater unit 2 additionally if the load cannot be fully covered.

[0068] 1 , when the only heat source unit in operation is the absorption chiller-heater unit 2, the control device for number of operating units 3 is configured to control the number of operating heat source units based on the aperture of a metering valve (e.g., gas control valve 43 or a heating fluid flow control valve) of the absorption chiller-heater unit 2. More specifically, when the aperture of the metering valve of an operating absorption chiller-heater unit 2 exceeds a third reference value, the control device for number of operating units 3 increases the number of operating heat source units, and when the aperture of the metering valve falls below a fourth reference value, the control device for number of operating units decreases the number of operating heat source units. The third reference value is a value greater than the fourth reference value.

[0069] In one embodiment, the control device for number of operating units 3 increases the number of operating heat source units when the average value of the apertures of the metering valves of the operating absorption chiller-heaters 2 exceeds a third reference value, and decreases the number of operating heat source units when the average value of the apertures of the metering valves falls below a fourth reference value. The third reference value is a value greater than the fourth reference value. In another embodiment, the control device for number of operating units 3 increases the number of operating heat source units when the maximum value of the apertures of the metering valves of the operating absorption chiller-heaters 2 exceeds the third reference value, and decreases the number of operating heat source units when the minimum value of the apertures of the metering valves falls below the fourth reference value. The third reference value is a value greater than the fourth reference value. Note that the first reference value may be used as the third reference value, and the second reference value may be used as the fourth reference value.

[0070] 1 has an absorption chiller / heater machine 2, but an absorption chiller may be used instead of the absorption chiller / heater machine 2. Even in this case, the control device 3 for controlling the number of operating units can control the number of operating heat source machines based on the aperture of the metering valve (for example, a gas control valve or a heating fluid flow control valve) of the absorption chiller / heater machine in operation, just like the absorption chiller / heater machine 2.

[0071] When the variable speed centrifugal chiller 1 and the absorption chiller / heater unit 2 are operating simultaneously, the control device for the number of operating units 3 treats the load index value of the variable speed centrifugal chiller 1 and the aperture of the metering valve of the absorption chiller / heater unit 2 as equivalent to the load index value of the variable speed centrifugal chiller, and controls the number of operating heat source units. Specifically, the control device for the number of operating units 3 increases the number of operating heat source units when the load index value of the variable speed centrifugal chiller 1 and the maximum value of the aperture of the metering valve of the absorption chiller / heater unit 2 (or the average value of these) exceed a first reference value, and decreases the number of operating heat source units when the load index value of the variable speed centrifugal chiller 1 and the minimum value of the aperture of the metering valve of the absorption chiller / heater unit 2 (or the average value of these) fall below a second reference value. As described above, the load index value relatively indicates the load of the heat source unit, and therefore can also be treated as equivalent to the aperture of the metering valve, etc., in this way.

[0072] In one embodiment, the above-described first reference value, second reference value, third reference value, and fourth reference value may be increased or decreased according to the number of operating heat source units. Specifically, as the number of operating heat source units increases, at least one of the first reference value and the third reference value is increased, and at least one of the second reference value and the fourth reference value is decreased. In this way, by changing the first reference value, second reference value, third reference value, and fourth reference value based on the number of operating heat source units, it is possible to avoid frequent increases and decreases in the number of operating units.

[0073] In the embodiments described so far, the multiple heat source machines included in the heat source system are a combination of a variable speed turbo chiller 1 and an absorption chiller / heater 2, or a combination of a variable speed turbo chiller 1 and an absorption chiller. However, the above-described control of the number of operating units can be applied not only to the above embodiments, but also to heat source systems that include, in addition to the variable speed turbo chiller 1, at least one of a variable speed turbo heat pump, a fixed speed turbo chiller, a fixed speed turbo heat pump, a positive displacement compression chiller, an absorption chiller / heater, and an absorption chiller.

[0074] Depending on the situation, there may be cases where it is desired to prioritize operation of the turbo chiller over the absorption chiller / heater (such as when priority is given to the use of renewable electricity), or conversely, cases where priority is given to operation of the absorption chiller / heater (such as when the power supply and demand is tight and power saving is necessary). In such cases, the following control is performed.

[0075] First, a priority is set for each heat source unit. For example, if it is desired to prioritize operation of a variable speed centrifugal chiller, the priority of the variable speed centrifugal chiller is set to "1" and the priority of the absorption chiller-heater is set to "2." Note that although this is called a priority, it is best to assign the same priority to heat source units of the same type (if there are multiple heat source units with the same priority).

[0076] Here, as described above, if the load index value and the maximum value (or average value) of the regulating valve opening of the operating heat source machines exceed the first reference value, the heat source machine with the highest priority (smallest value) among the stopped heat source machines will be operated. If there are multiple stopped heat source machines with the highest priority, the heat source machine to be operated will be determined based on the shortest operating time, etc., or using a random number, etc.

[0077] Furthermore, if the load index value and minimum (or average) value of the regulating valve opening of the operating heat source machines fall below the second reference value, the heat source machine with the lowest priority (largest numerical value) among the operating heat source machines is stopped. If there are multiple operating heat source machines with the lowest priority, the heat source machine to operate is determined based on the one with the longest operating time, a random number, or the like.

[0078] It is preferable that the combination of operational priorities of the heat source units can be changed all at once by changing the so-called operation mode. For example, in the "power consumption reduction priority" mode, the absorption chiller-heater unit is given a higher priority than the variable speed turbo chiller, and the "CO ２ In the "emission reduction priority" mode, the absorption chiller heater is given a lower priority than the variable speed turbo chiller. ２ This will enable operations to be carried out according to the indicators that are prioritized in the given situation, such as reducing emissions.

[0079] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims.

[0080] The present invention can be used in a heat source system equipped with multiple heat source devices for air conditioning or temperature control, and in particular can be used to control the number of operating heat source devices including variable speed turbo heat source devices such as variable speed turbo chillers and variable speed turbo heat pumps.

[0081] REFRIGERATION SYSTEM 1 Variable speed turbo chiller 2 Absorption chiller / heater 3 Operating unit number control device 5, 6 Heat source unit control unit 8 Communication line 11 Compressor 12 Inverter 14A, 14B, 14C Refrigerant piping 15 Condenser 16 Suction guide vane 18 Evaporator 20 Expansion valve 21 Impeller 23 Electric motor 25 Vane actuator 31 Regenerator 32 Condenser 33 Evaporator 34 Absorber 36 Partition wall 40 Gas line 41 Burner 43 Gas control valve 45 Diluted solution transfer pipe 46 Solution transfer pipe 47 Condenser cooling water pipe 48 Piping 50 Absorber cooling water pipe 51 Refrigerant supply pipe 53 Partition wall 62 Cold water pipe 63 Refrigerant spray nozzle 65 Refrigerant transfer pipe 66 Refrigerant pump 71 Solution spray nozzle 74 Diluted solution pump

Claims

1. A heat source system for temperature regulation comprising: a plurality of heat source units including a variable speed turbo heat source unit; and an operating unit number control device that controls the number of operating heat source units of the plurality of heat source units, wherein the variable speed turbo heat source unit comprises a compressor that compresses refrigerant gas and an inverter that varies the rotational speed of the compressor, and the compressor comprises a suction guide vane that adjusts the suction flow rate of refrigerant gas to the compressor, and the operating unit number control device calculates a load index value of the variable speed turbo heat source unit by multiplying the relative value of the opening of the suction guide vane by the relative value of the rotational speed of the compressor, and is configured to increase the number of operating heat source units when the load index value exceeds a first reference value, and to decrease the number of operating heat source units when the load index value falls below a second reference value.

2. The heat source system described in claim 1, wherein the number of operating units control device is configured to increase the number of operating heat source units when the average value of the load index value exceeds a first reference value, and to decrease the number of operating heat source units when the average value of the load index value falls below a second reference value.

3. The heat source system described in claim 1, wherein the number of operating units control device is configured to increase the number of operating heat source units when the maximum value of the load index value exceeds a first reference value, and to reduce the number of operating heat source units when the minimum value of the load index value falls below a second reference value.

4. The heat source system of claim 1, wherein the relative value of the opening of the suction guide vane is calculated by the following formula: Relative value of the opening of the suction guide vane = (current opening of the suction guide vane - minimum opening of the suction guide vane) / (maximum opening of the suction guide vane - minimum opening of the suction guide vane), and the relative value of the rotational speed of the compressor is calculated by the following formula: Relative value of the rotational speed of the compressor = (current rotational speed of the compressor - minimum rotational speed of the compressor) / (maximum rotational speed of the compressor - minimum rotational speed of the compressor).

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