TURBO REFRIGERATOR, REFRIGERATOR CONTROL DEVICE, TURBO REFRIGERATOR CONTROL METHOD, AND PROGRAM

TECHNICAL FIELD

[0001]The present disclosure relates to a centrifugal chiller, a chiller control device, a control method of a centrifugal chiller, and a program. Priority is claimed on Japanese Patent Application No. 2022-144367 filed on Sep. 12, 2022, the content of which is incorporated herein by reference.

BACKGROUND ART

[0002]PTL 1 discloses a centrifugal chiller including a turbo compressor that compresses a refrigerant gas and a suction capacity control unit that controls a capacity of the refrigerant gas passing through the turbo compressor. In the centrifugal chiller disclosed in PTL 1, when starting the turbo compressor, the suction capacity control unit is set to a target opening degree. The setting of such a suction capacity control unit to the target opening degree is performed when starting the centrifugal chiller in order to cause a refrigerant dissolved in a lubricant in an oil tank of the turbo compressor to foam, and to suppress oil lifting.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

[0004]Meanwhile, in the centrifugal chiller, in a case where a load by the refrigerant gas sucked by the turbo compressor at the time of starting is large, a starting current and a starting time of an electric motor that drives the turbo compressor increase. For this reason, when starting the centrifugal chiller, an opening degree of a vane provided at an inlet for the refrigerant gas in the turbo compressor is reduced to limit suction flow rate of the refrigerant gas.

[0005]However, the flow rate of the refrigerant gas sucked by the turbo compressor at the time of starting can fluctuate depending on a state of the refrigerant such as a density of the refrigerant at the time of starting. For this reason, there is a problem in which the opening degree of the vane initially set does not match the state of the refrigerant gas when starting the turbo compressor, which leads to a starting failure of the turbo compressor.

[0006]The centrifugal chiller disclosed in PTL 1 does not solve such a problem.

[0007]The present disclosure has been devised in order to solve the above problem, and an object thereof is to provide a centrifugal chiller, a chiller control device, a control method of a centrifugal chiller, and a program that can improve startability regardless of a state of a refrigerant gas at the time of starting.

Solution to Problem

[0008]According to an aspect of the present disclosure, in order to solve the above problem, there is provided a centrifugal chiller including a turbo compressor that compresses a refrigerant gas, a vane that is capable of adjusting flow rate of the refrigerant gas sucked by the turbo compressor, a condenser that condenses the refrigerant gas compressed by the turbo compressor by causing the refrigerant gas to release heat through heat exchange, an expansion valve that expands a liquid refrigerant introduced from the condenser, an evaporator that evaporates the liquid refrigerant expanded by the expansion valve by causing the liquid refrigerant to absorb heat through heat exchange, and a chiller control device, in which the chiller control device includes an acquisition unit that acquires at least a state amount of the refrigerant gas when starting the centrifugal chiller, an opening degree determination unit that determines an opening degree of the vane based on the acquired state amount, and an opening degree control unit that controls the opening degree of the vane based on the determined opening degree.

[0009]According to another aspect of the present disclosure, there is provided a chiller control device of a centrifugal chiller including a turbo compressor that compresses a refrigerant gas, a vane that is capable of adjusting flow rate of the refrigerant gas sucked by the turbo compressor, a condenser that condenses the refrigerant gas compressed by the turbo compressor by causing the refrigerant gas to release heat through heat exchange, an expansion valve that expands a liquid refrigerant introduced from the condenser, and an evaporator that evaporates the liquid refrigerant expanded by the expansion valve by causing the liquid refrigerant to absorb heat through heat exchange, the chiller control device including an acquisition unit that acquires at least a state amount of the refrigerant gas when starting the centrifugal chiller, an opening degree determination unit that determines an opening degree of the vane based on the acquired state amount, and an opening degree control unit that controls the opening degree of the vane based on the determined opening degree.

[0010]According to still another aspect of the present disclosure, there is provided a control method of a centrifugal chiller including a turbo compressor that compresses a refrigerant gas, a vane that is capable of adjusting flow rate of the refrigerant gas sucked by the turbo compressor, a condenser that condenses the refrigerant gas compressed by the turbo compressor by causing the refrigerant gas to release heat through heat exchange, an expansion valve that expands a liquid refrigerant introduced from the condenser, and an evaporator that evaporates the liquid refrigerant expanded by the expansion valve by causing the liquid refrigerant to absorb heat through heat exchange, the control method including acquiring at least a state amount of the refrigerant gas when starting the centrifugal chiller, determining an opening degree of the vane based on the acquired state amount, and controlling the opening degree of the vane based on the determined opening degree.

[0011]According to still another aspect of the present disclosure, there is provided a program causing a computer included in a centrifugal chiller, including a turbo compressor that compresses a refrigerant gas, a vane that is capable of adjusting flow rate of the refrigerant gas sucked by the turbo compressor, a condenser that condenses the refrigerant gas compressed by the turbo compressor by causing the refrigerant gas to release heat through heat exchange, an expansion valve that expands a liquid refrigerant introduced from the condenser, and an evaporator that evaporates the liquid refrigerant expanded by the expansion valve by causing the liquid refrigerant to absorb heat through heat exchange, to execute a procedure of acquiring at least a state amount of the refrigerant gas when starting the centrifugal chiller, a procedure of determining an opening degree of the vane based on the acquired state amount, and a procedure of controlling the opening degree of the vane based on the determined opening degree.

Advantageous Effects of Invention

[0012]With the centrifugal chiller, the chiller control device, the control method of a centrifugal chiller, and the program according to the present disclosure, startability can be improved regardless of the state of the refrigerant gas at the time of starting.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a diagram showing an overall configuration of a centrifugal chiller according to an embodiment of the present disclosure.

[0014]FIG. 2 is a block diagram showing a functional configuration of a chiller control device of the centrifugal chiller.

[0015]FIG. 3 is a flowchart showing procedures of a control method of a centrifugal chiller according to the embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0016]Hereinafter, an embodiment for carrying out a centrifugal chiller, a chiller control device, a control method of a centrifugal chiller, and a program according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiment only.

(Overall Configuration of Centrifugal Chiller)

[0017]As shown in FIG. 1, a centrifugal chiller 1 mainly includes a turbo compressor 3 that compresses a refrigerant gas, a condenser 5, an expansion valve 7, an evaporator 9, and a chiller control device 100.

[0018]The condenser 5 condenses a high-temperature and high-pressure gas refrigerant compressed by the turbo compressor 3. The condenser 5 condenses the refrigerant gas compressed by the turbo compressor 3 by causing the refrigerant gas to release heat through heat exchange with cooling water. A heat exchanger such as a shell-and-tube type and a plate type can be given as an example of the condenser 5.

[0019]The expansion valve 7 expands a liquid refrigerant condensed by the condenser 5. The expansion valve 7 is, for example, a motor-driven type, and an opening degree is set to any degree by the chiller control device 100.

[0020]The evaporator 9 evaporates the liquid refrigerant expanded by the expansion valve 7. The evaporator 9 evaporates the liquid refrigerant expanded by the expansion valve 7 by causing the liquid refrigerant to absorb heat through heat exchange with water, such as a cooling target. A heat exchanger such as a shell-and-tube type and a plate type can be given as an example of the evaporator 9.

[0021]The turbo compressor 3 is a centrifugal compressor and is driven by an electric motor 11 of which a rotation speed is controlled by an inverter (not shown). An output of the inverter is controlled by the chiller control device 100. The turbo compressor 3 includes an impeller 3a that rotates around a rotating shaft 3b. Rotational power is transmitted from the electric motor 11 to the rotating shaft 3b via a speed increaser 15. The rotating shaft 3b is supported by a bearing 3c to be rotatable about a central axis of the rotating shaft 3b. The turbo compressor 3 compresses the refrigerant gas sucked into a housing (not shown) of the turbo compressor 3 with the impeller 3a rotating around the rotating shaft 3b and discharges the refrigerant gas to the condenser 5.

[0022]The turbo compressor 3 may have an aspect (for example, an electric motor direct-coupling type) not including the speed increaser 15.

[0023]A refrigerant intake port of the turbo compressor 3 is provided with a vane 13 (so-called inlet guide vane: IGV). The vane 13 can adjust an opening degree of the refrigerant intake port with an opening degree adjustment mechanism 17 including a motor. The flow rate of the refrigerant sucked by the turbo compressor 3 at the refrigerant intake port is adjusted by adjusting an opening degree of the vane 13.

[0024]The chiller control device 100 controls an operation of each unit of the centrifugal chiller 1. In the present embodiment, the chiller control device 100 controls the opening degree of the vane 13 by controlling the opening degree adjustment mechanism 17 when starting the centrifugal chiller 1.

[0025]A pressure sensor 120 is provided on an outlet side of the evaporator 9. The pressure sensor 120 detects a pressure of the refrigerant gas on the outlet side of the evaporator 9. The pressure sensor 120 outputs the detection result of the pressure of the refrigerant gas to the chiller control device 100.

[0026]FIG. 2 is a block diagram showing a functional configuration of the chiller control device of the centrifugal chiller.

[0027]The chiller control device 100 can be configured by using hardware that includes a computer, including a central processing unit (CPU), volatile and non-volatile storage devices, an input/output device, and a communication device, and a peripheral circuit, a peripheral device, and the like of the computer. As shown in FIG. 2, the chiller control device 100 includes an acquisition unit 101, an opening degree determination unit 102, an opening degree control unit 103, and a storage unit 105 as a functional configuration consisting of a combination of the hardware and software such as a program executed by the computer.

[0028]The acquisition unit 101 acquires information necessary for determining an opening degree of the vane 13 necessary for starting the centrifugal chiller 1 (hereinafter, referred to as a required vane opening degree).

[0029]The acquisition unit 101 acquires device information of the turbo compressor 3. Examples of the device information of the turbo compressor 3 include a type of the turbo compressor 3, a type of refrigerant to be used, and a shape of the vane 13.

[0030]The device information of the turbo compressor 3 may be input from the outside into the chiller control device 100 by an operator or may be acquired from an external storage device or the like in which the device information of the turbo compressor 3 is stored.

[0031]In addition, the acquisition unit 101 acquires state information when starting (immediately before starting) the centrifugal chiller 1 as information necessary for determining the required vane opening degree. The acquisition unit 101 acquires at least a state amount of the refrigerant gas as the state information. In the present embodiment, the acquisition unit 101 acquires, as the state amount of refrigerant gas, the pressure of the refrigerant gas sucked by the turbo compressor 3. The acquisition unit 101 acquires the detection result of the pressure of the refrigerant gas on the outlet side of the evaporator 9 detected by the pressure sensor 120 as the pressure of the refrigerant gas sucked by the turbo compressor 3. The acquisition unit 101 may acquire a temperature of the refrigerant gas sucked by the turbo compressor 3 as the state amount of the refrigerant gas.

[0032]Further, the acquisition unit 101 acquires, as the state information, a used rotation speed of the turbo compressor 3 during a steady operation of the centrifugal chiller 1. For example, the used rotation speed may be input from the outside to the chiller control device 100 by the operator, or a value of the used rotation speed that is set in the chiller control device 100 in advance from the outside and that is stored in the storage unit 105 may be acquired when starting the centrifugal chiller 1.

[0033]The storage unit 105 stores the device information, the state information, and the like acquired by the acquisition unit 101.

[0034]The opening degree determination unit 102 determines the required vane opening degree of the vane 13 when starting the centrifugal chiller 1 based on the device information and the state information acquired by the acquisition unit 101.

[0035]The opening degree control unit 103 controls the opening degree of the vane 13 by controlling the opening degree adjustment mechanism 17 based on the required vane opening degree determined by the opening degree determination unit 102.

(Control Method of Centrifugal Chiller)

[0036]FIG. 3 is a flowchart showing procedures of the control method of a centrifugal chiller according to the embodiment of the present disclosure.

[0037]As shown in FIG. 3, when starting the centrifugal chiller 1, first, the acquisition unit 101 acquires the device information of the turbo compressor 3 (step S10). The acquisition unit 101 reads and acquires, as the device information of the turbo compressor 3, for example, a type of the turbo compressor 3, a type of refrigerant to be used, a shape of the vane 13, and the like from the storage unit 105. More specifically, the acquisition unit 101 acquires an allowable before-after differential pressure ΔPsb of the vane 13 set in advance based on the shape or the like of the vane 13. The allowable before-after differential pressure ΔPsb of the vane 13 is an allowable value of a differential pressure between an upstream side and a downstream side of the vane 13 in a suction direction of the refrigerant gas, which is set in advance. In addition, the acquisition unit 101 acquires a correction value K of the allowable before-after differential pressure ΔPsb, which is set in advance according to the type of the turbo compressor 3. In addition, the acquisition unit 101 acquires a function (calculation equation) indicating a correlation between the pressure (or temperature) of the refrigerant and a density ρ of the refrigerant, which is set in advance for each type of refrigerant to be used. This function is obtained by acquiring information of the (saturated) pressure-(saturated) temperature-density of the refrigerant based on a physical property value database of the refrigerant (for example, REFPROP by National Institute of Standards and Technology (NIST)) and creating an approximate equation from the data.

[0038]Next, the acquisition unit 101 acquires the state information when starting (immediately before starting) the centrifugal chiller 1 (step S20). The acquisition unit 101 acquires the detection result of the pressure of the refrigerant gas on the outlet side of the evaporator 9 detected by the pressure sensor 120 as the state information. In addition, the acquisition unit 101 acquires, as the state information, the used rotation speed of the turbo compressor 3 during the steady operation of the centrifugal chiller 1.

[0039]Next, the opening degree determination unit 102 determines the required vane opening degree as the opening degree of the vane 13 when starting the turbo compressor 3 based on the device information acquired in step S10 and the state information acquired in step S20 (step S30). In the present embodiment, this step S30 includes steps S31 to S36 to be described below.

[0040]First, the opening degree determination unit 102 calculates the required vane opening degree of the vane 13, which is necessary when starting the turbo compressor 3 (step S31).

[0041]In order to achieve this, the opening degree determination unit 102 calculates the density ρ of the refrigerant immediately before starting the turbo compressor 3 with a function set in advance, based on the type of refrigerant to be used in the centrifugal chiller 1 acquired in step S10 and the detection result of the pressure of the refrigerant gas acquired in step S20.

[0042]In addition, the opening degree determination unit 102 calculates a vane opening degree increase/decrease coefficient XB based on equation (1) by using the allowable before-after differential pressure ΔPsb and the correction value K acquired in step S10 and the used rotation speed of the turbo compressor 3 acquired in step S20.

$\begin{array}{cc}\mathrm{XB}=\left(\Delta \mathrm{Psb}\times K\right)/\left(f\left(\rho \right)\times \mathrm{XN}\right)& \left(1\right)\end{array}$

[0043]f(ρ) is a reference estimated differential pressure of the vane 13 when starting the turbo compressor 3, which is calculated by a function determined in advance based on the density of the refrigerant gas. The device information of the turbo compressor 3 read from the storage unit 105 includes a difference (model difference) for each model. The reference estimated differential pressure is for including the model difference and is used as reference (base) for control for each model of the turbo compressor 3. In addition, XN is an increase/decrease coefficient of the Mach number determined according to the rotation speed of the turbo compressor 3. As the Mach number (the rotation speed of the turbo compressor 3) increases, a larger amount of refrigerant flows into the turbo compressor 3, and a load on the vane 13 increases. The increase/decrease coefficient of the Mach number is used to take into account fluctuations of the load on the vane 13 according to the Mach number.

[0044]The opening degree determination unit 102 calculates the required vane opening degree of the vane 13 that is required when starting the turbo compressor 3, with a function f(XB) determined in advance based on the vane opening degree increase/decrease coefficient XB calculated through equation (1). Herein, when the opening degree (=angle) of the vane 13 changes, a force (a resistance force for moving the vane 13) received from the refrigerant (fluid) changes in accordance with the change. For this reason, it is preferable to calculate the required vane opening degree of the vane 13 by taking into account the vane opening degree increase/decrease coefficient XB.

[0045]The required vane opening degree of the vane 13 calculated in this manner in step S31 is larger as the pressure of the refrigerant gas acquired in step S20 is higher. In addition, the required vane opening degree of the vane 13 is larger as the used rotation speed of the turbo compressor 3 acquired in step S20 is higher.

[0046]Next, the opening degree determination unit 102 checks whether or not the required vane opening degree of the vane 13 calculated in step S31 falls within a set opening degree range of the vane 13 set in advance. The opening degree determination unit 102 determines the required vane opening degree of the vane 13 such that the required vane opening degree falls between a minimum opening degree set value and a maximum opening degree set value of the vane 13 which are set in advance.

[0047]To this end, first, the opening degree determination unit 102 determines whether or not the required vane opening degree of the vane 13 calculated in step S31 is equal to or larger than the minimum opening degree set value set in advance (step S32).

[0048]In step S32, in a case where the required vane opening degree is not equal to or larger than the minimum opening degree set value (step S32: No), the opening degree determination unit 102 updates and determines the required vane opening degree of the vane 13 when starting the turbo compressor 3 to the minimum opening degree set value (step S33). Accordingly, an excessive decrease in the actual opening degree of the vane 13 can be suppressed when starting the turbo compressor 3.

[0049]In addition, in step S32, in a case where the required vane opening degree is equal to or larger than the minimum opening degree set value (step S32: Yes), the opening degree determination unit 102 determines whether or not the required vane opening degree of the vane 13 calculated in step S31 is equal to or smaller than the maximum opening degree set value set in advance (step S34).

[0050]In step S34, in a case where the required vane opening degree is not equal to or smaller than the maximum opening degree set value (step S34: No), the opening degree determination unit 102 updates and determines the required vane opening degree of the vane 13 when starting the turbo compressor 3 to the maximum opening degree set value (step S35). Accordingly, an excessive increase in the actual opening degree of the vane 13 can be suppressed when starting the turbo compressor 3.

[0051]In addition, in step S34, in a case where the required vane opening degree is equal to or smaller than the maximum opening degree set value (step S34: Yes), the opening degree determination unit 102 determines the required vane opening degree of the vane 13 calculated in step S31 as it is as the required vane opening degree of the vane 13 when starting the turbo compressor 3 (step S36).

[0052]The opening degree control unit 103 adjusts the actual opening degree of the vane 13 by controlling the opening degree adjustment mechanism 17 based on the required vane opening degree determined as described above. After then, the chiller control device 100 starts the turbo compressor 3.

[0053]The chiller control device 100 adjusts the opening degree of the vane 13 in accordance with the used rotation speed of the turbo compressor 3 after starting the turbo compressor 3.

Operational Effects

[0054]In the centrifugal chiller 1, the chiller control device 100, the control method of a centrifugal chiller, and the program having the above configuration, when starting the centrifugal chiller 1, at least the state amount of the refrigerant gas is acquired, and the opening degree of the vane 13 is controlled based on the acquired state amount. Accordingly, when starting the centrifugal chiller 1, the opening degree of the vane 13 can be set according to the state of the refrigerant gas at that time. Therefore, startability of the centrifugal chiller 1 can be improved regardless of the state of the refrigerant gas at the time of starting.

[0055]In addition, the density of the refrigerant gas can be calculated by acquiring the pressure of the refrigerant gas sucked by the turbo compressor 3 as the state amount of the refrigerant gas. Accordingly, the opening degree of the vane 13 can be controlled according to the density of the refrigerant gas when starting the centrifugal chiller 1.

[0056]Further, by detecting the pressure of the refrigerant gas on the outlet side of the evaporator 9 with the pressure sensor 120, the pressure of the refrigerant gas sucked by the turbo compressor 3 can be easily acquired as the state amount of the refrigerant gas.

[0057]In addition, a differential pressure caused by the refrigerant gas acting on the vane 13 can be acquired based on the pressure of the refrigerant gas sucked by the turbo compressor 3 and the used rotation speed of the turbo compressor 3 during the steady operation of the centrifugal chiller 1. By calculating the opening degree of the vane 13 based on the acquired differential pressure, the opening degree of the vane 13 can be appropriately adjusted while suppressing hindrance of the opening degree adjustment of the vane 13 due to the differential pressure acting on the vane 13.

[0058]In addition, by determining the opening degree of the vane 13 to fall between the minimum opening degree set value and the maximum set value, the opening degree of the vane 13 can be appropriately adjusted.

Other Embodiments

[0059]Although the embodiment of the present disclosure has been described in detail with reference to the drawings hereinbefore, a specific configuration is not limited to the embodiment, and design changes or the like are also included without departing from the gist of the present disclosure.

[0060]In the embodiment described above, the procedures of a control method of the centrifugal chiller 1 are described as an example, but the procedures thereof can be changed as appropriate.

[0061]In addition, a part or all of the program executed by the computer in the above embodiment can be distributed via a recording medium or a communication line readable by the computer.

APPENDIX

[0078]Accordingly, the startability of the centrifugal chiller 1 can be improved regardless of the state of the refrigerant gas at the time of starting.

INDUSTRIAL APPLICABILITY

[0079]With the centrifugal chiller, the chiller control device, the control method of a centrifugal chiller, and the program according to the present disclosure, startability can be improved regardless of the state of the refrigerant gas at the time of starting.

REFERENCE SIGNS LIST