Refrigeration machine control device, turbo refrigeration machine, refrigeration machine control method, and program

A turbo refrigeration machine comprising:

• a turbo compressor which is configured to compress a refrigerant gas;
• a condenser which is configured to condense the refrigerant gas compressed by the turbo compressor;
• an expansion valve which is configured to expand a liquid refrigerant guided from the condenser;
• an evaporator which is configured to lower a temperature of chilled water flowing in from a chilled water inlet by evaporating the liquid refrigerant expanded by the expansion valve and then cause the chilled water to flow out from a chilled water outlet;
• an oil tank which stores lubricating oil to be supplied to the turbo compressor;
• a pressure equalizing pipe which connects the oil tank to the evaporator;
• and
• a refrigeration machine control device which is configured to control each of the parts,
• wherein the refrigeration machine control device includes:
• a processor configured to perform the functions of:
• a pressure reduction rate identification unit which is configured to identify a pressure reduction rate at which foaming does not occur in the oil tank, and
• a pressure adjustment unit which is configured to adjust a pressure of the evaporator on the basis of the identified pressure reduction rate;
• wherein the pressure reduction rate identification unit includes:
• a refrigerant precipitation gas volume calculation unit which is configured to calculate a volume of a refrigerant gas precipitated from the lubricating oil when the pressure is reduced at a predetermined pressure reduction rate;
• and
• a determination unit which is configured to determine whether or not the foaming is permissible on the basis of a comparison between the calculated volume and a volume on a surface of an oil in the oil tank,
• wherein the refrigerant precipitation gas volume calculation unit is configured to calculate the volume of a refrigerant gas precipitated from the lubricating oil by changing the predetermined pressure reduction rate when the determination unit determines that the foaming is not permissible, and
• wherein the pressure reduction rate identification unit is configured to identify the predetermined pressure reduction rate, in which the determination unit determines that the foaming is permissible, as the pressure reduction rate at which foaming does not occur.

A refrigeration machine control method in which a turbo refrigeration machine including a turbo compressor which is configured to compress a refrigerant gas, a condenser which is configured to condense the refrigerant gas compressed by the turbo compressor by radiating heat through heat exchange, an expansion valve which is configured to expand a liquid refrigerant guided from the condenser, an evaporator which is configured to lower a temperature of chilled water flowing in from a chilled water inlet by causing the liquid refrigerant expanded by the expansion valve to absorb heat and to evaporate due to the heat exchange and then cause the chilled water to flow out from a chilled water outlet, an oil tank which stores lubricating oil to be supplied to the turbo compressor, and a pressure equalizing pipe which connects the oil tank to the evaporator is controlled by a refrigeration machine control device,

• wherein the refrigeration machine control device includes a processor configured to perform the functions of:
• a pressure reduction rate identification unit which is configured to identify a pressure reduction rate at which foaming does not occur in the oil tank, and a pressure adjustment unit which is configured to adjust a pressure of the evaporator on the basis of the identified pressure reduction rate,
• wherein the pressure reduction rate identification unit includes a refrigerant precipitation gas volume calculation unit and a determination unit,
• wherein a volume of a refrigerant gas precipitated from the lubricating oil is calculated by the refrigerant precipitation gas volume calculation unit when the pressure is reduced at a predetermined pressure reduction rate,
• wherein whether or not the foaming is permissible is determined by the determination unit on the basis of a comparison between the calculated volume and a volume on a surface of an oil in the oil tank,
• wherein the refrigerant precipitation gas volume calculation unit is configured to calculate the volume of a refrigerant gas precipitated from the lubricating oil by changing the predetermined pressure reduction rate when the determination unit determines that the foaming is not permissible, and
• wherein the pressure reduction rate identification unit is configured to identify the predetermined pressure reduction rate, in which the determination unit determines that the foaming is permissible, as the pressure reduction rate at which foaming does not occur.

A non-transitory computer-readable recording medium that stores a program for controlling a turbo refrigeration machine by a refrigeration machine control device,

• the refrigeration machine control device including:
• a pressure reduction rate identification unit which is configured to identify a pressure reduction rate at which foaming does not occur in an oil tank, and
• a pressure adjustment unit which is configured to adjust a pressure of an evaporator on the basis of the identified pressure reduction rate,
• wherein the pressure reduction rate identification unit includes a refrigerant precipitation gas volume calculation unit and a determination unit,
• the program being configured to perform the steps of:
• calculating, by the refrigerant precipitation gas volume calculation unit, a volume of a refrigerant gas precipitated from the lubricating oil when the pressure is reduced at a predetermined pressure reduction rate,
• determining, by the determination unit, whether or not the foaming is permissible on the basis of a comparison between the calculated volume and a volume on a surface of an oil in the oil tank,
• calculating, by the refrigerant precipitation gas volume calculation unit the volume of a refrigerant gas precipitated from the lubricating oil by changing the predetermined pressure reduction rate when the determination unit determines that the foaming is not permissible, and
• identifying, by the pressure reduction rate identification unit, the predetermined pressure reduction rate, in which the determination unit determines that the foaming is permissible, as the pressure reduction rate at which foaming does not occur.