Cooling device and control method for cooling device

Abstract

An object of the present invention is to prevent cavitation in a refrigerant pump from occurring due to a decrease in a net positive suction head in a cooling device. A cooling device of the present invention is a cooling device using a refrigeration cycle in which a refrigerant is circulated through a heat receiver ( 1 ), a compressor ( 2 ), a heat radiator ( 3 ), and an expander ( 4 ), and includes a tank ( 5 ) that separates the refrigerant supplied from the expander ( 4 ) into a gas phase refrigerant and a liquid phase refrigerant, a pump ( 6 ) that sends the liquid phase refrigerant separated in the tank ( 5 ) to the heat receiver ( 1 ), and a control unit ( 7 ) that controls the amount of increase in pressure of the compressor 2 in the refrigeration cycle, and the control unit ( 7 ) increases the pressure of the compressor ( 2 ) in a limited range in which the value of the net positive suction head of the pump ( 6 ) does not fall below a predetermined value.

1 . A cooling device using a refrigeration cycle in which a refrigerant is circulated through a heat receiver, a compressor, a heat radiator, and an expander, the cooling device comprising:
 a gas-liquid separator configured to separate the refrigerant supplied from the expander into a gas phase refrigerant and a liquid phase refrigerant;   a pump configured to send the liquid phase refrigerant separated by the gas-liquid separator to the heat receiver; and   a control unit configured to control an amount of increase in pressure of the compressor in the refrigeration cycle,   wherein the control unit limits a value of a net positive suction head of the pump to a range in which the value does not fall below a predetermined value and increases the pressure of the compressor.   
     
     
         2 . The cooling device according to  claim 1 , wherein the control unit calculates the net positive suction head from an inlet pressure of the pump, a saturated vapor pressure of the refrigerant, and a density of the refrigerant. 
     
     
         3 . The cooling device according to  claim 1 , wherein the control unit calculates the net positive suction head from detection data of a pressure sensor and a temperature sensor, the pressure sensor being configured to measure an inlet pressure of the pump, the temperature sensor configured to measure a temperature of a liquid phase portion of an inlet of the pump. 
     
     
         4 . The cooling device according to  claim 1 , wherein the control unit calculates the net positive suction head from detection data of a pressure sensor and a temperature sensor, the pressure sensor being configured to measure a pressure of the refrigerant inside a bypass pipe configured to connect a discharge side to a suction side of the pump, the temperature sensor configured to measure a temperature of the refrigerant. 
     
     
         5 . The cooling device according to  claim 1 , wherein the control unit calculates the net positive suction head from a pressure, a temperature, and a liquid level height of the refrigerant inside the gas-liquid separator. 
     
     
         6 . The cooling device according to  claim 1 , wherein the control unit increases the pressure of the compressor in a plurality of stages. 
     
     
         7 . The cooling device according to any one of  claims 1 to 6 , wherein the control unit controls an amount of heat radiated from the heat radiator together with the increase in pressure of the compressor. 
     
     
         8 . A control method for a cooling device using a refrigeration cycle in which a refrigerant is circulated through a heat receiver, a compressor, a heat radiator, and an expander, the control method comprising:
 limiting, by a control unit, a value of a net positive suction head of a pump to a range in which the value does not fall below a predetermined value, the pump being configured to suck a liquid-phase refrigerant from a gas-liquid separator and send the liquid phase refrigerant to the heat receiver, the gas-liquid separator being configured to separate the refrigerant supplied from the expander into a gas phase refrigerant and the liquid phase refrigerant; and   controlling, by the control unit, an increase in the pressure of the compressor.