Cooling system and cooling method

A cooling method for a cooling system,

• wherein the cooling system includes:
• an evaporator for evaporating a coolant by heat exchange with indoor air that is an object of air conditioning;
• a condenser for cooling and thereby condensing the coolant evaporated by the evaporator;
• a coolant liquid storage section that communicates with the condenser and stores the liquid flowing in from the condenser;
• a coolant pump that communicates with the coolant liquid storage section and pressure-transmits the coolant liquid toward the evaporator, the coolant liquid flowing in from the coolant liquid storage section;
• a coolant liquid detection unit for detecting whether or not a liquid level of the coolant liquid stored in the coolant liquid storage section is higher than or equal to a predetermined height;
• and
• a control unit,
• the cooling method comprising the steps of:
• individually detecting whether or not the liquid level of the coolant liquid stored in the coolant liquid storage section is higher than or equal to respective plural heights including a first height and a second height higher than the first height in the coolant liquid storage section;
• and
• changing, by the control unit, a rotation speed of a motor of the coolant pump, corresponding to a detection result that is input from the coolant liquid detection unit.