Central cooling system and controlling method for the same

A central cooling system comprising:

• a ventilation fan unit configured to provide air to a predetermined space and including a ventilation fan;
• a chiller unit configured to provide a heat exchange medium to lower a temperature of the air through heat exchange between the air flowing into or out of the ventilation fan unit and the heat exchange medium;
• a cooling tower unit configured to provide a coolant to the chiller unit, the coolant lowering a temperature of the heat exchange medium through heat exchange between the coolant and the heat exchange medium in the chiller unit, the cooling tower unit configured to lower a temperature of the coolant through heat exchange between the coolant and ambient air outside of the predetermined space;
• a sensor unit comprising:
• a first sensor;
• a second sensor;
• a third sensor;
• and
• a fourth sensor, the first sensor configured to measure the temperature of the air provided from the ventilation fan unit, the second sensor configured to measure the temperature of the heat exchange medium discharged from the chiller unit, the third sensor configured to measure the temperature of the coolant entering the chiller unit from the cooling tower unit for the heat exchange between the coolant and the heat exchange medium in the chiller unit, and the fourth sensor configured to measure a temperature and humidity of the ambient air;
• and
• a control unit configured to monitor energy consumption of the central cooling system according to the temperature of the air, the temperature of the heat exchange medium and the temperature of the coolant measured in the sensor unit when the ventilation fan unit, the chiller unit and the cooling tower unit are in operation, and configured to calculate at least one of a control temperature of the heat exchange medium, a control temperature of the coolant, and a control temperature of the air which minimizes the energy consumption based on the measured temperatures of the heat exchange medium, the coolant, the air and the ambient air and the humidity of the ambient air by the sensor unit,
• wherein the heat exchange between the air flowing out of the ventilation fan unit and the heat exchange medium occurs in a guide duct connecting an outlet of the ventilation fan to the predetermined space,
• wherein the first sensor measures the temperature of the air at a location downstream of the heat exchange between the air flowing into or out of the ventilation fan unit and the heat exchange medium, and
• wherein the control unit is configured to calculate the energy consumption (Power) by a quadratic function (P) in which an optimum condition is analytically determined according to the following equation:
• Power=β1+β2Tch+β3Tao+β4Tco+β5Twb+β6Tout+β7Tch2+β8Tao2+β9Tco2+β10Twb2+β11Tout2+β12TchTao+β13TchTco+β14TchTwb+β15TchTout+β16TaoTco+β17TaoTwb+β18TaoTout+β19TcoTwb+β20TcoTout,
• where β1 through β20 denote constants, Tco denotes the temperature of the coolant, Tao denotes the temperature of the air, Tch denotes the temperature of the heat exchange medium, Twb denotes a wet-bulb temperature of the ambient air, and Tout denotes a dry-bulb temperature of the ambient air.