Central cooling system and controlling method for the same

1. 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=β 1 +β 2 T ch +β 3 T ao +β 4 T co +β 5 T wb +β 6 T out +β 7 T ch 2 +β 8 T ao 2 +β 9 T co 2 +β 10 T wb 2 +β 11 T out 2 +β 12 T ch T ao +β 13 T ch T co +β 14 T ch T wb +β 15 T ch T out +β 16 T ao T co +β 17 T ao T wb +β 18 T ao T out +β 19 T co T wb +β 20 T co T out ,

where β 1 through β 20 denote constants, T co denotes the temperature of the coolant, T ao denotes the temperature of the air, T ch denotes the temperature of the heat exchange medium, T wb denotes a wet-bulb temperature of the ambient air, and T out denotes a dry-bulb temperature of the ambient air.

2. The central cooling system of claim 1 , wherein the control unit is configured to control the operation of at least one of the ventilation fan unit, the chiller unit, and the cooling tower unit corresponding to at least one of the calculated control temperatures of the heat exchange medium, the coolant, and the air.

3. The central cooling system of claim 1 , wherein the control unit is configured to determine at least one coefficient or constant value of the quadratic function (P) through a least squares linear regression analysis for the energy consumption of the central cooling system according to measured temperatures of the heat exchange medium, the coolant, and the air and humidity in the sensor unit when the central cooling system is in operation.

4. The central cooling system of claim 1 , wherein the control unit is configured to compare the calculated control temperature of the heat exchange medium with a first temperature range and configured to set the control temperature of the heat exchange medium according to a result of the comparison.

5. The central cooling system of claim 1 , wherein the control unit is configured to compare the calculated control temperature of the coolant with a second temperature range and configured to set the control temperature of the coolant according to a result of the comparison.

6. The central cooling system of claim 1 , wherein the control unit is configured to compare the calculated control temperature of the air with a third temperature range and configured to set the control temperature of the air according to a result of the comparison.