Parameters to be measured: Air wet bulb temperature, air dry bulb temperature, cooling tower inlet water temperature, cooling tower outlet water temperature, discharge temperature, pump and motor operating parameters, water flow velocity, air flow rate;

Operating parameters: Cooling water temperature difference, cooling width, efficiency, cooling tower capacity, make-up water volume, cooling water flow rate, type selection, cooling tower type selection and design issues.

1. Cooling water temperature difference

Inlet temperature — large temperature difference at outlet = high performance

2. Cold Range

The difference between the cooling tower outlet water temperature and the inlet air wet bulb temperature: small cooling amplitude = high performance

3. Cooling tower capacity

The unit of cooling tower capacity is “kcal per hour”or“cooling ton”;

Cooling tower capacity = cooling water mass flow & times; specific heat capacity of water & times; temperature difference;

Large capacity = high performance

4. Calculation of make-up water volume

Evaporative water loss (E)

E = Q/600 = (T1-T2)*L /600

E represents the amount of evaporated water (kg/h) ;

Q stands for heat load (Kcal/h);

600 represents the latent heat of evaporation of water (Kcal/h);

T1 represents the water temperature (℃);

T2 represents the water temperature (℃);

L represents the circulating water volume (kg/h).

5. Calculation of make-up water volume

Splash loss (C)

The splash loss of the cooling tower is determined by the cooling tower design type, wind speed and other factors. Under normal circumstances, its value is about 0.1~0.2% of the circulating water volume.

Periodic discharge water loss (D)

The loss of regular discharge water is determined by factors such as water quality or solid concentration in the water. Generally, it is about 0.3% of the circulating water volume.

M=E+C+D

Water loss by evaporation (E); Water loss by splashing (C); Water loss by regular discharge (D).

When the cooling tower is used for air conditioning, the temperature difference is designed to be 5°C, and the make-up water required by the cooling tower is about 2% of the circulating water.

6. Cooling water flow

K·Q=C·M·ΔT

K: Estimation coefficient

Q: The maximum cooling capacity of the unit

C: Specific heat capacity of water

ΔT: temperature difference between supply and return water

M: Cooling water mass flow

The maximum cooling capacity of the compression refrigeration unit is 1.3 times;

2.5 times the cooling capacity of absorption refrigeration units (lithium bromide).

Example of selection: Example: a project with a 640RT unit cooling tower water flow and water supply.

Q=640RT=2251KW

K=1.3

C=4.2KJ/(kg·℃)

ΔT=5℃

Water replenishment m=M·2%=140kg/s·2%=2.8kg/s