what are cooling tower calculations?

Cooling Towers design depend on the calculation of the following:

1.  Evaporation.
2. Temperature Drop.
3. Recirculation Rate
4. Concentration Ratio or Cycles of Concentration.
5. Make Up Water.
6. Holding Capacity or System Volume.
7. Blowdown Rate.

It's too long and need to the explain of each step, you can found in Process calculation handbook or any thermal engineering books.

would you be able to provide a detailed expalnation on this issue with some mathematical expressions?

 

Evaporation loss, drift loss & blow down loss.
Based on the heat rejection from the chiller, %age of drift loss and number of COC one could derive the total losses through the cooling towers.