The approach of a cooling tower varies directly with the heat load
of a process. Heat load is defined as the total heat to be removed
from the circulating water by the cooling tower per unit time
(Btu/hr). Heat load is a function of water flow rate and range.
Because of this, heat load will increase with increasing flow and/
or range. A cooling tower that is cooling less of a heat load can
cool to lower cold water temperatures than a similar cooling tower
cooling more heat load.