This example illustrates the use of the cooling tower model
Buildings.Fluid.HeatExchangers.CoolingTowers.FixedApproach,
using the outdoor dry-bulb temperature as the potential for heat
transfer. Heat is injected into the volume vol. An
on/off controller switches the cooling loop water pump on or off
based on the temperature of this volume. The cooling tower outlet
temperature has a fixed approach temperature to the outdoor
dry-bulb temperature.