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.