Which method is used to determine the approach of a cooling tower?

The method to determine the approach of a cooling tower involves measuring the temperature difference between the water leaving the tower and the wet bulb temperature of the air entering the tower. This is because the approach temperature indicates how efficiently the cooling tower is functioning in relation to the environmental conditions.

The wet bulb temperature represents the lowest temperature that can be achieved by evaporative cooling, taking into account both temperature and humidity. By comparing this with the cooling water temperature, you can gauge the effectiveness of the heat exchange process within the tower. A smaller approach temperature suggests that the cooling tower is functioning well and effectively chilling the water.

The other methods mentioned do not directly assess the cooling tower's efficiency in this relevant way. For instance, merely measuring the water flow rate or the temperature difference from the tower to the ambient temperature would not provide insight into the cooling tower's performance against the ambient air conditions. Additionally, measuring just the inlet air temperature does not reflect the tower's heat exchange effectiveness since it overlooks the outlet water's cooling performance compared to the air entering the system.