Question - When Specifying A Cooling Tower, Should I Look Up Historic Wet Bulb Temperatures For My Area Or Should I Take Measurements?
Answer -
If this is a new installation, look up historical wet bulb temperatures for area and be sure to report them to the cooling tower manufacturer as "ambient wet bulb temperatures". The manufacturer will adjust this temperature accordingly to estimate an "entering wet bulb temperature".
If you have an existing tower that is to be replaced, take several wet bulb temperature measurements near the air inlet during the hottest months. Report this as the "entering wet bulb temperature" to the tower manufacturer.
The difference between the ambient and the entering wet bulb temperatures is to account for wet recirculation from the tower exit back to the tower entrance. The entering wet bulb temperature always higher than the ambient wet bulb temperature.