In case of air conditioning units, the airflow at the Fan Coil Units (FCU) or the Air Handling Units (AHU) can be measured with an anemometer.
Dry bulb temperatures and wet bulb temperatures are measured at the inlet and outlet of AHU or the FCU and the refrigeration load in TR is assessed as ;
TR = Q x Rho x (H in – H out) / 3024
Where,
TR is the Ton of refrigeration
Q is the air flow in m3/h
Rho is density of air kg/m3
H in is enthalpy of inlet air kCal/kg
H out is enthalpy of outlet air kCal/kg
Use of psychometric charts can help to calculate Enthalpy H in and H out from dry bulb, wet bulb temperature values which are, in-turn measured, during trials, by a whirling psychrometer.