Determine the total cooling load and the room heat gain.

Question

The air handling unit of an air conditioning plant supplies a total 4500 cubic metre/min of dry air which comprises 20 percent fresh air at 40⁰C DBT and 27⁰C WBT and 80 percent of recirculated air at 25⁰C DBT and 50% RH. The air leaves the cooling coil at 13⁰ C saturated state. Determine the total cooling load and the room heat gain. Take specific volume of air entering the cooling coil as 0.869 m³/kg da.

Condition	DBT 0C	WBT 0C	RH %	Sp. humidity gwv/kg da	Enthalpy kJ/kg da
Outside	40	27	-	17.2	85.0
Inside	25	-	50	10.0	50.8
ADP	13	-	100	9.4	37.0

 Note: ADP – Apparatus dew point

           wv – water vapour                                                      da – dry air.