Calculate the cooling load on the washer

Question

An air conditioning plant is designed to maintain a room at a condition of 20⁰C dry bulb temperature and specific humidity 0.0079 kg/kg dry air when the outside condition is 30⁰C dry bulb temperature and 40% saturation. The corresponding heat gains are 18000 W (sensible) and 3600 W(latent). The supply air contains one-third outside air by mass and the supply temperature is to be 15⁰C dry bulb temperature.

      The plant consists of mixing chamber for fresh and recirculated air, an air washer with chilled spray water with an efficiency of 80%, an after heater battery and a supply fan.

      Neglecting temperature changes in fan and ducting, calculate:

1. the mass flow rate of supply air necessary ;
2. the specific humidity of the supply air;
3. the cooling load on the washer;
4. the heating load on the after heater.