In a continuously operating drying oven, the leather layers are dried from 200% moisture to 15% humidity at 800 kg per hour. The ambient air with a specific humidity of 0.012kgsb/kgkh at a temperature of 20 C is heated up to 82 C in an electric heater and sent to the oven. The air comes out of the oven at 56 C and 0.022 kgsb/kgkh specific humidity. The skin enters at 20 C and leaves at 40 C.

a) Find the flow rate of air circulating per hour,

b) find The power of the electric heater,

c) find The heat given to evaporate 1 kg of water.

Cder=1.2 kJ/kg C, Cphava=1 kJ/kg C, Cpsteam=1.84 kJ/kg C, Cpsu=4.18 kJ/kg C, hsb,20C=2454.3 kJ/kg, hsb ,56C=2386.4 kJ/kg , hsb,82C=2303.8kJ/kg