Question

Air is flowing in an insulated duct at a rate of 2 kg/sec. Air enters the duct at 40 oC and 8-kW of heat is added with a electric resistance heater. Find the exit temperature of air. (Cp=1.005 kJ/kgK) a) 44 b)30 c) 54 d) 60

Answer 1

Answer:60°c

Etxplanation:

Heat added= mass flowrate* specific heat capacity*temperature change

Assuming 200kg of air

Q=MC∆Temperature

Q=8kw, T1 =40oC,C=1.005Kj/kgK

8000=2*200*1.005(T2-40)

8000/402= T2-40

19.9+40=T2

59.9oC=60°c