Question

Air and fuel enter a furnace used for home heating. The air has an enthalpy of 320 kJ/kg and the fuel has an enthalpy of 43027 kJ/kg. The gases leaving the furnace has an enthalpy of 616 kJ/kg. There are 17 kgair/kgfuel, water circulated through the wall furnace receiving heat. The hose required 17.02 kW of heat, what is the fuel consumption per day. (41 kg/day)

Answer 1

Here in question it is given the enthalpy of air as h_a=320 KJ/kg and the enthalpy of fuel is

h_f=43027 kJ/kg the gases leaving at an enthalpy of h_m=616 Kj/kg here , for heating air the fuel requirement is $17 \frac{kg(air)}{kg(fuel)}$ so,

Here it is given that hose required heat as 17.02 kW = $17.02 \frac{kJ}{s}$

Total heat requirement per day by hose will = $17.02\times3600\times24=1470528 kJ$

Net enthalpy exchange by air to heat the hose = $(h_f+h_a)-h_m=42731 kJ$ /kg

so, net mass of air consumption per day $= \frac{1470528}{42731} =34.41 Kg$ /day

so net mass of fuel consumption per day =$\frac{34.41}{17.02}=2.02 kg$ of fuel per day