A motor cycle engine delivers a power of l0 kW, by consuming petrol at the rate of 2.4 kg/hour. If the calorific value of petrol is 35.5 MJ/kg, the rate of heat rejection by the exhaust is

Heat received (or produced by the burning of petrol) in one hour will be              = (2.4 kg/hour)(3.5 MJ/kg)             = 85.2× 106 J/hour∴ The rate at which heat is received    = 85.2 ×106J(3600s) = 2.37 ×104 J/s = 23.7 kWEvidentaly, the rate of heat rejection = rate at which heat is produced - rate at which work is obtained = 23.7 kW - 10kW - 13.7 kW