A car engine operates with a thermal efficiency of 35%. Assume the airconditioner has a coefficient of performance of β = 3 working as a refrigerator cooling the inside using engine shaft work to drive it. How much fuel energy should be spend extra to remove 1 kJ from the inside?
Car engine: W = ηeng Qfuel
Air conditioner: β = QL/W
W = ηeng /Qfuel = QL/β
Qfuel = QL / (ηeng β) = 1/0.35 x 3 = 0.952 kJ
