Question

A heat engine with a thermal efficiency of 25% is connected to an electric generator with an efficiency of 95%. A liquid fuel providing heat is consumed at 2.29 litres per hour. What is the power output in kW from the generator?

Heat of Combustion: 43.7 MJ/kg
Density of the fuel: 0.749 g/ml

Answer 1

4.94 kW

Step-by-step explanation:

The heat energy produced by the fuel in one hour is ...

(2.29 L/h)(0.749 kg/L)(43.7 MJ/kg) = 74.954677 MJ/h

Then the power output is ...

(74.954677 MJ/h)(1 h)/(3600 s) = 20.8207 kJ/s

Multiplying this heat energy by the efficiencies of the processes involved, the output power is ...

(20.8207 kW)(0.25)(0.95) = 4.94 kW