What do you understand by mechanical and thermal efficiency? A steam plant uses 3 tonne of \(\mathrm{coal} / \mathrm{h}\). The steam is fed to turbine the output of which is \(4 \mathrm{MW}\). The calorific value of the coal is 30 \(\mathrm{MJ} / \mathrm{kg}\) calculate the thermal efficiency of the plant.