Question

In the compression stroke of an internal combustion engine the heat rejected to

the cooling water is 45 KJ/Kg and the work input is 90 KJ/Kg. Calculate the

Change in internal energy of the working fluid stating whether it is a gain or

loss

Answer 1

According to the first law of thermodynamics

$Q=\Delta U+W\to \Delta U=Q-W=-45-(-90)=45\ (kJ/kg)$

It is a gain.