Heat Engine Net Work
Heat Engine Net Work
A heat engine’s net work is simply the heat it takes from the hot source minus the heat it dumps to the cold sink — energy conservation.
The net work is W = Q_h − Q_c. where Q_h is the heat absorbed and Q_c the heat rejected.
Inputs
Q_h := 1000 kJ=1e+06 Nm
Q_c := 650 kJ=650000 Nm
Subtract rejected heat from absorbed heat.
W := Q_h - Q_c=350000 Nm
Results
The fraction W/Q_h is the thermal efficiency. The rejected heat can never be zero (second law), capping how much work is possible.
Assumptions & limitations
- Cyclic operation (first law over a cycle).
- No other energy flows.
- Steady state.