How this calculator works
A cyclic heat engine returns to its starting internal energy, so net work equals heat received minus heat rejected. Thermal efficiency is net work divided by heat received. Use totals over one complete cycle or consistent mass-specific quantities; do not mix these bases. The Carnot mode gives an independent reservoir-temperature ceiling. Real machines need both their energy balance and the second-law limit checked at the actual operating conditions.
Formula
eta = Wnet/Qin = 1 - Qout/Qin; Wnet = Qin - Qout; etaCarnot = 1 - Tc/Th.
Worked example
A cycle receiving 1000 J and rejecting 600 J delivers 400 J with 40% efficiency. Mass-specific heats of 800000 and 500000 J/kg give 300000 J/kg work and 37.5% efficiency.
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Frequently asked questions
Why use net work?
Subtract work consumed by pumps or compressors from work delivered by the power-producing components.
Can a heat balance alone prove feasibility?
No. An engine must also satisfy the second law, including the temperature-dependent efficiency bound.
Can heat input and output use different units?
The energy unit selectors convert totals to joules. Mass-specific entries are explicitly J/kg.