HEAT ENGINE - Thermodynamics:

HEAT ENGINE. A heat engine is a thermodynamics system that operates in a cycle in which heat can be transferred from heat source to heat sink. For the continuous production of work. Both heat and work interaction takes place across the boundary of engine. It receive heat Q₁ from a higher temperature  reservoir  at  T₁.

It converts part of heat Q₁ into mechanical work W₁. It reject residual heat Q₂ into sink at T₂. There is working substance that continuously flows through the engine to ensure continuous/cyclic operation.