Thermogalvanic cells are a kind of heat engine. An example of a DCM heat engine is the drinking bird. So Equation gives the efficiency of any reversible heat engine. Undaunted, he returned to his youthful fascination with the mechanics of the heat engine. A Hadley cell is an example of a heat engine. A domestic refrigerator is an example of a heat pump&colon; a heat engine in reverse. The energetics of the system may be idealized as an atmospheric Carnot heat engine. The source of energy in a heat engine, is a heat input. This also categorizes the engine device as an external heat engine. We first look at a heat engine, assuming that formula 33. A pop pop boat is powered by a very simple heat engine. The ideal Stirling cycle is unattainable in the real world, as with any heat engine. However, a microscopic Carnot heat engine has been designed and run. For a real heat engine, the total thermodynamic process is generally irreversible. A Carnot heat engine is a theoretical engine that operates on the Carnot cycle.