A cyclic thermodynamic heat engine, which combines adiabatic and isothermal processes and consists of classical ideal gas as working substance, runs most efficiently if it is reversible.
以经典理想气体为工质的卡诺热机循环由两个等温和两个绝热过程构成，热机可逆时，它的效率为最大。
2
Reversible proton exchange membrane fuel cell (RPEMFC) is an electrochemical cell working both as the water electrolyzer (charging) and fuel cell (discharging).