Quasi(Almost) Equilibrium(Static) Processes <---> Real Life Processes Hi, I am posting here for the first time, hence, should I have violated any forum rules I am sorry and kindly advise. I am a novice so please bear with me. Thank you. I read everywhere (in text books) that a quasiequilibrium or a quasistatic process is an ideal process and we try to achieve same whilst modelling any system. But in reality we get close to quasiequilibrium or quasistatic but never overlap the ideal form of it. Just able to get as closer as we can to a quasiequilibrium or quasistatic. Now my question is, in real life I have seen heat engines and heat pumps working really fast. This is what I observe. Should I look at the vapor compression air conditioners (heat pump) or 4 Wheeler's IC Engine (heat engine). They all work really really fast. So how are they said to be almost quasistatic/quasiequilibrium? Quasistatic/quasiequilibrium are also said to be reversible. Now when these real life equipments are working helluva fast, how can the processes going inside them are termed to be reversible? Please help me out of this predicament.