Experimental test of power-efficiency trade-off in a finite-time Carnot cycle

The Carnot cycle is a prototype of an ideal heat engine cycle to draw mechanical energy from the heat flux between two thermal baths with the maximum efficiency, dubbed as the Carnot efficiency eta C. Such efficiency is reached by thermodynamical equilibrium processes with infinite time, accompanied unavoidably with vanishing power-energy output per unit time. The quest to acquire high power leads to an open question of whether a fundamental maximum efficiency exists for finite-time heat engines with given power. We experimentally implement a finite-time Carnot cycle with sealed dry air as a working substance and verify the existence of a trade-off relation between power and efficiency. Efficiency up to (0.524 +/- 0.034)eta C is reached for the engine to generate the maximum power, consistent with the theoretical prediction eta C/2. Our experimental setup shall provide a platform for studying finite-time thermodynamics consisting of nonequilibrium processes.