On optimizing maximum-power heat engines

Abstract

Maximum power point characteristics of heat engines as a general thermodynamic problem Am.For a general class of heat engines operating at maximum power, in which the generic sources of irreversibility are finite-rate heat transfer and friction only, we investigate ( 1) the timedependent driving functions that maximize power when heat input and heat rejection are constrained to be nonisothermal, as is the case in many conventional heat engines, and (2) the specific impact of friction on the nature of the engine cycle that maximizes power, and on the engine's power-efficiency characteristic. The extent to which maximum power is affected by the constraints on the driving function is evaluated, as well as the time divisions on the different branches of the optimal cycle. The fundamental differences in engine performance that arise from frictional losses being internally dissipative, as opposed to externally dissipative, are derived, and illustrative examples are presented.

Coefficient of performance for a low-dissipation Carnot-like refrigerator with nonadiabatic dissipation

“…The influence on the performance of a classical or quantum heat engine, induced by internally dissipative dissipation (such as inner friction and internal dynamics, etc. ), has been discussed in several papers [28][29][30][31][32][33][34][35]. To the best of our knowledge, so far little attention has been paid to the effects of nonadiabatic dissipation on the performance characteristics of the refrigerators proceeding with finite time.…”

“…As emphasized, the irreversible entropy production in any adiabatic process [∆S As for isothermal processes, we also adopt the low-dissipation assumption for any adiabatic process [28,29,[32][33][34] to describe the irreversible entropy production. It is physically reasonable since the irreversible entropy production ∆S ir κ becomes much smaller and is vanishing in the longtime limit (τ κ → ∞) when the process is quasistatic.…”

Weighted reciprocal of temperature, weighted thermal flux, and their applications in finite-time thermodynamics

“…The other classic topic on nonequilibrium processes is finite-time thermodynamics [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] which is concerned * Corresponding author. Email: tuzc@bnu.edu.cn mainly with the energy conversion efficiency for heat devices including heat engines and refrigerators that complete thermodynamic cycles in finite time or operate in finite net rate.…”

Quantum four-stroke heat engine: Thermodynamic observables in a model with intrinsic friction

“…Real heat engines operate far from the reversible conditions, where the maximum power is restricted due to finite heat transfer [19], internal friction and heat leaks [20,21,22,23,24,25,26]. Analysis of the quantum models of heat engines, based on a first principle dynamical theory, enable to pinpoint the fundamental origins of finite heat transfer, internal friction and heat leaks.…”