Optimization of heat engines with fixed heat fluxes at the hot or the cold side

Abstract We use the low dissipation model to optimize the power of heat engines in which the total amount of energy taken from the hot reservoir is kept fixed while the total amount of energy dissipated to the cold reservoir is optimizable. Then, we optimize heat engines working while they reject fixed amounts of energy to the cold reservoir. We find that under these operating conditions, the maximum power and efficiency at maximum power are different from those of thermal engines that are optimized without imposing restrictions. For both working situations, we analyze the effect that small perturbations changing the value of the fixed heat (on the hot or cold side) have on the heat engine work, efficiency, and power.