Power optimization of an endoreversible closed intercooled regenerated Brayton-cycle coupled to variable-temperature heat-reservoirs

In this paper, in the viewpoint of finite-time thermodynamics and entropy-generation minimization are employed. The analytical formulae relating the power and pressure-ratio are derived assuming heat-resistance losses in the four heat-exchangers (hot- and cold-side heat exchangers, the intercooler and the regenerator), and the effect of the finite thermal-capacity rate of the heat reservoirs. The power optimization is performed by searching the optimum heat-conductance distributions among the four heat-exchangers for a fixed total heat-exchanger inventory, and by searching for the optimum intercooling pressure-ratio. When the optimization is performed with respect to the total pressure-ratio of the cycle, the maximum power is maximized twice and a 'double-maximum' power is obtained. When the optimization is performed with respect to the thermal capacitance rate ratio between the working fluid and the heat reservoir, the double-maximum power is maximized again and a thrice-maximum power is obtained. The effects of the heat reservoir's inlet-temperature ratio and the total heat-exchanger inventory on the optimal performance of the cycle are analyzed by numerical examples.