RESUMO

Heat engines, heat pumps, and other various thermodynamic systems, containing coupled heat work conversion and heat transfer processes, are widely used in engineering fields. Improving the thermal performance of such energy systems through thermodynamic optimization is of high significance in energy saving. In this paper, in order to investigate the interactive influence mechanism between heat work conversion and heat transfer processes in coupled thermodynamic systems, the simplified models of irreversible heat engine and heat pump cycles, respectively, are constructed. Moreover, the mathematical relationships between the heat work conversion entropy generation (S_g), heat exchange areas distribution ((UA)_h, (UA)_c), and the coefficient of performance (COP) are established. Aimed at maximizing COP of the heat engine and heat pump, the optimal heat exchange area distributions are determined by applying an inverse problem and variation method. The preliminary results show that COP always decreases with increasing heat work conversion entropy generations (S_g) and the optimal UA ratio of the two heat exchangers is the function of entropy generations (S_g) for both heat engine and heat pump. It also indicates that in ideal cycles with no heat work conversion irreversibility (S_g = 0), the heat exchange areas (UA) should be distributed equally. Otherwise, for practical irreversible cycles (S_g > 0), it should give priority to the enhancement of the heat transfer process in the condenser if the total heat exchange areas are limited. This work can offer guidance for the optimization design of practical coupled heat work conversion and heat transfer systems.