Thermodynamic Analysis of General Heat Engine Cycle with Finite Heat Capacity Rates for Power Maximization

In this study, a theoretical approach to the ideal cycle with finite heat capacity rates for maximizing power using a sequential Carnot cycle model is investigated. Although the Carnot efficiency is important, it is limited to evaluating only in terms of the temperatures, and power generation can be minimized. For the actual heat engine, especially from low-grade heat sources such as a waste heat, the power is more important than cycle thermal efficiency to produce maximum work. In this study, power optimization is numerically simulated through two design variables. First, the correlation between the variables is investigated, and optimum values are obtained using the pattern search algorithm (PSA) in MATLAB. The optimization is performed over several typical thermal capacitance rate ratios and overall heat transfer coefficient ( UA ) conditions. As a result, designing a lower temperature of fluid at the heat exchanger inlet for maximizing the heat received from heat sources does not always maximize the power, but the higher the UA , the lower the optimum temperature, and the higher the power output. These considerations can be used as a reference for the design and optimal operation of the actual low-grade heat source power cycle in future