Performance evaluation of heater and recuperator in Brayton cycles for power and energy storage

Abstract

The performance of heat exchangers matters in the Brayton cycles for power and energy storage systems. However, the understanding of how heat exchanger performances affect cycle efficiency is still highly inadequate. The existing methods, including the performance evaluation criteria (PEC) and exergy/entropy analysis, are insufficient in evaluating the contributions of heat transfer enhancement or flow resistance reduction to the cycle performance. Also, the coupling analysis only provides the solutions for the cases under specific operation parameters of a specific cycle layout, in addition to their high computational cost and technical complexity. In the present work, a novel evaluation method, a performance recovery coefficient (PRC), was proposed to evaluate the effect of heat exchanger performances on the cycle efficiency simply using the component-scale parameters, avoiding complex coupling analysis. The applications of PRC in both heaters and recuperators were demonstrated, under different layouts, parameters and working fluids, of Brayton cycles for power generation, and integrated power generation and storage. Finally, it is shown that the PRC can facilitate the type selection and arrangement of heat exchangers of both direct and indirect heating, and deliver a cycle efficiency enhancement by 1.4 and 0.4 percentage points, respectively. Overall, the present method provides clear insights into how the interplay between heat transfer and flow resistance in heat exchangers contributes to cycle performance.