Numerical analysis of heat transfer characteristics of a novel heat exchanger for Lorenz-Meutzner cycle with zeotropic mixtures

Abstract

This study evaluates the performance enhancement of the Lorenz–Meutzner (LM) cycle with zeotropic mixtures of multiple refrigerants using a numerical simulation model. The computational simulation includes a heat exchanger model developed for predicting the air outlet temperature accurately. The predicted results are validated against experimental gliding temperature with varying mass fractions of different zeotropic mixture combinations. The R600/R290 mixture demonstrates the best performance characteristics. Various design changes of the heat exchanger are adopted to enhance the energy efficiency of the LM cycle. Counterflow configuration is found to be superior to the parallel configuration, particularly in the LM cycle, owing to the gliding temperature difference of zeotropic mixtures. Multiple refrigerant flow paths decrease the air outlet temperature further and prove to be more effective than the single flow path design. Based on careful investigation of the geometrical effect of heat exchangers on the LM cycle, a novel design of the heat exchanger is proposed, and its overall performance in the LM cycle is evaluated. The novel design of the heat exchanger indicates the largest air temperature difference, leading to the highest coefficient of performance (system energy efficiency) of the LM cycle compared with the baseline cycle with R600a.