Exergy Based Ecological Performance Analysis of a Waste Heat-Powered Marine Refrigeration Cycle

The escalating costs of fuel, global fuel supply disruptions, and stringent international emissions regulations necessitate more efficient ship operations.A key component of environmentally sustainable, economical, and efficient marine transportation is the recovery and utilization of waste heat.This study investigates the potential of converting waste heat from ship exhaust gas into useful energy through an organic Rankine cycle and its subsequent integration into a refrigeration system.In this study, the thermodynamic performance of the refrigerants R717, R152a, R290, and R134a was investigated.The findings demonstrate that R717 exhibits superior performance in terms of utilization factor and second law efficiency ( II ), while R290 emerges as the optimal choice when minimizing total entropy generation (s gen_TOT ) is the primary objective.If the priorities are focused on maximizing useful work production, minimizing energy losses, and reducing environmental impacts, the advantages of the R717 refrigerant, which has the highest total ecological coefficient of performance (ECOP) and exergetic performance criteria (EPC) values, are clearly evident.The ideal operating temperatures for evaporator temperature (T Evap ) and turbine temperatures (T Turbine ) concerning EPC and ECOP, using R717 as the refrigerant, were investigated in the continuation of the study.During this investigation, changes in T Evap and T Turbine were observed to have affected other components.When the T Evap is kept constant, and the T Turbine amount is increased, an improvement was observed in EPC TOT , ECOP TOT , II , and utility factor values, while an increase in s gen_TOT and exergy destruction (ExD TOT ) values.When the T Turbine is kept constant, a decrease is observed in the EPC TOT value.At the same time, an improvement is seen in ExD TOT , II , and ECOP TOT values, while an increase is noted in the s gen_TOT value.