Theoretical analysis of a low-grade thermal energy based organic Rankine cycle coupled to an ultra-low temperature auto-cascade refrigeration cycle

Refrigeration systems powered by free thermal energy represent an excellent solution to address this issue. Combined systems of an Organic Rankine Cycle (ORC) and an Auto-Cascade Refrigeration Cycle (ARC) activated by low-temperature free heat offer an efficient approach to producing environmentally friendly cooling at ultra-low temperatures. This technology integrates an Organic Rankine Cycle with an internal heat exchanger (ORC) and an Auto-Cascade Refrigeration System (ARC) to achieve ultra-low temperatures, using a zeotropic mixture (R170 + R290) to produce temperatures ranging from −65°C to −45°C. For the ORC, dry fluids such as R245fa, R245ca, RE245cb2, RE245fa2, R1224yd(Z), R1233zd(E), and R1336mzz(Z) are utilized. In this article, a comprehensive thermodynamic model was developed to analyze the operational performance of the overall system. Based on the presented thermodynamic model, a parametric study was conducted to evaluate the impact of condensation and evaporation parameters on the overall system’s operation. The performance of the ORC, the ARC, and the overall system was analyzed. This article highlights the potential of utilizing low-temperature renewable energy to achieve ultra-low temperatures and provides a foundation for future research on the proposed system. It is noted that the operational COP of the system varies in all cases from 3.8 to approximately 20.