Experimental evaluation of a R290 vapour compression refrigeration system hybridised with a thermoelectric subcooler

• First experimental study of a thermoelectric subcooler in propane cooling systems. • Systematic COP improvements of 3.6–––6.2% under all tested operating conditions. • Maximum COP achieved at low thermoelectric subcooler voltages (1.0–––1.5 V) • Flexible TESC operation boosts cooling capacity up to 16.2% in pull-down processes. The HVAC and refrigeration sector accounts for a significant share of global electricity consumption and greenhouse gas emissions, driving the adoption of low global warming potential refrigerants and more energy-efficient technologies. Among these refrigerants, propane has emerged as a promising alternative, and thermoelectric subcooling has been identified as an attractive performance-enhancing solution for low-capacity applications, motivating the design and construction of an experimental propane refrigeration test bench. This facility incorporates an internal heat exchanger to ensure safe and reliable operation, along with a novel thermoelectric subcooler (TESC). The experimental tests have been performed at two different ambient (25 and 35 °C) and evaporating (−15 and −10 °C) temperatures, and varying the voltage supplied to the TEMs. Two system configurations were evaluated: the baseline cycle with only the internal heat exchanger (IHX), which serves as the reference, and the combined TESC + IHX configuration. Performance comparisons between the two configurations were conducted for all the tested operating temperatures. The results show that the TESC + IHX configuration outperforms the IHX configuration under all tested conditions, with improvements in coefficient of performance of up to 6.2% and increases in cooling capacity of up to 9.7% at the optimal operating point. In addition, the TESC allows an almost linear regulation of the cooling capacity by adjusting the supplied voltage. This feature provides not only improved system performance but also greater operational flexibility and controllability, enabling the system to adapt to changes in ambient conditions and transient peak demands without the need for oversizing.