Experimental enhancement of a CO2 transcritical refrigerating plant including thermoelectric subcooling

CO2 is an excellent natural refrigerant that can be used in almost any commercial cooling application thanks to its useful range of evaporative temperatures and excellent environmental properties. However, due to its low critical temperature, CO2 has an important issue related to the low performance of the simplest transcritical refrigeration cycle. To overcome it, the subcooling technique is a well-known method to improve the energy performance of any refrigeration cycle especially the CO2 transcritical one. The IHX is a widely used example of this method that is implemented in almost all standalone systems that use CO2 as a refrigerant. As an alternative of this element, in this work, a thermoelectric subcooling system is presented and tested in a CO2 transcritical refrigerating plant. The experimental tests have been performed at two ambient temperatures: 25 and 30 degrees C, maintaining a constant evaporating level at-10 degrees C and varying the voltage supply to thermoelectric modules and the heat rejection pressure. The results from these experimental tests revealed that the COP and the cooling capacity of the refrigerating plant can be enhanced up to 9.9% and 16.0%, respectively, operating at the optimum operating conditions. Moreover, the experimental tests corroborate the existence of an optimum voltage which maximizes the COP, and the almost linear capacity regulation easily adjustable by varying the voltage supply. (C) 2020 Elsevier Ltd and IIR. All rights reserved.