Semi-empirical analysis of HFC supermarket refrigeration retrofit with advanced configurations from energy, environmental, and economic perspectives
Adrián Mota-Babiloni, Pau Giménez-Prades, Pavel Makhnatch, Jörgen Rogstam, Adrián Fernández-Moreno, Joaquín Navarro-Esbrí
Abstract
F-gas phase-down schedules will remove most of the HFCs (hydrofluorocarbons) used in refrigeration systems in the short term. Besides refrigerant substitution, configuration modifications can be considered in existing installations to increase energy efficiency. Basic cycle, direct injection, economiser, parallel compression, and cascade configurations with internal heat exchanger have been proposed to increase the energy efficiency of a supermarket refrigeration system when replacing R-404A with R-449A at low and medium temperatures. Both systems are based on indirect expansion and are equipped with a subcooler. Their regular operation was recorded using R-404A and R-449A during a representative period. Then, a semi-empirical approach is followed to determine R-449A energy performance with each proposed configuration. Only parallel compression (PC) and basic cycle with internal heat exchanger (IHX) benefit energy performance, highlighting the medium temperature (MT) system. However, this benefit is not extended to the environmental analysis because the R-449A charge in PC significantly increases. Moreover, additional PC components extend the expected payback period, and a drop-in replacement is financially more interesting. Therefore, using R-449A with minor modifications in the MT and LT R-404A refrigeration system decreases 52% and 60% carbon footprint, respectively. The payback period of this action is below one year in both circuits. This study provides a semi-empirical methodology for existing systems to predict alternative refrigerants' energy performance.