Energy evaluation of the mechanical subcooling impact on a CO2 DX-system in a commercial MT cabinet.

Recent experimental studies of the use of the mechanical subcooling in CO2 plants have demonstrated the improvements in COP and Capacity that can be achieved. Improving the energy aspects in warm countries is important in order to equate these systems to the classical ones. The aim of this study is to analyse in an experimental way the effect of this system applied to a commercial medium temperature (MT) cabinet using direct expansion. This work measures the energy consumption of a direct expansion (DX) system using a CO2 cycle with dedicated mechanical subcooling with respect to a classic CO2 cycle, without mechanical subcooling. The laboratory environmental conditions for the cabinet were 25ºC and relative humidity of 55% and the experimental tests performed with both DX-systems have been carried out at six heat rejection temperatures (17.9, 23.6, 28.0, 32.7, 38.2 and 43.6ºC), providing the cooling needs to the medium temperature cabinet for fresh product (2 °C). The analysis and comparison of these experimental data are presented and discussed in this work.