Experimental evaluation of freezing processes in horizontal plate freezers using CO2 as refrigerant

This paper deals with an experimental analysis of freezing processes using a horizontal plate freezer with CO2 as refrigerant. The CO2 is supplied from an experimental CO2/NH3 cascade refrigeration system facility with a 9 kW of refrigeration capacity at −50 °C. The experimental facility, the data acquisition system and the experimental methodology are described. The experimental results include the temperature evolution in the product to be frozen, the CO2 evaporating temperature and freezing times. Results show a clear link between the freezing time and CO2 average evaporating temperature. The observed trend showed that a temperature reduction of 1 °C causes a reduction of approximately 2 min in the freezing time. The experimental results also include the refrigeration capacity of the facility, the electric power of the compressors and the cascade system COP. In addition, a numerical model of the freezing process using a commercial software was developed and validated. The results obtained would confirm that the use of CO2 as refrigerant in plate freezers represents a viable alternative to the refrigerants currently in use.

► We analysed freezing processes in a plate freezer with CO2 as refrigerant. ► Results show a clear link between freezing time and evaporating temperature. ► Decreasing evaporating temperature 1 °C decreases freezing time around 2 minutes. ► We develop a numerical model of the freezing processes. ► The numerical results show a good agreement with the experimental data.