Experimental analysis of freezing times for fish and dummy loads in a horizontal CO₂ plate freezer at -50 °C evaporation temperature

This study experimentally evaluated the performance of an industrial-scale horizontal CO₂ plate freezer integrated into an existing CO₂ refrigeration system. The shared central CO₂ system can provide cooling capacity of 100 kW at evaporation temperature between -30 °C and -50 °C. Apple juice cartons were employed as the primary test material acting as dummy loads; freezing times were also measured for real fish samples—including mackerel, herring, and salmon. Freezing trials with apple juice cartons showed that lowering the average evaporation temperature from –36.1 °C to –48.6 °C reduced the average freezing time by 35.3%. Although the Coefficient of Performance (COP) was lower at reduced evaporation temperatures, specific energy consumption remained largely unaffected because of shorter freezing times. Additionally, lower circulation rates were associated with longer freezing time and higher specific energy consumption. The experimental results also demonstrated the importance of uniform plate contact, packaging material and configuration, and optimized product void space for freezing efficiency. A dynamic numerical model was developed and validated against the experimental data, showing good agreement with observed temperature profiles and freezing times.