Determining thermal parameters in the cooling of a small-scale high-pressure freezing vessel

High-pressure supported freezing processes need a more efficient refrigeration technique to be applied at industrial level. A cooling method consisting in the circulation of a refrigerant in ebullition around the product in the vessel has been tested on a lab-scale prototype built for that purpose. The cooling kinetic of a mixture of ethanol, ethylene glycol and water (a usual pressurizing medium) was followed, recording temperatures in the whole sample. A mathematical model has been developed to describe heat transfer during cooling of the sample in the vessel. The heat transfer coefficient between the refrigerant and the vessel was determined by a fitting procedure between the numerical simulation results and the experimental measurements. This model should be used to predict the cooling kinetics in other conditions (other products, larger vessels) and to optimise the process.