Transient model of a vertical freezer with door openings and defrost effects

Abstract

Cabinet temperature evolution and energy consumption are two parameters of primary importance for food/medicals preservation and energy savings in cold appliances. In this paper, a transient model of a vertical freezer is developed to study the trend of cabinet temperature and of energy consumption with time, taking also into account door openings, air leakage, frost formation and defrost effect. The model is validated with the experimental data, both with in-house data and with data available in the open literature for frost formation. The results are presented with varying operating conditions, such as air temperature, air humidity, frequency of door opening and defrosting. A qualitative comparison of the trends of air temperature inside the cabinet and of power consumption showed a good agreement between the experimental and simulated profiles; a good agreement was also found in the statistical analysis of errors, with maximum absolute errors on the time averaged temperature of air inside the cabinet of the order of 4K and maximum relative error on the time averaged power consumption of the order of 4%. Sensitivity analyses are reported as examples to exploit the potential of the model as a tool for design of systems, for settings for defrost parameters and for preventing fault events for food/medical preservation.