Food Freezing Times and Heat Transfer Coefficients
Author: Bryan R. Becker, Ph.D., P.E. and Brian A. Fricke, Ph.D.
Freezing food is one of the most significant applications of refrigeration. Proper design of refrigeration equipment requires good knowledge of the surface-heat transfer coefficient for the freezing operation. This paper describes the thermodynamic of food freezing and reviews basic freezing-time estimation methods. It also describes a study to resolve deficiencies in heat transfer coefficient data for food freezing processes. Using actual freezing curves and transfer-heat data, a unique iterative algorithm was developed to estimate the surface- heat transfer coefficients of foods based on their freezing curves. Making use of this algorithm, heat transfer coefficients for various food items were calculated fro the freezing curves collected during an industry survey. The algorithm described in this paper was developed and used in recent ASHRAE research project to generate over 800 heat transfer coefficients that will appear I future additions of the ASHRAE Handbook. These heat transfer coefficients can then be used with the freezing-time estimation methods to achieve efficient design of food freezing equipment.