Computer algorithms for calculating the cooling and freezing times, refrigeration loads and thermal properties of foods and beverages.

摘要

Preservation of food is one of the most significant applications of refrigeration. It is known that cooling and freezing of food effectively reduces the activity of micro-organisms and enzymes, thus retarding deterioration. In addition, crystallization of water reduces the amount of liquid water in food items and inhibits microbial growth.; In order for cooling and freezing operations to be cost-effective, it is necessary to optimally design the refrigeration equipment to fit the specific requirements of the particular cooling or freezing application. The design of such refrigeration equipment requires estimation of the cooling and freezing times of foods and beverages, as well as the corresponding refrigeration loads. These estimates, in turn, depend upon estimates of the thermal properties of foods and beverages.; Numerous methods for predicting the cooling and freezing times of foods and beverages have been proposed, including those based upon numerical, analytical and empirical analysis. In addition, various methods have been developed for estimation of the thermal properties of foods and beverages, including those based upon food composition data as well as empirical correlations. The designer is faced with the challenge of selecting appropriate estimation methods from the plethora of those available.; Therefore, this project reviewed the state-of-the-art in estimation methods for the thermal properties as well as the cooling and freezing times of foods and beverages. The performance of these various methods was evaluated by comparing their results to experimental freezing time data and thermophysical property data obtained from the literature. Suitable estimation methods were then selected based upon the performance evaluation. Step-by-step algorithms were developed from the selected cooling and freezing time estimation methods and thermal property models.; In addition, computer programs, based upon the selected estimation methods, were developed for calculating the cooling and freezing times, refrigeration loads and thermal properties of foods and beverages. WinFreeze is a computer program for determining the cooling and freezing times of foods and beverages, while the Thermophysical Properties Calculator is a computer program for determining the thermophysical properties of foods and beverages. Details of the operation of these computer programs are discussed in their respective user's manuals, Appendices D and E.