R19 -- Thermal Properties of Foods - (I-P)

Thermal properties of foods and beverages must be known to perform the various heat transfer calculations involved in de-signing storage and refrigeration equipment and estimating process times for refrigerating, freezing, heating, or drying of foods and beverages. Because the thermal properties of foods and beverages strongly depend on chemical composition and temperature, and be-cause many types of food are available, it is nearly impossible to experimentally determine and tabulate the thermal properties of foods and beverages for all possible conditions and compositions. However, composition data for foods and beverages are readily available from sources such as Holland et al. (1991) and USDA (1975). These data consist of the mass fractions of the major components found in foods. Thermal properties of foods can be predicted by using these composition data in conjunction with temperature-dependent mathematical models of thermal properties of the individual food constituents.

Thermophysical properties often required for heat transfer calculations include density, specific heat, enthalpy, thermal conductivity, and thermal diffusivity. In addition, if the food is a living organism, such as a fresh fruit or vegetable, it generates heat through respiration and loses moisture through transpiration. Both of these processes should be included in heat transfer calculations. This chapter summarizes prediction methods for estimating these thermophysical proper-ties and includes examples on the use of these prediction methods. Tables of measured thermophysical property data for various foods and beverages are also provided.

Chapter Table of Contents

Thermal Properties of Food Constituents
Thermal Properties of Foods
Water Content
Initial Freezing Point
Ice Fraction
Density
Specific Heat
Enthalpy
Thermal Conductivity
Thermal Diffusivity
Heat of Respiration
Transpiration of Fresh Fruits and Vegetables
Surface Heat Transfer Coefficient
Symbols

Citation: 2010 ASHRAE Handbook -- Refrigeration: Chapter 19,Thermal Properties of Foods



Product Code(s): D-R192010IP