Measurement of thermophysical properties and analysis of heat transfer during freezing of slab-shaped food commodities

Abstract

Experiments have been designed to measure water content, packing density and transient temperatures during cooling and freezing of fresh green peas packed in rectangular containers. Specific heat capacity in unfrozen and frozen states and latent heats of fusion are calculated from the measured water content. Experimental temperature records are used to calculate bulk thermal diffusivity, both in the frozen and unfrozen states, on the basis of transient heat transfer analysis. In the frozen state, the measured thermal diffusivity was found to vary almost linearly with temperature. A calculation scheme has been presented and applied to compute temperature variations during immersion and air-freezing of peas, using the measured thermal properties. The proposed scheme yielded the calculated freezing time lying within ±8% of its measured values. The calculated temperatures, with both first and second (Von Neumann) type of boundary conditions, were in good agreement with the measurements of present and earlier investigations.