IMMERSING COOLING OF LARGE SPHERICAL PRODUCES: THERMAL PARAMETERS

摘要

This article presents a combined experimental and modelling study for determining the thermal parameters of spherical produces in immersing cooling. In experiments, large spherically shaped water melons were selected as test samples, and cooled in water at surrounding temperatures of 0.5℃, 1.0℃, and 1.5℃. Inside temperatures of the produces were recorded at these water temperatures. In the analytical part, the models were introduced to determine the thermal parameters involved in the process, such as cooling coefficients, lag factors, heat transfer coefficients, thermal conductivities, thermal diffusivities, Biot numbers as well as the cooling times in terms of half cooling and seven-eighths cooling times. The results indicate that the cooling coefficient, the heat transfer coefficient, the Biot number, and the thermal diffusivity of the produce decreased by 3.2%, 0.42%, 0.42%, and 3%, respectively, with increasing cooling medium temperature. The lag factor increased by 9.3%. The half cooling time and the seven-eights cooling time indicating the cooling rates of the produce increased by respectively 15.01% and 7.56%. One can conclude that the present technique is a useful, simple and effective tool for determining thermal parameters for produces cooled in a fluid medium.