Sensitivity of the food centre temperature with respect to the air velocity and the turbulence kinetic energy

摘要

The surface heat transfer coefficient is an important parameter to characterise forced convection heating and cooling processes. It expresses the influence of flow phenomena on the heat transfer rate to foods. For thermal process calculations, one often relies on dimensionless correlations that contain the flow properties, namely the free stream air velocity and the turbulence kinetic energy. This paper discusses the sensitivity of the food temperature with respect to these variables for different food geometries and con- ditions. The study is based on the finite element analysis of the product temperature deviations as a result from deviations of the surface heat transfer coefficient, combined with existing dimensionless correlations for the surface heat transfer coefficient. Sensi- tivity charts are constructed, which relate the temperature sensitivity with respect to the free stream air velocity and the turbulence kinetic energy to different air flow conditions as a function of time. By constructing sensitivity charts, it is shown that small velocity deviations can lead to large food temperature deviations. The effect of smaIl deviations of the turbulence intensity is not as sig- nificant.