Effect of convective and radiative heat transfer in evaporative losses during beef cooling.

Abstract

In the present work a numerical analysis is presented to identify the separate effect of cooling by radiation and convection, in evaporative meat weight loss during beef carcass cooling process. A transient heat and mass transfer model is proposed using a 3D beef side geometry. Water activity variations are incorporated in the model. Convective coefficients are obtained from correlations by considering buoyancy effect due to temperature and vapor concentration gradi ents, and forced air flow. For the purpose of model water mass diffusion into the carcass, a first approximation of the meat layer thickness affected by drying is obtained from an analytical analysis as a semi-infinite solid. The model is solved numerically and it is validated with experimental data from the literature. Results of heat load and weight loss are compared to models proposed by other authors. Temperature and surface water activity evolution, and temper ature and water content profiles are analyzed also. Finally, a sensitivity study is carried out on the main result of the model, total evaporated mass, varying heat convection coefficient and radiative cooling. It is found that there is a convective heat transfer coefficient that maximize the evaporative losses, so it is important to operate far from this point in order to reduce the evaporated mass. Furthermore, radiation during the meat cooling process turns out to be an interesting method to rapidly cool meat without increasing the evaporated mass (radiation cooling). Results shows that combining properly the convection and radiation heat transfer, evaporation losses can be reduced.