Evaluation of convective heat transfer coefficient between fluids and particles in suspension as food model systems for natural convection using two methodologies

摘要

This study was conducted to evaluate the convective heat transfer coefficient between Newtonian and non-Newtonian fluids and food particles inside of a glass vessel and to assess the effect of controlled variables: convection phenomena, heating temperature, immersion fluid, and different food particles. The coefficient was evaluated from the sample temperature as a function of the heating time by two approaches: a lumped parameter method and an analytical methodology. High values corresponded to heating in Newtonian fluids (70-181, 57-248 W/m~2 K), and lower corresponded in non Newtonian fluids (31-169, 28-167 W/m~2 K). Similarly, major heat transfer coefficient corresponded to the heating of mushrooms (32-110, 28-132 W/m~2 K), followed by tomatoes (30-181, 35-183 W/m~2 K) and potatoes (31-148, 34-248 W/m~2 K), respectively. Fluid properties were more important than the thermal properties of the particles. This coefficient was higher at 85 ℃ in both types of fluids. Both methods generated satisfactory values, but the analytical approach showed more accuracy.