Heat transfer coefficients measurement in industrial freezing equipment by using heat flux sensors

Heat transfer coefficients, either for convection or conduction mechanisms were determined by using heat flux sensors coupled to temperature measurement devices. Three distinct pieces of equipment were assessed with respect to their heat transfer capabilities. The dynamic variability of heat transfer coefficients was determined along the processing length of a conduction-convection SuperContact® tunnel and a fluidized bed freezer. The main sources of heat transfer inefficiency were uneven air speed profiles for convection and high thermal contact resistance for conduction mechanisms. Fluctuation of coolant temperature was determined to be the limiting factor in a plate freezer. Simulations either with Tylose® gel (SuperContact® tunnel) or with mashed carrot (plate freezer) were carried out to predict improvement in heat transfer coefficients.