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The article contains the results of research on transient heat and mass transfer processes occurring in a honey dehydrator with the capacity of 30 kg of honey with closed air circulation with volumetric flow rates Va = 0.01–0.03 m³s−1. The research was carried out different rotational speeds of the honey mixer ns = 120-270 rpm, without and with preheating of the honey. The article presents heat and mass balance equations for the considered process of honey dehydration, the values of heat transfer and mass transfer coefficients between honey and air were determined. The values obtained are respectively α = 5-25 Wm−2 K−1, β = 0.001–0.035 kg m−2s−1. The reduction of mixer speed from ns = 270 rpm tons = 120 rpm was accompanied by an increase in average heat and mass transfer coefficients of approx. 30% and 52%, respectively. The tripled volumetric flow rate of air(Va1/Va2 = 3) resulted in an increase in heat and mass transfer coefficients – on average by 80% and 140%, respectively. Preheating the honey allows to increase the amount of removed water by 30%. The paper presents the general dimensionless expressions allowing for the calculation of heat and mass transfer coefficients. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model of the heat and mass transfer processes for a rotary-spray honey dehydrator with a heat pump and a closed air circuit. An analytical calculation model, based on the energy balance equations of the dehydrator and heat pump, was used to model the transient dehydration process of honey in a dehydrator. The presented article includes a different approach to modelling both the dryer and the heat pump assisting the drying process. The novel quality of this study lies in the use of original equations to determine the heat and mass transfer coefficients between honey and air and using an actual model of a cooling unit to model the honey dehydration process. The experimentally verified calculation algorithm enables an analysis of the effects of air flow rate, mixer rotation speed, and cooling unit power on the efficiency of the drying process. The dehydrator calculation model was used to minimize the drying time by selecting the optimal evaporative temperature values of the cooling unit. For fixed mixer speed and air flow rates, optimal values of evaporation temperatures allow for 8–13% reduction in honey drying time and an increase in the specific moisture extraction rate (SMER) by 4–32%. [ABSTRACT FROM AUTHOR]