HEAT BALANCE OF COMBINED HEAT EXCHANGER USED IN AERODYNAMIC HEATING DRYERS

Abstract

One of the promising methods of drying raw fruit and berry materials is the use of aerodynamic heating dryers that transform electric energy spent on a centrifugal fan drive into heat energy due to the mutual friction of air flows circulating in a closed chamber. To reduce the energy intensity of the drying process, the authors propose to utilize the heat of the used drying agent by equipping the dryer with a combined heat exchanger. To predict the thermotechnical characteristics of the combined heat exchanger depending on variable external factors, based on the heat balance equation, the authors determined the theoretical relationship between the drying agent temperature at the outlet of the combined heat exchanger and the dryer operating time. The presence of an air solar collector in the combined heat exchanger allowed increasing the temperature of the drying agent at the outlet by another 10°C without additional electric energy costs. A comparative analysis of the results of experimental and theoretical studies has shown their high convergence.