HEAT AND MASS TRANSFER IN DRYING OF CARROT BY RADIO FREQUENCY ASSISTED HEAT PUMP DRYING

Abstract

This study focused on the heat and mass transfer in radio (RF) assisted heat pump (HP) drying of carrots. The experimental drying of carrot by RF assisted HP drying method was conducted to evaluate the effect of RF power on drying efficiency including drying rate and heating rate. The input drying parameters were drying air temperature of 45 o C, drying air velocity of 2.5 m/s and RF power of 0, 0.5 and 1.5 kW, in which, RF power of 0 was corresponding to HP drying method. The experimental drying results showed that in RF assisted HP drying method, the drying rate and heating rate were improved as compared to HP drying. The drying time was 480, 375 and 335 minutes corresponding to RF power of 0, 0.5 and 1.5 kW. The temperature of drying material reached the drying air temperature in about 25 and 30 minutes corresponding to RF power of 1.5 and 0.5 kW. While in HP drying, the temperature of drying material reached nearly the drying air temperature value in about 310 minutes. Besides, the comparison between the heat and mass equations solving results and experimental drying data was also carried out with the analysis results confirmed that the predicted data by numerically solving the heat and mass transfer equations could be used to predict the experimental data accurately.