HEAT AND MASS TRANSFER IN INFRARED ASSISTED HEAT PUMP DRYING OF HOLY BASIL LEAVES $(OCIMUM GRATISSIMUM)$

This study focused on a drying technical problem of heat and mass transfer in infrared radiation (IR) assisted heat pump (HP) drying of holy basil leaves. The experimental drying of holy basil leaves was carried out to evaluate the effect of IR power on drying rate and heating rate of drying process. The experimental drying was carried out with drying air temperature of 45°C, drying air velocity of 2.0m/s and IR power of 0, 300 and 350W, in which, the HP-only drying mode corresponds to drying mode at IR power of 0W. The experimental drying results showed that the drying rate and heating rate of IR assisted HP drying method could be improved significantly due to the support of IR heating mechanism. The drying mode at IR power 350W obtained the highest drying rate with the shortest drying time of 90 minutes, followed by IR power 300W with drying time of 120 minutes and the HP-only drying mode got the lowest drying rate with drying time of 210 minutes. The IR assisted HP drying mode at IR power 350W and 300W attained the high heating rate with the time duration required for the drying material to reach the drying temperature being about 30 and 40 minutes, respectively, while the HP-only drying mode required about 190 minutes for the drying material’s temperature to reach near drying air temperature value. Besides, the heat and mass transfer equations in IR assisted HP drying process have been established and solved numerically by Matlab software. Statistical comparison between predicted data (the results of numerically solving the heat and mass transfer equations) and experimental drying data was also performed. The statistical analysis results affirmed that the predicted data could be used for predicting the experimental data accurately. Received: December 20, 2025Accepted: February 9, 2026