The presence of high relative air humidity in regions characterized by a humid climate results in a slow drying process and the rehydration of paddy. To address this issue, the utilization of a liquefied petroleum gas refrigeration system for the purpose of dehumidifying the ambient air has been shown to reduce drying time and enhance the quality of the final product. In the present investigation, the impact of ambient air dehumidification on the quality and moisture reduction of the Hashemi rice variety was examined. The drying of paddy was modeled and optimized using the Response Surface Method, taking into consideration three key factors: temperature (40, 45, and 50 °C), air velocity (1.7, 2.2, and 2.7 m/s), and relative air humidity (70, 80, and 90 %) as the variables in the conducted experiments. The findings of this study revealed that under dehumidification conditions, samples with a moisture content of 6 % exhibited the lowest cracking rate of 2 %. Moreover, the use of liquefied petroleum gas resulted in a 13 % reduction in cracking and drying times, ranging from 22.3 % to 68.9 %, depending on the experimental conditions. Irrespective of whether dehumidification was employed or not, the temperature was identified as the most influential parameter, impacting the experimental responses by 73.29 % and 73.09 % for the non-dehumidified and dehumidified conditions, respectively. Under optimal conditions, a cracking rate of 2 % was attained during dehumidification at a temperature of 40 °C, a relative air humidity of 80 %, and an air velocity of 1.7 m/s, yielding a desirability index of 0.958. The Response Surface Method, when applied in the dehumidification case, displayed an excellent fit between the experimental and predicted data for both the moisture content (R2 = 0.99) and the cracking index (R2 = 0.98). These results demonstrate the efficacy of the refrigeration system that employs liquefied petroleum gas inefficiently drying paddy in humid regions, rendering it applicable in industrial settings.
