Kinetics and mathematical modeling of thin layer drying of mint leaves by a hot water recirculating solar dryer

Abstract

AbstractThis research was mainly devoted to evaluating the drying kinetics of mint leaves in a newly introduced solar dryer. In order to assess the drying kinetics of mint leaves, nine drying temperature levels (with the average value of: 41.3, 42.2, 44.1, 45.9, 47, 48.2, 50, 51.5, and 53.9°C and a corresponded drying time of 255, 255, 195, 180, 180, 180, 165, 165, and 150 min, respectively) were used. In addition, the corresponded values for the average drying rate levels were obtained as 2.19, 2.33, 2.96, 3.21, 3.35, 3.44, 3.51, 3.57, and 3.84% dry basis/min, respectively. Specific energy consumption of drying was calculated, which varied 5.5 to 8.6 MJ/kg of water removed. Also, 11 semiempirical models were applied to find the best‐fitted thin layer drying model, and an approximation of diffusion model has the highest correlation (R2 = 0.98, root mean square error = 0.041, k2 = 0.0017) with the experimental moisture ratio than the other models. Also, emitted carbon dioxide due to energy production from fossil fuel for usage in the electrical pump was calculated as 0.3 kg of CO2/kg of water removed. Hence, it can be concluded that the introduced solar drying technique is an eco‐friendly apparatus which was successfully used for the drying of mint leaves.Practical applicationApplication of solar for production of heating energy can cause to emit lower CO2, and consequently lower environmental pollution will occur. Hence, apparatuses with fossil fuel consumption can be replaced with this dryer. Also, due to lower air flow and temperature, this dryer can be used for drying of pharmaceutical plants such as mint leaves. Therefore, the introduced dryer has lower specific energy consumption and higher energy performance as a suitable dryer for industrial usages.