Performance Evaluation and Optimization of a Solar-Assisted Multi-Belt Conveyor Dryer Based on Response Surface Methodology

Drying process is an important post-harvest stage of food crops production which accounts for about ۲۰ % of the world’s energy consumption in the industrial sector. One of the effective ways to reduce the share of fossil fuel consumption in the food drying process is to develop new drying systems based on the use of renewable energy sources. In this research, a novel solar-assisted multi-belt conveyor dryer was developed and its performance was analysed. The required thermal energy for drying process was supplied by the combination of solar-gas water heaters and four solar-powered infrared (IR) lamps. The experimental factors included the speed and temperature of the drying air and the power of IR lamps. The performance characteristics were drying time, Overall Specific Energy (OSE), Non-Solar Specific Energy (NSE), Overall Energy Efficiency (OEE), and Solar-Assisted Energy Efficiency (SEE). The optimization process of the drying system was carried out using Response Surface Methodology (RSM) by defining two general modes for the energy sources of the drying system, namely overall mode and solar-assisted mode. Based on the results, the lowest OSE (۱۷.۳۰ MJ/kg water evaporated) was obtained when the speed and temperature of the drying air were equal to ۷ m/s and ۴۰ °C, respectively, without using IR power. The lowest NSE (۲.۷۱ MJ/kg water evaporated) was achieved by applying the treatment of ۷ m/s * ۴۰ °C * ۳۰۰ W. The maximum OEE was equal to ۱۳.۹۲ % whilst the maximum SEE was obtained as ۸۸.۷۱ %. Both of the mentioned maximum values were obtained at the speed and temperature combination of ۷ m/s and ۴۰ °C and their difference was applying     ۳۰۰ W IR power to gain maximum SEE and no IR utilization for the maximum OEE. According to RSM analysis, the optimum working conditions for the drying system included the treatment of ۷ m/s * ۳۹.۹۶ ºC * ۳۰۰ W. Under this condition, the drying time, NSE, and SEE values were equal to ۱۸۰.۹۵ min, ۱.۰۶۲ MJ/kg water evaporated, and ۸۴.۶۳ %, respectively.

کلیدواژه ها:

Drying ، specific energy ، Energy efficiency ، Solar-assisted dryer ، Solar Water Heater