Analysis and control of hybrid convection‐radiation drying systems toward energy saving strategy

Food drying is a vital technology in agricultural preservation, where hybrid drying provides efficient moisture removal. However, the transient behavior of the moisture ratio ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>MR</mml:mi> <mml:annotation>${\mathrm{MR}}$</mml:annotation></mml:semantics> </mml:math> ) and associated drying rate ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>DR</mml:mi> <mml:annotation>${\mathrm{DR}}$</mml:annotation></mml:semantics> </mml:math> ) could increase energy consumption if not managed with an effective energy-saving strategy. This study investigates the impacts of hybrid convection-radiation drying on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>MR</mml:mi> <mml:annotation>${\mathrm{MR}}$</mml:annotation></mml:semantics> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>DR</mml:mi> <mml:annotation>${\mathrm{DR}}$</mml:annotation></mml:semantics> </mml:math> , drying time, and energy consumption. Unlike previous studies, which have not fully addressed the connections between operating conditions and drying kinetics, this work provides new insights into these relationships. Additionally, an artificial neural network (ANN) control model is applied to optimize energy consumption, offering a new approach to improving the efficiency of the drying process. During the experiment, the airflow velocity was varied from 0.7 m/s to 1.5 m/s, the airflow temperature was varied from 40°C to 60°C, and the radiation intensity was varied from 1500 W/m² to 3000 W/m². The results showed that the transient behavior exhibited four data groups with consistent <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>MR</mml:mi> <mml:annotation>${\mathrm{MR}}$</mml:annotation></mml:semantics> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>DR</mml:mi> <mml:annotation>${\mathrm{DR}}$</mml:annotation></mml:semantics> </mml:math> through the mean and statistical analysis. Increasing radiation intensity and air temperature has decreased the drying time, while higher airflow has increased the drying time. The energy indices were enhanced by increasing radiation intensity and temperature while reducing airflow velocity. The measured <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>MR</mml:mi> <mml:annotation>${\mathrm{MR}}$</mml:annotation></mml:semantics> </mml:math> of all groups exhibited similar kinetics behavior, while the associated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>DR</mml:mi> <mml:annotation>${\mathrm{DR}}$</mml:annotation></mml:semantics> </mml:math> exhibited similar clustering through the self-organizing map. Those findings were further controlled using an ANN model with 99% predicting accuracy. With airborne heating at 60°C and airflow at 0.7 m/s, the radiation intensity is transiently controlled, showing a 6.5% drying time reduction and a 36% energy saving. Thus, controlling the radiation intensity and its impact on the slice properties is highly desirable in future work. This work could help designers improve the processing efficiency and energy conservation of garlic slices drying.