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High energy consumption and low thermal efficiency are the main problems associated with convection hot air dryers. The effect of various energy sources on tomato drying in a convective dryer was performed. In particular, drying experiments were performed on a convection dryer at two types of heat energy sources, electric and butane-gas, air velocity 1.0, 1.5, and 2 m/s, and air temperature 40, 50, and 60 °C. The rising temperature from 40 to 60 °C caused a reduction of the drying period by 24.8, 22.1, and 21.5% at 1.0, 1.5, and 2.0 m/s, respectively. Minimum energy consumption of 3.83 kW.h was recorded using the electrically heated system while minimizing energy consumption of 0.82 kW.h was detected for the convection gas dryer at 60 °C and 1.0 m/s. The lowest SEC was recorded at 17.44 kWh/kg using gas dryers, while a maximum SEC (112.05 kWh/kg) was observed at the electric dryer under 60 °C and 2.0 m/s. The gas dryer had a thermal efficiency ranging from 50.32 to 78.77%, while the electrically heated dryer had a thermal efficiency ranging from 34.86 to 50.34%. Moreover, applying the butane gas as a heat source for drying had various advantages over the conventional electric system, such as less overall energy consumption with more effectiveness under all conditions.
Hany S. El‐Mesery (Thu,) studied this question.