Exhaust air recycling is a simple and commonly used technique to save energy when using a dryer. The fixed-bed drying test device with increased efficiency by condensation is a clean and energy-saving drying test device developed by combining exhaust air recycling and condensation dehumidification technology. In this paper, through comparisons with or without exhaust air circulation using the single factor test of drying process parameters and the response surface test of corn drying on this test device to investigate the energy-saving effect and drying characteristics resulting from the novel drying method of increased efficiency by condensation. We drew the following main conclusions: (1) increased efficiency drying by condensation resulted in an energy savings of 32-56% compared with the conventional open hot air drying; and (2) during the increased efficiency corn drying by condensation, the mean energy and exergy efficiencies were within 31.65-51.26% and 41.69-63.52%, respectively, when the air temperature was in the 30-55 °C range, and they were 24.96-65.28% and 30.40-84.90%, respectively, when the air passed through the grain layer at 0.2-0.6 m/s; both of these increased with increasing air temperature, and decreased with increasing air velocity. These conclusions may constitute an important reference for investigating the energy-saving drying process of increased efficiency by condensation and developing relevant energy-saving drying equipment.
Keywords: energy efficiency; energy-saving drying; exergy efficiency; improvement potential rate; increased efficiency by condensation; sustainability index.