Effect of infrared power and intermittency ratio on combined infrared-convective intermittent drying of banana

Abstract

This work compared continuous and intermittent combined infrared-convective drying of banana using the response methodology surface by desirability function approach. The effectiveness of the drying process concerning the energy performance, CO₂ emission, and the resistance to moisture transfer were reported and discussed. Experiments were performed according to a 3² factorial design taking infrared power (P) (118, 178, and 238 W) and the intermittency ratio (α) (0, 0.333, and 0.667) as independent factors. It was found a reduction in the drying time by 79 % (for α = 0.333) and 74 % (for α = 0.667) when the IR power increased from 118 W to 238 W. Optimal operating condition was obtained for P = 216 W and α = 0.289 which a 'very good' global desirability was achieved, corresponding to a final moisture content of 12.19 % (w.b.), 17.80 kWh/kgH₂O SEC, and 8.89 gCO_2,eq. The effective moisture diffusivity ranged from 2.88 × 10⁻⁹ to 2.41 × 10⁻⁸ m²/s. The resistance by diffusion was greater than the vapor convective one. The conventional drying gave resistance to diffusion of about 1.33 times higher than the intermittent drying with α = 0.333. The net energy for intermittent drying was higher which reinforces its superiority in terms of an energy-effective process.