Experimental study on thin layer variable temperature hot air drying of konjac

This paper discussed the effects of variable temperature( 50 → 70 ℃ and 70 → 50 ℃) and different thickness of konjac pieces( 5,6 and 7 mm) on the drying rate of konjac,nine mathematical models were selected to fit the experimental data,the effective moisture diffusion coefficient of konjac was calculated,and the experiments of thin layer variable temperature drying and constant temperature drying were compared. The thin layer variable temperature drying experiments of konjac were conducted through the air velocities( 0.75 m / s) and the thickness of pieces( 5,6 and 7 mm) and air temperature( 50→70 ℃ and 70→50 ℃).The results showed that drying time increased with the addition of the thickness of konjac slices while the other drying conditions were same. And the two- term model was much more adequate for describing the thin layer variable temperature drying of konjac.The values of D_(eff) increased with the addition of the thickness of konjac slices. Under the same condition of the air velocities and thickness,the thin layer variable temperature drying rate was higher than the rate of constant temperature drying,and the results showed that the low-to-high mode( 50→70 ℃) of variable temperature was better.