Heat transfer characteristics and drying kinetics of hematite thin layer during hot air convection

Heat transfer characteristics and drying kinetics of the hematite thin layer during hot air convection based on a lab-scale setup were examined at seven temperatures (100, 110, 120, 130, 140, 150, and 160 degrees C). Four periods during the drying process were detected, a warm-up period, a constant rate period, the first and second falling rate periods. Two isothermal temperature stages were captured during the hot air drying. The average heat transfer coefficients of the whole drying process increased by 28%, 40%, 49%, 56%, 61% and 66% as the hot air temperature rising from 100 to 110, 120, 130, 140, 150 and 160 degrees C. The effective moisture diffusivities of the hematite thin layer were from 8.37 x 10(-9) to 2.05 x 10(-8) m(2) s(-1) for the first falling rate period, and from 1.24 x 10(-8) to 4.06 x 10(-8) m(2) s(-1) for the second falling rate period. The isothermal temperature increased with the elevated hot air temperature, which increased by about 56% as the hot air temperature rose from 100 to 160 degrees C.