Effect of Size on the Convective Heat and Mass Transfer Coefficients during Natural Convection Greenhouse Drying of Khoa-A Heat Desiccated Milk Product

Abstract

In this research paper, the convective heat and mass transfer coefficients are evaluated for khoa drying under natural convection greenhouse mode for different sizes of khoa samples for a given mass. The khoa pieces of dimensions 0.025 × 0.02 × 0.015 m 3 , 0.0375 × 0.03 × 0.015 m 3 , and 0.075 × 0.06 × 0.015 m3 with total quantity of 100 g are dried in the roof type even span greenhouse with a floor area of 1.2 × 0.8 m2. The khoa has been dried at atmospheric pressure till there is almost no variation in its mass is recorded. The experimental data are used to determine the values of the constants in the Nusselt number expression by simple linear regression analysis and, consequently the convective heat transfer coefficients are evaluated. The mass transfer coefficients have also been evaluated. The convective heat and mass transfer coefficients are observed to decrease with the increase in size of the khoa sample and are found more for the khoa pieces having dimension 0.025 × 0.02 × 0.015 m3. The experimental error in terms of percent uncertainty has also been evaluated.