Experimental investigation on convective heat transfer coefficient for khoa drying

In this research paper, the convective heat transfer coefficients of khoa were investigated in an open sun and greenhouse drying for natural as well as forced convection modes. The khoa was dried in open sun conditions and in the roof type even span greenhouse with a floor area of 1.2×0.8 m2 in natural and forced convection mode at atmospheric pressure till there is almost no variation in its mass. The experimental data were used to determine the values of the constants in the well known Nusselt expression by simple linear regression analysis and, consequently the convective heat transfer coefficients were evaluated. The convective heat transfer coefficient under forced convection greenhouse drying was found to be higher than the other modes. The convective heat transfer coefficient could be expressed exponentially as a function of the drying time interval. To test the consistency of the models developed for khoa drying, correlation coefficient, and various statistical parameters were also determined. The experimental error in terms of percent uncertainty was also evaluated.