Effect of size on forced convection greenhouse drying of khoa

Abstract

Khoa, a heat desiccated milk product, forms an important base for preparation of milk sweets. In this communication, an attempt is made to evaluate the convective heat and mass transfer coefficients during forced convection greenhouse drying of different sizes of khoa samples. Experiments were conducted during the month of October 2012 at Guru Jambheshwar University of Science & Technology Hisar. Khoa pieces of different dimensions with a total quantity of 100 g were dried in a roof type even span greenhouse with a floor area of 1.2 × 0.8 m 2 till almost no variation in its mass was recorded. Hourly data on the mass evaporated, temperature of khoa, relative humidity and temperature inside the greenhouse structure were recorded. These data were used to determine the values of convective heat transfer coefficients by regression analysis, and the convective mass transfer coefficients were consequently evaluated. The convective heat and mass transfer coefficients were observed to increase with the decrease in khoa sample size for the given size of greenhouse. The experimental error in terms of percent uncertainty was also evaluated, and observed to vary in the range of 14.99% to 23.24%.