Experimental investigation and empirical correlations of thin layer drying characteristics of seedless grapes

An analytical model for a grapes drying chamber based on the energy balance equations for the drying air and the drying product is presented. The drying constant (k) is determined from the drying experiments of the seedless grapes. The characteristic constants c and n in Henderson's equation are also obtained using the experimental results. The empirical values of the constants K, n and c are employed for calculating the system thermal performance such as the temperature distribution and drying curves. This work presents two empirical equations for the equilibrium moisture content (M e) and the latent heat of vaporization (L) of the grapes. A test rig has been designed and constructed to obtain the experimental data used to derive the empirical equations. These two formulae are very important to evaluate the drying rate of the grapes at particular conditions and also to calculate the correct values of the latent heat of grapes as a function of the equilibrium moisture content