Heat and mass transfer properties of longan shrinking from a spherical to an irregular shape during drying

The heat and mass transfer longan shrinking from a regular spherical shape to an irregular shape during combined microwave with hot air drying (MHD) was investigated. The heat and mass transfer coefficients equations for a spherical shape were modified using modelling and experimental data. A moisture diffusivity equation as a function of temperature and moisture content was also developed. A microwave based heat absorption equation was developed without using conventional microwave properties. The root mean square of errors (RMSE) between predicted and experimental data were 0.070–0.093 d.b. and 1.41–4.81 °C for average moisture content and longan temperature, respectively. Sensitivity analysis of the estimated parameters for the nonlinear equations indicated that global optimum values were determined.