Thesis Abstract

Majority of small scale farmers and homes are still using open-sun and/or non-convective methods for drying due to either high cost of gas/electric dryer or lack of electricity in their locations. These methods are time consuming and exposed the products to rain and contamination. A maintenance-friendly and properly enclosed dryer is therefore desired. The batch kerosene heated dryer was studied and adapted to suit the need of these people. In this work, the heat and mass transfer analysis of potato drying in a batch kerosene heated oven is considered. The analysis concentrates on the drying chamber of the system. First, the reasons for and working operations of the dryer were considered. The temperature of the drying chamber was maintained constant (130oC) and sample thickness was varied in two levels (0.005m and 0.01m). Fick’s diffusion model (among others) was modified and used as a major equation to predict the effective moisture diffusivity (Deff) of the sample during the drying period. The model was developed to describe the heat and mass transfer of the material in the dryer; based on some assumed conditions. The experimental drying curves showed only a falling drying rate period. The analysis and validation proves that the model could be used to predict the particle moisture content and temperature profile, the average temperature of particles, the heating rate, the activation energy (Ea) etc during the drying process. Comparing the predictions of the conventional Fick’s model proposed in this study with the experimental data shows that the temperature variation of sample during the drying has a strong influence on the prediction of the drying model.

Thesis Overview