Specific Heat, Thermal Conductivity and Thermal Diffusivity of Red Lentil Seed as a Function of Moisture Content

Thermal properties of red lentil seeds, including specific heat, thermal conductivity and thermal diffusivity in the moisture content range of 9.5–21.1% (w.b) were determined. The specific heat was measured using method of mixtures and found to be between 1.08 and 2.03 kJ/kg·K as the moisture content increased. The thermal conductivity of seed increased from 0.191 to 0.241 W/m·K by increasing moisture content (P < 0.05). This relationship has been established in the form of a second-order regression equation. Moreover, the thermal diffusivity computed from the values of thermal conductivity, specific heat and bulk density showed polynomial decrease from 2.15 × l0−7 to 1.65 × 10−7 m2/s in the specified range of moisture content (P < 0.05). Determination of these characteristics is practical in modeling thermal behavior of red lentil seeds during thermal processing operations, such as frying, drying and baking. Practical Application Thermal properties of agricultural materials and foods need to be known to better understand their nature and to be able to develop new technologies. Knowledge of thermal properties is important for mathematical modeling and simulation of heat and moisture transport. However, the moisture content significantly affects different thermal characteristics. The presented models and equations in this study allow engineers to predict these properties, thus saving time, material and cost.