Measurement of Thermal Properties of Mung Bean (Vigna radiata)

Abstract

The thermal properties of mung bean (Vigna radiata) are essential for designing postharvest handling equipment for mung bean processing. The specific heat, thermal conductivity, and thermal diffusivity of mung bean were determined as a function of moisture content and temperature. The specific heat and thermal conductivity were quantified using a specially built vacuum flask calorimeter and thermal conductivity probe, respectively. The specific heat was determined by mixing hot water with a sample maintained at lower temperature and incorporating graphical temperature-correction into the calculation. The thermal conductivity was determined by measuring the temperature response of the sample when heated with a line heat source. The thermal diffusivity was directly calculated from the specific heat and thermal conductivity data. The specific heat and thermal conductivity of mung bean increased linearly from 1.63 to 2.45 kJ kg-1 K-1 and from 0.092 to 0.141 W m-1 K-1, respectively, with the corresponding increase in moisture content from 9.9% to 18.3% w.b. and temperature from 10°C to 50°C. The thermal diffusivity of mung bean changed from 0.659 × 10-7 to 0.752 × 10-7 m2 s-1 with increase in moisture content and temperature. The thermal diffusivity increased with increase in moisture content and decreased with increase in temperature.