EFFECTS OF MOISTURE CONTENTS AND TEMPERATURE ON THE THERMAL PROPERTIES OF SOME NERICA VARIETIES RELEVANT TO ITS PROCESSING

Abstract

The thermal properties of NERICA (New Rice for Africa) was investigated on differing moisture content levels and temperatures. The NERICA varieties studied includes; FARO 44, FARO 52, FARO 57, FARO 60 and FARO 61. The variety samples were later categorized into two; NERICA Raw-Paddy and NERICA Parboiled-Milled samples. The thermal properties studied were; thermal conductivity, specific heat, and thermal diffusivity. The thermal conductivity and the specific heat were determined using the thermal conductivity probe method and a digital scanning calorimeter, respectively. The thermal diffusivity was determined from the obtained results of the specific heat and the thermal conductivity. Results indicated that, increase in moisture content and temperature results to increase in the specific heat, thermal conductivity and thermal diffusivity of NERICA varieties and these ranged from 4.245 to 39.976 kJ/kg^oC; 0.042 to 1.403 W/m^oC; and 1.236 x 10^-5 to 5.933 x 10^-5 m²/s respectively for NERICA Raw-Paddy and 7.033 to 81.657 kJ/kg^oC; 0.067 to 1.876 W/m^oC; and 1.413 x 10^-5 to 5.219 x 10^-5 m²/s respectively for NERICA Parboiled-Milled. Bulk density decreased with an increase in moisture contents and temperature and the obtained results ranged from 760.3 to 698.7 kg/m³ for NERICA Raw-Paddy and 720.4 to 652.4 kg/m³ for NERICA Parboiled. Regression analysis were carried out on the thermal properties of NERICA varieties and moisture content, and there was positive correlation between the parameters. There were significant effects of moisture content (p < 0.05) on all the parameters studied.