Thermal properties of Jatropha curcas L. kernels

The thermal properties of Jatropha curcas L. kernels, including thermal diffusivity and conductivity were studied where kernels in 3 different forms were investigated, i.e. whole kernels, ¼ kernels and kernel powder. The specific heat of kernels in 2 different forms was also assessed (i.e. small piece of kernel and powdered kernel). The experiments were undertaken using kernels obtained at 2 different harvesting periods, a mature, ripe stage (yellow fruit) and a fully ripe stage (black fruit). The thermal diffusivity of whole kernels, ¼ kernels and kernel powder obtained from yellow fruit were 9.303 × 10−6, 8.370 × 10−6 and 7.456 × 10−6 m2 s−1, respectively, while those obtained from black fruit were 8.792 × 10−6, 7.723 × 10−6 and 6.652 × 10−6 m2 s−1, respectively. The thermal conductivity of whole kernels, ¼ kernels and powdered kernels increased with increasing temperature from 25 to 100 °C, ranged from 0.0663 to 0.1181, 0.0593 to 0.1087 and from 0.0536 to 0.1015 W m−1 °C−1 for the 3 kernel forms derived from yellow fruit, respectively. For the different kernel forms obtained from the black fruit the corresponding values were 0.0608–0.0977, 0.0527–0.0841 and 0.0452–0.0740 W m−1 °C−1, respectively. The specific heat of the small piece kernel and powder obtained from yellow fruit, ranged from 0.7852 to 1.3929 and from 1.3823 to 2.4510 kJ kg−1 °C−1, respectively. For black fruit, the values ranged from 0.6258 to 0.9933 and from 0.8930 to 1.7810 kJ kg−1 °C−1, respectively. Linear relationships between thermal conductivity and specific heat with temperature are reported.

► The thermal properties of Jatropha curcas L. kernels were investigated for the first time. ► Thermal diffusivity and thermal conductivity increased with particle size but decreased with ripeness. ► Thermal conductivity and specific heat linearly increased with temperature (25–100 °C). ► The specific heat decreased with particle size and ripeness.