Determination of thermal properties of six yam cultivars grown in the benue river basin, nigeria

Ijabo, O. J, E. O. Ajayi and M. Bebelede

Thermal conductivity (k), specific heat capacity (Cp) and thermal diffusivity (d) are important properties in modelling, simulation and control of various food processing unit operations. This study, investigates these properties for tubers of six yam cultivars grown in the Lower Benue River Basin, Nigeria. The measurements were done for the head, middle and tail sections of yam in 10 replicates. The yams were first characterized in terms of moisture contents and density. Thermal conductivity was measured using a line heat source probe at the storage moisture contents and temperatures near 30⁰C. The results for specific heat ranged from 1.1157 to 5.3282 Jkg-1⁰C-1 and it is neither significantly affected by the tuber section nor the cultivar so a mean ± standard deviation of 3.5181 ± 0.7516 Jkg-1⁰C-1 value was returned for yam. Both thermal conductivity and thermal diffusivity were not affected by yam tuber section but were affected by cultivar. Consequently conductivity relates as follows: Amula ≤ Agbo (Pan ave) Agbo (Kor) < Gbangu ≤ Pepa ≤ Hemba kwase which in terms of numerical values are 0.2258 ≤ 0.2363 0.2662 < 0.3058 ≤ 0.3230 ≤ 0.3485 W/(m⁰C). A similar relationship for thermal diffusivity is Hemba kwase < Amula < Agbo-kor Agbo-pan ave ≤ Gbangu < Pepa which in terms of numerical values reads: 4.257E-05 < 6.339E-05 < 6.560E-05 6.602E-05 < 9.770E-05. Thermal conductivity and thermal diffusivity of D. alata cultivars are not significantly different from each other.

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