Thermal and physical properties of shallots (Allium cepa L. var. ascalonicum)

Abstract

The purpose of this study was to analyze the thermal and physical properties of shallot (Allium cepa L. var. ascalonicum). The thermal and physical properties are density, thermal conductivity, specific heat, and thermal diffusivity. The methods of determining density, heat conductivity, and specific heat, were using the Archimedes principle, the transient method with probe and the mixture method, respectively. Thermal diffusivity was determined by numerical analysis of the cooling temperature of shallot. Mathematical equations of these physical and thermal properties at various water contents have been obtained from the results of this study. Based on the results of measurements, it was obtained the value of the apparent density of shallots of 929.67 kg/m3 and the bulk density of shallots 767.2 kg/m3. The value of thermal conductivity of shallot leaves ranged from 0.529 W m-1 K-1 to 0.758 W m-1 K-1, and the thermal conductivity of shallot bulbs was 0.841 W m-1 K-1 to 0.991 W m-1 K-1. The specific heat was 3530.5 J g-1 °C. Based on the numerical analysis of Fourier series of cooling temperature data, the thermal diffusivity value of shallots of 4.868 × 10-8 m2/s was obtained.