Document Type : Research Paper
Abstract
To design equipment and facilities to dry, preserve and process pomegranates, it is necessary to know their specific heat and thermal conductivity. The objectives of this study were to determine the specific heat and thermal conductivity of pomegranates and develop mathematical estimation models for them. The effects of moisture content (15-75% w.b.) and temperature (5-20°C) on the thermal properties of pomegranates (Alak variety) were studied. Specific heat was measured using the mixtures method. The thermal conductivity was measured using a line heat source probe for pomegranate exocarps and mesocarps and the bare-wire transient method for the seeds. The results showed that an increase in moisture content and temperature produced a linear increase in the specific heat from 1.127 to 2.789 kJ/kg°C for seeds, 0.931 to 3.066 kJ/kg°C for mesocarps, and 1.516 to 3.411 kJ/kg°C for exocarps. Thermal conductivity increased from 0.1524 to 0.4218 W/m°C for seeds, 0.148 to 0.451 W/m°C for mesocarps and 0.131 to 0.4204 W/m°C for exocarps as moisture content and temperature increased. However, the effect of moisture content was greater than the effect of temperature on specific heat and thermal conductivity. The empirical equations for these thermal properties were subsequently expressed as a function of moisture content and temperature.
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