Investigation of Specific Heat and Thermal Conductivity of Rasa Grape (Vitis vinifera L.) As a Function of Moisture Content

Kurdistan Rasa grape is beautiful, delicious and black in color. It has some vitamins such as E, C and some protectors such as antioxidant. In order to design equipments and facilities for the drying, preservation and processing of Rasa grape, it is necessary to know about the specific heat and thermal conductivity. Therefore, the objectives of this study were to determine the specific heat and thermal conductivity of Rasa grape and developing mathematical models for their estimation. The method of mixtures and hot wire as a heating source was used for measuring the specific heat and thermal conductivity of Rasa grape, respectively. The effective thermal conductivity and specific heat of Rasa grape were determined as the functions of moisture at 40, 50, 60 and 70°C. The moisture of grape ranged from 22.31 to 71.53%. The results show that the specific heat and thermal conductivity of Rasa grape increased linearly from of 1.6523 kJ/kg°C to 3.3253 kJ/kg°C and 0.1252 W/m°C to 0.4202 W/m°C, respectively with increase in the experimental range of the variables. The effect of moisture content on increasing the specific heat and thermal conductivity is more than that of temperature. Regression equations were established which could be used to reasonably estimation of the values of specific heat and thermal conductivity as a function of specific moisture content and temperature.