Experimental Measurement Of Physical Parameters Of Paddy

The thermal property parameters of paddy grains play an important role in the computer simulation of drying, the design of drying technologies and calculation of heat transfer in the storage of paddy grain. In past decades, domestic researchers carried out little research on the thermal parameters of paddy and had to cite the data from oversea in their research works. However, except for these factors such as moisture content and temperature, the breed and growing area environment of paddy grain also have, despite slightness, certain influence upon thermal property parameters of paddy grains. As a result, a deviation would occur when the data from abroad were adopted for the native paddy drying. Therefore, it is very important and necessary to conduct studies on measure of thermal property parameters of paddy grains growing our country.The main objectives of this study were to determine the thermal property parameters of the short paddy, No.3 Wuyujing, growing in South China. Special attention was focused on investigating the effect of moisture content of paddy on its heat capacity, thermal conductivity and thermal diffusivity.CSK-1 type of hydrothermograph was used for the measurement of heat capacity .The results show that the heat capacity of paddy will rise with an increase in the moisture content. The relationship between the heat capacity and moisture content(wb) is governed by following expression:cs =0.1227w-0.4378A ting heat probe was employed for determination of the thermal conductivities of paddy with different moisture contents.When a ting heat probe is used to measure thermal conductivities of the loosing materials such as the grains, a small temperature rise of the surface of heat probe will cause little change of properties of grains. As a result, the testing results would be quite accurate. In this paper, the author eliminated the error resulted from the temperature un-uniformity of heat probe by unifying the heating device and the thermotector. Based on multi-points measurement and the calculation of slope of regressive curves, the relative accurate thermal conductivities of paddy with different moisture contents were obtained. In addition, theexperimental results show that the thermal conductivities of paddy will rise with an increase in its moisture contents and their relationship can be described as following:In terms of the theory of transient heat-transfer of cylinder, the determination of the thermal diffusivity of short paddy were carried out The studies indicated that, in the temperature from 20 to 80癈, no linear relationship exist between the moisture content and thermal diffusivities of short paddy grains with moisture contents from 6.48% to 19.8% and in the confidence 95%, the thermal diffusivity of short paddy grains follow the expression: a =0.146 + 0.003 m2/s.The comparion of measured thermal diffusivity of paddy with those from heat capacity, thermal conductivity and density show that although there are differences between the tested data and the calculated one, they change in almost the same range. This imply the testing result of thermal conductivity, thermal diffusivity and heat capacity of paddy were reliable.