Measurement of Specific Heat Using Twin Isoperibol Calorimeters and Estimation of the Effective Thermal Diffusivity of Wheat Flour

Abstract

　The specific heat of wheat flour was measured at four different moisture contents (9～18%) and five different temperatures (10～50℃), using twin isoperibol calorimeters. This type of calorimeter is suitable for specific heat measurements of liquids. In this study, wheat flour samples were added to water, and the specific heat of each sample suspension was determined at each measurement condition. An additive relationship exists between the specific heat of a food material, its composition, and the specific heat of each component. The specific heat of the sample (wheat flour) was determined from the specific heat of the sample suspension using the additive property of specific heats. Furthermore, the effective thermal diffusivity of the sample (wheat flour) packed bed was estimated by substituting the literature data of effective thermal conductivity, the measured data of specific heat of the sample, and the bulk density of sample packed bed. The effects of moisture content, temperature, and bulk density on these thermophysical properties of the sample were investigated, and we proposed predictive models for these properties.