The ultimate goal of this research was to determine the feasibility of measuring thermal conductivity of food materials using the bead thermistor with particular reference to high temperature.
Feasibility was established by examining the effects of the input parameters and the measurement error associated with them on the ability to estimate the test medium thermal conductivity test medium. This study showed that estimation of effective radius and bead thermal conductivity, the probe parameters, had the most significant impact on the ability to estimate the thermal conductivity of food materials. The probe parameters were determined by standardizing the thermistor probe against materials of known thermal conductivity. The current lack of well defined thermal reference materials in the range of water and most food products is a primary source of error associated with the method.
The accuracy and coefficient of variation of the Bead Thermistor Method were statistically documented in 10° increments over the temperature range of 25°C to 125°C. These results showed the method to have better than 10% accuracy across the entire temperature range. Distinct differences in accuracy between probes at a given temperature were also discovered. Standardization with water and castor oil resulted in a more accurate method than was achieved using water, castor oil, and glycerin.
The minimum particle diameter necessary to maintain the infinite boundary condition assumption required by heat transfer theory was found to be >5 mm.
The methodology was evaluated by examining the effects of temperature on the thermal conductivity of milk of different fat contents. A prediction equation for each product was attempted from the experimental data, but the data appear best fit by assuming a constant value across temperature. Heat altered the product physically which likely affected temperature dependence.
Based on the results of this study, the bead thermistor method can be considered a practical method for determining thermal conductivity of food materials over the temperature range considered in this study. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/54223 |
| Date | January 1989 |
| Creators | Kravets, Robert R. |
| Contributors | Food Science and Technology, Diehl, Kenneth C., Larkin, J.W., Lopez, A., Byler, R.K., Marcy, Joseph E. |
| Publisher | Virginia Polytechnic Institute and State University |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | xvi, 152 leaves, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 20438571 |
Page generated in 0.002 seconds