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E. MURAKAMI, FDA National Center for Food Safety & Technology

The thermal conductivity probe is a versatile and simple device that has gained wide acceptance in food engineering applications. It has been used for measuring the thermal conductivity of a wide variety of materials including powders, liquids, bulk grains, and whole fruit. It owes its popularity to its low cost, ease of operation, and simple design. The thermal conductivity probe is derived from an idealized transient heat transfer model, therefore there are inevitable differences between the real probe and the theoretical model. If designed and used properly, the thermal conductivity probe can be an accurate and practical measurement device with wide-ranging applications. Users of the thermal conductivity probe must be aware of its limitations and the possible errors that can develop in its application. Thus, a standard design and operating procedure must be developed to guide users in its fabrication and application. This paper includes a theoretical derivation of the thermal conductivity probe equation and some experimental and theoretical simulations of parameters that can cause errors in the application of the thermal conductivity probe. An explanation is given of the significance of certain design and operating parameters. Some of the findings in the study are that the time-correction factor is not required and contact resistance does not affect accuracy. The calibration factor is necessary as it compensates for the difference in the thermal masses of the probe and the sample. Errors due to edge effects and convection can be avoided by limiting data analysis to the linear section of the time-temperature plot. The truncation error is minimized by making ? as small as possible.