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Optimization of the temperature sensor position in a hot wire probe set up for estimation of the thermal properties of foods
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 016089, 2001 ASAE Annual Meeting. @2001
Authors: H.B. Nahor, N. Scheerlinck, J.F. Van Impe, B.M. Nicolaï
Keywords: Heat transfer, Finite element, Parameter estimation, Optimal experimental design, Hot wire probe, Modified E-Criterion
For successful design and simulation, accurate knowledge of thermophysical properties of food
products is essential. When considering conduction heat transfer, the involved thermophysical
properties are the thermal conductivity and the volumetric heat capacity. Recent interests are
directed towards simultaneous determination of the thermophysical properties. In this context,
the quality of the experimental data is crucial in order to estimate the parameters accurately and
The objective of this paper is to determine the optimal measurement position with respect to the
information content of an experiment in a hot wire probe set up given an input heat generation.
Moreover, the influences of different parameters of the input heat generation profile such as the
magnitude of the heat generation and final time with respect to the optimal sensor location were
To achieve this objective, a simple experimental set up has been developed using the line heat
source method. A constantan heating wire is impeded in a stainless steel hypodermic needle and
a thermocouple is placed at some point in the model food substances (Tylose and Agar gel) to
measure the temperature. The heat conduction in the probe and its environment was modeled by
means of the finite element method and the model has been validated using experimental data.
For a given type of heat generation profile, the influence of the sensor location with respect to
the information content of the experiment has been investigated by using an optimal design
criterion based on the Fisher information matrix.
Simulations indicated that there is an optimal position where the time-temperature measurement
should be recorded in order to have an informative experiment such that the parameters are estimated accurately and uniquely. Moreover, it was observed that the choice of magnitude of
heat generation and final time have no significant influence on the information content.
Implementation results confirmed that by using the time-temperature data measured around the
optimal position, unique and accurate estimates could be obtained.