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Adjustment of Sensor Locations During Thermal Property Parameter EstimationThe temperature dependent thermal properties of a material may be evaluated from transient temperature histories using nonlinear parameter estimation techniques. The usual approach is to minimize the sum of the squared errors between measured and calculated temperatures at specific locations in the body. Temperature measurements are usually made with thermocouples and it is customary to take thermocouple locations as known and fixed during parameter estimation computations. In fact, thermocouple locations are never known exactly. Location errors on the order of the thermocouple wire diameter are intrinsic to most common instrumentation procedures (e.g., inserting a thermocouple into a drilled hole) and additional errors can be expected for delicate materials, difficult installations, large thermocouple beads, etc.. Thermocouple location errors are especially significant when estimating thermal properties of low diffusively materials which can sustain large temperature gradients during testing. In the present work, a parameter estimation formulation is presented which allows for the direct inclusion of thermocouple positions into the primary parameter estimation procedure. It is straightforward to set bounds on thermocouple locations which exclude non-physical locations and are consistent with installation tolerances. Furthermore, bounds may be tightened to an extent consistent with any independent verification of thermocouple location, such as x-raying, and so the procedure is entirely consonant with experimental information. A mathematical outline of the procedure is given and its implementation is illustrated through numerical examples characteristic of light-weight, high-temperature ceramic insulation during transient heating. The efficacy and the errors associated with the procedure are discussed.
Document ID
20020040973
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Milos, Frank S.
(NASA Ames Research Center Moffett Field, CA United States)
Marschall, Jochen
(Eloret Corp. Moffett Field, CA United States)
Rasky, Daniel J.
Date Acquired
August 20, 2013
Publication Date
January 1, 1996
Subject Category
Instrumentation And Photography
Meeting Information
Meeting: 1997 National Heat Transfer Conference
Location: Baltimore, MD
Country: United States
Start Date: August 10, 1997
End Date: August 12, 1997
Funding Number(s)
PROJECT: RTOP 242-80-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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