Analysis of thermal-probe measurements using
an iterative method to give sample conductivity
and diﬀusivity data
Steven Goodhew, Richard Griﬃths*
Joint Schools of the Built Environment, University of Plymouth, Hoe Centre, Notte Street,
Plymouth, Devon PL1 2AR, UK
Accepted 29April 2003
The application of Microsoft Excel Solver routines to analyze data from a thermal-probe
placed in a number of samples is described. The successful application of the Solver routine to
the thermal-probe temperature time data requires the selection of an appropriate time-inter-
val. The various critical times are discussed and a method proposed for selecting the appro-
priate Solver routine and the time-interval over which the experimental data must be
analyzed. Values of the sample thermal conductivity, the thermal diﬀusivity and the probe to
sample conductance are reported for a stainless-steel probe in unused mineral oil, and paraﬃn
wax and for a copper probe in Magna904 and PTFE. The results for a commercial probe in
agar agree with accepted data for water and the results for a clay–straw mixture demonstrates
the method applied to a good insulator.
# 2003 Elsevier Ltd. All rights reserved.
Keywords: Thermal probe technique; Iterative solution; Conductivity; Diﬀusivity
The Centre for Earthen Architecture, in the University of Plymouth School of
Architecture, is interested in the conservation of earth walls. The Centre has studied
the structural properties: Greer , the pathology, Keefe et al. , the inventoring of
earth buildings using GIS, Ford  and the thermal properties, Goodhew et al. .
Applied Energy 77 (2004) 205–223
0306-2619/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: +44-1752-233605; fax: +44-1752-233634.
E-mail address: rgriﬃths@plymouth.ac.uk (R. Griﬃths).