Analytical method for on-line determination of thermal properties of materials in an absorption calorimeter
Abstract
A Microsoft FORTRAN 77 computer program for on-line
determination of thermal properties (absorptance a and emittance E)
of materials has been developed. It uses data from sample heating
and cooling histories obtained in an absorption calorimeter by
Mulwa G.W (1991). The calorimeter is a box chamber having a window,
sample holder, tungsten halogen lamp and a microcomputer with
instrument interface to control the opening and closing of the
shutter window. It is automated with a Z80 microprocessor system,
which has an operating system (OS) and control programs resident in
a block of type 2716 EPROMS with a working memory comprising type
HITACHI 6116 static RAMS. The Z80 ~P system acquires the data from
the sample through thermocouples, filters, amplifiers and analogueto-
digital signal converters (ADC) for temporary storage in the onboard
RAM. Analytical solutions of heat balance equations of the
calorimeter are computed for the data using numerical methods.
Newton's iteration procedure for systems of nonlinear equations is
used with the assumption that these properties are constant in the
temperature range considered (20°C - 60°C). Computed values of the
properties are substituted into the analytical equations for
verification of temperature history. The IBM PS/2 model 50z
microcomputer has been used for data processing and display of
results. Results obtained for commercial copper and aluminium
samples compare well with those computed by other methods
Citation
Master of ScienceSponsorhip
University of NairobiPublisher
Department of Physics, University of Nairobi