A Transient Method of Measuring Thermal Contact Conductance Between Metal-Plastic Surfaces

Abstract

The thesis describes a method developed to measure thermal
contact conductance between metal-plastics surfaces by transient
experiments. Published literature contains no comparable transient
experimental technique and no conductance values for metal-plastics
surfaces. Thermal transients set up by a radiant heat flux in two
aluminium alloy rods which sandwich between them a thin sheet of
plastic material are used to evaluate the contact conductance.

Crank-Nicolson's finite difference scheme is used to
evaluate the time-temperature history in a three body composite
system with contact resistance at two interfaces. The details of
the experimental equipment designed and constructed for this work
is presented. Dimensionless groups obtained from the heat conduction
equation, initial and boundary conditions predict the contact
conductance from experimental data and the limits to the accuracy
of the measurements of contact conductance. Optimisation techniques
are used to find the minimum of the sum of squares function formed
by the theoretically predicted and experimentally measured temperature
values. The thermal conductivity of the plastic material is
also evaluated from these measurements.

The thermal contact conductance values obtained by this
method at various applied pressures lie in the range of
40 BTU/hr ft² ºF (227.2 W/m² ºK) to 200 BTU/hr ft² ºF (1136 W/m² ºK)
and the thermal conductivity of the plastic material was 0.1042
BTU/hr ft ºF (0.1803 W/m ºK). This conductivity value agrees with
that given in the literature.

The effects of applied pressure and ambient pressure on
contact conductance are investigated.

Date of Award	1972
Original language	English