Thermophysical Properties Research Laboratory, Inc.
Phone : 765-463-1581
Step Heat Apparatus
The Step Heat Method is a transient measurement, that is a variation of the pulse heating method. It can be used
for measuring the thermal conductivity of materials which have
a grain size too large to be a laser flash sample. There are several possible ways of conducting an
experiment. One method involves subjecting one face of a specimen to a constant and uniform heat
flux and recording the surface temperature response on the opposite face. A second methodology entails putting two
pieces of the sample material together with a thermocouple between them and on both ends to measure the boundary
conditions. Then, by measuring the temperature response to a changing heat flux, the diffusivity can be calculated.
Another variation is to heat one end of a thin strip or film and measure the temperature response at three locations
along the strip to determine the in-plane thermal diffusivity.
The sample holder consists of two end rings aligned on threaded rods. There are sample mounts on the inside side
of each end ring. The threaded rods allow the position of the rings relative to each other to be changed through
the use of nuts. There is a ceramic furnace that the sample holder slides into. The furnace can heat the sample
up to about 900°C. The heater is in a bell jar that can be vacuumed out and allows for a variety of atmospheres
that can be reintroduced to do the measurements in. Liquid N2 can be run through the system to cool the sample down
to -90°C. Additionally there is a ceramic furnace that can be used to heat the sample up to 1000°C in air.
A 50W bulb is used as the input heat flux. The time temperature response is sampled by a N1, 24-bit Thermocouple
Input Module using Chromel-Alumel thermocouples. Digital data acquisition is controlled by a PC.
Copyright 2011 TPRL, Inc.
3080 Kent Avenue
West Lafayette, IN 47906
Last updated 1/5/2012