Transient method for rapidly measuring thermal conductivity and diffusivity of salt mine core samples (the plane probe)

A plane probe technique was developed to measure the thermal conductivity (k) and thermal diffusivity (..cap alpha..) of 7.5-cm dia core samples for the Geologic Disposal Evaluation Program. This plane probe was formed by sandwiching a spiral planar heater between a specimen of known k and ..cap alpha.. (NBS gum rubber) and a specimen of unknown k and ..cap alpha.. which was instrumented with a thermocouple. The probe was interfaced with a PDP 8 computer for exact computation of k and ..cap alpha... A controlled amount of power was supplied to the heater and the thermocouple response recorded for the duration of the power application (approx. 100 s). Reliable results were obtained with a rise in specimen temperature of 1 to 2/sup 0/C. NBS gum rubber, Pyroceram Code 9606, and lavite were used to study variables. The plane probe method yielded a k value within 1% of the NBS value for gum rubber and Pyroceram and within 3% of their ..cap alpha..-value for Pyroceram. The range of applicability is approximately 0.0007 to 0.2 cm/sup 2//s for ..cap alpha.. and 0.001 to 0.04 W/cm . /sup 0/K for k. (DLC)