Application of Quasi-Heat-Pulse Solutions for Luikov’s Equations of Heat and Moisture Transfer for Calibrating and Utilizing Thermal Properties Apparatus

Abstract

Several years ago the Laplace transform solutions of Luikov’s differential equations were presented for one-dimensional heat and moisture transfer in porous hydroscopic orthotropic materials for the boundary condition of a gradual heat pulse applied to both surfaces of a flat slab. This paper presents calibration methods and data for the K-tester 637 (Lasercomp), allowing use of the mathematical solutions to measure material properties. The K-tester supplies a quasi-heat-pulse to both sides of a 2-ft-square specimen and records signals as function of time from surface thermocouples and thermopiles. Analysis methods are presented that apply to the thermal wave traveling through the FR4 thermopile, copper cladding, a sheet facing (aluminum or particle board), and the test specimen. A heavier, thicker, and expanded polystyrene (PS) foam board traceable to NIST was used as a “standard” specimen for calibrating thermal properties and temperature differential (from thermopile microvolts) for the FR4 thermopile via a specialized “forked” heat pulse profile. The similar heat pulse profile was then used to determine heat capacities and thermal conductivities of a very heavy and pure polystyrene board, Rexolite 1422, and a very light and thinner extruded PS foam board, in basic agreement with independent measurements. In addition, formulae are obtained for heat capacities and thermal conductivities of PS-based boards as functions of density, structure, and temperature. The stage is set for future work for determining heat and moisture transfer properties for a moist wood core between aluminum plate facings.

Citation

Dietenberger, Mark A.; Boardman, Charles R. 2014. Application of Quasi-Heat-Pulse Solutions for Luikov’s Equations of Heat and Moisture Transfer for Calibrating and Utilizing Thermal Properties Apparatus. In: NATAS North American Thermal Analysis Society, September 14-17, 2014, Santa Fe, New Mexico Technical Program of the 42nd NORTH AMERICAN THERMAL ANALYSIS SOCIETY CONFERENCE, paper 135, 2014; 12 p.