The thermohysical properties of gypsum boards containing wax
An Unguarded Thin-Heater Apparatus (UTHA) was used to measure the thermal conductivity (k) and thermal diffusivity ({alpha}) of gypsum boards containing 0, 15, 30 wt % wax (C{sub 18}H{sub 38}) in the temperature range 20 to 50{degree}C (68 to 122{degree}F). Since this wax melts near 28{degree}C (82{degree}F), this combination provides a phase-change material for possible use in building applications. The k-values for gypsum board without wax reported here are independent of temperature and extend the available data to a lower density ({rho}). The k-values agree with data by Malloy but are 17% greater than the ASHRAE Handbook value. The k-values for the gypsum-wax composites are greater than the k-value of gypsum board without wax, increase with wax content, and correlate with a two-phase conduction model by Eucken. The k-value of composites with solid wax is greater than the k of composites with liquid wax. A step-change in heat flux transient technique was used on specimens that were initially isothermal or that had a steady imposed temperature gradient. Analysis of the temperature response of the thin-heater for short-times predicts a temperature rise that is a linear function of the square-root of time. This prediction was verified, and the slope of this relaxation provided experimental values for the product k{center dot}{rho}{center dot}C, where C is the specific heat. Experimental values of C were calculated from experimental values of k and {rho} and compared favorably with literature values of C for gypsum and predictions of C for the composites. Transient tests that heated parts of the specimen through the phase change of wax yielded very large C values. These tests required very long time to reach steady-state. 17 refs., 5 figs., 5 tabs.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- DOE/CE
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5256634
- Report Number(s):
- CONF-8910319-2; ON: DE90004933
- Resource Relation:
- Conference: 21. international thermal conductivity conference, Lexington, KY (USA), 15-18 Oct 1989
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
THERMAL INSULATION
PHASE CHANGE MATERIALS
BUILDING MATERIALS
BUILDINGS
ENERGY CONSERVATION
GYPSUM
THERMAL CONDUCTIVITY
WAXES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM SULFATES
MATERIALS
MINERALS
ORGANIC COMPOUNDS
OTHER ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SULFATE MINERALS
SULFATES
SULFUR COMPOUNDS
THERMODYNAMIC PROPERTIES
320107* - Energy Conservation
Consumption
& Utilization- Building Systems- (1987-)
360603 - Materials- Properties