Abonnement à la biblothèque: Guest

ISSN Online: 2377-424X

ISBN Print: 0-89116-130-9

International Heat Transfer Conference 6
August, 7-11, 1978, Toronto, Canada

SIMULTANEOUS DIFFUSION OF HEAT AND MOISTURE THROUGH ISOTROPIC POROUS MEDIA WITH VARYING PHYSICAL PROPERTIES

Get access (open in a dialog) DOI: 10.1615/IHTC6.20
pages 323-328

Résumé

A general theoretical model describing the heat and moisture diffusion around a cylindrical heat source in a partially saturated isotropic porous medium is developed which takes into account the variation of physical properties of the medium with moisture and temperature. The theory is applied to the case of an e.h.v. transmission cable in a sand backfill for which relevant thermal and hydraulic properties have been evaluated.
Initially the model is used to examine the relative importance of these properties. It is clear for example that thermal conductivity predominates and that its precise evaluation, especially at low moisture contents, is necessary for meaningful predictions of temperature and moisture change.
The results of a laboratory cable-simulation experiment and of a full scale field trial are presented. Laboratory measurements of temperature transients showed agreement to within 7% of the predicted values for radii up to 4.5 of the cable radius. Comparison with field data over the long term (7.106 s) showed agreement generally well within 10% near the cable surface.
Finally, the variable property solution is applied to a typical cable problem in which the thermal performance of the surrounding backfill, when the cable is subjected to a short-term overload condition, is examined.