Estimation of Thermal Migration around Buried Coolant Ducts with Engineered Backfill Material

Abstract

During designing of centralized air-conditioning system, it is a usual practice to lay out the ducts carrying liquids at lower temperature under the ground surface. The design guideline is stringent about the heat loss from the protective sheath around the coolants and it is expected that, the encapsulating geomaterial around the protective casing should be of lesser thermal conductivity. This will ensure minimal heat loss, thus increasing the effective performance of the air-conditioning system. In view of the above, this present investigation is pertaining to performance assessment of pond ash, a locally available waste material for its suitability as an engineered backfill around the buried cooling systems. The paper makes use of a correlation derived using a recently developed artificial intelligence technique, functional network (FN) approach from the literature data to estimate thermal resistivity of pond ash from its experimentally evaluated electrical resistivity. Electrical conductivity of the material of interest is determined using a fabricated electrical probe. Furthermore, a numerical analysis for thermal migration around the cooling system is realized in a commercially available finite element environment, ANSYS. It is demonstrated that, pond ash can indeed act as a suitable engineered backfill in this regard.