Date of Award


Degree Type


Degree Name

Master of Engineering Science


Civil and Environmental Engineering


Dr. Tim Newson

Second Advisor

Dr. Anthony Straatman,


Heat transfer from an isothermal pipe buried in porous media and superimposed by a fluid layer has been investigated numerically using the commercial software FLUENT (6.3.26). Due to natural and induced heterogeneity, soils have variations in their hydraulic and volumetric properties; these must be considered for accurate design purposes. Two types of porous media have been investigated, sand and clay. For sand media, the study investigates the effects of different flow and geometric conditions on the heat transfer process. The flow parameters are represented by the Rayleigh number, the permeability ratio of the backfill to the seabed and the permeability anisotropy of the backfill, while the geometric parameters are represented by the trench size and shape and the position of the pipe in the trench. For clay media, two states of the backfill were investigated; these are slurried and lumpy clays. The study also shows the impact of the different trenching conditions on insulation of the pipe as opposed to expensive coating. Lowest heat losses were achieved for a sand backfill of a permeability 100 times the permeability of the seabed and permeability anisotropy of (Kth/Ktv=50). Clay slurry backfill gave the lowest heat transfer results as the main mode of heat transfer in this case was conduction. In contrast, the high permeability and intergranular porosity of clay lumps, allowed for pure convection heat transfer. It was also noticed that clay lumps of sizes 5 and 10 cm allowed for more heat losses than for a pipe with no backfill at all.



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