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Offshore oil and gas production in arctic areas is challenging due to harsh environmental conditions. Pipeline burial and trenching in those areas are now one of the prime methods to avoid ice gouge risks and other threats. Thermal management becomes critical when the ambient temperature is low such as the typical seawater temperature on the sea bed. The flow temperature and pressure affect viscosity of the fluid traveling through the pipeline and determines the state of the fluid (single or multiphase). The effect of freezing around oil and gas pipes in the vicinity of permafrost is considered as another concern for flow properties of oil and gas in arctic regions. Theoretical shape factor model has been widely utilized to estimate heat loss from buried pipelines. This study examines the validity of using this method for flow assurance calculations. Several steady state and transient experiments have been carried out to model the heat loss considering different parameters such as burial depth, backfill soil, trench geometries etc. Natural convection can play a significant role in the overall heat loss process from the buried pipeline. The total heat loss increases significantly when the backfill soil is loose or sandy. This paper illustrates the effects of heat conduction and natural convection in the heat loss mechanism from buried pipelines. The outcome of this paper will provide valuable heat loss models based on experimental and numerical analysis results. These outputs can be used largely in petroleum industries for designing pipelines in offshore arctic areas and to mitigate several flow assurance issues (e.g. wax and hydrate formation in the pipeline effectively). The methodology used in this research i.e. analyzing the experimental data with two steps of validation will ensure the validity of the proposed model. Using different parameters such as burial depths, trench geometries, and backfill soil this paper provides an effective model for the offshore pipeline design.

Numerical simulations of heat transfer in two-phase Taylor flows in microchannels have been performed for different film thicknesses. Film thickness has been changed by adjusting surface tension and consequently Capillary number to investigate effects of film thickness on heat transfer processes under constant wall flux boundary condition. As stated in the early literature, film thickness is an important factor in Taylor flow hydrodynamics and governs the ratio between the portion of liquid which is in circulation and the portion which is bypassed through the thin liquid film around gas bubbles. It has been shown that film thickness has to be considered in the heat transfer correlations for this type of flow. Something which has not been considered in previous research.