Offshore production fluids from the reservoir are often transported in pipelines from the wellheads to the platform and from the platform to process facilities. At low flow velocity water, sand or liquids like condensate could settle at the bottom of pipelines that may lead to grave implications for flow assurance. During shutdown the settled heavy liquid (e.g. water), could result in corrosion in pipelines, while following restart stages the settled water could form water plugs that could damage equipment, while settled sand could also form a blockage that needs to be purged. Furthermore, there is a requirement to know the quantity of water and base sediment for fiscal metering and custody transfer purposes. A series of experiments were carried out to observe low water cut in oil and water flows in four inch diameter pipeline. Similarly low sand concentrations in water and sand, water, air and sand flows were observed in two inch diameter pipelines. Conductive film thickness sensors were used to ascertain structural velocities, height and dense phase fractions. Comparisons are made between two cases in order to gain better understanding of the behaviours and dispersal process of low loading denser phase in multiphase flows. The arrangement enabled production of flow regime maps for low water cut oil and water flow, as well as water sand and water, air and sand flows, structural velocities and denser phase removal velocities were also ascertained. Actual in-situ liquid velocities were obtained experimentally. A novel detection of sand in water and water and sand flows was produced. The experimentally obtained film thickness was in agreement with two fluid model predictions. Thus, confirming use of conductive sensors for dense phase classification, film thickness, velocity and holdup measurements in pipelines.

L’objectif de ce travail consiste en l'étude expérimentale et la modélisation du comportement thermo-hydraulique d'un fluide frigoporteur diphasique (FFD) particulier : le coulis de paraffine, en écoulement dans un canal rectangulaire simulant un échangeur à plaques. Les coulis de paraffine sont constitués de particules millimétriques de paraffine, stabilisées dans une matrice poreuse el mises en suspension dans de l'eau. Les particules de paraffines sont composées de 75% en masse de Norpar®15 et de 25% de polymère tri-block qui sert à gélifier la paraffine. Les résultats expérimentaux issus de bilans sur les veines d'essai de l'installation développée el mise en place au Centre de Thermique de Lyon (CETHIL), mettent en évidence une intensification importante du coefficient d'échange thermique, due a la présence des particules dans le fluide porteur. Pour un écoulement laminaire du coulis de paraffine dans le canal de refroidissement, une multiplication moyenne par 1 ,25 à 1 ,5 du coefficient d'échange global par rapport au fluide monophasique a été enregistrée pour des fractions massiques en particules de 6 à 12 %. Par régression linéaire des résultats expérimentaux, des corrélations pour le calcul des nombres de Nusselt local et moyen sont proposées. Une approche théorique basée sur le modèle de mélanges (Mixture Mode!) a été élaborée pour étudier le comportement hydraulique et thermique du fluide frigoporteur diphasique FFD pendant son refroidissement en écoulement laminaire dans un canal rectangulaire. L'évolution des valeurs expérimentales et théoriques pour la température moyenne du fluide et le coemcien1 d'échange thermique paroi - fluide montrent qu'ils sont en bon accord. Le modèle peut être considéré comme satisfaisant car les écarts entre résultats théoriques et expérimentaux n'excèdent jamais 14 %. / This work concerns the experimental investigation and modelling of the thermo hydraulic behaviour of a new Iwo-phase secondary refrigerant, the paraffin slurry, flowing through a rectangular channel of a heat plate exchanger type. The paraffin slurries are made of millimetric bullets of paraffin, stabilized in an organic porous polymeric matrix, in suspension in water serving as a carrying fluid. The paraffin particles used contain 75% of paraffin called NORPAR®15 and 25% of a tri-block polymer of styrene with High Molecular Weight (HMW). The experimental results generated by the heat balances on the test sections of the experimental setup built in the Thermal Center of Lyon (CETHIL), highlight an important increase of the heat transfer coefficient, due to the particles presence in the carrying fluid. For a laminar flow of the paraffin slurry in the cold channel, an average multiplication by 1 .25 to 1.5 of the global heat transfer coefficient compared to the single-phase fluid was recorded for particles mass fractions of 6 to 12%. By regression of the experimental results, correlations for the local and average Nusselt number calculation for the laminar flows are proposed. The particularity of the presented correlations is their validity in the case of a pure fluid as we\l as for a two-phase fluid containing so\id particles. A model for the hydraulic and thermal behaviours studies of a Iwo-phase secondary refrigerant fluid during its cooling in laminar flow through a rectangular channel was developed it is based on the mixture model and to king the slip velocity into account. The evolution of the experimental and theoretical values for the fluid average temperature, the heat flow which crosses the walls and the heat transfer coefficient between the wall and fluid shows good agreement and the model is satisfactory since the variations never exceed 14%.