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In this paper, we consider the heat transfer problems associated with a periodic array of triangular, longitudinal, axisymmetric, and pin fins. The problems are modeled as a wall where the flat side is isothermal and the other side, which has extended surfaces/fins, is subjected to convection with a uniform heat transfer coefficient. Hence, our analysis differs from the classical approach because (i) we consider multidimensional heat conduction and (ii) the wall on which the fins are attached is included in the analysis. The latter results in a nonisothermal temperature distribution along the base of the fin. The Biot number (Bi=ht/k) characterizing the heat transfer process is defined with respect to the thickness/diameter of the fins (t). Numerical results demonstrate that the fins would enhance the heat transfer rate only if the Biot number is less than a critical value, which, in general, depends on the geometrical parameters, i.e., the thickness of the wall, the length of the fins, and the period. For pin fins, similar to rectangular fins, the critical Biot number is independent of the geometry and is approximately equal to 3.1. The physical argument is that, under strong convection, a thick fin introduces an additional resistance to heat conduction.

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Hydraulic performance and thermal characterization are the main parameters dictating proper consideration of flow assurance in pipelines. Hydraulic performance considers the evaluation of multiphase systems, specifically the equilibrium of phases and consequent flow patterns and their impact on pressure loss, holdup and sustainable and safe flow transport characteristics. Secure supply of hydrocarbons via pipelines plays crucial importance to maximize their production. In this study, a multiphase flow simulation of gas-condensate is developed using PIPESIM™ software. The data and main physical parameters correspond to a projected off-shore natural gas pipeline located in the north sea of Venezuela. The flow of hydrocarbons is analyzed and potential improvements are presented using both a traditional single-size and an ¨out-of-the-box¨ multi-sizing technique with the objective to reduce predicted overall holdups and pressure drops along the pipeline. The simulation permitted to assess different flow characteristics as liquid holdup, flow rate and pressure drop through different sections and accessories of the pipeline. Fixed pipeline insulation was maintained along all the study to keep a practical number of independent variables. The outcome of the analysis demonstrates that with a reasonable adjustment of pipe diameter, it is possible to increase the gas production without extra energy to compress the line, favoring the project economy and reducing its carbon footprint.