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In the steam cracking industry of natural gas or naphtha, fouling of tubular heat exchangers by cokes is a major issue. This growing carboneous layer has two major negative effects: 1) it increases pressure drop and 2) reduces heat transfer from the tube wall to the processed fluid. Using the open-source Computational Fluid Dynamics software OpenFOAM, this study numerically investigates wall shear stress, pressure drop and heat transfer performances of swirl decaying flow generated by different elliptical cross-section twisted tube. One of the objectives is to determine if minor modifications of tube geometry can generate swirling flow which could enhance wall shear stress at a reduce pressure drop penalty. For a Reynolds number ranging from 10, 000 to 100, 000, it is shown that the investigated geometries could enhance heat transfer by 90% at an increased pressure drop of 128% which yields a Performance Evaluation Criterion (PEC) of 1.44. The comparison between the performances of the different geometries is carried out using a newly defined PEC based on the bulk temperature, along with the usual PEC. [ABSTRACT FROM AUTHOR]

Numerical simulations were carried out to investigate the swirling decaying flow generated by a novel axial guide vane swirler with profiled blades and no supporting device in a tube and its effect on heat transfer and pressure drop compared to a developed turbulent flow in a no swirl tube. Reynolds number ranged from 10,000 to 200,000. Turbulence was modeled using a k − ω Shear Stress Transport model and a Low-Reynolds approach. The swirling flow enhances significantly the heat transfer locally especially in the developing swirling flow region and globally with an increase of Nusselt number from 1.57 to 1.34 respectively for Reynolds number of 10,000 and 200,000. Pressure drop is also increased up to 2.9 for a Reynolds number of 200,000, however this is relatively low compared to other axial guide vane swirler device encountered in the literature. Furthermore, the Performance Evaluation Criterion of the swirling flow is higher than 1 for both Reynolds number of 10,000 and 30,000. [ABSTRACT FROM AUTHOR]