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Abstract
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Gas-liquid two-phase flow in crude oil transmission pipelines represents one of the major challenges in the oil and gas industry both in Iran and globally. Given that a significant portion of Iran's produced crude oil contains associated petroleum gas, nearly all major transmission pipelines in the country operate under two-phase flow conditions. The presence of gas in the crude oil stream reduces the convective heat transfer rate from the pipe wall to the fluid, particularly in tropical regions with high ambient temperatures, leading to elevated wall temperatures and accelerated paraffin and asphaltene deposition. These deposits reduce the effective pipe diameter, increase pressure drop, and impose substantial annual cleaning and maintenance costs on the oil industry [3]. Furthermore, non-uniform bubble distribution and unstable flow regimes such as slug flow cause severe pipe vibration, localized corrosion, and even the risk of pipe rupture, thereby threatening personnel and equipment safety. Any oil leakage resulting from these issues creates irreversible environmental damage, while increased energy consumption to compensate for excess pressure drop further elevates greenhouse gas emissions.
From an economic and scientific perspective, the reduced transmission capacity caused by these phenomena lowers pipeline efficiency and necessitates additional investments in higher-power pumping or parallel lines. Most existing global models have been developed based on low-viscosity fluids and lack sufficient accuracy for heavy Iranian crude oil [4]. Therefore, accurate numerical modeling that simultaneously investigates heat transfer rate and bubble distribution under real Iranian conditions not only contributes to design optimization, operational cost reduction, and enhanced safety, but also facilitates the localization of technical knowledge, laying the foundation for future research on more complex multiphase flows and taking a significant step toward greater sustainabi
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