Steam cracking of hydrocarbons is and will be the main process to produce light olefins but emits large quantities of CO2. Enhancing heat transfer in the radiation section, using green energy and novel furnace designs will be key to substantially reducing CO2 emissions.

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The enhancement of convective heat transfer in single-phase heat transfer through the use of helicoidally corrugated tubes has been studied numerically. By comparing the large eddy simulation (LES) results with detailed Stereo-PIV and Liquid Crystal Thermography measurements obtained at the von Karman Institute for Fluid Dynamics (VKI), a validated numerical framework was obtained. Heat transfer enhancements of 83-119% were seen, at the cost of pressure losses that were approximately 5.6 to 6.7 times higher than for a bare tube. To extrapolate the results to industrial Reynolds numbers at which experimental data is scarce, the simulation data was used to develop an improved near-wall Reynolds stress transport model (RSTM) that more accurately describes the heat flux vector. Comparison of both global and local flow characteristics at different Reynolds numbers confirms that the approach allows more accurate predictions over a wider range of design and operating parameters than using two-equation turbulence models, while the computational cost is still significantly lower than LES.

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Spherical dimples in cylindrical tubes enhance heat transfer and lead to a more uniform radial temperature profile. To combine these positive properties with a low pressure drop, a single dimple was optimized through a genetic algorithm. Multiple design parameters such as width, height, and curvature of the dimple were investigated. Heart‐shaped dimples outperformed spherical dimples. Three‐dimensional reactive simulations of a Millisecond propane steam cracking reactor showed that both the spherically dimpled and the heart‐shaped dimpled coil positively affect the light olefin selectivity, mainly through an increase in propylene selectivity. The optimized dimples could reduce the high pressure drop penalty by 21%. Run length simulations proved that the optimized dimple shape results in an additional run length extension of 18%. Next to this, the fuel rate consumption can be decreased by 6% compared to a bare coil, which could theoretically result in 4% less CO2 emissions.

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