265045 Numerical Investigation of Effect of Hollow Cross-Over Disk On Flow and Heat Transfer in Tube of Cracking Furnace
This paper presents the influence of main parameters of a novel hollow cross-over disk (HCD) on flow, heat transfer enhancement and flow resistance in tube of ethylene cracking furnace. The location of HCD in the tube, geometric size and shape of HCD are studied. Global analysis of thermal performance and local analysis of vorticity flux, turbulence mixing and friction factor are performed based on computational fluid dynamics (CFD). The numerical results indicated the overall Nusselt number of tube decreased when HCDs' location was far from the inlet and the space between HCD pair decreased. While the total pressure drop of the tube had no significant change with the variance of HCDs' location. The effects of the geometrical size of the HCD on heat transfer enhancement were analyzed from the view point of the field synergy principle and it was found that the increase of heat transfer enhancement was always accompanied with the decrease of field synergy angle between the velocity and temperature gradient when the geometrical parameters of HCD were changed. This confirms that the basic mechanism of heat transfer enhancement by HCD can be well described by the field synergy principle. This present results show that heat transfer enhancement can be achieved without much flow resistance using strategies of geometrical optimization and appropriate placement for HCDs, which is benefit to energy consumption decreasing and coke formation inhabitation for tubular cracking furnace.