(304g) 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.