Novel cracking coil design based on positive constructing of synergetic flowing field

摘要

A novel insert-hollow cross disk (HCD) combined with twisted tape is embedded in a cracking coil to enhance the propane cracking process by positive constructing of synergetic flowing field. Quantitative analysis of appropriate insert arrangement has been conducted based on contrastive CFD simulation results in the bare and novel coil. The characteristic exchanging flow between the central zone and the near wall area induced by inserts in the novel coil can play an effective role in improving the radial synergy among heat, mass and velocity. This leads to an obvious yield increase of 0.50% and 10.23% of ethylene and propylene comparing with the bare coil. And the average tube skin temperature is declined by 28.45 k. Moreover, the Nu and Sh are increased by 10.96% and 2.98% respectively and the overall PEC factor has a rise of 8.00% in the novel coil. This confirms the effective strengthening effect by the novel coil.Furthermore, the field synergy theory is applied to evaluate the synergy improvement for the heat and mass transfer process. Comparing with the bare coil, the synergy angles for heat as well as mass transfer in the novel coil have a maximum decrease of 21.76% and 23.14% in the downstream of the twisted tape (z/L = 0.23) and HCD insert (z/L = 0.60), respectively. This could explain the enhanced heat and mass transfer as well as the product distribution due to the synergic flow field in the novel coil with the assemble inserts group. (C) 2018 Elsevier Ltd. All rights reserved.