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42759-AC9
Entrainment and Evaporation of a Nozzle Spray in Gas-Solids Fluidization System
Evaporating nozzle sprays in gas-solids fluidization systems are widely used in many petroleum industrial processes. The following three studies are supported by this PRF grant: (1) effect of spray evaporation on gas entrainment in a co-current spray jet [1]; (2) effect of aspect ratio of rectangular nozzles on evaporating spray penetration and mixing in gas-solid fluidized bed [2]; (3) Modeling and experimental investigation on mass and heat transfers of droplet-solid collision [3].
An experimental system has been set up to directly measure the air entrainment induced by a liquid nitrogen spray jet into an unbounded and stagnant air. An in-situ oxygen concentration analyzer, a thermocouple system and a LDV velocimetry are implemented to determine the flow structure of the spray jet. The results indicate that there exist flow similarities in evaporating spray jets with round nozzles and suggest that the evaporation of spray markedly weakens the gas entrainment.
A numerical study has been performed on the effects of aspect ratio of rectangular nozzles on the spray characteristics and phase interactions in spray-gas-solid three-phase flows. Our study shows that the effect of aspect ratio has a significant impact on the penetration length and trajectories of the spray jet under the same flow conditions.
As the hydrodynamics of droplet-solid collision has significant effect on the entrainment and evaporation characteristics of nozzle spray, a detailed modeling and experimental study is conducted on the mechanism of the mass and heat transfer of droplet-solid collision under different working conditions. The droplet attachment, mass and heat transfer during the collision under different temperature condition, the bridge effect when droplet collides with a group of two or three solids are investigated in detail. Parametric studies on many parameters such as droplet velocity, size ratio between the droplet and solid, temperature difference between droplet and solid, are studies. The study gives a basic understanding on the mechanism of hydrodynamics of multiphase flow.
[1] M.M. Rafique Qureshi and C. Zhu, “Gas entrainment in an evaporating spray jet”, Int. J. Heat & Mass Transfer, 49, 3417-3428, 2006.
[2] M. M. Rafique Qureshi and C. Zhu, “Crossflow evaporating sprays in gas-solid flows: Effect of aspect ratio of rectangular nozzles”, Powder Technology, 166, 60-71, 2006.
[3] Zheng Shen, Phase Transfer in Droplets-Solids Collisions, Master Thesis, New Jersey Institute of Technology, Newark, NJ, 2007.
