Effects of Droplets' Collision on Heat and Mass Transfer between High-Temperature Gas and Micron Water Droplets

Abstract:

The heat and mass transfer process between gas and micron water droplets is complicated. During the process, the collision of droplets can affect the evaporation rate of droplets, and the heat and mass transfer between two phases as well. Unsteady numerical simulation was done in this paper to investigate the effect of droplets collision on the heat and mass transfer. The results show that after the water droplets collide and combine together, the total heat transfer area decreases, thus the accelerated rate of droplet temperature drops. As a result, the unsteady time of droplet temperature rising with considering droplets collision in calculation is longer than that of without considering droplets collision. After droplets collide and combine together, the evaporation rate drops, thus the droplets survival time and time for evaporating completely are extended. The steady gas temperature with droplets collision is higher slightly than that without droplets collision, which indicates that the droplets collision affect the results by using numerical prediction. Against the experimental data, the predicted results with droplets collision are more believable than that without collision. Considering the droplets collision and combination, the change rate of the droplets diameter drops, thus the gas velocity picks up slowly.

• Periodical: Key Engineering Materials (Volumes 609-610)
• Pages: 1386-1391
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.609-610.1386
• Online since: April 2014
• Authors: Guo He, Xiao Chuan Wang*, Yan Fei Li
• Keywords: Eulerian-Lagrangian Method, Exhaust System, Gas-Droplets Two-Phase Flow, Spray Cooling

References

[1] He Guo，Wang Xiaochuan．Research on spray cooling within finite volume based on Eulerian-Lagrangian method [C] / Proceedings of International Conference on Smart Technologies for Materials and Communications，Melbourne，Australia，March 15-16，2012：131-135.

DOI: 10.4028/www.scientific.net/aef.4.131

[2] Sun Huijuan, Zhang Haibin, Bai Bofeng. Evaporation investigation of single droplet in high temperature fuel gas [J]. Journal of Xi'an JiaoTong University, 2008, 42(7): 833-837.

[3] Yuan Jiangtao, Jin Renxi and Yang Li. Coupling characteristics of droplet's motion and evaporation in high-temperature gas stream and their influencing factors [J]. Journal of HuaZhong University of Science and Technology (Natural Science Edition), 2009, 37(12): 92-95.

[4] Wang Xiaochuan, He Guo. Study of cooling engine exhaust systems with water spray by using ELM [J]. Journal of HuaZhong University of Science and Technology (Natural Science Edition), 2013, 41(1): 31-35.

[5] Xia J L, Jarvi J, Nurminen E, et al. Effect of nozzle location and nozzle capacity on spray cooling of hot gas in a horizontal duct [J]. Canadian Metallurgical Quarterly, 2007, 46(4): 407-414.

DOI: 10.1179/cmq.2007.46.4.407

[6] Poole D R, Barenghi C F, Sergeev Y A, et al. Motion of tracer particles in He II [J]. Physical Review B, 2005，71(6)：064514-1-16.

[7] Sazhin S S, Abdelghaffar W A, Sazhina E M, et al. Model for droplet transient heating: Effects on droplet evaporation, ignition and break-up [J]. International Journal of Thermal Sciences, 2005, 44(7): 610-622.

DOI: 10.1016/j.ijthermalsci.2005.02.004

[8] Liu Q, Cai T M, He G Q, et al. Droplet collision and coalescence model [J]. Applied Mathematics and Mechanics, 2006, 27(1): 67-73.

[9] Hou Lingyun. Manual of Spraying Technology [M]. Beijing, China: Sinopec Press, (2006).

[10] Fluent Inc. Fluent 6. 3 user's guide [Z]. Lebanon，USA：Fluent Inc，(2006).

[11] Rahimi A, Taheri M and Fathikalajahi J. Mathematical modeling of heat and mass transfer in hot gas spray systems [J]. Chemical. Engineering Communications, 2002, 189 (7), 959-973.

DOI: 10.1080/00986440213133