Experimental study of water droplets impinging upon a hot surface

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Title: Experimental study of water droplets impinging upon a hot surface
Author: Tran, Cong
Abstract: The objective of the presence investigation is to study the droplet impingement characteristics on heated and unheated surfaces with different surface roughness. The purpose is to show clear photographs of the impinging droplets from beneath the solid surface. Atmospheric pressure (lOlkpa), surface materials (glass and copper), impinging droplet temperature (T, = 24C), original droplet diameter (4.7mm), and testing liquid (H20) were fixed. A MotionScope PCI8000S high-speed camera was placed beneath the heated glass surface. Droplets of water were dropped on the test surface, which is located 25 mm to 50 mm under the tip of a burette. For the unheated surfaces, the droplet was positioned above the surface between 23mm and 229mm. Thus, the primary parameter was the Weber number, which ranged from 30 to 60 for heated surface and 29 to 290 for unheated surfaces. Furthermore, the effects of unheated copper surfaces with different surface roughness and droplet characteristic were experimentally studied. Surface temperature was fixed at Tw = 24C whereas Weber number varied from 53 to 266. Impinging of water droplets upon unheated glass surface was also tested at fixed surface temperature of Tw = 24C. However, Weber number was varied from 29 to 290 for unheated glass surface. Finally, a theoretical study was conducted to compare the experimental results with the theoretical results. As a result, surface temperature was found to have very little effect on the spreading process of the impinging droplet upon both heated and unheated glass surface. Moreover, the results from impinging droplets upon unheated copper and glass surface were also analyzed. It was found that surface roughness exhibited no significant effect on the spreading process. The measurement values of maximum spreading diameter collected in the present investigation compare well with the predictions model provided by previous investigators. However, the maximum spreading time of the impinging droplets upon both heated and unheated surface did not correlate well with the previous models.
Record URI: http://hdl.handle.net/1850/14253
Date: 2000-08

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