An Experimental Study on the Heat Transfer of Traveling Airborne Water Droplets in Cold Environment

2015 ◽  
Vol 32 (2) ◽  
pp. 219-225 ◽  
Author(s):  
Y.-K. Chuah ◽  
J.-T. Lin ◽  
K.-H. Yu

AbstractThis paper presents experimental results on rapid freezing of water droplets injected into a low temperature environment. A heat balance method was applied to determine the ratio of the water droplets frozen at the collection after the airborne time. The experimental results show that rapid freezing of water droplets could be achieved within three seconds of airborne time. Droplet size distribution of the frozen water droplets after collection was estimated. Heat transfer during the airborne time was calculated with consideration of the droplet size distribution. At attempt was taken to compare the heat transfer obtained with some previous studies on heat transfer of spherical objects in air. The research results show that droplet size distribution is important for the prediction of heat transfer of water droplets traveling in air. The results presented in this study contribute to the understanding of heat transfer of water droplets injected into a low temperature air.

Author(s):  
Qun Zhang ◽  
Xin Wang ◽  
Rui Kou ◽  
Chaochao Li ◽  
Peng Zhang ◽  
...  

The overall process and mechanism of the centrifugal pre-film atomization with double swirling flow were studied using the methods of large Eddy simulation and volume of fluid. The atomization process includes a centrifugal jet under the primary swirl and a pre-film atomization under the two-stage counter-rotating swirl at the venturi outlet. The fuel is ejected from the outlet of the centrifugal nozzle and undergoes the transient process of reaching the venturi throat. The breaking mechanism of liquid film in this process is the same as that of the formation mechanism of the mushroom-shaped tip of liquid jet. The numerical simulation results are highly consistent with the experimental results. For the formation and development of the liquid film on the venturi wall, collision and wave action promote the expansion of the liquid film. At the outlet position of the venturi tube, the short wave mode and the two-stage reverse swirling structure play major roles in the fragmentation process of the flake liquid film, which coincides with the flow characteristics given by the experiment. It is found that the spray cone angle increases as the fuel flow rate increases, and the numerical results are basically consistent with the predicted values of the empirical formula under different fuel flow rates. The droplet size distribution showed a Poisson distribution during the atomization of centrifugal jets and pre-film, and the peak position and variation trend of the droplet size distribution at the outlet of the venturi tube were basically consistent with experimental results.


1977 ◽  
Vol 99 (3) ◽  
pp. 381-385 ◽  
Author(s):  
K. H. Chen ◽  
G. J. Trezek

Energy balance considerations indicate that the droplet heat transfer coefficient, local wet bulb temperature, and droplet size distribution function are the basic parameters affecting spray system thermal performance. Within the range of available experimental data, results indicate that the Ranz-Marshall correlation gives an agreement to within ±5.0 percent of measured droplet temperatures at the pond surface for a medium wind range of between 2.5 and 5 m/s. The local wet bulb temperature is taken as the arithmetic mean of the initial and final wet bulb temperatures. For wind speeds greater than 3.5 m/s, the local wet bulb can be taken as the ambient. The modified log normal distribution of Mugele and Evans provides the best description of the droplet size distribution. Further, through the introduction of a correction term, the Spray Energy Release (SER) can be deduced from single droplet information.


2006 ◽  
Vol 16 (6) ◽  
pp. 673-686 ◽  
Author(s):  
Laszlo E. Kollar ◽  
Masoud Farzaneh ◽  
Anatolij R. Karev

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