Experimental study on bubble size distribution of subcooled flow boiling in cylinder head of internal combustion engines

2019 ◽  
Vol 33 (2) ◽  
pp. 913-921
Author(s):  
Jie Ni ◽  
Taotao Cao ◽  
Liuwendi Hou ◽  
Fei Dong
Keyword(s):  
Experimental Study ◽  
Size Distribution ◽  
Bubble Size ◽  
Cylinder Head ◽  
Internal Combustion Engines ◽  
Flow Boiling ◽  
Bubble Size Distribution ◽  
Combustion Engines ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow

Experiments on Lift-off Bubble Size Distribution in Subcooled Flow Boiling

2019 ◽  
Vol 2019.24 (0) ◽  
pp. A215
Author(s):  
Tomio OKAWA ◽  
Kazuhiro KAIHO ◽  
Hongji LI ◽  
Koki OHORI ◽  
Shintaro SAKAMOTO ◽  
...  
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Flow Boiling ◽  
Bubble Size Distribution ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Lift Off

Numerical Simulation of Subcooled Flow Boiling Using a Bubble Tracking Method

2016 ◽  
Author(s):  
Tomio Okawa ◽  
Naoki Miyano ◽  
Kazuhiro Kaiho ◽  
Koji Enoki
Keyword(s):  
Numerical Simulation ◽  
Size Distribution ◽  
Void Fraction ◽  
Bubble Size ◽  
Flow Boiling ◽  
Bubble Nucleation ◽  
Bubble Size Distribution ◽  
Subcooled Flow Boiling ◽  
Tracking Method ◽  
Subcooled Flow

The process of bubble nucleation in subcooled flow boiling was visualized using a high speed camera to show that the bubble size can be significantly different between the nucleation sites. However, the bubble size is usually assumed constant in the numerical simulation of subcooled flow boiling. To explore the effect of the bubble size distribution on the void fraction in subcooled flow boiling, numerical simulations were performed using a bubble tracking method in which the size and position of each bubble are calculated individually using a Lagrangian coordinates. In the present simulation, the void fraction was greater when the bubble size distribution was taken into consideration. Since the bubble tracking method requires many correlations, further improvement is necessary. The present numerical results however indicate that the bubble size distribution should be taken in to consideration to evaluate the void fraction in subcooled flow boiling accurately.

Accurate Estimation of Vaporization Rate in Subcooled Flow Boiling Based on the Results of Visualization Experiment

2016 ◽  
Author(s):  
Kazuhiro Kaiho ◽  
Koji Enoki ◽  
Tomio Okawa
Keyword(s):  
Size Distribution ◽  
Gaussian Distribution ◽  
Bubble Size ◽  
Flow Boiling ◽  
Heated Surface ◽  
Bubble Size Distribution ◽  
Vaporization Rate ◽  
Subcooled Flow Boiling ◽  
Bubble Detachment ◽  
Subcooled Flow

This research presents experimental approaches to accumulate the data for mechanistic model in subcooled flow boiling. A number of photographic studies have been provided to investigate phenomena of bubble nucleation and condensation process for accurate prediction of void fraction such as bubble detachment diameter, bubble detachment frequency and nucleation site density in a subcooled flow boiling. In this work, a transparent heated surface was used to obtain the data from back side of heated surface to avoid overlapping bubbles by using high speed video camera. It enabled to observe bubble nucleation process and active nucleation sites. The experiment was performed in a vertical rectangular channel at atmospheric pressure and the water was used as test fluid. In generally, the computational analysis for a subcooled flow boing deal with mean bubble size as the size of bubbles produced on heated surface. Although, it was found that mean bubble size can represent bubbles produced at same site because they are almost uniform size. Even though the size of bubbles at same site are almost uniform, the difference of the size of bubbles between other sites are considerable value. Therefore, mean bubble size on the surface should not represent bubbles for all site otherwise the serious error may be caused. It seems that bubble detachment diameter should not be given by correlations of mean bubble detachment diameter for accurate prediction of vaporization rate. Some researchers proposed that bubble size distribution should be considered by Gaussian distribution [1–3]. However, it found that bubble size distribution data accumulated in this work cannot be fitted by Gaussian distribution and there are probability that larger bubbles are neglected due to the configuration features of Gaussian distribution. So, Gamma distribution was used to predict the bubble size distribution and it was evaluated in terms of heat flux, wall superheat, mass flux and liquid subcooling. And then, by the experimental approaches, the important dimensionless parameters are identified such as Nusselt number, Jakob number, Reynolds number and dimensionless subcooling. Furthermore, vaporization rate was calculated by correlations of bubble detachment diameter, bubble detachment diameter and nucleation site density and compared with the data. Finally, the effect of using mean bubble size or bubble size distribution on vaporization rate was investigated.

A theoretical and experimental study on subcooled flow boiling at high heat flux

1994 ◽  
Vol 29 (5) ◽  
pp. 319-327 ◽  
Author(s):  
K. W. Lin ◽  
C. H. Lee ◽  
L. W. Hourng ◽  
J. C. Hsu
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow
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