Liquid film distribution around long gas bubbles propagating in rectangular capillaries

2022 ◽  
pp. 103939
Author(s):  
M. Magnini ◽  
F. Municchi ◽  
I. El Mellas ◽  
M. Icardi
Keyword(s):  
Liquid Film ◽  
Gas Bubbles ◽  
Film Distribution

NUMERICAL INVESTIGATION OF FILM DISTRIBUTION IN HORIZONTAL-TUBE FALLING FILM EVAPORATOR

2011 ◽  
Vol 19 (03) ◽  
pp. 177-183 ◽  
Author(s):  
JIN-BO CHEN ◽  
QING-GANG QIU
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Film Thickness ◽  
Liquid Film ◽  
Numerical Investigation ◽  
Horizontal Tube ◽  
Flow Density ◽  
Falling Film ◽  
Film Distribution ◽  
Simulation Results

The technique of horizontal-tube falling film has been used in the cooling and heating industries such as refrigeration systems, heating systems and ocean thermal energy conversion systems. The comprehensive performance of evaporator is directly affected by the film distribution characteristics outside tubes. In this paper, numerical investigation was performed to predict the film characteristics outside the tubes in horizontal-tube falling film evaporator. The effects of liquid flow rate, tube diameter and the circular degree of tube on the film thickness were presented. The numerical simulation results were compared with that of the empirical equations for calculating the falling film thickness, and agreements between them were reasonable. Numerical simulation results show that, at the fixed fluid flow density, the liquid film is thicker on the upper and lower tube and the thinnest liquid film appears at angle of about 120°. The results also indicate that, when the fluid flow density decreases to a certain value, the local dryout spot on the surface of the tube would occur. In addition, the film thickness decreases with the increases of the tube diameter at the fixed fluid flow density.

Analysis for the Fluctuation Characteristics of Annular Flow in the Oil-Air Lubrication System

2014 ◽  
Vol 487 ◽  
pp. 408-412
Author(s):  
Qi Guo Sun ◽  
Ali Cai ◽  
Zheng Hui Zhou ◽  
Zhi Hong Li ◽  
Xiong Shi Wang
Keyword(s):  
Pressure Drop ◽  
Film Thickness ◽  
Liquid Film ◽  
Annular Flow ◽  
Lubrication System ◽  
Air Velocity ◽  
Film Distribution ◽  
Air Lubrication ◽  
Calculation Results ◽  
Simulation Results

Fluctuation characteristics of the pressure drop distribution and liquid film distribution along a pipe of the oil-air annular flow in oil-air lubrication system are calculated respectively introducing Chisholm constant c base on the Chisholm theory and simulated by Fluent in this paper. The results show that the theoretical calculation results of the pressure drop and liquid film agree qualitatively with the simulation results, and the fluctuation characteristics of the pressure drop and liquid film thickness are augmented respectively when the air velocity increases. These conclusions will do favors for predicting and controlling the lubricant in the oil-air lubrication system.

Boundary-Layer Cooling by Spattered Particles

1967 ◽  
Vol 89 (1) ◽  
pp. 7-10 ◽  
Author(s):  
B. Steverding
Keyword(s):  
Boundary Layer ◽  
Surface Tension ◽  
Liquid Film ◽  
Flow Condition ◽  
Material Parameter ◽  
Gas Bubbles ◽  
Liquid Films ◽  
General Belief ◽  
Effective Boundary

The phenomenon of spattering of ablating liquid films is studied under the condition that gas bubbles penetrate the liquid film. The characteristic material parameter for spattering is the surface tension. Contrary to general belief, it will be shown that spattering will not always decrease ablation effectiveness and that, under certain “ideal” conditions, effective boundary-layer cooling by spattered particles may be achieved. Ideal spattering can only occur when the surface tension has a distinct value for a given flow condition. The phenomenon of preferential ablation may be explained by this phenomenon.

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