Effect of Hydraulic Jump on Hydrodynamics and Heat Transfer in a Thin Liquid Film Flowing Over a Rotating Disk Analyzed by Integral Method

2006 ◽  
Vol 129 (5) ◽  
pp. 657-663 ◽  
Author(s):  
S. Basu ◽  
B. M. Cetegen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Film ◽  
Hydraulic Jump ◽  
Thin Liquid Film ◽  
Rotating Disk ◽  
Disk Surface ◽  
Constant Heat Flux ◽  
Heat Transfer Analysis ◽  
Scaling Analysis

Flow and heat transfer in a liquid film flowing over the surface of a rotating disk was analyzed by integral technique. The integral analysis includes the prediction of the hydraulic jump and its effects on heat transfer. The results of this analysis are compared to the earlier results that did not include this effect. At low inlet Reynolds numbers and high Rossby numbers, corresponding to low film inertia and low rotation rates, respectively, a hydraulic jump appears on the disk surface. The location of the jump and the liquid film height at this location are predicted. A scaling analysis of the equations governing the film thickness provided a semi-empirical expression for these quantities that was found to be in very good agreement with numerical results. Heat transfer analysis shows that the Nusselt numbers for both constant disk surface temperature and constant disk surface heat flux boundary conditions are lowered in the vicinity of the hydraulic jump due to the thickened liquid film. This effect can be more pronounced for the constant heat flux case depending on the location of the hydraulic jump. The Nusselt number exhibits a turning point at the jump location and can have higher values downstream of the hydraulic jump compared to those obtained from the analysis that does not include the gravitational effects.

scholarly journals Analysis of Hydrodynamics and Heat Transfer in a Thin Liquid Film Flowing Over a Rotating Disk by the Integral Method

2005 ◽  
Vol 128 (3) ◽  
pp. 217-225 ◽  
Author(s):  
S. Basu ◽  
B. M. Cetegen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Rotating Disk ◽  
Disk Surface ◽  
Experimental Results ◽  
Rotation Rates

An integral analysis of hydrodynamics and heat transfer in a thin liquid film flowing over a rotating disk surface is presented for both constant temperature and constant heat flux boundary conditions. The model is found to capture the correct trends of the liquid film thickness variation over the disk surface and compare reasonably well with experimental results over the range of Reynolds and Rossby numbers covering both inertia and rotation dominated regimes. Nusselt number variation over the disk surface shows two types of behavior. At low rotation rates, the Nusselt number exhibits a radial decay with Nusselt number magnitudes increasing with higher inlet Reynolds number for both constant wall temperature and heat flux cases. At high rotation rates, the Nusselt number profiles exhibit a peak whose location advances radially outward with increasing film Reynolds number or inertia. The results also compare favorably with the full numerical simulation results from an earlier study as well as with the reported experimental results.

Numerical Investigation of EHD Conduction Pumping of Liquid Film With Phase-Change

2007 ◽  
Author(s):  
Miad Yazdani ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Phase Change ◽  
Flow System ◽  
Thin Liquid Film ◽  
Finite Thickness ◽  
Constant Heat Flux ◽  
Two Dimensional ◽  
Enhanced Heat Transfer ◽  
Constant Heat

Electrohydrodynamic (EHD) conduction pumping is associated with the heterocharge layers of finite thickness in the vicinity of the electrodes, generated by the process of dissociation of the neutral electrolytic species and recombination of the generated ions. This paper numerically investigates the EHD conduction pumping of a thin liquid film in the presence of phase change. The flow system comprises a liquid film flowing over a two-dimensional flat plate while the vapor phase extended far beyond the interface to result in almost motionless vapor. The channel is separated into four different sections: the entrance, electrode, evaporation, and downstream sections. The entrance, electrode and downstream regions are adiabatic while a constant heat flux is applied in the evaporation side. The concept of EHD conduction pumping of liquid film in the presence of phase change is demonstrated in this paper. The enhanced heat transfer due to conduction pumping is evaluated.

scholarly journals Convection Heat Transfer Analysis in A Vertical Porous Tube

2020 ◽  
Vol 8 (1) ◽  
pp. 31-45
Author(s):  
Hikmat N. Abdulkareem ◽  
Kifah H. Hilal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convection Heat Transfer ◽  
Particle Diameter ◽  
Vertical Channel ◽  
Packed Bed ◽  
Constant Heat Flux ◽  
Heat Transfer Analysis ◽  
Constant Heat ◽  
Flux Boundary Condition

Forced convective heat transfer in a vertical channel symmetrically heated with a constant heat flux, and packed with saturated porous media, has been investigated experimentally in the present work. The channel was padded with spherical glass of three diameter (1, 3 and 10 mm) in a range 0.0416 < (particle diameter / inner channel radius) <0.416. The experimental setup, using a copper tube as a packed bed assembly with (48 mm) inside diameter and (1150 mm) heated length with a constant heat flux boundary condition. The test section was vertically oriented with water flowing against gravity and packed with glass spheres (1, 3 and 10 mm) diameter respectively. The results show that local Nusselt number increased at 34% with increasing Reynolds number at 65% while increased at 11% with increasing heat flux at 71%. Heat transfer rate increase as the particle diameter increase at the range of (1 – 3) mm but decrease with increasing particle diameter at the range (3 – 10) mm. Pressure drop through channel minimize at 97% as porosity increase at 23%.Many empirical relations, obtained experimentally.

Temporal Effect and Transient Simulation of Thin Liquid Film in Micro Channels

2013 ◽  
Author(s):  
Yu-Yan Jiang ◽  
Da-Wei Tang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Film ◽  
Flow Boiling ◽  
Thin Liquid Film ◽  
Liquid Films ◽  
Transient Simulation ◽  
Governing Equations ◽  
Flash Evaporation ◽  
Micro Channels

The evaporation and heat transfer of thin liquid film are crucial factors affecting on the heat transfer performance of boiling bubbles or slugs. For boiling in micro-channels, the flash evaporation of the liquid film may give rise to boiling instability, and the dry-out of the film leads to serious deterioration of the heat transport. The thin liquid film has multi-scale transitions, and hence the phase change and fluid dynamics need to be solved by special governing equations and numerical algorithm. The numerical studies to date have solved the steady state distribution of the film, but the difficulty consists in the transient simulation of time-variant liquid films. In the present study, unsteady form governing equations are developed. With inclusion of the temporal terms, we conducted transient simulations for flat liquid films formed during the flow boiling in micro-channels. The model predicts the developing of drying spot during growth of elongated bubbles. The results show that the film thickness and distribution change quickly in a growth period, which are functions of the heat flux, mass flow rate and the other parameters. The quantitative assessment of these effects helps to clarify the mechanism of boiling instability and the conditions for the occurrence of critical heat flux (CHF). The simulation needs special numerical scheme for time marching and stabilization treatment for the nonlinear terms, where the numerical accuracy and the significance of the temporal effects are also discussed.

One-Dimensional Analysis of the Hydrodynamic and Thermal Characteristics of Thin Film Flows Including the Hydraulic Jump and Rotation

1990 ◽  
Vol 112 (3) ◽  
pp. 728-735 ◽  
Author(s):  
S. Thomas ◽  
W. Hankey ◽  
A. Faghri ◽  
T. Swanson
Keyword(s):  
Liquid Film ◽  
Solid Body ◽  
Hydraulic Jump ◽  
Radial Flow ◽  
Thin Liquid Film ◽  
Thermal Characteristics ◽  
Rotating Disk ◽  
Body Rotation ◽  
Solid Body Rotation ◽  
Film Flows

The flow of a thin liquid film with a free surface along a horizontal plate that emanates from a pressurized vessel is examined numerically. In one g, a hydraulic jump was predicted in both plane and radial flow, which could be forced away from the inlet by increasing the inlet Froude number or Reynolds number. In zero g, the hydraulic jump was not predicted. The effect of solid-body rotation for radial flow in one g was to “wash out” the hydraulic jump and to decrease the film height on the disk. The liquid film heights under one g and zero g were equal under solid-body rotation because the effect of centrifugal force was much greater than that of the gravitational force. The heat transfer to a film on a rotating disk was predicted to be greater than that of a stationary disk because the liquid film is extremely thin and is moving with a very high velocity.

Numerical Investigation On Bubble Growth and Merger in Microchannel Flow Boiling with Self-rewetting Fluid

2021 ◽  
Author(s):  
Wei Li ◽  
Yuhao Lin ◽  
Yang Luo
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Film ◽  
Numerical Investigation ◽  
Contact Line ◽  
Bubble Growth ◽  
Flow Boiling ◽  
Thin Liquid Film ◽  
Microchannel Flow ◽  
Thermocapillary Force

Abstract The application of two-phase flow in microchannel needs further research to achieve a more stable and highly-performed heat sink. Utilizing self-rewetting fluid is one of the promising ways to minimize the dryout area, thus increasing the heat transfer coefficient and critical heat flux (CHF). To investigate the heat transfer performance of self-rewetting fluid in microchannel flow boiling, a numerical investigation is carried out in this study utilizing the VOF method, phase-change model and continuum surface force (CSF) model with surface tension versus temperature. Athree-dimensional numerical investigation of bubble growth and merger is carried out with water and 0.2%wt heptanol solution. The single bubble growing cases, two x-direction/y-direction bubbles merging cases and three bubbles merging cases are conducted. Since the bubbles never detach the heated walls, the dryout area and regions nearby the contact line with thin liquid film dominated the heat transfer process during the bubbles' growth and merger. The self-rewetting fluid is able to minimize the local dryout area and achieve the larger thin liquid film area around the contact line due to the Marangoni effect and thermocapillary force, thus result in higher wall heat flux when compared to water. The two x-direction bubbles merging case performed best for heat transfer in the microchannel, in which self-rewetting fluid achieves heat transfer enhancement for over 50 percent compared with water.

Integral Analysis of Heat Transfer on Falling Laminar Liquid Film with Constant Heat Flux

2012 ◽  
Vol 516-517 ◽  
pp. 30-35
Author(s):  
You Shun Peng ◽  
Li Yang ◽  
Yong Cheng Du
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Liquid Film ◽  
Film Flow ◽  
Constant Heat Flux ◽  
Heated Plate ◽  
Flux Boundary Condition ◽  
Integral Analysis ◽  
Characteristic Relationship

Integral analysis of heat transfer of a laminar falling liquid film along a vertical heated plate with specified heat flux boundary condition was investigated. The temperature distribution of liquid film was obtained by utilizing an integral analysis method, which was compared with numerical solution and other researcher’s results. In this analysis a new concept of thermal changing point was put forward. It’s found that the Nusselt number has a characteristic relationship with thermal changing point, which is obtained by calculation. When the film flow distance is less than thermal changing point, the Nusselt number decreases rapidly. When the film flow distance is greater than or equal to thermal changing point, the Nusselt number reaches to a fixed value. A larger Peclet number or lower initial temperature generally leads to a larger Nusselt number in entrance region, whereas the wall heat flux is found to have no influence on the Nusselt number.

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