Effect of Nozzle Configuration on Transport in the Stagnation Zone of Axisymmetric, Impinging Free-Surface Liquid Jets: Part 1—Turbulent Flow Structure

1992 ◽  
Vol 114 (4) ◽  
pp. 874-879 ◽  
Author(s):  
J. Stevens ◽  
Y. Pan ◽  
B. W. Webb
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Flow Structure ◽  
Nozzle Exit ◽  
Local Heat Transfer ◽  
Liquid Jet ◽  
Mean Velocity ◽  
Stagnation Region ◽  
Surface Liquid ◽  
Nozzle Type

This study characterized the mean and fluctuating parts of the radial component of the local velocity in the stagnation region of an impinging, free-surface liquid jet striking a smooth flat plate. Four different nozzle exit conditions were studied, including fully developed pipe flow, a contoured nozzle, and turbulence-damped and -undamped sharp-edged orifices. Liquid jet Reynolds numbers in the range 30,000 to 55,000 were investigated. Velocities were measured using laser-Doppler velocimetry. Mean velocities were found to vary nearly linearly with radial location, with the slope of the line being a function of distance from the impingement plate. Dimensionless mean velocity gradients, of relevance to the heat transfer, were found to be a strong function of nozzle type, but roughly independent of jet Reynolds number for a given nozzle type. Turbulence levels were also found to be strongly influenced by the nozzle exit condition. Local heat transfer data corresponding to the flow structure measurements presented here are reported in Part 2 of this study.

Turbulence Dissipation in a Free-Surface Jet of Water and Its Effect on Local Impingement Heat Transfer From a Heated Surface: Part 1—Flow Structure

1995 ◽  
Vol 117 (1) ◽  
pp. 85-94 ◽  
Author(s):  
D. H. Wolf ◽  
R. Viskanta ◽  
F. P. Incropera
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Flow Structure ◽  
Heated Surface ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Mean Velocity ◽  
Planar Jet ◽  
Impingement Heat Transfer ◽  
Surface Jet

This study investigates the relationship between jet turbulence and local impingement heat transfer for a free-surface, planar jet of water. Employing a thermal anemometer system, measurements of the mean velocity and turbulence intensity are reported at different streamwise and spanwise locations throughout the jet. The flow conditions at the nozzle discharge were controlled by using different nozzle designs (parallel-plate and converging) and flow manipulators (wire grid and screens). Measurements of the velocity gradient along the impingement surface, known to influence heat transfer from analytical considerations of a laminar impinging jet, were also made for the same sets of nozzle conditions. The test matrix also included variations in the Reynolds number (23,000 and 46,000) and distance from the nozzle discharge to the surface (0 to 30 nozzle widths). The local heat transfer results corresponding to the flow structure measurements are reported in Part 2 of this paper.

scholarly journals Conjugated Heat Transfer on a Horizontal Surface Impinged by Circular Free-Surface Liquid Jet.

2002 ◽  
Vol 45 (2) ◽  
pp. 307-314 ◽  
Author(s):  
Yaohua ZHAO ◽  
Takashi MASUOKA ◽  
Takaharu TSURUTA ◽  
Chong-Fang MA
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Horizontal Surface ◽  
Liquid Jet ◽  
Conjugated Heat Transfer ◽  
Surface Liquid

Impingement Heat Transfer of Free-Surface Liquid Jets

2002 ◽  
Author(s):  
Albert Y. Tong
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Stagnation Region ◽  
Navier Stokes Equations ◽  
Impingement Heat Transfer

The problem of convective heat transfer of a circular liquid jet impinging onto a substrate is studied numerically. The objective of the study is to understand the hydrodynamics and heat transfer of the impingement process. The Navier-Stokes equations are solved using a finite-volume formulation. The free surface of the jet is tracked by the volume-of-fluid method. The energy equation is modeled by using an enthalpy-based formulation. Detailed flow fields as well as free surface contours and pressure distributions on the substrate have been obtained. Local Nusselt number variations along the solid surface have also been calculated. The effects of several key parameters on the hydrodynamics and heat transfer of an impinging liquid jet have been examined. It has been found that the jet-inlet velocity profile and jet elevation have a significant effect on the hydrodynamics and heat transfer, particularly in the stagnation region, of an impinging jet. The numerical results have been compared with experimental data obtained from the literature. The close agreement supports the validity of the numerical study.

Effect of Nozzle Configuration on Transport in the Stagnation Zone of Axisymmetric, Impinging Free-Surface Liquid Jets: Part 2—Local Heat Transfer

1992 ◽  
Vol 114 (4) ◽  
pp. 880-886 ◽  
Author(s):  
Y. Pan ◽  
J. Stevens ◽  
B. W. Webb
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Free Surface ◽  
Radial Velocity ◽  
Velocity Gradient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Liquid Jets ◽  
Stagnation Zone ◽  
Surface Liquid

This is the second of a two-part study on the flow structure and heat transfer characteristics of turbulent, free-surface liquid jets. Part 2 deals with the effect of selected nozzle configurations on the local heat transfer in the stagnation zone. Infrared techniques have been used to characterize the local heat transfer for the four nozzle configurations whose mean and turbulent flow structure was detailed in Part 1. The results show that for identical jet Reynolds numbers, significant differences exist in the magnitudes of the local Nusselt number for the nozzle types studied. Differences of approximately 40 percent were observed. Local heat transfer results reveal that for already turbulent jets, the mean radial velocity gradient appears to be more influential in determining the heat transfer than incremental changes in the level of turbulence (as measured by the radial component of the fluctuations). An empirical correlation of the experimental data supports this conclusion, and reveals that the stagnation Nusselt number is affected independently by the jet Reynolds number and the dimensionless mean radial velocity gradient.

Heat Transfer Characteristics of Arrays of Free-Surface Liquid Jets

1995 ◽  
Vol 117 (4) ◽  
pp. 878-883 ◽  
Author(s):  
Y. Pan ◽  
B. W. Webb
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Free Surface ◽  
Local Heat Transfer ◽  
Jet Flow ◽  
Local Heat ◽  
Liquid Jets ◽  
Heat Transfer Characteristics ◽  
Array Configuration ◽  
Surface Liquid

In this study, local heat transfer data under arrays of free-surface liquid jets are measured with a two-dimensional infrared radiometer. Experimental measurements were made for three nozzle diameters using a seven-jet staggered and a nine-jet inline geometric array configuration. Nozzle-to-plate spacings of two and five nozzle diameters were investigated for four jet center-to-center spacings ranging from two to eight diameters in the jet Reynolds number range of 5000 to 20,000. Results show that the stagnation Nusselt number under the central jet is independent of array configuration and jet-to-jet spacing. The different inter jet flow interaction, as represented by different jet array configurations (the in-line array and the staggered array with different nozzle-to-nozzle spacings), shows negligible influence on local heat transfer under the central jet. Differences in the heat transfer characteristics for the two nozzle-to-plate spacings investigated were the result of an observed transition from confined submerged central jet flow to free-surface jet flow as the nozzle-to-plate spacing was increased. Secondary maxima in the Nusselt number were observed between the adjacent jets, being a direct consequence of the radial flow interaction between jets. A correlation for average heat transfer is presented.

Numerical Investigation of Heat Transfer Enhancement on a Small Scale Vortex Generator

2009 ◽  
Author(s):  
Jiansheng Wang ◽  
Zhiqin Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Rectangular Channel ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Small Scale ◽  
Transfer Enhancement

The heat transfer characteristic and flow structure of fluid in the rectangular channel with different height vortex generators in small scale are investigated with numerical simulation. Meantime, the properties of heat transfer and flow of fluid in the rectangular channel are compared with the channel which located small scale vortex generator. The variation law of local heat transfer and flow structure in channel is obtained. The mechanism of heat transfer enhancement of small scale vortex generators is discussed in detail. It is found that the influence of vortex generator on heat transfer is not in proportion to the size of vortex generator. What is more, turbulent flow structure near the wall, which influences the temperature distribution near the wall, induces the variety of local heat transfer. The fluid movement towards to the wall causes the heat transfer enhanced. On the contrary, the fluid movement away from the wall decreases the local heat transfer.

Heat transfer in the hydraulic jump region of circular free-surface liquid jets

2020 ◽  
Vol 146 ◽  
pp. 118823 ◽  
Author(s):  
Hossein Askarizadeh ◽  
Hossein Ahmadikia ◽  
Claas Ehrenpreis ◽  
Reinhold Kneer ◽  
Ahmadreza Pishevar ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Free Surface ◽  
Hydraulic Jump ◽  
Liquid Jets ◽  
Surface Liquid
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