Heat Transfer in Compartment Fires Near Regions of Ceiling-Jet Impingement on a Wall

1989 ◽  
Vol 111 (2) ◽  
pp. 455-460 ◽  
Author(s):  
L. Y. Cooper
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Problem Formulation ◽  
Jet Flows ◽  
Fire Plume ◽  
Compartment Fires ◽  
Free Jet ◽  
Wall Impingement ◽  
Energy Release Rates ◽  
Scale Experiment

The problem of heat transfer to walls from fire-plume-driven ceiling jets during compartment fires is introduced. Estimates are obtained for the mass, momentum, and enthalpy flux of the ceiling jet immediately upstream of the ceiling–wall junction. An analogy is drawn between the flow dynamics and heat transfer at ceiling-jet/wall impingement and at the line impingement of a wall and a two-dimensional, plane, free jet. Using the analogy, results from the literature on plane, free-jet flows and corresponding wall-stagnation heat transfer rates are recast into a ceiling-jet/wall-impingement-problem formulation. This leads to a readily usable estimate for the heat transfer from the ceiling jet as it turns downward and begins its initial descent as a negatively buoyant flow along the compartment walls. Available data from a reduced-scale experiment provide some limited verification of the heat transfer estimate. Depending on the proximity of a wall to the point of plume–ceiling impingement, the result indicates that for typical full-scale compartment fires with energy release rates in the range 200–2000 kW and fire-to-ceiling distances of 2–3 m, the rate of heat transfer to walls can be enhanced by a factor of 1.1–2.3 over the heat transfer to ceilings immediately upstream of ceiling-jet impingement.

Large Eddy Simulation of the Heat Transfer Due to Swirling and Non-Swirling Jet Impingement

2008 ◽  
Author(s):  
Naseem Uddin ◽  
S. O. Neumann ◽  
B. Weigand
Keyword(s):  
Heat Transfer ◽  
Turbulence Models ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Test Case ◽  
Complex Flow ◽  
Free Jet ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Target Wall

Turbulent impinging jet is a complex flow phenomenon involving free jet, impingement and subsequent wall jet development zones; this makes it a difficult test case for the evaluation of new turbulence models. The complexity of the jet impingement can be further amplified by the addition of the swirl. In this paper, results of Large Eddy Simulations (LES) of swirling and non-swirling impinging jet are presented. The Reynolds number of the jet based on bulk axial velocity is 23000 and target-to-wall distance (H/D) is two. The Swirl numbers (S) of the jet are 0,0.2, 0.47. In swirling jets, the heat transfer at the geometric stagnation zone deteriorates due to the formation of conical recirculation zone. It is found numerically that the addition of swirl does not give any improvement for the over all heat transfer at the target wall. The LES predictions are validated by available experimental data.

scholarly journals Rotation Effect on Jet Impingement Heat Transfer in Smooth Rectangular Channels with Film Coolant Extraction

2001 ◽  
Vol 7 (2) ◽  
pp. 87-103 ◽  
Author(s):  
James A. Parsons ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Cross Flow ◽  
Flow Distribution ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Jet Flows ◽  
Impingement Heat Transfer ◽  
Rectangular Channels ◽  
Circular Jets ◽  
Target Wall

The effect of channel rotation on jet impingement cooling by arrays of circular jets in twin channels was studied. Impinging jet flows were in the direction of rotation in one channel and opposite to the direction of rotation in the other channel. The jets impinged normally on the smooth, heated target wall in each channel. The spent air exited the channels through extraction holes in each target wall, which eliminates cross flow on other jets. Jet rotation numbers and jet Reynolds numbers varied from 0.0 to 0.0028 and 5000 to 10,000, respectively. For the target walls with jet flow in the direction of rotation (or opposite to the direction of rotation), as rotation number increases heat transfer decreases up to 25% (or 15%) as compared to corresponding results for non-rotating conditions. This is due to the changes in flow distribution and rotation induced Coriolis and centrifugal forces.

scholarly journals Numerical Investigation Of The Impingement Of A Planar Jet of Nanofluids On A V-Shaped Plate

2021 ◽  
Author(s):  
Nishma Bhatt
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Propylene Glycol ◽  
Base Fluid ◽  
Volume Fraction ◽  
Cooling System ◽  
Jet Impingement ◽  
Numerical Code ◽  
Jet Flows ◽  
Transfer Enhancement

An effective way to enhance the heat dissipation in industrial heat transfer devices is impinging of the fluid jet. Due to the higher dissipation heat flux, jet flows can be used for to control the temperature of high intensity heat sources. Traditional fluids such as water, ethylene and propylene glycol, and oils offer heat transfer capabilities that are adequate for many applications. There are several options to increase the effectiveness of the heat transfer characteristics for these fluids, for instance, using jet flows, and increasing the surface area of the heat transfer object. However, with the advances in nanotechnology and material science, nanofluids offer an attractive alternative option. Nanofluids refer to a dispersion of metallic or non-metallic particles with dimensions smaller than 100 nm in a base fluid like water, ethylene and propylene glycol, oil. Nanofluids have been shown to have an enhanced heat transfer characteristic, because of their high thermal conductivity. In this Project, Heat transfer enhancement of an impinging liquid jet on a V-shape target plate cooling system, has been investigated numerically, by replacing the base fluid, water, with Al2O3–water nanofluid. To conduct the research, literature review on nanofluid heat transfer enhancement, jet impingement, and nanofluids jet impingement, has been conducted. Numerical model has been built using ANSYS Workbench 16.0. After validating the numerical code with the previous experimental data, the effect of nanoparticles volume fraction, jet-surface distance and jet’s Reynolds number on the heat transfer enhancement has been investigated

Rotation Effect on Jet Impingement Heat Transfer in Smooth Rectangular Channels With Four Heated Walls and Film Coolant Extraction

2003 ◽  
Author(s):  
James A. Parsons ◽  
Je-Chin Han ◽  
C. Pang Lee
Keyword(s):  
Heat Transfer ◽  
Rotation Number ◽  
Cross Flow ◽  
Jet Impingement ◽  
Jet Flows ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer ◽  
Rectangular Channels ◽  
Circular Jets ◽  
Target Wall

The effect of orthogonal channel rotation on jet impingement cooling by arrays of circular jets in two channels was studied. Impinging jet flows on smooth target walls were in the direction of rotation in one channel and opposite to the direction of rotation in the other channel. Spent air exited the channels through extraction holes in each target wall which eliminates cross flow on other jets. Heat transfer results for these target walls, for the jet walls containing the jet producing orifices, and for the connecting sidewalls show as the jet rotation number increases to 0.0028, these wall Nusselt numbers decrease to 35, 25 and 30%, respectively, below the corresponding non-rotating values. Jet rotation number is a correlating parameter and as wall-to-jet temperature difference ratio increases to 0.129 the wall Nusselt numbers vary up to 10%. Comparisons are made with previous rotating results for target wall heating only and for the radially outward cross flow exit configuration.

A study of free jet impingement. Part 2. Free jet turbulent structure and impingement heat transfer

1971 ◽  
Vol 45 (3) ◽  
pp. 477-512 ◽  
Author(s):  
Coleman Dup. Donaldson ◽  
Richard S. Snedeker ◽  
David P. Margolis
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Correction Factor ◽  
Jet Impingement ◽  
Turbulent Shear ◽  
Axial Distance ◽  
Free Jet ◽  
Impingement Heat Transfer ◽  
Turbulent Characteristics ◽  
Turbulent Jet Flow

An experimental study of jet impingement is completed with the presentation of the measured turbulent characteristics of the circular subsonic jet and the heat transfer rates measured when this jet impinges normal to a flat plate. The data suggest that for impingement very close to the stagnation point, the heat transfer can be computed by applying a turbulent correction factor to the laminar value calculated for a flow having the same pressure distribution as that present in the impingement region. The correction factor is found to be a function of the axial distance and not of Reynolds number. Farther away, the measurements agree well with the heat transfer estimated using the method of Rosenbaum & Donaldson (1967). At large distances from the stagnation point, the heat transfer falls off in inverse proportion with the distance.The documentation of the turbulent jet flow field includes measurements of the radial and axial velocity fluctuations and their spectra, as well as the radial distribution of turbulent shear$\overline{w^{\prime}u^{\prime}}$. In addition, measurements of the turbulence near the stagnation point and the total pressure fluctuation at the stagnation point are presented.

scholarly journals Numerical Investigation Of The Impingement Of A Planar Jet of Nanofluids On A V-Shaped Plate

2021 ◽  
Author(s):  
Nishma Bhatt
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Propylene Glycol ◽  
Base Fluid ◽  
Volume Fraction ◽  
Cooling System ◽  
Jet Impingement ◽  
Numerical Code ◽  
Jet Flows ◽  
Transfer Enhancement

An effective way to enhance the heat dissipation in industrial heat transfer devices is impinging of the fluid jet. Due to the higher dissipation heat flux, jet flows can be used for to control the temperature of high intensity heat sources. Traditional fluids such as water, ethylene and propylene glycol, and oils offer heat transfer capabilities that are adequate for many applications. There are several options to increase the effectiveness of the heat transfer characteristics for these fluids, for instance, using jet flows, and increasing the surface area of the heat transfer object. However, with the advances in nanotechnology and material science, nanofluids offer an attractive alternative option. Nanofluids refer to a dispersion of metallic or non-metallic particles with dimensions smaller than 100 nm in a base fluid like water, ethylene and propylene glycol, oil. Nanofluids have been shown to have an enhanced heat transfer characteristic, because of their high thermal conductivity. In this Project, Heat transfer enhancement of an impinging liquid jet on a V-shape target plate cooling system, has been investigated numerically, by replacing the base fluid, water, with Al2O3–water nanofluid. To conduct the research, literature review on nanofluid heat transfer enhancement, jet impingement, and nanofluids jet impingement, has been conducted. Numerical model has been built using ANSYS Workbench 16.0. After validating the numerical code with the previous experimental data, the effect of nanoparticles volume fraction, jet-surface distance and jet’s Reynolds number on the heat transfer enhancement has been investigated

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