Numerical Analysis of Heat Transfer During Jet Impingement on Curved Surfaces

Numerical Analysis of Heat Transfer During Jet Impingement on Curved Surfaces
Author: Cesar F. Hernandez-Ontiveros
Publisher:
Total Pages:
Release: 2007
Genre:
ISBN:

ABSTRACT: The flow structure and convective heat transfer behavior of a free liquid jet ejecting from a round nozzle impinging vertically on a hemispherical solid plate and a slot nozzle impinging vertically on a cylindrical curved plate have been studied using a numerical analysis approach. The simulation model incorporated the entire fluid region and the solid hemisphere or curved plate. Solution was done for both isothermal and constant heat flux boundary conditions at the inner surface of the hemispherical plate and the constant heat flux boundary condition at the inner surface of the cylindrical shaped plate. Computations for the round nozzle impinging jet on the hemispherical plate and cylindrical plate were done for jet Reynolds number (ReJ) ranging from 500 to 2000, dimensionless nozzle to target spacing ratio (β) from 0.75 to 3, and for various dimensionless plate thicknesses to diameter nozzle ratio (b/dn) from 0.083-1.5. Also, computations for the slot nozzle impinging jet on the cylindrical plate were done for inner plate radius of curvature to nozzle diameter ratio (Ri/dn) of 4.16-16.66, plate thickness to nozzle diameter ratio (b/dn) of 0.08-1.0, and different nozzle diameters (dn), Results are presented for dimensionless solid-fluid interface temperature, dimensionless maximum temperature in the solid, local and average Nusselt numbers using the following fluids: water (H2O), flouroinert (FC-77), and oil (MIL-7808) and the following solid materials: aluminum, copper, Constantan, silver, and silicon. Materials with higher thermal conductivity maintained a more uniform temperature distribution at the solid-fluid interface. A higher Reynolds number increased the Nusselt number over the entire solid-fluid interface. Local and average Nusselt number and heat transfer coefficient distributions showed a strong dependence on the impingement velocity or Reynolds number. As the velocity increases, the local Nusselt number increases over the entire solid-fluid interface. Decreasing the nozzle to target spacing favors the increasing of the Nusselt number. Increasing the nozzle diameter decreases the temperature at the curved plate outer surface and increases the local Nusselt number. Similarly, local and average Nusselt number was enhanced by decreasing plate thickness. Numerical simulation results are validated by comparing with experimental measurements and related correlations.

Impingement Jet Cooling in Gas Turbines

Impingement Jet Cooling in Gas Turbines
Author: R.S. Amano
Publisher: WIT Press
Total Pages: 253
Release: 2014-05-28
Genre: Science
ISBN: 1845649060

Due to the requirement for enhanced cooling technologies on modern gas turbine engines, advanced research and development has had to take place in field of thermal engineering. Among the gas turbine cooling technologies, impingement jet cooling is one of the most effective in terms of cooling effectiveness, manufacturability and cost. The chapters contained in this book describe research on state-of-the-art and advanced cooling technologies that have been developed, or that are being researched, with a variety of approaches from theoretical, experimental, and CFD studies. The authors of the chapters have been selected from some of the most active researchers and scientists on the subject. This is the first to book published on the topics of gas turbines and heat transfer to focus on impingement cooling alone.

Heat Transfer Analysis of Slot Jet Impingement Onto Roughened Surfaces

Heat Transfer Analysis of Slot Jet Impingement Onto Roughened Surfaces
Author: Rashid Ali Alshatti
Publisher:
Total Pages:
Release: 2015
Genre: Mechanical engineering
ISBN:

The effect of surface roughness on jet impingement heat transfer was investigated in this research. A numerical analysis was conducted for free surface slot jet impinging normally onto a heated plate. Six different geometries and three different plate materials were investigated. The cooling fluid used for the analysis was water, and the flow was laminar with a range of Reynolds number (Re) from 500 to 1000. Temperature distribution, local and average heat transfer coefficient, and local and average Nusselt number were presented for each case. The steady state heat transfer results show that the increase in Reynolds number (Re) increases the local heat transfer coefficient and the local Nusselt number. Impinging the jet nozzle directly onto a step has a better heat transfer enhancement than impinging the jet nozzle in between steps. Materials with low thermal conductivity exhibit large variation in temperature along the solid-fluid interface. The variations of the interface temperature become smaller between all cases when applying the isothermal boundary condition. The transient heat transfer results show that the temperature of the interface increases with time until steady state condition is met. Materials with high thermal diffusivity reach the steady state condition with less time. The increase in surface roughness increases the time required to reach the steady state condition. The highest rates of heat transfer were found at locations where no fluid recirculation occurs. It takes less time to reach steady state condition when applying the isothermal boundary condition at the bottom surface of the plate.

Three-Dimensional Attached Viscous Flow

Three-Dimensional Attached Viscous Flow
Author: Ernst Heinrich Hirschel
Publisher: Springer Science & Business Media
Total Pages: 396
Release: 2013-10-29
Genre: Technology & Engineering
ISBN: 3642413781

Viscous flow is treated usually in the frame of boundary-layer theory and as two-dimensional flow. Books on boundary layers give at most the describing equations for three-dimensional boundary layers, and solutions often only for some special cases. This book provides basic principles and theoretical foundations regarding three-dimensional attached viscous flow. Emphasis is put on general three-dimensional attached viscous flows and not on three-dimensional boundary layers. This wider scope is necessary in view of the theoretical and practical problems to be mastered in practice. The topics are weak, strong, and global interaction, the locality principle, properties of three-dimensional viscous flow, thermal surface effects, characteristic properties, wall compatibility conditions, connections between inviscid and viscous flow, flow topology, quasi-one- and two-dimensional flows, laminar-turbulent transition and turbulence. Though the primary flight speed range is that of civil air transport vehicles, flows past other flying vehicles up to hypersonic speeds are also considered. Emphasis is put on general three-dimensional attached viscous flows and not on three-dimensional boundary layers, as this wider scope is necessary in view of the theoretical and practical problems that have to be overcome in practice. The specific topics covered include weak, strong, and global interaction; the locality principle; properties of three-dimensional viscous flows; thermal surface effects; characteristic properties; wall compatibility conditions; connections between inviscid and viscous flows; flow topology; quasi-one- and two-dimensional flows; laminar-turbulent transition; and turbulence. Detailed discussions of examples illustrate these topics and the relevant phenomena encountered in three-dimensional viscous flows. The full governing equations, reference-temperature relations for qualitative considerations and estimations of flow properties, and coordinates for fuselages and wings are also provided. Sample problems with solutions allow readers to test their understanding.

Numerical Simulations of Heat Transfer Processes in a Dehumidifying Wavy Fin and a Confined Liquid Jet Impingement on Various Surfaces

Numerical Simulations of Heat Transfer Processes in a Dehumidifying Wavy Fin and a Confined Liquid Jet Impingement on Various Surfaces
Author: Mutasim Mohamed Sarour Elsheikh
Publisher:
Total Pages:
Release: 2011
Genre:
ISBN:

The results demonstrate that the overall fin efficiency is dependent on the relative humidity of the surrounding air and the total surface area of the fin. In addition, the findings of the present work are in good agreement with experimental data. The second problem investigated is the heat transfer analysis of confined liquid jet impingement on various surfaces. The objective of this computational study is to characterize the convective heat transfer of a confined liquid jet impinging on a curved surface of a solid body, while the body is being supplied with a uniform heat flux at its opposite flat surface. Both convex and concave configurations of the curved surface are investigated. The confinement plate has the same shape as the curved surface. Calculations were done for various solid materials, namely copper, aluminum, Constantan, and silicon; at two-dimensional jet. For this research, Reynolds numbers ranging from 750 to 2000 for various nozzle widths channel spacing, radii of curvature, and base thicknesses of the solid body, were used. Results are presented in terms of dimensionless solid-fluid interface temperature, heat transfer coefficient, and local and average Nusselt numbers. The increments of Reynolds numbers increase local Nusselt numbers over the entire solid-fluid interface. Decreasing the nozzle width, channel spacing, plate thickness or curved surface radius of curvature all enhanced the local Nusselt number. Results show that a convex surface is more effective compared to a flat or concave surface. Numerical simulation results are validated by comparing them with experimental data for flat and concave surfaces.

Handbook of Hydraulic Resistance

Handbook of Hydraulic Resistance
Author: I. E. Idelchik
Publisher:
Total Pages: 0
Release: 2005
Genre: Fluid dynamics
ISBN: 9788179921180

The handbook has been composed on the basis of processing, systematization and classification of the results of a great number of investigations published at different time. The essential part of the book is the outcome of investigations carried out by the author. The present edition of this handbook should assist in increasing the quality and efficiency of the design and usage of indutrial power engineering and other constructions and also of the devices and apparatus through which liquids and gases move.

Food Engineering: Integrated Approaches

Food Engineering: Integrated Approaches
Author: Gustavo F. Gutiérrez-Lopez
Publisher: Springer Science & Business Media
Total Pages: 475
Release: 2008-02-29
Genre: Technology & Engineering
ISBN: 038775430X

This book presents a significant and up-to-date review of various integrated approaches to food engineering. Distinguished food engineers and food scientists from key institutions worldwide have contributed chapters that provide a deep analysis of their particular subjects. Emerging technologies and biotechnology are introduced, and the book discusses predictive microbiology, packing materials for foods, and biodegradable films. This book is mainly directed to academics, and to undergraduate and postgraduate students in food engineering and food science and technology, who will find a selection of topics.

Experimental and Numerical Investigation of Heat and Mass Transfer Due to Pulse Combustor Jet Impingement

Experimental and Numerical Investigation of Heat and Mass Transfer Due to Pulse Combustor Jet Impingement
Author: Michael J. Psimas
Publisher:
Total Pages:
Release: 2010
Genre: Drying apparatus
ISBN:

Under certain circumstances pulse combustors have been shown to improve both heat transfer and drying rate when compared to steady flow impingement. Despite this potential, there have been few investigations into the use of pulse combustor driven impingement jets for industrial drying applications. The research presented here utilized experimental and numerical techniques to study the heat transfer characteristics of these types of oscillating jets when impinging on solid surfaces and the heat and mass transfer when drying porous media. The numerical methods were extensively validated using laboratory heat flux and drying data, as well as correlations from literature. As a result, the numerical techniques and methods that were developed and employed in this work were found to be well suited for the current application. It was found that the pulsating flows yielded elevated heat and mass transfer compared to similar steady flow jets. However, the numerical simulations were used to analyze not just the heat flux or drying, but also the details of the fluid flow in the impingement zone that resulted in said heat and mass transport. It was found that the key mechanisms of the enhanced transfer were the vortices produced by the oscillating flow. The characteristics of these vortices such as the size, strength, location, duration, and temperature, determined the extent of the improvement. The effects of five parameters were studied: the velocity amplitude ratio, oscillation frequency, the time-averaged bulk fluid velocity at the tailpipe exit, the hydraulic diameter of the tailpipe, and the impingement surface velocity. Analysis of the resulting fluid flow revealed three distinct flow types as characterized by the vortices in the impingement zone, each with unique heat transfer characteristics. These flow types were: a single strong vortex that dissipated before the start of the next oscillation cycle, a single persistent vortex that remained relatively strong at the end of the cycle, and a strong primary vortex coupled with a short-lived, weaker secondary vortex. It was found that the range over which each flow type was observed could be classified into distinct flow regimes. The secondary vortex and persistent vortex regimes were found to enhance heat transfer. Subsequently, transition criteria dividing these regimes were formed based on dimensionless parameters. The critical dimensionless parameters appeared to be the Strouhal number, a modified Strouhal number, the Reynolds number, the velocity amplitude ratio, and the H/Dh ratio. Further study would be required to determine if these parameters offer similar significance for other configurations.