Numerical Investigation of Flow Field and Heat Transfer in Cross-Corrugated Ducts

1999 ◽  
Vol 121 (2) ◽  
pp. 314-321 ◽  
Author(s):  
H. Blomerius ◽  
C. Ho¨lsken ◽  
N. K. Mitra
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Critical Reynolds Number ◽  
Wave Length ◽  
Reynolds Numbers ◽  
Sine Wave ◽  
Transitional Flow ◽  
Navier Stokes ◽  
Flow Oscillations ◽  
Energy Equations

Flow field and heat transfer in sine-wave crossed-corrugated ducts have been investigated by numerical solution of the Navier-Stokes and energy equations in the laminar and transitional flow regime between Re = 170 and 2000. The ratio of the corrugation wave length λ* to amplitude a* has been varied between 7 and 10. The angle of the corrugation of the neighboring plates has been kept fixed at 45 deg. Results show that the critical Reynolds number for self-sustained flow oscillations is about 240. For Reynolds numbers larger than 1000, the Nusselt number and the friction factor are nearly independent of the dimensionless wavelength. Computational results compare well with available experimental results.

scholarly journals Multiple Solutions in Fluid Dynamics

2009 ◽  
Vol 14 (2) ◽  
pp. 263-279
Author(s):  
L.-S. Yao
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Reynolds Number ◽  
Flow Field ◽  
Multiple Solutions ◽  
Fluid Flows ◽  
Critical Value ◽  
Navier Stokes ◽  
Energy Equations

The principle of multiple solutions of the Navier-Stokes and energy equations discussed in this paper is not directed at any particular problems in fluid dynamics and heat transfer, or at any specific applications. The non-uniqueness principle states that the Reynolds number, above its critical value, is insufficient to uniquely determine a flow field for a given geometry, or for similar geometries. It is a generic principle for all fluid flows and its transportation properties, but is not well known. It compliments the current popular bifurcation theories by the fact that multiple solutions can exist on each stable bifurcation branch.

Unsteady Heat Transfer in Baffled Channels

1996 ◽  
Vol 118 (3) ◽  
pp. 585-591 ◽  
Author(s):  
G. Wang ◽  
K. Stone ◽  
S. P. Vanka
Keyword(s):  
Heat Transfer ◽  
Critical Reynolds Number ◽  
Reynolds Numbers ◽  
Process Industry ◽  
Unsteady Heat Transfer ◽  
Enhancement Of Heat Transfer ◽  
Compact Heat Exchangers ◽  
Unsteady Fluid Flow ◽  
Unsteady Fluid ◽  
Energy Equations

In this paper, the enhancement of heat transfer due to unsteady flow in channels with in-line and staggered baffles is investigated through the numerical solution of the governing unsteady fluid flow and energy equations with periodicity in the stream wise direction. For the inline configuration, the flow becomes naturally unsteady at a critical Reynolds number (Q/v) around 110. For the staggered case, this value is around 200. Significant increases in heat transfer rate are observed once the flow becomes unsteady. Results for several Reynolds numbers up to 500 are presented. The present results can be valuable to the design and operation of compact heat exchangers used in process industry.

Fast forced liquid film spreading on a substrate: flow, heat transfer and phase transition

2010 ◽  
Vol 656 ◽  
pp. 189-204 ◽  
Author(s):  
ILIA V. ROISMAN
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Stokes Equations ◽  
Substrate Surface ◽  
Reynolds Numbers ◽  
Drop Impact ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Theoretical Predictions ◽  
Viscous Drop

This theoretical study is devoted to description of fluid flow and heat transfer in a spreading viscous drop with phase transition. A similarity solution for the combined full Navier–Stokes equations and energy equation for the expanding lamella generated by drop impact is obtained for a general case of oblique drop impact with high Weber and Reynolds numbers. The theory is applicable to the analysis of the phenomena of drop solidification, target melting and film boiling. The theoretical predictions for the contact temperature at the substrate surface agree well with the existing experimental data.

Investigating Gas Turbine Internal Cooling Using Supercritical CO2 at High Reynolds Numbers for Direct Fired Cycle Applications

2021 ◽  
Author(s):  
Matthew Searle ◽  
Arnab Roy ◽  
James Black ◽  
Doug Straub ◽  
Sridharan Ramesh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Gas Turbines ◽  
Cfd Simulation ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Process Conditions ◽  
Internal Cooling ◽  
Air Breathing

Abstract In this paper, experimental and numerical investigations of three variants of internal cooling configurations — dimples only, ribs only and ribs with dimples have been explored at process conditions (96°C and 207bar) with sCO2 as the coolant. The designs were chosen based on a review of advanced internal cooling features typically used for air-breathing gas turbines. The experimental study described in this paper utilizes additively manufactured square channels with the cooling features over a range of Reynolds number from 80,000 to 250,000. Nusselt number is calculated in the experiments utilizing the Wilson Plot method and three heat transfer characteristics — augmentation in Nusselt number, friction factor and overall Thermal Performance Factor (TPF) are reported. To explore the effect of surface roughness introduced due to additive manufacturing, two baseline channel flow cases are considered — a conventional smooth tube and an additively manufactured square tube. A companion computational fluid dynamics (CFD) simulation is also performed for the corresponding cooling configurations reported in the experiments using the Reynolds Averaged Navier Stokes (RANS) based turbulence model. Both experimental and computational results show increasing Nusselt number augmentation as higher Reynolds numbers are approached, whereas prior work on internal cooling of air-breathing gas turbines predict a decay in the heat transfer enhancement as Reynolds number increases. Comparing cooling features, it is observed that the “ribs only” and “ribs with dimples” configurations exhibit higher Nusselt number augmentation at all Reynolds numbers compared to the “dimples only” and the “no features” configurations. However, the frictional losses are almost an order of magnitude higher in presence of ribs.

Numerical Modeling of Radiative and Reactive Flow Field Around a Blunt Body at Hypersonic Regimes

2010 ◽  
Author(s):  
Morteza Rahmanpour ◽  
Reza Ebrahimi ◽  
Mehrzad Shams
Keyword(s):  
Flow Field ◽  
Differential Equations ◽  
Heat Fluxes ◽  
Transitional Flow ◽  
Navier Stokes ◽  
Implicit Time ◽  
Discrete Ordinates ◽  
Two Dimensional ◽  
Fully Implicit ◽  
Time Marching

A numerical method for calculation of strong radiation for two-dimensional reactive air flow field is developed. The governing equations are taken to be two dimensional, compressible Reynolds-average Navier-Stokes and species transport equations. Also, radiation heat flux in energy equation is evaluated using a model of discrete ordinate method. The model used S4 approximation to reduce the governing system of integro-differential equations to coupled set of partial differential equations. A multiband model is used to construct absorption coefficients. Tangent slab approximation is assumed to determine the characteristic parameters needed in the Discrete Ordinates Method. The turbulent diffusion and heat fluxes are modeled by Baldwin and Lomax method. The flow solution is obtained with a fully implicit time marching method. A thermochemical nonequilibrium formulation appropriate to hypersonic transitional flow of air is presented. The method is compared with existing experimental results and good agreement is observed.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

Improving the performance of the condenser fan in a subway train against the effects of crosswind flow by placing barriers

2019 ◽  
Vol 234 (2) ◽  
pp. 214-225
Author(s):  
Reza NB Abadi ◽  
Mahdi Deymi-Dashtebayaz ◽  
Niki Rezazadeh
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Velocity Profile ◽  
Air Temperature ◽  
Rotating Flows ◽  
Navier Stokes ◽  
Rotational Flow ◽  
Parallel Lines ◽  
Subway Train ◽  
Energy Equations

In this paper, the effect of crosswind flow and barrier placement on the performance of the condenser fan in a subway train is investigated. In addition, the amount of heat transfer on the condenser tubes is also analyzed. At different velocities of the train, variations in the velocity profile and drag force are determined for various geometries including triangular, rectangular, symmetric triangular barriers, and a barrier with parallel lines outside of the fan. Navier–Stokes, energy equations, and k– ω turbulence model have been used for the numerical modeling of the turbulent and incompressible flow. The results show that due to the created vortices behind the triangular and rectangular barriers, a negative velocity on the outflow of the fan is observed. Also, the symmetric triangular barrier minimizes the rotational flow on the top of the fan, and parallel paths have the most impact on the improvement of the fan's performance due to the elimination of all rotating flows. Finally, variations in temperature on the condenser tubes in the presence of barriers that are placed in the middle gap between the holes on the top of the condenser tubes are determined. These barriers move the crosswind flow toward the condenser tubes and decrease the output air temperature of the condenser.

scholarly journals Calculation of Convective Heat Transfer in Square-Sectioned Gas Turbine Blade Cooling Channels

1998 ◽  
Author(s):  
Arash Saidi ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Cross Sections ◽  
Turbine Blades ◽  
Solution Procedure ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Turbine Blade Cooling ◽  
Cooling Channels ◽  
Energy Equations

Internal cooling channels are commonly used to reduce the thermal loads on the gas turbine blades to improve overall efficiency. In this study a numerical investigation has been carried out to provide a validated and consistent method to deal with the prediction of the fluid flow and the heat transfer of such channels with square cross sections. The rotation modified Navier-Stokes and energy equations together with a low-Re number version of the k-ε turbulence model are solved with appropriate boundary conditions. The solution procedure is based on a numerical method using a collocated grid, and the pressure-velocity coupling is handled by the SIMPLEC algorithm. The computations are performed with the assumption of fully developed periodic conditions. The calculations are carried out for smooth ducts with and without rotation and effects of rotation on the heat transfer are described. Similar numerical calculations have carried out for channels with rib-roughened walls. The obtained results are compared with available experimental data and empirical correlations for the heat transfer rate and the friction factor. Some details of the flow and heat transfer fields are also presented.

Characteristics of Fully Developed Flow and Heat Transfer in Channels With Varying Wall Geometry

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Abhishek G. Ramgadia ◽  
Arun K. Saha
Keyword(s):  
Heat Transfer ◽  
Time Dependent ◽  
Navier Stokes ◽  
Fully Developed Flow ◽  
Flow And Heat Transfer ◽  
Collocated Grid ◽  
Wall Profile ◽  
Energy Equations ◽  
Volume Method ◽  
Wall Geometry

Present study focuses on numerical investigation of fully developed flow and heat transfer through three channels having sine-shaped, triangle-shaped, and arc-shaped wall profiles. All computations are performed at Reynolds number of 600. Finite volume method on collocated grid is used to solve the time-dependent Navier–Stokes and energy equations in primitive variable form. For all the geometries considered in the study, the ratios Hmin/Hmax and L/a are kept fixed to 0.4 and 8.0, respectively. The thermal performances of all the three wall configurations are assessed using integral parameters as well as instantaneous, time-averaged and fluctuating flow fields. The geometry with the sinusoidal-shaped wall profile is found to produce the best thermal properties as compared to the triangle-shaped and the arc-shaped profiles though the obtained heat transfer is the highest for the arc-shaped geometry.

scholarly journals A Comparison of Experimental and Computational Heat Transfer Results for a Leading Edge Impingement System

2018 ◽  
Vol 3 (4) ◽  
pp. 23
Author(s):  
Robert Pearce ◽  
Peter Ireland ◽  
Ed Dane ◽  
Janendra Telisinghe
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbine Blades ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
High Heat ◽  
Navier Stokes ◽  
Spatially Resolved ◽  
Computational Fluid Dynamics Simulations ◽  
Dynamics Simulations

Leading edge impingement systems are increasingly being used for high pressure turbine blades in gas turbine engines, in regions where very high heat loads are encountered. The flow structure in such systems can be very complex and high resolution experimental data is required for engine-realistic systems to enable code validation and optimal design. This paper presents spatially resolved heat transfer distributions for an engine-realistic impingement system for multiple different hole geometries, with jet Reynolds numbers in the range of 13,000–22,000. Following this, Reynolds-averaged Navier-Stokes computational fluid dynamics simulations are compared to the experimental data. The experimental results show variation in heat transfer distributions for different geometries, however average levels are primarily dependent on jet Reynolds number. The computational simulations match the shape of the distributions well however with a consistent over-prediction of around 10% in heat transfer levels.

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