Heat Transfer and Hydraulic Resistance in Turbulent Flow in Vertical Round Tubes At Supercritical Pressures. Part II. Results From Numerical Simulation with Differential Turbulent Viscosity Models

2020 ◽  
Author(s):  
Georgii Glebovich Yankov ◽  
Vladimir Kurganov ◽  
Yury Zeigarnik ◽  
Irina Maslakova
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Turbulent Viscosity ◽  
Turbulence Models ◽  
Model Verification ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Numerical Studies ◽  
Viscosity Models ◽  
Mesh Independence

Abstract The review of numerical studies on the turbulent flow and heat transfer of supercritical pressure (SCP) coolants in heated vertical round tubes, which were conducted using different differential turbulent viscosity models, is presented. It is shown that most often the turbulent viscosity models only qualitatively predict the deteriorated heat transfer effects, which appear due do buoyancy forces and thermal acceleration effects at strongly variable physical properties of a coolant. At the same time, the regimes of normal heat transfer are successfully reproduced by "standard" k- and RNG models with wall functions, as well as by two-layer models. The conclusion is made that none of the presently known turbulent viscosity models can be confidently recommended for predicting any flow regimes and heat transfer of SCP coolants. Strongly variable properties of SCP coolant stipulate more strict demands for validating mesh independence of the obtained results and for an accuracy of approximation of the tabulated values of the coolant properties. It was ascertained that using more and more numerous calculation codes and the results from their application requires certain caution and circumspection. In some works, the parameters of the regimes used for turbulent viscosity model verification and those of the experiments attracted for such verification did not correspond each other. It is pointed out that the crying discrepancy in the predictions of different authors conducted using the same CFD codes and turbulence models and possible reasons for such a discrepancy are not analyzed.

Heat Transfer and Hydraulic Resistance in Turbulent Flow in Vertical Round Tubes At Supercritical Pressures. Part 1. Results From Numerical Simulations Using Algebraic Turbulent Viscosity Models

2020 ◽  
Author(s):  
Georgii Glebovich Yankov ◽  
Vladimir Kurganov ◽  
Yury Zeigarnik ◽  
Irina Maslakova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Turbulent Flow ◽  
Hydraulic Resistance ◽  
Turbulent Viscosity ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Heating And Cooling ◽  
Prediction Techniques ◽  
Vertical Tubes

Abstract The review of numerical studies on supercritical pressure (SCP) coolants heat transfer and hydraulic resistance in turbulent flow in vertical round tubes based on Reynolds-averaged Navier-Stokes (RANS) equations and different models for turbulent viscosity is presented. The paper is the first part of the general analysis, the works based on using algebraic turbulence models of different complexity are considered in it. The main attention is paid to Petukhov-Medvetskaya and Popov et al. models. They were developed especially for simulating heat transfer in tubes of the coolants with significantly variable properties (droplet liquids, gases, SCP fluids) under heating and cooling conditions. These predictions were verified on the entire reliable experimental data base. It is shown that in the case of turbulent flow in vertical round tubes these models make it possible predicting heat transfer and hydraulic resistance characteristics of SCP flows that agree well with the existed reliable experimental data on normal and certain modes of deteriorated heat transfer, if significant influence of buoyancy and radical flow restructuring are absent. For the more complicated cases than a flow in round vertical tubes, as well as for the case of rather strong buoyancy effect, more sophisticated prediction techniques must be applied. The state-of-the-art of these methods and the problems of their application are considered in the Part II of the analysis.

Computations of Turbulent Flow and Heat Transfer in Staggered Tube Banks

1996 ◽  
Author(s):  
M. C. Sharatchandra ◽  
David L. Rhode
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Finite Volume ◽  
Cross Flow ◽  
Turbulence Models ◽  
Curvilinear Coordinates ◽  
Flow And Heat Transfer ◽  
Finite Volume Approach ◽  
Tube Banks ◽  
Limiting Case

Abstract Turbulent Flow in closely spaced staggered tube bundles is numerically investigated using a finite-volume approach in general curvilinear coordinates. Attention if focused on the hydrodynamic and thermal effects of the longitudinal displacement of alternate tube rows. The computations used both standard and 2-layer k–ϵ turbulence models in conjunction with a streamwise periodic finite volume formulation. The computations are in excellent agreement with experimental data for the limiting case of flow and heat transfer in undisplaced tube banks. Furthermore, the results indicate increases in both pressure drop and heat transfer with an increase in displacement. The results of this study may serve as an aid in the design of shell and tube cross flow heat exchangers.

Prediction of Turbulent Flow and Heat Transfer in a Ribbed Rectangular Duct With and Without Rotation

1993 ◽  
Author(s):  
C. Prakash ◽  
R. Zerkle
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Case ◽  
Rectangular Duct ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Smooth Channel

The present study deals with the numerical prediction of turbulent flow and heat transfer in a 2:1 aspect ratio rectangular duct with ribs on the two shorter sides. The ribs are of square cross–section, staggered and aligned normal (90–deg) to the main flow direction. The ratio of rib height to duct hydraulic diameter equals 0.063, and the ratio of rib spacing to rib height equals 10. The duct may be stationary or rotating. The axis of rotation is normal to the axis of the duct and parallel to the ribbed walls (i.e., the ribbed walls form the leading and the trailing faces). The problem is three–dimensional and fully elliptic; hence, for computational economy, the present analysis deals only with a periodically–fully–developed situation where the calculation domain is limited to the region between two adjacent ribs. Turbulence is modelled with the k–epsilon model in conjunction with wall–functions. However, since the rib height is small, use of wall–functions necessitates that the Reynolds number be kept high. (Attempts to use a two–layer model that permits integration to the wall did not yield satisfactory results and such modelling issues are discussed at length). Computations are made here for Reynolds number in the range (30,000–100,000) and for Rotation number=0 (stationary), 0.06, and 0.12. For the stationary case, the predicted heat transfer agrees well with the experimental correlations. Due to the Coriolis induced secondary flow, rotation is found to enhance heat transfer from the trailing and the side walls, while decreasing heat transfer from the leading face. Relative to the corresponding stationary case, the effect of rotation is found to be less for a ribbed channel as compared to a smooth channel.

Computer Simulation of Flow and Heat Transfer in Bare Tubes at Supercritical Parameters

2016 ◽  
Author(s):  
Alexander Zvorykin ◽  
Sergey Aleshko ◽  
Nataliia Fialko ◽  
Nikolay Maison ◽  
Nataliia Meranova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Reynolds Number ◽  
Turbulence Models ◽  
Wall Functions ◽  
Physical Conditions ◽  
Flow And Heat Transfer ◽  
Sst Turbulence Model ◽  
High Reynolds ◽  
Vertical Tubes

This paper deals with CFD predictions for flow and heat transfer in supercritical water in a bare tube. Studies were performed using the software FLUENT for upward flows in vertical tubes with heated length of 4 m and an inner diameter of 10 mm at high values of mass flux (G > 1000 kg/m2s). Turbulence models verification data for the given physical conditions are presented. Besides the testing of different turbulence models that are presented in modern catalog of these models is carried out. Namely, the models related to the following three groups: High–Reynolds number k-ε models with wall functions, k-ω models and Low-Reynolds number k-ε models were considered. On the basis of performed studies the best compliance of known experimental data with computer simulation results fits the k-ω SST turbulence model is shown.

Turbulent Three-Dimensional Air Flow and Heat Transfer in a Cross-Corrugated Triangular Duct

2005 ◽  
Vol 127 (10) ◽  
pp. 1151-1158 ◽  
Author(s):  
Li-Zhi Zhang
Keyword(s):  
Heat Transfer ◽  
Air Flow ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Flat Plates ◽  
Wall Functions ◽  
Mean Values ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Rsm Model

Turbulent complex three-dimensional air flow and heat transfer inside a cross-corrugated triangular duct is numerically investigated. Four turbulence models, the standard k‐ε (SKE), the renormalized group k‐ε, the low Reynolds k‐ω (LKW), and the Reynolds stress models (RSM) are selected, with nonequilibrium wall functions approach (if applicable). The periodic mean values of the friction factor and the wall Nusselt numbers in the hydro and thermally developing entrance region are studied, with the determination of the distribution of time-averaged temperature and velocity profiles in the complex topology. The results are compared with the available experimental Nusselt numbers for cross-corrugated membrane modules. Among the various turbulence models, generally speaking, the RSM model gives the best prediction for 2000⩽Re⩽20,000. However, for 2000⩽Re⩽6000, the LKW model agrees the best with experimental data, while for 6000<Re⩽20,000, the SKE predicts the best. Two correlations are proposed to predict the fully developed periodic mean values of Nusselt numbers and friction factors for Reynolds numbers ranging from 2000 to 20,000. The results are that compared to parallel flat plates, the corrugated ducts could enhance heat transfer by 40 to 60%, but with a 2 times more pressure drop penalty. The velocity, temperature, and turbulence fields in the flow passages are investigated to give some insight into the mechanisms for heat transfer enhancement.

Numerical Modelling of Flow and Heat Transfer From an Array of Jets Impinging Onto a Concave Surface Under Stationary and Rotating Conditions

2008 ◽  
Author(s):  
Tim J. Craft ◽  
Hector Iacovides ◽  
Nor A. Mostafa
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Wall Layer ◽  
Wall Functions ◽  
Turbine Blade Cooling ◽  
Round Jets ◽  
Flow And Heat Transfer ◽  
Viscosity Models ◽  
Flow Features ◽  
Circular Surface

The paper reports computations of the flow and heat-transfer from an array of five round jets impinging onto a concave semi-circular surface, under both stationary and rotating conditions. The geometry is designed to reproduce important flow features found in internal turbine blade cooling applications. Linear and non-linear eddy-viscosity models are applied, with wall-functions to cover the near-wall layer, and are shown to capture many of the overall flow characteristics under stationary conditions, although greater discrepancies are found in rotating cases. The standard, log-law based, form of wall-function is found to be inadequate in predicting the heat-transfer, and a more advanced form developed at Manchester (the AWF) is also tested, and shown to lead to better heat transfer results.

scholarly journals Three-dimensional numerical investigation of turbulent flow and heat transfer inside a horizontal semi-circular cross-sectioned duct

2014 ◽  
Vol 18 (4) ◽  
pp. 1145-1158 ◽  
Author(s):  
Kamil Arslan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Forced Flow ◽  
Flow And Heat Transfer ◽  
Darcy Friction Factor

In this study, steady-state turbulent forced flow and heat transfer in a horizontal smooth semi-circular cross-sectioned duct was numerically investigated. The study was carried out in the turbulent flow condition where Reynolds numbers range from 1?104 to 5.5?104. Flow is hydrodynamically and thermally developing (simultaneously developing flow) under uniform surface heat flux with uniform peripheral wall heat flux (H2) boundary condition on the duct?s wall. A commercial CFD program, Ansys Fluent 12.1, with different turbulent models was used to carry out the numerical study. Different suitable turbulence models for fully turbulent flow (k-? Standard, k-? Realizable, k-? RNG, k-? Standard and k-? SST) were used in this study. The results have shown that as the Reynolds number increases Nusselt number increases but Darcy friction factor decreases. Based on the present numerical solutions, new engineering correlations were presented for the average Nusselt number and average Darcy friction factor. The numerical results for different turbulence models were compared with each other and similar experimental investigations carried out in the literature. It is obtained that, k-? Standard, k-? Realizable and k-? RNG turbulence models are the most suitable turbulence models for this investigation. Isovel contours of velocity magnitude and temperature distribution for different Reynolds numbers, turbulence models and axial stations in the duct were presented graphically. Also, local heat transfer coefficient and local Darcy friction factor as function of dimensionless position along the duct were obtained in this investigation.

Heat Transfer in a Suddenly Expanded Turbulent Flow Past a Porous Insert Using Linear and Non-Linear Eddy-Viscosity Models

2002 ◽  
Author(s):  
Marcelo J. S. de Lemos ◽  
Marcelo Assato
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Eddy Viscosity ◽  
Control Volume ◽  
Numerical Technique ◽  
Turbulence Models ◽  
Wall Functions ◽  
Porous Insert ◽  
Flow Past ◽  
Non Linear

This work presents numerical results for heat transfer in turbulent flow past a backward-facing-step channel with a porous insert using linear and non-linear eddy viscosity macroscopic models. The non-linear turbulence models are known to perform better than classical eddy-diffusivity models due to their ability to simulate important characteristics of the flow. Parameters such as porosity, permeability and thickness of the porous insert are varied in order to analyze their effects on the flow pattern, particularly on the damping of the recirculating bubble after the porous insertion. The numerical technique employed for discretizing the governing equations is the control-volume method. The SIMPLE algorithm is used to correct the pressure field. Wall functions for velocity and temperature are used in order to bypass fine computational close to the wall. Comparisons of results simulated with both linear and non-linear turbulence models are presented.

Prediction of Turbulent Flow and Heat Transfer in a Ribbed Rectangular Duct With and Without Rotation

1995 ◽  
Vol 117 (2) ◽  
pp. 255-264 ◽  
Author(s):  
C. Prakash ◽  
R. Zerkle
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Case ◽  
Rectangular Duct ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Smooth Channel

The present study deals with the numerical prediction of turbulent flow and heat transfer in a 2:1 aspect ratio rectangular duct with ribs on the two shorter sides. The ribs are of square cross section, staggered and aligned normal (90 deg) to the main flow direction. The ratio of rib height to duct hydraulic diameter equals 0.063, and the ratio of rib spacing to rib height equals 10. The duct may be stationary or rotating. The axis of rotation is normal to the axis of the duct and parallel to the ribbed walls (i.e., the ribbed walls form the leading and the trailing faces). The problem is three dimensional and fully elliptic; hence, for computational economy, the present analysis deals only with a periodically fully developed situation where the calculation domain is limited to the region between two adjacent ribs. Turbulence is modeled with the k–ε model in conjunction with wall functions. However, since the rib height is small, use of wall functions necessitates that the Reynolds number be kept high. (Attempts to use a two-layer model that permits integration to the wall did not yield satisfactory results and such modeling issues are discussed at length.) Computations are made here for Reynolds number in the range 30,000–100,000 and for Rotation number = 0 (stationary), 0.06, and 0.12. For the stationary case, the predicted heat transfer agrees well with the experimental correlations. Due to the Coriolis-induced secondary flow, rotation is found to enhance heat transfer from the trailing and the side walls, while decreasing heat transfer from the leading face. Relative to the corresponding stationary case, the effect of rotation is found to be less for a ribbed channel as compared to a smooth channel.

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