Optimization of Three-Dimensional Angled Ribs With RANS Analysis of Turbulent Heat Transfer

2004 ◽  
Author(s):  
Hong-Min Kim ◽  
Kwang-Yong Kim
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Optimization Procedure ◽  
Local Heat ◽  
Weighting Factor ◽  
Turbulent Heat Transfer ◽  
Channel Height ◽  
Turbulent Heat ◽  
Height Ratio

A numerical optimization procedure for the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer is presented. The response surface based global optimization with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer is used. Shear stress transport (SST) turbulence model is used as a turbulence closure. Computational results for local heat transfer rate show a reasonable agreement with the experimental data. The pitch-to-height ratio of the rib and rib height-to-channel height ratio are set to be 9.0 and 0.1, respectively, and width-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with the weighting factor. Full-factorial experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained in the range from 0.0 to 0.1 of the weighting factor.

scholarly journals Numerical Simulation of Turbulent Heat Transfer and Flow in a Rotating Multiple-Pass Square Channel

1997 ◽  
Author(s):  
Jenn-Jiang Hwang ◽  
Wei-Jyh Wang ◽  
Dong-Yuo Lai
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Constant Heat Flux ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Straight Channel ◽  
Turbulent Fluid Flow ◽  
Square Channel

Three-dimensional turbulent fluid flow and heat transfer characteristics are analyzed numerically for fluids flowing through a rotating periodical two-pass square channel. The two-pass channel is characterized by three parts: (1) a radial-inward straight channel, (2) 180-deg sharp turns, and (3) a radial-outward straight channel. The smooth walls of the two-pass channel are subject to a constant heat flux. A two-equation k-ε turbulence model with modified terms for Coriolis and rotational buoyancy is employed to resolve this elliptic problem. The effects of rotational buoyancy are examined and discussed. It is found that adjacent the 180-deg turn, the rotational buoyancy effect on the local heat transfer is nearly negligible due to the relatively strong entrance effect of 180-deg turns. Downstream the entrance length, the changes in local heat transfer due to the rotational buoyancy in the radially outward flow are more significant than those in the radially inward flow. However, the channel averaged heat transfer is affected slightly by the rotational buoyancy. Whenever the buoyancy effects are sufficiently strong, the flow reversal appears over the leading face of the radial outward flow channel. A comparison of the present numerical results with the available experimental data by taking buoyancy into consideration is also presented.

Numerical and Experimental Study of Turbulent Heat Transfer and Fluid Flow in Longitudinal Fin Arrays

1986 ◽  
Vol 108 (1) ◽  
pp. 16-23 ◽  
Author(s):  
D. S. Kadle ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Base Plate ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Numerical Work ◽  
Model Average ◽  
Air Stream

Heat transfer from an array of parallel longitudinal fins to a turbulent air stream passing through the interfin spaces has been investigated both analytically/numerically and experimentally. The fins were integrally attached to a heated base plate, while the fin tips were shrouded to avoid leakage. In the analytical/numerical work, a conjugate problem was solved which encompassed turbulent flow and heat transfer in the air stream and heat conduction in the fins and in the base plate. The turbulence model and computational scheme were verified by comparison with experiment. It was found that the local heat transfer coefficients varied along the fins and along the surface of the base plate, with the lowest values in the corners formed by the fin/base plate intersections and the fin/shroud intersections. The numerically determined fin efficiencies did not differ appreciably from those calculated from the conventional pure-conduction fin model. Average Nusselt numbers, evaluated from the experimental data in conjunction with the numerically determined fin efficiencies (for derating the fin surface area), agreed well with those for fully developed heat transfer in a uniformly heated circular tube.

Maldistributed Inlet Flow Effects on Turbulent Heat Transfer and Pressure Drop in a Flat Rectangular Duct

1983 ◽  
Vol 105 (3) ◽  
pp. 527-535 ◽  
Author(s):  
E. M. Sparrow ◽  
N. Cur
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Rectangular Duct ◽  
Transfer Coefficients ◽  
Inlet Flow ◽  
Heat Transfer Coefficients ◽  
Flow Maldistribution

The effects of flow maldistribution caused by partial blockage of the inlet of a flat rectangular duct were studied experimentally. Local heat transfer coefficients were measured on the principal walls of the duct for two blockages and for Reynolds numbers spanning the range between 6000 and 30,000. Measurements were also made of the pressure distribution along the duct, and the fluid flow pattern was visualized by the oil-lampblack technique. Large spanwise nonuniformities of the local heat transfer coefficient were induced by the maldistributed flow. These nonuniformities persisted to far downstream locations, especially in the presence of severe inlet flow maldistributions. Spanwise-average heat transfer coefficients, evaluated from the local data, were found to be enhanced in the downstream portion of the duct due to the flow maldistribution. However, at more upstream locations, where the entering flow reattached to the duct wall following its separation at the sharp-edged inlet, the average coefficients were reduced by the presence of the maldistribution.

scholarly journals Steady interaction of a turbulent plane jet with a rectangular heated cavity

2016 ◽  
Vol 20 (5) ◽  
pp. 1485-1498
Author(s):  
Farida Iachachene ◽  
Amina Mataoui ◽  
Yacine Halouane
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Structure ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heated Wall ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Potential Core

Turbulent heat transfer between a confined jet flowing in a hot rectangular cavity is studied numerically by finite volume method using the k-w SST one point closure turbulence model. The location of the jet inside the cavity is chosen so that the flow is in the non-oscillation regime. The flow structure is described for different jet-to-bottom-wall distances. A parametrical study was conducted to identify the influence of the jet exit location and the Reynolds number on the heat transfer coefficient. The parameters of this study are: the jet exit Reynolds number (Re, 1560< Re <33333), the temperature difference between the cavity heated wall and the jet exit (DT=60?C) and the jet location inside the cavity (Lf, 2? Lf? 10 and Lh 2.5<Lh?10). The Nusselt number increased and attained its maximum value at the stagnation points and then decreased. The flow structure is found in good agreement with the available experimental data. The maximum local heat transfer between the cavity walls and the flow occurs at the potential core end. The ratio between the stagnation point Nusselt numbers of the cavity bottom (NuB0) to the maximum Nusselt number on the lateral cavity wall (NuLmax) decreased with the Reynolds number for all considered impinging distances. For a given lateral confinement, the stagnation Nusselt number of the asymmetrical interaction Lh?10 is almost equal to that of the symmetrical interaction Lh=10.

Heat Transfer Prediction of a Jet Impinging a Cylindrical Deadlock Area

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Yacine Halouane ◽  
Amina Mataoui ◽  
Farida Iachachene
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Behavior ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Potential Core ◽  
Numerical Predictions

The turbulent heat transfer by a confined jet flowing inside a hot cylindrical cavity is investigated numerically in this paper. This configuration is found in several engineering applications such as air conditioning and the ventilation of mines, deadlock, or corridors. The parameters investigated in this work are the Reynolds number (Re, 20,000 ≤ Re ≤ 50,000) and the normalized distance Lf between jet exit and the cavity bottom (Lf, 2 ≤ Lf  ≤ 12). The numerical predictions are performed by finite volume method using the second order one-point closure turbulence model (RSM). The Nusselt number increases and attains maximum values at stagnation points, after it decreases. For an experimental test case available in the literature Lf = 8, the numerical predictions are in good agreement. Processes of heat transfer are analyzed from the flow behavior and the underlying mechanisms. The maximum local heat transfer between the cavity walls and the flow occurs at Lf = 6 corresponding to the length of the potential core. Nusselt number at the stagnation point is correlated versus Reynolds number Re and impinging distance Lf; [Nu0=f(Re,Lf)].

A New Heat Transfer Correlation for Turbulent Flow of Air With Variable Properties in Noncircular Ducts

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Peng Wang ◽  
Mo Yang ◽  
Zhiyun Wang ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Circular Tube ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Variable Properties ◽  
Corner Region

Turbulent flow and heat transfer of air with variable properties in a set of regular polygonal ducts and circular tube have been numerically simulated. All the ducts have the same hydraulic diameter as their characteristic lengths in the Reynolds number. The flow is modeled as three-dimensional (3D) and fully elliptic by using the finite volume method and the standard k-ε turbulence model. The results showed that the relatively strong secondary flow could be observed with variable properties fluid. For the regular polygonal ducts, the local heat transfer coefficient along circumferential direction is not uniform; there is an appreciable reduction in the corner region and the smaller the angle of the corner region, the more appreciable deterioration the corner region causes. The use of hydraulic diameter for regular polygonal ducts leads to unacceptably large errors in turbulent heat transfer determined from the circular tube correlations. Based on the simulation results, a correction factor is proposed to predict turbulent heat transfer in regular polygonal ducts.

Measurements of Turbulent Heat Transfer on the Leading and Trailing Surfaces of a Square Duct Rotating About an Orthogonal Axis

1988 ◽  
Author(s):  
W. D. Morris ◽  
S. P. Harasgama ◽  
R. Salemi
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Rotor ◽  
Secondary Flows ◽  
Rotor Blades ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Orthogonal Axis ◽  
Square Duct

This paper presents the results of an experimental investigation of local heat transfer on the trailing and leading surfaces of a square-sectioned duct rotating about an axis orthogonal to its central axis. The flow geometry has application to the cooling of gas turbine rotor blades. It is demonstrated that Coriolis induced secondary flows enhance local heat transfer over the trailing surface in relation to the corresponding non rotating case. Little effect of rotation on the leading surface was detected over the range of experiments covered to date. Rotational buoyancy is shown to have a slight effect only at the lowest Reynolds number tested. The conditions under which buoyancy may be neglected in the real engine range of parameters is still uncertain. Simple correlations for the present data are given as design aids.

Numerical Study of a New Heat Transfer Correlation for Turbulent Air Flow in Noncircular Ducts With Variable Properties

2013 ◽  
Author(s):  
Mo Yang ◽  
Peng Wang ◽  
Yuwen Zhang ◽  
Zhiyun Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Circular Tube ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Variable Properties

Turbulent flow of air with variable properties in a set of regular polygonal ducts and circular tube have been numerically simulated. All the ducts have the same hydraulic diameter as their characteristic length dimension in the Reynolds number. The flow is modeled as three-dimensional and fully elliptic by using the finite volume method and the standard k-ε turbulence model is adopted. The performances of the flow and heat transfer have been thoroughly investigated. The results showed that comparatively strong secondary flow can be observed with variable properties fluid. For the regular polygonal duct, the local heat transfer coefficient along circumferential direction is not uniform and there is an appreciable reduction in the corner region. The use of hydraulic diameter for regular polygonal ducts to determine turbulent flow heat transfer from circular tube correlations leads to unacceptably large errors. Based on the simulation results, a correction factor Cϕ is proposed to ameliorate the previous correlations, and the error in the prediction of turbulent heat transfer with the new correlation is within 6%.

Experimental and Numerical Study of Turbulent Heat Transfer in Twisted Square Ducts

2001 ◽  
Vol 123 (5) ◽  
pp. 868-877 ◽  
Author(s):  
Liang-Bi Wang ◽  
Wen-Quan Tao ◽  
Qiu-Wang Wang ◽  
Ya-Ling He
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Uniform Heat Flux ◽  
Turbulent Heat ◽  
Square Duct ◽  
Square Ducts

This paper describes the experimental and numerical study of three mildly twisted square ducts (twisted uniform cross section square duct, twisted divergent square duct and twisted convergent square duct). Experiments are conducted for air with uniform heat flux condition. Measurements are also conducted for a straight untwisted square duct for comparison purpose. Numerical simulations are performed for three-dimensional and fully elliptic flow and heat transfer by using a body-fitted finite volume method and standard k−ε turbulence model. Both experimental and numerical results show that the twisting brings about a special variation pattern of the spanwise distribution of the local heat transfer coefficient, while the divergent and convergent shapes lead to different axial local heat transfer distributions. Based on the test data, the thermal performance comparisons are made under three constraints (identical mass flow rate, identical pumping power and identical pressure drop) with straight untwisted square duct as a reference. Comparisons show that the twisted divergent duct can always enhance heat transfer, the twisted convergent duct always deteriorates heat transfer, and the twisted constant cross section duct is somewhat in between.

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