A NEW HEAT EDDY DIFFUSIVITY EQUATION FOR CALCULATION OF HEAT TRANSFER TO DRAG REDUCING TURBULENT PIPE FLOWS

1986 ◽  
Author(s):  
H. K. Yoon ◽  
Afshin J. Ghajar
Keyword(s):  
Heat Transfer ◽  
Eddy Diffusivity ◽  
Pipe Flows ◽  
Diffusivity Equation

Numerical Study of Convective Heat Transfer From Expanding Annular Pipe Flows

2016 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Prandtl Number ◽  
Convective Heat Transfer ◽  
Diameter Ratio ◽  
Wall Heat Transfer ◽  
Reattachment Point ◽  
Transfer Rates ◽  
Pipe Flows ◽  
Annular Pipe

Convective heat transfer from suddenly expanding annular pipe flows are numerically investigated within the steady laminar flow regime. A parametric study is performed to reveal the influence of the annular diameter ratio, k, the Prandtl number, Pr, and the Reynolds number, Re, over the following range of parameters: k = {0, 0.5, 0.7}, Pr = {0.7, 1, 7, 100}, and Re = {25, 50, 100}. Heat transfer enhancement downstream of the expansion plane is only observed for Pr > 1. Peak wall-heat-transfer-rates always appear downstream of the flow reattachment point, in the case of suddenly expanding round pipe flows, i.e. k = 0. However, for suddenly expanding annular pipe flows, i.e., k = 0.5 and 0.7, peak wall-heat-transfer-rates always appear upstream of the flow reattachment point. The observed heat transfer augmentation is more dramatic for suddenly expanding annular flows, in comparison with the one observed for suddenly expanding pipe flows. For a given annular diameter ratio and Reynolds number, increasing the Prandtl number, always results in higher wall-heat-transfer-rates downstream the expansion plane.

Heat Transfer in a Supersonic Parallel Diffuser

1965 ◽  
Vol 7 (1) ◽  
pp. 1-7 ◽  
Author(s):  
P. J. Baker
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Cross Section ◽  
Static Pressure ◽  
Positive Pressure ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Flows ◽  
Pressure Distributions ◽  
The Mean

This paper presents the results of heat transfer measurements taken on a two-dimensional supersonic parallel diffuser. The wall static pressure distributions and the corresponding heat transfer coefficients and fluxes have been measured for a range of initial total pressures. The effects of varying the area of the diffuser cross-section for the same upstream generating nozzle have also been studied. Mach number profiles measured at sections along the diffuser show that in the presence of shock waves and a positive pressure gradient the flow is very much underdeveloped. In general, the mean level of heat transfer is found to be much greater than that predicted by conventional empirical equations for subsonic pipe flows with zero pressure gradient. Further, on comparison between normal and oblique shock diffusion the former is found to give the higher level of heat transfer.

Developing Turbulent Flow and Heat Transfer in Concentric Annuli

1972 ◽  
Vol 1 (1) ◽  
pp. 13-24
Author(s):  
Y. Lee ◽  
S.D. Park
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Thermal Conditions ◽  
Eddy Diffusivity ◽  
Gas Flows ◽  
Local Flow ◽  
Number Range ◽  
Starting Position ◽  
Eddy Diffusivities ◽  
Flow And Heat Transfer

The problem of the simultaneously developing turbulent flow and heat transfer in concentric annuli was studied from an integral viewpoint, based on a modified model for the eddy diffusivity of momentum together with a new ratio of eddy diffusivities obtained from experiment. Solutions were obtained for one surface uniformly heated and the other insulated. The analytical results were then compared with the measurement of local flow and thermal conditions for air flow through four concentric annuli for a Reynolds number range of about 20,000 to 110,000. The analysis assumed the flow was turbulent everywhere. In the experimental work the flow was tripped at the starting position of both the velocity and thermal boundary layers. Air was chosen in the experiment as it represents gas flows in general.

Improved Modeling of Turbulent Forced Convective Heat Transfer in Straight Ducts

1999 ◽  
Vol 121 (3) ◽  
pp. 712-719 ◽  
Author(s):  
M. Rokni ◽  
B. Sunden
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Low Reynolds Number ◽  
Eddy Diffusivity ◽  
Numerical Approach ◽  
Generalized Gradient ◽  
Forced Convective Heat Transfer ◽  
Low Reynolds

This investigation concerns numerical calculation of turbulent forced convective heat transfer and fluid flow in their fully developed state at low Reynolds number. The authors have developed a low Reynolds number version of the nonlinear k-ε model combined with the heat flux models of simple eddy diffusivity (SED), low Reynolds number version of generalized gradient diffusion hypothesis (GGDH), and wealth ∝ earning × time (WET) in general three-dimensional geometries. The numerical approach is based on the finite volume technique with a nonstaggered grid arrangement and the SIMPLEC algorithm. Results have been obtained with the nonlinear k-ε model, combined with the Lam-Bremhorst and the Abe-Kondoh-Nagano damping functions for low Reynolds numbers.

Prediction of Local and Integral Turbulent Transport Properties for Liquid-Metal Heat Transfer in Equilateral Triangular Rod Arrays

1975 ◽  
Vol 97 (2) ◽  
pp. 238-243 ◽  
Author(s):  
H. Ramm ◽  
K. Johannsen
Keyword(s):  
Heat Transfer ◽  
Liquid Metal ◽  
Transport Properties ◽  
Turbulence Model ◽  
Transfer Problem ◽  
Turbulent Transport ◽  
Three Dimensional ◽  
Theoretical Method ◽  
Eddy Diffusivity ◽  
Thermal Mixing

A theoretical method based on a phenomenological turbulence model has been applied to evaluate turbulent transport properties for liquid-metal heat transfer in bare equilateral triangular rod bundles. Results obtained for local distributions of thermal eddy diffusivity in the various directions are presented in terms of correlations. From a subsequent solution of the three-dimensional heat transfer problem between two characteristic interior subchannels under conditions characteristic for tracer-type mixing experiments, integral thermal mixing coefficients and thermal length scales have been evaluated. Results demonstrate that the basic concept of subchannel analysis treating molecular conduction and turbulent transport independently of each other tends to underestimate intersubchannel transport. The uncertainties which are involved in principal assumptions of the turbulence-model as well as in the available empirical results are discussed in some detail.

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