Turbulent Heat Transfer Downstream of a Contraction-Related, Forward-Facing Step in a Duct

1987 ◽  
Vol 109 (3) ◽  
pp. 621-626 ◽  
Author(s):  
A. Garcia ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Sherwood Number ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Axial Distribution ◽  
Contraction Ratio ◽  
Abrupt Contraction ◽  
Forward Facing Step ◽  
The Heat Transfer Coefficient

Experiments were performed to investigate the axial distribution of the heat transfer coefficient downstream of an abrupt contraction in a flat rectangular duct. The contraction was created by the presence of a forward-facing step in one of the walls of the duct. The flow arriving at the step was hydrodynamically developed and isothermal. In the contracted duct, the duct wall that constituted the continuation of the step was maintained at a uniform temperature different from that of the entering flow, while the other walls were adiabatic. During the course of the experiments, the Reynolds number of the flow in the contracted duct ranged from 4000 to 24,000, while the ratio of the post-contraction to the precontraction duct heights took on values of 1 (no contraction), 0.8, 0.6, and 0.4. In the presence of the contraction, the axial distribution of the Sherwood number increased at first, attained a maximum, and then decreased monotonically to a fully developed value. In contrast, the no-contraction Sherwood number decreased monotonically and subsequently became fully developed. At a given Reynolds number, the peak Sherwood number for the contraction case was virtually independent of the contraction ratio and exceeded the largest measured Sherwood number for the no-contraction case by about a factor of two.

Numerical Study of Turbulent Heat Transfer in Annular Pipe with Sudden Contraction

2013 ◽  
Vol 465-466 ◽  
pp. 461-466 ◽  
Author(s):  
Hussein Togun ◽  
Tuqa Abdulrazzaq ◽  
S.N. Kazi ◽  
A. Badarudin ◽  
Mohd Khairol Anuar Ariffin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbulent Heat Transfer ◽  
Recirculation Region ◽  
Turbulent Heat ◽  
Contraction Ratio ◽  
Sudden Contraction ◽  
Annular Pipe

Turbulent heat transfer to air flow in annular pipe with sudden contraction numerically studied in this paper. The k-ε model with finite volume method used to solve continuity, moment and energy equations. The boundary condition represented by uniform and constant heat flux on inner pipe with range of Reynolds number varied from 7500 to 30,000 and contraction ratio (CR) varied from 1.2 to 2. The numerical result shows increase in local heat transfer coefficient with increase of contraction ratio (CR) and Reynolds number. The maximum of heat transfer coefficient observed at contraction ratio of 2 and Reynolds number of 30,000 in compared with other cases. Also pressure drop coefficient noticed rises with increase contraction ratio due to increase of recirculation flow before and after the step height. In contour of velocity stream line can be seen that increase of recirculation region with increase contraction ratio (CR).

Heat Transfer Downstream of a Fluid Withdrawal Branch in a Tube

1979 ◽  
Vol 101 (1) ◽  
pp. 23-28 ◽  
Author(s):  
E. M. Sparrow ◽  
R. G. Kemink
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Test Section ◽  
Turbulent Pipe Flow ◽  
Turbulent Heat Transfer ◽  
Working Fluid ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Axial Distribution ◽  
Thermal Entrance

Experiments have been performed to study how fluid withdrawal at a branch point in a tube affects the turbulent heat transfer characteristics of the main line flow downstream of the branch. Air was the working fluid. The experiments were carried out for several fixed test section Reynolds numbers and at each Reynolds number the ratio of the withdrawn flow to the test section flow (hereafter designated as the flow split number) was varied systematically. Local heat transfer coefficients were determined both around circumference and along the length of the tube, and circumferential average coefficients were also evaluated. The circumferential average Nusselt numbers in the thermal entrance region are much higher than those for a conventional turbulent pipe flow having the same Reynolds number, and the differences are accentuated at higher values of the flow split number. When normalized by the corresponding fully developed value, the axial distribution of the circumferential average Nusselt number is relatively insensitive to the Reynolds number for a fixed flow split. The thermal entrance lengths, based on a five percent approach to fully developed conditions, are in the 20 to 30 diameter range, which is substantially greater than that for conventional turbulent air flows. Circumferential variations on the order of ±20 percent are induced by the fluid withdrawal process. For the most part, these variations are dissipated upstream of x/D = 10.

An Experimental Study of Turbulent Heat Transfer in Converging Rectangular Ducts

1973 ◽  
Vol 95 (4) ◽  
pp. 453-457 ◽  
Author(s):  
J. W. Yang ◽  
Nansen Liao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Taper Angle ◽  
Number Range ◽  
Pressure Distributions ◽  
Side Walls ◽  
The Heat Transfer Coefficient ◽  
Local Reynolds Number

The turbulent heat transfer rate, wall temperature, and pressure distributions in the hydrodynamically and thermally developing region of rectangular converging ducts of taper angle 0, 2-1/2, 5, and 7-1/2 deg have been determined experimentally. The heating condition is such that the top and bottom walls are uniformly heated while the two side walls are unheated. The fluid is air and the experiments cover the Reynolds number range from 2.4 × 104 to 4.8 × 104. The results show that the heat transfer coefficient is increased by the increasing of either the taper angle or the inlet Reynolds number. An empirical correlation between the local Nusselt number and the local Reynolds number was determined.

Investigation of MHD RANS Modeling Base on DNS Database Under the Advanced Blanket Design Conditions Utilized Molten Salt

2014 ◽  
Author(s):  
Naoki Osawa ◽  
Yoshinobu Yamamoto ◽  
Tomoaki Kunugi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Turbulent Channel Flow ◽  
Turbulent Heat Transfer ◽  
Navier Stokes ◽  
Turbulent Heat ◽  
Mhd Turbulence ◽  
Rans Modeling ◽  
Heat Transfer Degradation

In this study, validations of Reynolds Averaged Navier-Stokes Simulation (RANS) based on Kenjeres & Hanjalic MHD turbulence model (Int. J. Heat & Fluid Flow, 21, 2000) coupled with the low-Reynolds number k-epsilon model have been conducted with the usage of Direct Numerical Simulation (DNS) database. DNS database of turbulent channel flow imposed wall-normal magnetic field on, are established in condition of bulk Reynolds number 40000, Hartmann number 24, and Prandtl number 5. As the results, the Nagano & Shimada model (Trans. JSME series B. 59, 1993) coupled with Kenjeres & Hanjalic MHD turbulence model has the better availability compared with Myong & Kasagi model (Int. Fluid Eng, 109, 1990) in estimation of the heat transfer degradation in MHD turbulent heat transfer.

Turbulent Heat Transfer Computations for Rearward-Facing Steps and Sudden Pipe Expansions

1985 ◽  
Vol 107 (1) ◽  
pp. 70-76 ◽  
Author(s):  
A. M. Gooray ◽  
C. B. Watkins ◽  
Win Aung
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Dynamic ◽  
Turbulence Models ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Streamline Curvature ◽  
Recirculating Flow ◽  
Moderate Reynolds Number ◽  
Entire Flow

Results of numerical calculations for heat transfer in turbulent recirculating flow over two-dimensional, rearward-facing steps and sudden pipe expansions are presented. The turbulence models used in the calculation are the standard k – ε model and the low-Reynolds number version of this model. The k – ε models have been improved to account for the effects of streamline curvature and pressure-strain (scalar) interactions including wall damping. A sequence of two computational passes is performed to obtain optimal results over the entire flow field. The presented results consist of computed distributions of heat transfer coefficents for several Reynolds numbers, emphasizing the low-to-moderate Reynolds number regime. The heat transfer results also include correlations of Nusselt numnber for both side and bottom walls. The computed heat transfer results and typical computed fluid dynamic results are compared with available experimental data.

scholarly journals Computation of Turbulent Heat Transfer on the Walls of a 180 Degree Turn Channel With a Low Reynolds Number Reynolds Stress Model

2002 ◽  
Author(s):  
D. L. Rigby ◽  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Reynolds Stress ◽  
Low Reynolds Number ◽  
Reynolds Stress Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Stress Model ◽  
Generalized Gradient ◽  
Low Reynolds

The Low Reynolds number version of the Stress-ω model and the two equation k-ω model of Wilcox were used for the calculation of turbulent heat transfer in a 180 degree turn simulating an internal coolant passage. The Stress-ω model was chosen for its robustness. The turbulent thermal fluxes were calculated by modifying and using the Generalized Gradient Diffusion Hypothesis. The results showed that using this Reynolds Stress model allowed better prediction of heat transfer compared to the k-ω two equation model. This improvement however required a finer grid and commensurately more CPU time.

Large Eddy Simulation of Turbulent Heat Transfer Around a Circular Cylinder in Crossflow

2007 ◽  
Author(s):  
Sung-Eun Kim ◽  
Hajime Nakamura
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Large Eddy Simulation ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Heat Transfer Characteristics ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Large eddy simulation has been carried out of turbulent flow and heat transfer around a circular cylinder in crossflow at three subcritical Reynolds numbers (Re = 3,900, 10,000, 18,900) where the flow and heat transfer characteristics change rapidly with the Reynolds number. The computations were carried out using a second-order-accurate finite-volume Navier-Stokes solver that permits use of arbitrary unstructured meshes. A fully implicit, non-iterative fractional-step method was employed to advance the solution in time. The subgrid-scale (SGS) turbulent stresses and heat fluxes were modeled using the dynamic Smagorinsky model. The LES predictions were found to be in good agreement with the experimental data of Hajime and Igarashi (2004). The salient features of turbulent heat transfer in subcritical regime such as the laminar thermal boundary layer and the rapid increase with Reynolds number both in the mean and the r.m.s. Nusselt number in the separated region are closely reproduced by the predictions. The numerical results confirmed that the heat transfer characteristics are closely correlated with the structural change in the underlying flow with the Reynolds number.

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