Experimental Study on Convective Heat Transfer for Turbulent Flow in a Square Duct With a Ribbed Rough Wall (Characteristics of Mean Temperature Field)

1994 ◽  
Vol 116 (2) ◽  
pp. 332-340 ◽  
Author(s):  
M. Hirota ◽  
H. Fujita ◽  
H. Yokosawa
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Turbulent Flow ◽  
Cross Section ◽  
Rough Wall ◽  
Turbulent Shear ◽  
Turbulent Heat ◽  
Square Duct ◽  
Mean Temperature ◽  
The Mean

This paper presents experimental results concerning a time-mean temperature field obtained in forced convection heat transfer for a turbulent flow through a square duct with a ribbed rough bottom wall. The secondary flow pattern in the duct is reflected in the distribution of the local Nusselt number, the values of which on the smooth walls of the rough duct are 1.71~1.97 times those of the smooth duct. In the upper half cross section near the upper smooth wall opposite the bottom ribbed rough wall, the profile of the mean temperature distribution is similar to that of the primary flow velocity distribution, and the validity of the temperature inner law was confirmed. However, in the lower half cross section near the bottom ribbed rough wall, the dissimilarity between the mean velocity and the mean temperature fields becomes pronounced, and the inner law is not valid for mean temperature distributions. The mechanism of the heat transfer near the ribbed rough wall was examined based on the transport equations of turbulent shear stress and turbulent heat flux.

Heat Transfer Scaling Close to the Wall for Turbulent Channel Flows

2013 ◽  
Vol 65 (3) ◽  
Author(s):  
Chiranth Srinivasan ◽  
Dimitrios V. Papavassiliou
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Turbulent Flow ◽  
Turbulent Heat Flux ◽  
Turbulent Heat Transfer ◽  
Wall Region ◽  
Turbulent Heat ◽  
Mean Temperature ◽  
Scaling Parameters ◽  
The Mean

This work serves a two-fold purpose of briefly reviewing the currently existing literature on the scaling of thermal turbulent fields and, in addition, proposing a new scaling framework and testing its applicability. An extensive set of turbulent scalar transport data for turbulent flow in infinitely long channels is obtained using a Lagrangian scalar tracking approach combined with direct numerical simulation of turbulent flow. Two cases of Poiseuille channel flow, with friction Reynolds numbers 150 and 300, and different types of fluids with Prandtl number ranging from 0.7 to 50,000 are studied. Based on analysis of this database, it is argued that the value and the location of the maximum normal turbulent heat flux are important scaling parameters in turbulent heat transfer. Implementing such scaling on the mean temperature profile for different fluids and Reynolds number cases shows a collapse of the mean temperature profiles onto a single universal profile in the near wall region of the channel. In addition, the profiles of normal turbulent heat flux and the root mean square of the temperature fluctuations appear to collapse on one profile, respectively. The maximum normal turbulent heat flux is thus established as a turbulence thermal scaling parameter for both mean and fluctuating temperature statistics.

STEADY STATE HEAT TRANSFER TO FULLY DEVELOPED TURBULENT FLOW IN A CURVED CHANNEL

1957 ◽  
Vol 35 (4) ◽  
pp. 410-434
Author(s):  
A. W. Marris
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Flow ◽  
Curved Channel ◽  
Mean Velocity ◽  
Fully Developed Turbulent Flow ◽  
Angular Velocities ◽  
The Mean

A vorticity transfer analogy theory of turbulent heat transfer is developed first for the case of fully developed turbulent flow under zero transverse pressure and temperature gradients such as that in the annulus between concentric cylinders rotating with different angular velocities or in a "free vortex". The mean flow is assumed to be two-dimensional. The theory, which requires that the turbulence be statistically isotropic, yields a temperature distribution in agreement with experiment except in narrow regions immediately adjacent to the boundaries. An argument is given to show that the boundary layer thickness should be of the order of the reciprocal of the square root of the mean velocity, these boundaries are introduced, and Nusselt moduli are defined and their dependence on Reynolds and Prandtl numbers is investigated.The temperature distributions for the case of non-zero transverse temperature and pressure gradients, i.e. for the case of flow in a curved channel in which the fluid does not flow back into itself, are then obtained and the applicability of the simpler equations for zero transverse gradients to this case is investigated.

Large Eddy Simulation in a Duct With Rounded Skewed Ribs

2005 ◽  
Author(s):  
Aroon K. Viswanathan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Cross Section ◽  
Mean Flow ◽  
Cross Sectional ◽  
Square Duct ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
Experimental Values

Results from Large Eddy Simulation (LES) of fully developed flow in a ribbed duct are presented with rib pitch-to-height ratio (P/e) is 10 and a rib height to hydraulic diameter ratio (e/Dh) is 0.1. Computations are carried out on a square duct with 45° ribs on the top and bottom walls arranged in a staggered fashion. The ribs have a rounded cross-section and are skewed at 45° to the main flow. The Reynolds number based on bulk velocity is 25,000. Mean flow and turbulent quantities, together with heat transfer and friction augmentation results are presented for a stationary case. The flow is characterized by a helical vortex behind each rib and a complementary cross-sectional secondary flow, both of which result from the angle of the rib with respect to the mean flow and result in a spanwise variation of the heat transfer. The mean flow, the turbulent quantities and the heat transfer in the duct show similar trends as in the duct with square cross-section ribs. However the results show that there is lesser friction in the ducts with rounded ribs. The overall heat transfer on the ribbed wall was augmented by 2.85 times that of a smooth duct, at the cost of friction which increases by a factor of 10. The computed values compare well with the experimental values.

Hybrid RANS-LES Simulation of Turbulent Heat Transfer in a Channel Flow With Imposed Spanwise and Streamwise Mean Temperature Gradient

2019 ◽  
Author(s):  
Olalekan O. Shobayo ◽  
D. Keith Walters
Keyword(s):  
Heat Transfer ◽  
Temperature Gradient ◽  
Channel Flow ◽  
Plane Channel ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Mean Temperature ◽  
The Mean

Abstract Computational fluid dynamics (CFD) results for turbulent flow and heat transfer in a plane channel are presented. This study presents an idealized fully-developed planar channel flow case for which the mean velocity gradient is non-zero only in the wall-normal direction, and the mean temperature gradient is imposed to be uniform and non-zero in the streamwise or spanwise direction. Previous studies have documented direct numerical simulation results for periodic channel flow with mean temperature gradient in both the streamwise and wall-normal directions, but limited investigations exist documenting the effect of imposed spanwise gradient. The objective of this study is to evaluate turbulent heat flux predictions for three different classes of modeling approach: Reynolds-averaged Navier-Stokes (RANS), large-eddy simulation (LES), and hybrid RANS-LES. Results are compared to available DNS data at Prandtl number of 0.71 and Reynolds number of 180 based on friction velocity and channel half-width. Specific models evaluated include the k-ω SST RANS model, monotonically integrated LES (MILES), improved delayed detached eddy simulation (IDDES), and dynamic hybrid RANS-LES (DHRL). The DHRL model includes both the standard formulation that has been previously documented in the literature as well as a modified version developed specifically to improve predictive capability for flows in which the primary mean velocity and mean temperature gradients are not closely aligned. The modification consists of using separate RANS-to-LES blending parameters in the momentum and energy equations. Results are interrogated to evaluate the performance of the three different model types and specifically to evaluate the performance of the new modified DHRL variant compared with the baseline version.

scholarly journals Turbulent Heat Transfer in a Square Duct with a Rough Wall.

2001 ◽  
Vol 67 (653) ◽  
pp. 154-161 ◽  
Author(s):  
Masafumi HIROTA ◽  
Gen-ichi KOARAI ◽  
Hideomi FUJITA ◽  
Shin-ichi NAKAMURA ◽  
Shuzo ITAKURA
Keyword(s):  
Heat Transfer ◽  
Rough Wall ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Square Duct

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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