Effect of the Number of Periodic Module on Flow and Heat Transfer in a Periodic Array of Cubic Pin-Fins Inside a Channel

2008 ◽  
Vol 15 (3) ◽  
pp. 243-260 ◽  
Author(s):  
Arun K. Saha
Keyword(s):  
Heat Transfer ◽  
Periodic Array ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Periodic Module

Unsteady RANS Simulation of Turbulent Flow and Heat Transfer in a Channel With Periodic Array of Cubic Pin-Fins

2003 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Channel Wall ◽  
Numerical Study ◽  
Periodic Array ◽  
Outer Flow ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Unsteady Rans

An unsteady three-dimensional numerical study is performed to explore flow and heat transfer in a periodic array of cubic pin-fins housed inside a narrow channel. Short cubic pin-fins are arranged in an inline pattern with both streamwise and transverse periodicity set to 2.5 times the pin-fin dimension. Calculations are done in the turbulent flow regime for Reynolds numbers in the range of 7090–13280. The unsteady Reynolds-Averaged Navier Stokes (RANS) and energy equations are solved using higher order temporal and spatial discretization schemes. An unsteady k-ε turbulence model is employed to model the unresolved turbulence fluctuations. The unsteady RANS results are able to resolve discrete large scale spatial and temporal fluctuations in the flow. These fluctuations appear to mostly influence the flow in the region between the cubic fins, but are linked to low amplitude oscillations in the outer flow. Three thermal boundary conditions are studied: (1) only channel wall heated (2) only pin-fins heated and (3) both channel wall and pin-fins heated. The overall heat transfer enhancement is about 1.8–2.0 times the heat transfer from a smooth duct flow. The heat transfer from pin-fins is found to be 5–9% higher than that from the top wall at low Reynolds number (7090 and 8900), while it is of comparable magnitude at higher Reynolds number (=13280).

Computation of Flow and Heat Transfer in Rotating Rectangular Channels (AR=4:1) With Pin-Fins by a Reynolds Stress Turbulence Model

2006 ◽  
Vol 129 (6) ◽  
pp. 685-696 ◽  
Author(s):  
Guoguang Su ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotation Number ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Pin Fins

Computations with multi-block chimera grids were performed to study the three-dimensional turbulent flow and heat transfer in a rotating rectangular channel with staggered arrays of pin-fins. The channel aspect ratio (AR) is 4:1, the pin length to diameter ratio (H∕D) is 2.0, and the pin spacing to diameter ratio is 2.0 in both the stream-wise (S1∕D) and span-wise (S2∕D) directions. A total of six calculations have been performed with various combinations of rotation number, Reynolds number, and coolant-to-wall density ratio. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.20, respectively, while the Reynolds number varied from 10,000 to 100,000. For the rotating cases, the rectangular channel was oriented at 150deg with respect to the plane of rotation to be consistent with the configuration of the gas turbine blade. A Reynolds-averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure for detailed predictions of mean velocity, mean temperature, and heat transfer coefficient distributions.

Steady RANS of Flow and Heat Transfer in a Smooth and Pin-Finned U-Duct With a Trapezoidal Cross Section

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Kenny S.-Y. Hu ◽  
Xingkai Chi ◽  
Tom I.-P. Shih ◽  
Minking Chyu ◽  
Michael Crawford
Keyword(s):  
Heat Transfer ◽  
Relative Error ◽  
Turbulence Models ◽  
Separated Flow ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Maximum Relative Error ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Turn Region

Steady Reynolds-averaged Navier--Stokes (RANS) simulations were performed to examine the ability of four turbulence models—realizable k–ε (k–ε), shear-stress transport (SST), Reynolds stress model with linear pressure strain (RSM-LPS), and stress-omega RSM (RSM-τω)—to predict the turbulent flow and heat transfer in a trapezoidal U-duct with and without a staggered array of pin fins. Results generated for the heat-transfer coefficient (HTC) were compared with experimental measurements. For the smooth U-duct, the maximum relative error in the averaged HTC in the up-leg is 2.5% for k–ε, SST, and RSM-τω and 9% for RSM-LPS. In the turn region, the maximum is 50% for k–ε and RSM-LPS, 14.5% for RSM-τω, and 29% for SST. In the down-leg, SST gave the best predictions and RSM-τω being a close second with maximum relative error less than 10%. The ability to predict the separated flow downstream of the turn dominated the performance of the models. For the U-duct with pin fins, SST and RSM-τω predicted the best, and k–ε predicted the least accurate HTCs. For k–ε, the maximum relative error is about 25%, whereas it is 15% for the SST and RSM-τω, and they occur in the turn. In the turn region, the staggered array of pin fins was found to behave like guide vanes in turning the flow. The pin fins also reduced the size of the separated region just after the turn.

Effects of Pin-Fin Height on Flow and Heat Transfer in a Rectangular Duct

2011 ◽  
Author(s):  
X. Chi ◽  
T. I.-P. Shih ◽  
K. M. Bryden ◽  
S. Siw ◽  
M. K. Chyu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Wall Region ◽  
Rectangular Duct ◽  
Opposite Wall ◽  
Pin Fin ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Inlet Conditions ◽  
D Values

CFD simulations were performed to study the flow and heat transfer in a rectangular duct (Wd × Hd, where Wd/Hd = 3) with a staggered array of circular pin fins (D = Hd/4) mounted on the two opposite walls separated by Hd. For this array of pin fins, five different pin-fin height (H) combinations were examined, and they are (1) H = Hd = 4D (i.e., all pin fins extended from wall to wall), (2) H = 3D on both walls, (3) H = 2D on both walls, (4) H = 4D on one wall and H = 2D on the opposite wall, and (5) H = 3D on one wall and H = 2D on the opposite wall. The H values studied give H/D values of 2, 3, and 4 and C/D values of 2, 1, and 0, where C is the distance between the pin-fin tip and the opposite wall. For all cases, the duct wall and pin-fin surface temperatures were maintained at Tw = 313.15 K; the temperature and the speed of the air at the duct inlet were uniform at Tinlet = 343.15 K and U = 8.24 m/s; the pressure at the duct exit was fixed at Pb = 1 atm; and the Reynolds number based on the duct hydraulic diameter and duct inlet conditions was Re = 15,000. This CFD study is based on 3-D steady RANS, where the ensemble averaged continuity, compressible Navier-Stokes, and energy equations are closed by the thermally perfect equation of state and the two-equation realizable k-ε turbulence model with wall functions and with the low-Reynolds number model of Chen and Patel in the near-wall region. The usefulness of this CFD study was assessed by comparing predicted heat-transfer coefficient and friction factor with available experimental data. Results are presented to show how the flow induced by arrays of pin fins of different heights affects temperature distribution, surface heat transfer, and pressure loss.

Steady RANS of Flow and Heat Transfer in a Smooth and Pin-Finned U-Duct With a Trapezoidal Cross Section

2018 ◽  
Author(s):  
Kenny S.-Y. Hu ◽  
Xingkai Chi ◽  
Tom I-P. Shih ◽  
Minking Chyu ◽  
Michael Crawford
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Relative Error ◽  
Turbulence Models ◽  
Separated Flow ◽  
Maximum Relative Error ◽  
Trapezoidal Cross Section ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Turn Region

Steady RANS were performed to examine the ability of four turbulence models — realizable k-ε (k-ε), shear-stress transport (SST), Reynolds stress model with linear pressure strain (RSM-LPS), and stress-omega RSAM (RSM-τω) — to predict the turbulent flow and heat transfer in a U-duct with a trapezoidal cross section and with and without a staggered array of pin fins. Results generated for the heat-transfer coefficient (HTC) were compared with experimentally measured values. For the smooth U-duct, the maximum relative error in the averaged HTC in the up-leg is 2.5% for k-ε, SST, and RSM-τω and 9% for RSM-LPS. In the turn region, that maximum is 14.5% for RSM-τω, 29% for SST, and 50% for k-ε and RSM-LPS. In the down-leg, SST gave the best predictions and RSM-τω being a close second with maximum relative error less than 10%. The ability to predict the secondary flow in the turn region and the separated flow downstream of the turn dominated in how well the models predict the HTC. For the U-duct with pin fins, k-ε predicted the lowest and the least accurate HTCs, and SST and RSM-τω predicted the best. For k-ε, the maximum relative error in the averaged HTC is about 25%, whereas it is 15% for the SST and RSM-τω, and they occur in the turn. In the turn region, the staggered array of pin fins was found to behave like guide vanes in turning the flow. The pin fins also reduced the size of the separated region just after the turn.

Numerical Investigation on the Flow and Heat Transfer Characteristics of the Superheated Steam in the Wedge Duct With Pin-Fins

2013 ◽  
Author(s):  
Gaoliang Liao ◽  
Xinjun Wang ◽  
Xiaowei Bai ◽  
Ding Zhu ◽  
Jinling Yao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Three Dimensional ◽  
Heat Transfer Characteristics ◽  
Pin Fin ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Steam Superheat

By using the CFX software, the three-dimensional flow and heat transfer characteristics in the cooling duct with pin-fin in the blade trailing edge were numerically simulated. The effects of pin-fin arrangements, Reynolds number, steam superheat degrees, streamwise pin density and convergence angle of the wedge duct on the flow and heat transfer characteristics were analysed. The results show that the Nusselt number on the endwall and pin-fin surfaces as well as the pin-fin row averaged Nusselt number increase with the increasing of Reynolds number, while it decreased with the with the increasing of X/D. The pressure drop increases with the increasing of Reynolds number while decreases with the increasing of X/D in the wedge duct. The degree of superheat has little effect on the pressure loss in the wedge duct. A comprehensive analysis and comparison show that the highest thermal performance is reached in the wedge duct when the value of X/D is 1.5.

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