A Numerical Study of the Convective Heat Transfer in Low-Reynolds Number Turbulent Flows in Corrugated Pipes

2012 ◽  
Author(s):  
Ramin K. Rahmani ◽  
J. Eric Arnold ◽  
George W. Kraus
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Turbulent Flows ◽  
Convective Heat ◽  
Numerical Study ◽  
Internal Flow ◽  
Eddy Simulation ◽  
Corrugated Surfaces ◽  
The Impact

Enhancement of convective heat transfer in internal turbulent flows with low-to-moderate Re number has been the subject of numerous studies, due to its vast applications. Corrugated surfaces can be used as enhancement devices in the heat convection systems. An ideal corrugation, for heat transfer in internal flow applications, provides a higher heat transfer rate with minimized pressure drop. The ratio of heat flux to the pressure drop can be used to determine the efficiency of a design. Using Large-Eddy Simulation, the heat transfer in low-Re turbulent flow in a pipe is studied to investigate the impact of different corrugated profiles with similar hydraulic diameter.

Effect of a Pair of Horizontal Frame Members on the Convective Heat Transfer With Laminar and Turbulent Flow From a Recessed Window to a Room

2011 ◽  
Author(s):  
Patrick H. Oosthuizen ◽  
David Naylor
Keyword(s):  
Heat Transfer ◽  
Prandtl Number ◽  
Convective Heat Transfer ◽  
Turbulent Flows ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Numerical Study ◽  
Wall Functions ◽  
Inner Surface

The horizontal frame members that often protrude from the inner surface of a window can significantly effect the convective heat transfer rate from this inner surface to the room. The purpose of the present numerical study was to determine how the size of a pair of horizontal frame members effect this heat transfer rate. The flow has been assumed to be steady and conditions under which laminar, transitional, and turbulent flows occur are considered. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being dealt with using the Boussinesq approach. The governing equations have been solved using the FLUENT commercial CFD code. The k-epsilon turbulence model with standard wall functions and with buoyancy force effects fully accounted for has been used. The solution has the following parameters: the Rayleigh number, the Prandtl number, the dimensionless window recess depth, and the dimensionless width and depth of the frame members. Results have been obtained for a Prandtl number of 0.74.

Influence of Various Nanofluid Types on Wavy Microchannels Heat Sink Cooling Performance

2013 ◽  
Vol 420 ◽  
pp. 118-122 ◽  
Author(s):  
Prem Gunnasegaran ◽  
Noel Narindra ◽  
Norshah Hafeez Shuaib
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Sink ◽  
Convective Heat Transfer Coefficient ◽  
Volume Fractions ◽  
The Impact

This paper discusses the impact of using various types of nanofluids and nanoparticle volume fractions on heat transfer and fluid flow characteristics in a wavy microchannel heat sink (WMCHS) with rectangular cross-section. Numerical investigations using three different types of nanofluids including Al2O3-H2O, CuO-H2O, and diamond-H2O with a fixed nanoparticle volume fraction of 3% and using a diamond-H2O with nanoparticle volume fractions ranging from 0.5% to 5% are examined. This investigation covers Reynolds numbers in the range of 100 to 1000. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using the finite-volume method (FVM). The computational model is used to study the variations of convective heat transfer coefficient, pressure drop and wall shear stress. It is inferred that the convective heat transfer coefficient of a WMCHS cooled with the nanofluid flow showed marked improvement over the pure water with a smaller pressure drop penalty.

Enhancement of Temperature Blending in Convective Heat Transfer by Motionless Inserts With Variable Segment Length

2010 ◽  
Vol 2 (3) ◽  
Author(s):  
Ramin K. Rahmani ◽  
Anahita Ayasoufi ◽  
Emad Y. Tanbour ◽  
Hosein Molavi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Convective Heat Transfer ◽  
Turbulent Flows ◽  
Convective Heat ◽  
Segment Length ◽  
Width Ratio ◽  
Enhance Heat Transfer ◽  
Variable Segment ◽  
The Impact

Stationary spiral inserts can effectively enhance heat transfer and temperature blending in the heat convection systems. In this paper, the impact of the segment length on the performance of a stationary insert is studied for flow Re numbers from ∼80 to ∼7900 through numerical simulation of heat transfer in streams of cold and hot gases flowing across it. The segment length to width ratio is from 1.11 to 2.33. The temperature of the studied gas is from 300 K to 1300 K. It is shown that the insert with variable segment length is more effective in temperature blending for two compressible streams compared with an insert with constant segment length, especially for low-Re-number turbulent flows.

scholarly journals Numerical Study of Turbulent Flows and Convective Heat Transfer of Al2O3-Water Nanofluids In A Circular Tube

2020 ◽  
Vol 77 (2) ◽  
pp. 1-12
Author(s):  
Abdelkader Mahammedi ◽  
Houari Ameur ◽  
Younes Menni ◽  
Driss Meddah Medjahed
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Turbulent Flows ◽  
Convective Heat ◽  
Circular Tube ◽  
Numerical Study ◽  
Constant Heat Flux ◽  
Flux Boundary Condition ◽  
Pressure Losses

The convective heat transfer of Al2O3-water nanofluids through a circular tube with a constant heat flux boundary condition is studied numerically. Turbulent flow conditions are considered with a Reynolds number ranging from 3500 to 20000. The numerical method used is based on the single-phase model. Four volume concentrations of Al2O3-water nanoparticles (0.1, 0.5, 1, and 2%) are used with a diameter of nanoparticle of 40 nm. A considerable increase in Nusselt number, axial velocity, and turbulent kinetic energy was found with increasing Reynolds number and volume fractions. However, the pressure losses were also increased with the raise of Re and nanoparticles concentration.

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