Conjugate Heat Transfer Study of a Two-Dimensional Laminar Incompressible Wall Jet Over a Backward-Facing Step

2006 ◽  
Vol 129 (2) ◽  
pp. 220-231 ◽  
Author(s):  
P. Rajesh Kanna ◽  
Manab Kumar Das
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Conjugate Heat Transfer ◽  
Flow Property ◽  
Wall Jet ◽  
Two Dimensional ◽  
Interface Boundary ◽  
Backward Facing Step ◽  
Transfer Study

Steady-state conjugate heat transfer study of a slab and a fluid is carried out for a two-dimensional laminar incompressible wall jet over a backward-facing step. Unsteady stream function-vorticity formulation is used to solve the governing equation in the fluid region. An explicit expression has been derived for the conjugate interface boundary. The energy equation in the fluid, interface boundary and the conduction equation in the solid are solved simultaneously. The conjugate heat transfer characteristics, Nusselt number are studied with flow property (Re), fluid property (Pr), and solid to fluid conductivity ratio (k). Average Nusselt number is compared with that of the nonconjugate case. As k is increased, average Nusselt number is increased, asymptotically approaching the non-conjugate value.

Effect of Geometry on the Conjugate Heat Transfer of Wall Jet Flow Over a Backward-Facing Step

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
P. Rajesh Kanna ◽  
Manab Kumar Das
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Conjugate Heat Transfer ◽  
Step Length ◽  
Interface Temperature ◽  
Slab Thickness ◽  
Wall Jet ◽  
Backward Facing Step ◽  
Wall Jet Flow ◽  
Transfer Study

Conjugate heat transfer study of a backward-facing step cooled by a two-dimensional laminar incompressible wall jet has been carried out. The study is performed to find the isotherm patterns, conjugate interface temperature, local Nusselt number and average Nusselt number by varying the geometry of the solid slab. Different step length, step height, and slab thickness are considered for conjugate heat transfer study.

Numerical Simulation of Steady State Heat Transfer in a Microchannel With Obstruction

2007 ◽  
Author(s):  
Phaninder Injeti ◽  
Muhammad M. Rahman
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Nusselt Number ◽  
Average Nusselt Number ◽  
Isothermal Condition ◽  
Fabrication Process ◽  
Two Dimensional ◽  
Micro Electro Mechanical Systems ◽  
R 134A ◽  
Steady State Heat Transfer

Effects of obstructions on the heat transfer in a microtube and a two-dimensional microchannel were investigated. The obstructions normally arise during the fabrication process on the inner surface of the microtube or microchannel. Various shapes and sizes of the obstruction were considered. The shapes that were modeled were rectangular, triangular, and semicircular obstructions. Calculations were done for incompressible flow of a Newtonian fluid with developing momentum and thermal boundary layers. Equations governing the conservation of mass, momentum and energy were solved for an isothermal condition at the wall. Comparison with no obstruction case was made. It was found that for microtubes, the local Nusselt number increases significantly at the obstruction whereas the average Nusselt number for the whole tube comes out somewhat lower. For two-dimensional microchannels, both local Nusselt number at the obstruction as well as average Nusselt number for the entire tube came out to be higher. The working fluids that were investigated were water and refrigerant R-134a. The results presented in the paper demonstrates that in microchannels and microtubes that are widely used in micro electro mechanical systems (MEMS), small defects in the fabrication process may lead to large changes in local as well as global performance of the device.

Viscous Dissipation and Variable Properties Effect on Two Dimensional Conjugate Heat Transfer of Nanofluids in Microchannels

2011 ◽  
Author(s):  
A. Ramiar ◽  
A. A. Ranjbar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Viscous Dissipation ◽  
Conjugate Heat Transfer ◽  
Energy Equation ◽  
Critical Reynolds Number ◽  
Two Dimensional ◽  
Variable Properties ◽  
Enhance Heat Transfer

Laminar two dimensional forced convective heat transfer of Al2O3–water nanofluid in a horizontal microchannel has been studied numerically, considering axial conduction, viscous dissipation and variable properties effects. The existing criteria in the literature for considering viscous dissipation in energy equation are compared for different cases and the most proper one is applied for the rest of the paper. The results showed that nanoparticles enhance heat transfer characteristics of the channel and inversely, viscous dissipation causes the Nusselt number and friction factor to decrease. The viscous dissipation effect may be emphasized by increasing Reynolds number and decreased by raising the exerted heat flux. Also, it was found that there is a critical Reynolds number below which the average Nusselt number of the nanofluid changes abnormally with Reynolds number as a result of variable properties effect.

scholarly journals Numerical study of flow and heat transfer in differentially heated enclosures

2014 ◽  
Vol 18 (2) ◽  
pp. 451-463 ◽  
Author(s):  
Byong-Hoon Chang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Heated Air ◽  
Side Walls ◽  
Laminar Natural Convection

Two-dimensional laminar natural convection is studied numerically for differentially heated air-filled rectangular enclosures with adiabatic side walls and aspect ratios of 1, 2, 4 and 8. The inclination angle of the enclosure was varied from 0? to 180?, and the effect of inclination on flow field and heat transfer was investigated over the range 103 ? Ra ? 106. Correlations of average Nusselt number based on the present results are presented for horizontal and vertical cases. Large discrepancies were found among published results.

scholarly journals Two-Dimensional Variable Property Conjugate Heat Transfer Simulation of Nanofluids in Microchannels

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
A. Ramiar ◽  
A. A. Ranjbar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Conjugate Heat Transfer ◽  
Variable Thermal Conductivity ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Enhancement Of Heat Transfer ◽  
Axial Conduction ◽  
Heat Transfer Simulation ◽  
Dimensional Variable

Laminar two-dimensional forced convective heat transfer of CuO-water and Al2O3-water nanofluids in a horizontal microchannel has been studied numerically, considering axial conduction effects in both solid and liquid regions and variable thermal conductivity and dynamic viscosity. The results show that using nanoparticles with higher thermal conductivities will intensify enhancement of heat transfer characteristics and slightly increases shear stress on the wall. The obtained results show more steep changes in Nusselt number for lower diameters and also higher values of Nusselt number by decreasing the diameter of nanoparticles. Also, by utilizing conduction number as the criterion, it was concluded from the results that adding nanoparticles will intensify the axial conduction effect in the geometry considered.

FREE CONVECTION FROM A HORIZONTAL HEATED CYLINDER LOCATED BELOW A CEILING

1999 ◽  
Vol 23 (1A) ◽  
pp. 19-35 ◽  
Author(s):  
G.B. Lawrence ◽  
G.E. Jardin ◽  
D. Naylor ◽  
A.D. Machin
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Free Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Average Nusselt Number ◽  
Two Dimensional ◽  
Number Range ◽  
Heated Cylinder ◽  
Made In

Steady two-dimensional laminar free convection from a horizontal heated cylinder located beneath a wide ceiling at ambient temperature has been studied. A finite element numerical solution has been obtained for a Prandtl number of Pr = 0.7 and a Rayleigh number range (based on the cylinder diameter) of 102 ≤ Ra ≤ 105. Numerically predicted temperature field and local Nusselt number distributions were compared to experimental measurements made in air using a Mach-Zehnder interferometer. For cylinder- to-ceiling spacings greater than about one diameter, the ceiling was found to have almost no influence on the heat transfer rate from the cylinder. At very close cylinder-to-ceiling spacings, the average Nusselt number increased substantially because of conduction effects. However, for 103 ≤ Ra ≤ 105, the effect of the ceiling on the numerically predicted overall heat transfer rate was less than ±10%, provided the cylinder was more than about one quarter of a diameter away form the ceiling.

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