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.

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.

Computational Study of Heat Transfer in a Conjugate Turbulent Wall Jet Flow at High Reynolds Number

2008 ◽  
Vol 130 (7) ◽  
Author(s):  
E. Vishnuvardhanarao ◽  
Manab Kumar Das
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
High Reynolds Number ◽  
Computational Study ◽  
Local Heat ◽  
Interface Temperature ◽  
Slab Thickness ◽  
Wall Jet ◽  
High Reynolds

In the present case, the conjugate heat transfer involving the cooling of a heated slab by a turbulent plane wall jet has been numerically solved. The bottom of the solid slab is maintained at a hot uniform temperature, whereas the wall jet temperature, is equal to the ambient temperature. The Reynolds number considered is 15,000 because it has already been experimentally found and reported that the flow becomes fully turbulent and is independent of the Reynolds number. The high Reynolds number two-equation model (κ‐ϵ) has been used for the turbulence modeling. The parameters chosen for the study are the conductivity ratio of the solid-fluid (K), the solid slab thickness (S), and the Prandtl number (Pr). The ranges of parameters are K=1–1000, S=1–10, and Pr=0.01–100. Results for the solid-fluid interface temperature, local Nusselt number, local heat flux, average Nusselt number, and average heat transfer are presented and discussed.

NUMERICAL INVESTIGATION OF CONJUGATE HEAT TRANSFER FROM LAMINAR WALL JET FLOW OVER A SHALLOW CAVITY

2018 ◽  
Vol 49 (12) ◽  
pp. 1151-1170 ◽  
Author(s):  
Maheandera Prabu Paulraj ◽  
Rajesh Kanna Parthasarathy ◽  
Jan Taler ◽  
Dawid Taler ◽  
Pawel Oclon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Conjugate Heat Transfer ◽  
Jet Flow ◽  
Wall Jet ◽  
Shallow Cavity ◽  
Wall Jet Flow

Uncoupling the Conjugate Heat Transfer Problem in a Horizontal Plate Under the Influence of a Laminar Flow

2003 ◽  
Author(s):  
Ricardo S. Va´squez ◽  
Antonio J. Bula
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Conjugate Heat Transfer ◽  
Energy Equation ◽  
Transfer Problem ◽  
Heat Transfer Problem ◽  
Interface Temperature ◽  
Horizontal Plate ◽  
Steady State Condition ◽  
Heated Body

The conjugate heat transfer process of cooling a horizontal plate in steady state condition is studied. The model considers both solid and fluid regions in Cartesian coordinates. The problem was solved analytically, considering the fluid flowing in a laminar condition and hydrodynamically developed before any interaction with the heated body. The height of the fluid considered was enough to allow the generation of a thermal boundary layer without any restriction. The conservation of mass, momentum and energy equations were considered to turn the problem into a non dimensional form. The heated body presented a constant heat flux at the bottom side, and convective heat transfer at the top side in contact with the fluid. The other two boundary conditions are adiabatic. The energy equation was considered in the solid to turn it into a non dimensional form. The interface temperature was obtained from a regression using the Chebyshev polynomial approximation. As the problem deals with the cooling of a electronics components, the solution presents the mathematical solution of the energy equation for the solid, including the isothermal lines. The non dimensional form allows a thorough analysis of the problem, considering the influence of the different parameters in the conjugate heat transfer problem. The solution is compared with numerical solution of different problems, and the parameters considered are Reynolds number, plate thickness, Prandtl number, and solid thermal conductivity. The results obtained present isothermal lines, local Nusselt number, and average Nusselt number.

An Experimental Study of the Forcing Effect on the Flow and Heat Transfer in a Turbulent Wall Jet

2015 ◽  
Author(s):  
Johnny Issa ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Stream Flow ◽  
Free Stream ◽  
Maximum Velocity ◽  
Local Maximum ◽  
Jet Flow ◽  
Wall Jet ◽  
Wall Jet Flow ◽  
Turbulent Wall

The effect of the exit wall jet flow excitation on the flow and thermal behaviors of the turbulent wall jet is experimentally investigated. Various forcing amplitudes and frequencies are used in the presence and absence of a free stream flow. Forcing the flow showed to have a major impact on the fluid mechanics of the turbulent wall jet which was clearly shown in the velocity fields and the associated time-averaged quantities such as the wall jet spread and the maximum velocity decay. The normal direction at which the local maximum velocity occurs, also known as the wall jet spreading, is shown to move further away from the wall and is increased by more than 20% under some forcing conditions. The local maximum velocity decay with the downstream direction is reduced by more than 2.5% at further downstream locations. At a given location, the increase in the wall jet spreading together with the reduction in the mean velocity results in a decrease in the wall skin friction calculated using the slope of the mean velocity in the viscous sublayer, a behavior consistent with the literature. Due to its importance in enhancing heat transfer phenomena, the effect of the forcing on the streamwise velocity fluctuations is also investigated under the various forcing conditions. The profiles of the fluctuating component of the velocity, u’, are measured at various downstream locations since they are essential in understanding the growth of the disturbances. Forcing the wall jet increased u’ in the inner and outer regions and revealed the two peaks corresponding to the inner and outer shear layers respectively. This phenomenon is attributed to the added disturbance at the jet exit in addition to the disturbance growth with the downstream direction. The introduction of wall jet flow forcing at various amplitudes and frequencies showed a significant effect on the thermal behavior of the wall jet and was more pronounced in the absence of a free stream flow, a fact related to the evolution of the mixing layer with the downstream direction. In the absence of a free stream flow, Nusselt number decreases with increasing forcing amplitude and frequency in the region close to the jet exit. The decay of Nusselt number in the downstream direction showed an inflection point at further downstream locations which leads to a larger Nusselt number value than the one observed in the unforced case. This behavior is related to the enhanced mixing between the wall jet flow and the free stream due to forcing, which results in a reduction in the wall skin friction and consequently a decrease in the heat transfer rate from the wall.

scholarly journals Laminar Wall Jet Flow and Heat Transfer over a Shallow Cavity

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
P. Maheandera Prabu ◽  
K. P. Padmanaban
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Vortex Formation ◽  
Leading Edge ◽  
Step Length ◽  
Jet Flow ◽  
Maximum Temperature ◽  
Wall Jet ◽  
Shallow Cavity ◽  
Wall Jet Flow

This paper presents the detailed simulation of two-dimensional incompressible laminar wall jet flow over a shallow cavity. The flow characteristics of wall jet with respect to aspect ratio (AR), step length (Xu), and Reynolds number (Re) of the shallow cavity are expressed. For higher accuracy, third-order discretization is applied for momentum equation which is solved using QUICK scheme with SIMPLE algorithm for pressure-velocity coupling. Low Reynolds numbers 25, 50, 100, 200, 400, and 600 are assigned for simulation. Results are presented for streamline contour, velocity contour, and vorticity formation at wall and also velocity profiles are reported. The detailed study of vortex formation on shallow cavity region is presented for various AR,Xu, and Re conditions which led to key findings as Re increases and vortex formation moves from leading edge to trailing edge of the wall. Distance between vortices increases when the step length (Xu) increases. When Re increases, the maximum temperature contour distributions take place in shallow cavity region and highest convection heat transfer is obtained in heated walls. The finite volume code (FLUENT) is used for solving Navier-Stokes equations and GAMBIT for modeling and meshing.

Numerical Simulation of Two-Dimensional Laminar Incompressible Wall Jet Flow Under Backward-Facing Step

2006 ◽  
Vol 128 (5) ◽  
pp. 1023-1035 ◽  
Author(s):  
P. Rajesh Kanna ◽  
Manab Kumar Das
Keyword(s):  
Linear Trend ◽  
Step Length ◽  
Jet Flow ◽  
Step Height ◽  
Jet Flows ◽  
Wall Jet ◽  
Two Dimensional ◽  
Backward Facing Step ◽  
Navier Stokes Equation ◽  
Wall Jet Flow

Two-dimensional laminar incompressible wall jet flow over a backward-facing step is solved numerically to gain insight into the expansion and recirculation of flow processes. Transient streamfunction vorticity formulation of the Navier-Stokes equation is solved with clustered grids on the physical domain. The behavior of the jet has been studied for different step geometry (step length, l, step height, s) and Reynolds number (Re). It is found that the presence of a step in the wall jet flow creates recirculation and the reattachment length follows an almost linear trend within the range considered for both parameters Re and step geometry. Simulations are made to show the effect of entrainment on recirculation eddy. Detailed study of u velocity decay is reported. The velocity profile in the wall jet region shows good agreement with experimental as well as similarity results. The distance where the similarity profile forms is reduced by increasing the step geometry whereas an increment in Re increases this distance. The effects of Re, step length, and step height on wall vorticity are presented. The parametric study is helpful to predict the reattachment location for wall jet flows over step.

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