Computational Analysis of Conjugate Heat Transfer in Gaseous Microchannels

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Giulio Croce ◽  
Olga Rovenskaya ◽  
Paola D'Agaro
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mach Number ◽  
Heat Sink ◽  
Conjugate Heat Transfer ◽  
Stokes Equations ◽  
Heat Transfer Analysis ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Navier Stokes Equations

A fully conjugate heat transfer analysis of gaseous flow in short microchannels is presented. Navier–Stokes equations, coupled with Maxwell and Smoluchowski slip and temperature jump boundary conditions, are used for numerical analysis. Results are presented in terms of Nusselt number, heat sink thermal resistance, and resulting wall temperature as well as Mach number profiles for different flow conditions. The comparative importance of wall conduction, rarefaction, and compressibility are discussed. It was found that compressibility plays a major role. Although a significant penalization in the Nusselt number, due to conjugate heat transfer effect, is observed even for a small value of solid conductivity, the performances in terms of heat sink efficiency are essentially a function only of the Mach number.

Design of a Fractal Tree-Like Microchannel Net Heat Sink for Microelectronic Cooling

2006 ◽  
Author(s):  
F. J. Hong ◽  
P. Cheng ◽  
H. Ge ◽  
Teck Joo Goh
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Electronic Cooling ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Numerical Result ◽  
Parallel Microchannels

In this paper, a numerical simulation is carried to study pressure drop and heat transfer in a fractal tree-like microchannel net heat sink of 10mm×12.5mm×0.5mm in dimensions. The numerical result is obtained by solving three-dimensional Navier-Stokes equations and energy equation, taking into consideration conjugate heat transfer in the microchannel walls. A comparison of fractal tree-like microchannel net heat sink with 6 branch levels to parallel microchannels heat sink, with respect to the pressure drop, thermal resistance and temperature uniformity, was also performed under the condition of the same heat sink dimensions. The results indicates that for a mass flow rate of water less than 0.00175kg/s, the fractal tree-like microchannel is much better than parallel channel heat sink with respect to all of three aspects. Therefore, the fractal tree-like microchannels net heat sink using water as the coolant is promising to be used in the future electronic cooling industry.

An Implicit Scheme for Cascade Flow and Heat Transfer Analysis

1999 ◽  
Vol 122 (2) ◽  
pp. 294-300 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Implicit Scheme ◽  
Heat Transfer Analysis ◽  
Navier Stokes ◽  
Computational Time ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Intermediate Time ◽  
The Difference

A new efficient implicit scheme, based on the second-order time and spatial difference algorithm for solving steady flow by using time-marching Navier–Stokes equations, was developed for predicting turbine cascade flows and heat transfer. The difference scheme comprises an explicit part in the intermediate time-step and an implicit part in the local time-step. The viscous flux vectors are decomposed to simplify the flow calculation in the explicit step. The time difference terms are expressed in terms of the viscous dependent terms that appear in the diffusion terms in the form by adding eigenvalues of viscous flux matrices into the time derivation term. In the presently proposed scheme, the two-sweep procedure is used in the implicit step instead of employing a traditional matrix operation to save the computational time. This method has been used to calculate the flow around C3X and VKI cascades. The computed results were compared with experimental data as well as with other published computations. The comparisons for both surface pressure and heat transfer coefficient showed good agreement with the experiments. [S0889-504X(00)01702-5]

Effect of Heat Transfer on Magnetohydrodynamic Axisymmetric Flow Between Two Stretching Sheets

2010 ◽  
Vol 65 (11) ◽  
pp. 961-968 ◽  
Author(s):  
Tasawar Hayat ◽  
Muhammad Nawaz
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Stokes Equations ◽  
Axisymmetric Flow ◽  
Skin Friction Coefficient ◽  
Navier Stokes ◽  
Tabular Form ◽  
Analysis Method ◽  
Navier Stokes Equations ◽  
Homotopy Analysis

This investigation describes the effects of heat transfer on magnetohydrodynamic (MHD) axisymmetric flow of a viscous fluid between two radially stretching sheets. Navier-Stokes equations are transformed into the ordinary differential equations by utilizing similarity variables. Solution computations are presented by using the homotopy analysis method. The convergence of obtained solutions is checked. Skin friction coefficient and Nusselt number are given in tabular form. The dimensionless velocities and temperature are also analyzed for the pertinent parameters entering into the problem.

Simulation of Jet Impingement Heat Transfer

2013 ◽  
Author(s):  
G. Nasif ◽  
R. M. Barron ◽  
R. Balachandar ◽  
O. Iqbal
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Stokes Equations ◽  
Thermal Characteristics ◽  
Jet Impingement ◽  
Navier Stokes ◽  
Uniform Heat Flux ◽  
Two Phase ◽  
Stagnation Region ◽  
Navier Stokes Equations

A numerical investigation to determine flow and thermal characteristics of an unsubmerged axisymmetric oil jet impinging on a confined flat surface with uniform heat flux has been undertaken. Large impingement length to nozzle diameter ratios were chosen in the simulations. The volume of fluid (VOF) method utilizing a High Resolution Interface Capturing scheme (HRIC) was used to perform the two-phase (air-oil) simulations. The governing 3D Navier-Stokes equations and energy equation were numerically solved using a finite volume discretization on an unstructured mesh. A new methodology was developed to define the radial extent of the stagnation region and understand the variation of the heat transfer coefficient in this region. The normalized local Nusselt number profile was found to be slightly dependent on Reynolds number for a given nozzle size. Correlations to predict the dimensionless velocity gradient and the Nusselt number in the stagnation region were established.

Hydrodynamics and Heat Transfer of an Oblique Plane Jet Impinging Onto a Substrate

2002 ◽  
Author(s):  
Albert Y. Tong
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Stokes Equations ◽  
Piecewise Linear ◽  
Analytical Data ◽  
Jet Impingement ◽  
Navier Stokes ◽  
Maximum Pressure ◽  
Navier Stokes Equations ◽  
Plane Jet

The objective of the present study is to understand the hydrodynamics and heat transfer of the impingement process, particularly the complexities attributable to the asymmetric geometry of an oblique free liquid jet. The Navier-Stokes equations are solved using a finite-volume formulation with a two-step projection method on a fixed non-uniform rectangular grid. The free surface of the jet is tracked by the volume-of-fluid (VOF) method with a second order accurate piecewise-linear scheme. The energy equation is modeled by using an enthalpy-based formulation. The method provides a state-of-the-art comprehensive model of the dynamic and thermal aspects of the impinging process. Nusselt number plots and pressure distributions on the substrate are obtained. The locations of the maximum Nusselt number as well as maximum pressure on the surface are identified and compared with the geometric jet impingement point. Results for normal impingement are also obtained and are used as reference. The effects of several parameters are examined. These include jet Reynolds number, jet impingement angle and jet inlet velocity profile. Experimental and analytical data from the literature are also included for comparison.

scholarly journals An Implicit Scheme for Cascade Flow and Heat Transfer Analysis

1999 ◽  
Author(s):  
C. Xu ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Implicit Scheme ◽  
Heat Transfer Analysis ◽  
Navier Stokes ◽  
Computational Time ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Intermediate Time ◽  
The Difference

A new efficient implicit scheme, based on the second-order time and spatial difference algorithm for solving steady flow by using time-marching Navier-Stokes equations, was developed for predicating turbine cascade flows and heat transfer. The difference scheme comprises an explicit part in the intermediate time-step and an implicit part in the local time-step. The viscous flux-vectors are decomposed to simplify the flow calculation in the explicit step. The time difference terms are expressed in terms of the viscous dependent terms which appear in the diffusion terms in the form by adding eigenvalues of viscous flux matrices into the time derivation term. In the presently proposed scheme, the two-sweep procedure is used in the implicit step instead of employing a traditional matrix operation to save the computational time. This method has been used to calculate the flow around C3X and VKI cascades. The computed results were compared with experimental data as well as with other published computations. The comparisons for both surface pressure and heat transfer coefficient showed good agreement with the experiments.

Numerical Simulation of Solar Radiation and Conjugate Heat Transfer through Cabin Seat Textile

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Yijie Zhang ◽  
Juhong Jia
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Conjugate Heat Transfer ◽  
Radiative Heat ◽  
Stokes Equations ◽  
Thermal Environment ◽  
Heat Radiation ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Lower Temperature

AbstractThe solar radiation and the conjugate heat transfer through the cabin seat fabric were investigated numerically with a focus on a comparative analysis of various fabric solar reflectance or reflectivity (SR) and inlet cooling air velocity. For this purpose, 3D compressible Reynolds-averaged Navier–Stokes equations with the low Reynolds number turbulence model were utilized to simulate the airflow in the cabin. The discrete ordinate radiation model was adopted to describe the solar radiation. The conjugate heat transfer between the airflow and the fabric seats was included. The airflow temperature, radiative heat flux, and radiative heat transfer through the fabrics in a fixed cross section were studied. The results demonstrate that the increase in fabric SR leads to the increase in energy reflected to the atmosphere, which will bring about a lower temperature on the seat fabric. The decrease in emissivity and the energy absorbed results in the lower heat transfer and heat radiation and leads to the improvement of the cabin thermal environment. The high-temperature gradient near the seat causes the forced air circulation and is beneficial for the improvement of the thermal comfort. However, the cooling effect is not so obvious near the cabin seats when the inflow speed is increased.

scholarly journals Cooling analysis of a light emitting diode automotive fog lamp

2017 ◽  
Vol 21 (1 Part B) ◽  
pp. 757-766
Author(s):  
Matej Zadravec ◽  
Matjaz Ramsak ◽  
Jure Ravnik ◽  
Matjaz Hribersek ◽  
Jernej Slanovec
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Sink ◽  
Stokes Equations ◽  
Light Emitting Diode ◽  
Navier Stokes ◽  
Radiation Model ◽  
Navier Stokes Equations ◽  
Light Emitting

Efficiency of cooling fins inside of a light emitting diode fog lamp is studied using computational fluid dynamics. Diffusion in heat sink, natural convection and radiation are the main principles of the simulated heat transfer. The Navier-Stokes equations were solved by the computational fluid dynamics code, including Monte Carlo radiation model and no additional turbulence model was needed. The numerical simulation is tested using the existing lamp geometry and temperature measurements. The agreement is excellent inside of few degrees at all measured points. The main objective of the article is to determine the cooling effect of various heat sink parts. Based on performed simulations, some heat sink parts are found to be very ineffective. The geometry and heat sink modifications are proposed. While radiation influence is significant, compressible effects are found to be minor.

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