scholarly journals Direct Simulation of Thermal Transport Through Sintered Wick Microstructures

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Karthik K. Bodla ◽  
Jayathi Y. Murthy ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Effective Thermal Conductivity ◽  
Thermal Transport ◽  
Heat Pipes ◽  
Interfacial Heat Transfer Coefficient ◽  
Interfacial Heat Transfer ◽  
Particle Beds

Porous sintered microstructures are critical to the functioning of passive heat transport devices such as heat pipes. The topology and microstructure of the porous wick play a crucial role in determining the thermal performance of such devices. Three sintered copper wick samples employed in commercial heat pipes are characterized in this work in terms of their thermal transport properties––porosity, effective thermal conductivity, permeability, and interfacial heat transfer coefficient. The commercially available samples of nearly identical porosities (∼61% open volume) are CT scanned at 5.5 μm resolution, and the resulting image stack is reconstructed to produce high-quality finite volume meshes representing the solid and interstitial pore regions, with a conformal mesh at the interface separating these two regions. The resulting mesh is then employed for numerical analysis of thermal transport through fluid-saturated porous sintered beds. Multiple realizations are employed for statistically averaging out the randomness exhibited by the samples under consideration. The effective thermal conductivity and permeability data are compared with analytical models developed for spherical particle beds. The dependence of effective thermal conductivity of sintered samples on the extent of sintering is quantified. The interfacial heat transfer coefficient is compared against a correlation from the literature based on experimental data obtained with spherical particle beds. A modified correlation is proposed to match the results obtained.

Thermal Modeling for High Thermal Conductivity Thermal Ground Planes

2012 ◽  
Author(s):  
Mohammed T. Ababneh ◽  
Pramod Chamarthy ◽  
Shakti Chauhan ◽  
Frank M. Gerner ◽  
Peter de Bock ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Energy Balance ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Interfacial Energy ◽  
Interfacial Heat Transfer Coefficient ◽  
Interfacial Heat Transfer ◽  
Vapor Liquid

Thermal ground planes (TGPs) are flat, thin (external thickness of 2 mm) heat pipes which utilize two-phase cooling. The goal is to utilize TGPs as thermal spreaders in a variety of microelectronic cooling applications. TGPs are novel high-performance, integrated systems able to operate at a high power density with a reduced weight and temperature gradient. In addition to being able to dissipate large amounts of heat, they have very high effective axial thermal conductivities and (because of nano-porous wicks) can operate in high adverse gravitational fields. A three-dimensional (3D) finite element model is used to predict the thermal performance of the TGP. The 3D thermal model predicts the temperature field in the TGP, the effective axial thermal conductivity, and the evaporation and the condensation rates. A key feature of this model is that it relies on empirical interfacial heat transfer coefficient data to very accurately model the interfacial energy balance at the vapor-liquid saturated wick interface. Wick samples for a TGP are tested in an experimental setup to measure the interfacial heat transfer coefficient. Then the experimental heat transfer coefficient data are used for the interfacial energy balance. Another key feature of this model is that it demonstrates that for the Jakob numbers of interest, the thermal and flow fields can be decoupled except at the vapor-liquid saturated wick interface. This model can be used to predict the performance of a TGP for different geometries and implementation structures. This paper will describe the model and how it incorporates empirical interfacial heat transfer coefficient data. It will then show theoretical predictions for the thermal performance of TGP’s, and compare with experimental results.

A Correlation for Interfacial Heat Transfer Coefficient for Turbulent Flow Over an Array of Square Rods

2005 ◽  
Vol 128 (5) ◽  
pp. 444-452 ◽  
Author(s):  
Marcelo B. Saito ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Transfer Coefficient ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Energy Equation ◽  
Local Thermal Equilibrium ◽  
Equation Modeling ◽  
Interfacial Heat Transfer Coefficient ◽  
Interfacial Heat Transfer

Interfacial heat transfer coefficients in a porous medium modeled as a staggered array of square rods are numerically determined. High and low Reynolds k-ϵ turbulence models are used in conjunction of a two-energy equation model, which includes distinct transport equations for the fluid and the solid phases. The literature has documented proposals for macroscopic energy equation modeling for porous media considering the local thermal equilibrium hypothesis and laminar flow. In addition, two-energy equation models have been proposed for conduction and laminar convection in packed beds. With the aim of contributing to new developments, this work treats turbulent heat transport modeling in porous media under the local thermal nonequilibrium assumption. Macroscopic time-average equations for continuity, momentum, and energy are presented based on the recently established double decomposition concept (spatial deviations and temporal fluctuations of flow properties). The numerical technique employed for discretizing the governing equations is the control volume method. Turbulent flow results for the macroscopic heat transfer coefficient, between the fluid and solid phase in a periodic cell, are presented.

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