Optimizing a Functionally Graded Metal-Matrix Heat Sink Through Growth of a Constructal Tree of Convective Fins

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Jacob Kephart ◽  
G. F. Jones
Keyword(s):  
Heat Sink ◽  
Metal Matrix ◽  
Heated Surface ◽  
Electronics Cooling ◽  
Functionally Graded ◽  
Aspect Ratios ◽  
Volume Porosity ◽  
Convective Fin ◽  
Matrix Heat ◽  
Fin Shape

Optimal material utilization in metal-matrix heat sink is investigated using constructal design (CD) in combination with fin theory to develop a constructal tree of optimally shaped convective fins. The structure is developed through systematic growth of constructs, consisting initially of a single convective fin enveloped in a convective medium. Increasingly complex convective fin structures are created and optimized at each level of complexity to determine optimal fin shapes, aspect ratios, and fin-base thickness ratios. One result of the optimized structures is a functional grading of porosity. The porosity increases as a function of distance from the heated surface in a manner ranging from linear to a power function of distance with exponent of about 2. The degree of nonlinearity in this distribution varies depending on the volume of the heat sink and average packing density and approaches a parabolic shape for large volume. For small volume, porosity approaches a linear function of distance. Thus, a parabolic (or least-material) fin shape at each construct level would not necessarily be optimal. Significant improvements in total heat transfer, up to 55% for the cases considered in this work, were observed when the fin shape is part of the optimization in a constructal tree of convective fins. The results of this work will lead to better understanding of the role played by the porosity distribution in a metal-matrix heat sink and may be applied to the analysis, optimization, and design of more effective heat sinks for electronics cooling and related areas.

Material Distribution Optimization in a Metal Matrix Heat Sink Using a Constructal-Design Inspired Unit T-Cell

2017 ◽  
Author(s):  
Jacob Kephart ◽  
G. F. Jones
Keyword(s):  
T Cell ◽  
Heat Sink ◽  
Metal Matrix ◽  
Unit Cell ◽  
Material Distribution ◽  
Two Dimensional ◽  
Aspect Ratios ◽  
The Matrix ◽  
Unit Cells ◽  
Matrix Heat

Constructal principles are used to investigate the optimization of material utilization in a metal matrix heat sink that maximizes the total heat transfer rate through the base of heat sink. This approach utilizes a two-dimensional geometry to examine spatial heat flow and optimal material distribution in a metal matrix in the plane perpendicular to the coolant flow direction. The matrix is composed of multiple layers of conductive tees built up from the smallest constituent, the unit T-cell. The unit cell consists of a conductive tee-shaped geometry with the two rectangular void regions each making up half of a cooling channel. The horizontal boundaries must match the temperature and heat flux at the boundaries of the neighboring unit cells as this is a conjugate conduction/convection problem. The geometry of the unit cell is characterized by aspect ratios of channel width to height, overall cell width to height, and channel height to cell height. The matrix structure is assembled by stacking unit cells into multiple layers where the number of cells in each layer is an integer multiple of the cells contained in the lower layer. The solution is obtained for optimal T-cell geometric parameters under a set of predetermined constraints including overall volume, solid fill fraction, and number of layers. When a large number of stacked unit cells are considered, the results describe the ideal spatial distribution of porosity and pore sizes for two dimensional functionally graded metal-matrix heat sink. These results will lead to a better understanding of the role played by the porosity distribution in a metal-matrix heat sink and may be applied to the analysis, optimization, and design of more effective heat sinks.

Optimizing a Functionally Graded Metal-Matrix Heat Sink Through Growth of a Constructal Tree of Convective Fins

2013 ◽  
Author(s):  
Jacob Kephart ◽  
G. F. Jones
Keyword(s):  
Porous Media ◽  
Heat Exchanger ◽  
Metal Matrix ◽  
Metal Foam ◽  
Functionally Graded ◽  
Constructal Theory ◽  
Fixed Amount ◽  
Surface Areas ◽  
Optimal Material ◽  
Matrix Heat

This work focuses on an analytical approach to understand optimal material utilization in metal matrix heat exchangers. An objective of this work is to develop a bridge between a fully defined and discrete structure to that of a functionally graded porous media. A porous media heat exchanger is a structure which uses porous material, such as a metal foam, to achieve large convective surface areas in a small volume while also using the media as a conductive path from the heat source or sink. Therefore, a functionally graded porous media heat exchanger has a porosity that is specified as a function of position. Constructal theory is used here to develop increasingly complex convective fin structures, optimized at each level of complexity, which have a resulting characteristic of 2-D functional grading. The approach described here is developed from first principles by using Fourier’s law to develop analytical solutions and seeks to yield an optimized heat exchanger configuration that maximizes total heat transfer subject to a fixed amount conductive material, total volume, and flow condition.

Parametric Studies of Single-Phase Multi-Layer Heat Sinks Using a Porous Media Approach: Effects of Spatially-Varying Porosity and Total Porosity

2014 ◽  
Author(s):  
John J. Podhiny ◽  
Alfonso Ortega
Keyword(s):  
Porous Media ◽  
Heat Sink ◽  
Heated Surface ◽  
Continuous Variation ◽  
Heat Sinks ◽  
Optimum Level ◽  
Fluid Temperature ◽  
Porosity Variation ◽  
Aspect Ratios ◽  
Spatially Varying

Prior analyses and experiments have demonstrated that varying or scaling the number of fluid channels in each layer of a stacked multi-layer heat sink yields distinct advantages over traditional single-layer designs which use channels with high aspect ratios. Specifically, a design which implements scaling in order to vary the porosity (or equivalently, the number of channels) from one layer to the next allows a given thermal performance to be realized at a lower pressure drop than the corresponding non-scaled design. In previous work, the authors have used volume-averaged non-equilibrium porous media heat transfer theory to analyze a range of heat sinks of this type, including those with discrete or step-wise porosity variation (in earlier efforts) and continuous porosity variation (in more recent efforts). The authors have used discrete variation to model stacked mini-channel multi-later heat exchangers, and continuous variation as a more general investigative tool for this class of heat sinks. The continuous variation approach can also be used as a design tool for heat sink envelopes that use scaled micro- or nano-channels or engineered porous media with spatially varying porosity or pore diameter. This paper reports on the results of a parametric study of water-cooled copper heat sinks which employ 0.50 mm × 0.50 mm square channels in a range of porosity scaling profiles that yield and total integrated porosities of 0.10 to 0.95. The investigation identifies the highest and lowest performing designs based upon temperatures on the heated surface, and analyzes their performance characteristics in terms of the spatial distributions of solid and fluid temperature distributions, thermal resistance components and ratios, and conductive and convective heat flows. In general, the results imply the existence of an optimum level and distribution of porosity and confirm the potential benefits of spatial variation of porosity.

On heated surface transport of heat bearing thermal radiation and MHD Cross flow with effects of nonuniform heat sink/source and buoyancy opposing/assisting flow

Heat Transfer ◽  
2021 ◽  
Author(s):  
Assad Ayub ◽  
Hafiz A. Wahab ◽  
Syed Zahir Hussain Shah ◽  
Syed Latif Shah ◽  
Zulqurnain Sabir ◽  
...  
Keyword(s):  
Thermal Radiation ◽  
Heat Sink ◽  
Heated Surface ◽  
Cross Flow ◽  
Surface Transport

Two-Phase Flow in Microchannels

2001 ◽  
Author(s):  
G. Hetsroni ◽  
A. Mosyak ◽  
Z. Segal
Keyword(s):  
Heat Sink ◽  
High Speed ◽  
Single Phase ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
Working Fluid ◽  
Microchannel Heat Sink ◽  
Two Phase ◽  
Infrared Radiometry ◽  
Phase Water

Abstract Experimental investigation of a heat sink for electronics cooling is performed. The objective is to keep the operating temperature at a relatively low level of about 323–333K, while reducing the undesired temperature variation in both the streamwise and transverse directions. The experimental study is based on systematic temperature, flow and pressure measurements, infrared radiometry and high-speed digital video imaging. The heat sink has parallel triangular microchannels with a base of 250μm. According to the objectives of the present study, Vertrel XF is chosen as the working fluid. Experiments on flow boiling of Vertrel XF in the microchannel heat sink are performed to study the effect of mass velocity and vapor quality on the heat transfer, as well as to compare the two-phase results to a single-phase water flow.

THERMAL AND HYDRODYNAMIC PERFORMANCE OF A MICROCHANNEL HEAT SINK COOLED WITH CARBON NANOTUBES NANOFLUID

2016 ◽  
Vol 78 (10-2) ◽  
Author(s):  
Nik Ahmad Faiz Nik Mazlam ◽  
Normah Mohd-Ghazali ◽  
Thierry Mare ◽  
Patrice Estelle ◽  
Salma Halelfadl
Keyword(s):  
Thermal Resistance ◽  
Heat Sink ◽  
Operating Temperature ◽  
Heat Removal ◽  
Hydrodynamic Performance ◽  
Spherical Particles ◽  
Microchannel Heat Sink ◽  
Pumping Power ◽  
Rectangular Microchannel ◽  
Aspect Ratios

The microchannel heat sink (MCHS) has been established as an effective heat removal system in electronic chip packaging. With increasing power demand, research has advanced beyond the conventional coolants of air and water towards nanofluids with their enhanced heat transfer capabilities. This research had been carried out on the optimization of the thermal and hydrodynamic performance of a rectangular microchannel heat sink (MCHS) cooled with carbon nanotube (CNT) nanofluid, a coolant that has recently been discovered with improved thermal conductivity. Unlike the common nanofluids with spherical particles, nanotubes generally come in cylindrical structure characterized with different aspect ratios. A volume concentration of 0.1% of the CNT nanofluid is used here; the nanotubes have an average diameter and length of 9.2 nm and 1.5 mm respectively. The nanofluid has a density of 1800 kg/m3 with carbon purity 90% by weight having lignin as the surfactant. The approach used for the optimization process is based on the thermal resistance model and it is analyzed by using the non-dominated sorting multi-objective genetic algorithm. Optimized outcomes include the channel aspect ratio and the channel wall ratio at the optimal values of thermal resistance and pumping power. The optimized results show that, at high operating temperature of 40°C the use of CNT nanofluid reduces the total thermal resistance by 3% compared to at 20°C and consequently improve the thermal performance of the fluid. In terms of the hydrodynamic performance, the pumping power is also being reduced significantly by 35% at 40°C compared to the lower operating temperature.  

Thermal-Structural Performance of Orthotropic Pin Fin in Electronics Cooling Applications

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
A. F. M. Arif ◽  
Syed M. Zubair ◽  
S. Pashah
Keyword(s):  
Heat Sink ◽  
Structural Response ◽  
Electronics Cooling ◽  
Base Plate ◽  
Thermal Design ◽  
Heat Flow Rate ◽  
Thermal Interface ◽  
Conductive Composites ◽  
Thermally Conductive ◽  
As Stress

Thermally conductive composites as compared to metals have reduced density, decreased oxidation, and improved chemical resistance, as well as adjustable properties to fit a given application. However, there are several challenges that need to be addressed before they can be successfully implemented in heat sink design. The interface between the device and heat sink is an important factor in the thermal design of microelectronics cooling. Depending on the thermal interface conditions and material properties, the contact pressure and thermal stress level can attain undesirable values. In this paper, we investigate the effect of thermal interface between the fin and base plate on thermal-structural behavior of heat sinks. A coupled-field (thermal-structural) analysis using finite element method is performed to predict temperature as well as stress fields in the interface region. In addition temperature and heat flow rate predictions are supported through analytical results. effect of various interface geometrical (such as slot-depth, axial-gap, and radial-gap) and contact properties (such as air gap with surface roughness and gaps filled with interface material) on the resulting thermal-structural response is investigated with respect to four interface materials combinations, and it is found that the thermal performance is most sensitive to the slot-depth compared to any other parameter.

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