A Comparison of Numerical Strategies for Optimal Liquid Cooled Heat Sink Design

2016 ◽  
Author(s):  
Ali C. Kheirabadi ◽  
Dominic Groulx
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Parametric Design ◽  
Three Dimensional ◽  
Primary Objective ◽  
Design Tool ◽  
Unit Cell ◽  
Channel Width ◽  
Pressure Drops ◽  
Temperature And Pressure

This study compares two common numerical strategies for modeling flow and heat transfer through mini- and micro-channel heat sinks: the unit cell approach and a complete three dimensional unified approach. Conjugate heat transfer and laminar flow through a copper-water heat sink over a 2×2 cm2 heat source have been modelled using the finite element method within COMSOL Multiphysics 5.0; with the primary objective being to identify the channel width at which the two models yield similar temperature and pressure predictions. Parametric studies that varied channel widths showed that as these widths were reduced, and the total number of channels increased, temperature and pressure predictions from both models converged to similar values. Relative differences as low as 5.4 and 1.6 % were attained at a channel width of 0.25 mm for maximum wall temperatures and channel pressure drops, respectively. Based upon its computational efficiency and conservative over prediction of wall temperatures, the unit cell approach is recommended as a superior design tool for parametric design studies at channel widths of less than 0.5 mm.

Thermal Performance of Two and Three Dimensional Radial Flow Heat Sinks

2009 ◽  
Author(s):  
Ronan Grimes ◽  
Kieran Hanly ◽  
Edmond Walsh
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Angular Displacement ◽  
Three Dimensional ◽  
Heat Sinks ◽  
Electronic Systems ◽  
Two Dimensional ◽  
Pressure Drops ◽  
Low Profile ◽  
Fin Spacing

Space and power constraints in many contemporary electronic systems place a greater importance than ever on efficient thermal management solutions. This paper investigates the performance and optimisation of air cooled heat sinks suitable for deployment in compact electronic devices. The heat sinks examined have circular footprint, with air flowing from the centre, radially outwards through radially aligned channels. Heat sink height is examined through experiments which were performed on heat sinks with high and low fins, with two and three dimensional flow and heat transfer phenomena respectively. In both cases the effect of angular fin spacing is investigated to determine optimum fin spacing for a range of heat sink pressure drops. Heat transfer correlations from literature which were originally developed for parallel finned heat sinks are compared with the experimental data. The main findings of the paper are that the performance of the high profile two dimensional heat sink is more sensitive to fin angular displacement than low profile three dimensional heat sinks. The parallel fin correlations from literature were found to predict the performance of the three dimensional heat sinks more accurately than the two dimensional heat sinks.

The Effectiveness of the Unit Cell Method in Numerically Modeling and Designing Liquid Cooled Heatsinks

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Ali C. Kheirabadi ◽  
Dominic Groulx
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Parametric Design ◽  
Unit Cell ◽  
Liquid Cooling ◽  
Cell Method ◽  
Numerical Predictions ◽  
Finite Element Package ◽  
Parametric Studies ◽  
Relative Differences

This study compares two numerical strategies for modeling flow and heat transfer through mini- and microchannel heatsinks, the unit cell approximation, and the full 3D model, with the objective of validating the former approach. Conjugate heat transfer and laminar flow through a 2 × 2 cm2 copper–water heatsink are modeled using the finite element package COMSOL Multiphysics 5.0. Parametric studies showed that as the heatsink channels’ widths were reduced, and the total number of channels increased, temperature and pressure predictions from both models converged to similar values. Relative differences as low as 5.4% and 1.6% were attained at a channel width of 0.25 mm for maximum wall temperature and channel pressure drop, respectively. Due to its computational efficiency and tendency to conservatively overpredict temperatures relative to the full 3D method, the unit cell approximation is recommended for parametric design of heatsinks with channels’ widths smaller than 0.5 mm, although this condition only holds for the given heatsink design. The unit cell method is then used to design an optimal heatsink for server liquid cooling applications. The heatsink has been fabricated and tested experimentally, and its thermal performance is compared with numerical predictions. The unit cell method underestimated the maximum wall temperature relative to experimental results by 3.0–14.5% as the flowrate rose from 0.3 to 1.5 gal/min (1.1–5.7 l/min).

Heat transfer characteristic modelling and the effect of operating conditions on re-cooled cycle for a scramjet

2011 ◽  
Vol 115 (1164) ◽  
pp. 83-90 ◽  
Author(s):  
W. Bao ◽  
J. Qin ◽  
W. X. Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Transfer Characteristic ◽  
Cooling Capacity ◽  
Sensitivity Study ◽  
Performance Model ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Fuel Flow ◽  
Temperature And Pressure

Abstract A re-cooled cycle has been proposed for a regeneratively cooled scramjet to reduce the hydrogen fuel flow for cooling. Upon the completion of the first cooling, fuel can be used for secondary cooling by transferring the enthalpy from fuel to work. Fuel heat sink (cooling capacity) is thus repeatedly used and fuel heat sink is indirectly increased. Instead of carrying excess fuel for cooling or seeking for any new coolant, the cooling fuel flow is reduced, and fuel onboard is adequate to satisfy the cooling requirement for the whole hypersonic vehicle. A performance model considering flow and heat transfer is build. A model sensitivity study of inlet temperature and pressure reveals that, for given exterior heating condition and cooling panel size, fuel heat sink can be obviously increased at moderate inlet temperature and pressure. Simultaneously the low-temperature heat transfer deterioration and Mach number constrains can also be avoided.

scholarly journals OPTIMALLY STAGGERED FINNED CIRCULAR AND ELLIPTIC TUBES IN FORCED CONVECTION

2003 ◽  
Vol 2 (2) ◽  
pp. 65 ◽  
Author(s):  
R. S. Matos ◽  
T. A. Laursen ◽  
J. V. C. Vargas ◽  
A. Bejan
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Optimization Procedure ◽  
Total Heat ◽  
Cross Sectional ◽  
Maximum Heat ◽  
Pressure Drops ◽  
Tube Cross Section ◽  
Fixed Volume ◽  
Maximum Heat Transfer

This work presents a three-dimensional (3-D) numerical and experimental geometric optimization study to maximize the total heat transfer rate between a bundle of finned tubes in a given volume and a given external flow both for circular and elliptic arrangements, for general staggered configurations. The optimization procedure started by recognizing the design limited space availability as a fixed volume constraint. The experimental results were obtained for circular and elliptic configurations with a fixed number of tubes (12), starting with an equilateral triangle configuration, which fitted uniformly into the fixed volume with a resulting maximum dimensionless tube-to-tube spacing S/2b = 1.5, where S is the actual spacing and b is the smaller ellipse semi-axis. Several experimental configurations were built by reducing the tube-to-tube spacings, identifying the optimal spacing for maximum heat transfer. Similarly, it was possible to investigate the existence of optima with respect to other two geometric degrees of freedom, i.e., tube eccentricity and fin-to-fin spacing. The results are reported for air as the external fluid in the laminar regime, for 125 and 100 Re 2b , where 2b is the ellipses smaller axis length. Circular and elliptic arrangements with the same flow obstruction cross-sectional area were compared on the basis of maximum total heat transfer. This criterion allows one to quantify the heat transfer gain in the most isolated way possible, by studying arrangements with equivalent total pressure drops independently of the tube cross section shape. This paper reports three-dimensional (3- D) numerical optimization results for finned circular and elliptic tubes arrangements, which are validated by direct comparison with experimental measurements with good agreement. Global optima with respect to tube-to-tube spacing, eccentricity and fin-tofin spacing ( 0.5 e 0.5, S/2b and 06 . 0 f for 125 and 100 Re 2b , respectively) were found and reported in general dimensionless variables. A relative heat transfer gain of up to 19% is observed in the optimal elliptic arrangement, as compared to the optimal circular one. The heat transfer gain, combined with the relative material mass reduction of up to 32% observed in the optimal elliptic arrangement in comparison to the circular one, show the elliptical arrangement has the potential for a considerably better overall performance and lower cost than the traditional circular geometry.

scholarly journals On the formulation of green open space planning parameters: A parametric tool

2017 ◽  
Author(s):  
T.M. Leung ◽  
Irina Kukina ◽  
Anna Yuryevna-Lipovka
Keyword(s):  
Open Space ◽  
Parametric Design ◽  
Primary Objective ◽  
Design Tool ◽  
Tree Planting ◽  
Width Ratio ◽  
Open Spaces ◽  
Space Planning ◽  
Open Space Planning ◽  
Solar Access

Greenery can affect spatial characteristics such as relationship between hard and soft surfaces and activities inside open spaces. Among different types of greenery, trees have influences on summer shading and winter solar access, and hence usage patterns in open spaces. However, the relationship between tree planting and open space characteristics such as typology, proportion and height-to-width ratio in terms of shading and solar access was rarely investigated. On the other hand, there has been an increasing number of studies on using parametric tools to design urban environment recently. Despite the success in urban fabric planning by parametric tools, the utilization of these tools to design open spaces with a relatively smaller scale has not been revealed. Even worse, parameters that should be included in a parametric design tool for open space planning are still unknown. Accordingly, the primary objective of this study is to, by investigating the design characteristics and concepts of different open spaces, identify parameters for a parametric tool to design green open spaces. Specifically, the possibility of using shaded areas projected by trees and surrounding buildings as one of the parameters will be revealed. The study also aims at examining how the height-to-width ratios, proportions and typologies of open spaces will affect tree planting positions when optimizing shading or solar access of the spaces in different climate zones. Results from this study will provide designers with an additional layer of information when designing open spaces.

Pressure Drop and Convective Heat Transfer in Different SiSiC Structures Fabricated by Indirect Additive Manufacturing

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Ehsan Rezaei ◽  
Maurizio Barbato ◽  
Sandro Gianella ◽  
Alberto Ortona ◽  
Sophia Haussener
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Three Dimensional ◽  
Ceramic Foam ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Surface Areas ◽  
Averaged Model

Abstract The microstructure of porous materials has a significant effect on their transport properties. Engineered cellular ceramics can be designed to exhibit properties at will, thanks to the advances in additive manufacturing. We investigated the heat and mass transport characteristics of SiSiC lattices produced by three-dimensional (3D) printing and replication, with three different morphologies: rotated cube (RC), Weaire–Phelan (WPh), and tetrakaidecahedron (TK) lattices, and a commercially available ceramic foam. The pressure gradients were measured experimentally for various velocities. The convective heat transfer coefficients were determined through a steady-state experimental technique in combination with numerical analysis. The numerical model was a volume-averaged model based on a local thermal nonequilibrium (LTNE) assumption of the two homogeneous phases. The results showed that for TK and WPh structures, undesirable manufacturing anomalies (specifically window clogging) led to unexpectedly higher pressure drops across the samples and increased thermal dispersion. Compared to the TK and WPh structures the manufactured RC lattice and the random foam had lower heat transfer rates but also lower pressure drops. These lower values for the RC lattice and foam are also a result of their lower specific surface areas.

Three-Dimensional Stress Analysis and Configuration Optimization of Cross Wavy Primary Surface Recuperator for Microturbine System

2008 ◽  
Author(s):  
D. J. Zhang ◽  
M. Zeng ◽  
Q. W. Wang
Keyword(s):  
High Temperature ◽  
Stress Distribution ◽  
Stress Analysis ◽  
Parametric Design ◽  
Minimum Principle ◽  
High Stress ◽  
Three Dimensional ◽  
Automatic Generation ◽  
Temperature And Pressure ◽  
Air Passage

Recuperator in a microturbine system, which has to work under a high temperature and high pressure condition, is a key component to improve the electricity efficiency of the system. High temperature and pressure may cause high stress inside the Cross-Wavy Primary Surface (CWPS) sheet, and it is essential to analyze the stress distribution to ensure the security while the recuperator is working. In this paper the combined thermomechanical design of a CWPS recuperator for a 100kW microturbine system is presented. With the ANSYS Parametric Design Language (APDL), calculation procedures for heat transfer and stress analysis are combined in order to perform a reliable strength prediction of the recuperator. A program has been generated, which allows the automatic generation of the numerical model, the mesh and the boundary conditions. Also with the energy minimum principle, an optimal configuration of the air and gas passages is obtained. The results show that the material of the primary sheet (0Cr18Ni11Nb) is reliable. The stress distribution changes with the different configuration of the passages. Since the air pressure is much higher than that of the exhaust gas, the configuration of the primary sheet is much better when the sectional area of the gas passage is larger than that of the air passage. If the pitch of the sheet is maintained at 2mm, the best configuration is obtained when the dimension of passage is at r = 0.35–0.42mm, R = 0.55–0.48mm.

Mixed Convection of Impinging Air Cooling Over Heat Sink in Telecom System Application

2004 ◽  
Vol 126 (4) ◽  
pp. 519-523 ◽  
Author(s):  
Siddharth Bhopte ◽  
Musa S. Alshuqairi ◽  
Dereje Agonafer ◽  
Gamal Refai-Ahmed
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Mixed Convection ◽  
Heat Sink ◽  
Three Dimensional ◽  
Source Surface ◽  
Air Cooling ◽  
Transfer Rates ◽  
Nusselt Numbers ◽  
Air Jet

The current numerical investigation will examine the effect of an impinging mixed convection air jet on the heat transfer rate of a parallel flat plate heat sink. A three-dimensional numerical model was developed to evaluate the effects of the nozzle diameter d, nozzle-to-target vertical placement H/d, Rayleigh number, and the jet Reynolds number on the heat transfer rates from a discrete heat source. Simulations were performed for a Prandtl number of 0.7 and for Reynolds numbers ranging from 100 to 5000. The governing equations were solved in the dimensionless form using a commercial finite-volume package. Average Nusselt numbers were obtained, at H/d=3 and two jet diameters, for the bare heat source, for the heat source with a base heat sink, and for the heat source with the finned heat sink. The heat transfer rates from the bare heat source surface have been compared with the ones obtained with the heat sink in order to determine the overall performance of the heat sink in an impingement configuration.

Numerical Analysis of Blockage and Optimization of Heat Transfer Performance of Fractal-like Microchannel Nets

2005 ◽  
Vol 128 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Xiang-Qi Wang ◽  
Arun S. Mujumdar ◽  
Christopher Yap
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Flow Resistance ◽  
Heat Transfer Performance ◽  
Three Dimensional ◽  
Constant Heat Flux ◽  
Low Flow ◽  
Flow And Heat Transfer ◽  
Computational Fluid Dynamics Cfd ◽  
Number Of Branches

The conjugate fluid flow and heat transfer characteristics of fractal-like microchannel nets embedded in a disk-shape heat sink are investigated using a three-dimensional computational fluid dynamics (CFD) approach. A constant heat flux is applied to the top wall of the heat sink. The intrinsic advantages of fractal-like microchannel nets such as low flow resistance, temperature uniformity, and reduced danger of blockage compared with the traditional parallel channel nets are demonstrated. In addition, various optimized designs with parameters such as the number of branches, number of branching levels, and number of channels that reach the center of the disk are addressed in this context.

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