Numerical Modeling of Buoyancy Induced Convection in Finned Heat Sinks in Presence of Unheated and Heated Shrouds

2005 ◽  
Author(s):  
S. S. Bahga ◽  
A. Bhattacharya ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Sink ◽  
Numerical Study ◽  
Numerical Results ◽  
Heat Sinks ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Wide Range ◽  
The Impact

This paper investigates the effects of the presence of unheated and heated shrouds on the thermal performance of longitudinal finned heat sinks. A comprehensive numerical study was conducted to determine the impact of the shroud clearance from the tip of the fins and shroud heating. The first part of the study deals with the effects of an unheated shroud on finned heat sinks of different fin height, fin pitch and length in an attempt to cover a wide range of geometry. The numerical results reveal an optimum clearance for maximum heat transfer. For all heat sinks studied the unheated shroud improved the performance by as much as 15% until the shroud was very close when the performance decreased by as much as 10%. In the second part of the paper, the effects of heating of the shroud were considered. In these numerical runs, an isothermal boundary condition was imposed on the shroud. For the heating levels considered, it was found that heating of the shrouds can increase or lower the thermal performance of the heat sink depending on the heat sink geometry and shroud clearance. Finally, the numerical results also revealed a systematic dependence of the normalized Nusselt number on the Rayleigh number for a given heat sink geometry.

scholarly journals Numerical Study on Flow and Heat Transfer Mechanisms in the Heat Exchanger Channel with V-Orifice at Various Blockage Ratios, Gap Spacing Ratios, and Flow Directions

2019 ◽  
Vol 2019 ◽  
pp. 1-21 ◽  
Author(s):  
Amnart Boonloi ◽  
Withada Jedsadaratanachai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Numerical Results ◽  
Blockage Ratio ◽  
Maximum Heat ◽  
Flow And Heat Transfer ◽  
Maximum Heat Transfer ◽  
Smooth Channel ◽  
Gap Spacing

Numerical assessments in the square channel heat exchanger installed with various parameters of V-orifices are presented. The V-orifice is installed in the heat exchanger channel with gap spacing between the upper-lower edges of the orifice and the channel wall. The purposes of the design are to reduce the pressure loss, increase the vortex strength, and increase the turbulent mixing of the flow. The influence of the blockage ratio and V-orifice arrangement is investigated. The blockage ratio, b/H, of the V-orifice is varied in the range 0.05–0.30. The V-tip of the V-orifice pointing downstream (V-downstream) is compared with the V-tip pointing upstream (V-upstream) by both flow and heat transfer. The numerical results are reported in terms of flow visualization and heat transfer pattern in the test section. The thermal performance assessments in terms of Nusselt number, friction factor, and thermal enhancement factor are also concluded. The numerical results reveal that the maximum heat transfer enhancement is found to be around 26.13 times higher than the smooth channel, while the optimum TEF is around 3.2. The suggested gap spacing for the present configuration of the V-orifice channel is around 5–10%.

Cooling Performances of Perforated-Finned Heat Sinks

2016 ◽  
Author(s):  
Mohammad Reza Shaeri ◽  
Bradley Richard ◽  
Richard Bonner
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Cooling System ◽  
Thermal Characteristics ◽  
Heat Sinks ◽  
Pumping Power ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Cooling performances of perforated-finned heat sinks (PFHS) are investigated in the laminar forced convection heat transfer mode, through detailed experiments. Perforations like windows with square cross sections are placed on the lateral surfaces of the fins. Cooling performances are evaluated due to changes in both porosities and perforation sizes. Thermal characteristics are reported based on pumping power, in order to provide more practical insight about performances of PFHSs in real applications. It is found that at a constant perforation size, there is an optimum porosity that results in the largest heat transfer coefficient. For a fixed porosity, increasing the number of perforations (reducing the perforation size) results in an enhancement of heat transfer rate due to repeated interruption of the thermal boundary layer. The opposite trend is observed for PFHSs with larger perforation sizes. This indicates that there is an optimum perforation size and distance between perforations in order to achieve the maximum heat transfer coefficients at a constant porosity. Also, a PFHS results in a smaller temperature non-uniformity across the heat sink base, as well as a more rapid reduction in temperature non-uniformity on the heat sink base by increasing pumping power. In addition, the advantage of a PFHS to reduce the overall weight of the cooling system is incorporated into thermal characteristics of the heat sinks, and demonstrated by the mass specific heat transfer coefficient.

Enhanced Heat Transfer in Radial Heat Sinks for LED Lamps

2018 ◽  
Author(s):  
Fernando Cano-Banda ◽  
Ana Gallardo-Gutierrez ◽  
Jesus Garcia-Gonzalez ◽  
Abel Hernandez-Guerrero ◽  
Luis Luviano-Ortiz
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Heat Sinks ◽  
Output Analysis ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Longitudinal Orientation ◽  
Radial Heat

A radial design of a passive heat sink for cooling LED illumination devices is analyzed numerically in order to identify the geometric shape that promotes better heat dissipation rates. Natural convection with the surrounding is considered during the operation of the heat sink. Due to the fact that natural convection is the main mechanism of heat transfer, the shape of the heat sink has a high influence in the heat dissipated. An analysis of the influence of different parameters of a heat sink is conducted in the presented study. The radial heat sink under analysis consists in a flat disc with rectangular fins on it, and the fins are distributed with a radial longitudinal orientation in a circular row arrangement. The number of rows can vary but there is a constant relation of two times the number of fins between the number of fins in an inner row and the next outer row. In order to find a correct configuration to improve the dissipation of heat, parameters like the number of fins, the length of the fins and the separation between fins are studied. The average Nusselt number and thermal resistance for each geometric configuration are compared. The output analysis provides the best shape for a maximum heat transfer.

Flow Boiling in a Heat Sink Embedded With Hexagonally Linked Minichannels

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Shubhankar Chakraborty ◽  
Omprakash Sahu ◽  
Prasanta Kr. Das
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Flow Boiling ◽  
Heat Sinks ◽  
Vapor Quality ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
The Heat Transfer Coefficient

The thermal hydraulic performance of a miniature heat sink during flow boiling of distilled water is presented in this article. The unique design of the heat sink contains a number of microchannels of 1 mm × 1 mm cross section arranged in a regular hexagonal array. The design facilitates repeated division and joining of individual streams from different microchannels and thereby can enhance heat transfer. Individual slug bubble experiences a typical route of break up, coalescence, and growth. The randomness of these processes enhances the transport of heat. With the increase of vapor quality the heat transfer coefficient increases, reaches the maximum value, and then drops. The maximum heat transfer coefficient occurs at an exit vapor quality much higher than that observed in conventional parallel microchannel heat sinks. Repeated redistribution of the coolant in the interlinked channels and the restricted growth of the slug bubbles may be responsible for this trend.

The Effect of Thermal Contact Resistance at Porous-Solid Interfaces in Finned Metal Foam Heat Sinks

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Christopher T. DeGroot ◽  
Derek Gateman ◽  
Anthony G. Straatman
Keyword(s):  
Heat Transfer ◽  
Contact Resistance ◽  
Boundary Layers ◽  
Thermal Contact Resistance ◽  
Numerical Study ◽  
Thermal Contact ◽  
Porous Solid ◽  
Heat Sinks ◽  
Wide Range ◽  
The Impact

A numerical study on the effect of thermal contact resistance and its impact on the performance of finned aluminum foam heat sinks has been conducted. Calculations are based on the solution of the volume-averaged mass, momentum, and energy equations under conditions of local thermal nonequilibrium using a finite-volume-based computational fluid dynamics code for conjugate fluid/porous/solid domains. Numerical results have been obtained for a wide range of contact resistances at the porous-solid interfaces, up to the limit of an effectively infinite resistance. As the contact resistance is increased to such high levels, the heat transfer is found to asymptote as conduction into the solid constituent of the foam is completely blocked. Even without conduction into the solid, a convective enhancement is obtained due to the presence of the foam material. It is reasoned that this is due to the thinning of the momentum boundary layers as a result of the presence of the porous material, which acts as a momentum sink. As a result of the thinner boundary layers, the flow speed near the finned surfaces and base is increased, which serves to increase the rate of convection from these surfaces. It is also found that for most reasonable interface materials, such as thermal epoxies, the impact of thermal contact resistance on the heat transfer performance in comparison to that for an ideal bond is small.

An Investigation of the Effect of interrupted fin arrangements on the Thermal Performance of a Heat Sink under a Free Convection Condition

2019 ◽  
Vol 7 (1) ◽  
pp. 43-53
Author(s):  
Abbas Jassem Jubear ◽  
Ali Hameed Abd
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Convection ◽  
Thermal Performance ◽  
Heat Sink ◽  
Numerical Study ◽  
Ansys Fluent ◽  
Fluent Software ◽  
Steady State Heat ◽  
Steady State Heat Transfer

The heat sink with vertically rectangular interrupted fins was investigated numerically in a natural convection field, with steady-state heat transfer. A numerical study has been conducted using ANSYS Fluent software (R16.1) in order to develop a 3-D numerical model.  The dimensions of the fins are (305 mm length, 100 mm width, 17 mm height, and 9.5 mm space between fins. The number of fins used on the surface is eight. In this study, the heat input was used as follows: 20, 40, 60, 80, 100, and 120 watts. This study focused on interrupted rectangular fins with a different arrangement and angle of the fins. Results show that the addition of interruption in fins in various arrangements will improve the thermal performance of the heat sink, and through the results, a better interruption rate as an equation can be obtained.

scholarly journals Effect of liquid cooling on PCR performance with the parametric study of cross-section shapes of microchannels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yousef Alihosseini ◽  
Mohammad Reza Azaddel ◽  
Sahel Moslemi ◽  
Mehdi Mohammadi ◽  
Ali Pormohammad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Heat Sink ◽  
Evaluation Criteria ◽  
Circular Cross Section ◽  
Microchannel Heat Sink ◽  
Liquid Cooling ◽  
Maximum Heat ◽  
Maximum Heat Transfer

AbstractIn recent years, PCR-based methods as a rapid and high accurate technique in the industry and medical fields have been expanded rapidly. Where we are faced with the COVID-19 pandemic, the necessity of a rapid diagnosis has felt more than ever. In the current interdisciplinary study, we have proposed, developed, and characterized a state-of-the-art liquid cooling design to accelerate the PCR procedure. A numerical simulation approach is utilized to evaluate 15 different cross-sections of the microchannel heat sink and select the best shape to achieve this goal. Also, crucial heat sink parameters are characterized, e.g., heat transfer coefficient, pressure drop, performance evaluation criteria, and fluid flow. The achieved result showed that the circular cross-section is the most efficient shape for the microchannel heat sink, which has a maximum heat transfer enhancement of 25% compared to the square shape at the Reynolds number of 1150. In the next phase of the study, the circular cross-section microchannel is located below the PCR device to evaluate the cooling rate of the PCR. Also, the results demonstrate that it takes 16.5 s to cool saliva samples in the PCR well, which saves up to 157.5 s for the whole amplification procedure compared to the conventional air fans. Another advantage of using the microchannel heat sink is that it takes up a little space compared to other common cooling methods.

Pin-Fin Heat Sink With Horizontal Base and Blocked Edges

2008 ◽  
Author(s):  
D. Sahray ◽  
H. Shmueli ◽  
N. Segal ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Contact Resistance ◽  
Cross Section ◽  
Heat Input ◽  
Heat Sink ◽  
Numerical Study ◽  
Heat Sinks ◽  
Transfer Enhancement ◽  
Pin Fin

In the present work, horizontal-base pin fin heat sinks exposed to free convection in air are studied. They are made of aluminum, and there is no contact resistance between the base and the fins. For the same base dimensions the fin height and pitch vary. The fins have a constant square cross-section. The edges of the sink are blocked: the surrounding insulation is flush with the fin tips. The effect of fin height and pitch on the performance of the sink is studied experimentally and numerically. In the experiments, the heat sinks are heated using foil electrical heaters. The heat input is set, and temperatures of the base and fins are measured. In the corresponding numerical study, the sinks and their environment are modeled using the Fluent 6 software. The results show that heat transfer enhancement due to the fins is not monotonic. The differences between sparsely and densely populated sinks are analyzed for various fin heights. Also assessed are effects of the blocked edges as compared to the previously studied cases where the sink edges were exposed to the surroundings.

Numerical and Experimental Investigation of Heat Transfer Enhancement Using Heat Pipes for Electronic Cooling

2018 ◽  
Author(s):  
Ning Zhang ◽  
Pankaj R. Chandra ◽  
Ryan Robledo ◽  
Sree Harsha Balijepalli
Keyword(s):  
Heat Transfer ◽  
Heat Pipes ◽  
Copper Plate ◽  
Heat Sinks ◽  
Modern World ◽  
Processing Unit ◽  
Maximum Heat ◽  
Central Processing ◽  
Load Combination ◽  
Maximum Heat Transfer

Computers are crucial to nearly every endeavor in the modern world. Some computers, particularly those used in military applications, are required to endure extreme conditions with limited maintenance and few parts. Units such as these will hereafter be referred to as “rugged computers.” This series of experiments aims to produce improvements to rugged computers currently in service. Using heat pipes and finned heat sinks on an enclosed box, a computer’s Central Processing Unit (CPU) is able to reject heat without suffering contamination from unforgiving environments. A modular prototype was designed to allow for three distinct cases; a case with no heat pipes and fins, a cast with heat-pipes mounted internally with exterior fins and a case with heat-pipes extended externally with exterior fins. Each case was tested at three different heat loads, with a copper plate heated by a silicone heat strip simulating the heat load generated by a CPU. Each case/load combination was run many times to check for repeatability. The aim of this research is to discover the ideal case for maximum heat transfer from the CPU to the external environment. In addition to the experiments, numerical simulation of these modular prototypes with different designs of heat pipes were conducted in this research. Creating an accurate model for computer simulations will provide validation for the experiments and will prove useful in testing cases not represented by the modular prototype. The flow and heat transfer simulations were conducted using Autodesk CFD. The aim here is to create a model that accurately reflects the experimentally-verified results from the modular prototype’s cases and loads, thereby providing a base from whence further designs can branch off and be simulated with a fair degree of accuracy.

Parametric Analysis of a Bayonet Tube With a Special Type of Extended Surface

2010 ◽  
Author(s):  
L. Almanza-Huerta ◽  
A. Hernandez-Guerrero ◽  
M. Krarti ◽  
J. M. Luna
Keyword(s):  
Heat Transfer ◽  
Parametric Analysis ◽  
Numerical Study ◽  
Systematic Investigation ◽  
Heat Transfer Characteristics ◽  
Maximum Heat ◽  
Turbulent Transition ◽  
Maximum Heat Transfer ◽  
Internal Fluid ◽  
Extended Surface

The present paper provides a numerical study of a parametric analysis of a bayonet tube with a special type of extended surface during the laminar-turbulent transition. The working internal fluid is air. Attention is focused on the heat transfer characteristics of the tube. The results constitute a systematic investigation of the effect of the extended surface located along the annulus of the bayonet on the overall heat transfer rate. The effects of the variation of some parameters related to the extended surface aiming to attain the maximum heat transfer with the minimum pressure drop are discussed. Comparisons between designs with and without extended surface are also made.

Sign in / Sign up

Export Citation Format

Share Document