Natural Convection From Finned Heat Sinks

2007 ◽  
Author(s):  
L. T. Yeh ◽  
Joseph Yeh ◽  
B. T. F. Chung
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Plate Thickness ◽  
Heat Sinks ◽  
Cfd Model ◽  
Practical Applications ◽  
Computational Fluid Dynamics Analysis ◽  
Fin Spacing ◽  
Fin Length

A CFD (computational fluid dynamics) analysis is performed on the finned heat sinks. For convenience, a commercial CFD code, Flotherm, is utilized in the analysis. Though the code can handle the radiation heat transfer, the present analysis is limited to the natural convection with the base of the heat sink at a constant temperature. The continuous fin configuration is first considered due to the importance of its applications. Several experimental data are available for the vertically straight-fin heat sink and a useful correlation is also developed. For given overall fin dimensions of 15″ × 10.341″ × 2.2″, the correlations are first employed to determine the optimal fin spacing. This optimal fin spacing of 0.439 in is then used to develop the baseline CFD model. The dimensions of the baseline CFD model are as follows: Fin width (in): 10.341. Heat sink length (in): 15. Fin spacing (in): 0.439. Fin height (in): 2.0. Fin thickness (in): 0.1. Fin base plate thickness (in): 0.2. Fin numbers: 20. The baseline model with various fin spacing is analyzed and the results (heat loss from the finned heat sink) compare well with those obtained through the correlations. The analysis is extended to the staggered and in-line fin configurations because of their practical applications. Three different fin lengths, including 1″, 3″ and 5″ fin length for the staggered fin array are examined. The results indicate that the effectiveness of heat transfer is increased as the fin length increasing. The continuous fin configuration is the most efficient, and is followed by the staggered fins and then by the in-line fins.

A Review On Rectangular Heat Sinks Under Natural Convection

2019 ◽  
Vol 118 (7) ◽  
pp. 44-49
Author(s):  
Rajshekhar V Unni ◽  
Vijay S Majali
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Ambient Temperature ◽  
Temperature Difference ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Cost Effective ◽  
Heat Sinks ◽  
Maximum Heat ◽  
Fin Spacing

In the paper review of studies of heat sinks under natural convection is taken up. The discussions are mainly on experimental works carried out on rectangular fin arrays, optimization of heat sink dimensions and heat transfer enhancement. The geometries of heat sinks, fin spacing, fin height, fin length, fin thickness and fin material and base to ambient temperature difference are the important parameters on which heat transfer rate depends. So the design and optimization of the heat sink geometries becomes essential. It was found that the optimum fin  spacing is ranging from 6.1- 11.9mm which gives maximum heat dissipation; the base to ambient temperature difference is 20-1500C. During most of the experimental work carried out a good thermal conductivity material which is cost-effective was chosen.

Thermally Optimum Natural Convection Cooled Longitudinal-Plate Heat Sinks With Horizontal Base Plates

2001 ◽  
Author(s):  
K. K. Sikka ◽  
C. George
Keyword(s):  
Natural Convection ◽  
Heat Sink ◽  
Base Plate ◽  
Heat Sinks ◽  
Geometrical Parameters ◽  
Plate Heat ◽  
Horizontal Orientation ◽  
Fin Spacing ◽  
Base Plates ◽  
Weakly Dependent

Abstract Longitudinal-plate fin heat sinks are optimized under natural convection conditions for the horizontal orientation of the heat sink base plate. The thermal performance of the heat sinks is numerically modeled. The fin height, thickness and spacing and heat sink width are systematically varied. The numerical results are validated by experimentation. Results show that the thermal resistance of a heat sink minimizes for a certain number of fins on the base plate. The fin spacing-to-length ratio at which the minimum occurs is weakly dependent on the fin height and thickness and heat sink width. The flow fields reveal that the minimum occurs for the heat sink geometry in which the number of fins are maximized such that the flow velocity as the air exits the fins is fully developed. A correlation of the heat transfer with the heat sink geometrical parameters is also developed.

Partitioned Heat Sinks for Improved Natural Convection

2020 ◽  
Author(s):  
Todd Salamon ◽  
Roger Kempers ◽  
Brian Lynch ◽  
Kevin Terrell ◽  
Elina Simon
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Convective Heat Transfer ◽  
Antenna Arrays ◽  
Heat Sink ◽  
Massive Mimo ◽  
Vertical Plate ◽  
Numerical Models ◽  
Heat Sinks ◽  
Sensible Heat

Abstract The main drivers contributing to the continued growth of network traffic include video, mobile broadband and machine-to-machine communication (Internet of Things, cloud computing, etc.). Two primary technologies that next-generation (5G) networks are using to increase capacity to meet these future demands are massive MIMO (Multi-Input Multi-Output) antenna arrays and new frequency spectrum. The massive MIMO antenna arrays have significant thermal challenges due to the presence of large arrays of active antenna elements coupled with a reliance on natural convection cooling using vertical plate-finned heat sinks. The geometry of vertical plate-finned heat sinks can be optimized (for example, by choosing the fin pitch and thickness that minimize the thermal resistance of the heat sink to ambient air) and enhanced (for example, by embedding heat pipes within the base to improve heat spreading) to improve convective heat transfer. However, heat transfer performance often suffers as the sensible heat rise of the air flowing through the heat sink can be significant, particularly near the top of the heat sink; this issue can be especially problematic for the relatively large or high-aspect-ratio heat sinks associated with massive MIMO arrays. In this study a vertical plate-finned natural convection heat sink was modified by partitioning the heat sink along its length into distinct sections, where each partitioned section ejects heated air and entrains cooler air. This approach increases overall heat sink effectiveness as the net sensible heat rise of the air in any partitioned section is less than that observed in the unpartitioned heat sink. Experiments were performed using a standard heat sink and equivalent heat sinks partitioned into two and three sections for the cases of ducted and un-ducted natural convection with a uniform heat load applied to the rear of the heat sink. Numerical models were developed which compare well to the experimental results and observed trends. The numerical models also provide additional insight regarding the airflow and thermal performance of the partitioned heat sinks. The combined experimental and numerical results show that for relatively tall natural convection cooled heat sinks, the partitioning approach significantly improves convective heat transfer and overall heat sink effectiveness.

Performance Prediction for Partially-Confined Heat Sinks

2003 ◽  
Author(s):  
Tzer-Ming Jeng ◽  
Meng-Ping Wang ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Velocity ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Thermal Conductance ◽  
Optimal Number ◽  
Performance Parameter ◽  
Heat Sinks ◽  
Fin Spacing

In the present study, the forced air convection heat transfer for unconfined and confined heat sinks by considering flow bypass effect is studied on a semi-empirical basis. The flow bypass effect for unconfined heat sinks is firstly investigated. For unconfined heat sinks with specified fin spacing and fin height, the results reveal that the value of Ui/(ε·Us), which represents the flow bypass capability, increases from a very small Reynolds number up to a certain Reynolds number, say Rei = 60–200; and then gradually decrease with further increasing Reynolds number. At a specified Reynolds number, the Ui/(ε·Us) will generally increase when the fin spacing decreases or the fin height increases. For heat sinks partially confined in a channel, a novel concept to estimate an imaginative flow domain, in which the flow is influenced due to the existence of heat sink in the channel, is postulated in the study. Accordingly, an effective method for predicting the flow velocity between fins, flow rate through the heat sink and the fin heat transfer coefficient in both unconfined flow and confined flow is presented. Finally, in order to explore the optimal number of fins, a performance parameter defined as the ratio of thermal conductance to the required pumping power is introduced; an optimal procedure to determine the maximum performance parameter for a heat sink partially confined in a channel is postulated. The results manifest that the optimal number of fins increases with increasing inlet flow velocity.

Effect of Synthetic Jets Over Natural Convection Heat Sinks

2008 ◽  
Author(s):  
Mehmet Arik ◽  
Yogen Utturkar ◽  
Murat Ozmusul
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Operating Conditions ◽  
Heat Sinks ◽  
Junction Temperature ◽  
Allowable Limit

In moderate power electronics applications, the most preferred way of thermal management is natural convection to air with or without heat sinks. Though the use of heat sinks is fairly adequate for modest heat dissipation needs, it suffers from some serious performance limitations. Firstly, a large volume of the heat sink is required to keep the junction temperature at an allowable limit. This need arises because of the low convective film coefficients due to close spacing. In the present computational and experimental study, we propose a synthetic jet embedded heat sink to enhance the performance levels beyond two times within the same volume of a regular passive heat sink. Synthetic jets are meso-scale devices producing high velocity periodic jet streams at high velocities. As a result, by carefully positioning of these jets in the thermal real estate, the heat transfer over the surfaces can be dramatically augmented. This increase in the heat transfer rate is able to compensate for the loss of fin area happening due to the embedding of the jet within the heat sink volume, thus causing an overall increase in the heat dissipation. Heat transfer enhancements of 2.2 times over baseline natural convection cooled heat sinks are measured. Thermal resistances are compared for a range of jet operating conditions and found to be less than 0.9 K/W. Local temperatures obtained from experimental and computational agreed within ± 5%.

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.

Natural and forced convection heat transfer coefficients of various finned heat sinks for miniature electronic systems

2018 ◽  
Vol 233 (2) ◽  
pp. 249-261 ◽  
Author(s):  
SW Pua ◽  
KS Ong ◽  
KC Lai ◽  
MS Naghavi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Convection Heat Transfer ◽  
Heat Sinks ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Cooling Mode ◽  
Heat Transfer Coefficients ◽  
Experimental Heat

Downward lighting light-emitting diodes require cooling with cylindrical fin heat sinks to be mounted on top and cooled under natural convection air cooling mode. Performance simulation would involve specification of the heat transfer coefficient. Numerous methods are available to simulate the performance of conventional plate fin heat sinks including computational fluid dynamics packages. It would be feasible to perform simulation based on conventional flat plate fin heat sinks. A cylindrical fin heat sinks could be simply treated as a plate fin heat sink, if we imagine it cut open and laid out horizontally. A theoretical model is proposed in this paper. An experimental investigation is conducted here to validate its accuracy. Convective heat transfer coefficients were experimentally determined for a horizontally and vertically inclined bare plate operating under natural and forced air cooling modes. In addition, a vertical plate fin heat sink and a vertical cylindrical fin heat sink under natural convection were investigated. Power inputs were kept from 5 to 40 W in order to keep operating temperatures below 100 ℃. Comparison of the experimental heat transfer coefficients and those obtained from well-known existing Nusselt number correlations show that agreement was poor for the bare plate but satisfactory for the plate and cylindrical fin heat sinks. Although they are within the generally accepted range, it would be advisable for actual measurements to be carried out in order to provide more accurate sizing for thermal measurements.

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.

Natural Convection Heat Transfer From Horizontal Rectangular Inverted Notched Fin Arrays

2009 ◽  
Vol 131 (8) ◽  
Author(s):  
Sanjeev D. Suryawanshi ◽  
Narayan K. Sane
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Dissipation ◽  
Convection Heat Transfer ◽  
Average Heat Transfer Coefficient ◽  
Enhancement Of Heat Transfer ◽  
Computational Fluid Dynamics Analysis ◽  
Convection Cooling ◽  
Fin Spacing ◽  
Bottom Portion

The variables for natural convection cooling with the help of finned surfaces are orientation and geometry. In lengthwise short array (L/H∼5), where single chimney flow pattern is present, a stagnant zone is created at the central bottom portion of fin array channel and hence it does not contribute much in heat dissipation. Hence it is removed in the form of inverted notch at the central bottom portion of fin to modify its geometry for enhancement of heat transfer. An experimental setup is developed for studying the investigation on normal and inverted notched fin arrays (INFAs). Fin spacing, heater input, and percentage of area removed in the form of inverted notch are the parameters. For few spacing, it is verified by computational fluid dynamics analysis (Course Notes on Introduction to Commercial CFD of Tridiagonal Solutions, Pune), and the results are well matching. It is found that the average heat transfer coefficient for INFAs is nearly 30–40% higher as compared with normal array.

scholarly journals EXPERIMENTAL ANALYSIS OF THE INFLUENCE OF HEAT SINK GEOMETRIC PARAMETERS ON NATURAL CONVECTION

2016 ◽  
Vol 15 (1) ◽  
pp. 26
Author(s):  
V. A. Silva ◽  
B. C. S. Anselmo ◽  
A. L. F. L. Silva ◽  
S. M. M. L. Silva
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Optimal Number ◽  
Geometric Parameters ◽  
Heat Sinks ◽  
Temperature Range ◽  
Steady State Heat ◽  
Steady State Heat Transfer ◽  
Heat Transfer By Radiation

In this work, the steady state heat transfer by natural convection in heat sinks with rectangular fins positioned vertically and horizontally was studied. The heat transfer by radiation was also considered. Several analyses were performed to determine the optimal number and position of the sensors used to measure the temperature on the heat sinks horizontally and vertically positioned. These analyses confirmed an almost uniform temperature distribution in the heat sink. This uniformity allowed the use of thermocouples only in the center of the heat sink. Twelve heat sinks were designed to study how their geometric parameters such as height, spacing and thickness of the fins, influence the heat transfer by free convection. In addition, in this work, two correlations using the dimensionless parameters Nusselt and Rayleigh are proposed. These correlations were obtained by using the results from the 12 heat sinks vertically and horizontally positioned considering a temperature range between 20 °C and 100 °C. Furthermore, studies were done to identify which of the 12 analyzed heat sinks managed to remove the greatest amount of heat in a given temperature range. The results were compared with those obtained from empirical correlations found in literature.

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