An Experimental Study of Pin Fin Heat Sinks and Determination of End Wall Heat Transfer

An experimental study of a pin fin heat sink was carried out in support of the development of heat sink optimization methods requiring more detailed measurements be made. Measurements of heat flux and temperature are used to separately determine heat transfer coefficients for the pins and the base region between the pins. Three pitch to diameter ratios (distance from pin center to pin center measured diagonally) were studied: P/d = 3/1, 9/4, 3/2. Heat generation was accomplished using cartridge heaters inserted into a copper block. The high thermal conductivity of the copper ensured that the surface beneath the heat sink would be at a constant temperature. The cooling fluid was air and the experiments were conducted with a Reynolds numbers based on a porous media type hydraulic diameter ranging from 500 to 25000. The channel had a shroud that touches the fin tips, eliminating any flow bypass. The pin surface heat transfer coefficients match the values reported by Kays and London and by Zukauskas. The base region heat transfer coefficients were, surprisngly, larger than the pin values.

Volume 3: Gas Turbine Heat Transfer; Transport Phenomena in Materials Processing and Manufacturing; Heat Transfer in Electronic Equipment; Symposium in Honor of Professor Richard Goldstein; Symposium in Honor of Prof. Spalding; Symposium in Honor of Prof. Arthur E. Bergles ◽

Cryogenic Single-Phase Heat Transfer in a Microscale Pin Fin Heat Sink

10.1115/ht2013-17660 ◽

2013 ◽

Author(s):

Eric D. Truong ◽

Erfan Rasouli ◽

Vinod Narayanan

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Heat Sink ◽

Single Phase ◽

Flow Direction ◽

Heat Sinks ◽

Variable Cross ◽

Transfer Coefficients ◽

Pin Fin ◽

A combined experimental and computational fluid dynamics study of single-phase liquid nitrogen flow through a microscale pin-fin heat sink is presented. Such cryogenic heat sinks find use in applications such as high performance computing and spacecraft thermal management. A circular pin fin heat sink in diameter 5 cm and 250 micrometers in depth was studied herein. Unique features of the heat sink included its variable cross sectional area in the flow direction, variable pin diameters, as well as a circumferential distribution of fluid into the pin fin region. The stainless steel heat sink was fabricated using chemical etching and diffusion bonding. Experimental results indicate that the heat transfer coefficients were relatively unchanged around 2600 W/m2-K for flow rates ranging from 2–4 g/s while the pressure drop increased monotonically with the flow rate. None of the existing correlations in literature on cross flow over a tube bank or micro pin fin heat sinks were able to predict the experimental pressure drop and heat transfer characteristics. However, three dimensional simulations performed using ANSYS Fluent showed reasonable (∼7 percent difference) agreement in the average heat transfer coefficients between experiments and CFD simulations.

A Study of Forced Convection Direct Air Cooling in the Downstream Vicinity of Heat Sinks

Journal of Electronic Packaging ◽

10.1115/1.2904372 ◽

1990 ◽

Vol 112 (3) ◽

pp. 234-240 ◽

Cited By ~ 5

Author(s):

G. L. Lehmann ◽

S. J. Kosteva

Keyword(s):

Heat Transfer ◽

Forced Convection ◽

Heat Sink ◽

Convection Heat Transfer ◽

Heat Sinks ◽

Air Cooling ◽

Transfer Coefficients ◽

Packaging System ◽

Transfer Rates ◽

An experimental study of forced convection heat transfer is reported. Direct air cooling of an electronics packaging system is modeled by a channel flow, with an array of uniformly sized and spaced elements attached to one channel wall. The presence of a single or complete row of longitudinally finned heat sinks creates a modified flow pattern. Convective heat transfer rates at downstream positions are measured and compared to that of a plain array (no heat sinks). Heat transfer rates are described in terms of adiabatic heat transfer coefficients and thermal wake functions. Empirical correlations are presented for both variations in Reynolds number (5000 < Re < 20,000) and heat sink geometry. It is found that the presence of a heat sink can both enhance and degrade the heat transfer coefficient at downstream locations, depending on the relative position.

Heat Transfer From a Finned Surface in Ducted Air Jet Suction and Impingement

Journal of Electronic Packaging ◽

10.1115/1.1286106 ◽

1999 ◽

Vol 122 (3) ◽

pp. 282-285 ◽

Cited By ~ 2

Author(s):

Luis A. Brignoni ◽

Suresh V. Garimella

Keyword(s):

Heat Transfer ◽

Heat Sink ◽

Jet Impingement ◽

Target Distance ◽

Transfer Coefficients ◽

Pin Fin ◽

Air Jet ◽

Finned Surface ◽

Different Diameters

Experimental measurements were obtained to characterize the thermal performance of ducted air suction in conjunction with a pin-fin heat sink. Four single nozzles of different diameters and two multiple-nozzle arrays were studied at a fixed nozzle-to-target distance, for different turbulent Reynolds numbers 5000⩽Re⩽20,000. Variations of nozzle-to-target distance, i.e., open area, in ducted suction were found to have a strong effect on heat transfer especially with the larger diameter single nozzle and both multiple-nozzle arrays. Enhancement factors were computed with the heat sink in suction flow, relative to a bare surface, and were in the range of 8.3 to 17.7, with the largest value being obtained for the nine-nozzle array. Results from the present study on air jet suction are compared with previous experiments with air jet impingement on the pin-fin heat sink. Average heat transfer coefficients and thermal resistance values are reported for the heat sink as a function of Reynolds number, air flow rate, and pumping power. [S1043-7398(00)00903-8]

A Novel Concept to Improve the Performance of LED Panel Using Drilled Holes

Heat Transfer, Part A ◽

10.1115/imece2005-82627 ◽

2005 ◽

Author(s):

S. B. Chiang ◽

C. C. Wang

Keyword(s):

Heat Transfer ◽

Surface Area ◽

Heat Sink ◽

Maximum Temperature ◽

Transfer Coefficients ◽

Pin Fin ◽

Pin Fins ◽

Overall Performance ◽

Novel Concept

In this study, the concept of the thermal module of LEDs cooling by use of drilled hole to entrain air flow was examined. It is found that the drilled hole does not necessarily improve the overall performance. It depends on the size of the drilled hole, the number of drilled holes, and the locations. The heat transfer coefficients are generally increased with the number of drilled holes and the diameter of the drilled hole. In this paper, the plate fin heat sink has a higher heat transfer coefficients than pin fins, but the overall performance of the LED panel having pin fin outperforms that of plate fin. This is because the pin fin provides much larger surface area. For decrease the maximum temperature of the LED panel, placement of the drilled holes along the hot region will be more effective.

Experiments and Modeling of the Heat Transfer of In-Line Square Pin Fin Heat Sinks With Top By-Pass Flow

Heat Transfer, Volume 7 ◽

10.1115/imece2002-39245 ◽

2002 ◽

Cited By ~ 1

Author(s):

M. Baris Dogruoz ◽

Mario Urdaneta ◽

Alfonso Ortega

Keyword(s):

Heat Transfer ◽

Experimental Results ◽

Heat Sinks ◽

Transfer Coefficients ◽

Clearance Ratio ◽

One Dimensional ◽

Pin Fin ◽

Approach Velocity ◽

Good Agreement

This paper presents experimental results on the heat transfer characteristics of in-line square pin fin heat sinks with and without top by-pass. A self-consistent set of aluminum heat sinks were utilized, where the pin height was varied from 12.5 mm to 22.5 mm, the pin pitch was varied from 3.4 mm to 5.8 mm and the base dimensions were kept fixed at 25 × 25 mm. The overall base to ambient thermal resistance was measured as a function of Reynolds number and bypass height. Experimental results were then compared with predictions based on a simple one-dimensional “two-branch by-pass model”. Comparisons were made with the data using heat transfer coefficients available in the literature for infinitely long tube bundles. It was shown that there is a good agreement between the temperature predictions based on the model and the experimental data at high approach velocities for tall heat sinks, however the discrepancy between the computations and experiments increases as the approach velocity and heat sink height decrease. The validated model was used to identify optimum pin spacing as a function of clearance ratio.

Detailed Measurements of End-Wall Heat Transfer Coefficients of Square Pin-Fin Heat Sink for LED Lamp at Forced Convective State

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.697 ◽

2013 ◽

Vol 284-287 ◽

pp. 697-701

Author(s):

Tzer Ming Jeng ◽

Sheng Chung Tzeng

Keyword(s):

Heat Transfer ◽

Heat Sink ◽

Rectangular Channel ◽

Wall Heat Transfer ◽

Transfer Coefficients ◽

Wall Area ◽

Pin Fin ◽

Convective State ◽

End Wall

The device made of fan and pin-fin heat sink should be a powerful heat sink for LED lamp. This study used transient liquid crystal experimentation to measure the end-wall heat transfer coefficient of linearly arrayed square pin array in the rectangular channel, and discussed the influence of axial spacing on heat transfer. The air was used as operating fluid, and the square pin size was 8 mm (d) × 8 mm (d) × 64 mm (Hf), arrayed in a 240 mm (L) × 120 mm (W) × 64 mm (H) rectangular channel. The relative lateral spacing (XT=ST/d) was set as 3, and the relative axial spacing (XL=SL/d=1.88~5) and the Reynolds number (Re=11047~17937) were changed. Considering the end-wall area, the average Nusselt number with square pin was 1.46~2.58 times of that without square pin, and the square pin array of XL= 3.75 had the maximum end-wall heat transfer gain.

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

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

10.1177/0957650918784420 ◽

2018 ◽

Vol 233 (2) ◽

pp. 249-261 ◽

Cited By ~ 4

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 ◽

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.

Experimental Study of Single-Phase Heat Transfer in Circular Milli-Channels for Cooling of Micro Components

Advanced Energy Systems ◽

10.1115/imece2005-82438 ◽

2005 ◽

Author(s):

Antonio Ramos ◽

Antonio J. Bula ◽

Maria Cely

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Single Phase ◽

Flow Direction ◽

Heat Sinks ◽

Rectangular Plates ◽

Transfer Coefficients ◽

Channel Diameter ◽

Experimental Process

The increase of processing speed in applications such as servers, laptops and workstations requires heat-sinking technologies with higher levels of power dissipation than the current methods. For this reason, this paper presents an experimental study of heat transfer in water-cooled milli - channel heat sinks. The experimental process consists of fabrication and testing of rectangular plates with multiple parallel channels oriented in the flow direction. Variations in the number of channels, channel diameter, and volumetric flow were considered in order to study the conjugate heat transfer phenomena. Overall heat transfer coefficients in single-phase flow regimes are presented and analyzed.

Enhanced Microchannel Heat Sinks Using Oblique Fins

ASME 2009 InterPACK Conference, Volume 2 ◽

10.1115/interpack2009-89059 ◽

2009 ◽

Cited By ~ 17

Author(s):

Yong-Jiun Lee ◽

Poh-Seng Lee ◽

Siaw-Kiang Chou

Keyword(s):

Heat Transfer ◽

Heat Sink ◽

Leading Edge ◽

Local Heat Transfer ◽

Local Heat ◽

Secondary Flows ◽

Heat Sinks ◽

Microchannel Heat Sink ◽

Transfer Coefficients ◽

Oblique fins created in a microchannel heat sink can serve to modulate the flow, resulting in local and global heat transfer enhancement. Numerical analysis of laminar flow and heat transfer in such modified microchannel heat sink showed that significant enhancement of heat transfer can be achieved with negligible pressure drop penalty. The breakage of continuous fin into oblique sections causes the thermal boundary layers to be re-initialized at the leading edge of each oblique fin and reduces the boundary-layer thickness. This regeneration of the entrance effect causes the flow to be always in a developing state thus resulting in better heat transfer. In addition, the presence of the smaller oblique channels causes a fraction of the flow to branch into the adjacent main channels. The secondary flows thus created improve fluid mixing which serves to further enhance the heat transfer. The combination of the entrance and secondary flow effect results in a much improved heat transfer performance (the average and local heat transfer coefficients are enhanced by as much as 80%). Both the maximum wall temperature and temperature gradient are substantially decreased as a result.