Free Convection Limits for Pin-Fin Cooling

1998 ◽  
Vol 120 (3) ◽  
pp. 633-640 ◽  
Author(s):  
T. S. Fisher ◽  
K. E. Torrance
Keyword(s):  
Analytical Solution ◽  
Free Convection ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Inviscid Flow ◽  
System Size ◽  
Total System ◽  
Pin Fin ◽  
Optimal Values

An analytical solution for a system consisting of a pin-fin heat sink and a chimney is presented. The result is applied to problems in which the size of the overall system is constrained. For a given heat dissipation and total system size, optimal values of the pin-fin diameter and heat-sink porosity are observed. The optima occur for systems with and without chimneys. The optimization is used to show that the minimum thermal resistance from a pin-fin heat sink is about two times larger than that of an idealized model based on inviscid flow.

Characteristic Study on the Optimization of Pin-Fin Micro Heat Sink

2009 ◽  
Author(s):  
T. J. John ◽  
B. Mathew ◽  
H. Hegab
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Heat Sinks ◽  
Low Flow ◽  
Pumping Power ◽  
Flow Rates ◽  
Pin Fin

The need for dissipating heat from microsystems has increased drastically in the last decade. Several methods of heat dissipation using air and liquids have been proposed by many studies, and pin-fin micro heat sinks are one among them. Researchers have developed several effective pin-fin structures for use in heat sinks, but not much effort has been taken towards the optimization of profile and dimensions of the pin-fin. In this paper the authors studied the effect of different pin-fin shapes on the thermal resistance and pressure drop in a specific micro heat-sink. Optimization subjected to two different constraints is studied in this paper. The first optimization is subjected to constant flow rate and the second one is subjected to constant pressure drop. Both optimization processes are carried out using computer simulations generated using COVENTORWARE™. Two of the best structures from each of these optimization studies are selected and further analysis is performed for optimizing their structure dimensions such as width, height and length. A section of the total micro heat-sink is modeled for the initial optimization of the pin-fin shape. The model consists of two sections, the substrate and the fluid. Six different shapes: square, circle, rectangle, triangle, oval and rhombus were analyzed in the initial optimization study. Preliminary tests were conducted using the first model described above for a flow rate of 0.6ml/min. The non dimensional overall thermal resistance of the heat sink, and the nondimensional pumping power was calculated from the results. A figure of merit (FOM) was developed using the nondimensional thermal resistance and nondimensional pumping power for each structure with different pin-fin shapes. Smaller the value of FOM better the performance of the heat sink. The study revealed that the circle and ellipse structures have the best performance and the rectangle structure had the worst performance at low flow rates. At high flow rates rectangular and square structures have the best performance.

Thermal Behaviors of Passively-Cooled Hybrid Fin Heat Sinks for Lightweight and High Performance Thermal Management

2015 ◽  
Author(s):  
Nico Setiawan Effendi ◽  
Kyoung Joon Kim
Keyword(s):  
Thermal Resistance ◽  
Heat Sink ◽  
High Performance ◽  
Heat Dissipation ◽  
Computational Study ◽  
Heat Sinks ◽  
Channel Diameter ◽  
Internal Channel ◽  
Study Results ◽  
Parametric Effects

A computational study is conducted to explore thermal performances of natural convection hybrid fin heat sinks (HF HSs). The proposed HF HSs are a hollow hybrid fin heat sink (HHF HS) and a solid hybrid fin heat sink (SHF HS). Parametric effects such as a fin spacing, an internal channel diameter, a heat dissipation on the performance of HF HSs are investigated by CFD analysis. Study results show that the thermal resistance of the HS increases while the mass-multiplied thermal resistance of the HS decreases associated with the increase of the channel diameter. The results also shows the thermal resistance of the SHF HS is 13% smaller, and the mass-multiplied thermal resistance of the HHF HS is 32% smaller compared with the pin fin heat sink (PF HS). These interesting results are mainly due to integrated effects of the mass-reduction, the surface area enhancement, and the heat pumping via the internal channel. Such better performances of HF HSs show the feasibility of alternatives to the conventional PF HS especially for passive cooling of LED lighting modules.

Effect of Heat Sink Structure Improvement on Heat Dissipation Performance in High Heat Flux

2016 ◽  
Author(s):  
Zhuo Cui
Keyword(s):  
Heat Resistance ◽  
Water Flow ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Convection Heat Transfer ◽  
Cooling Water ◽  
High Heat Flux ◽  
Pin Fin ◽  
Pin Fins ◽  
Pin Fin Arrays

This paper presents the effects of heat dissipation performance of pin fins with different heat sink structures. The heat dissipation performance of two types of pin fin arrays heat sink are compared through measuring their heat resistance and the average Nusselt number in different cooling water flow. The temperature of cpu chip is monitored to determine the temperature is in the normal range of working temperature. The cooling water flow is in the range of 0.02L/s to 0.15L/s. It’s found that the increase of pin fins in the corner region effectively reduce the temperature of heat sink and cpu chip. The new type of pin fin arrays increase convection heat transfer coefficient and reduce heat resistance of heat sink.

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.

The Effect of Orientation on the Performance of Small Free-Convection Heat Sinks for Use With a Thermoelectric Cryotherapy Device

2020 ◽  
Vol 13 (4) ◽  
Author(s):  
Mark Baldry ◽  
Victoria Timchenko ◽  
Chris Menictas
Keyword(s):  
Free Convection ◽  
Heat Sink ◽  
Rapid Development ◽  
Heat Sinks ◽  
Convection Heat ◽  
Pin Fin ◽  
Flat Base ◽  
Free Convection Heat ◽  
Performance Decline ◽  
Metal 3D Printing

Abstract The rapid development of metal 3D printing techniques has enabled the exploration of complex free-convection heat sink designs. Small free-convection heat sinks with pin-fin arrays (or novel geometries) are widely employed at different orientations in a variety of electronic devices, yet there is limited understanding of how orientation impacts their heat transfer behavior. This article characterizes the orientation-dependent performance of a small, tapered pin, free-convection heat sink (named HS17) manufactured with direct metal laser sintering for use with a thermoelectric scalp cryotherapy device for the prevention of chemotherapy-induced alopecia. A validated numerical model and custom-built free-convection test rig were used to investigate the heat sink’s performance over the orientation range of 0 deg to 135 deg. HS17 maintained relatively robust performance over the 0 deg to 90 deg range; however, the thermal resistance (Rth) at 112.5 deg and 135 deg was 6% and 11% higher compared to the 90 deg case, respectively. The heat sink design was modified to include a 22.5 deg wedge base (named HS17-W) to mitigate this performance decline, which is important to ensure safe and continued operation of the cryotherapy device. Compared to the flat base heat sink, the wedge-base design successfully reduced Rth from 11.9 K/W, 12.5 K/W, and 12.8 K/W to 11.5 K/W, 11.8 K/W, and 12.3 K/W at 90 deg, 112.5 deg, and 135 deg, respectively. These results demonstrate the effectiveness of the current proposed design to improve the performance of free-convection heat sinks at downward-facing orientations.

Chip Level Refrigeration of Portable Electronic Equipment Using Thermoelectric Devices

2003 ◽  
Author(s):  
Gary L. Solbrekken ◽  
Kazuaki Yazawa ◽  
Avram Bar-Cohen
Keyword(s):  
Thermal Resistance ◽  
Heat Sink ◽  
High Performance ◽  
Heat Dissipation ◽  
Electronic Equipment ◽  
Interfacial Thermal Resistance ◽  
Maximum Heat ◽  
Power Efficient ◽  
System Sensitivity ◽  
Heat Pumping

It is well established that the power dissipation for electronic components is increasing. At the same time, high performance portable equipment with volume, weight, and power limitations are gaining widespread acceptance in the marketplace. The combination of the above conditions requires thermal solutions that are high performance and yet small, light, and power efficient. This paper explores the possibility of using thermoelectric (TE) refrigeration as an integrated solution for portable electronic equipment accounting for heat sink and interface material thermal resistances. The current study shows that TE refrigeration can indeed have a benefit over using just a heat sink. Performance maps illustrating where TE refrigeration offers an advantage over an air-cooled heat sink are created for a parametric range of CPU heat flows, heat sink thermal resistances, and TE material properties. During the course of the study, it was found that setting the TE operating current based on minimizing the CPU temperature (Tj), as opposed to maximizing the amount of heat pumping, significantly reduces Tj. For the baseline case studied, a reduction of 20–30°C was demonstrated over a range of CPU heat dissipation. The parametric studies also illustrate that management of the heat sink thermal resistance appears to be more critical than the CPU/TE interfacial thermal resistance. However, setting the TE current based on a minimum Tj as opposed to maximum heat pumping reduces the system sensitivity to the heat sink thermal resistance.

Design and Tests of a Water-Cooling Micro-Channel Heat Sink Made by WEDM

2012 ◽  
Vol 459 ◽  
pp. 609-614
Author(s):  
Kuo Zoo Liang ◽  
A Cheng Wang ◽  
Chun Ho Liu ◽  
Lung Tasi ◽  
Yan Cherng Lin
Keyword(s):  
Thermal Resistance ◽  
Heat Sink ◽  
Electrical Discharge ◽  
Heat Dissipation ◽  
Electrical Discharge Machining ◽  
Input Power ◽  
Wire Electrical Discharge Machining ◽  
Micro Channel ◽  
Water Cooling ◽  
Computer Aided

The purpose of this research is to design a new heat sink of water-cooling. With the aid of CAE (computer aided engineering), WEDM (wire electrical discharge machining), and the concept of micro-channel design, a heat sink of water-cooling can then be built with the merit of a smaller volume and lower thermal resistance. From this paper, results of the experiment indicate that the thermal resistance of heat sink can be decreased to 0.12 °C/W with input power of 60W, flow rate of 0.6 LPM, and a better heat dissipation with the in input power of 100W or 140W can be revealed.

S-Shaped Pin-Fins for Enhancement of Overall Performance of the Pin-Fin Heat Sink

2010 ◽  
Author(s):  
T. J. John ◽  
B. Mathew ◽  
H. Hegab
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heat Sink ◽  
Heat Sinks ◽  
Uniform Heat Flux ◽  
Pumping Power ◽  
Pin Fin ◽  
Pin Fins ◽  
Overall Performance

In this paper the authors are studying the effect of introducing S-shaped pin-fin structures in a micro pin-fin heat sink to enhance the overall thermal performance of the heat sinks. For the purpose of evaluating the overall thermal performance of the heat sink a figure of merit (FOM) term comprising both thermal resistance and pumping power is introduced in this paper. An optimization study of the overall performance based on the pitch distance of the pin-fin structures both in the axial and the transverse direction, and based on the curvature at the ends of S-shape fins is also carried out in this paper. The value of the Reynolds number of liquid flow at the entrance of the heat sink is kept constant for the optimization purpose and the study is carried out over a range of Reynolds number from 50 to 500. All the optimization processes are carried out using computational fluid dynamics software CoventorWARE™. The models generated for the study consists of two sections, the substrate (silicon) and the fluid (water at 278K). The pin fins are 150 micrometers tall and the total structure is 500 micrometer thick and a uniform heat flux of 500KW is applied to the base of the model. The non dimensional thermal resistance and nondimensional pumping power calculated from the results is used in determining the FOM term. The study proved the superiority of the S-shaped pin-fin heat sinks over the conventional pin-fin heat sinks in terms of both FOM and flow distribution. S-shaped pin-fins with pointed tips provided the best performance compared to pin-fins with straight and circular tips.

Thermal resistance of high power LED influenced by ZnO thickness and surface roughness parameter

2016 ◽  
Vol 33 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Shanmugan Subramani ◽  
Mutharasu Devarajan
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Roughness Parameter ◽  
Junction Temperature ◽  
Zno Thin Film ◽  
Content Type ◽  
Cu Substrates

Purpose – The purpose of this research is to study the effect of thickness and surface properties of ZnO solid thin film for heat dissipation application in LED. Heat dissipation in electronic packaging can be improved by applying a thermally conductive interface material (TIM) and hence the junction temperature will be maintained. ZnO is one of the oxide materials and used as a filler to increase the thermal conductivity of thermal paste. The thickness of these paste-type material cannot be controlled which restricts the heat flow from the LED junction to ambient. The controlled thickness is only possible by using a solid thin-film interface material. Design/methodology/approach – Radio Frequency (RF)-sputtered ZnO thin film on Cu substrates were used as a heat sink for high-power LED and the thermal performance of various ZnO thin film thickness on changing total thermal resistance (R th-tot) and rise in junction temperature were tested. Thermal transient analysis was used to study the performance of the given LED. The influence of surface roughness profile was also tested on the LED performance. Findings – The junction temperature was high (6.35°C) for 200 nm thickness of ZnO thin film boundary condition when compared with bare Cu substrates. Consecutively, low R th-tot values were noticed with the same boundary condition. The 600 nm thickness of ZnO thin film exhibited high R th-tot and interface resistance than the other thicknesses. Bond Line Thickness of the interface material was influenced on the interface thermal resistance which was decreased with increased BLT. Surface roughness parameter showed an immense effect on thermal transport, and hence, low R th (47.6 K/W) value was noticed with low film roughness (7 nm) as compared with bare Cu substrate (50.8 K/W) where the surface roughness was 20.5 nm. Originality/value – Instead of using thermal paste, solid thin film ZnO is used as TIM and coated Cu substrates were used as a heat sink. The thickness can be controlled, and it is a new approach for reducing the BLT between the metal core printed circuit board and heat sink.

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