Computational Fluid Dynamics Based Investigation of the Performance of Hybrid Heat Sinks

2021 ◽  
Author(s):  
Anas Alkhazaleh ◽  
Mohamed Younes El-Saghir Selim ◽  
Fadi Alnaimat ◽  
Bobby Mathew
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Heat Sinks ◽  
Geometrical Parameters ◽  
Microchannel Heat Sink ◽  
Liquid Cooling ◽  
Pin Fins

Abstract This article discusses the mathematical modeling of a straight microchannel heat sink, embedded with pin-fins, for purposes of liquid cooling of microelectronic chips. The influence of three different geometrical parameters, pin fins’ diameter, pitch, and hydraulic diameter, on the heat sinks performance is studied. The studies are performed for Reynolds numbers varying from 250 to 2000, and the results are quantified based on thermal resistance and pressure drop. The heat sinks embedded with pin fins have better performance in terms of thermal resistance but at the same time have higher pressure drop. Studies revealed that increasing the pin fins’ diameter, pitch, and hydraulic diameter have an influence on the thermal resistance; the thermal resistance is found to be decreasing with increasing these parameters for the same Reynolds number. For the cases studied, the reduction in thermal resistance of straight microchannels embedded with pin fins varied from 18% to 60% compared with that of traditional straight microchannels for different heat sinks configurations and Reynolds number. On the other hand, the pressure drop is increasing with an increase in pin fins’ diameter and pitch, while it is found to be decreasing with increasing the hydraulic diameter.

Thermo-Hydraulic Performance of Heat Sinks With Microchannel Embedded With Pin-fins

2021 ◽  
Author(s):  
Anas Alkhazaleh ◽  
Mohamed Younes El-Saghir Selim ◽  
Fadi Alnaimat ◽  
Bobby Mathew
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Reynolds Numbers ◽  
Sine Wave ◽  
Hydraulic Diameter ◽  
Heat Sinks ◽  
Microchannel Heat Sink ◽  
Pin Fins ◽  
The Cost

Abstract In this work, an investigation of the heat sink performance employing sinusoidal microchannels embedded with pin fins was conducted. The effect of the sine wave frequency, the pin fins’ diameter, and the hydraulic diameter of the microchannel are studied. The results are quantified in terms of thermal resistance and pressure drop. The study was done using Reynolds numbers varying from 250 to 2000. As Reynolds number increases, the heat sink’s thermal resistance decreased while the pressure drop increased accordingly for all scenarios. The sinusoidal microchannels showed better performance — lower thermal resistance — but with the cost of higher pressure drop compared to the straight microchannel heat sink. The heat sink’s performance was improved by increasing the frequency, diameter of pin fins, and hydraulic diameter; however, this reduction in thermal resistance was associated with an increase in pressure drop. The reduction in thermal resistance of the different configurations of the sinusoidal microchannels was between 17% and 69% compared to the straight microchannel heat sink.

Comparative Study of Thermal Performance of Longitudinal and Transversal-Wavy Microchannel Heat Sinks for Electronic Cooling

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Gongnan Xie ◽  
Jian Liu ◽  
Yanquan Liu ◽  
Bengt Sunden ◽  
Weihong Zhang
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Thermal Resistance ◽  
Cross Section ◽  
Thermal Performance ◽  
Heat Load ◽  
Rectangular Cross Section ◽  
Flow Direction ◽  
Heat Sinks ◽  
Liquid Cooling

Liquid cooling incorporating microchannels are used to cool electronic chips in order to remove more heat load. However, such microchannels are often designed to be straight with rectangular cross section. In this paper, on the basis of straight microchannels having rectangular cross section (SRC), longitudinal-wavy microchannel (LWC), and transversal microchannel (TWC) were designed, respectively, and then the corresponding laminar flow and heat transfer were investigated numerically. Among them, the channel wall of LWC undulates along the flow direction according to a sinusoidal function while the TWC undulates along the transversal direction. The numerical results show that for removing an identical heat load, the overall thermal resistance of the LWC is decreased with increasing inlet Reynolds number while the pressure drop is increased greatly, so that the overall thermal performance of LWC is inferior to that of SRC under the considered geometries. On the contrary, TWC has a great potential to reduce the pressure drop compared to SRC, especially for higher wave amplitudes at the same Reynolds number. Thus the overall thermal performance of TWC is superior to that of SRC. It is suggested that the TWC can be used to cool chips effectively with much smaller pressure drop penalty. In addition to the overall thermal resistance, other criteria of evaluation of the overall thermal performance, e.g., (Nu/Nu0)/(f/f0) and (Nu/Nu0)/(f/f0)1/3, are applied and some controversial results are obtained.

Hydrodynamic and Thermal Performance of Microchannels With Different Staggered Arrangements of Cylindrical Micro Pin Fins

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Ali Mohammadi ◽  
Ali Koşar
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Design Parameters ◽  
Interaction Patterns ◽  
Wake Region ◽  
Pin Fins ◽  
Micro Pin Fins

This study focuses on microheat sinks with different staggered arrangements of micro pin fins (MPFs). A rectangular microchannel with the dimensions of 5000 × 1500 × 100 μm3 (l′ × w′ × h′) was considered for all the configurations while different MPF diameters, height over diameter ratio (H/D), and longitudinal and transversal pitch ratios (SL/D and ST/D) were considered in different arrangements. Using the ansys fluent 14.5 commercial software, the simulations were done for different Reynolds numbers between 20 and 160. A constant heat flux of 30 W/cm2 was applied through the bottom heating section. The performances of the microheat sinks were evaluated using design parameters, namely pressure drop, friction factor, Nusselt number, and thermal-hydraulic performance index (TPI). The effect of each geometrical parameter as well as wake-pin fin interaction patterns were carefully studied using the streamline patterns and temperature profiles of each configuration. The results reveal a great dependency of trends in pressure drops and Nusselt numbers on the wake region lengths as well as the local velocity and pressure gradients. Moreover, the wake region lengths mostly contribute to the increase in obtained pressure drop and Nusselt number with Reynolds number. Although an increase in the H/D and SL/D ratios results in an increase and a decrease in pressure drop, respectively, the effect on the Nusselt number depends on other geometrical parameters and Reynolds number. A larger ST/D ratio generally results in a decrease in the pressure drop and Nusselt number. Finally, while the friction factor decreases with Reynolds number, two different trends are seen for the TPI values of configurations with the H/D ratio of 1 and 2 (D = 100 and 50 μm). While the trend in the TPIs is increasing for Reynolds numbers between 20 and 40, it reverses for higher Reynolds numbers with a steeper slope in the configurations with the ST/D ratio of 1.5.

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 Analysis and Experimental Validation of Laminar Heat Transfer and Pressure Drop in Serpentine Channel Heat Sinks for Electronic Cooling

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Xiaohong Hao ◽  
Bei Peng ◽  
Gongnan Xie ◽  
Yi Chen
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Reynolds Numbers ◽  
Electronic Cooling ◽  
Heat Sinks ◽  
Total Thermal Resistance ◽  
Serpentine Channel ◽  
Resistance Network ◽  
Aspect Ratios ◽  
Resistance Network Model

In this paper, a thermal resistance network analytical model is proposed to investigate the thermal resistance and pressure drop in serpentine channel heat sinks with 180 deg bends. The total thermal resistance is obtained using a thermal resistance network model based on the equivalent thermal circuit method. Pressure drop is derived considering straight channel and bend loss because the bends interrupt the hydrodynamic boundary periodically. Considering the effects of laminar flow development and redevelopment, the bend loss coefficient is obtained as a function of the Reynolds number, aspect ratios, widths of fins, and turn clearances, through a three-regime correlation. The model is then experimentally validated by measuring the temperature and pressure characteristics of heat sinks with different Reynolds numbers and different geometric parameters. Finally, the temperature-rise and pressure distribution of the thermal fluid with Reynolds numbers of 500, 1000, and 1500 are examined utilizing this model.

Experimental Investigation of Liquid Cooling Through Shallow Copperclad Cavities With Etched Pin-Fin Arrays

2018 ◽  
Author(s):  
Yin Lam ◽  
Nicole Okamoto ◽  
Younes Shabany ◽  
Sang-Joon John Lee
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Surface Area ◽  
Flow Rate ◽  
Heat Sink ◽  
Heat Removal ◽  
Heat Sinks ◽  
Liquid Cooling ◽  
Pin Fin ◽  
Pin Fin Arrays

Heat removal is an increasing engineering challenge for higher-density packaging of circuit components. Microchannel heat sinks with liquid cooling have been investigated to take advantage of high surface-to-volume ratio and higher heat capacity of liquids relative to gases. This study experimentally investigated heat removal by liquid cooling through shallow copperclad cavities with staggered pin-fin arrays. Cavities with pin-fins were fabricated by chemical etching of a copperclad layer (nominally 105 μm thick) on a printed-circuit substrate (FR-4). The overall etched cavity was 30 mm wide, 40 mm long, and 0.1 mm deep. The pins were 1.1 mm in diameter and were distributed in a staggered arrangement. The cavity was sealed with a second copperclad substrate using an elastomer gasket. This assembly was then connected to a syringe pump delivery system. Deionized water was used as the working fluid, with volumetric flow rate up to 1.5 mL/min. The heat sink was subjected to a uniform heat flux of 5 W on the underside. Performance of the heat sink was evaluated in terms of pressure drop and the convection thermal resistance. Pressure drop across the heat sinks was less than 10 kPa, dominated by wall surface area rather than the small surface area contributed by cylindrical pins. At low flow rate, caloric thermal resistance dominated the overall thermal resistance of the heat sink. When compared to a microchannel without pins, the pin-fin microchannel reduced convective thermal resistance of the heat sink by approximately a factor of 4.

Evaluation of Various Channel Shapes of a Microchannel Heat Sink

2016 ◽  
Vol 24 (03) ◽  
pp. 1650018 ◽  
Author(s):  
Aatif Ali Khan ◽  
Kwang-Yong Kim
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Stokes Equations ◽  
Hydraulic Diameter ◽  
Navier Stokes ◽  
Average Height ◽  
Microchannel Heat Sink ◽  
Navier Stokes Equations ◽  
Number Range

Thermal and hydraulic performances of various geometric shapes of a microchannel heat sink were evaluated numerically using Navier–Stokes equations. A heat sink comprised of a [Formula: see text][Formula: see text]cm2 silicon wafer was investigated with water as the cooling fluid. The performances of seven microchannel shapes were compared at the same microchannel hydraulic diameter and the same average height of the bottom silicon substrate. The thermal resistance, friction coefficient, and Nusselt number were calculated for a Reynolds number range of 50 to 500. The results show that an inverse trapezoidal shape gives the lowest thermal resistance for a Reynolds number up to 300. The values of [Formula: see text]Re are almost similar for all the shapes because of the constant hydraulic diameter.

A Numerical Parametric Study of Flow and Heat Transfer in Circular and Zig-Zag Square Microchannel Heat Sinks

2016 ◽  
Author(s):  
Wenming Li ◽  
Fanghao Yang ◽  
Tamanna Alam ◽  
Congcong Ren
Keyword(s):  
Pressure Drop ◽  
Thermal Resistance ◽  
Parametric Study ◽  
Orientation Angle ◽  
Hydraulic Diameter ◽  
Heat Sinks ◽  
Microchannel Heat Sinks ◽  
Circular Microchannel ◽  
Square Microchannel ◽  
Numerical Parametric Study

This paper aims to study the overall performance of circular and zig-zag square microchannel heat sinks with single phase liquid flow via a numerical parametric study. Thermal resistance and pressure drop when subjected to key geometric parameters such as hydraulic diameter, orientation, and connector length is numerically investigated with Reynolds number ranging from 50 to 500. Specifically, the hydraulic diameter is varied from 100 μm to 300 μm with an increment of 100 μm; the orientation angle of 10°, 20° and 30° is studied. A figure of merit (FOM) involving both the thermal resistance and pressure drop is introduced to evaluate the performance. Results show that hydraulic diameter is critical to thermal resistance and pressure drop compared to orientation angle. Zig-zag microchannel heat sink shows better performance compared with heat sinks with circular microchannel. FOM varies considerably with the change in hydraulic diameter and flow rate.

scholarly journals Prediction and Measurement of Pressure Drop of Water Flowing in a Rectangular Microchannel

2013 ◽  
Vol 3 (2) ◽  
Author(s):  
M. Mirmanto
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Inlet Temperature ◽  
Mean Velocity ◽  
Rectangular Microchannel ◽  
The Mean ◽  
Poiseuille Number

This paper presents experimental results of pressure drop measurement and prediction of water flowing through a copper rectangular microchannel with a hydraulic diameter of 437 µm. The aim of this work is to identify discrepancies between experimental data and macrochannel theory. An inlet temperature of 60oC was kept constant at the channel entrance and the experiments were performed with Reynolds numbers (based on the mean velocity and hydraulic diameter) ranging up to 4500.  The results show that the pressure drop prediction agrees with the theory. However, the trend of Poiseuille number with the Reynolds number was not constant for laminar flow. This could be due to the entrance effect. Moreover, the friction factor theory could predict the experimental data for turbulent flow. Thus, in this experiment, the theory for flow in macro passages is still applicable.

scholarly journals Parametric optimization of a stamped longitudinal vortex generator inside a circular tube of a solar water heater at low Reynolds numbers

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
Felipe A. S. Silva ◽  
Luis Júnior ◽  
José Silva ◽  
Sandilya Kambampati ◽  
Leandro Salviano
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Reynolds Numbers ◽  
Geometric Parameters ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Solar Water Heater ◽  
Water Heater ◽  
Solar Water

AbstractSolar Water Heater (SWH) has low efficiency and the performance of this type of device needs to be improved to provide useful and ecological sources of energy. The passive techniques of augmentation heat transfer are an effective strategy to increase the convective heat transfer coefficient without external equipment. In this way, recent investigations have been done to study the potential applications of different inserts including wire coils, vortex generators, and twisted tapes for several solar thermal applications. However, few researchers have investigated inserts in SWH which is useful in many sectors where the working fluid operates at moderate temperatures. The longitudinal vortex generators (LVG) have been applied to promote heat transfer enhancement with a low/moderate pressure drop penalty. Therefore, the present work investigated optimal geometric parameters of LVG to enhance the heat transfer for a SWH at low Reynolds number and laminar flow, using a 3D periodical numerical simulation based on the Finite Volume Method coupled to the Genetic Algorithm optimization method (NSGA-II). The LVG was stamped over a flat plate inserted inside a smooth tube operating under a typical residential application corresponding to Reynolds numbers of 300, 600, and 900. The geometric parameters of LGV were submitted to the optimization procedure which can find traditional LVG such as rectangular-winglet and delta-winglet or a mix of them. The results showed that the application of LGVs to enhance heat transfer is an effective passive technique. The different optimal shapes of the LVG for all Reynolds numbers evaluated improved more than 50% of heat transfer. The highest augmentation heat transfer of 62% is found for the Reynolds number 900. However, the best thermo-hydraulic efficiency value is found for the Reynolds number of 600 in which the heat transfer intensification represents 55% of the pressure drop penalty.

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