Showing papers on "Electronics cooling published in 2017"
TL;DR: In this paper, a critical review of traditional and emerging cooling methods as well as coolants for electronics is provided, summarizing traditional coolants, heat transfer properties and performances of potential new coolants such as nanofluids are also reviewed and analyzed.
Abstract: Continued miniaturization and demand for high-end performance of electronic devices and appliances have led to dramatic increase in their heat flux generation. Consequently, conventional coolants and cooling approaches are increasingly falling short in meeting the ever-increasing cooling needs and challenges of those high heat generating electronic devices. This study provides a critical review of traditional and emerging cooling methods as well as coolants for electronics. In addition to summarizing traditional coolants, heat transfer properties and performances of potential new coolants such as nanofluids are also reviewed and analyzed. With superior thermal properties and numerous benefits nanofluids show great promises in fulfilling the cooling demands of high heat generating electronic devices. It is believed that applications of such novel coolants in emerging techniques like micro-channels and micro-heat pipes can revolutionize cooling technologies for electronics in the future.
441 citations
TL;DR: In this article, phase change materials (PCMs) were used as thermal conductivity enhancers (TCEs) for passive cooling systems. But, the authors focused on the optimization of passive cooling system using extruded finned surfaces.
129 citations
TL;DR: In this paper, the use of passive cooling methods in microchannel heat sink is comprehensively discussed and the effects of some important parameters such as the type of channel types, surface roughness, fluid additives, and Reynolds number on the rate of heat transfer in micro channel heat sink are presented.
125 citations
TL;DR: In this paper, a new dynamic simulation tool using interconnected PDEs is described in the first part of the present paper followed by the validation of the modeling for both steady and dynamic regimes using a first-of-a-kind 15 cm-height thermosyphon test bench.
74 citations
TL;DR: In this article, the energy efficiency of a specific liquid block working with the water-Al2O3 nanofluid for utilization in electronics cooling is investigated and the effects of Reynolds number, nanoparticle size and volume concentration are evaluated.
58 citations
TL;DR: In this paper, the effect of surface structure size (size scale i.e. micro and nano size) on boiling heat transfer characteristics of samples with different surface morphology was investigated.
40 citations
33 citations
TL;DR: In this paper, a titanium dioxide (TiO2/water) nanofluid (with a volume fraction of 0.1%) is prepared by dispersing nanoparticles in distilled water.
29 citations
TL;DR: In this article, a new water cooling system applied in a permanent magnet synchronous motor is presented, inspired by a widely used concept in electronics cooling, which consists of implementing some cold plates in the magnetic core and a lot of experimental tests have been carried out to evaluate the thermal performance of this cooling process and estimate the influent parameters, such as ambient environment, flow rate, pressure stack, and distance between cold plates.
Abstract: This paper presents a new water cooling system applied in a permanent magnet synchronous motor This system is inspired by a widely used concept in electronics cooling It consists of implementing some cold plates in the magnetic core A lot of experimental tests have been carried out to evaluate the thermal performance of this cooling process and to estimate the influent parameters, such as ambient environment, flow rate, pressure stack, and distance between cold plates Numerical approach based on computational fluid dynamics and finite elements method has been carried out to study the flow structure and the temperature distribution Regarding the numerical results compared to the experimental results, it is noticed how much the flow structure has a significant influence on the overall thermal performance of this cooling design
25 citations
TL;DR: In this article, isothermal liquid flow distribution control between parallel tubes 1mm in diameter, utilizing Electrohydrodynamic (EHD) conduction pumps in meso scale was examined, using Novec 7600 Engineering Fluid operated at ambient conditions.
Abstract: Electrohydrodynamic (EHD) conduction pumping technology offers an innovative way to control flow distribution in multiscale environments. In EHD conduction, the interaction between a strong electric field and dissociated electrolyte species in a dielectric fluid generates a net body force and therefore a net flow. EHD conduction pumps have simple designs with no moving parts, low power consumption, and the ability to operate in microgravity. These pumps perform better at smaller scales and have been shown to be effective for heat transfer enhancement, with possible applications in electronics cooling terrestrially and in space. Flow distribution control using EHD conduction pumps was previously examined only in macro scale. This study experimentally and numerically examines isothermal liquid flow distribution control between parallel tubes 1 mm in diameter, utilizing EHD conduction pumps in meso scale. The working fluid is Novec 7600 Engineering Fluid operated at ambient conditions.
16 citations
TL;DR: In this paper, the effects of using nanofluids on impinging slot jet over a flat plate with a ribbed surface was investigated, where the main objective was to investigate the possibility of improving the overall heat transfer rate by focusing on the improvements in the local and average surface Nusselt number values.
Abstract: Impinging jet is one of various methods of cooling with the ability to achieve high heat transfer rates and improve average surface’s Nusselt number This method has vast industrial applications including integrated use in solar collectors, gas turbine cooling, refrigeration, air conditioning and electronics cooling A numerical study is conducted to study the effects of using nanofluids on impinging slot jet over a flat plate with a ribbed surface The main objective of the study was to investigate the possibility of improving the overall heat transfer rate by focusing on the improvements in the local and average surface Nusselt number values Several parameters effects are studied including Solid Volume Fraction, Richardson number and Reynolds number These results indicated a marked improvement in average Nusselt number with the increase in the solid volume fraction Also, there is an amended value when the buoyancy effect is dominant over the whole domain The results are shown in the form of streamlines, isotherms and Nusselt numbers contra other variables The current work was simulated using a FORTRAN CFD Code, which discretizes the non-dimensional forms of the governing equations utilizing the finite volume method and solving the consequent algebraic equations using Gauss-Seidel method Utilizing TDMA
01 May 2017
TL;DR: In this paper, an experimental study investigating the thermal performance of a two-phase thermosyphon for electronics cooling is presented, which consists of an evaporator with 18 individual microcooling zones connected via riser and downcomer tubes to an air-cooled condenser.
Abstract: An experimental study investigating the thermal performance of a two-phase thermosyphon for electronics cooling is presented in this article. Two-phase cooling implemented using a gravity-driven thermosyphon-based system represents an efficient solution for dissipating high power densities compared to traditional air-cooling approaches, allowing for increased reliability and reduced power consumption. The thermosyphon-based system consists of an evaporator with 18 individual microcooling zones connected via riser and downcomer tubes to an air-cooled condenser. Experiments were carried out with working fluid R134a for filling ratios ranging from 45% to 65%, heat loads from 102 W to 1841 W and air flow rates from 516 m3/h to 1404 m3/h. Robust thermal performance was observed for the entire range of operating conditions. In particular, at the optimum filling ratio of 50%, minimum air flow rate of 516 m3/h and uniform heat load of 1841 W, the temperature difference between the evaporator and ambient air was less than 20 K with a COP of 102, while at the highest fan speed of 1404 m3/h this temperature difference was reduced to 8.9 K, with a reasonable CoP of 11. The test results show the high efficiency of the current hybrid air- and liquid-based cooling technology for removing heat from electronics to the ambient.
TL;DR: In this paper, supercritical CO2 is proposed as a heat transfer fluid in micro-channel heat sink for power electronics cooling, and energy and exergetic performance analyses of micro channel heat sink using super critical CO2 are done and compared with conventional coolant, water.
Abstract: In view of increasing tendency of power density of electronic systems, cooling performance improvement of micro-channel heat sink is an emerging issue. In the present article, supercritical CO2 is proposed as a heat transfer fluid in micro-channel heat sink for power electronics cooling. Energetic and exergetic performance analyses of micro-channel heat sink using supercritical CO2 have been done and compared with conventional coolant, water. To take care of sharp change in properties in near critical region, the discretization technique has been used for simulation. Effects of both operating and geometric parameters (heat flux, flow rate, fluid inlet temperature, channel width ratio, and channel numbers) on thermal resistance, heat source (chip) temperature, pressure drop, pumping power and entropy generation are presented. Study shows that the thermal resistance, heat source temperature and pumping power are highly dependent on CO2 inlet pressure and temperature. Supercritical CO2 yields better performance than water for certain range of fluid inlet temperature. For the studied ranges, maximum reduction of thermal resistance by using CO2 is evaluated as 30%. Present study reveals that there is an opportunity to use supercritical CO2 as coolant for power electronic cooling at lower ambient temperature.
TL;DR: In this paper, a 3D model of an electrostatic fluid accelerator was simulated using the finite element method (as implemented in COMSOL Multiphysics), and the impinging flow of the accelerator was used to cool down a heating round plate.
TL;DR: In this article, an experimental evaluation of the thermal performance of four different passive devices was accomplished, which were a rod, a thermosyphon, a heat pipe with a metal screen as the capillary structure, and a heatpipe with microgrooves.
Abstract: The advent of modern electronic technology lead to miniaturization and high power density of electronic devices, then the existing electronic cooling techniques cannot be used, directly affecting the performance, cost, and reliability of electronic devices. Thus, the thermal management of electronic packaging has become a key technique in many products. Passive heat transfer devices can be a good alternative to the stabilization of electronic devices temperature. In this re-search, an experimental evaluation of the thermal performance of four different passive devices was accomplished. The considered devices were a rod, a thermosyphon, a heat pipe with a metal screen as the capillary structure, and a heat pipe with microgrooves. The heat pipe is a highly efficient device that carries large amounts of power with a small temperature difference. The heat pipe consists of the involucre, the working fluid, and the capillary structure. The thermosyphon is a kind of heat pipe assisted by gravity. In other words, it has no wick structure to return the working fluid. The devices were made of copper with a total length of 200 mm and an outer diameter of 9.45 mm. The thermosyphon and the heat pipes used deionized water as working fluid with a filling ratio of 60% of the evaporator volume. The devices were tested in vertical and horizontal positions under thermal loads between 5 W and 45 W. All the devices have operated satisfactorily when tested in accordance with the behavior of the thermal resistance. The heat pipes were the best among the tested devices and the best position was vertical.
01 May 2017
TL;DR: In this paper, an experimental study to analyse the thermal performance of a two-phase pump-driven loop for electronics cooling is presented, with the target application being a telecommunications equipment shelf having multiple circuit pack cards each dissipating several hundred Watts of power.
Abstract: An experimental study to analyse the thermal performance of a two-phase pump-driven loop for electronics cooling is presented, with the target application being a telecommunications equipment shelf having multiple circuit pack cards each dissipating several hundred Watts of power. The upward flow boiling heat transfer and pressure drop of R134a within an evaporator prototype fabricated with 18 individual microcooling zones to cool multiple electronics heat sources was investigated. The electronic heat sources were emulated by multiple copper heater blocks with embedded cartridge heaters, where each heat source was capable of dissipating more than 100 W, for a total power dissipation larger than 1800 W. Experimental results demonstrated the best cooling capability at a mass flow rate of 140 kg/h, uniform heat load of 1800 W to the 18 microcooling zones, system pressure of 600 kPa and inlet subcooling of 2 K in which the temperature difference between the evaporator and coolant inlet was 7.1 K with a uniform flow distribution within the evaporator.
TL;DR: Investigation of the effects of the area ratio of the ejector constant-area mixing section to the nozzle throat, the length of the constant- area section, and the nozzle exit position (NXP) on the performance of a miniature steam ejector shows that the performanceOf this investigation, CFD provided a good solution to the miniatureSteam ejector embedded with a capillary pump loop for electronics cooling application.
Abstract: A miniature steam ejector refrigeration system embedded with a capillary pump loop can result in a compact design which can be used for electronics cooling. In this paper, computational fluid dynamics (CFD) is employed to investigate the effects of the area ratio of the ejector constant-area mixing section to the nozzle throat, the length of the constant-area section, and the nozzle exit position (NXP), on the performance of a miniature steam ejector. Results show that the performance of the miniature steam ejector is very sensitive to the area ratio of the constant-area mixing section to the nozzle. For the needs of practical application, the area ratio of the constant-area mixing section to the nozzle should be smaller than 16 when the temperature of the primary flow is 60 °C. The NXP plays an important role in the flow phenomena inside the miniature ejector. The critical back pressure is more sensitive to length of the constant-area mixing section than the entrainment ratio. Results of this investigation provided a good solution to the miniature steam ejector embedded with a capillary pump loop for electronics cooling application.
TL;DR: The results showed that the Q2D method can predict the overall thermal resistance for the evaporator region and the whole heat pipe with a higher accuracy because the spreading resistance was significant and should be considered under small heater area (hot spot) conditions.
TL;DR: In this paper, the authors investigated the heat transfer performance of a vapor chamber and its effectiveness in the cooling of electronic devices and found that the maximum temperature decrease of 26 % and a maximum increase in the convective heat transfer coefficient of 36 % were achieved by using the vapor chamber.
Abstract: The heat transfer performance of a vapor chamber and its effectiveness in the cooling of electronic devices are experimentally and theoretically investigated in the present work. The power transistor in the circuit board usually operates with electric power that ranges from 15 W to 100 W, which is the heat input to the simulated processor. The heat flux varies between 3300 and 22000 W/m2. The simulated processor is cooled with the forced and induced air cooling methods with and without the use of the vapor chamber. Results show a maximum temperature decrease of 26 % and a maximum increase in the convective heat transfer coefficient of 36 %. The minimum value of the thermal resistance through the vapor chamber and the total thermal resistance is 0.195 and 0.82 °C/W, respectively. The experimental results are compared with the ANSYS predicted values.
TL;DR: In this article, a brief description of recent advances of convective heat transfer in some surface modified ducts using liquid crystal thermography and computational fluid dynamics is given, and influences of configuration and arrangement of surface modifications on the heat transfer are presented.
Abstract: Enhancement and control of forced convection heat transfer is important in many engineering applications and ducts of various surface complexity are used. Surface modifications like rib-roughening, grooves, dimples, protrusions, etc., are commonly applied in applications such as compact heat exchangers, electronics cooling as well as cooling in gas turbines and aircraft engines. This chapter gives a brief description of recent advances of convective heat transfer in some surface modified ducts using liquid crystal thermography and computational fluid dynamics. Details of temperature and heat transfer coefficient distributions are highlighted and influences of configuration and arrangement of surface modifications on the heat transfer are presented.
01 May 2017
TL;DR: In this article, an experimental study to investigate the thermal performance of a two-phase thermosyphon for electronics cooling is presented, where the secondary side of the condenser was connected via a riser and a downcomer to an ultra-compact condenser operating as a refrigerant-to-refrigerant counter flow heat exchanger.
Abstract: An experimental study to investigate the thermal performance of a two-phase thermosyphon for electronics cooling is presented in this article. In this study, the thermosyphon evaporator was connected via a riser and a downcomer to an ultra-compact condenser operating as a refrigerant-to-refrigerant counter flow heat exchanger. The secondary side of the condenser evaporated R134a from a “bus line” to condense the working fluid in the thermosyphon. Experiments were carried out for filling ratios ranging from 60% to 76%, heat loads from 102 W to 1841 W, secondary side mass flow rates from 40 kg/h to 120 kg/h, inlet subcoolings from about 0 K to 5 K, and saturation pressures from 600 kPa to 730 kPa. Robust thermal performance was observed for the entire range of operating test conditions. In particular, at the optimum filling ratio of 65%, secondary side mass flow rate of 80 kg/h, inlet subcooling close to 0 K and saturation pressure of 600 kPa, the mean temperature difference from the evaporator to inlet coolant was only 9.4 K. Experimental results demonstrated an increase of 14X in heat density dissipation, 19X increase in energy efficiency and a virtually noiseless system compared to the air-cooled thermosyphon discussed in Part 2.
TL;DR: In this article, the authors describe the complex interplay of single and multi-phase flow, residence time, mixing, and heat transfer with chemical kinetics in microchannels.
Abstract: Fluid flow and heat transfer in microchannels is since decades a wide area of vivid research in electronics cooling, compact heat exchangers, or chemical analytics. Fluid dynamics, mixing, and heat transfer are very important for performing exothermic chemical reactions in microchannels under stable and robust conditions. This contribution describes the complex interplay of single and multi-phase flow, residence time, mixing, and heat transfer with chemical kinetics. Dimensionless numbers and typical time scales guide the appropriate design and operation of microstructured equipment and chemical processes. Well-characterized, modular equipment enable short cut methods in the conceptual design phase and allow for consistent scale-up to production scale. The complex correlations are displayed here in a simple fashion with arrows, which can be replaced by relevant equations. The equipment is categorized with a toolbox concept of plate, tube, and vessel on certain platform levels for similar volumetri...
TL;DR: In this paper, an experimental exploration of flow boiling heat transfer in a spiraling radial inflow microchannel heat sink is presented, where the effect of surface wettability, fluid subcooling, and mass fluxes are considered.
Abstract: This study presents an experimental exploration of flow boiling heat transfer in a spiraling radial inflow microchannel heat sink. The effect of surface wettability, fluid subcooling, and mass fluxes are considered. The design of the heat sink provides an inward radial swirl flow between parallel, coaxial disks that form a microchannel of 300 microns. The channel is heated on one side, while the opposite side is essentially adiabatic to simulate a heat sink scenario for electronics cooling. To explore the effects of varying surface wetting, experiments were conducted with two different heated surfaces. One was a clean, machined copper surface and the other was a surface coated with zinc oxide nanostructures that are superhydrophilic. During boiling, increased wettability resulted in quicker rewetting and smaller bubble departure diameter, as indicated by reduced temperature oscillations during boiling, and achieving higher maximum heat flux without dryout. The highest heat transfer coefficients we...
TL;DR: In this paper, the authors proposed a thermal management technique based on spectral matching between thermal radiation and the infrared optical window of polymers, which are widely used in device encapsulation and packaging.
TL;DR: In this paper, the aerodynamic performance of a piezoelectrically actuated cantilever blade operating in the first mode of vibration was investigated for different operational conditions and blade confinement states.
Abstract: This paper investigates the aerodynamic performance of a piezoelectrically actuated cantilever blade operating in the first mode of vibration. Bulk air-moving capability and local velocity field features have been experimentally measured for different operational conditions and blade confinement states. A testing facility has been developed to determine the pressure-flow rate characteristics of a vibrating blade and simultaneously conduct particle image velocimetry. Under high system resistance, similar to that found in densely packed electronics, flow reversal occurs at the blade outlet region analogous to stall. This is accompanied by increased local unsteadiness in the airflow being emitted. Local turbulence intensity increases by 50% between maximum flow rate and maximum efficiency operating points. The introduction of confinement around a vibrating blade reduces bulk air-moving capability significantly, with pressure rise and volumetric flow rate measured as low as 20% of what can be achieved for an unconfined blade. However, there is an accompanying change in spatial velocity distribution, which focuses the flow normal to the outlet. This has potentially beneficial uses for targeted electronics cooling applications. The findings identify the relationship between local and bulk airflow characteristics that ultimately provides information about the sensitivity of this type of air-moving device in practical installations.
20 Jul 2017
TL;DR: In this article, a comprehensive linear compressor simulation model has been developed to describe the entire dynamic compression process and associated energy flows, based on mass and energy balance equations applied to open control volumes.
Abstract: The work presented in this paper focuses on the analytical modelling of the dynamic characteristics of a linear compressor used for electronics cooling. A comprehensive linear compressor simulation model has been developed to describe the entire dynamic compression process and associated energy flows. The model is based on mass and energy balance equations applied to open control volumes. The overall model is composed of several sub-models that include a piston dynamic model, an electrical motor model, a valve dynamic model, and a heat transfer model. When integrated together with an overall energy flow model for the compressor, it is possible to predict piston vibration, temperatures, and pressures within the compressor as well as overall performance. The dynamic characteristics of the linear compressor are analyzed and frequency response functions of the stroke are obtained to evaluate the effect of excitation frequency on the compressor performance and motor efficiency.
TL;DR: Based on the node analysis method and the conservation of energy and mass, Wang et al. as discussed by the authors developed a mathematic model to simulate the operation of heat pipes, which was further applied to evaluate the dynamic performance of using a heat pipe for electronics cooling.
01 Nov 2017
TL;DR: In this article, the performance of integrated piezoelectric fan with passive fans is discussed to enhance the heat transfer in cooling system by adding a magnet at the tip of the fan to activate other magnetic passive fans.
Abstract: Recently, piezoelectric fan has gained attention as potential active cooling method for electronics devices. Even though the piezoelectric requires high voltage, there are findings to overcome the shortcomings. Adding on a magnet at the tip of the piezoelectric fan to activate other magnetic passive fans is one of the methods to increase the total amplitude generated by the fans. This paper will discuss on the performance of integrated piezoelectric fan with passive fans (later refer to magnetic fans) to enhance the heat transfer in cooling system. A repulsive force produced by the magnets will cause the magnetic blades to oscillate together with the piezoelectric fan. The paper will focus on the optimization parameters of the magnets for selected dimension of piezoelectric fan. The parameters under investigation are the position of the magnet on the piezoelectric fan, number of magnets on each blades and orientation of blades with respect to adjacent blade. Results show that the magnet at middle location of extensive blade with double magnets generate the largest amplitude, 80% better than fan without magnet and for dual integrated piezoelectric fan with magnetic fan, radial orientation gives better result by 25%. By increasing the total amplitude, it shows a good agreement for positive heat transfer improvement compared to natural convection.
TL;DR: In this article, an external magnetic field was applied to generate enhanced mixing of the microfluidic flow to improve the cooling performance of two-phase liquid-liquid plug flow.
Abstract: Overheating of power electronic devices has become a significant issue due to their continued miniaturization and increased heat flux that needs to be dissipated. Microchannel heat sinks utilising two-phase flow are capable of very high heat transfer rates and represent a possible means of cooling such devices. In this paper, we focus on two-phase liquid-liquid plug flow using water-based ferrofluid (magnetic nanofluid) plugs as the dispersed phase and silicone oil as the continuous phase. An external magnetic field was applied to generate enhanced mixing of the microfluidic flow. We show that material properties of the ferrofluid plug influences heat transfer properties of the microfluidic flow, and demonstrate that cooling performance is further enhanced by the application of an external magnetic field which induces mixing. We also show that microchannel heat transfer using a ferrofluid is superior to that using de-ionized water as the dispersed phase for two-phase liquid-liquid plug flow.