Noise Measurements and Reduction for High-Frequency Vibrating Devices in the Application of Cooling Electronics

2012 ◽  
Author(s):  
Longzhong Huang ◽  
Terrence Simon ◽  
Min Zhang ◽  
Taiho Yeom ◽  
Mark North ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Frequency ◽  
Noise Level ◽  
Electronics Cooling ◽  
Acoustic Energy ◽  
High Heat Flux ◽  
Driving Voltage ◽  
Active Device ◽  
Acoustic Characteristics ◽  
Active Devices

Traditional heat sinks for electronics cooling have become ever more difficult to design to meet the high dissipation rate of modern high-heat-flux electronics. Active devices, especially devices operating at a high frequency, show promise toward enhancing heat transfer performance. However, active devices generate noise that may not be acceptable to personnel. The present work studies acoustic characteristics of piezoelectrically-driven synthetic jets and oscillating plate agitators operating at high frequency (around 1000 Hz) employed in an electronics cooling module for heat transfer enhancement purposes. The A-weighted noise level from such actuators is measured and found to increase with increases of driving voltage and operational frequency. The measured sound pressure level of the active devices used in our present enhanced heat transfer module can be as high as 100 dB. Through a power spectrum analysis, we find that most acoustic energy is in a narrow frequency band close to the operating frequency of the active device. To decrease the noise level, a muffler, which also allows cooling air to recirculate through the equipment cabinet, has been designed and tested. An analytical model is employed to select the geometry of the muffler for optimal performance based on acoustic characteristics of the active devices and the through-flow pressure drop. The muffler having this optimal design is fabricated and tested and found to be able to decrease the noise level generated by two actuators from 83 dB to 64 dB.

Reciprocating-Mechanism Driven Heat Loops and Their Applications

2003 ◽  
Author(s):  
Yiding Cao ◽  
Mingcong Gao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Electronics Cooling ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Condenser Section ◽  
Evaporator Section ◽  
Two Phase Heat Transfer ◽  
Transfer Device

This paper introduces a novel heat transfer mechanism that facilitates two-phase heat transfer while eliminating the so-called cavitation problem commonly encountered by a conventional pump. The heat transfer device is coined as the reciprocating-mechanism driven heat loop (RMDHL), which includes a hollow loop having an interior flow passage, an amount of working fluid filled within the loop, and a reciprocating driver. The hollow loop has an evaporator section, a condenser section, and a liquid reservoir. The reciprocating driver is integrated with the liquid reservoir and facilitates a reciprocating flow of the working fluid within the loop, so that liquid is supplied from the condenser section to the evaporator section under a substantially saturated condition and the so-called cavitation problem associated with a conventional pump is avoided. The reciprocating driver could be a solenoid-operated reciprocating driver for electronics cooling applications and a bellows-type reciprocating driver for high-temperature applications. Experimental study has been undertaken for a solenoid-operated heat loop in connection with high heat flux thermal management applications. Experimental results show that the heat loop worked very effectively and a heat flux as high as 300 W/cm2 in the evaporator section could be handled. The applications of the bellows-type reciprocating heat loop for gas turbine nozzle guide vanes and the leading edges of hypersonic vehicles are also illustrated. The new heat transfer device is expected to advance the current two-phase heat transfer device and open up a new frontier for further research and development.

Mechanistic Considerations for Enhancing Flow Boiling Heat Transfer in Microchannels

2015 ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Electronics Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Nucleation Sites ◽  
Flow Boiling Heat Transfer ◽  
Underlying Mechanisms

Research efforts on flow boiling in microchannels were focused on stabilizing the flow during the early part of the last decade. After achieving that goal through inlet restrictors and distributed nucleation sites, the focus has now shifted on improving its performance for high heat flux dissipation. The recent worldwide efforts described in this paper are aimed at increasing the critical heat flux (CHF) while keeping the pressure drop low, with an implicit goal of dissipating 1 kW/cm2 for meeting the high-end target in electronics cooling application. The underlying mechanisms in these studies are identified and critically evaluated for their potential in meeting the high heat flux dissipation goals. Future need to simultaneously increase the CHF and the heat transfer coefficient (HTC) has been identified and hierarchical integration of nanoscale and microscale technologies is deemed necessary for developing integrated pathways toward meeting this objective.

Fluid Damping and Power Consumption of Active Devices Used in Cooling Electronics

2012 ◽  
Author(s):  
Longzhong Huang ◽  
Smita Agrawal ◽  
Terrence Simon ◽  
Min Zhang ◽  
Taiho Yeom ◽  
...  
Keyword(s):  
Power Consumption ◽  
Cooling System ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Operating Conditions ◽  
High Heat Flux ◽  
Active Device ◽  
Active Devices ◽  
Fluid Damping ◽  
Oscillating Plate

Active devices, such as synthetic jets and oscillating plate agitators were found to be effective in cooling of high-heat-flux electronics. These devices generate unsteady flows, thinning the thermal boundary layer and enhancing turbulent transport. However, the active devices cause extra power consumption due to flow friction and separation. It is important to understand the factors influencing power consumption in these devices if they are to be applied in cooling system designs. The present study analyzes fluid damping and power consumption in high-frequency (about 1000 Hz) synthetic jets and oscillating plate agitators driven by piezoelectric stacks. This analysis is done numerically, since it is difficult to measure fluid damping. In the simulations, the moving part of the active device is modeled with the moving wall boundary condition. The mesh is updated and the flow is calculated every time the moving part changes its position. The coherent vortex structures generated by theses active devices, like vortices in the synthetic jet cavity or in the oscillating plate tip gap region, are found to cause fluid damping and power consumption. Fluidic power consumption levels with different geometries and different operating frequencies and amplitudes are studied. A correlation is developed to predict fluidic power consumption at different operating conditions.

Experimental and Analytical Studies of Reciprocating-Mechanism Driven Heat Loops (RMDHLs)

2008 ◽  
Vol 130 (7) ◽  
Author(s):  
Yiding Cao ◽  
Mingcong Gao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Electronics Cooling ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Condenser Section ◽  
Analytical Studies ◽  
Evaporator Section

This paper conducts experimental and analytical studies of a novel heat-transfer device, reciprocating-mechanism driven heat loop (RMDHL) that facilitates two-phase heat transfer while eliminating the so-called cavitation problem commonly encountered by a conventional pump. A RMDHL normally includes a hollow loop having an interior flow passage, an amount of working fluid filled within the loop, and a reciprocating driver. The hollow loop has an evaporator section, a condenser section, and a liquid reservoir. The reciprocating driver is integrated with the liquid reservoir and facilitates a reciprocating flow of the working fluid within the loop, so that liquid is supplied from the condenser section to the evaporator section under a substantially saturated condition and the so-called cavitation problem associated with a conventional pump is avoided. The reciprocating driver could be a solenoid-operated reciprocating driver for electronics cooling applications and a bellows-type reciprocating driver for high-temperature applications. Experimental study has been undertaken for a solenoid-operated heat loop in connection with high heat flux thermal management applications. Experimental results show that the heat loop worked very effectively and a heat flux as high as 300W∕cm2 in the evaporator section could be handled. A working criterion has also been derived, which could provide a guidance for the design of a RMDHL.

Forced Convective Boiling in Microchannels for kW/cm2 Electronics Cooling

2003 ◽  
Author(s):  
Daniel J. Faulkner ◽  
Reza Shekarriz
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Electronics Cooling ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Design Solution ◽  
High Heat Flux ◽  
Convective Boiling ◽  
High Heat Transfer

This paper reports some of the results of our tests for the development of a high heat flux cooling system for thermal management of high power electronics. Our objective is to develop a practical design solution for achieving 1000 W/cm2 cooling. To achieve such high heat transfer rates, we have pursued and combined design advantages of a microchannel heat exchanger, high heat fluxes associated with forced convective nucleate boiling, and the use of a nanoparticles laden fluid for enhancement of heat transfer. A laboratory test module was designed, built, and tested to verify its performance. The experimental system employed sub-cooled as well as saturated forced convection boiling heat transfer in a high aspect ratio parallel microchannel heat sink. The working fluids tested were water and a selection of ceramic-based nanoparticle suspensions (nanofluids). The system was observed to readily dissipate heat fluxes in excess of 275 W/cm2 of substrate, while maintaining the substrate at or below 125°C. For optimized fin geometry, the current conditions would result in greater than 500 W/cm2. While the use of nanofluids was intended for boiling enhancement to push the envelop beyond 1000 W/cm2, we discerned limited improvement in the overall heat transfer rate. Future studies are planned for further exploitation of nanoparticles for enhancement of convective nucleate boiling.

Effects of High Frequency Droplet Train Impingement on Spreading-Splashing Transition, Film Hydrodynamics and Heat Transfer

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Taolue Zhang ◽  
Jorge Alvarado ◽  
J. P. Muthusamy ◽  
Anoop Kanjirakat ◽  
Reza Sadr
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Liquid Film ◽  
High Frequency ◽  
High Heat ◽  
High Heat Flux ◽  
Droplet Impingement ◽  
Dry Out ◽  
The Impact

The objective of this study is to investigate the effects of droplet-induced crown propagation regimes (spreading and splashing) on liquid film hydrodynamics and heat transfer. In this work, the effects of high frequency droplet train impingement on spreading-splashing transition, liquid film hydrodynamics and surface heat transfer were investigated experimentally. HFE-7100 droplet train was generated using a piezo-electric droplet generator at a fixed flow rate of 165 mL/h. Optical and IR images were captured at stable droplet impingement conditions to visualize the thermal physical process. The droplet-induced crown propagation transition phenomena from spreading to splashing were observed by increasing the droplet Weber number. The liquid film hydrodynamics induced by droplet train impingement becomes more complex when the surface was heated. Bubbles and micro-scale fingering phenomena were observed outside the impact crater under low heat flux conditions. Dry-out was observed outside the impact craters under high heat flux conditions. IR images of the heater surface show that heat transfer was most effective within the droplet impact crater zone due to high fluid inertia including high radial momentum caused by high-frequency droplet impingement. Time-averaged heat transfer measurements indicate that the heat flux-surface temperature curves are linear at low surface temperature and before the onset of dry-out. However, a sharp increase in surface temperature can be observed when dry-out appears on the heater surface. Results also show that strong splashing (We = 850) is unfavorable for heat transfer at high heat flux conditions due to instabilities of the liquid film, which lead to the onset of dry-out. In summary, the results show that droplet Weber number is a significant factor in the spreading-splashing transition, liquid film hydrodynamics and heat transfer.

Biotemplated Superhydrophobic Surfaces for Enhanced Dropwise Condensation

2012 ◽  
Author(s):  
Emre Olceroglu ◽  
Stephen M. King ◽  
Md. Mahamudur Rahman ◽  
Matthew McCarthy
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Electronics Cooling ◽  
High Heat ◽  
The Self ◽  
High Heat Flux ◽  
Dropwise Condensation ◽  
Large Area ◽  
Hydrophobic Surfaces ◽  
Structured Surfaces

The increased heat transfer achieved through dropwise condensation, as compared to filmwise condensation, has the potential to substantially impact a variety of applications including high-heat flux thermal management systems, integrated electronics cooling, and various industrial and chemical processes. Here, we report stable dropwise condensation onto biotemplated nanostructured super-hydrophobic surfaces. We have demonstrated continuous droplet coalescence and ejection at diameters of less than 20 μm and compared directly with flat hydrophobic surfaces. The self-ejection mechanism characteristic of dropwise condensation has been shown using a simple bio-nano-fabrication technique based on the self-assembly and mineralization of the Tobacco mosaic virus (TMV). This process is extendable to commercially relevant nanomanufacturing of both microscale electronics devices as well as large-scale large-area industrial equipment. This manufacturing flexibility is unique as compared to many other micro/nano-structured surfaces fabricated to demonstrate similar increases in condensation heat transfer.

Empirical Heat Transfer Models of Single- and Multiple-Nozzle Spray Cooling for Electronics

Volume 4 ◽  
2004 ◽  
Author(s):  
Timothy A. Shedd ◽  
Adam G. Pautsch
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Liquid Film ◽  
Single Phase ◽  
Thin Liquid Film ◽  
Electronics Cooling ◽  
Current Data ◽  
Film Boiling ◽  
High Heat Flux ◽  
Test Chips

The performance of single- and four-nozzle spays for high heat flux electronics cooling using nitrogen-saturated FC-72 was evaluated in this study. The testing was performed using a multichip module (MCM) test setup, similar to MCM’s used in current high-end computer systems. The MCM contained eight test chips; four of these were cooled by single-nozzle sprays and four by four-nozzle sprays simultaneously. The swirl-atomizing, full-cone spray nozzles were incorporated into a production spray plate and were positioned about 6 mm above the test chips. An additional facility was constructed for visualization of the sprays and heat transfer behavior using clear heating elements coated with an indium titanium oxide (ITO) film. Using both the heat transfer and visualization data, it was determined that the heat transfer could be broken down into two or three components: a dominant single-phase component in and around the spray impact, a two-phase liquid film boiling component in the corners away from the spray impact, and, for the multiple-nozzle sprays, a single-phase drainage flow component. Multi-part empirical models were generated based on this conceptual model, and the correlations predict the data to within 5%. In addition, a phenomenological critical heat flux (CHF) model was generated based on previous work with thin liquid-film boiling that suggests CHF in thin films occurs due to a homogeneous nucleation mechanism. This model predicts the current data to within 12% for both single- and four-nozzle arrays.

Bubble Growth During Nucleate Boiling in Microchannels

2010 ◽  
Author(s):  
David M. Christopher ◽  
Xipeng Lin
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
High Speed ◽  
Stokes Equations ◽  
Electronics Cooling ◽  
Nucleate Boiling ◽  
Nucleation Site ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Vof Model

The flow and heat transfer in microchannels has been of great interest for some years now due to the significantly higher heat transfer coefficients useful for enhancing the heat transfer in very small but high heat flux applications such as electronics cooling. Nucleate boiling heat transfer in microchannels is also of great interest for generating even higher heat transfer rates; however, numerous studies have shown that the bubble formation immediately fills the entire microchannel with vapor significantly reducing the heat transfer since the bubble size is normally of the same size as the microchannel. The bubble growth process is very fast and difficult to study experimentally, even with high speed cameras. This study numerically analyzes the flow and bubble growth in a microchannel for various conditions by solving the Navier-Stokes equations with the VOF model with an analytical microlayer model to provide the large amount of vapor produced by the curved region of the microlayer. As each bubble forms, the large pressure drop around the bubble causes the bubble to quickly break away from the nucleation site and move quickly downstream. The bubbles are quite small with the size depending on the bulk flow velocity, subcooling and the heating rate. The numerical results compare quite well with preliminary experimental observations of bubble growth on a microheater embedded in the channel wall for FC-72 flowing in a microchannel.

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