Author: Majid Ali Faani Tabrizi Nezhaad
Publisher:
ISBN:
Category : Electrohydrodynamics
Languages : en
Pages : 492

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Author: Dong Soo Jung
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 246

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Author: Sri Laxmi Priya Raghupathi
Publisher:
ISBN:
Category :
Languages : en
Pages : 194

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Close-up video of boiling taking place on a nanostructured surface in a controlled laboratory experiment.

Author: H. Yamaguchi
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Author: Indranil M. Joshi
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages : 71

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"The miniaturization trend in electronics has spurred the development of efficient thermal management solutions. Single phase techniques are reliable but are limited by large fluid temperature differences and pressure drop. Two phase cooling has very little pressure drop with large heat absorption capacity. Boiling stands out as one of the most effective methods of heat dissipation which utilizes phase change. However, the design of two-phase systems is limited by the critical heat flux condition where a vapor layer prevents the liquid from contacting the heater surface. The current research study is directed towards increasing the CHF and maintaining low wall superheats to design efficient heat removal systems. In this study, different surface modification techniques are studied with an aim to identify various mechanisms that affect the heat transfer. Different surface enhancements in the form of Circumferential rectangular microchannels(CRM) and fin are used over cylindrical surface. Cylindrical tube with outer diameter of 15 mm was used for testing with water as working fluid. Tubular surface with fin attached performed the best yielding the CHF of 115 W/cm2 at wall superheat of 18oC which translated to an enhancement of 76%. The best performance of 110 W/cm2 at 9 oC without reaching CHF was obtained amongst CRM. Different mechanisms were identified by analyzing the results from pool boiling experiments. Area enhancement and contact line substantially affected the heat transfer performance in CRM. Area enhancement increased performance by providing additional area for heat transfer. Contact line region has higher heat flux. Single bubble growing over multiple grooves has increased contact line density which increases heat transfer performance. Increment in CHF was obtained by employing any one of these surface enhancements. High speed imaging enabled to analyze the behavior of bubble after nucleation on the fin surface thus deciphering the flow modulation over the cylindrical surface. Presence of bubble diverter at the bottom surface ensured higher evaporative momentum force towards the cylindrical surface. This displaced nucleating bubble at the bottom away from the fin, enabling liquid to rewet the surface. This allowed the formation of separate liquid vapor pathways which resulted in increased performance."--Abstract.

Author: Sujoy Kumar Saha
Publisher: Springer
ISBN: 3030207730
Category : Science
Languages : en
Pages : 125

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Book Description
This Brief deals with electrode design and placement, enhancement of both liquid and gas flow, vapor space condensation, in-tube condensation, falling film evaporation, correlations. It further provides a fundamental understanding of boiling and condensation, pool boiling, critical heat flux, convective vaporization, additives for single-phase liquids like solid particles, gas bubbles, suspensions in dilute polymer and surfactant solutions, solid additives and liquid additives for gases, additives for boiling, condensation and absorption, mass transfer resistance in gas phase (condensation with noncondensible gases, evaporation into air, dehumidifying finned tube heat exchangers, water film enhancement of finned tube exchanger), controlling resistance in liquid phase, and significant resistance in both phases. The volume is ideal for professionals and researchers dealing with thermal management in devices.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 16

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Author: Arvind Jaikumar
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages : 218

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"The advent of cloud computing and the complex packaging architecture of next generation electronic devices drives methods for advanced thermal management solutions. Convection based single-phase cooling systems are inefficient due to their large pressure drops, fluid temperature differences and costs, and are incapable of meeting the cooling requirements in the high power density components and systems. Alternatively, phase-change cooling techniques are attractive due to their ability to remove large amounts of heat while maintaining uniform fluid temperatures. Pool boiling heat transfer mechanism centers on the nucleation, growth and departure of a bubble from the heat transfer surface in a stagnant pool of liquid. The pool boiling performance is quantified by the Critical Heat Flux (CHF) and Heat Transfer Coefficients (HTC) which dictate the operating ranges and efficiency of the heat transfer process. In this work, three novel geometries are introduced to modify the nucleation characteristics, liquid pathways and contact line motion on the prime heater surface for a simultaneous increase in CHF and HTC. First, sintered microchannels and nucleating region with feeder channels (NRFC) were developed through the mechanistic concept of separate liquid-vapor pathways and enhanced macroconvection heat transfer. A maximum CHF of 420 W/cm2 at a wall superheat of 1.7 °C with a HTC of 2900 MW/m2°C was achieved with the sintered-channels configuration, while the NRFC reached a CHF of 394 W/cm2 with a HTC of 713 kW/m2°C. Second, the scale effect of liquid wettability, roughness and microlayer evaporation was exploited to facilitate capillary wicking in graphene through interlaced porous copper particles. A CHF of 220 W/cm2 with a HTC of 155 kW/m2°C was achieved using an electrodeposition coating technique. Third, the chemical heterogeneity on nanoscale coatings was shown to increase the contribution from transient conduction mechanisms. A maximum CHF of 226 W/cm2 with a HTC of 107 kW/m2°C was achieved. The enhancement techniques developed here provide a mechanistic tool at the microscale and nanoscale to increase the boiling CHF and HTC."--Abstract.

Author: Chinmay Patil
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages : 196

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