Yung Chan , Suman Sinha Ray and Alexander L. YarinMicro/Nanoscale Fluid Transport LaboratoryEngineering Research Facility Room 1014University of Illinois at Chicago, IL 60612

2010 NSF REU Summer Program

Hydrodynamics of Drop Impact and Spray Cooling through Nanofiber Mats

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Outline

Acknowledgement Introduction Applications Experiments Results and Discussions Conclusion Reference

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Acknowledgement3

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Introduction

Drop impacts on dry surface exhibit more complicated flow patterns than those on the wetted surfaces

Six possible outcomes of drop

impacts on a dry surface

Drop impact on dry surface is a key element of a wide variety of phenomena encountered in many technical applications, including spray printing, rapid spray cooling of hot surface, ice accumulation on power lines and aircrafts

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Applications Spray cooling can be used to transfer large amounts of energy through the

latent heat of evaporation, heat transfer rate much higher than pool boiling since the drop can be removed heat from surface more easily.

Water Spray Cooling: extremely high heat transfer (L= 2260J/g)

cooling microelectronic chips , radiological elements and server room.

Semiconducting diamond devices works up to temperatures of 500 °C, and silicon devices fail at around 150 °C

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Use minimum amount of water to transfer maximum heat from device in shorter time.

Coating that can increase the interface

Experiment- Nanofiber Mat Coating

Electrospinning is a process that produces continuous polymer fibers through the action of an external electric field imposed on a polymer solution.

Primary characteristic of nanofibers is the high ratio of surface area to mass .

Then polymer fiber distributed on the grounded plate

PAN (Poly-acrylonitrile) is a resinous, fibrous, and rubbery organic polymer.

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Experiment-set up 7

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Experiment

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Copper Substrate at 200 C

Copper Nanofiber Mat at 200C

Result and Discussion-1

In room temperature

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Result and Discussion-2

In room temperature

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Result and Discussion-311

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Result and Discussion-412

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Result and Discussion-513

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Conclusion

Nanofiber mat coating:

Silver > Copper > Nickel > PAN

Based on cost and heat flux rate: Copper nanofiber mat is the best coating.

Copper nanofiber mat: high thermal conductivity

high interface between water and hot surface Copper nanofiber coating may lead to a breakthrough in the

development of a new generation of spray cooling process.

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Reference

Alexander L. Yarin, “Drop Impact Dynamics: Splashing, Spreading, Receding, Bouncing…” Annual Review of Fluid Mechanics, Vol. 38, pp.159-192, Jan. 2006.

Darrel l H. Reneker, and Alexander L. Yarin, “Electrospinning jets and polymer nanofibers” Polymer, Vol. 49, pp.2387-2425, Feb. 2008.

Andreas N. Lembach, Yiyun Zhang, and Alexander L. Yarin, “Drop Impact, Spreding, Splashing, and Penetration into Electrospun Nanofiber Mats” Langmuir Article, Vol. 26, pp.9516-9523, Feb. 2010.

R. Srikar, A.L. Yarin, “ Nanofiber coating of surfaces for intensification of drop or spray impact cooling” International Journal of Heat and Mass Transfer, Vol. 52, pp.5814-5826, Sept. 2009.

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Questions?

Thank you for your attention!

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