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Vapor Bubble Dynamics on Micro Line Heaters in Microchannel

Nov. 30 th , 2004. Vapor Bubble Dynamics on Micro Line Heaters in Microchannel. Jin Su Department of Mechanical Engineering. contents. Introduction Bubble Physics Experimental Study Numerical Simulation Application – Microinjector Conclusions. 1. Introduction.

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Vapor Bubble Dynamics on Micro Line Heaters in Microchannel

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  1. Nov. 30th , 2004 Vapor Bubble Dynamics on Micro Line Heaters in Microchannel Jin Su Department of Mechanical Engineering

  2. contents • Introduction • Bubble Physics • Experimental Study • Numerical Simulation • Application – Microinjector • Conclusions

  3. 1. Introduction • Bubbles are prevalent in MEMS devices, such as the bubble driven micropump, microinjector in ink-jet printer, etc; • Common situations are found in these cases – bubble generated by pulsed microheater • This topic is widely studied and has successful applications to micorinjector

  4. 2. Bubble Physics[1] Fig. 1. Bubble growth and collapse or

  5. Hong et al (2004) [2] 3. Experimental Study Size: Heat flux: ~ 417 MW/m2 Working Fluid: water

  6. Yin et al (2004) [3] 3. Experimental Study Size: Cylindrical chamber: Di: 73 mm; H: 55 mm Heater: 5 wide, 200 nm thick, lines laid out in a serpentine pattern over an area of Working Fluid: FC-72 (3M Corporation) Heat flux: ~ 44.4 MW/m2

  7. Lee et al (2003) [4] 3. Experimental Study Size: Chamber: Heater: Working Fluid: FC-72, FC-77 and FC-40

  8. Wang et al (2002) [5] 3. Experimental Study Size: Hydraulic diameter of microchannel: Working Fluid: Deionized water seeded with fluorescent polystyrene particles at a particle density of 0.025%

  9. Asai (1991) [6] 3. Experimental Study Size: Chamber: Heater: Thin film of Working Fluid: Methanol

  10. Factors affect the bubbles nucleation and growth 3. Experimental Study • Effects of input voltage • Effects of pulse duration • Effect of initial liquid temperature

  11. Effects of input voltage 3. Experimental Study a weak linear dependency empirical equation: Fig. 2. Temperature at the phase of nucleation and vapor sheet formation as a function of input voltage, Hong et al (2004) [2]

  12. Effects of pulse duration 3. Experimental Study • Pulse duration time increases with applied voltage • There is a maximum bubble size Fig. 3. Effect of pulse duration on the bubble size Hong et al (2004) [2]

  13. Effect of initial temperature 3. Experimental Study For a given heat flux, the liquid reaches the nucleation temperature more rapidly for higher initial liquid temperatures Fig. 4 Bubble size as a function of time at different ambient temperature, Hong et al (2004) [2]

  14. Thermal model: 4. Numerical Simulation[7] Before the nucleation: IC: BC: After the nucleation: BC: (heater ); (liquid ); (bubble surface ).

  15. Bubble pressure 4. Numerical Simulation Clausius-Clapeyron equation Where, pamb is ambient pressure; KB is the Boltzmann’s constant. L is the latent heat of vaporization

  16. Fluid model 4. Numerical Simulation BC: no slip boundary condition on a the rigid wall slip boundary condition on a nonadhering surface

  17. Computational results Fig. 5. Velocity vector fields in the liquid taken from a y_z plane with x = 0at (i) t = 0.1 ,(ii) t = 2.4 Hong et al (2004) [7] 4. Numerical Simulation Simulation parameters: Size: V0=36V; t = 3.1 Ti,film = 223

  18. Computational results Fig. 5. Velocity vector fields in the liquid taken from a y_z plane with x = 0at (i) t = 3.4 ,(ii) t = 4.1 Hong et al (2004) [7] 4. Numerical Simulation

  19. Computational results Fig. 5. Velocity vector fields in the liquid taken from a y_z plane with x = 0at (i) t = 4.9 ,(ii) t = 5.9 Hong et al (2004) [7] 4. Numerical Simulation

  20. Working Principle[8] 5.Application – Microinjector The bubble formed under the heater forms a virtual chamber neck, which blocks the unwanted liquid movements Fig.6 Principle of microinjector

  21. Working Principle[8] 5.Application – Microinjector Fig.6 Principle of microinjector

  22. Fabrication[9] 5.Application – Microinjector Fig.7 Fabrication process flow

  23. Fabrication[9] 5.Application – Microinjector Fig.8 Nozzle in a microinjector Fig.9 Microchamber structure

  24. Characteristics of microinjector[9] 5.Application – Microinjector • It can work at a frequency over 35 kHz, at least 3 times higher than those of commercial counterparts; • The ink-jet printer using it can provide high-spatial resolution, maximum is 1700 dpi • The driving energy is low, around 30 J/cycle ;

  25. 6.Conclusions • Bubble growth and collapse are very important in the research of surface tension related micro devices; • Experimental studies found bubble generation, life time and size relate to applied voltage, pulse duration and initial liquid temperature; • Given the initial condition and boundary, bubble growth process can be simulated by the thermal and fluid model introduced; • Ink-jet printer using microinjector is very successful.

  26. Reference 1. Shiming Yang. Heat transfer. High Education Press, Beijing, 1987 2. Y.Hong, N. Ashgriz, J.Andrews. Exprerimental study of bubble dynamics on a micro heater induced by pulse heating. Journal of Heat Transfer-ASME, Vol.126, 2004, pp259-271 3. Z. Yin, A.Prosperetti, J. Kim. Bubble growth on an impulsively powered microheater. International Journal of heat and mass transfer. Vol.47, 2004, pp1053-1067 4. Jung-Yeop Lee, Hong-Chul Park, et al. Bubble nucleation on micro line heaters. Journal of heat transfer. Vol.125, 2003, pp687-702 5. E.N. Wang, S. Devasenathipathy, C.H. Hidrovo, D.W. Fogg, J.-M. Koo, J.G. Santiago, K.E. Goodson, T.W. Kenny. “A Quantitative Understanding of Transient Bubble Growth in Microchannels using µPIV” Hilton Head 2002: Solid-State Sensors & Actuator Workshop, June 2002, Hilton Head, South Carolina 6. A. Asai. Bubble dynamics in boiling under high heat flux pulse heating. Journal of heat transfer, Vol. 113, 1991, pp973-979 7. Yushik Hong, N. Ashgriz, et al. Numerical simulation of growth and collapse of a bubble induced by a pulse microheater. Journal of microelectromechanical systems. Vol. 13, N..5, 2004, pp 857-869 8. F.-G. Tseng, C.-J. Kim, C.-M. Ho, A High-Resolution High-Frequency Monolithic Top-shooting Microinjector Free of Satellite Drops-Part I: Concept, Design and Model. J. of MEMS, Vol.11,No.5, pp 427-436, Oct 2002 9. F.-G. Tseng, C.-J. Kim, C.-M. Ho, A High-Resolution High-Frequency Monolithic Top-shooting Microinjector Free of Satellite Drops-Part II: Fabrication, Implementation and Characterization, J. of MEMS, Vol.11,No.5, pp 437-447, Oct 2002

  27. Thank you! Questions ?

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