bottle2.gif Phase Change Laboratory

at Chung-Ang University (PCLCAU)  bottle2.gif

  

 

Phase Change Laboratory led by Professor Ho-Young Kwak has produced 13 Ph.Ds and 49 Masters since Professor Kwak has joined mechanical engineering faculty,Chung-Ang University in 1981. Currently 2 graduate students  are working at PCL. Educational background and professional career of Professor Kwak are as follows.

clipbrd.gif  Education

dot2_blu.gifB. S. in Physics,Seoul National University,Seoul,Korea, 1971

dot2_blu.gifM.A in Plasma Physics, TheUniversity ofTexas atAustin,USA, 1977

dot2_blu.gifPh.D in Mechanical Engineering(Fluid Dynamics), TheUniversity ofTexas atAustin, USA, 1981

 

clipbrd.gif Professional Career

 

dot2_blu.gif1981. 9 - 1986. 2

 Assistant Professor in Mechanical Engineering, Chung-Ang University

dot2_blu.gif1986. 3 - 1991. 2

 Associate Professor in Mechanical Engineering, Chung-Ang University

dot2_blu.gif1986. 12 - 1987. 6

 Visiting Professor, Cornell University, USA

dot2_blu.gif1991. 3 - Present

 Professor in Mechanical Engineering, Chung-Ang University

dot2_blu.gif1994. 9 - 1997. 2

 Vice Dean for Research Affairs, Chung-Ang University

dot2_blu.gif1996. 1 - 1997.12

 Editor for KSME Journal and KSME International Journal

dot2_blu.gif1997. 2 - 1999. 2

Dean of College of Engineering, Chung-Ang University

dot2_blu.gif2000. 1 - 2000.12

 Head for the Thermal Engineering Section in KSME

dot2_blu.gif2003 - 2010

 Cited in Who's Who in Science and Engineering (MARQUIS Who's Who)

dot2_blu.gif2002 - 2010

 Cited in Who's Who in the World (MARQUIS Who's Who)

dot2_blu.gif2003. 1 - 2004.12

 Chair, the Korea Section of ASME International

dot2_blu.gif2004. 1 -

Editorial Board Member of International Journal of Exergy

dot2_blu.gif2005. 11

 Namheon Award by KSME for contribution in Thermal Engineering Science

dot2_blu.gif2006. 3 - 2010. 8

 Director for Research Team of Application of Function Reinforced Materials, for Post BK21

dot2_blu.gif2006. 7 

Editor of Advances and Applications in Fulid Mechanics.

dot2_blu.gif2007

Cited in Who's Who in Asia (MARQUIS Who's Who)

dot2_blu.gif2009 -

 Cited in Who's Who in America (MARQUIS Who's Who)

dot2_blu.gif2010. 5

Thermal Engineering Award by KSME

dot2_blu.gif2010. 11-

Member of Korean Academy of Science and Technology

dot2_blu.gif2011. 9-

CAU Fellow

  

clipbrd.gif Contact

 

Mailing address : Mechanical Engineering Department,Chung-Ang University,Seoul, 156-756,Korea.

Tel : +82-2-820-5278

Fax : +82-2-826-7464

E-mail : kwakhy@cau.ac.kr

clipbrd.gif Research Topics 

    Bubble nucleation, bubble dynamics, sonoluminescenal phenomena, nucleate boiling heat transfer and cooling electronic equipment by phase change have been our major research topics sudied at PCL past 29 years or so. Sucesses in the formulation of general exergy balance and exergy cost-balance equations, which can be applicable to any component of thermal system gave motivation to study on the design and economic evaluation of thermal system at PCL. Syntheses of specialty nano materials under multi-bubble Sonoluminescence condition and micro actuator design are underway. Brief summary of our previous achievement and current research interests are as follows.

 

      clipbrd.gifMajor Contribution in Research (2014. 7)

 

dot2_blu.gifBubble Nucleation and Dynamics

1. Gas bubble formation in non-equilibrium water-gas solution, Journal of Chemical Physics, vol. 78, pp.5795-5799, 1983 (Citations: 35)

2. Tensile strength of simple liquids predicted by a model of molecular interaction, Journal of Physics D, Applied Physics, vol.18,pp.647-659,1985(Citations : 48)

3. Homogeneous bubble nucleation predicted by a molecular interaction model, ASME Journal of Heat Transfer, vol.113, pp.714-721,1991(Citations: 33)

4. Bubble dynamics on the evolving bubble formed from a droplet at the superheat limit, International Journal of Heat and Mass Transfer, vol.38, pp. 1709-1718, 1995 (Citations: 18)

5. Homogeneous nucleation and macroscopic growth of gas bubble in organic solutions, International Journal of Heat and Mass Transfer, vol.41, pp. 757-767, 1998 (Citations: 32)

6. Transient characteristics of a two-phase thermosyphon loop for multichip modules, ETRI Journal, vol. 20, pp. 284-289, 1998 (Citations: 10)

7. A model of homogeneous bubble nucleation of CO bubbles in Fe-C-O melts, Journal of Colloid and Interface Science, vol. 198, pp.113-118,1998 (Citations: 9)

8. A model of bubble nucleation on a micro line heater, ASME Journal of Heat Transfer, vol.121, pp.220-225, 1999 (Citations: 10)

9. A study of bubble behavior and boiling heat transfer enhancement under electric field, Heat Transfer Engineering, vol. 21 pp. 33-34, 2000 (Citations: 9)

10. Experimental study on closed-loop two-phase thermosyphon device for cooling MCMs, Heat Transfer Engineering, vol. 22, pp. 29-39, 2002 (Citations: 11)

11. Bubble nucleation of micro line heater, ASME Journal of Heat Transfer, vol. 125, pp. 687-692, 2003 (Citations: 8)

12. Bubble nucleation on micro line heaters under steady or finite pulse of voltage input, International Journal of Heat and Mass Transfer, vol. 46, pp. 3897-3907, 2003 (Citations: 13)

13. A model of laser-induced cavitation, Japanese Journal of Applied Physics, vol.43, pp.621-630, 2004 (Citations: 17)

14. Bubble evolution and radiation mechanism for laser-induced collapsing bubble in water, Japanese Journal of Applied Physics, vol. 43, pp.6364-6370, 2004 (Citations: 13)

15. Bubble nucleation and growth in polymer solutions, Polymer Engineering and Science, vol. 44, pp.1890-1899 , 2004 (Citations: 12)

16. Gas-vapor bubble nucleation--a unified approach, Journal of Colloid and Interface Science, vol. 278, pp. 436-446, 2004 (Citations: 10)

17. Explosive boiling of liquid droplets at their superheat limits, Chemical Engineering Science, vol. 60, pp.1809-1821, 2005 (Citations: 9)

18. Effect of surface condition on boiling heat transfer from silicon chip with submicron-scale roughness, International Journal of Heat and Mass Transfer, vol. 49, pp. 4543-4551, 2006 (Citations: 23)

19. Fabrication and testing of bubble powered micropumps using embeded microheater, Microfluidics and Naofluidics vol. 3, pp. 161-169, 2007 (Citations: 15)

20. Separation of microparticles and biological cells inside an evaporating droplet using dielectrophoresis, Analytical Chemistry, vol. 79, pp. 5087-5092, 2007 (Citations: 23)

21. Forced convective heat transfer of nanofluids in microchannels, International Journal of Heat and Mass Transfer, vol. 52, pp. 466-472, 2009 (Citations: 76)

dot2_blu.gifSonoluminescence Phenomena

1. An aspect of sonoluminescence from hydrodynamic theory, Journal of Physical Society of Japan, vol. 64, pp. 1980-1995 (Citations: 62)

2. Hydrodynamic solutions for a sonoluminescing gas bubble, Physical Review Letters, vol. 77, pp. 4454-4457, 1996 (Citations: 63)

3. Physical processes for a single bubble sonoluminescence, Journal of Physical Society of Japan, vol. 10, pp.3074-3083, 1997 (Citations: 43)

4. Shock pulse from a sonoluminescencing gas bubble, Journal of Physical Society of Japan, vol. 60, pp. 2537-2540, 1997 (Citations: 10)

5. Radiation mechanism for a single bubble sonoluminescence, Journal of Physical Society of Japan, vol. 69, pp.112-119, 2000 (Citations: 10)

6. Gravitational collapse of Newtonian stars, International Journal of Modern Physics D, vol. 9, pp. 35-42, 2000 (Citations: 14)

7. Radius measurement of a sonoluminescing gas bubble, Japanese Journal of Applied Physics, vol. 39, pp. 1124-1127, 2000 (Citations: 10)

8. Bubble dyanmics for single bubble sonoluminescence, Journal of Physical Society of Japan, vol. 70, pp. 2909- 2917, 2001 (Citations: 12)

9. Possibility of upscaling for single bubble sonoluminescence at a low driving frequency, Journal of Physical Society of Japan, vol. 72, pp. 509-515, 2003 (Citations: 8)

10. Degradation of methylene blue under multibubble sonoluminescence condition, Journal of Photochemistry and Photobiology A: Chemistry, vol. 175, pp. 45-50, 2005 (Citations: 24)

11. CdS coating on TiO2 nanoparticles under multibubble sonoluminescence condition, Bulletin of Korean Chemical Society, vol. 26, pp. 1759-1581, 2005 (Citations: 21)

12. Characteristics of sonoluminescing bubble in aqueous solutions of sulfuric acid solution, Journal of Physical Society of Japan vol. 75, 114705, 2006 (Citations: 10)

13. Preparation of Li4Ti5O12 nanoparticles by a simple sonochemical method, Dalton Transations, vol. 37, pp. 4182-4184, 2007 (Citations: 22)

14. Syntheses of ZnO and ZnO-coated TiO2 nanoparticles in various alcohol solutions at multibubble sonoluminescence (MBSL) condition, Chemical Engineering Journal, vol. 135, pp. 168-173, 2008 (Citations: 12)

15. Homogeneous ZnS coating onto TiO2 nanoparticles by a simple one pot sonochemical method, Chemical Engineering Journal, vol. 139, pp. 194-197, 2008 (Citations: 18)

16. Preparation of supported Ni catalysts with a core/shell structure and their catalytic tests of partial oxidation of methane, International Journal of Hydrogen Energy, vol. 34, pp. 3351-3359, 2009 (Citations: 32).

17. Preparation of supported Ni catalysts on various metal oxides with core/shell structures and their tests for the steam reforming of methane, Chemical Engineering Journal, Vol. 168, pp. 775-783, 2011 (Citations : 22).

18. Catalytic test of supported Ni catalysts with core/shell structure for dry reforming of methane, Fuel Processing Technology, Vol. 92, pp. 1236-1243, 2011 (Citations : 28).

.dot2_blu.gifExergetic and Thermoeconomic Analysis of Thermal Systems

1. Exergy analysis for a gas turbine cogeneration system, ASME Journal of Engineering for Gas Turbine and Power, vol. 118, pp. 782-791 1996(Citations: 26)

2. Exergoeconomic analysis of thermal systems, Energy, vol. 23, pp. 393-406, 1998 (Citations: 48)

3. Exergoeconomic analysis of gas turbine cogeneration systems, Exergy International Journal, vol. 1, pp. 31-40, 2001 (Citations: 18)

4. Exergetic and thermoeconomic analysis of power plant, Energy, vol. 28, pp.343-406, 2003 (Citations: 62)

5. Cost structure of CGAM cogeneration system, International Journal of Energy Research, vol. 28, pp. 1145-1158, 2004 (Citations: 19)

6. Exergetic and thermoeconomic analysis of a 200 kW phosphoric acid fuel cell plant, Fuel, vol. 83, pp. 2087-2094, 2004 (Citations: 14)

7. Economic evaluation for adoption of cogeneration system, Applied Energy, vol.84, pp. 266-278, 2007 (Citations: 21)

8. Optimal planning and economic evalution of cogeneration system, Energy, vol. 32, pp. 760-771, 2007 (Citations: 29)

9. Economic optimization of a cogeneration system for apartment houses in Korea, Energy and Buildings, vol. 40, pp. 961-967, 2008 (Citations: 15)

10. Optimal operation of a 1-kW PEMFC-based CHP system for residential applications, Applied Energy, Vol. 95, pp. 93-101, 2012 (Citations: 13)

           

clipbrd.gif Research Members 

  dot2_blu.gif Professor Ho-Young Kwak (kwakhy@cau.ac.kr)

 dot2_blu.gif Jaekyun Oh (DR/3)             (jakeoh@chol.com)

 dot2_blu.gif Yungpil Yoo (MA/4)            (newreality@naver.com)

 

  

   
   
   

 



 

  dot1_yell.gif  Bubble Nucleation in Liquid

  dot1_yell.gif Bubble Dynamics and Sonoluminescence Phenomena

 

book1.gifBubble Nucleation in Liquids

Classical bubble nucleation theory, originally proposed by W. Gibbs assumes the formation of the critical size bubble. This theory fails to predict the amount of decompression for gaseous bubble formation in water-gas solutions. It also fails to predict the tensile strength of liquids. In addition, the classical theory gives no information about the evaporation intensity at the superheat limit.

Using a new surface energy for the formation of the critical cluster(Molecular Cluster Model), models for the gas bubble formation in gas-liquid solution[1] and for the vapor bubble formation within a liquid under tension[2,3] were proposed. Our cluster model for bubble nucleation can descripe correctly the evaporation phenomena at the superheat limit[3]. How a critical cluster grows to become a critical size bubble in gas-liquid solutions was also theorized[4,5]. The cluster model of bubble nucleation may be applied to CO bubble formation in iron-melt system characterized with high surface tension and low vapor pressure[6] and the bubble formation on a cavity free surface[7,8,9,10]. Recently the superheat limit of hydrocarbons and their mixtures were measured precisely by using the droplet explosion technique with visualization. The dynamic behavior of the bubble formed from the fully evaporated droplet at its superheat limit was also investigated by measuring the far field pressure signal from the bubble [11]. We reformulated the cluster model for the bubble formation due to dissolved gas molecules and activated vapor molecules in a unified way [12]. Thermal as well as quantum nucleation of bubbles and the cross-over from thermal to quantum regime in liquid helium under negative pressure near the absolute zero temperature was investigated by using the molecular cluster model based as theLondon dispersion force between molecules [13]. In addition, it was found that the "molecular culster model" for the bubble formation could be extended to predict the laser-induced cavitation which has become important in the field of laser mediated surgery [14] and gaseous bubble nucleation events in elastomers, polymers and polymer solutions [15], which is very important in polymer processing [16] to produce foamed materials and microcellular plastics. A bubble-powered micropump which consists of two-parallel microline heaters, and a pair of nozzle-diffuser flow controller was fabricated and tested [17]. We found that the mechanism of the light emission from the laser-induced bubble at its first collapse might be due to the black body radiation [18]. More work will be done on the bubble nucleation and growth on a cavity free micro heaters, which could evolutionize the designs and applications of thermal micromachines. Recently, we have reported how gaseous bubble nucleation occurs under shear flow[19]. An effort to understand the absolute metastable limit of liquid was alos tried based on our bubble nucleation model[20]. A review of our bubble nucleation model appears in an entry of 2nd edition of Encyclopedia of Surface and Colloid Science published in 2006 [21]. Explosive boiling processes on the surfaces of nanoparticles irradiated using a  high-power laser have been studied for use in medical applications, such as cellular surgery and photo-thermal killing of cells. Recently, detailed theoretical study on nucleation and subsequent evolution of bubbles on the surfaces of nanoparticles irradiated using a high-power laser has been done in PCLCAU [22].

 

[1] Ho-Young Kwak, R.L. Panton, "Gas bubble formation in non-equillibrum water-gas solutions," Journal of Chemical Physics. Vol. 78. pp.5795-5799, 1983.

[2] Ho-Young Kwak, R.L. Panton, "Tensile strength of simple liquids predicted by a model of molecular interactions," Journal of Physics, D, Applied Physics, Vol. 18, pp. 647-659, 1985.

[3] Ho-Young Kwak, Sangbum Lee,"Homogeneous bubble nucleation predicted by a molecular interaction model," ASME Journal of Heat Transfer, Vol.113, pp. 714-721, 1991.

[4] Ho-Young Kwak, "Homogeneous bubble nucleations," Applied Mechanics Review, Vol. 43, pp.164-165, 1990.

[5] Ho-Young Kwak, Yong W. Kim, "Homogeneous nucleation and macroscopic growth of gas bubble in the organic solutions," International Journal of Heat Mass Transfer, Vol. 41, pp. 757-767, 1998.

[6] Ho-Young Kwak, Si-Doek Oh, "A model of homogeneous bubble nucleation of CO bubble in Fe-C-O melts," Journal of Colloid and Interface Science, Vol. 198, pp.113-118, 1998.

[7] Si-Doek Oh, Sam-Sun Seung, Ho-Young Kwak, " A model of bubble nucleation on a micro line heater," ASME Journal of Heat Transfer, Vol. 121, pp. 220-225, 1999.

[8] Jung-Yeop Lee, Hong-Chul Park, Jung-Yeul Jung, and Ho-Young Kwak, "Bubble nucleation on micro line heaters," ASME Journal of Heat Transfer, Vol. 121, pp. 687-692, 2003.

[9] Jung-Yeul Jung, Jung-Yeop Lee, Hong-Chul Park, and Ho-Young Kwak, "Bubble nucleation on micro heaters inder steady or finite pulse of voltage input," International Journal of Heat and Mass Transfer, Vol. 46, pp. 3897-3907, 2003.

[10] Jung-Yeul Jung and Ho-Young Kwak, "Bubble nucleation and behavior on micro square heaters," Nanoscale and Microscale Thermophysical Engineering, Vol. 10, pp. 95-107, 2006. (featured on the issue cover)

[11] Hong-Chul Park, Ki-Taek Byun, and Ho-Young Kwak, "Explosion boiling of liquid droplets at their superheat limits," Chemical Engineering Science, Vol. 60, pp. 1809-1821, 2005.

[12] Ho-Young Kwak, and Si-Doek Oh, "Gas-vapor bubble nucleation; An unified approach," J. of Colloid and Interface Science, Vol. 278, pp. 436-446, 2004.

[13] Ho-Young Kwak, Jung-Yeul Jung and Jae-Ho Hong, "Quantum nucleation of bubbles in liquid heliums," J. Phys. Soc. Jpn., Vol. 71, pp. 2186-2191, 2002.

[14] Ki-Taek Byun, and Ho-Young Kwak, "A model of laser-induced cavitation," Jpn. J. Appl. Phys., Vol. 43, pp. 621-630, 2004.

[15] Seong Lin Karng, Ki Young Kim, and Ho-Young Kwak, "Bubble nucleation and growth in polymer solutions," Polymer Engineering and Science, Vol. 44, pp. 1890-1899, 2004.

[16] Ki Young Kim, Sung Lin Kang, and Ho-Young Kwak, "Generationof microcellular foams by supercritical carbond dioxide in a PMMA compound," International Polymer Processing, Vol. 23, pp. 8-16, 2008.

[17] Jung-Yeul Jung and Ho-Young Kwak, "Fabrication and testing of bubble-powered micropumps using imbedded microheater," Microfluidics and Nanofluidics, Vol. 3, pp. 161-169, 2007.

[18] Ki-Taek Byun, Ho-Young Kwak, and Sarng Woo Karng, "Bubble evolution and radiation mechanism for laser-induced collapsing bubble in water," Jpn. J. Appl. Phys., Vol. 43, pp. 6364-6370, 2004.

[19] Ho-Young Kwak and Ki-Moon Kang, " Gaseous bubble nucleation under shear flow," International Journal of Heat and Mass Transfer, Vol. 52, pp.4729-4937, 2009.

[20] Ho-Young Kwak Ki-Moon Kang and Ilgon Ko, "The absolute metastable limit of liquids under tension --- A review," Journal of Mechanical Science and Technology, Vol. 25, pp. 863-869, 2011.

[21] Ho-Young Kwak, Bubbles: Homogeneous nucleation, in Encyclopedia of Surface and Colloid Science, 2nd Edition, pp. 1048-1071, CRC Press, 2006.

[22] Ho-Young Kwak, Jaekyoon Oh, Yungpil Yoo, Shahid Mahmood, Bubble formation on the surface of laser-irradiated nano-sized particles, Journal of Heat Transfer, Vol. 136, pp. 081501-1~081501-9, 2014.

book1.gifBubble Dynamics and Sonoluminescence Phenomena

  Understanding of the behavior of bubble inside liquid is not a simple problem. The full hydrodynamic problem for the bubble motion involves solving 3-D Navier-Stokes equations inside and outside the bubble, coupled with equations of heat and mass transfers at the bubble wall. We have solved this problem without massive computational work! A breakthrough came by finding the analytical solution of the mass and momentum equations in spherical symmetry [23]. The conservation equations in spherical symmetry are given as

                                (1)

              (2)

where r  is the distance from center, is the gas density  is the gas velocity which obeys  . A set of solutions satisfying Eqs. (1) and (2) are [24]

                                                   (3)

                                                        (4)

                          (5)

where and .
  The constant a is related to the gas mass inside the bubble. With uniform density and pressure approximation, the violent oscillation of the bubble formed from the evaporated droplet at the superheat limit could be accounted [25]. The bubble behavior of a nonsonoluminescencing gas bubble can be described correctly by the solutions with uniform pressure approximation [23]. However, the gas pressure inside bubble is no longer uniform if the bubble wall acceleration exceeds 10
12 m/s2. The solutions for 3-D Navier-Stokes equations in spherical symmetry show that sonoluminescence occurs due to the rapid increase and subsequent decrease in the bubble wall acceleration which induces a thermal spike [24,26]. The temperature profile obtained by the solutions suggests that the light pulse duration is less than 300 ps [26]. Also the solutions have revealed that the Guderley's similarity solution is not valid just prior to the collapse [26]. In addition correct spectral behavior of sonoluminescence was obtained by assuming that the source for the sonoluminescence is bremsstrahlung in partially ionized gases [24,26]. The shock pulse emanating form a sonoluminescing gas bubble were calculated [27], measured [28] and the propagation of a pressure wave inside bubble near the bubble collapse [28,29] have also been calculated by using the solutions.

It has been found that there always exists a mismatch between the natural frequency of an oscillator (bubble) and the characteristic frequency of the applied ultrasound, so that a proper choice of time scale of the driving force is crucial for the calculation of the bubble behavier under ultrasound [30,31]. It has also been found experimentally that the upscaling of SBSL cannot be achieved at low frequencies of ultrasound due to such mismatch [32]. An artificial resonance may occur in the course of numerical evaluation of the equation for bubble motion under ultrasound if the bubble motion is forced to be in phase with the characteristic frequency of the driving force. Two time normalization method [30] was introduced to avoid the artificial resonance. Of course the two time normalization method introduced by us is a physical approximation which represents lagging behavior of bubble motion under ultrasound. Such relaxational motion of bubble, which is typical for nonlinear oscillators [33], turns out to be due to the combined effect of surface tension and viscosity of liquid. This method enables to explain why a sonoluminescing air bubble can be maintained at partial pressure of about 0.03~0.14 atm [34] and why the sonoluminescing air bubble can be stable at the driving pressure of 1.45 atm [35].

Recently, our theory predicts that extremely high temperature above million degree might be achieved from a submicron sonoluminescing gas bubble driven at 1 MHz [36]. This happens because the submicron bubble driven at MHz frequency can be stable even at higher driving pressure above 10 atm [36]. Even our theoretical model predicts correctly the nonlinear behavior of bubble in sulfuric acid solutions, which shows two states of bubble motion [37] and the characteristics of a sonoluminescing gas bubble such as the peak pressure and temperature and the flash width [38] in those solutions. Our theory will be used as a tool for optimum design of sonochemical reactors. [39]

Exact solution of the cosmological fluid equations for Newtonian stars, which yields many fruitful results such as stellar stability, spherical oscillation and gravitational collapse [40] was obtained by using the linear velocity profile given in Eq. 4. The velocity profile obtained shows homologous character of the gases inside the sphere: every mass point during the collapse or expansion may be traced back to a single point. Furthermore, the exact solution yields to calculate central densities, pressures and temperatures of the Newtonian stars such as the Sun, Jupiter and the Saturn [41]. Our calculation results may be applicable to the formation of protostars. Using these exact solution of the cosmological fluid equations, fire-ball expansion and subsequent shock wave propagation by detonation of explosives were studied recently [42].

Experimental works on the single bubble sonoluminescence(SBSL) have also been done at PCL. It has been found that a selective bifurcation instead of period doubling occurs when the driving pressure is increased and the bubble gains extreme stability (SL state) after the cascade occurrence of such bifurcation [43]. Accurate measurement of the radius of a sonoluminescing gas bubble by light scattering method and direct imaging technique was tried [44] by using the remarkable stability of sonoluminescing gas bubble having the same shape variation sequence in every oscillation cycle and having only 50 ps jitter in the time flashes. Such SBSL characteristics enable to measure the bubble radius by the light scattering method and direct imaging tenique sequentially. The spectrum from SBSL was measured and the observed results were compared with the results by the theory proposed [24,26]. Calculated and experimental results yield common spectral behavior in the visible region : the spectral radiance shows power-law dependence on wavelength with an exponent of -2.5 [45].

Recently we have succeded in measuring the pulse width from the sonoluminescing gas bubble in sulfuric acid solutions [46] and glycerin-water mixtures [47], where the SL bubble is extremly unstable. The measured values of the pulse widht were found to be in the range of 150 ps to several ns [46,47]. No appreciable difference in the measured pulse width [48] and the bubble behavior [49] for the sonoluminescing air bubble in various solutions was found. The measured results for the pulse width of  sonoluminescence in various solutions whose density varied from 1000 kg/m3 to 1800 kg/m3 suggest that light is emitted from the core region where the temperature is almost uniform [47].

Application of sonoluminescence phenomena such as possibility of bubble fusion and the chemical reaction enhanced by multibubble sonoluminescence are underway. For example, degradation of Methylene blue, a typical textile dyestuffs in aqueous solution was examined for the first time at the multibubble sonoluminescence (MBSL) condition [50]. At the optimum condition of MBSL, the solution was degradated completely. Recently, uniform coating on CdS particles on TiO2 nanoparticles[51] was succeeded through a one pot reaction under MBSL condition. Zinc oxide(ZnO) and ZnO-coated tintanium nanoparticles were synthesized in various alcohol solution[52] at the MBSL condition.  Furthermore, Li4Ti5O12(LTO), a powerful anode material for all kids of rechargeable lithium batteries was systhesized by heating the LiOH coated TiO2 nanoparticles prepared at the MBSL condition[53].

We also synthesized the nanoparticles with core/shell structure such as ZnS coating on to TiO2 nanoparticles [54] and PbS coating on TiO2 nanoparticles [55] at the MBSL condition. Specially we prepared the supported Ni catalysts with core/shell structure at the MBSL condition and found that 10% Ni Ni/Al2O3 catalysts of core/shell structure produced good conversion efficient of CH4, which is about 96% at reaction temperature of 800 and showed good thermal stability [56]. With the supported Ni catalysts Ni/Al2O3 and Ni/MgO-Al2O3 synthesized at the MBSL conditions, the methane conversion of 97% in steam reforming reation at 750 [57] and 95% in dry (CO2) reforming reaction at 800 [58] were achieved for the first 150h. A test for the mixed reforming of methane with these catalysts was also done [59]. Recently, the pulse width from a bubble cloud under MBSL conditions was measured for the first time [60]. The observed pulse width which appears to be comparable to that of the single bubble sonolunimescence indicates that the cloud of bubbles collapse simultaneously to emitting a light that is synchronized with th applied ultrasound. Based on this observation, MBSL is studied hydro-dynamically to obtain the velocity profile and radiation pressure field by solving the continuity and momentum equations for a spherical cluster containing numerous microbubbles[61]. Molecular dynamics simulation for the sonoluminescing gas bubble [62] with ten million molecules is in progress with supercomputer facility at KISTI (Korea Institute of Science and Technology Information), Daejon, Korea. An appropriate boundary condition at the bubble wall was found to be one of important factor to simulate the sonoluminescing bubble by molecular dynamics [63].

[23] Ho-Young Kwak and Hyup Yang, "An aspect of sonoluminescence from hydrodynamic theory," Journal of Physical Society of Japan, Vol. 64, pp. 1980-1992, 1995.

[24] Ho-Young Kwak and Jung Hee Na, "Hydrodynamic solutions for a sonoluminescing gas bubble," Physical Review Letters, Vol. 77, pp. 4454-4475, 1996.

[25] Ho-Young Kwak, Si-Doek Oh and Cheon-Ho Park, "Bubble dynamics for the evolving bubble formed from the droplet at the superheat limit," International Journal of Heat Mass Transfer, Vol. 38, pp. 1709-1718, 1995.

[26] Ho-Young Kwak and Jung Hee Na, Physical process for single bubble sonoluminescence," Journal of Physical Society of Japan, Vol. 66, pp. 1101-1110, 1997.

[27] Yoon-Pyo Lee, Sarng-Woo Karng, Jin-Seok Jeon and Ho-Young Kwak, "Shock pulse from a sonoluminesceing gas bubble," Journal of Physical Society of Japan, Vol. 66, pp. 2537-2540, 1997.

[28] Sarng Woo Karng, Yoon Pyo Lee, Ki Young Kim, and Ho-Young Kwak, "Implosion mechanism for a sonoluminescing gas bubble," Journal of the Korean Physical Society, Vol. 43, pp. 135-144, 2003.

[29] Ho-Young Kwak, Yoon-Pyo Lee and Sarng-Woo Karng, Pressure wave propagation inside a sonoluminescing gas bubble," Journal of Physical Society of Japan, Vol. 68, pp. 705-708, 1999.

[30] Ho-Young Kwak, Joong-Yeob Lee and Sarng Woo Karng, "Bubble dynamics for single bubble sonoluminescence," Journal of Physical Society of Japan, Vol.70, pp.2909-2917, 2001.

[31] Sarng Woo Karng and Ho-Young Kwak, "Relaxation behavior of microbubbles in ultrasonic field," Japanese Journal of Applied Physics, Vol. 45, pp. 317-322, 2006.

[32] Jin-Seok Jeon, Joong-Yeob Lee and Ho-Young Kwak, "Possibility of upscaling for single bubble sonoluminescence at a low driving frequency", Journal of Physical Society of Japan, Vol.72, pp. 509-515, 2003.

[33] Sarng Woo Karng, Ki Young Kim, and Ho-Young Kwak, "Lagging motion of forced nonlinear oscillators," Journal of Sound and Vibration, Vol. 287, pp. 117-128, 2005.

[34] Jung-Hee Na, Gi-Taek Byun, and Ho-Young Kwak, 'Diffusive stability for a sonoluminescing gas bubble," Journal of the Korean Physical Society, Vol. 42, pp. 143-152, 2003.

[35] Ho-Young Kwak, Sarng-Woo Karng and Yoo-Pyo Lee, "Rayleigh-Taylor instability on sonoluminescing gas bubble," Journal of the Korean Physical Society, Vol. 46, pp. 951-962, 2005.

[36] Ki-Taek Byun, Sarng Woo Karng, Ki Young Kim and Ho-Young Kwak, "Sonoluminescence characteristics from micron and submicron size bubbles," Journal of the Korean Physical Society, Vol. 47, No. 6, 2005.

[37] Ki Young Kim and Ho-Young Kwak, Prediction of bubble behavior in sulfuric acid solutions by a set of solutions of Navier-Stokes equations, Chemical Engineering Science, Vol. 62, pp. 2880-2889, 2007.

[38] Ki Young Kim, Ki-Taek Byun and Ho-Young Kwak, Characteristics of sonolunescing bubbles in aqueous solutions of sulfuric acid, Journal of Physical Society of Japan, Vol. 75, No. 11, 2006.

[39] Ki Young Kim, Ki-Taek Byun, and Ho-Young Kwak, Temperature and pressure fields due to collapsing bubble under ultrasound," Chemical Engineering Journal, Vol. 131/132, pp. 125-135,  2007.

[40] Jung Whan Jun and Ho-Young Kwak, "Gravitational collapse of Newtonian stars", International Journal of Modern Physics D, Vol. 9, pp. 35-42, 2000.

[41] Ho-Young Kwak and Jung Whan Jun, "Hydrodynamics and thermodynamics of Newtonian stars," Geophys. Astrophys. Fluid Dynamics, pp. 1-14. 2003.

[42] Ho-Young Kwak, Ilgon Ko and Ki-Moon Kang, Expanding of fire-ball and subsequent shock wave propagation by detonation of explosives," International Journal of Thermal Sciences, Vol. 59, pp. 9-16, 2012..

[43] Byung-Rock Kim, Jin Seok Jeon and Ho-Young Kwak, "Stability and selective bifurcation for a gas bubble oscillating under ultrasound", Journal of Physical Society of Japan, Vol. 68, pp. 1197-1204, 1999.

[44] Jin-Seok Jeon, Ik-Jun Yang, Sarng Woo Karng and Ho-Young Kwak, "Radius measurement of a microbubble oscilliating under ultrasound", Japanese Journal of Applied Physics, Vol.39, pp. 1124-1127, 2000

[45] Jin-Seok Jeon, Ik-Jun Yang, Jung Hee Na and Ho-Young Kwak, "Radiation mechanism for a single bubble sonoluminescence," Journal of Physical Society of Japan, Vol. 69, pp. 112-119, 2000.

[46] Jin-Seok Jeon, Chansoo Lim and Ho-Young Kwak, "Measurement of pulse width of sonoluminescing gas bubble in sulfuric acid solution," Journal of the Physical Society of Japan, Vol. 77, Paper # 033703, 2008.

[47] Chansoo Lim, Jin-Seok Jeon and Ho-Young Kwak, " Pulse width measurements for sonoluminescing gas bubble in various solution," Europhysics Letters, Vol. 86, Paper # 17002, 2009.

[48] Jin-Seok Jeon, Chansoo Lim, Ilgon Ko and Ho-Young Kwak, " Pulse width measurement of sonoluminescing air bubble in various solution using a time-correlated single photon counting technique," Submitted for publication, 2009.

[49] Chansoo Lim, Jeong Eun Kim, Jae Young Lee and Ho-Young Kwak, " Nonlinear behavior of micro bubble under ultrasound due to heat transfer," Journal of Mechnical Science and Technology, in press, 2009.

[50] Ki-Taek Byun and Ho-Young Kwak, "Degradation of Methylene blue under multibubble sonoluminescence," Journal of Photochemistry and Photobiology, Vol. 175, pp. 45-50, 2005.

[51] Seong Soo Lee, Kook Won Seo, Seok Hwan Yoon, Il-Wun Shim, Ki-Taek Byun and Ho-Young Kwak, "CdS coating on TiO2 nanoparticles under multibubble sonoluminescence condition," Bulletin of the Korean Chemical Society, Vol. 26, pp. 1579-1581, 2005.

[52] Ki-Taek Byun, Kook Won Seo, Il-Wun Shim, and Ho-Young Kwak," Syntheses of ZnO and ZnO-coated nanoparticles in various alcohol solutions at multibubble sonoluminescence (MBSL) condition, Chemical Engineering Journal, Vol. 132, pp. 125-135, 2007.

[53] Seung Soo Lee, Ki-Taek Byun, Jong Pil Park, Sin Kyu Kim, Ho-Young Kwak, and Il-Wun Shim, "Preparation of Li4Ti5O12 nanoparticles by a simple sonochemical method," Dalton Transations, Vol. 37, pp. 4182-4184, 2007.

[54] Seung Soo Lee, Ki-Tack Byun, Jong Pil Park, Sin Kyu Kim, Joung Chan Lee, Suk-Kyu Chang, Ho-Young Kwak and Il-Wun Shim, " Homogeneous ZnS coating onto TiO2 nanoparticles by a simple one pot sonochmical method," Chemical Engineering Journal, Vol. 139, pp. 194-197, 2008.

[55] Sin Kyu Kim, Seung Soo Lee, Jong Pil Park, Jae Young Park, kang Min Ok, Ho-Young Kwak and Il-Won Shim," Coating of TiO2 nanoparticles with PbS- thin films and preparation of PbS nanoparticles using a one-pot sonochemical reaction," Thin Solid Films, Vol. 517, pp. 6663-6665, 2009.

[56] Hyo Won Kim, Ki Moon Kang and Ho-Young Kwak, " Preparation of supported Ni catalysts with a core/shell structure and their catalytic tests of partial oxidation of methane," International Journal of Hydrogen Energy, Vol. 34, pp. 3351-3359, 2009.

[57] Hyo-Won Kim, Ki-Moon Kang, Ho-Young Kwak and Jong Hyun Kim, Preparation of supported Ni catalysts on various metal oxides with core/shell structures and their tests for steam reforming of methane," Chemical Engineering Journal, Vol. 168, pp. 775-783, 2011.

[58] Ki-Moon Kang, Hyo-Won Kim, Il-Wun Shim and Ho-Young Kwak, Catalytic test of supported Ni catalysts with core/shell structure for dry reforming of methane," Fuel Processing Technology, Vol. 92, pp. 1236-1243, 2011.

[59] Ki-Moon Kang, Il-Wun Shim and Ho-Young Kwak, Mixed and autothermal reforming of methane with supported Ni catalysts with a core/shell structure," Fuel Processing Technology, Vol. 93, pp. 105-114, 2012.

[60] Ilgon Ko and Ho-Young Kwak, Measurement of pulse width from a bubble cloud under multibubble sonoluminescence conditions," Journal of the Physica Society of Japan, Vol. 79, Paper No. 124401, 2010.

[61] Shahid Mahmood, Yungpil Yoo, Jaekyoon Oh, Ho-Young Kwak, Hydrodynamic approach to multibubble sonoluminescence, Ultrasonics Sonochemistry, Vol. 21, pp. 1512-1518, 2014.

[62] Ki Young Kim and Ho-Young Kwak, and Jong Hyun Kim, Molecular dynamics simulation of collapsing phase for asonoluminescing gas bubble in sulfuric acid solutions : A comparative study with theoretical results, Journal of Physical Society of Japan, Vol. 76, Paper #024301, 2007.

[63] Ki Young Kim, Chansoo Im, Ho-Young Kwak, and Jong Hyun Kim, "Validation of molecular dynamics simulation for a collapsing gas bubble," Molecular Physics,  Vol. 106, pp. 967-975, 2008.

 

 

 
 

 

  dot1_yell.gif  Exergy and Thermoeconomic Analyses for Thermal Systems

  dot1_yell.gif  Nucleate Boiling Heat Transfer, Convective Heat transfer in Microchannels

 book1.gif Exergy and Thermoeconomic Analyses for Thermal Systems    

A general exergy balance equation [64] and the corresponding cost-balance equation [65] that are applicable to any component of thermal systems have been formulated. The exergy of material stream involved in the component of any thermal system was decomposed into thermal, mechanical and chemical exergy flows and an entropy-production flow. A unit exergy cost is assigned to each disaggregated exergy in the stream at any state. This methodology permits us to obtain a set of equations for the unit costs of various exergies by applying the cost-balance equation to each component of the system and to each junction. The monetary evaluations of various exergy costs as well as the production cost of thermal system are obtained by solving the set of equations. The lost costs of each component of the system can also be obtained by this method. Application to a 1000 kW gas turbine cogeneration system show that the unit exergy costs increase as the production process continues and that the production cost of electricity increase nearly proportional with the input cost [66].

The application of the proposed exergy and thermoeconomic analyses to 500-MW combined cycle plant [67] has revealed that the model provides the productive structure of the system considered, consequently could visualize the cost formation process and the productive interaction between components clearly. In the analyses, it has been found that the exergy and cost balance equations for the plant boundary play a crucial role for the determination of the production costs. A comparative study of thermoeconomic methodologies between the SPECO(Specific Cost) methodology proposed by Professor G. Tsatsaronis and our MOPSA(Modified Productive Structure Analysis) for the predefined CGAM cogeneration system has been done [66]. It has also been found that the unit cost of products is dependent on the chosen level of aggregation of the system only when one consider the entropy production rate as one of parameters to determine the unit cost of products, which suggest that the cost structure of energy system is interrelated by the irreversibilities occurred at each component [68,69]. Recently exergetic and thermoeconomic analysis were also performed for a 200-kW phosphoric acid fuel cell plant by using MOPSA and was found that the system might be viable economically when the initial investment cost per power is reduced to the level of the gas turbine co-generation plant of 1500 $/kW [70]. Recently optimal configuration and optimal operation condition of the cogeneration plant [69] and the economic evaluation of the plant [72] were determined by considering annual energy demand pattern of commercial building such as hotels and hospitals and apartments[73]. Recently thermoeconomic analysis was performed for the high-temperature gas-cooled reactors coupled with a steam methane reforming plant in order to estimate the hydorgen production cost [74].

Recently, optimal operation of PEMFC-based CHP system [75], a support strategy for the promotion of photovoltaic uses in Korea [76] and thermoeconomic analysis of ground-source heat pump system [77] were published with collaboration of researchers in Blue Economy Strategy Institute Co. Ltd. in Seoul Korea. Recently, a cost-effective method for integration of existing grids with new and renewable energy sources in public buildings in Korea was suggested [78]. A key factor of the method is based on the fact that the unit costs of the products from the energy systems depends on the capacity factor or the utilization factor which is crucially dependent on the interaction between the energy demand pattern for the building and the production time of the specific energy from the new and renewable energy sources

 

[64] Si-Doek Oh, Hyo-Sun Pang, Si-Moon Kim and Ho-Young Kwak, "Exergy analysis for a gas turbine cogeneration systems," Journal of Engineering Gas Turbines and Power, Vol. 118, pp. 782-791, 1996.

[65] Si-Moon Kim, Si-Doek Oh, Yong-Ho Kwon and Ho-Young Kwak, "Exeroeconomic analysis for thermal systems," Energy, Vol. 23, pp. 393-406, 1998.

[66] Yong-Ho Kwon, Ho-Young Kwak, Si-Doek Oh, "Exergoeconomic analysis of gas turbine cogeneration systems," Exergy; Int. J., Vol.1, pp.31-40, 2001.

[67] Ho-young Kwak, Duck-Jin Kim and Jin-Seok Jeon, "Exergetic and thermoeconomic analysis of power plant," Energy, Vol. 28, pp.  343-360, 2003.

[68] Ho-Young Kwak, Gi-Taek Byun, Yong-Ho Kwon and Hyup Yang, "Cost structure of CGAM cogeneration system," International Journal of Energy Research, Vol. 28, pp. 1145-1158, 2004.

[69] Ho-Young Kwak, Ki-Moon Kang, "Sensitivity analysis of component efficiencies on perfomance of a gas turbin cogeneration system," International Journal of Exergy, Vol. 9, pp. 337-345, 2011.

[70] Ho-Young Kwak, Hyun-Soo Lee, Jung-Yeul Jung, Jin-Seok Jeon and Dal-Ryung Park, "Exergetic and thermoeconomic analysis of a 200-kW phosphoric acid fuel cell plant," Fuel, Vol. 83, pp. 2087-2094, 2004.

[71] Si-Doek Oh, Ho-Jun Lee, Jung-Yeul Jung and Ho-Young Kwak, Optimal planning and economic evaluation of small scale cogeneration system," Energy, Vol. 33, pp.760-771, 2006.

[72] Si-Doek Oh, Hoo-Suk Oh and Ho-Young Kwak, Economic evaluation for adoption of cogeneration system," Applied Energy, Vol. 84, pp.266-278, 2007.

[73] Hyon Uk Seo, Jinil Sung, Si-Doek Oh, Hoo-Suk Oh, and Ho-Young Kwak, "Economic optimization of a cogeneration system for apartment houses in Korea," Energy and Buildings,Vol. 40, pp. 961-967, 2008.

[74] Duk Jin Kim, Jong Hyun Kim, K.F.Barry and Ho-Young Kwak, "Thermoeconomic analysis of high-temperature gas-cooled reactors with steam methane reforming for hydrogen production," Nuclear Technology, Vol. 176, pp. 337-351, 2011.

[75] Si-Doek Oh, Ki-Young Kim, Shuk_Bum Oh and Ho-Young Kwak, Optimal operation of a 1-kW PEMFC-based CHP system for residential applications, Applied Energy, vol. 95, pp. 93-101, 2012.

         [76] Si-Doek Oh, Yeji Lee, Yungpil Yoo, Jinoh kim, Suyong kim, Seung Jin Song and Ho-Young Kwak, A support strategy for the promotion of photovoltaic uses for residential houses in Korea, Energy Policy, vol. 53, pp. 248-256, 2013.

 

        [77] Ho-Young Kwak, Yungpil Yoo, Si-Doek Oh and Ha-Na Jang, Thermoeconomic analysis of ground-source heat pump systems, International Journal of Energy Research, Published online in Wiley Online Library, 2013.

 

 

        [78] Si-Doek Oh, Yungpiul Yoo, Jeonghun Song, Seung Jin Song, Ha-Na Jang, Kwagwon Kim, Ho-Young Kwak, A cost-effective method for integration of new and renewable energy systems in public buildings in Korea, Energy & Buildings, Vol. 74, pp. 120-131, 2014.

book1.gifNucleate Boiling Heat Transfer / Convective Heat Transfer in Microchannels

The effect of d.c. electric field on nucleate boiling heat transfer for various refrigerants R11, R113 and FC-72 in addition to the study on the convective boiling of refrigerant mixture of R11 and R113 [79] was investigated in a single-tube shell/ tube heat exchanger by using temperature control method of wall superheat [80]. Also the behavior of bubble under nonuniform electric field produced by wire electrode was studied by numerical calculation. Proper electrode configuration, appropriate electric field strength and wall superheat turn out to be all important factors to enhance the nucleate boiling heat transfer as well as to prevent reducing the electric field strength, which should be considered for electrohydrodynamic (EHD) augmented evaporator design and its operation [80], It has also been found that the electrical charge relaxation time of field is an important parameter for the enhancement of nucleate boiling heat transfer [81]. This can be realized by azeotropic mixture of R113+wt4% ethanol one having very short charge relaxation time of 0.005ses [82]. A "convective immersion cooling module" to enhance the the critical heat flux by increasing the nucleate boiling area in the heat spreader was developed [83].

An experimental study of thermosyphonic boiling heat transfer in vertical tube and channel made by two parallel retangular plate with open periphery was done to understand the effect of the gap size and pumping action [84]. Also a new thermosyphon cooling module(TSCM) was designed and fabricated to cool the mult-chip module(MCM), which can be utilized in the telecommunication system [85]. The cooling module patented in Korea(# 0211058) and in United States(# 5,859,763, 1999) consists of a cold plate and an integrated condenser. With an allowable temperature rise of 56 on the surface of the heater, the cooling module TSCM can handle a heat flux of about 2.7 W/cm2 using R11 as working fluid. More refined cooling module which has smooth transition from transient to steady state without heat transfer crises at any heat flux level was tested [86].
  For application in thermal control of electronic devices and bioengineering, the friction factors and the convective heat transfer coefficients for flow of water and FC-72 in microchannels with rectangular cross section [87] Recently, proteinaceous bubbles and nano particles flows in microchannels was tested to study the macroscopic flow behavior associated with the change in the state of the microchannels [88]. Recently micro/nano particles and biological cells mixed in water solution were tried to be separated using the dielectrophoresis in an evaporating droplet [89]. For cooling of microelectronic system, experiments of pool boiling on chemically etched silicon surfaces [90], capillary pumped loop with cone shaped capillary structure in evaporator [91] and forced convective heat transfer of nanofluids in microchannels [92] were performed.

[79] Jae Ho Hong, Cheon-Ho Park, and Ho-Young Kwak, "Forced convective boiling in vertical tube for binary refrigerant mixtures of R11 and R113," KSME International Journal, Vol. 12, pp. 493-503, 1998.

[80] Si-Doek Oh and Ho-Young Kwak, " A study of bubble behavior and boiling heat transfer enhancement under electric field", ASME, NE-Vol. 19, Thermal Science of Advanced Steam Generator/Heat Exchangers, pp. 1-14, 1996, Heat Transfer Engineering, Vol. 21, pp. 33-45, 2000.

[81] Snag-Houn Han, Min-Kyun Na, Si-Deok Oh and Ho-Young Kwak, "Electrohydrodynamic(EHD) enhancement of boiling heat transfer with a lo-fin tube", KSME International Journal, Vol. 13, pp. 1999.

[82] Si-Deok Oh, and Ho-Young Kwak, "Electrohydrodynamic (EHD) enhancement on boiling heat transfer of R113+wt4% ethanol mixture", Journal of Mechanical Science and Technology (KSME Int. J.), Vol. 20, pp. 681-691, 2006.

[83] Yong-Sik Yoon, Hyup Yang, and Ho-Young Kwak, "Enhancement of the critical heat flux by using heat spreader," KSME International Journal, Vol. 17, pp. 1063-1072, 2003.

[84] Jin-Seok Jeon, Jung Hee Na, Hong Chul Park, and Ho-Young Kwak, "An experiment on thermosyphon boiling in uniformly heated vertical tube and asymmetrically heated vertical channel," KSME International Journal, Vol. 15, pp.98-107, 2001.

[85] Sang-Sig Nam, Sung-Bong Choi, Jae-Hee Kim and Ho-Young Kwak, "Transient characteristics of a two phase thermosyphon cooling module for multi-chip device",     ETRI J. Vol. 20, pp. 284-299, 1998.

[86] Min-Kyun Na, Jin-Seok Jeon, Ho-Young Kwak and Sang-Sig Nam, "Experimental study on a closed loop two-phase thermosyphon for cooling MCMs, Heat Transfer Engineering, Vol.22, pp.29-39, 2001.

[87] Jung-Yeul Jung and Ho-Young Kwak, "Fluid flow and heat transfer in microchannels with rectangular cross section," Heat Transfer Engineering, in press, 2007.

[88] Jung-Yeul Jung, Ki-Taek Byun, and Ho-Young Kwak, "Proteinaceous bubbles and nano particles flows in microchannel," Microfluidics and Nanofluidics, Vol. 1, pp. 177-182, 2005.

[89] Jung-Yeul Jung, and Ho-Young Kwak, "Separation of micro particles and biological cells inside an evaporating droplet using dielectrophoresis," Analytical Chemistry, Vol. 79, pp. 5087-5092, 2007.

[90] Jung-Yeul Jung and Ho-Young Kwak, "Effect of surface condition on boiling heat transfer from silicon chip with sub-micron roughness," International Journal of Heat and Mass Transfer, Vol. 49, pp. 4543-4531, 2006.

[91] Jung-Yeul Jung, Hoo-Suk Oh, Dae Keun Lee, Kyong Bin Choi, Sang Keun Dong, and Ho-Young Kwak, "A Capillary pumped loop (CPL) with cone shaped capillary structure for cooling electronic device," Journal of Micromechanics and Microengineering, Vol. 18(1) paper #017002.

[92] Jung-Yeul Jung, Hoo-Suk Oh, Ho-Young Kwak, "Forced convection heat transfer of nanofluids in microchannels," International Journal of Heat and Mass Transfer, Vol. 52, pp. 466-472, 2009.

Two foreign scholars visited our Phase Change Lab. by BK21 programme. Dr. Sharma P. Mahapatra who stayed from November 2007 to July 2008 works as Chemistry Professor in National Institute of Technology at Rapipur, India. Dr Vijay Singh who stayed from December 2008 to November 2010 now works as HWK Fellow in Institute for Advanced Study at Delmenhorst, Germany. They produced the following excellent works during their stay.

[93] S.P. Mahapatra, V. Sridhar, D.K. Tripathy, J. K. Kim, H. Kwak, Dynamic mechanical and dielectric relaxation characteristics of microcellular rubble composites," Polymers for Advanced Technologies, vol. 19, pp. 1311-1322, 2008.

[94]T.T.N. Dang, S.P. Mahapatra, V. Sridhar, J.K. Kim, K-J. Kim, H.Kwak, Dielectric properties of nanotube reinforced butyl elastomer composites," Journal of Applied Polymer Science, Vol. 113, pp. 1690-1700, 2009.

[95] V. Singh, R.P.S. Chakradhar, J.L. Rao, H. Kwak, Characterization, EPR and photoluminescence studies of LiAl5O8:Cr phophors," Solid State Sciences, Vol. 11, pp. 870-874, 2009.

[96] V. Singh, M. Tiwari, M. Soni, M. Aynayas, S.-H. Hyun, H. Kwak, V. Natarajan, Photoluminescence and EPR investigation of combustion synthesized BaAl2O4:Cr3+, Indian Journal of Pure and Applied Physics, Vol. 47, pp. 449-440, 2009.

[97] V. Singh, V. K. Rai, I. Ledoux-Rak, H. Kwak, Visible up-conversion and NIR luminescence of LiAl5O8:Er phosphor co-doped with Yb3+ and Zn2,", Applied Physics B: Lasers and Optics, vol. 97, pp. 103-107, 2009.

[98] V. Singh, V. K. Rai, I. Ledoux-Rak, L. Badie, H. Kwak, Visible up-conversion and infrared luminescence investigations of Al2O3 powders doped with Er3+, Yb3+ and Zn2+ ions,", Applied Physics B: Lasers and Optics, vol. 97, pp. 805-809, 2009.

[99] V. Singh, S. Watanabe, T.K. Gundu Rao, J.F.D. Chubaci, I. Ledoux-Rak, H. Kwak, Infrared luminescence, thermoluminescence and defect centres in Er and Yb doped ZnAl2O4 phosphor," Applied Physics B: Lasers and Optics, vol. 98, pp. 165-172, 2010.

[100] V. Singh, R.P.S. Chakradhar, J.L. Rao, H. Kwak, "Green luminescence and EPR studies on Mn-activated yttrium aluminum garnet phosphor," Applied Physics B: Lasers and Optics, vol. 98, pp. 407-415, 2010.

[101] V. Singh, R.P.S. Chakradhar, J.L. Rao, I. Ko, H. Kwak "Luminescence and EPR studies of Eu2+ doped BaAl12O19 blue light emitting phosphors," Journal of Luminescence, vol. 130, pp. 703-708, 2010.

[102] V. Singh, S. Watanabe, T.K. Gundu Rao, J.F.D. Chubaci, H. Kwak, "Luminescence and defect centers in MgSrAl10O17:Sm3+ phosphor, Journal of Non-Crystalline Solids, vol. 356, pp. 1185-1190, 2010.

[103] V. Singh, V.V. Ravi, Kanth Kumar, R.P.S. Chakradhar, H. Kwak, Synthesis characterization and photoluminescence of Eu3+, Ce3+ co-doped CaLaAl3O7 phosphors, Philosophical Magazine, vol. 90, pp. 3095-3105, 2010.

[104]V. Singh, V.K. Rai, S. Watanabe, T.K. Gundo Rao, I. Ledoux-Rak, H. Kwak, "Infrad emission and defect centres in Er and Yb codoped Y3Al5O12 phosphors," Applied Physics A, vol. 100, pp. 1123-1230, 2011.

[105]V.Singh, V.K. Rai, S. Watanabe, T.K. Gundu Rao, I. Ledox-Rak,H. Kwak, "Infrared emissions, visible up-conversion, thermoluminescence and defect centres in Er3Al5O12 phosp, Applied Physics B , vol. 101, pp. 631-638, 2010. IF: 1.992

[106]V. Singh, S. Watanabe, T.K. Gundu Rao, H. Kwak, "Luminescence and defect centers in Tb3+ doped LaMgAl11O19 phosphors," Solid State Science, vol.12, pp. 1981-1987, 2011. IF:1.675

[107]V. Singh, S. Watanabe, T.K. Gundu Rao, J.F.D. Chubachi, H. Kwak, "Characterization, photoluminescence, thermally stimulated luminescence and electron spin resonance studies of Eu3+ doped LaAlO3 phosphor," Solid State Science, vol.13, pp. 66-71, 2011. IF:1.675

[108]V. Singh, S. Watanabe, T.K. Gundu Rao, H. Kwak, "Synthesis, characterization, luminescence and defect centres in CaYAl3O7:Eu3+ red phosphor," Journal of Fluorescence," Vol. 21, pp. 313-320, 2011

[109]V. Singh, R.P.S. Chakradhar, J.L. Rao, H. Kwak, Enhanced blue emission and EPR study of LaMgAl11O19:Eu phosphors, Journal of Luminescence, Vol. 131, pp. 247-252, 2011.

[110]V. Singh, R.P.S. Chakradhar, J.L. Rao, I. Ledoux-Rak, H. Kwak, Luminescence and EPR studies of Y2O3:Gd3+ phosphors prepared via solution combustion method, Journal of Materials Science, Vol. 46, pp. 1038-1043, 2011.

[111]V. Singh, R.P.S. Chakradhar, J.L. Rao, H. Kwak, EPR and photoluminescence properties of combustion-synthesized ZnAl2O4:Cr3+ phosphors," Journal of Materials Science, Vol. 46, pp. 2331-2337, 2011.

[112]V. Singh, R.P.S. Chakradhar, J.L. Rao, H.Kwak, Invesigation on green-emitting, Mn2+:BaAl12O19 phosphors obtained by solution combustion process, Journal of Materials Science, Vol. 46, pp. 3928-3924, 2011.

book1.gifInvited Lectures

1. Invited Lecture at the Spring Meeting of Lorean Society of Mechanical Engineers(KSME); April 24-25, 1998, Jinju(Kyung Sang University) Korea.

    Bubble, bebble, toil and trouble :

    Sonoluminescence Phenomena and Star Formation

Abstract

 The phenomenon og light emission from a oscillating gas bubble trapped in ultrasound field in water, SL, was discussed with spherical symmetry. Also the stability, spherical oscillation and gravitational collapse of Newtonian stars were stars were studied hydrodynamically.

 

2. Invited Lecture at the Research Workshop on Nucleation Theory and Applications; April 12-20, 1999,Dubna,Russia.

    Cluster Models in the Theory of Bubble Formation and Related Problems

Abstract

Using a new surface energy for the formation of the critical cluster, models for the gas bubble formation in gas-liquid solutions and for the vapor bubble formation within a liquid under tension are presented in this paper. The energy related to translational motion of molecule, which is lost during the dissolution process is considered as the surface energy needed for the gas bubble formation in solutions. Results from the model show good agreement with experiments for various gases dissolved in water solutions. On the other hand, the surface energy needed for the bubble formation is calculated from theLondon dispersion force between molecules. Also the vapor bubble formation model gives a very good prediction of tensile strength of simple liquids as well as the superheat limit of liquids. In another test of the vapor bubble formation model, the complete evaporation time of a butane droplet at its superheat limit is compared with experiments and found to be in good agreement. Transition from a critical cluster to a critical bubble where surface formation is needed in process is also discussed.

3. Plenary Speakers at the Fourth JSME-KSME Thermal Engineering Conference; Oct. 1-6, 2000,Kobe,Japan.

     Bubble Dynamics/Sonoluminescence/Newtonian Stars

Abstract

The sonoluminescence phenomenon which is the light emission associated with the catastrophic collapse of a gas bubble oscillating under ultrasound may be understood by the analytical solutions for the Navier-Stokes equations in spherical symmetry. Further the homologous solutions of the Euler equation with Newtonian gravity yield many fruitful results such as stellar stability, spherical oscillation and collapse of Newtonian stars. All these results came from an effort to understand the dynamics of a thin shelled sphere of gas, a tiny bubble.

4. Keynote Lecture at the Twelfth International Heat Transfer Conference, August 18-23, 2003,Grenoble,France.

    Bubble Nucleation; A Microscopic Phenomenon

Abstract

In this article, vaporous bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit were discussed based on clustering process of molecules (molecular cluster model for bubble nucleation). A puzzling phenomenon of carbon monoxide gas bubble formation in Fe-C-O melts was also discussed by the cluster model based on the interaction between solute gas and solvent molecules. For the vapor bubble formation, the energy barrier against bubble nucleation was estimated by the molecular interaction due toLondon dispersion force. Bubble nucleation by quantum tunneling in liquid helium under negative pressure near the absolute zero temperature and bubble nucleation on micro heaters were also presented as one of the homogenous nucleation process with the molecular cluster model.

book1.gifReview Papers / Books

1. Ho-Young Kwak and Yoon-Pyo Lee, "Shock and thermal waves emanating from a sonoluminescing gas bubble in Shock Focussing Effect in Medical Science and Sonoluminescence," Edited by R.C. Srivastava, D. Leutloff, K. Takayama and H. Gronig, Springer, 2003.

Abstract

The generation and propagation of the shock pulse from a sonoluminescing gas bubble whose wall acceleration reaches 1012m/s2 near the collapse is considered by using the bubble wall motion developed by Keller and Miksis in conjunction with the analytical solutions for the gas inside bubble and the Kirkwood-Bethe hypothesis for the outgoing wave. The propagation of the pressure wave inside the bubble, where there are in homogeneous of density, pressure and temperature induced by the rapid bubble collapse, is also treated. The propagation of a solition-like heat wave which is generated by "thermal spike" due to the rapid increase and subsequent decrease in the bubble wall acceleration is also discussed.

2. Ho-Young Kwak, "Vapor bubble nucleation: a microscopic phenomena," KSME International Journal, Vol. 18, pp. 1271-1287, 2004.

Abstract

In this article, vapor bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit were discussed from the viewpoint of molecular clustering (molecular cluster model for bubble nucleation). For the vapor bubble formation, the energy barrier against bubble nucleation was estimated by the molecular interaction due to theLondon dispersion force. Bubble nucleation by quantum tunneling in liquid helium under negative pressure near the absolute zero temperature and bubble nucleation on cavity free micro heaters were also presented as the homogenous nucleation processes.

 

 

 

3. Ho-Young Kwak, "Bubbles: Homogeneous Nucleation," Encyclopedia of Surface and Colloid Science, 2nd Edition, pp. 1048-1071, CRC Press, 2006.


Abstract

In this article, gas bubble nucleation in gas-supersaturated solutions, vapor bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit were discussed from the viewpoint of molecular clustering (molecular cluster model for homogeneous bubble nucleation) in metastable liquid. A puzzling phenomenon of carbon monoxide gas bubble formation in Fe-C-O melts and gas bubble nucleation in polymer solutions were also discussed by using the molecular cluster model based on the interaction between solute gas and solvent molecules. For the vapor bubble formation, the energy barrier against bubble nucleation was estimated from the molecular interaction due to theLondon dispersion force. Bubble nucleation by quantum tunneling in liquid helium under negative pressure near the absolute zero temperature, bubble nucleation on cavity free micro heaters, and the bubble nucleation due to laser irradiation were also presented as the homogeneous vapor bubble nucleation processes.

Key words; bubble nucleation, CO bubble in melts, droplet explosion, evaporation, gas bubble, laser-induced cavitation, microcellular foam, molecular cluster, quantum tunneling, superheat limit of liquid, tensile strength, vapor bubble.

 

 

4. Ho-Young Kwak and Si-Doek Oh, "Exergetic and thermoeconomic analyses optimal planning of cogeneration systems" in Energy Efficiency Research Advances, ed. By D.M. Bergmann, Nova Science Publishers, Inc., 2008.

Abstract

Increasing demand in fossil fuels which will remain the dominant energy source to 2030 might cause a drastic change in global climate.  To curb such fossil fuels demand and reduce CO2 emissions correspondingly, more efficient use of the fossil fuels are strongly required.  In this article thermodynamic and economic evaluation methods and optimal planning of gas turbine cogeneration systems which can return fossil fuel energy savings up to 30% are treated.  A general exergy balance equation that is applicable to any component of thermal system is presented.  A cost-balance equation formulated by assigning a unit exergy cost to each disaggregated exergy stream in the exergy balance equation is also presented.  Applications of the exergy and cost-balance equations to a gas turbine cogeneration are shown.  A method to determine the optimal configuration and optimal operation mode of cogneration system is also presented based on the energy demand data for commercial buildings such as a hotel, a hospital and an office building.

5. Ho-Yong Kwak, Nonlinear bubble behavior due to heat transfer in Heat Transfer—Theoretical Analysis, Experimental Investigations and Industrial Systems, INTECH, 2011.

 

Abstract

 

Previous studies of the forced oscillation of a spherical bubble in solution have been investigated by using the Rayleigh equation to obtain the time dependent bubble radius and a polytropic relation to obtain the gas pressure inside the bubble depending bubble volume. In fact, the polytropic approximation with proper index values has been widely used for the gas undergoing quasi-equilibrium process in which there is heat transfer. However, the polytropic pressure-volume relationship fails to account the thermal damping due to heat transfer through the bubble wall because PbdV is a perfect differential and consequently its integral over a cycle vanishes where Pb is the gas pressure inside the bubble and V is the bubble volume. Furthermore, the polytropic approximation assumes the uniform temperature for the gas intrinsically, which is valid only for a particular case and it is hard to tell whether the gas inside the bubble oscillating under ultrasound behaves isothermally or adiabatically.

In this study, we have formulated a general bubble dynamics model, which is as follows. The density, velocity and pressure distributions for the gas inside a spherical bubble were obtained by solving the continuity and momentum equations analytically. With the set of analytical solutions for the conservation equations, the temperature distribution for the gas inside the bubble was also obtained by solving the energy equation for the gas. The heat transfer through the bubble wall was considered to obtain the instantaneous thermal boundary layer thickness from the mass and energy conservations for the liquid layer adjacent to the bubble wall by the integral method. The mass and momentum equations for the liquid outside the bubble wall provided the well known equation of motion for the bubble wall, the Rayleigh-Plesset equation in incompressible medium or the Keller-Miksis equation in compressible medium. The bubble dynamics model was applied to an evolving bubble formed form the fully evaporated droplet at the superheat limit and phenomena of sonoluminescence which is light emission associated with the catastrophic collapse of a micro-bubble oscillation under ultrasound.

With uniform density, temperature and pressure approximations which are valid for the characteristic time scale of ms, the calculated values of the far field pressure signal from the evolving the bubble formed form the fully evaporated droplet at its superheat limit are in good agreement with the experimental results. With uniform pressure approximation which is valid for the characteristic time scale of s, the calculated values of the minimum velocity of the bubble wall, the peak temperature and pressure are excellent agreement with the observed ones for the sonoluminescing xenon bubble in sulfuric acid solutions. Furthermore, the calculated bubble radius-time curve displays alternating pattern of bubble motion which is apparently due to the heat transfer for the sonoluminescing xenon bubble, as observed in experiment. The bubble dynamics model presented in this study has also revealed that the sonoluminescence for an air bubble in water solution occurs due to the increase and subsequent decrease in the bubble wall acceleration which induces pressure non-uniformity for the gas inside the bubble during ns range near the collapse point. The calculated sonoluminescence pulse width from the instantaneous gas temperature for air bubble is in good agreement with the observed value of 150 ps. Due to enormous heat transfer the gas temperature inside the sonoluminescing air bubble at the collapse point is about 20000~40000 K instead of 107 K which estimated to be in the adiabatic case. Molecular dynamics (MD) simulation results for the sonoluminescing xenon bubble were compared to the theoretical predictions and observed results.

 

  

 

  dot1_yell.gif  International Conference / Symposiums

       dot1_yell.gif  Refereed Conference Preceedings

       dot1_yell.gif  Oral Presentations

book1.gifRefereed Conference Proceedings

 

[1] Ho-Young Kwak, and Sung-Kap Cho, "Bubble formation, growth, and collapse mechanism from a droplet at the superheat limit", Proceedings of the Fourth Miami International Symposium on Multiphase Transport and Particulate Phenomena,pp.359-375,1986(Miami Beach,Florida, USA).

[2] Ho-Young Kwak, and Sangbum Lee, "Homogeneous nucleation of liquids predicted by a model of molecular interactions", Proceedings of the Fourth Miami International Symposium on Multiphase Transport and Particulate Phenomena, pp. 485-500,1986 (Miami Beach, Florida,USA).

[3] Ho-Young Kwak, and Joon-Hyuk Kim, "A model of laser induced cavitation",Korea-US Seminar on Thermal Engineering and High Technology, pp. 281-295, 1986(Daejon, Korea).

[4] Ho-Young Kwak, and Si-Doek Oh, "Gas -vapor bubble nucleation --- An unified approach", Proceedings of the 1988 National Heat Transfer Conference, vol.2, pp. 557-564, 1988(Houston, USA).

[5] Ho-Young Kwak, and Yong-Won Kim, "Homogeneous nucleation and macroscopic growth of gas bubble in organic solutions, Proceedings of the First KSME-JSME Thermal and Fluid Engineering Conference, vol.1, pp.125-131, 1988(Seoul, Korea)

[6] Jung Hee Na, Jin-Seok Jun, and Ho-Young Kwak, "An experiment on thermosyphon boiling in uniformly heated vertical tube and channel", Proceedings of the 2nd KSME-JSME Fluid Engineering Conference, vol.2, pp. 160-164, 1990(Seoul, Korea).

[7] Ho-Young Kwak, and Si-Doek Oh, "A model of homogeneous bubble nucleation of CO bubble in Fe-C-O melts", Proceedings  of the 2nd KSME-JSME Fluid Engineering Conference, vol.2, pp. 177-180, 1990(Seoul, Korea).

[8] Ho-Young Kwak, Si-Doek Oh,and Jae-Ho Hong, "Thermal damping effect on an oscillating bubble in hot incompressible medium, ASME Winter Annual Meeting, ASME Paper 91-WA-HT-2, 1991( Atlanta, USA).

[9] Jei-Cheong Ryu, and Ho-Young Kwak, "Chaotic behavior of the damped bubble oscillation", Proceedings of the Fifth Asian Congress of Fluid Mechanics, pp. 1185-1188,1992(Daejon, Korea).

[10] Yong -Sik Yoon, Hyup Yang, and Ho-Young Kwak, "Enhancement of the critical heat flux from high power heat sources using heat spreader", Proceedings of the 2nd JSME-KSME thermal Engineering Conference, vol.3, pp. 349-353, 1992(Kitakyushu, Japan).

[11] Jei-Cheong Ryu, and Ho-Young Kwak, "Bifurcation phenomena for the damped bubble oscillations in periodically driven pressure fields", in HTD-vol. 214, Bifurcation Phenomena and Chaos in Thermal Convection, pp. 1-8,1992, ASME Winter Annual Meeting(Anaheim,Californai,USA).

[12] Si-Doek Oh, Sam-Sun Seung, and Ho-Young Kwak,"A model of bubble nucleation on a micro line heater", DSC-vol. 40, Micromechanical Systems, pp. 313-328,1992 ASME Winter Annual Meeting(Anaheim, Californaia, USA).

[13] Cheon-Ho Park, Jae-Ho Hong, and Ho-Young Kwak, "Forced convective boiling in vertical tube for binary refrigerant mixtures of R11 and R113", Proceedings of the 6th International Symposium on Transport Phenomena in Thermal Engineering, pp. 105-110,1993(Seoul, Korea).

[14] Si-Doek Oh, Sam-Sun Seung, Sung-Kap Cho, and Ho-Young Kwak, "Actuation mechanism by bubble formation on a micro line heater", DSC-vol.46, Micromechanical Systems, pp. 35-42,1993, ASME Winter Annual Meeting (New Orleans,Louisiana, USA).

[15] Ho-Young Kwak, and Hyup Yang, "Some theoretical aspects of sonoluminescence obtained from a bubble dynamics model", Proceedings of the 3rd JSME-KSME Fluids Engineering Conference, pp.1-6, 1994(Sendai, Japan).

[16] Si-Doek Oh, Hyo-Sun Pang, Si-Moon Kim, and Ho-Young Kwak, "Exergy analysis for a gas turbine cogeneration system", AES-vol.35, Thermodynamics and Design, Analysis, and Improvement of Energy Systems, pp. 241-254,1995, ASME International Mechanical Engineering Congress and Exposition(San Fransisco, California,USA).

[17] Si-Doek Oh, and Ho-Young Kwak, "Electrohydrodynamic(EHD) enhancement on boiling heat transfer of R113+wt 4% ethanol", Proceedings of the 3rd KSME-JSME Thermal Engineering Conference, vol.I, pp.407-414,1996(Kyongju, Korea).

[18] Yoon Pyo Lee, Kong Hoon Lee, Sang Hoon Han, and Ho-Young Kwak, "Heat transfer characteristics of a horizontal evaporator-condenser heat exchanger with noncondensable gas", Proceedings of the 3rd KSME-JSME Thermal Engineering Conference, vol.III, pp.157-162,1996(Kyongju, Korea).

[19] Si-Doek Oh, and Ho-Young Kwak, "A study of bubble  behavior and boiling heat transfer enhancement under electric field", NE-vol. 19, Thermal Science of Advanced Steam Generator/Heat Exchangers, pp. 1-14,1996, ASME International Mechanical Engineering Congress and Exposition(Atlanta,USA).

[20] Sung-Bong Choi, Sang-Sig Nam, Jae-Hee Kim, and Ho-Young Kwak, "Thermal characteristics of two phase thermosyphon cooling module for multi-chip device", PID-vol.2/HTD-vol 338, Advances in Energy Efficiency, Heat/Mass Transfer Enhancement, pp. 33-43, 1996, ASME International Mechanical Engineering Congress and Exposition (Atlanta,Georgia, USA).

[21] Si-Moon Kim,Si-Doek Oh, Yong-Ho Kwon, and Ho-Young Kwak, "An approach of exergoeconomic analysis of thermal systems",AES-vol.37, Proceedings of the ASME Advanced Energy Systems Division, pp.181-196,1997, ASME International Mechanical Engineering Congress and Exposition(Dallas,Texas,USA).

[22] Sang-Hoon Han, Min-Kyun Na, Si-Doek Oh, and Ho-Young Kwak, "Electrohydrodynamic(EHD) enhancement og boiling heat transfer with a lo-fin tube",HTD-vol.351, Proceedings of the ASME Heat Transfer Division,vol. 1, pp.223-233,1997, ASME International Mechanical Engineering Congress and Exposition(Dallas, Texas,USA).

[23] Yoon Pyo Lee,Sarng Woo Karng, and Ho-Young Kwak, "Heat Diffusion from a sonoluminescing gas bubble,Proceedings of the Eleventh International Heat Transfer Conference, vol.2,pp.39-44,1998(Kyongju, Korea).

[24] Yoon Pyo Lee, Sarng Woo Karng, Jin-Seok Jun, and Ho-Young Kwak, "Implosion from a sonoluminescing gas bubble",Proceedings of the 4th KSME-JSME Fluids Engineering Conference,pp.453-456,1998(Pusan,Korea).

[25] Yong-Ho Kwon,Ho-Young Kwak,and Si-Doek Oh, "Effect of cost change of a component on the production costs in thermal system",AES-vol.38, Proceedings of the ASME Advanced Energy Systems Division, pp.119-132, 1998, ASME International Mechanical Engineering Congress and Exposition(Anaheim,California,USA).

[26] Min-Kyun Na,Jin-Seok Jeon, Ho-Young Kwak, and Sang-Sig Nam, "Analytical and experimental studies on a closed loop two-phase thermosyphon for cooling MCM, Proceedings of the Two-Phase Flow Modeling and Experimentation, pp.553-560,1999(Pisa, Italy).

[27] Jin-SeokJeon, Ik-Jun Yang, Jung-Hee Na, and Ho-Young Kwak, "Radiation mechanism for a single bubble sonoluminescence", HTD-vol364-3, Proceedings of the ASME Heat Transfer Division, pp.1-8,1999,ASME International Mechanical Engineering Congress and Exposition(Nashiville,Tennessee,USA).

[28] Jung-Hee Na,Sung-Kap Cho, and Ho-Young Kwak, "Mass transfer characteristics for a sonoluminescing gas bubble",Proceedings of the Fourth ISHMT-ASME Heat and Mass Transfer Conference ,pp.345-352,2000(Pune, India).

[29] Jin-Seok Jeon, Ik-Jun Yang, Sarng Woo Karng, and Ho-Young Kwak, "Measurement and prediction of radius for a sonoluminescing gas bubble",Proceedings of the 4th JSME-KSME Thermal Engineering Conference, vol.1, pp.325-330(Kobe, Japan).

[30] Pan-Seok Yang, Chan-Goo Kang, Si-Doek Oh, Ho-Young Kwak,Jung-Man Lee, and Yong-Soo Lee, "Development of a simulation program for CNG refueling station", Proceedings of the 7th International Conference and Exhibition on Natural Gas Vehicles, pp.643-650, 2000(Yokohama, Japan).

[31] Duck-Jin Kim, Hyun-Soo Lee, Ho-Young Kwak, and Jae-Ho Hong, "Thermoeconomic analysis of power plants with integrated exergy stream", AES-vol.40,Proceedings of the ASME Advanced Energy Systems Division, pp.393-404,2000, ASME International Mechanical Engineering Congress and Exposition(Orlando, Florida,USA).

[32] Ho-Young Kwak, and Jung-Hwan Jun, "Hydrodynamics and thermodynamics of Newtonian stars",  AES-vol.40, Proceedings of the ASME Advanced Energy Systems Division, pp.423-430,2000, ASME International Mechanical Engineering Congress and Exposition(Orlando, Florida,USA).

[33] Ho-Young Kwak, Hyun-Soo Lee, Jin-Seok Jeon, and Dongsoo Lee,"Exergetic and thermoeconomic analysis of a 200-kW Phosphoric acid fuel cell plant", Proceedings of 2001 ASME International Mechanical Engineering Congress and Exposition, Paper #IMECE2001/ AES-23649(pp.1-10),2001 (New York,New York,USA).

[34] Jung-Yeop Lee, Hong-Chul Park, Ho-Young Kwak, and Jin-Seok Jeon, "Bubble nucleation on micro line heaters", Proceedings of 2001 ASME International Mechanical Engineering Congress and Exposition, Paper #IMECE2001/HTD-24215(pp.1-9), 2001 (New York, New York,USA).

[35] Ho-Young Kwak, Jung-Yeul Jung, and Jae-Ho Hong, "Quantum nucleation of bubbles in liquid  helium near the absolute zero temperature", Proceedings of the Twelfth International Heat Transfer Conference, pp.531-536,2002(Grenoble, France).

[36] Jung-Yeul Jung, Hong-Chul Park,Ho-Young Kwak,"Bubbble nucleation and growth on surface of rapidly heated micro heaters",Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper# IMECE2002-32777(pp.1-7), 2002(New Orleans,LouisianaUSA).

[37] Ho-Young Kwak,Gi-Taek Byun,Yong-Ho Kwon, and Ho-Young Kwak, "Cost structure of CGAM cogeneration system", Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper # IMECE-33187(pp.1-8), 2002(New Orleans,Louisiana,USA).

[38] Jung-Yeul Jung, and Ho-Young Kwak, "Fluid flow and heat transfer in microchannels with rectangular cross section", Proceedings of the First International Conference on Microchannels and Minichannels, pp.291-297(Paper # ICMM2003-1032),2003(Rochester,New York,USA).

[39] Jung-Yeul Jung, Ho-Young Kwak, Sarng Woo Karng,and Yoon Pyo Lee, "Forced convective flows in microchannels for cooling electronic devices",Proceedings of the 7th International Heat Pipe Symposium, pp.332-337,2003(Jeju, Korea).

[40] Sarng Woo Karng, Ki Young Kim, and Ho-Young Kwak, "Lagging motion of forced nonlinear oscillators", Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper# IMECE2003-43176(pp.1-8), 2003(Washington D.C., USA).

[41] Hong-Chul Park,Gi-Taek Byun,Ho-Young Kwak, and Sung-Kap Cho, "Explosive boiling of liquid droplet at their superheat limits", Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper# IMECE2003-41327(pp.1-11), 2003(Washington D.C.,USA).

[42] Jung-Yeul Jung, Ki-Taek Byun, Jae-Ho Hong, and Ho-Young Kwak, "Proteinaceous bubbles and nano particles flows in microchannel", Proceedings of the Second International Conference on Microchannels and Minichannels, pp. 961-966(Paper # ICMM2004-2437), 2004(Rochester,New York, USA).

[43] Sarng Woo Karng, Yoon Pyo Lee, and Ho-Young Kwak, "Rayleigh-Taylor instability mechanism on sonoluminescing bubble", Proceedings of the ASME Heat Transfer/Fluids Engineering Summer Conference,Paper # HT-FED04-56618(pp.1-10), 2004(Charlotte,North Carolina,USA).

[44] Jung-Yeul Jung, and Ho-Young Kwak, "Bubble nucleation and behavior on micro square heaters",International Symposium on Micro/Nanoscale Energy Conversion and Transport 2004, pp.68-70), 2004(Seoul, Korea).

[45] Ki Young Kim, Sung Lin Kang, and Ho-Young Kwak, "Growth of microcellular foams in viscoelastic mediums",Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper # IMECE2004-59490(pp.1-8),2004(Anaheim, California,USA).

[46] Ki-Taek Byun, Ki Young Kim, and Ho-Young Kwak, "Sonoluminescence characteristics from submicron size bubble", Proceedings of the Sixth KSME-JSME Thermal and Fluids Engineering Conference,pp. 1-5,2005(Jeju, Korea).

[47] Jung-Yeul Jung, and Ho-Young Kwak, "Novel fabrication and testing of a bubble powered micropump", Proceedings of the 3rd International Conference on Microchannels and Minichannels, Paper # ICMM2005-75015(pp.1-5),2005(Toronto, Canada).

[48] Si-Doek Oh, and Ho-Young Kwak, "Optimal planning of gas turbine cogeneration system based on linear programming", Proceedings of the International Green Energy Conference, Paper # IGEC-1D09(pp.1-7), 2005(Waterloo, Canada).

[49] Ho-Young Kwak, and Si-Doek Oh, "Optimal planning and economic evaluation of small scale cogeneration system", Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper # IMECE2005-80685(pp.1-10), 2005(Orlando,Florida,USA).

[50] Ki Young Kim, Ki-Taek Byun, and Ho-Young Kwak, "The mesoscopic simulation on the structures of the surfactant solution using dissipative paticle dynamics", Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper # IMECE2005-80702(pp.1-6), 2005(Orlando,Florida,USA).

[51] Jung-Yeul Jung, Hoo-Suk Oh, Dae-Keun Lee, Chang-Bok Ko, and Ho-Young Kwak, "Capillary pumped loop(CPL) with cone shaped capillary structure for cooling electronic device, Proceedings of the Fourth International Conference on Nanochannels,Microchannels, and minichannels, Paper # ICNMM2006-96158(pp.1-5), 2006((Limerick, Ireland).

[52] Ki-Taek Byun, Ki Young Kim, Hoo-Suk Oh, and Ho-Young Kwak, "Prediction  of sonoluminescence phenomena in sulfuric acid solutions by a set of solutions of Navier-Stokes equations",Proceedings of the 13th International Heat Transfer Conference, Paper # THP-11(pp.1-9),2006(Sydney, Australia).

[53] Jung-Yeul Jung, Hoo-Suk Oh, and Ho-Young Kwak, "Forced convective heat transfer of nanofluids in microchannels", Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Paper # IMECE2006-13851(pp.1-6), 2006(Chicago, Illinois. USA).

[54] Jung-Yeul Jung, and Ho-Young Kwak, "Separation of micro particles and biological cells inside an evaporating droplet using dielectrophoresis," Proceedings of the Fifth International Conference on Nanochannels, Microchannels and Minichannels, Paper # ICNMM 2007-30018, 2007 (Puebla, Mexico).

[55] Ki Young Kim, Chansoo Lim, Ho-Young Kwak, and Jong Hyun Kim, "Molecular dynamics simulation of collapsing phase for a sonoluminescing submicron and nano bubbles," Proceedings of the Eighteenth International Symposium on Transport Phenomena, pp. 1069-1076, 2007 (Daejeon, Korea).

[56] Hyon Uk Seo, Jinil Sung, Si-Doek Oh, Hoo-Suk Oh, and Ho-Young Kwak, "Economic optimization of a cogeneration system for apartments in Korea," Proceedings of the 2007 ASME International Mechanical engineering Congress and Exposition, Paper # IMECE 2007-43292, 2007 (Seattle, Washington, USA).

[57] Chansoo Lim, Jeong Eun Kim, Jae Young Lee and Ho-Young Kwak," Nonlinear behavior of micro bubbles under ultrasound due to heat trasfer," Proceedings of the 2007 ASME International Mechanical Engineering Congress and Exposition, Paper # IMECE 2007-43294, 2007 (Seattle, Washington, USA).

         [58] Ki Young Kim, Chansoo Lim and Ho-Young Kwak, "Molecular dynamics simulation for a            sonoluminescing micron bubble with mixed boundary condition", Proceedings of the sixth International            ASME Conference on Nanochannels, Microchannels and Minichannels, Paper # ICNMM 2008-62107,            2008 (Darmstadt, Germany).

           [59] Jin-Seok Jeon, Chansoo Lim and Ho-Young Kwak, "Pulse width measurement using  a time-            correlated single photon counting technique with sonoluminescing air bubble in various solutions", The            seventh JSME-KSME Thermal and Fluids Engineering Conference, Paper # I221, 2008 (Sapporo,            Japan).

           [60] Ki-Moon Kang, Hyo-Won Kim, Il-Wun Shim and Ho-Young Kwak, "Syntheses of specialty            nanomaterials at the multibubble sonoluminescence condition." Proceeding of ASME International            Mechanicl. Engineering Congress and Exposition Paper # IMECE 2008-68320, 2008 (Boston,            Massachusetts).

         [61] Ho-Young Kwak and Ki-Moon Kang, " Gaseous bubble nucleation inder shear flow," Proceedings            of  the ASME 2009, 7th International Conference in Nachannels, Microchannels and Minichannels,            Paper # IMECE 2009-82078, 2009 (Pohang, Korea).

           [62] Hyo-Won Kim, Ki- Moon Kang and Ho-Young Kwak, "Syntheses of nano chatalysts at multibubble            sonoluminescing condition," Proceeding of the 7th world Conference on Experimental Heat Transfer,            Fluid  Mechanics and Thermodynamics, pp. 315-322, 2009 (Krakow, Poland).

         [63] Ho-Young kwak, Hyo-Won Kim and Ilgon Ko, "Absolute metastable limit of liquids and gas-liquid            solutions, Proceedings of AMSE International Mechanical Enginering Congress and Exposition, Paper #            IMECE2009-10046, 2009 (Lake Buena Vista, Florida, USA).

[64] Ki-Moon Kang, Hyo-Won Kim and Ho-Young Kwak, "Catalytic test of a supported catalyst Ni/Al2O3 with core/shell structure for dry reforming of methane," Proceedings of 10th International Conference on Clean Energy (ICCE-2010), 2010 (Famagusta, N. Cyprus).

[65] Ho-Young Kwak, Ki-moon Kang and Ilgon Ko, Expanding of fire-ball and subsequent shock wave propagation by explosives detonation in underwater, Proceedings of ASME-KSME-JSME Joint Fluids Engineering Conference, 2011 (Hamamatsu, Japan)

 

[66] Yungpil Yoo, Si_Doek Oh and Ho-Young Kwak, Estimation of unit cost of electricity from solar PV and wind power systems in Korea, Abstract Book in Asia-Pacific Forum on Renewable Energy 2012, 2012 (Jeju, Korea)

 

[67] Ho-Young Kwak, Jaekyoon Oh, Yungpil Yoo, Shahid Mahmood, Bubble formation on the surface of laser irradiated nanosized particle, Proceedings of the 4th ASME Micro/Nanoscale Heat and Mass Transfer International Conference, 2013 (Hong Kong, China).

 

book1.gifOral Presentations

 

[1] R.L. Panton, and Ho-Young Kwak, "Degassing of water-gas solutions after a rapid decompression", Am. Phys.Soc. Fluid Dynamics Meeting , Nov. 1981(New Orleans, Louisiana,USA).

[2] Ho-Young Kwak, "Sound radiation from the evaporating droplet and the growing and collapsing bubble formed from the fully evaporated droplet", 108th Meeting of Acoustical Society of America, J. Acoust.Soc.Am. Suppl. 1, vol.76, S63, 1984(Minneapolis, Minnesota, USA).

[3] Joon-Hyuk Kim, Sangbum Lee, Hyup Yang, and Ho-Young Kwak, "A model of laser-induced bubble formationand collapse mechanism", 112th Meeting of Acoustical Society of America,J. Acoust.Soc.Am.Suppl.1,vol.80,S59,1986(Anaheim,California, USA).

[4] HoYoung Kwak, "Effect of ambient pressure on the pressure wave from the rapidly expanding bubble", 113th Meeting of Acoustical Society of America, J.Acoust.Soc.Am.Suppl.1,vol.81,S26, 1987(Indiannapolis,Indiana, USA).

[5] Ho-Young Kwak, "Homogeneous bubble nucleation", in the Session of "Some Unanswered Questions in Fluid Dynamics", Winter Annual Meeting of ASME,1989(San Fransisco,California, USA).

[6] Jei-Cheong Ryu, and Ho-Young Kwak, "A model of nonlinear oscillation of gas bubble in liquids",122nd Meeting of Acoustical Society of America, J.Acoust.Soc.Am.vol.90,  No.4,Pt.2, pp.2317,1991(Houston, Texas, USA).

[7] Hyup Yang, Jei-Cheong Ryu, and Ho-Young Kwak, "Temperature distribution and heat transfer from the pulsating bubble in ultrasonic field",125th Meeting of Acoustical Society of America, J. Acoust. Soc. Am., vol.93,No.4,Pt.2,pp.2383-2384,1993(Ottawa, Canada).

[8] Ho-Young Kwak, Hyup Yang, and Jae-Ho Hong, "An aspect of sonoluminescence from hydrodynamic theory", 128th Meeting of Acoustical Society of America, J.Acoust.Soc.Am., vol.96, No.5, Pt.2, pp.3253,1994(Austin, Texas, USA).

[9] Ho-Young Kwak,and Jung Hee Na, "Hydrodynamics solutions for a sonoluminescing gas bubble",3rd Joint Meeting of Acoustical Societies of America and Japan, J.Acoust.Soc.Am.,vol. 100, No.4,Pt.2,p.2679,1996(Hawaii,USA).

[10] Ho-Young Kwak, "Sonoluminescence phenomena," July 25, 1997, Mechanical Engineering Dept. KAIST(Daejeon, Korea).

[11] Yoon Pyo Lee,Sarng Woo Karng,Jin-Seok Jeon , and HoYoung Kwak, "Shock pulse from sonoluminescing gas bubble", Symposium on Sonoluminescence, September 12-13, 1997(Chicag, Illinois, USA).

[12] Jin-Seok Jeon, Ik-Jun Yang, Sarng Woo Karng , and Ho-Young Kwak, "Radius measurement of microbubble oscillating under ultrasonic field",Microscale Thermophysical Engineering Workshop, August,23,1998(Kyongju, Korea).

[13] Ho-Young Kwak,"Sonoluminescence phenomena and their applications", September, 11,1998, Mechanical Engineering Department, Pohang Institute of Technology.

[14] Yoon Pyo Lee, Sarng Woo Karng,and Ho-Young Kwak,"Thermal waves froma sonoluminescing gas bubble", 135th Meeting of Acoustical Society of America, J.Acoust.Soc.Am. ,vol.103,No.5,Pt.2, pp.3078,1998(Seattle, Washington, USA).

[15] Ho-Young Kwak, Cluster models in the theory of bubble formation and related problems",Research Workshops on Nucleation Theory and Applications, April,1999(Bogoliubov Laboratory of Theoretical Physics at the Joint Institute for Nuclear Research,Dubna, Russia).

[16] Ho-Young Kwak, "Sonoluminescence and bubble fusion", June 25, 1999, Korea Atomic Energy Research Institute (KAERI).

[17] Ho-Young Kwak, "Bubble nucleation via quantum tunneling in liquid helium", February 17, 2002, Micro Thermal System Research Center, Seoul National University.

[18] Ho-Young Kwak, "Bubble nucleation in micro line heaters", February 21, 2002, 2002, Samsung Advanced Institute of Technology.

[19] Ho-Young Kwak,  "Sonoluminescence phenomena and bubble fusion", April, 26, 2002, Department of Physics, Pohang Institute of Technology.

[20] Ho-Young Kwak, "Possibility of fusion inside a nano bubble", October, 1, 2002, Department of Nuclear and Quantum Engineering, KAIST.

[21] Ho-Young Kwak, "Bubble nucleation on micro line heaters", March ,20, 2003, School of Mechanical and Aeroapace Engineering, Seoul National University.

[22] Ho-Young Kwak, "Homogeneous bubble nucleation in liquids", Aug, 29, 2003, Department of Physics, Seoul National University.

[23] Ho-Young Kwak, "Sonoluminescence phenomena",China-Korea Symposium on Green Technology, February 11, 2004(Tianjin University,China).

[24] Ki-Taek Byun, and Ho-Young Kwak, "Bubble formation and subsequent shock propagation due to laser irradiation",Micrscale Phase Change Symposium:Tsinghua University and Chung-Ang University,February,12,2004(Beijing, China).

[25] Ho-Young Kwak, Ki Young Kim, and Sung Lin Kang, "Bubble nucleation in polymer solutions",80th Americal Chemical Society, Colloid and Surface Science Symposium, June18-21, 2006(Boulder, Colorado, USA).

[26] Ho-Young Kwak, "Characteristics and applications of sonoluminescence phenomena," Byron Lecture at the University of Texas at Austin, November 16, 2007.

[27] Ho-Young Kwak, "Characteristics and applications of sonoluminescence phenomena, Seminar at the Kyoto University, January, 24, 2008.

[28] Ki Young Kim, Chansoo Lim and Ho-Young Kwak, "Sonoluminescence phenomena in sulfuric acid solutions", 2008 ASME IMECE Micro & Nano Technology Society-Wide Forum, November 5, 2008 (Boston, Massachusetts).

[29] Ho-Young Kwak and Ilgon Ko, "Characteristics of multibubble sonoluminescence," ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting, August 2, 2010 (Montreal, Canada)

[30] Ho-Young Kwak, "Characteristics and applications of sonolumenescence phenomena,: Seminar at Kyung Hee University, October 16, 2010

 

 



  Academic Genealogy of Phase Change Laboratory

 book1.gif

A.K. Opprnheim (UC Berkely)

 

 R.L. Panton(Univ. of Texas at Austin)

 

 Ho-Young Kwak

(Chung-Ang University : Degrassing Phenomena from Liquid-Gas Solutions  after Rapid Decompression : May, 1981)   

 

Sung-Kap Cho

(Yuhan College : A Study on the Superheat Limit of  Organic Mixtures : Aug. 1985)

 

Jei-Cheong Ryu

(Korea Orthopedics and Rehabilitation Research Center  : A Study of Nonlinear Oscillation of a Gas Bubble Immersed in  a Liquid : Feb. 1992)

 

 Jae-Ho Hong

(Osan College : An Experimental Study on Flow Boiling of Refrigerant Mixtures: Aug. 1992)

 

Hyup Yang

(Kangwon National University : Sonoluminescence Phenomena: Feb. 1994)

 

Si-Doek Oh

(Blue Economy Strategy Institute Co., Ltd. : An Experimental Study of EHD Effect on Boiling Heat Transfer in Evaporator: Feb. 1995)

 

Jung-Hee Na

(Korea Power Engineering Co. Ltd.: A Thermo-Hydrodynamic Solution for a Sonoluminescing Gas Bubble  : Feb. 1998)

 

Jin-Seok Jeon

(Univ. of Toronto : Experimental Studies on Radius and Spectrum of a Light Emitting Gas Bubble in an Ultrasonic Field: Feb.2000)

 

Sarng Woo Karng

(Korea Institute of Science and Technology : A Study on Sonoluminescence Phenomena with Relaxation Motion of Bubble in Ultrasonic Field: Feb.2002)

 

Sung Lin Kang

(Korea Polytechnic University : Bubble Nucleation and Macroscopic Growth in Polymer Solutions: Aug.2005)

 

Ki-Taek Byun

(RouteJJ Co., Ltd. : A Study of Laser-Induced Cavitation,  Sonoluminescenceand Their Applications: Feb.2006)

 

Ki Young Kim

(Samsung SDS : Study of Sonoluminescence   in Sulfuric Acid Solutions : Feb.2007)

 

Jung-Yeul Jung

(Korea Ocean Research & Development Institute : A Study of Heat and Fluid Flow  in the Micro Heaters and Microchannels  : Feb.2007)

 

Ki Moon Kang

(Semes Co., Ltd.:Synthesis of Specialty Nano Materials at the Multi-bubble Sonoluminescence Condition and 

their Characteristics )