Nucleate 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 [BH-1] was investigated in a single-tube shell/ tube heat exchanger by using temperature control method of wall superheat [BH-2]. 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 [BH-2], 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 [BH-3]. This can be realized by azeotropic mixture of R113+wt4% ethanol one having very short charge relaxation time of 0.005 second [BH-4].
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 [BH-5]. 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 [BH-6]. 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 [BH-7]. A “convective immersion cooling module” to enhance the the critical heat flux by increasing the nucleate boiling area in the heat spreader was developed [BH-8]. 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 [BH-9] Proteinaceous bubbles andnano particles flows in microchannels was tested to study the macroscopic flow behavior associated with the change in the state of the microchannels [BH-10]. Micro/nano particles and biological cells mixed in water solution were tried to be separated using the dielectrophoresis in an evaporating droplet [BH-11]. With simple model for a surfactant consisting of a hydrophilic head group and hydrophobic tail groups connected by harmonic springs, the structural change of the association structures of the surfactant in aqueous solution was studied by using the dissipative particle dynamics (DPD) simulation [BH-12]. For cooling of microelectronic system, experiments of pool boiling on chemically etched silicon surfaces [BH-13], capillary pumped loop with cone shaped capillary structure in evaporator [BH-14] and forced convective heat transfer of nanofluids in microchannels [BH-15] were performed. Recently, propagation of pressure wave [BH-16] and shock wave [BH-17] was studied by using our bubble dynamics model.
[BH-1] 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.
[BH-2] 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.
[BH-3] 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.
[BH-4] 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.
[BH-5] 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.
[BH-6] 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.
[BH-7] 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.
[BH-8] 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.
[BH-9] Jung-Yeul Jung and Ho-Young Kwak, “Fluid flow and heat transfer in microchannels with rectangular cross section,” Heat Transfer Engineering, in press, 2007.
[BH-10] Jung-Yeul Jung, Ki-Taek Byun, and Ho-Young Kwak, “Proteinaceous bubbles andnano particles flows in microchannel,” Microfluidics and Nanofluidics, Vol. 1, pp. 177-182, 2005.
[BH-11] 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.
[BH-12] Ki Young Kim, Ki-Taek Byun, Ho-Young Kwak, “Mesoscopic simulation for the structural change of a surfactant solution using dissipative particle dynamics,” Korean Journal of Chemical Engineering, vol. 26, pp. 1717-1722, 2009.
[BH-13] 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.
[BH-14] 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.
[BH-15] 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.
[BH-16] Shahid Mahmood, Ho-Young Kwak, “Pressure waves in bubbly liquids,” Journal of Mechanical Science and Technology, 2016.
[BH-17] Shahid Mahmood, Ho-Young kwak, ” Shock wave propagation in bubbly liquids,” Submitted for publication, 2016.