Begell House Inc.
Interfacial Phenomena and Heat Transfer
IPHT
2169-2785
1
1
2013
STANDING SYMMETRIC OSCILLATIONS AND TRAVELING WAVES IN TWO-LAYER SYSTEMS WITH PERIODIC BOUNDARY CONDITIONS
1-12
10.1615/InterfacPhenomHeatTransfer.2013006791
Ilya B.
Simanovskii
Department of Mathematics, Technion - Israel Institute of Technology, 32000 Haifa, Israel
instabilities
interface
two-layer system
Nonlinear oscillatory convective flows developed under the joint action of buoyant and thermocapillary effects in the 47v2 silicone oil − water system with periodic boundary conditions on the lateral walls have been investigated. Two-dimensional convective regimes are studied by the finite difference method. Transitions between the flows with different spatial structures have been considered. Regimes of standing symmetric oscillations, traveling waves and modulated traveling waves have been found.
ENHANCED HEAT TRANSFER OF FLOW BOILING COMBINED WITH JET IMPINGEMENT
13-28
10.1615/InterfacPhenomHeatTransfer.2013006382
Jin-Jia
Wei
School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China; Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong Uniersity, Xi'an, 710049, China
Yonghai
Zhang
School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, Shaanxi,
710049, P.R. China; Shenzhen Research Institute of Xi'an Jiaotong University, Shenzhen, Guangdong, 518057,
P.R. China
Jian-Fu
Zhao
CAS Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, 15 Beisihuan Xilu, Beijing 100190, China; School of Engineering Science, University of Chinese Academy of Sciences, 19A Yuquan Rd, Beijing, 100049, China
Dong
Guo
YanTai WanHua Group, YanTai, 264000, China
flow boiling
jet impingement
micro-pin-fins
synergistic effect
FC-72
The experiment was made at flow boiling heat transfer of FC-72 on micro-pin-finned chips with jet impingement. The
experimental conditions cover two different liquid subcooling degrees (25, 35 K), three different crossflow velocities (Vc = 0.5, 1, 1.5 m/s), and three different jet velocities (Vj = 0, 1, 2 m/s) in the direction perpendicular to chip surface. The dimension of the silicon chips is 10 mm × 10 mm × 0.5 mm (length × width × thickness) on which four kinds of micro-pin-fins with the dimensions of 30 × 30 × 60 μ;m3, 50 × 50 × 60 μ;m3, 30 × 30 × 120 μ;m3, 50 × 50 × 120 μ;m3 (width × thickness × height, named PF30-60, PF50-60, PF30-120, PF50-120) were fabricated
using the dry etching technique. A smooth surface (named chip S) was also tested for comparison. The results have
shown that flow boiling combined with jet impingement gives a large heat transfer enhancement compared with pool
boiling and flow boiling. It has been also found that micro-pin-finned surfaces enhance heat transfer compared with the smooth surface. For all chips, the maximum q CHF increases in the order of chips S, PF50-60, PF30-60, PF50-120, PF30-120, and q CHF increases with crossflow or jet velocities. The maximum allowable heat flux q max is given by the q CHF if Tw,CHF < 85°C and by q at Tw = 85°C, if Tw,CHF > 85°C. Effects of liquid subcooling, surface structure, and boiling heat transfer mode on maximum allowable heat flux were also investigated in the present experiment, and the combination of these influence factors of maximum allowable heat flux exerts a synergistic effect. The maximum allowable heat flux of chip S is 15.1 W/cm2 at ΔTsub = 25 K by pool boiling, and the maximum allowable heat flux of micro-pin-fins by crossflow–jet combined boiling in the experiment is 167 W/cm2, which is 11.06 times as large as that
for the smooth surface without additional flow.
DETERMINATION OF APPARENT CONTACT ANGLE AND SHAPE OF A STATIC PENDANT DROP ON A PHYSICALLY TEXTURED INCLINED SURFACE
29-49
10.1615/InterfacPhenomHeatTransfer.2013007038
Gaurav
Bhutani
Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
Krishnamurthy
Muralidhar
Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
Sameer
Khandekar
Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur (UP)
208016, India
pendant drop
apparent contact angle
drop profile
advancing and receding angles
Surface Evolver
inverse technique
surface roughness
surface inclination
Estimating the apparent contact angle under equilibrium conditions is critical for the understanding of several engineering processes. Some examples are dropwise condensation, digital microfluidics, and material deposition schemes. Often, there is considerable uncertainty in the experimental estimation of the contact angle. In this work, we discuss the contact angles and shapes of pendant drops on physically textured inclined surfaces. Two methodologies to determine the apparent contact angles have been employed. In one approach these are obtained from drawing tangents at contact points of micro-droplets in optical images using digital image processing. In the second method, the three-dimensional
(3D) Young–Laplace equation is numerically solved using the open-source software, Surface Evolver, by minimizing
the sum of the potential and surface energies of the pendant droplet. A section of the numerically obtained 3D droplet shape is then fitted to the experimentally obtained two-dimensional profile using an inverse method. Advancing and receding angles of the imaged drop are calculated by minimizing the error between the numerical and experimental drop shapes, providing good estimates of these angles. In addition, the complete 3D droplet shape is also obtained. The overall methodology presented herein is generic, although the experiments have been conducted with glycerin as the working fluid. The role of surface roughness, plate inclination, and drop volume on the advancing and receding angles of a pendant drop are discussed. On inclined surfaces, the three-phase contact line does not remain pinned and its shape is not circular. The receding angle progressively diminishes with inclination while the advancing angle remains nearly
constant.
COALESCENCE OF A DROPLET CLUSTER SUSPENDED OVER A LOCALLY HEATED LIQUID LAYER
51-62
10.1615/InterfacPhenomHeatTransfer.2013007434
Alexander A.
Fedorets
University of Tyumen, X-BIO Institute, 6 Volodarsky St, Tyumen, 625003, Russia
Igor V.
Marchuk
Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, prosp. Lavrentyev 1, Novosibirsk; Novosibirsk State University, Pirogova 2, Novosibirsk, 630090, Russia
Oleg A.
Kabov
Kutateladze Institute of Thermophysics of the Siberian Branch of the Russian Academy of Sciences, 1, Acad. Lavrentyev Ave., Novosibirsk, 630090, Russia; Novosibirsk State University, 2, Pirogova str., Novosibirsk, 630090, Russia; Novosibirsk State Technical University, 20 Prospect K. Marksa, Novosibirsk, 630073, Russia
levitating drops
evaporation
thermocapillary convection
capillary wave
thermal imaging
temperature jump on the interphase
Experimental results on the coalescence of a dissipative structure "droplet cluster" obtained by means of high-speed
thermal imaging are presented. It is found out that coalescence of a single cluster droplet with a liquid layer can generate a capillary wave on the interphase, and propagation of this wave causes coalescence of the whole cluster during several thousandths of a second. Cluster coalescence is accompanied by a temperature jump on the interphase. With cluster restoration, the surface temperature of a liquid layer returns gradually to the initial level. The interphase temperature under the droplet cluster can be both lower and higher than the interphase temperature without this cluster, i.e., the
cluster can not only initiate both heat and mass transfer between liquid and gas, but also deteriorate it.
BOILING HEAT TRANSFER BY NUCLEATE BOILING OF IMMISCIBLE LIQUIDS
63-80
10.1615/InterfacPhenomHeatTransfer.2013007205
Shunsuke
Onishi
Department of Aeronautics and Astronautics, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan, 819-0395
Haruhiko
Ohta
Department of Aeronautics and Astronautics, Kyushu University, Chihaya Higashi-ku, Fukuoka, Fukuoka, Japan
Nobuo
Ohtani
Department of Aeronautics and Astronautics, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan, 819-0395
Yuta
Fukuyama
Department of Aeronautics and Astronautics, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan, 819-0395
Hiroyuki
Kobayashi
Department of Aeronautics and Astronautics, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan, 819-0395
pool boiling
immiscible liquid
critical heat flux
subcooling
intermediate burnout
Among the various methods to improve the heat transfer characteristics of nucleate boiling, the present research concentrates on the selection of coolant. Most of the existing research on nucleate boiling of binary mixtures clarified the heat transfer characteristics peculiar to the miscible mixtures, while the number of studies on immiscible mixtures is very limited. Pool boiling experiments on nucleate boiling of three immiscible mixtures, FC72/water, Novec649/water, and
Novec7200/water, are performed in a closed vessel at 0.1 MPa. In the experiments, the thicknesses of stratified liquid layers for both component liquids on a horizontal heating surface before the heating are varied as one of the important parameters. When the layer thickness of the more volatile component with higher density is very small, e.g., 5 mm, a new phenomenon, "intermediate burnout", is observed. At heat flux higher than that of intermediate burnout, the surface temperature for the immiscible mixtures decreases from that for pure water, and simultaneously the critical heat flux (CHF) for the mixtures increases under the same pressure. The increase of CHF is mainly caused by the high subcooling
of water, i.e., the less volatile component, resulting from the pressurization by the vapor of the more volatile component. The immiscible mixture has the potential to realize high performance heat exchange by the self-sustaining subcooling of component liquids even in closed systems.
INSTABILITY AND RUPTURE OF THIN LIQUID FILMS ON SOLID SUBSTRATES
81-92
10.1615/InterfacPhenomHeatTransfer.2013006838
Vladimir S.
Ajaev
Department of Mathematics, Clements Hall, Southern Methodist University, Dallas, TX,
75275, USA
surface tension
viscous flow
disjoining pressure
thermocapillarity
Studies of rupture of thin liquid films on solid surfaces are important for modeling of multiphase flows in microfluidic devices, heat exchange systems, mining industry, and for biomedical applications such as dynamics of the tear film in the eye. In the present study we review theoretical work on film rupture and discuss its comparison with some recent experiments. Conditions for the break-up of thin liquid films by London-van der Waals dispersion forces, electrostatic effects, and thermocapillary instability are discussed.