Icing is one of the most fascinating phenomena occurring ubiquitously in nature and multiple industrial applications. In spite of a century of research work on this topic, an in-depth physical description of icing process is still missing due to the unorthodox behaviors of water during solidification. In recent years, many important features pertaining to some ultrafast and microscale phenomena in icing have been revealed using latest experimental techniques and newly developed numerical simulation methods. This work aims to present a comprehensive up-to-date review on the subject of icing. Fundamentals of icing nucleation dynamics are introduced, followed by discussion on propagations of freezing phase fronts. Different forms of icing, including freezing of droplets, desublimation/sublimation, and condensation frosting, are presented sequentially. Emphasis is placed on a few recently revealed phenomena, such as dendritic ice growth through desublimation, kinetic behaviors of droplets upon freezing, frost spreading by building icing bridges, etc. A summary of recent progress in the application of anti-/de- icing methods is also presented. The results of these studies not only improve our understanding of physical mechanisms on icing, but also benefit the understanding of solidification processes in other disciplines with different applications.

Y. Zhao;Q. Guo;T. Lin;平 郑

International Journal of Heat and Mass Transfer

2020-10

Microchannel heat sink is a promising technique to dissipate high heat flux microelectronic chips in the near future. A silicon-based heat sink with tree-shaped microchannel network for the cooling of microelectronic chips was fabricated using micro electromechanical system techniques. Pt film thermo-resistors were also integrated on the heating surface to measure the surface temperature distribution. An experimental setup was built to test the pressure drop and thermal performance of the micro heat sink. The results show that the experimental data agree very well with the previous 3-D numerical simulation. And, the advantages of the tree-shaped microchannel network over parallel microchannel are verified.

芳军 洪;平 郑;Ou Liang Chang;Sheng Wu

Shanghai Jiaotong Daxue Xuebao/Journal of Shanghai Jiaotong University

2009-10

平 郑

Proceedings of the ASME Micro/Nanoscale Heat and Mass Transfer International Conference 2009, MNHMT2009

2010

The periodic generation of monodisperse micro air bubbles in water flowing in silicon microchannels having a trapezoidal cross section is investigated experimentally with the aid of high-speed CCD imaging technology. Air and water, used as the discontinuous and carrier fluid, are first co-flowing in the air microchannel and two adjacent water microchannels separately, and then converge in the main microchannel downstream. After breakup of the air bubble injected from the air microchannel, slug/bubbly flow regimes are formed periodically in the main microchannel. Correlations for the dimensionless bubble length and the dimensionless bubble formation frequency are obtained in terms of appropriate dimensionless parameters respectively.

Xiaojun Quan;Gang Chen;平 郑

International Communications in Heat and Mass Transfer

2010-10

Thermoacoustic oscillations at a cycle-steady state in a tube with an isothermal outer wall, and with one end closed and the other end connected to a wave generator, is analyzed based on a linearized theory. From the global mass conservation, an analytical solution has been obtained for the cross-sectional and cycle averaged axial velocity. It is shown that this averaged velocity is non-vanishing due to the mass streaming effect. By analyzing the global momentum balance, it is found that the cycle-averaged pressure depends on the momentum streaming and friction force, and a conservation relationship exists between the momentum streaming and the cycle-averaged pressure for the flow oscillating at a high frequency in a wide tube. An investigation of the global energy balance leads to an expression for thermoacoustic energy streaming. Furthermore, it is shown that the refrigeration effect is mainly caused by the non-vanishing mean velocity, and therefore the mass streaming and the energy streaming are intimately connected.

G. Q. Lu;平 郑

International Journal of Heat and Mass Transfer

2005-4

The possibility of using a micro-thermal bubble, generated by a micro-heater under pulse heating, as an actuator for applications in micro-bio-analytical systems is investigated in this paper. The perturbation force, generated when the micro-thermal bubble is formed instantaneously, can be used to promote such actions as mixing in the solution of a micro-reactor. Under pulse heating, a specially designed non-uniform width micro-heater (10 × 3 μm²) can induce highly localized near-homogeneous nucleation and results in periodic generation of stable single bubbles in DI water. The single bubble appears precisely on the narrow part of the micro-heater with size restricted within the superheated region in the fluid. The growth and collapse of the bubble, recorded by a high-speed CCD, is shown to be asymmetric with time if the pulse width is at milliseconds in time scale. This asymmetric behavior is very much different from those in thermal ink-jet printers. The bubble behavior under different heating duration, ranging from microseconds to milliseconds, is experimentally studied. A transient 3-D heat conduction numerical simulation is carried out to study the temperature field of the fluid before the nucleation process. To evaluate the perturbation area of the micro-bubble, submicron particles with diameter of 0.96 μm were placed in the fluid and their dynamic response during the transient bubble formation is recorded.

佩刚 邓;Yi Kuen Lee;平 郑

International Journal of Heat and Mass Transfer

2003-10

In this paper, effects of non-uniform temperature in the ice nucleus on heterogeneous ice nucleation are investigated via two approaches: changes in Gibbs free energy function and availability function. Analytical expressions for non-uniform temperature distribution inside the ice nucleus and heat transfer from the nucleus to the supercooled wall are obtained in terms of the contact angle and supercooled wall temperature based on the consideration that thermal conductivity resistance of the nucleus, interfacial resistance and thermal resistance due to curvature of ice/water interface are in series. With non-uniform temperature in the nucleus taken into consideration, it is found that the critical radius of the ice nucleation obtained based on availability analysis is slightly larger than those obtained based on Gibbs free energy analysis. Both heterogeneous critical radius and nucleation energy barrier are found to be increasing with surface contact angle. On an ice-phobic surface at small supercooling degrees, the critical radius and the nucleation energy barrier obtained with or without heat transfer taken into consideration differ greatly with the increase of the contact angle. However, at large supercooling degrees and small contact angles, differences in the critical radius and nucleation energy barrier by availability analysis are negligible with or without heat transfer effects. Thus, heterogeneous nucleation behaviors on ice-philic surfaces can be estimated based on the assumption of uniform temperature in the ice nucleus when degree of wall supercooling is large.

Q. Guo;平 郑

International Journal of Heat and Mass Transfer

2020-12

Based on a macroscopic force balance analysis, an analytical solution in terms of dynamic contact angle is obtained for steady velocity of a droplet driven by a shear flow and moving on the hydrophobic wall of a microchannel. The multiphase free-energy 3-D Lattice Boltzmann method (LBM) is applied to simulate the deformation of the droplet in order to obtain the dynamic contact angle of the moving micro-droplet in the analytical solution. The droplet velocities predicted by the analytical solution are found in good agreement with the LBM simulation results.

Liang Hao;平 郑

International Journal of Heat and Mass Transfer

2010-2

The electrohydrodynamic (EHD) enhancement of pool boiling from smooth and ribs surfaces in R113 is studied experimentally in this paper. Measurements and visualization methods are utilized to record and observe boiling heat transfer phenomena on heated surfaces with different rib heights (0 mm, 0.2 mm, 0.5 mm and 2.0 mm), and the "field trap effect" on rib surfaces is discussed. It is found that the boiling curve under an imposed electric field can be divided into three regions: low-superheat, medium-superheat and high-superheat regions, and EHD enhancement mechanisms on pool boiling heat transfer in these regions are investigated. In the low-superheat region, electroconvection is the main mechanism for heat transfer enhancement. In the medium-superheat region, both electroconvection and nucleate boiling heat transfer exist but bubble growth and departure are inhibited by the electrical force, and thus nucleate boiling heat transfer deteriorates. In the high-superheat region, because vapor columns are broken into small vapor slugs under the action of the electrical force, boiling heat transfer and critical heat flux are thus enhanced.

Xiaojun Quan;Ming Gao;平 郑;Jiasheng Li

International Journal of Heat and Mass Transfer

2015-6

This paper at first time numerically simulated the droplet driven in an electrowetting droplet-based microfluidic chip on a single-plate with no ground line, using droplet electrohydrody-namics (EHD) method by solving the conjugated N-S equations, volume of fluid (VOF) transport equation and electrical field equations. The results indicated in the process of the droplet driven to the activated electrode, the droplet morphology dodders, characterized by the oscillation of advancing and receding contact angles, and the droplet moving velocity decreases gradually and finally stops above the centre of grounded and activated electrodes.

芳军 洪;平 郑;Jun Cao

Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics

2009-8