能源与动力工程系

Department of Energy and Power Engineering

清华大学能源动力讲坛系列报告(十一)

11st Forum of Energy and Power 

Title:Technologies and boiling heat transfer enhancement on micro- and nano scales

Reporter:Prof. Yuri Kuzma-Kichta

(Moscow Power Engineering Institute)

Date:2019-4-29 (Monday)

Time:15:00-17:00

Site:A-559, Lee Shau Kee Building of Science and Technology

Inviter:姜培学

Abstract: Micro porous sintering coating is very effective coating for boiling.  This coating has a ready-made nucleation sites and Dmax and Dmin are the maximum and minimum diameters of pores. Such surface offers more favorable conditions for the nucleation process than a technically smooth surface, and this leads to lower wall superheating corresponding to the incipience of boiling. Micro porous sintered coating increases boiling heat transfer coefficient. Thin coating is more effective at the bubble boiling process. On the contrary, thick coating is more appropriate for the film boiling.

Micro porous sintered coating exerts the influence on the mechanism and development of the dry-out and can lead to both an increase and a decrease in qcr. A decrease in qcr on micro porous sintered coating is possible in the case where the data lie to the left of the inversion point of the dependence of qcr on mass velocity. An increase in qcr on applying micro porous sintered coating is possible in the case where the data lie to the right of the inversion point of the dependence of qcr on mass velocity.

Within the range of mass velocities ρω= 100?600 kg/(m2?s) the boundary vapor content  for a pipe without coating and with porous coating coincide. The boundary vapor content decrease in the region ρω < 100 kg/(m2?s) for a pipe without coatin . The decrease in the boundary vapor content at ρω < 100 kg/(m2?s) does not occur due to the action of the capillary forces of the porous structure exceeding the liquid film resistance to drying . The mechanism of heat transfer enhancement with micro porous sintered coating analyzed in film boiling by laser diagnostic.

Nanoparticles form the coating by deposition on the heating surface during boiling of nanofluid. The nanoparticles of coating have a fractal structure. Such structure of coating can be characterized with a fractal dimension. The coating from nanoparticles can either increase the heat transfer coefficient or decrease it at boiling.  This problem was analyzed with help of video film and measuring vapor content. The coating from nanoparticles decreases the contact angle, improves the transport of liquid and increases critical heat flux in pool.

It was very interesting to study the crisis in micro channel with coating from nanoparticles. We study this problem in the micro channel 3mm width, 13.7mm length, 0.2mm height for water. The thickness of the alumina nanoparticles layer is about 1 μm. The alumina nanoparticles coating increases more than 1.5 times the CHF and heat transfer in transition boiling in comparison with the value for surface without coating.

Pulsations of void fraction and average void fraction were measured in microchannel boiling. Pulsations of void fraction allowed to provide diagnostics of two-phase flows.

This work was supported by RFBR, Grant 18-08-183

Brief Biography: Dr. Yuri Kuzma-Kichta is a professor of Thermal Physics Department of Moscow Power Engineering Institute.

In 1967-1980 - was developed the boundary layer laser investigation method and investigated the mechanism of pool boiling (nucleate and film) heat transfer enhancement by microporous coating. The vapor film thickness and fluctuations measured at film boiling on tube in first.

In 1981-1990 - investigated the increasing of critical heat flux in channel with microporous coating at low mass velocities and pressures in first.

In 1991-2004 – investigated heat transfer and hydrodynamics during boiling of water solutions in tubes at low mass velocities and pressures in first.

In 2000-2005 – investigated vapor bubble fluctuations during its growth on the heating surface and showed that they are chaotic in first.

In 2005 - was invited by JSPS to give lections and to take a part in a joint investigation in Japan universities.

In 2005-2008 – investigated boiling characteristics of the single micro-cavity and showed that bubble diameters decrease with the cavity size reduction.

In 2008-2018 – studied the rewetting of the heating surface (in the context of nuclear reactors accidents) and effect of coating from micro- and nanoparticles on Leidenfrost temperature.

Since 2009 – investigates boiling (in pool and in a micro-channel) heat transfer on surfaces with micro- and nano-relief.

The obtained results were published in monographs:

“Hydrodynamics and heat transfer of water solutions boiling” , Publish Haus MEI, 2007, (P.164),

“Heat and Mass Transfer Enhancement on Macro-, Micro- and Nanoscales”,  Energoatomizdat, 2008, (P.532) ,“Intensification of heat and mass transfer on macro-, micro- and nanoscales”, Begell, 2016, (p.564),“Vortextechnologies for energetics”. Publish Haus MEI. 2017. P.350.

In 2008, 2010, 2012 – invited by DFG to take a part in conferences and seminars in Berlin, Erlangen, Munich and Braunschweig universities.

In 2005, 2008, 2011, 2015, 2017 – took part in the “International Conference on heat and mass-transfer in swirl flows” as a vice-chairman.

In 2012 – received the Award of the Russian Federation Government for joint work named “Development of efficient devices and vortex technologies”.


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