Heat transfer and critical phenomena during evaporation and boiling in a thin horizontal liquid layer

Significance 

Critical heat flux (CHF) limits areas of any heat-flux controlled boiling or evaporation application by the maximum heat flux. The first relationship for calculating the CHF at pool boiling is given by Kutateladze in 1948 by dimensional analysis based on the hypothesis of hydrodynamic nature boiling crisis. Presently, five approaches for the analysis of CHF mechanisms have been mainly considered, namely: bubble interference, hydrodynamic instability, macrolayer dryout, hot/dry spot, and interfacial lift-off. Previous studies have shown that none of the known calculation dependences (except Yagov model connecting crisis with irreversible growth dry spots area), cannot describe the experimental data on boiling crises at low reduced pressures, where the effect of pressure on CHF is very weak. Unfortunately, at low reduced pressures the mechanism of heat transfer through the liquid layer limited in height is changing. The upper boundary of the liquid layer starts playing an important role for the heat sink at low pressures. The convective motions of liquid carry hot liquid onto the free surface, where it evaporates. The effect of liquid evaporation from the upper boundary in the limiting case leads to inevitably of the Landau instability.

Recently, research carried out by professors V.I. Zhukov and A.N. Pavlenko from the Novosibirsk State Technical University and Kutateladze Institute of Thermophysics in Novosibirsk in Russia, respectively, investigated the heat transfer and high–speed video recording of evaporation and boiling processes in horizontal liquid films of n-dodecane for the wide ranges of layer height and pressure. They purposed to define the boundaries of the various regions characterizing existences of various structures in thin layers of liquid depending on the process regime parameters. Their work is currently published in the research journal, International Journal of Heat and Mass Transfer.

The two researchers commenced their experimental procedure by designing a working chamber as a thermosyphon whose surface was to be used as a heating surface. Next, they characterized evaporation regimes at low reduced pressures by formation of dry spots and structures with the shape of ‘‘funnels” (depressions with a hemispherical bottom on the layer surface) and ‘‘craters” in the layers. Eventually, maps of hydrodynamic regimes of evaporation and boiling for different heights of the liquid layer were plotted.

Zhukov and Pavlenko observed that at low reduced pressures in the liquid layers with the height less than the Laplace constant, dry spots were formed in the layer. Additionally, after a comparison of the calculations by the Kutateladze formula with experimental data, it was seen that at heat fluxes below the calculated ones, the ‘‘funnels” and ‘‘craters” were observed in the layer higher than the Laplace constant and for the heat fluxes higher than the calculated ones, only ‘‘craters” were observed in the layers. An increase in pressure resulted in all cases to occurrence of nucleate boiling.

The Zhukov-Pavlenko study has presented a systematic investigation of the various heat transfer regimes and critical phenomena at evaporation and boiling in the thin horizontal liquid layers with a wide range of pressures and layer heights. Zhukov-Pavlenko results depict that the upper value of CHF in the low pressures region is principally confined in the limiting case by Landau instability. Again, a cross examination of the experimental data indicates that within certain pressure range, the critical heat fluxes is slightly dependent on pressure. Altogether, the slope of the curve of heat flux dependence on the temperature head depends on the layer height at both evaporation and nucleate boiling.

Heat transfer and critical phenomena during evaporation and boiling in a thin horizontal liquid layer at low pressures. Advances in Engineering

About the author

Prof. Aleksandr N. Pavlenko is a head of Low Temperature Thermophysics Laboratory at Kutateladze Institute of Thermophysics SB RAS (IT SB RAS), Novosibirsk, Russia (from 1996). He graduated from the Department of Physics of Novosibirsk State University with a Speciality in Physics in 1981. . He worked as an Jr. rschr. Kutateladze Inst. Thermophysics SB RAS, Novosibirsk, 1983-89, sr. rshchr., 1989-96. He received his Ph.D. in Physics and Math. (Kutateladze Institute of Thermophysics SB RAS) in 1990, DSc in Physics and Math. (Kutateladze Institute of Thermophysics SB RAS) in 2001.

His main fields of research are heat transfer, transitional processes and crisis phenomena at boiling and evaporation, interfacial phenomena, distillation on the structured packing, investigation of the effects of micro-nanostructures of the heat-releasing surface and various nano-additions on intensification of heat transfer processes.

To date, he has co-authored two books in the field of heat and mass transfer and has published 150 journal and 230 conference papers/book chapters in the above technical areas. He has graduated 52 students/PhD students who now hold positions in academia and industry around the world.

He has received S.S. Kutateladze prize of SB RAS; he was awarded with certificates of honor and gratitude of RAS as well as of the Novosibirsk City Hall, Memorial sign of Novosibirsk City administration “For the work for the benefit of the city”. For successful and fruitful cooperation with the largest company of cryogenic machine building “Air Products and Chemicals, Inc.” he was awarded with four certificates of honor for the fundamental scientific and important applied results on hydrodynamics of the co-current and counter-current two-phase flow in the complex channel systems and minichannels, on regularities of mass transfer at distillation on the structured packing of various geometries in the columns of different shapes (2002, 2009).
He is Corresponding Member of Russian Academy of Sciences (2008), Member of the Scientific Council of the International Committee for Heat and Mass Transfer ICHMT (2009), Member of the National Committee for Heat and Mass Transfer NCHMT RAN (2008), editor–in-Chief of the Journal of Engineering Thermophysics (since 2014), and an Editorial Council member of the Journals “High Temperature” and “Thermal Processes in Engineering”.

He is a Chairman and a member of more than 40 organizing committees of conferences and symposiums, expert of the Russian Science Foundation (RSF), the Russian Foundation for Basic Research (RFBR), “SKOLKOVO” fund.

About the author

Dr. Vladimir Zhukov is an Associate Professor at Novosibirsk State Technical University, Novosibirsk, Russia (since 1998). He graduated from the Department of Physics of Novosibirsk State University with a Speciality in Physics in 1982. He worked as an Еngineer at Novosibirsk Branch of the Chemical, Engineering Design Institute (1982-1993) and as a Lecturer at Siberian State University of Geosystems and Technologies (1995-1998). He received his Ph.D. in Engineering Sciences (Kutateladze Institute of Thermophysics SB RAS) in 1991.

To date, he has published 26 papers in peer-reviewed journals in the field of science and technology. The scope of his scientific interests includes experimental study of heat and mass transfer processes in vacuum diffusion pumps, enhanced heat transfer, swirling flows, heat transfer and crisis phenomena at boiling and evaporation the film of liquids.

Reference

V.I. Zhukov, A.N. Pavlenko Heat transfer and critical phenomena during evaporation and boiling in a thin horizontal liquid layer at low pressures. International Journal of Heat and Mass Transfer, volume 117 (2018) pages 978–990.

Go To International Journal of Heat and Mass Transfer

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