In the keynote lecture the analysis of the modern state in the field of development of methods of heat transfer enhancement at nucleate boiling and evaporation in falling liquid films of refrigerants on the modified surfaces is carried out. As part of this analysis, a number of recent results obtained by the author and his colleagues are discussed. Various methods of surface treatment are analysed – methods of deformational cutting, installation of mesh coatings, including ierarhial combined structure, plasma spray coatings, 3D printing methods, micro-arc oxidation method, methods of creating contrast wettability.

 The paper presents a comparison of the results of heat transfer enhancement during boiling and evaporation of refrigerants in falling liquid films on vertical cylinders and flat plates, on the horizontal tubes using different surface treatment methods.

Finning of horizontal tubes with characteristic fin size in the order of liquid capillary constant leads to intensification of heat transfer mainly in the regime of evaporation of flowing film. The creation of a hybrid surface through the application of artificial roughness allows an additional increase in the heat transfer coefficients at nucleate boiling.

The application of plasma spray coatings with thicknesses of approximately 140–350 μm has been demonstrated to consistently enhance heat transfer in a film falling on the surface of horizontal tubes in the developed nucleate boiling regime. For coatings with a thickness of about 335 μm at a heat flux q ≈ (30−40) kW/m2 and Reynolds number Re = 1 000, the maximum increase in heat transfer reaches ≈ 3.5 times that of plain tubes. The porous rough structure of the coating, which exhibits a high roughness and broad range of pore sizes, contributes to effective wetting and uniform distribution of low-viscosity liquid over the tube surface.

The method of deformational cutting makes it possible to create a complex surface structure with micro-refinement and a developed structure of sub-surface cavities, which act as effective nucleation sites. On all surfaces of horizontal tubes modified by the deformational cutting method, a stable intensification of heat transfer in the falling film in the nucleate boiling regime is observed. 

Micro-arc oxidation of the surface of aluminum alloy tubes can produce a thin porous coating depending on the properties of the electrolytes used. The highest (3-4)x heat transfer enhancement in comparison with plain tube in the nucleate boiling regime was achieved on coatings, obtained in a silicate and phosphate electrolytes. An additional surface treatment of the porous ceramic coatings in silane solution allows a multiple intensification of the heat transfer, mainly due to the change of the surface wettability. 

The intensification of heat transfer at low heat fluxes, typical of heat exchangers in refrigeration and cryogenic equipment, is provided by a significant reduction in the temperature difference at the onset of nucleate boiling.

It is well known that the heat transfer coefficients at boiling of different freons under the same conditions can differ by several orders of magnitude. It is therefore of great scientific and practical importance to analyse the heat transfer performance of different refrigerants, including new refrigerants with low ODP and GWP (R245fa, R1233zd), under the same conditions and on surfaces with the same characteristics. 

The results obtained are important for the development of new high-efficiency methods of heat transfer intensification at boiling in power engineering, chemical technologies, refrigeration and cryogenic industries, including large-scale natural gas liquefaction plants, evaporators for water desalination and the food industry.

Acknowledgment: This research was conducted in accordance with RSF-NSFC grant 25-49-00133 (Analysis of the influence of refrigerant properties on heat transfer during boiling and evaporation in falling films) and the state assignment of the Kutateladze Institute of Thermophysics SB RAS 

No. 121031800216-1 (Analysis of the influence of surface treatment methods on heat transfer in falling films).

Education: Tomsk Polytechnic Institute, specialization 'Nuclear Power Plants and Installations (Engineer-Thermal Physicist)' 1971, Tomsk, Russia.

Position: Leading Researcher in the Laboratory of Low-Temperature Thermophysics, Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.

Doctoral thesis - 'Heat and mass transfer in two-phase flows on surfaces and in complex-shaped channels' 2019.

Research topics: Heat and mass transfer and hydrodynamics in two-phase flows on surfaces of complex geometry, including heat transfer during boiling and evaporation in falling films on structured surfaces and porous coatings of various materials; hydrodynamic and mass transfer in separation columns with structured packing in the cryogenic distillation process. The main publications are devoted to experimental studies of heat and mass transfer of two-phase flows in channels of complex geometry, the intensification of heat transfer during boiling and evaporation in falling films of refrigerants on the surface of vertical and horizontal pipes with complex macro- and microstructure of different scales. More than 160 publications in the leading Russian and International journals, indexed by Web of Sciences and Scopus.

International collaboration: participant in projects on separation of binary mixtures in distillation columns with structured packing - Air Products and Chemicals, USA; Tianjin University, China; Institute of Chemical Engineering, Bulgarian Academy of Sciences, Bulgaria; BASF Company, Germany; joint RFBR and DST grant with Indian Institute of Technology, Bhubaneswar, India; joint RSF grant with Xi'an Jiaotong University; contract with Huawei company, China.

Participation in organization of scientific events: International Workshop ISHM (2014-2018), International Conference IWHT2019; Member of the Scientific Committee of the International Congress CHISA, section 'Distillation and Absorption' (2016, 2018). 

Peer review of articles in Thermophysics and Aeromechanics, Theoretical Foundations of Chemical Engineering, Applied Thermal Engineering, International Journal of Heat and Mass Transfer, Experimental Thermal and Fluid Science, Chemical Engineering and Processing - Process Intensification, Chemical Engineering Science, Journal Enhanced Heat Transfer, MDPI Energies and others.   

Honours and awards: Certificates of Appreciation from Air Products and Chemicals, USA (1995-2005); International Prize named after Academician A.V. Lykov of the National Academy of Sciences of Belarus, 2020; 300th Anniversary Medal of the Russian Academy of Sciences, 2024.