要約

The methods of heat and mass transfer enhancement have been widely applied in the element of power equipment. The most popular methods of heat and mass transfer enhancement under convection are the use of the entry section effect, artificial flow agitation in the wall layer or over the entire flow section by circular or spiral grooves, dimples, finned surfaces, twisted tapes, screws and coiled pipes, jet impingement of heat carrier on a surface, porous and brush inserts, effect of ultrasonic vibrations, the influence of wall intensifiers of heat removal on laminar-flow heat transfer. To intensify heat transfer in boiling, extensive use is made of porous coatings, since the methods of artificial flow agitation are less efficient here. The enhancement of heat transfer in condensation is achieved by creating drop condensation, whereas in case of film condensation, knurling, finning, and alteration of the slope of the surface are employed to enhance heat transfer. Combined methods of heat transfer intensification are based on the use of at least two methods of increasing the heat removal intensity. For example,
– the use of artificial roughness of the surface and of a twisted tape;
– the use of helical pipe and of porous coating;
– the use of circular knurling and flow twisting in helical pipes.
The enhancement of heat and mass transfer make it possible to improve the equipment characteristics. Incorporation of grids-intensifiers into the structure of fuel assemblies made it possible to increase the power of energy block by a factor of 1.5. This new edition the survey of investigations in the field of heat and mass transfer enhancement on the macro-, micro-, and nanoscales. The available investigations into heat transfer and hydrodynamics of dimpled surfaces are considered in detail. Consideration is given on the thermohydrodynamics on the micro- and nanoscales: heat transfer under condensation on macro- and microrough surfaces, heat transfer with boiling on surfaces with porous coating and protrusions that form a homogeneous relief, heat transfer in the presence of convection in micro channels, the appearance of slipping on the wall in liquid flow over an ultrahydrofobic surface, the influence of molecular layers of surfactant formed on surfaces on the hydraulic resistance of pipelines.