Режимы с интенсификацией теплообмена при испарении в тонких горизонтальных слоях жидкости при пониженных давлениях

The influence of structures formed during the evaporation and boiling of a liquid (n-dodecane) in thin horizontal layers on heat transfer has been analyzed. Structures shaped with the shapes of funnels and craters are formed at low pressures in liquid layers with thicknesses above the capillary constant under the action of a vapor recoil force. Increasing pressure leads to the onset of bubble boiling. It is established that the formation of these structures in the regime of intense evaporation at low reduced pressures leads to an about 70% increase in the heat-transfer coefficient at analogous layer thicknesses in comparison to the case of bubble boiling.

Dynamics of the Liquid Microlayer Underneath a Vapor Bubble Growing at a Heated Wall

Evaporation of the liquid microlayer developing underneath a bubble in the initial (inertia controlled) phase of its growth can be a significant vapor source in the later (heat-diffusion controlled) phase of bubble growth. In the literature, representation of this microlayer is typically limited to a very short (order of microns) region near the apparent Triple Phase Line (TPL) between the bubble and the wall. However, experimental observations show that the microlayer may actually extend hundreds of microns beyond the TPL region. Guided by this observation, we develop a simple model to predict the time evolution of the extended microlayer, and the associated corresponding evaporation rate and heat flux underneath a bubble. The model is derived as a special case of the complete governing equations, which account for the complicated effects of disjoining pressure, capillarity, vapor recoil and interfacial resistance. The predictions of the model are in reasonable quantitative agreement with the experimentally observed behavior of the microlayer.

Effects of Varied Physical Mechanisms on the Evolution of Lubricant Interface During Heat-Assisted Magnetic Recording

A concoction of various forces and physical effects (both mechanical and chemical) come into play in the depletion and evolution of the lubricant on the media during a heat-assisted magnetic recording (HAMR) process. They include the air-bearing shear and pressure, capillary pressure, thermo-capillary stress, disjoining pressure, lubricant desorption and the vapor recoil mechanism. The effects of these mechanisms and their complex interplay to stabilize/destabilize the lubricant interface is studied here numerically. Results for Z-type perfluropolyether (PFPE) lubricants with different polydispersity indices (PDI) are summarized.