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LEADERS IN MECHANICAL ENGINEERING LECTURE SERIES - SPRING 2008
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Gas-Liquid Interface Deformations in Thin Locally Heated Liquid Films
Lecturer: Yulia Kabova, Russian Academy of Sciences - Novosibirsk, Russia
Original Air Date: Friday, May 9th at 2:00pm
Abstract: The levels of energy generation in high-speed computer chips are now approaching very high values (up to 100-150 W/cm2), and they are on the edge of exceeding the capabilities of today’s air-cooling technology. Thin liquid films may provide very high heat transfer intensity and may be used for cooling of microelectronic equipment. A particularly promising technological solution, allowing to reach high heat fluxes and to decrease space and mass of cooling equipment, is a set-up where heat is transferred to a thin liquid film driven by a forced gas or vapor flow of the same liquid in a micro or minichannel. Main objective of the present work is to create a mathematical model which allows getting in-depth understanding of the physics of two-phase flow of thin locally heated liquid film driven by gravity and gas flow in a micro- or minichannel under a variety of parametric influences.
Three-dimensional time-dependant mathematical model for calculation of gas-liquid interface deformations and evolution of temperature and velocity fields is developed. Effects of surface tension, temperature dependent viscosity and thermocapillarity are taken into account. Thin layer approximation technique is used.
The effect of mutual location of heaters on a substrate as well as the effect of size of hot spots on 3-D structures, occurring at the film surface, is investigated to define main features of the film dynamics. Calculations are carried out for two equal rectangular heaters arranged in a row (in spanwise or streamwise directions).
The influence of a temperature dependent viscosity on film deformations is investigated. A generalized analytical formula for film thickness as a function of liquid flow-rate is obtained. Criterion for appearance of a second order deformation of the free surface before the bump up to flow is found analytically. For the case of thin nonisothermal liquid film flowing under action of gravity force and co-current gas flow, which create the tangential force on the gas-liquid interface, the effect of gravity as well as the effect of gas speed is studied to define main features of the film dynamics.
Additional Materials: PDF of the slides can be viewed here
