ISSN Online: 2377-424X
ISBN Print: 978-1-56700-474-8
ISBN Online: 978-1-56700-473-1
International Heat Transfer Conference 16
EVAPORATION AND BOILING IN THIN GAP
Abstract
A vapor washing treatment has been recently proposed for disposal of electric transformers, a main part of which
is laminated metal plates immersed in insulating oils. To study its detailed mechanism, we have experimentally
investigated transport and evaporation dynamics of liquid confined in a thin gap between solid plates under
reduced pressure using a model system. As a test liquid, we use deionized water and ethanol. To visualize the
liquid motion in the gap, we adopt sand-blasted glass plates with specified surface roughness. When a test liquid
is sandwiched between the glass plates, incident LED light passes through the plates without much scattering;
once the liquid starts to evaporate, dried surface of the plates scatters the light and we can monitor the flow
pattern. Based on the transmitted light intensity, the whole plate area is categorized into three regions, i.e.,
completely wet, completely dried, and semi-dried one, from which the evaporation rate is successfully evaluated.
Among many control parameters, the effect of surface roughness is mainly discussed in this paper. We show that
an extended Lucas-Washburn model for liquid imbibition in porous media can explain the liquid transport
dynamics in such a thin gap.