Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
In this study, frost was grown on microgrooved and baseline
brass samples under specific operating conditions and a
comparison of condensation, frosting and defrosting pattern on
microgrooved and flat brass surfaces were carried out
experimentally. The surfaces were fabricated by mechanical
micro-machining process and no chemical alteration of the
surface was conducted. It was found that the shape, size and
distribution of condensed water droplets and subsequent frost
structure are significantly affected by the micro-scale roughness
on the surface. The condensed water droplets took an elongated
shape and then coalesced along the pillars and grooves on
grooved surfaces giving a parallel brick-like frosting pattern.
The frost structure on the grooved surface was different than
that on the flat surface and frost crystal exhibited more
directional growth in the parallel to the surface direction, with
numerous ice-flakes growing in the perpendicular and angular
directions to the grooves. This non-uniform growth of the frost
layer also gave the appearance of a spongy and loose frost
structure and suggested the formation of less dense frost.
Qualitative study of the spatial and temporal distribution of
retained condensate on the grooved and plain brass surfaces
after defrosting were carried out by analyzing thermal images
of the sample surface during the defrosting period. Findings of
this of this study can give significant insight about the frost
properties and defrosting and condensate retention behaviour of
heat transfer equipments with embedded microgrooves.
