Study of the Effects of Microgroove Geometry on Frost Structure

The variation in the frost structure on a number of microgrooved brass surfaces is examined through an experimental study. The microgrooved samples are 45 mm x 45 mm in dimension with a broad range of groove dimensions. Frost is grown on these microgrooved surfaces under natural convection for a range of plate temperature (-8 to -18 C) and relative humidity (30-70%) conditions. The frost structure on the microgrooved surfaces, especially at the early stages of frost formation, is found to be significantly affected by the groove geometry (i.e. groove depth and pillar width). Coalescence of the condensed and hence frozen droplets, covering multiple pillars and grooves, is found to occur more frequently on the surfaces with shallow grooves and/or narrow pillars. For surfaces with intermediate groove depth and pillar width, a regular (brick-wall-like) frost pattern on the pillar surface is observed. Thickness and density of frost layer on the microgrooved surfaces are also found to vary with the dimension of the grooves in frost cycles up to 4 hours long. The relationships between frost structure, frost properties, and frost melt-water drainage is discussed, emphasizing the importance of these morphological features.