Experimental investigation of adverse effect of frost formation on microchannel evaporators, part 1: Effect of fin geometry and environmental effects

This study experimentally investigated the frost growth on louvered folded fins in microchannel heat exchangers when used in outdoor air-source heat pump systems. The effects of surface temperature, fin geometries, and air environmental conditions were studied. The overall aim was to isolate and quantify the effect of geometry from surface temperature effects. Experimental data of frost weight, local frost thickness, air pressure drop across the coils, time of frost–defrost cycles and heat transfer rates were recorded. Data showed that the frosting time and the frost growth rates depended mainly on the local fin surface temperature. Lower fin density was beneficial because it delayed the blockage of the air flow. The fin length and fin depth had minor effects on frosting performance. The air humidity had a fairly significant effect on rate of frost formation while air velocity seemed to have a small effect on the frost growth rate.

► Frost formation on microchannel coil was experimentally investigated.
► A novel methodology was introduced to measure and control surface temperature.
► Effect of geometry was isolated and evaluated.
► Lower fin density samples had longer frost times.
► The fin depth and fin height had minor effect on frosting time.