SELF-POSITIONING SYSTEM FOR ELECTRIC RESISTANCE DEFROST HEATING ELEMENTS (US PATENT NO. 7,712,327)
Air-cooling heat exchangers operating at temperatures below the freezing point of water (32F) will accumulate frost on fin and tube surfaces which must be removed periodically in order to maintain system cooling capacity. One method of removing frost involves tubular electric resistance heating elements inserted in vacant tube spaces within the heat exchanger fin bundle. These heating elements are energized periodically to warm the frosted fin and tube surfaces sufficiently to melt the frost which is then captured as liquid water and removed from the space being refrigerated. After all of the frost has been melted and removed from the heat exchanger, the heating elements are de-energized and the heat exchanger is cooled back down to refrigerating temperature. This periodic removal of frost is termed a “defrost cycle”.