The purpose of door heaters is to provide air of a sufficient velocity (outlet velocity over 2,000 FPM) and temperature to temper incoming air and to minimize cold air infiltration. By adding a high-velocity nozzle to our unit heaters, we can use them as door heaters to temper cold air admitted through open loading-dock doors Cores are available for steam or liquid, allowing units to be applied in different plant areas with various heating media.
Two fin types are typically used in the manufacture of door heaters. The L fin has a foot at its base and is tension-wound on knurled tube material. The L-shaped base provides a large contact area between the tube and the fin, ensuring effective, long-lasting heat transfer. The L fin is recommended when tubes and fins are of the same material. (See drawing.)
The keyfin is manufactured by forming a helical groove in the tube surface, then winding the fin into the groove. The displaced metal from the groove is then peened against the fin. This means a tight fit between the fin and the tube. The keyfin is the superior design for dissimilar tube and fin material. (See drawing.)