Many of the best reasons to insist on Armstrong unit heaters are ones you never even see. Components like motors, bearings, tubes, enclosures and fins are heavy-duty to ensure lasting performance.
Armstrong’s options for fin material, pitch, height and type, for example, help explain why our heating cores last much longer and perform with greater efficiency than competitive units. These factors all have a bearing on heat transfer. Knowing how to balance these and other factors is the key to a cost-effective solution. That knowledge is perhaps the most important of Armstrong’s many hidden benefits.
Two fin types are typically used in the manufacture of unit 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.)
Basic units may be used in either horizontal or two-way vertical-discharge configurations. The addition or substitution of a four-way vertical louver section produces a square discharge pattern. Cores are available for steam or liquid, allowing units to be applied in different plant areas where various heating mediums my exist.