Controlled cooling is an essential part of manufacturing polyethylene stretch film. The process starts with granulated polyethylene raw product with very low strength, and develops thin, clear, strong film used in a variety of applications. It does this by melting, extrusion, “casting” and winding. See Figure 1 for a typical system diagram. “Casting” is forming and cooling at the same time. The extruded polymer is stretched and cooled on large, chrome-plated rollers with cooling water flowing inside. Thinner film is for manual use, like wrapping around food products. Thicker, stronger product is made for machine use, like automatically wrapping pallets of concrete bags.
Air compressors are very effective heaters. Over eighty percent of the energy input from the motor is converted into compression heat. That heat must be rejected from the compressor package in a way that maintains a variety of temperatures in a reliable manner. The laws of physics demand that the air temperatures go up with compression.
