Engineering: Heat Transfer in Extruders II—Simultaneous Heating and Cooling

摘要

In my last column (Cereal Foods World, November-December 2009), I began a discussion about heat transfer in extruders. The issue of heat losses was discussed and an approximate calculation of the relative heat losses in laboratory and commercial extruders was demonstrated. The calculations illustrated that the heat losses, as a fraction of the total mechanical energy input by the extruder, were negligible in the commercial scale extruder, but were quite significant in the laboratory extruder. The source of this difference was explained as the ever decreasing ratio of extruder surface area to throughput and the size of the extruder is increased.