DETERMINATION OF SPECIFIC MECHANICAL ENERGY-DISTRIBUTION ON A TWIN-SCREW EXTRUDER

The distribution of specific mechanical energy (SME) dissipated inside a co-rotating, self-wiping, twin-screw extruder was estimated by cond ucting energy balances on each zone of the extruder. SME dissipation w as studied under three different steady state conditions in which the zone before the die was kept adiabatic or under constant cooling or un der constant heating. Infrared temperature probes and extended thermoc ouples were used to measure the bulk temperature of the corn meal. Hea t flow sensors were used to measure the heat loss from the barrel surf aces. Total SME was calculated by measuring torque, screw speed, and m ass flow rate. Of the total SME dissipated 95-98% was accounted for fr om energy balance calculations on each zone. Estimated maximum SME dis sipation was found to occur in the zone prior to the die for adiabatic and constant cooling situations. However, in the case of constant hea ting, energy balance measurements indicated that most of the SME was d issipated in the middle zones of the extruder. The reasons for this ar e discussed. (C) 1997 Silsoe Research Institute.