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 conducting energy balances on each zone of the extruder. SME dissipation was studied under three different steady state conditions in which the zone before the die was kept adiabatic or under constant cooling or under constant heating. Infrared temperature probes and extended thermocouples were used to measure the bulk temperature of the corn meal. Heat flow sensors were used to measure the heat loss from the barrel surfaces. Total SME was calculated by measuring torque, screw speed, and mass flow rate. Of the total SME dissipated, 95-98 % was accounted for from energy balance calculations on each zone. Estimated maximum SME dissipation was found to occur in the zone prior to the die for adiabatic and constant cooling situations. However, in the case of constant heating, energy balance measurements indicated that most of the SME was dissipated in the middle zones of the extruder. The reasons for this are discussed.