TY - JOUR
T1 - Prediction of temperature profiles in twin screw extruders
AU - Mohamed, Ibrahim O.
AU - Ofoli, Robert Y.
PY - 1990
Y1 - 1990
N2 - A model incorporating viscous dissipation effects and a heat transfer coefficient based on the Brinkman and Graetz numbers is presented for predicting the temperature profiles of non-Newtonian food doughs in a twin-screw extruder, assuming uniform product temperatures in the direction normal to the screw shafts. Experimental measurements were obtained to evaluate the model for three screw configurations: 30° forwarding paddles (30F), feed (two-start or double-flighted) screws and single-start (single-flighted or single-lead) screws. Model predictions were well within engineering accuracy for 30F paddles and feed screws under all experimental conditions. Predictions for single-start screws were inaccurate, with deviations of up to 50%. In general, results indicate that the one-dimensional energy equation is sufficient for heat transfer analysis of extruder sections configured with mixing paddles and feed screws, particularly at high flow rates, high RPM, or combinations of the two variables. However, the level of mixing provided by single-start screws over the RPM and flow rates used in this study does not justify the assumption of uniform temperatures in the transverse direction. For these screws, at least a two-dimensional formulation of the energy equation must be used.
AB - A model incorporating viscous dissipation effects and a heat transfer coefficient based on the Brinkman and Graetz numbers is presented for predicting the temperature profiles of non-Newtonian food doughs in a twin-screw extruder, assuming uniform product temperatures in the direction normal to the screw shafts. Experimental measurements were obtained to evaluate the model for three screw configurations: 30° forwarding paddles (30F), feed (two-start or double-flighted) screws and single-start (single-flighted or single-lead) screws. Model predictions were well within engineering accuracy for 30F paddles and feed screws under all experimental conditions. Predictions for single-start screws were inaccurate, with deviations of up to 50%. In general, results indicate that the one-dimensional energy equation is sufficient for heat transfer analysis of extruder sections configured with mixing paddles and feed screws, particularly at high flow rates, high RPM, or combinations of the two variables. However, the level of mixing provided by single-start screws over the RPM and flow rates used in this study does not justify the assumption of uniform temperatures in the transverse direction. For these screws, at least a two-dimensional formulation of the energy equation must be used.
UR - http://www.scopus.com/inward/record.url?scp=0025639848&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0025639848&partnerID=8YFLogxK
U2 - 10.1016/0260-8774(90)90025-4
DO - 10.1016/0260-8774(90)90025-4
M3 - Article
AN - SCOPUS:0025639848
SN - 0260-8774
VL - 12
SP - 145
EP - 164
JO - Journal of Food Engineering
JF - Journal of Food Engineering
IS - 2
ER -