A model consisting of a plug flow reactor (PFR) in series to a continuous stirred tank reactor with a fraction of flow held up in a stagnant dead volume has been developed. The model was tested against the experimental measurements obtained from a single screw extruder fed with rice flour and the literature data. The fitting of the model to the experimental data was very good with correlation coefficients (r(2)) higher than 0.97. Through the paired comparison, no difference exists between the literature data and the model at the 95% confidence level. Feed rate and screw speed showed strong effects on the fraction of PFR (P) which was in the range of 0.36-0.65. The fraction of dead volume (d) varied from 0.04 to 0.16. Both the mean residence time and P were further expressed as functions of the screw speed and feed rate. With the average value of d for a specific screw profile, the residence time distributions were estimated from the operating conditions. The results demonstrated that no difference existed between the calculated values and experimental data at the 95% confidence level.