Hyun-Spalding model

Forces for Hyun-Spaldina Model forwarding force at the barrel wall and centered on surface. force due to pressure and centered on surface. 

Fg plays a similar role to that of the unknown force, in Campbell s models. Fg is resolved into forces Fj and F, and acts at an angle W to F (the flight edge). These forces are in a plane parallel to the screw root surface. The new static force balance yields  

However, the third term of Eq. A5.14 can be simplified using a torque balance about the axis A of Fig. A5.5  

Coupling Eq. A5.15 with forces A, F4, and as defined using the screw core friction factor, yields the following  

The remaining forces can be defined using pressures, coefficients, and surface areas  

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The coefficients of friction,and f are dependent on temperature, pressure, and velocity (Hyun-Spalding model [2]). 

Hyun, K.S. and Spalding, M.A., A New Model Eor Solids Conveying In Single-Screw Plasticating Extruders, SPEANTEC Tech. Papers, 43, 211 (1997)... 

Campbell et al. and Yamamuro et al. assume a form for (or F ) and then determine the solids conveying angle (p. Hyun and Spalding calculated q> using a force balance and two torque balances. Campbell and Dontula and Yamamuro et al. did not use a torque balance in their analysis. The following is a list of assumptions from all the models discussed. Additional assumptions will be added as needed. Assumptions that do not have keys were used by all authors ... 

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