Conversion heat transfer coefficient relationships

Heat transfer can, of course, be increased by increasing the agitator speed. An increase in speed by 10 will increase the relative heat transfer by 10. The relative power input, however, will increase by 10In viscous systems, therefore, one rapidly reaches the speed of maximum net heat removal beyond which the power input into the batch increases faster than the rate of heat removal out of the batch. In polymerization systems, the practical optimum will be significantly below this speed. The relative decrease in heat transfer coefficient for anchor and turbine agitated systems is shown in Fig. 9 as a function of conversion in polystyrene this was calculated from the previous viscosity relationships. Note that the relative heat transfer coefficient falls off less rapidly with the anchor than with the turbine. The relative heat transfer coefficient falls off very little for the anchor at low Reynolds numbers however, this means a relatively small decrease in ah already low heat transfer coefficient in the laminar region. In the regions where a turbine is effective,... 

Equation (8) provides a general relationship between the reactor temperature profile and the operating parameters. In relating the system heat transfer to the conversion-molecular weights relationship for a reactor of fixed size, the heat transfer coefficient emerges as the correlating parameter. 

Figure 14, Molecular weight-conversion relationship (computer simulation— reactor of a fixed geometry for a given initiator system) (h) heat transfer coefficient...

Optimized molecular weight-conversion relationship is related to the system heat transfer coefficient. The degree of conversion improvement from improved heat transfer depends on the average molecular weights of polymer being produced for a given initiator system. 

An exothermic co-polymerization was carried out in a 12-liter batch kneader reactor. Polymer temperature, shaft torque, cooling medium inlet and outlet temperatures, and conversion wctc measured as a fimetion of batch reaction time (residence time) for several batch trials. Reaction kinetics, shaft torque relationships, and heat transfer coefficients were determined from this data and a model for a continuous reactor was developed. Continuous trials were performed using a 31-liter reactor and the results from these trials were compared against the model predictions. 

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