Frictional factor general temperature dependence

Equation 2.2 shows that D is determined by the interplay of the thermodynamic factor dH/dc and the friction factor /. In general, the friction factor is expected to increase monotonically with increasing c rind decrease with rising temperature. On the other hand, as can be deduced from the known information about osmotic pressure, the thermodynamic factor as a function of c varies in complex ways with solvent quality and temperature. Thus, the concentration dependence of D for a given polymer should exhibit a variety of features depending on solvent conditions. 

In isothermal flow, the flowing temperature is constant. Constant temperature means the viscosity is constant. Viscosity generally depends on temperature pressure has negligible influence on the value of viscosity (unless the pressure drop is extremely high to influence the value of viscosity). The value of the Reynolds number is expressed as dvp/p. For isothermal flow and with comparatively low pressure drop condition, the Reynolds number as well as the friction factor will remain xmchanged. 

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