Frequency factor controller settings

It is also essential that the period of the ac stimulus not be so long that convection becomes a factor within a few cycles. The lower frequency limit was set here at 1 Hz because convection would become a problem in the range of several seconds in most liquid systems with water-like viscosity. Current equipment for EIS can operate at much lower frequencies (as low as 10 jU,Hz) and can be usefully applied in the low-frequency (long-time) regime when the processes being examined are not controlled by convection. Examples include transport or reaction at a solid-solid interfaces or diffusion and reaction in extremely viscous media, such as glasses or polymers. 

A new set of flow characteristics gradually emerges as the concentration of polymer becomes large. The solution viscosity loses its direct dependence on solvent viscosity and comes to depend on the product of two parameters a friction factor C which is controlled solely by local features such as the free volume (or alternatively the segmental jump frequency), and a structure factor F which is controlled by the large scale structure and configuration of the chains (16) ... 

A relay-feedback test on the reactor temperature controller is used to obtain the ultimate gain and frequency (K, = 64 and Pv = 10 min), using a 50 K temperature transmitter span and assuming the maximum cooling water flow is twice the steady-state value. The Tyreus-Luyben settings give oscillatory response, so the controller gain is reduced by factor of 2 (Kc = 10, t = 1320 s). 

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