Transfer units simplified approach

I umber of Transfer Units. Eor relatively dilute systems the ratios involvingjgj, jy gj, and 1 — y approach unity so that the computation of from equation 50 and -Nq from equation 49 may be simplified to... 

To simplify the subsequent treatments, we make the following five assumptions (i) polymer particles contain at most one radical, (ii) a radical with no longer than s monomer units can desorb from and enter into the particles with the same rate irrespective of chain length, (iii) instantaneous termination occurs when another radical enters the particle already containing a radical, (iv) no distinction is made between radicals with or without an initiator fragment on its end, and (v) water-phase reactions such as propagation, termination, and transfer i an be neglected from a kinetic point of view, as shown in Section II,A, Under these assumptions, the rate coefiident for radical desorption from the particles is derived with both deterministic and stochastic approaches,... 

To approach an artificial model from the chemical point of view, there is a need to simplify it in a basic donor-acceptor system, formed by one electron donor unit (D) and one electron acceptor unit (A), linked together throngh covalent or noncovalent interactions (Figure 2.23). This simple system (also called dyad) should efficiently give a long-lived CSS after irradiation with light. Donors supply a double function they not only act as excitation-harvesting antennas but also as primary electron donors that transfer electrons to the acceptor. 

Modelling of CFB systems is in a period of rapid development. Practical models, based on simplified hydrodynamic schemes such as the core-annular approach, have proved effective in allowing hydrodynamics and heat transfer to be scaled from pilot units. More fundamental approaches to transfer coefficient prediction should soon reduce the dependence upon empiricism, and allow greater confidence. 

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