Simplified equilibrium rate model ERM

Some flashin to maintain vapour-liquid equilibrium 

No flashing (non-equilibrium flow) until choke point 

It is recommended that the method given in equations (6.10) and (6.11) be used to obtain dPydT (see also 6.5.2). The simplified ERM can be rewritten by making use of the Clausius-Clapeyron thermodynamic relationship which introduces the following further requirement  

(This will not be true for mixtures with a wide boiling range). 

The simplified ERM is very convenient in that all the properties can be evaluated at the stagnation conditions in the reactor. The method may be appropriate for relief sizing for vapour pressure systems when flow is to be via a safety valve. Discharge coefficients for two-phase flow through safety valves are discussed in 9.7.1. - 

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This, method121 is applicable if the above assumptions are valid and the flow is of a flashing liquid. The method makes use of the simplified Equilibrium Rate Model (ERM) (see 9.4.2). -. ... 

Fauske s method14,51 (given below) is based on emptying the reactor (or achieving vapour/ liquid disengagement) before the pressure has risen from the relief pressure to the maximum accumulated pressure in a vented system. The method incorporates the simplified equilibrium rate model, ERM, for saturated liquid inlet (see 9.4.2) together with the Clausius-Clapeyron relationship (discussed in 6.3.3). The method makes use of adiabatic experimental rate data for the runaway, whose measurement is described in Annex 2. 

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