Conditions at inlet to the relief system

The conditions at the inlet to the relief system, i.e. the assumed upstream conditions for the flow calculation, affect the calculated flow. It is therefore important to have both an appropriate flow model and appropriate assumptions about the upstream conditions  

When calculating G, the pressure in the reactor at which the calculation is required will be known (see Chapter 5). The corresponding temperature and composition will be needed to evaluate physical properties. 

One of the most significant, parameters describing the inlet condition is the phase split at this position. This can be described by either the mass fraction of gas/ vapour, x, or the volume (void) fraction, a. These two parameters are related  

The value of x or a will depend on the assumptions made about the flow regime in 

Unless otherwise stated, the relief sizing methods given in this Workbook assume 

---