Equation for Systems of Variable Density

Substituting Equation 5-317 into the ideal gas law gives the total volume V  

Assuming that the total pressure is constant (i.e., when the pressure drop in the reactor is neglected), Equation 5-320 becomes 

However, in practice, eA is much more easily calculated for a given reaction by directly using Equation 5-18 

The expansion factor eA can be determined if V is known at some nonzero value of X. The most likely condition at which V can be determined is at total conversion, where the volume is readily computed from the stoichiometry. Then 

The same reaction with a feed of 25% NH3 and 75% inerts yields 

Introduction to Reactor Design Fundamentals for Ideal Systems 373 

However, in praetiee, is mueh more easily ealeulated for a given reaetion by direetly using Equation 5-18 

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