A Spreadsheet Application for Evaluating Two-Phase Emergency Venting Transients Utilizing an Interface to a Thermodynamic Property Package

This paper presents a numerical method for determining emergency relief requirements for a top-vented cylindrical vessel or batch-type chemical reactor through an ideal nozzle using a spreadsheet application interfaced to a CAPE-OPEN compliant thermodynamic package. A calculation algorithm based on the DIERS recommended homogeneous equilibrium model are presented for single and binary systems. Fluids exhibiting partial vapor-liquid separation with either churn-turbulent or bubbly flow behavior were considered and disengagement parameters greater than unity. A vessel condition subjected to energy input from an uncontrolled external source such as fire was considered with no chemical reaction. Analytical expressions are used; however, rigorous solution is achieved by relaxing the assumptions of constant physical properties and constant relieving vent rate of the fluid. The use of a spreadsheet significantly simplifies the tedious unsteady state emergency relief calculations while the use of AspenProperties® provides reliable thermodynamic data throughout the venting transients.