Insideout Methods

The inside-out algorithm has become one of the most popular methods because of its robustness and its ability to be applied to the solution of a wide variety of columns. The inside-out concept was developed by Boston (1980). Russell (1983) presented an inside-out method that works well for many refinery frac-tionators. The inside-out methods are now the methods of choice for mainstream column simulation and have displaced other methods.

In older methods, the MESH variables of temperatures, total flow rates and component flow rates are the primary solution variables and are used to generate the K values and enthalpies from complex correlations. These methods update the MESH variables in an outer loop with the K values and enthalpies updated whenever the MESH variables change. The inside-out concept reverses this by using the complex K value and enthalpy correlations to generate parameters for simple K value and enthalpy models. These parameters are unique for each stage and become the variables for the outside loop. The inside loop consists of the MESH equations and is a variation on other methods. In every step through the outside loop, the simple models are updated using MESH variables from the inside loop. This sets up the next pass through the inside loop. Since the K values and enthalpies are simple, the inside loop works well for a wide range of mixtures and is little affected by the nonideality of mixtures or the quality of the initial values.

The outer loop K value model is based on a simple composition-independent K method:

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

Get My Free Ebook

Post a comment