Density

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Navigation: User Guide -> Density

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Overview

The Density of a substance, or mixture of substances, is defined as the ratio of the mass to the volume. Density is a function of temperature and pressure, but pressure does not have a measurable effect on most liquids and solids.

In SysCAD the user enters the density of the pure species in the Species database.

Implementation in SysCAD

  • Entering Density Data in the Species Properties Database - the user enters the density of the pure species in the species database.
  • Density in Units and Pipes - This describes the information shown in the access window of pipes, tanks, etc. SysCAD will calculate and display the density of the overall mixture and of each Phase (solid, liquid and gas), as well as the density of the slurry = solid + liquid. (The user may have to click on the All fields button at the top of the Access Window to see all of these fields.)
  • Density Information in a Project - The density information used in a project can be seen in the Species Properties Access Window (Species - View Properties).

SysCAD allows a number of different methods of calculating the density of mixtures. These will be described separately below:

Mass Weighted Mean

  1. This is the standard method of calculating the density of a mixture in SysCAD.
  2. Currently, if the user does not use an implemented species model, this method will ALWAYS be used to calculate the density of the Solid phase.

Ideal Gas Density

  • Ideal Gas Density - the user may specify 'Ideal Gas Density' for any gas species in the species database. SysCAD will then use this to calculate the density of gas mixtures.

Density Correction for Liquid Species

  1. The density of a solution containing liquid species changes according to the mass fraction of dissolved species in solution. However, it does not usually change in a simple mass weighted mean fashion.
  2. In these cases you may enter a density correction function instead of a fixed value for density in the Species Database.
  3. This Density Correction function describes the solution density as a function of solute mass fraction for a solution containing a SINGLE solute.
  • Density correction for liquid mixtures - this describes the methodology used by SysCAD to calculate the density of the liquid solution using Density correction functions.
  • Setting Density Correction Method - the user may change the method used to calculate the liquor density by going to View - Plant Model and changing the Density Correction Method on the Species tab.

Implemented Species Models

In this case SysCAD will use a specified empirical equation to determine the density of the liquor or slurry mixture. (Please see the Bayer species model for an example)

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