Development of a three dimensional pressure-volume-temperature model for use in teaching environments

Abstract

Three phase equilibrium can be a difficult concept to comprehend, since it has geometric relationships in three dimensions. A teaching aid was developed to aid in explaining phase diagrams to student. The curve was made from transparent sheets of acrylic so the saturation curve could be projected onto the wall from the model. Virial Equations of State, Van der Waals Equation, Benedict-Webb-Rubin Equation, and Redlich-Kwong Equation were evaluated to find the best formula to design the model with. A three dimensional curve for water and carbon dioxide was built using Redlich-Kwong. The major issues with the hardware were scaling inconsistencies between the two plots and incorrect trends on the solid/liquid transition line. These issues can be repaired by adjusting the scale on the matlab file where the curves were generated and consulting experimental data where the Redlich-Kwong approximation fails.