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5: Phase Diagrams IV

  • Page ID
    7502
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    Learning Objectives
    • Module Goal: To familiarize you with the basic concepts of Phase Diagrams as a means of representing thermodynamic data.
    • Module Objective: To familiarize you with the process of extracting quantitative compositional information from phase envelopes.

    • 5.1: Effect of Composition on Phase Behavior
      This page examines how pure component pressure-temperature (P-T) diagrams affect the P-T behavior of binary mixtures, specifically Methane and Ethane. It highlights that due to Methane's higher volatility, its P-T curve is leftward, while Ethane's is rightward. The phase envelopes for different mixture compositions are found between the pure component curves.
    • 5.2: Px and Tx Diagrams
      This page emphasizes the significance of composition variations in thermodynamic diagrams, particularly "P-x" and "T-x" diagrams for binary systems. It introduces "zi" for overall mixture composition while using "xi" and "yi" for liquid and vapor compositions, respectively, to prevent confusion. Additionally, it outlines the P-x diagram's bubble and dew point curves and their connection to phase regions at constant temperature, contrasting this with the T-x diagram.
    • 5.3: The Lever Rule
      P-x and T-x diagrams are quite useful, in that information about the compositions and relative amounts of the two phases can be easily extracted. In fact, besides giving a qualitative picture of the phase behavior of fluid mixtures, phase diagrams can also give quantitative information pertaining to the amounts of each phase present, as well as the composition of each phase.
    • 5.4: Ternary Systems
      This page covers ternary systems with three components, emphasizing their practical significance over binary systems, using examples like air and natural gas. It introduces pseudo-components, categorizing multiple components for simplification, and explains ternary phase diagrams via a triangular coordinate system to depict concentration relationships.
    • 5.5: Multicomponent Mixtures
      This page discusses the challenges of pictorially representing systems with multiple components, highlighting the effectiveness of simpler diagrams for two or three components. It emphasizes that real-world mole fractions of components often change, requiring direct calculations from physical models to evaluate phase behavior accurately. This topic will be further examined in upcoming modules of the course.
    • 5.6: Action Item
      This page covers the P-T phase envelopes for binary mixtures of Methane and Ethane at different compositions, detailing their vapor pressure curves. It presents eight mixtures, from nearly pure Methane to pure Ethane, and highlights the applications of this data for creating P-x and T-x diagrams, as well as assessing temperature conditions for liquid state percentages under specific pressures.


    This page titled 5: Phase Diagrams IV is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Michael Adewumi (John A. Dutton: e-Education Institute) via source content that was edited to the style and standards of the LibreTexts platform.