Thermodynamics Lecture Notes

Introduction to Thermodynamics

• Origin of the term:
  • Greek origin: therme (heat) and dynamis (force).
• Early Understanding: Focus on extracting power from heat.
• Scope: Broader, involving natural physical processes, energy conversion, rhythm in nature.

Natural Processes and Rhythm

• Examples of Natural Processes:
  • Water flows downhill, heat flows from hot to cold.
• Energy Conversion Constraints:
  • Mechanical to heat is possible; reverse isn’t (e.g., stopping moving body turns kinetic energy into heat).
  • Some processes are reversible with external changes (e.g., heating/cooling, gas expansion/compression).

Laws of Thermodynamics

First Law (Conservation of Energy)

• Energy cannot be created nor destroyed.
• Total energy remains constant (mass-energy equivalence aside).
• Examples:
  • Mechanical to electrical energy conversion can be near 100% efficient.
  • Heat to work cannot be 100% efficient.

Second Law (Directionality)

• Natural constraints and rhythms.
• Examples:
  • Heat flow can’t spontaneously reverse.
  • Internal energy changes in chemical reactions.

Importance and Practical Relevance

• Conservation of Energy: Awareness due to depletion of fossil fuels.
• Efficient Utilization: Alternative energy sources have limitations (e.g., solar, wind).
• Environmental Concerns: Need for clean energy processes.
• Guidance: Thermodynamics outlines efficient and feasible energy practices.

Definitions and Fundamental Concepts

Systems and Surroundings

• System: Quantity of matter with a boundary.
• Types of Systems: Control Mass and Control Volume.
  • Control Mass: Fixed mass, no mass transfer but energy transfer allowed.
  • Control Volume: Fixed volume, allows both mass and energy transfer.
• Isolated System: No interaction (mass or energy) with surroundings.

Thermodynamic Properties

• Types:
  • Extensive: Depend on system mass (e.g., volume, internal energy).
  • Intensive: Independent of system mass (e.g., pressure, temperature).
• State Variables: Describe the state of the system at equilibrium.

Equilibrium and States

• Thermodynamic Equilibrium: No changes in properties or processes within the system.
• Types: Thermal, mechanical, and chemical equilibrium.
• State Representation: Systems are represented by state points in thermodynamic diagrams.
• Gibbs Phase Rule: Determines degrees of freedom (f = c - φ + 2) for phases and components.
  • Single Component, Single Phase: Requires two independent properties to fix state.
  • Triple Point: Zero degrees of freedom.

Processes and Pathways

• Quasi-equilibrium Process: Gradual process ensuring intermediate states can be considered equilibrium states.
• Dead State: When system properties equal surroundings, no interaction occurs.

Course Outline

• Introduction and Basic Definitions: Systems, surroundings, properties, equilibrium.
• First Law of Thermodynamics: Cyclic and non-cyclic processes, internal energy, enthalpy.
• Second Law of Thermodynamics: Directional constraints, entropy, reversibility, Carnot cycle.
• Thermodynamic Property Relations: Maxwell’s equations, specific heats, Joule-Kelvin effect.
• Properties of Pure Substances and Mixtures: Phase equilibrium, steam tables, Clausius-Clapeyron equation.
• Thermodynamics of Reactive Systems: Energy conservation in reactions.
• Thermodynamic Cycles: Carnot, Stirling, Otto, Diesel, and Brayton cycles.
• Texts Recommended: Various foundational and authoritative books on thermodynamics, e.g., Sonntag, Borgnakke, Van Wylen.

Note: The detailed lecture will be a compilation from multiple recommended texts.