Thermodynamics Lecture Notes

Definition of Thermodynamics

• Science of energy transfer and its effects on physical properties of substances.
• Based on common observations formulated into laws.
• Applications found in various fields including:
  • Power plants
  • Internal combustion engines
  • Refrigerators
  • Air conditioners
  • Fuel cells
• Utilizes heat for useful work and vice-versa.

Thermodynamic Systems

• Definition: A region of space focused on, separated from surroundings by a boundary.
• Types of Systems:
  1. Closed System: Energy transfer only.
  2. Open System: Both energy and mass transfer.
  3. Isolated System: No transfer occurs.
• Most systems analyzed are open systems.

Control Volume and Control Surface

• Focus on a specific volume within an open system.
• The surface bounding this volume is called the control surface.

Properties of a System

• Characteristics describing the system's physical condition (e.g., volume, temperature, pressure).
• When properties have definite values, the system is said to exist in a particular state.
• Change of State: Any operation where one or more properties change.
• When the path of change is specified, it is termed a Process (e.g., constant pressure process).

Cycles

• Defined as a series of state changes where the final state equals the initial state.

Matter and Thermodynamic Equilibrium

• Matter is composed of molecules and atoms, but often described continuously for macroscopic behavior.
• Thermodynamic Equilibrium: Exists when no change in macroscopic properties is observed.

Types of Equilibrium

1. Mechanical Equilibrium: Absence of unbalanced forces.
2. Chemical Equilibrium: No chemical reactions or matter transfer.
3. Thermal Equilibrium: No spontaneous property change when separated from surroundings.

Zeroth Law of Thermodynamics

• If body A is in thermal equilibrium with body B and C, then B and C are in thermal equilibrium with each other.
• Basis for temperature measurement, measured with thermometers.

Heat and Work Interaction

• Closed systems interact with surroundings via:
  • Work Transfer
  • Heat Transfer
• Heat and work are path functions and cannot be stored.

First Law of Thermodynamics

• Law of conservation of energy in thermodynamic terms.
• Forms:
  • For closed systems undergoing a cycle: Cyclic integral of work done is proportional to cyclic integral of heat transferred.
  • For closed systems undergoing a change of state: Net energy transfer is stored as internal energy, difference between work done and heat rejected.
• Major application: Analyzing mass flow across open systems with a steady flow energy equation.

Conclusion

• Quick revision on thermodynamics covered.

Questions

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