Engineering Thermodynamics Notes

Module Introduction

• Module Title: Engineering Thermodynamics (H3052)
• Instructor: Dr. Vasudevan Kanjirakkad
• Structure: 3 lectures/weeks (1-hr + 2-hr), workshops (weeks 2-11), lab session (week 3)

Assessment

1. Examination (UEX-in person): 70%
   • Duration: 2 hrs, answer 3 out of 4 questions
2. Coursework: 30%
   • 1 lab report, due 5 pm, Friday, Week 5

Resources

1. Online textbook (library)
2. Lecture slides (available on Canvas)
3. Recorded lecture videos (available post-lecture)
4. Workshop problems (weeks 2-4 & 6-11)

Module Contents

1. Introduction & Zeroth Law of Thermodynamics
2. Energy, Heat & Work: 1st Law of Thermodynamics
3. Pure Substances: Properties, Equations & Diagrams
4. Analysis of Closed Systems
5. Analysis of Control Volumes
6. 2nd Law; Thermodynamic Applications
7. Entropy and Reversibility
8. Gas Cycles
9. Liquid-Vapour Combined Cycles
10. Refrigeration

Introduction to Thermodynamics

• Definition: Thermodynamics is the study of heat, work, and the properties of matter.
• Key Terms:
  • Energy: Potential to do work (historically defined by Aristotle as ‘activity’).
  • Laws of Thermodynamics:
  • Zeroth Law: Establishes a basis for temperature and thermal equilibrium.
  • 1st Law: Conservation of energy (energy cannot be created or destroyed, only transformed).
  • 2nd Law: Addresses the quality of energy and entropy.

Working Definitions

• Engineers' Approach to Thermodynamics:
  • Focus on macroscopic properties and processes,
  • Use of properties like pressure, volume, temperature, and energy transformations.

Important Concepts in Thermodynamics

• Dimensions and Units:
  • Seven fundamental dimensions (length, mass, time, temperature, electric current, light intensity, amount of matter).
  • Various properties (pressure, energy) are derived from these.
• Definitions of Pressure: Normal force per unit area, often measured in Pa.

States and Properties

• System: Collection of matter with fixed identity for thermodynamic analysis.
• Closed System: No mass flow, but energy can be transferred (work or heat).
• Open System/Control Volume: Mass and energy can cross the boundaries.
• Extensive vs. Intensive Properties:
  • Extensive: Dependent on the amount of substance (e.g., volume, mass).
  • Intensive: Independent of the amount (e.g., temperature, density).
• Specific Properties: Per unit mass (e.g., specific volume).

Processes and Cycles

• Quasi-static Process: A process that happens slowly enough to maintain equilibrium.
• Cyclic Process: Returns to the original state.
• Steady State: No change in properties over time.

Energy Transfer Mechanisms

• Heat Transfer: Involves energy transfer due to temperature difference.
• Work Transfer: Mechanical energy transfer that results from a force moving through a distance.

Laws of Thermodynamics

• 1st Law: Energy conservation principle; states that the total energy of an isolated system is constant.
• 2nd Law: States that the total entropy (degree of disorder) can never decrease over time for an isolated system. This law explains the direction of natural processes and has various formulations, including the Kelvin-Planck statement and Clausius statement.

Coefficients of Performance (COP)

• COP: Measure of refrigerator or heat pump efficiency, defined as the ratio of useful heat removed or added to the work input.
• COP for Refrigerators:
  $COP<em>R = \frac{Q</em>L}{W_{net}}$
• COP for Heat Pumps:
  $COP<em>{HP} = \frac{Q</em>H}{W_{net}}$

Entropy

• Entropy (S) indicates the degree of disorder and randomness of a system.
  • Clausius Inequality:
    $dS \geq \frac{\delta Q}{T}$
  • Entropy is a state function and is always increasing in irreversible processes.

Carnot Cycle

• Idealized thermodynamic cycle that provides maximum efficiency.
• Efficiency Equation:
  $\eta<em>{Carnot} = 1 - \frac{T</em>L}{T_H}$

Rankine Cycle

• Practical cycle for steam power generation.
• Involves isentropic processes, heat addition, and rejection processes.

Otto & Diesel Cycles

• Idealized cycles for internal combustion engines, highlighting differences in the ignition process (spark vs. compression ignition).

Conclusion

• Thermodynamics laws and principles govern energy transformations in engineering applications. Understanding these principles is crucial for optimizing systems in practical applications such as engines, refrigerators, and turbines.

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Note

• Ensure to comprehend each section of the course material, practice problem sets, and refer to the recommended textbooks for deeper understanding.