Understanding Exergy Balance — Lesson 3

This lesson covers the concept of exergy balance, a fundamental principle in thermodynamics. It delves into the application of exergy balance in various systems and control volumes, using practical examples to illustrate the concept. The lesson begins with a tutorial on exergy balance in systems, focusing on a problem involving an iron block and water in an insulated tank. It then transitions to control volumes, discussing a problem involving a frictionless piston-cylinder device containing a mixture of gases. The lesson concludes with a detailed explanation of a problem involving air compression. The lesson provides a comprehensive understanding of how to calculate mass, temperature, entropy, and exergy changes in different scenarios.

Video Highlights

00:21 - Explanation of problem: An iron block and an insulator tank
08:10 - Introduction to problem: A piston cylinder device containing a mixture of gases
22:02 - Introduction to problem: Air compression

Key Takeaways

- Exergy balance problems involve understanding the system, applying the first and second laws of thermodynamics, and calculating the required parameters.
- In an exergy balance problem, it's crucial to consider the specific heat, temperature, and mass of the components involved.
- For systems like a frictionless leak-proof piston cylinder device, the molecular weight of the mixture, specific gas constant, and specific heat constant volume are important parameters.
- In problems involving a compressor, the power input, changes in kinetic and potential energies, and the rate of change in exergy are key considerations.
- The second law efficiency of a work absorbing device like a compressor can be calculated using the reversible work input and the actual work input.