Applications of Second Law Efficiency — Lesson 5

This lesson covers the application of the second law of thermodynamics to various steady flow processes. It provides a detailed explanation of how to calculate the second law efficiency of different devices such as a compressor, a steam turbine, a feed water heater, and a heat engine. The lesson also discusses the concept of exergy and how it can be used to evaluate the performance of these devices. For instance, it explains how to calculate the rate of exergy destruction and the second law efficiency of a compressor. The lesson also provides examples of how to apply these concepts to real-world scenarios, such as determining the mass flow rate of steam required in a feed water heater.

Video Highlights

00:19 - First example involving air compression in an 8-kilowatt compressor and determining the second law efficiency of the compressor
03:41 - Second example involving a steam turbine and determining the actual power output, maximum possible power output, and the second law efficiency
06:28 - Third example involving a feed water heater or mixing chamber and determining the required mass flow rate of steam
15:55 - Cyclic process in a direct heat engine and developing an expression for the second law efficiency of the heat engine

Key Takeaways

- Steady flow applications are crucial in understanding the workings of various devices like compressors, turbines, and heaters.
- The second law efficiency of a device can be determined by evaluating the rate of exergy destruction and the actual power output.
- Lost work is an important concept that affects the actual work done by a device.
- Thermodynamic cycles like the Rankine cycle, air standard cycle, and vapor compression refrigeration cycle provide insights into the performance of heat engines.