Understanding Specific Enthalpy — Lesson 5

This lesson covers the concept of specific enthalpy in moist air and its applications in psychrometry. It explains how specific enthalpy is defined and how it can be approximated using the calorically perfect assumption. The lesson also discusses how specific enthalpy appears in psychometric applications and how it is used in energy equations. It introduces new terms used in psychometry, such as the partial pressure of water vapor, relative humidity, and the specific volume of dry air. The lesson concludes by explaining how the psychometric chart simplifies calculations in real-life applications. For instance, it illustrates how lines of constant wet bulb temperature almost coincide with lines of constant mixture specific enthalpy in the psychometric chart.

Video Highlights

00:05 - Introduction to moist air and specific enthalpy
05:09 - Introduction of new terms in psychometry
08:20 - Explanation of wet bulb temperature
09:44 - Introduction to the psychometric chart
20:56 - Explanation of how the psychometric chart simplifies calculations

Key Takeaways

- Specific enthalpy for moist air can be defined and approximated using the calorically perfect assumption.
- In psychrometric applications, specific enthalpy is often defined on a per kg dry air basis.
- The psychrometric chart, which is based on two independent properties, temperature and omega, simplifies calculations in real-life applications.
- The chart plots lines of constant values for various quantities such as partial pressure of water vapor, relative humidity, and specific volume of dry air.