Enthalpy in Combustion Systems — Lesson 2

This lesson covers the application of the first law to combustion systems, focusing on steady flow situations. It delves into the concept of enthalpy, explaining how it is defined as specific enthalpy (u) plus pv, where u is the specific internal energy. The lesson also discusses how the specific internal energy for ideal gases is related to the modes of energy storage in molecules. It further explains how the energy stored in these modes is dependent only on the temperature of the gas. The lesson also introduces the concept of enthalpy of formation and how it is used in combustion calculations.

Video Highlights

01:07 - Explanation of the concept of enthalpy
06:19 - Explanation of the concept of enthalpy of formation
13:04 - Calculation of the enthalpy of formation of gaseous methane and acetylene
19:26 - Discussion on the first law analysis of combustion systems

Key Takeaways

- The first law of thermodynamics can be applied to combustion systems to understand the energy transformations that occur.
- Enthalpy is a crucial concept in thermodynamics, defined as the sum of the enthalpy of formation and sensible enthalpy.
- Energy storage modes in molecules include translation, rotation, and vibration, and these are dependent on the temperature of the gas.
- During combustion calculations, it's essential to account for the energy stored in chemical bonds as these bonds are broken and new ones are formed during chemical reactions.