 Welcome back to Mechanical AI, did you know that nearly 90% of all electricity generated in the world is by using steam as the working fluid? This makes us wonder, what are the properties of steam? Before we jump in, check out the previous part of this series to learn about what irreversibility is. Now, in a kilogram liquid vapor mixture, if XKG is the mass of vapor and 1-XKG is the mass of liquid, then X is known as a quantity or dryness fraction of the liquid vapor mixture. Mathematically speaking, dryness fraction X equals mass of vapor upon the sum of mass of vapor and the mass of liquid. enthalpy is a measurement of energy. It is equal to the internal energy of the system plus the product of the pressure and volume. More technically, it includes the internal energy, which is the energy required to create a system and the amount of energy required to make room for it by displacing its environment and establishing its volume and pressure. It is denoted by the letter H. In common use, however, only the change in enthalpy is discussed. The internal energy of a system is the energy contained within the system, excluding the kinetic energy of motion of the system as a whole and the potential energy of the system as a whole due to external force fields. It is denoted by the letter U. Hence, we learned about what dryness fraction of steam is, then moved on to learn about what enthalpy is and finally saw what internal energy is. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also, thanks a lot for those constructive comments. You helped the channel grow. So, here are the top mechanical years of our last videos. In the next episode of MechanicalEI, find out what is a mollier chart.