Thermodynamic Availability, What is?
Channel: MechanicaLEi
Date: 13/12/2017

Welcome back MechanicalEI, Out of all the energy that goes into a system only available energy or exergy is the one that does the actual work. This makes us wonder, What is availability? Before we jump in check out the previous part of this series to learn about what expansivity and compressibility is?. Now, The availability or the exergy of the system is the maximum work that can be extracted from it until it reaches the state of thermodynamic equilibrium with it's surroundings. This equilibrium state where all the spontaneous processes end, is called the dead state of the system. The minimum energy that has to be rejected by the second law is called the unavailability of the system. Exergy depends both on the system and it's surroundings. It is discussed under two groups: First, is the exergy of heat input in a cycle. From energy balance, we can understand that the net input in a cycle is the sum of available energy and unavailable energy and eta being the efficiency of the cycle, we get available energy to be equal to the product of efficiency eta and heat input Q. Second is the concept of availability in a steady flow process, which is given by the difference between the exergy steady state function psi and dead state steady state function psi not of the system. The exergy function is given as the sum of Keenan function denoted by B, kinetic energy denoted by m v squared upon 2 and potential energy denoted by m g z. Hence, we saw what Available energy is, then applied it to a cycle and then to a steady flow process .

Attributions:

Doh De Oh by Kevin MacLeod is licensed under a Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/)
Source: http://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100255
Artist: http://incompetech.com/

Subtle Library by Fabian Measures (http://freemusicarchive.org/music/Fabian_Measures/) is licensed under a Creative Commons Attribution licence ( https://creativecommons.org/licenses/by/4.0/)
Source: http://freemusicarchive.org/music/Fabian_Measures/Emotion_Music/Subtle_Library