Second law of thermodynamics states that the total entropy of an isolated system or systems never decreases, because isolated systems always evolve toward thermodynamic equilibrium, the state with maximum entropy.
Isolated System: In physics, an isolated system is either a thermodynamic system which is completely enclosed by walls through which can pass neither matter nor energy, though they can move around inside it or a physical system so far removed from others that it does not interact with them, though it is subject to its gravity.
Entropy: In thermodynamics, entropy (S) is a measure of the number of specific ways in which a thermodynamic system may be arranged, commonly understood as a measure of disorder.
The Second Law of Thermodynamics is formulated by Sadi Carnot in 1824.
The second law of thermodynamics asserts that processes occur in a certain direction and
that the energy has quality as well as quantity. The first law places no restriction on the direction of a process, and satisfying the first law does not guarantee that the process will occur. Thus, we need another general principle (second law) to identify whether a process can occur or not.
A process can occur when and only when it satisfies both the first and the second laws of
thermodynamics. The second law also asserts that energy has a quality. Preserving the quality of energy is a major concern of engineers. In the above example, the energy stored in a hot container
(higher temperature) has higher quality (ability to work) in comparison with the energy
contained (at lower temperature) in the surroundings. The second law is also used in determining the theoretical limits for the performance of commonly used engineering systems, such as heat engines and refrigerators etc
Heat Engines:
Heat engines convert heat to work. There are several types of heat engines, but they are
characterized by the following:
1‐ They all receive heat from a high‐temperature source (oil furnace, nuclear reactor, etc.)
2‐ They convert part of this heat to work
3‐ They reject the remaining waste heat to a low‐temperature sink
4‐ They operate in a cycle.
characterized by the following:
1‐ They all receive heat from a high‐temperature source (oil furnace, nuclear reactor, etc.)
2‐ They convert part of this heat to work
3‐ They reject the remaining waste heat to a low‐temperature sink
4‐ They operate in a cycle.
