In the diagram, the Fanno line reaches maximum entropy at H = 0.833 and the flow is choked. According to the Second law of thermodynamics, entropy must always increase for Fanno flow.
In the diagram, the Fanno line reaches its peak level of randomness at H = 0.833, and the flow is at a critical juncture. In accordance with the Second law of thermodynamics, randomness must always increase for Fanno flow.