Explanation:

Fanno flow is a type of compressible flow in which the fluid flows through a duct with frictional effects. The flow is considered to be adiabatic, that is, there is no heat transfer between the fluid and the duct walls. The Fanno flow is characterized by the Mach number, the duct length, and the friction factor.

The prime parameter causing change of state in a Fanno flow is friction. Friction is the resistance that occurs when one surface moves over another. In the case of a Fanno flow, friction occurs between the fluid and the duct walls. This friction causes energy loss and a decrease in the total pressure of the fluid. The decrease in pressure leads to a change in the state of the fluid.

The following points explain how friction causes a change in state in a Fanno flow:

1. Energy loss: The friction between the fluid and the duct walls causes energy loss. This energy loss is in the form of heat, which is dissipated into the surroundings.

2. Decrease in pressure: The energy loss leads to a decrease in the total pressure of the fluid. This decrease in pressure causes a change in the state of the fluid.

3. Increase in temperature: As the fluid loses energy, its temperature increases. This increase in temperature causes a change in the state of the fluid.

4. Compression: The decrease in pressure and the increase in temperature cause the fluid to become compressed. This compression also causes a change in the state of the fluid.

Conclusion:

In conclusion, the prime parameter causing change of state in a Fanno flow is friction. Friction causes energy loss, which leads to a decrease in pressure and an increase in temperature. This change in state is caused by compression, which is a result of the decrease in pressure and the increase in temperature.