Pipes water flow, pressure recovery

The reason the orifice flanges are kept close to the orifice plate is that when the liquid velocity decreases, downstream of the orifice plate, the pressure of the liquid goes partly back up. Figure 6.8 illustrates this point. It is called pressure recovery. Whenever the velocity of a flowing fluid (vapor or liquid) decreases, its pressure goes partly back up. An extreme example of this is water hammer. The reason the pressure at the end of the pipe in Fig. 6.8 is lower than at the inlet to the pipe is due to frictional losses. 

Figure 6.8 Pressure recovery for water flow in pipe.

Water is flowing in a pipe at a velocity of 8 m/s. Calculate the pressure increase and the increase in internal energy per unit mass for the following ways of bringing it to rest (a) a completely Mctionless diffuser with infinitely large. <42, (b) a diffuser which has 90 percent of the pressure recovery of a frictionless diffuser, with infinitely large A, and (c) a sudden expansion. 

---