A liquid flows from pipe A to pipe B as shown in Figure 4 Th

A liquid flows from pipe A to pipe B as shown in Figure 4. The diameter of pipe may not be the same as that of pipe B. The energy grade lines and the hydrauli grade lines for steady flow in the system are plotted in Figure 4. (i) What could be in the enclosed \"black box\"? Pick the best answer: a) a pump (b) a reservoir (c) a turbine (d) an abrupt expansion joint (ii) What can you say about the pipes? Pick your choice: (a) The internal diameters of both pipes are the same. (b) Pipe A is larger than pipe B. (c) Pipe B is larger than pipe A. (d) We cannot tell from the given information.

Solution

(i) (c) A Turbine:

That\'s because, in order to have such a variation in both (the Energy Grade Line (EGL) and the Hydraulic Grade Line (HGL)), there must be an exchange of energy between the fluid and the Black Box, which doesn\'t happen with a reservoir; a pump gives energy to the fluid, so, in such case, the lines at the Black Box of the EGL and the HGL must increase.

It could also be an abrupt expansion joint because it implies losses too. To know defenitly which one it is, you must know the magnitude order of the loss at the Black Box. A turbine makes a much more higher loss because its purpose is to extract energy.

(ii) (c) Pipe B is larger than pipe A:

If the diameters and lengths of pipe A and B were the same, the amount of loss would be equal before and after the Black Box.

If pipe A was larger than B and the diameters were the same, the losses in pipe A would be higher.

While if pipe B was larger than pipe A, and we assume that they have the same diameter and the slope of the image is not at scale, then the losses in pipe B would be higher, which is what we find in the lines.