Chapter 12.1, Problem 1P

To determine

Whether the device is a pump or a turbine.

Answer to Problem 1P

The device is a pump.

Explanation of Solution

Pump: It is defined as a machine or device which is used to force a fluid to move in a given direction. In the case of pump, the work is done on the fluid.

Turbine: It is defined as a mechanical machine which is used to produce continuous power. In the case of turbine, the work is done by the fluid.

Draw the velocity diagram for the given figure.

Figure-(1)

Write the expression for the linear velocity of the blade at inlet.

    $U_1=\omega r_1$                                                      (I)

Here, the radius of the blade at inlet is $r_1$ and the angular velocity is $\omega$.

Write the expression for the linear velocity of the blade at exit.

    $U_2=\omega r_2$                                                     (II)

Here, the radius of the blade at outlet is $r_2$.

Since, the angular velocity is remains constant at inlet and outlet, only the radius is different. The outlet radius is greater than the inlet radius. Hence, the exit velocity is also greater than the inlet velocity. Due to this the direction of absolute velocity is changed from $V_1$ to $V_2$ passing through blade from inlet to exit.

Therefore, the work is done on the fluid by the device hence the device is a pump.

Conclusion:

Thus, the device is a pump.