Exercise 4.II Head loss and cavitation in a hydraulic circuit

Exercise 4.II Head loss and cavitation in a hydraulic circuit 

Write the head loss versus flow rate relationship for the whole circuit. Head variations other than the regular head loss in the pipe, the singular head loss at the valve, and the head increase produced by the pump will be neglected. 

In commercially available pipes, the dimension a of the section equals 10 cm, 20 cm, 30 cm, 40 cm, 50 cm, 60 cm, 70 cm, 80 cm, 90 cm, 1 m, etc. State the smallest value of a that allows for a flow rate greater than 1001/s. For this evaluation, the head loss associated with the valve can be omitted. Why is that For the different pipe diameters considered, comment upon the obtained variations in the regular head loss coefficient. 

It is assumed from now on that a = 0.3 m. Estimate the angle by which the valve should open for a flow rate 0 = 70 1/s. A first stage will consist in evaluating the head variation across the pmnp, the pipe, and the valve, and comparing the values obtained. 

For the two opening angles d= 70° and 5= 15°, determine the flow rate and velocity in the pipe. Calculate the pressure variation between the inlet and the outlet of the valve, and between the inlet and the contracted section. Sketch the pressure changes inside the valve. Is it possible to observe cavitation in the contracted section without cavitation occurring at the valve outlet  

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