Assignment:
QUESTION 1.
i) A manometer using mercury shows a difference between the level of 0.11m when attached to the top of a tank containing liquid under pressure. Some liquid is added to the open end of the manometer to a depth of 1m and the difference between the levels of the mercury is now 0.01m. What is the density of the liquid added to the manometer?
ii) An unvented water system is being retro fitted into a building and some concern is expressed that not all the taps and joins in the plumbing system are capable of withstanding3 bar pressure. It was felt that all these taps and joints could withstand a pressure of 1 bar. What kind of measuring equipment would be used to check the mains pressure and in what area of the building would the pressure be taken?
QUESTION 2.
A dam of 85 m in length holding water to a depth of 45m in a reservoir. Calculate
(i) the position of the centre of pressure Assume density of water is 1000 KGm-3 and acceleration due to gravity is 9.81m3s-1
(ii) the total force acting on the dam.
(iii) If the wall of the dam is 60m above the base and the maximum force that is considered safe for the dam to withstand is 30MN, at what height must the spillway that sets the maximum depth be situated?
QUESTION 3.
i) The table given below gives the characteristics of a centrifugal pump running at a steady speed:
|
Discharge Q litres/s
|
0
|
10
|
20
|
30
|
40
|
50
|
60
|
70
|
|
Head Hm m
|
45.0
|
44.7
|
43.7
|
42.5
|
40.6
|
38.0
|
35.0
|
31.0
|
|
Efficiency
%
|
-
|
35
|
50
|
57
|
60
|
60
|
53
|
40
|
|
|
|
|
|
|
|
|
|
|
|
|
i) The table given below gives the characteristics of a centrifugal pump running at a steady speed:
Fresh water is pumped to a service reservoir through a 350mm diameter pipe 10km long. The static head is 20m. Determine the discharge in the through the pipe and the power requirement of the pump. (This will need you to plot the pump - characteristic, system characteristic and efficiency curves against flow rate (Q). You must also find the operating point> Assume the friction factor f = 0.0045 and take minor losses at ten times the velocity head.
ii) In the above problem, if the static head were 40m not 20m, and you had a second identical pump available, explain how would you have arranged these pumps to overcome this much greater head?
QUESTION 4
i) Outline the essential differences between a pump and a turbine especially in how efficiency is expressed.
ii) Outline the application of the three main types of turbine (radial, axial and reaction)