300725 Construction Technology Services For Assessment Answers
Answer:
Pump sizing. `
In the process of sizing a pump, the following points must be given specific consideration;
Flow rate
This is normally obtained by the process through which the pump is installed. The mass and energy balance of the process ultimately define the process.
Total differential head
Total differential head=Frictional head losses differences of static head.
Static head difference
It is the difference in the head between the suction static head and discharge static head; static head difference=suction static head+discharge static head.
Static head
This is normally considered as the sum of the gas pressure at the liquid surface in the vessel of discharge(Monteith et al 2012).
Frictional head losses
Frictional head losses consist of frictional losses in the piping system of the suction part and also in the discharge piping system.
This is normally calculated using the formula below;
Frictional head losses= (FL/D+Kfittings) u2/2g where;
F=friction factor
L= pipe length
D=diameter of pipe
K=fitting factor
U=velocity of the liquid
g=acceleration due to gravity.
Pump power
Pump power=flow rate*density of the liquid*acceleration due to gravity*efficiency of the pump*total differential.
Assuming that the amount of water to be pumped is 30000kg/hr. from one tank to another, water temperature is at 20c,density of 998kg/m3,vapour pressure of 0.023 bar and a viscosity of 1cp.The efficiency of the pump is taken to be 70%( Sun, Deng and Yan 2014).
Details of the pump
Barometric pressure=1.013bar
Margin available=0m
Efficiency of the pump=70%
Properties of the fluid
Type of fluid=water
Phase of the fluid=liquid
Flow rate=30000kg/hr.
Liquid density=998kg/m3
Water viscosity=1cP
Vapor pressure=0.023bar
Gas pressure vessels
Suction gas pressure=1bar
Gas pressure of discharge=2bar
Static heads
Static head at suction=2m
Static head at discharge=120m
Pipelines
Nominal diameter pipe=4(suction line) and 3(discharge line).
Pipe schedule=40(for both suction line and discharge line)
Length of the pipe=150m (discharge line) and 10m for suction line.
Absolute roughness=0.046m for both suction and discharge line.
Fittings
90 degrees LR bends=1(suction line) and 4(discharge line),Pipe entrances=1(suction line) and 0 for discharge line.
Gate valves=1(discharge) and also 1(suction line),Swing check valve=1(suction line).
Fitting factor=1 for both suction and discharge line (Nikaido and Pagès 2012).
|
Discharge line |
Line of suction | |||
|
Relative roughness |
0.00044 |
0.00058 | ||
|
Area of flow |
0.00820 |
0.00476 | ||
|
Velocity Reynolds number |
1.03 103757 |
1.76 136173 | ||
|
Regime of flow |
Turbulent |
Turbulent | ||
|
Factor of friction |
0.0211 |
0.0202 | ||
|
Velocity loss factor |
1.967 |
37.43 | ||
|
Total velocity head loss |
`1.725 |
2.024 | ||
|
Frictional pressure loss |
0.03 |
0.61 | ||
|
Frictional head loss= |
0.18 |
6.35 | ||
Suction pressure of the pump=2.18bar
Sanction head=22.36m
Discharge pressure of the pump=15.34bar
Discharge head pump=156.67m
Pump overall differential pressure (mH) =13.18bar
Differential head=134.85m
Pump power=15.56Kw
Pump flow rate (Q) =31m3/hr.
PART C
Calculation of flow rate, it may be assumed that the apartment has 56 units;
18 floors, residual pressure of 30psi, supply pressure by council is equal to 30psi, two full bath taps and dish washer machine at each unit.
Bathtubs: 4*112 tubs=448fu
Sink: 1*112=112fu
Toilet: 2.4fixture*112=280fu
Kitchen sink: 1.5*56=84fu
Clothes washer:1.5*56washer=84fu,the total fixture units sum 1092 and this gives flow rate of 220gpm.The flow rate=220gpm(Yannopoulos et al 2015).
Calculation of head
In this calculation, the following elements must be considered; friction head, residual head pressure, static head and finally inlet head pressure.
Static head= (18*12 feet per floor) =216 feet but 1psi=2.31 feet of head. This follows that total pressure is calculated as
216feet/2.30=93.49
Approximately 94 psi.
Calculation of friction loss
This is affected by pipe diameter, distance and gpm
=216 feet+100feet
=316feet
Taking into account elbows and other fittings, the loss factor is 0.5
=316 feet*0.05
=16feet,friction loss increases with increase in gpm.
Total equivalent pipe length =316feet +16feet
=332feet
(332feet*6feet)/100feet=20feet.
HF=20feet/2.31
=8.7Psi
Residual pressure head,HR=30psi.
The required discharge pressure=94psi+9psi+30psi
mH =133psi
REFERENCES
Nikaido, H. and Pagès, J.M., 2012. Broad-specificity efflux pumps and their role in multidrug resistance of Gram-negative bacteria. FEMS microbiology reviews, 36(2), pp.340-363.
Monteith, G.R., Davis, F.M. and Roberts-Thomson, S.J., 2012. Calcium channels and pumps in cancer: changes and consequences. Journal of Biological Chemistry, 287(38), pp.31666-31673.
Sun, J., Deng, Z. and Yan, A., 2014. Bacterial multidrug efflux pumps: mechanisms, physiology and pharmacological exploitations. Biochemical and biophysical research communications, 453(2), pp.254-267.
Yannopoulos, S.I., Lyberatos, G., Theodossiou, N., Li, W., Valipour, M., Tamburrino, A. and Angelakis, A.N., 2015. Evolution of water lifting devices (pumps) over the centuries worldwide. Water, 7(9), pp.5031-5060.
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