Question

I'm looking for a excercise of these topic. If any one have one of these topic example please comment

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Chapter 6

1) Pump Specific Speed and Similarity

2) Cavitation in Water Pump

3) Selection of Pump

4) Pump in Parallel or in Series

5) Power of Reaction Turbine, relate to equation 6.36 to 6.39

6) Turbine Laws and Specific Speed

7) Cavitation in Turbine

8) Selection of Turbine

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Chapter 7

1) Surface Drainage

2) Highway Drainage

3) Subsurface Drainage

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Answer 1

SELECTION OF PUMP

• Main principles of pumps selection
  • Process and design requirements
  • Nature of pumped medium
  • Key design parameters
  • Fields of pumps application (selection) according to the created head
  • Fields of pumps application (selection) according to the capacity
• Key design parameters of pumps (performance capacity, head, power)
• Capacity calculations for different types of pumps. Formulas
  • Piston pumps
  • Gear pumps
  • Screw pumps
  • Centrifugal pumps
• Calculation of pump head
• Calculation of pump power consumption
• Extreme suction head (for centrifugal pump)
• Examples of problems and solutions for calculation and selection of pumps
  • calculation of plunger pump volumetric efficiency
  • calculation of required power for two-piston pump electric motor
  • calculation of the value of three-piston pump head loss
  • calculation of screw pump volumetric efficiency
  • calculation of centrifugal pump head, flow rate and useful capacity
  • calculation of expediency of using centrifugal pump for water pumping
  • calculation of wheel (gear) pump delivery coefficient
  • determination of whether this particular pump meets requirements for starting torque
  • calculation of centrifugal pump useful capacity
  • calculation of extreme increase of pump flow rate

  • The following is a pump sizing problem to illustrate the calculations in this article. You are told to purchase a pump for your manufacturing facility that will carry water to the top of a tower at your facility. The pump is a centrifugal pump that will need to pump 800 gal/min when in normal operation. Assume BHP is 32 and 16 horsepower for the 3,500-rpm and 2,850-rpm pumps, respectively, for all pump choices in the composite curve. The pump operates for 8,000 h/yr. Assume all of the pumps are viable for your required flowrate. The suction-side pipe and discharge-side pipe diameters are 4 and 3 in., respectively. The suction tank elevation (S) is 12 ft, and the discharge tank elevation (D) is 150 ft. Pressure on the suction side is atmospheric pressure (1 atm = 14.696 psi) and the pressure on the discharge side is 1.1 atm. Assume that both hd,f and hs,f are roughly 10 ft.

    Based on a five-year life, the objective of the problem is to calculate the lifecycle cost to operate each pump (that is, the costs of installation, maintenance and electricity, which is $0.18/kW), and to choose the pump with the lowest lifecycle cost (depreciation is assumed to be negligible for this example). The pump curves in Figure 3 illustrate the following pump options to choose.

    Option 1: 4 × 3 – 13 3,500 rpm
    Installed cost of pump and motor: $20,000 for 3,500 rpm
    Maintenance cost: 10% of installed cost per year
    Motor efficiency: 65% (assumed)

    Option 2: 4 × 3 – 13 2,850 rpm
    Installed cost of pump and motor: $40,000 for 2,850 rpm
    Maintenance cost: 8% of installed cost per year
    Motor efficiency: 80% (assumed)

    Option 3: 4 × 3 – 10 3,500 rpm
    Installed cost of pump and motor: $10,000 for 3,500 rpm
    Maintenance cost: 10% of installed cost per year
    Motor efficiency: 65% (assumed)

    Option 4: 4 × 3 – 10 2,850 rpm
    Installed cost of pump and motor: $20,000 for 2,850 rpm
    Maintenance Cost: 8% of installed cost per year
    Motor Efficiency: 80% (assumed)

    Solution:
    Convert volumetric flow to velocity:

    

    

    

    

    

SUBSURFACE DRAINAGE

In flat lands, subsurface drainage systems are installed to control the general groundwater level in order to achieve water table levels and salt balances favourable for crop growth. Subsurface drainage may be achieved by means of a system of parallel drains or by pumping water from wells. The first method is usually known as horizontal subsurface drainage although the drains are generally laid with some slope. The second is called vertical drainage. A system of parallel drains sometimes consists of deep open trenches. However, more often, the field drains are buried perforated pipes and, in some cases, subsurface collector drains for further transport of the drain effluent to open water are also buried pipes. The drainage water is further conveyed through the main drains towards the drainage outlet. Less common are vertical drainage systems consisting of pumped wells that penetrate into an underlying aquifer. In sloping lands, the aim of subsurface drainage is usually to intercept seepage flows from higher places where this is easier than correcting the excess water problem at the places where waterlogging occurs from shallow seepage

Type of drainage system..........Engineering factor

Surface drainage system...........Length and slope of the fields, dimensions of beds,terraces and open drains

Subsurface drainage system......Depth, spacing, and dimensions of open or pipe drains

EXAMPLE: If a road culvert is to last 25 years with a 40% chance of failure during the design life, it should be designed for a 49-year peak flow event (i.e., 49-year recurrence interval).

When streamflow records are not available, peak discharge can be estimated by the "rational" method or formula and is recommended for use on channels draining less than 80 hectares (200 acres):

Q = 0.278 C i A

where:	Q = peak discharge, (m3/s)
	i = rainfall intensity (mm/hr) for a critical time period
	A = drainage area (km²).

(In English units the formula is expressed as:

Q = C i A

where:	Q = peak discharge (ft3/s)
	i = rainfall intensity (in/hr) for a critical time period, tc
	A = drainage area (acres).

The runoff coefficient, C, expresses the ratio of rate of runoff to rate of rainfall and is shown below in Table 26. The variable tc is the time of concentration of the watershed (hours).

Type of Surface	Factor C
Sandy soil, flat, 2%	0.05-0.10
Sandy soil, average, 2-7%	0.10-0.15
Sandy soil, steep, 7	0.15-0.20
Heavy soil, flat, 2%	0.13-0.22
Heavy soil, average, 2-7%	0.18-0.22
Heavy soil, steep, 7%	0.25-0.35
Asphaltic pavements	0.80-0.95
Concrete pavements	0.70-0.95
Gravel or macadam pavements	0.35-0.70

Numerous assumptions are necessary for use of the rational formula: (1) the rate of runoff must equal the rate of supply (rainfall excess) if train is greater than or equal to tc; (2) the maximum discharge occurs when the entire area is contributing runoff simultaneously; (3) at equilibrium, the duration of rainfall at intensity I is t = tc; (4) rainfall is uniformly distributed over the basin; (5) recurrence interval of Q is the same as the frequency of occurrence of rainfall intensity I; (6) the runoff coefficient is constant between storms and during a given storm and is determined solely by basin surface conditions. The fact that climate and watershed response are variable and dynamic explain much of the error associated with the use of this method.

Manning's formula is perhaps the most widely used empirical equation for estimating discharge since it relies solely on channel characteristics that are easily measured. Manning's formula is:

Q = n-1 A R2/3 S1/2

where:	Q = discharge (m3/s)
	A = cross sectional area of the stream (m²)
	R = hydraulic radius (m), (area/wetted perimeter of the channel)
	S = slope of the water surface
	n = roughness coefficient of the channel.

(In English units, Manning's equation is:

Q = 1.486 n-1 A R2/3 S1/2

where	Q = discharge (cfs)
	A = cross sectional area of the stream (ft2)
	R = hydraulic radius (ft)
	S = slope of the water surface
	n = roughness coefficient of the channel.)

Values for Manning's roughness coefficient are presented in Table 27.

Natural stream channels	n
1. Fairly regular section:
Some grass and weeds, little or no brush	0.030 - 0.035
Dense growth of weeds, depth of flow materially greater than weed height	0.035 - 0.050
Some weeds, light brush on banks	0.050 - 0.070
Some weeds, heavy brush on banks	0.060 - 0.080
Some weeds, dense willows on banks	0.010 - 0.020
For trees within channel, with branches submerged at high stage, increase above values by	0.010 - 0.020
2. Irregular sections, with pools, slight channel meander; increase values given above by	0.010 - 0.020
3. Mountain streams, no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stage:
Bottom of gravel, cobbles, and few boulders	0.040 - 0.050
Bottom of cobbles with large boulders	0.050 - 0.070

Area and wetted perimeter are determined in the field by observing high water marks on the adjacent stream banks (Figure 61). Look in the stream bed for scour effect and soil discoloration. Scour and soil erosion found outside the stream channel on the floodplains may be caused by the 10-year peak flood. Examining tree trunks and brush in the channel and floodplain may reveal small floatable debris hung up in the vegetation. Log jams are also a good indication of flood marks because their age can be estimated and old, high log jams will show the high watermark on the logs. The difficulty in associating high water marks with flow events of a specified recurrence interval makes values obtained by this method subject to gross inaccuracy. If the 10-year flood can be determined, flow levels for events with a higher recurrence interval can be determined roughly from Table 28.

Peak flow return period (years)	Factor of flood intensity (10-year peak flow = 1.00)
10	1.00
25	1.25
50	1.50
100	1.80

A key assumption in the use of Manning's equation is that uniform steady flow exists. It is doubtful that high gradient forested streams ever exhibit this condition. (Campbell, et al., 1982) When sufficient hydrologic data is lacking, however, Manning's equation, together with observations of flow conditions in similar channels having flow and/or precipitation records, provide the best estimate of stream discharge for purposes of designing stream crossings. An example illustrating the use of Manning's equation to calculate peak discharge is as follows: