Design of Pump Piping System for a Reservoir Tank

This exercise requires you to design a pump-piping system to keep a 80, 000 m’ capacity reservoir tank filled. The tank is to be filled daily with groundwater (at 10 °C) from an aquiter which is 100 m lower than the tank, using a pipe 2200 m long. Estimated daily water use is 100, 000 m'/day, and the filling time should not exceed 8 h per day. The piping system will contain 4 butterfly valves (loes coefficient A = 0.30 when fully open), 10 elbows of various angles (loss coefficient K 0.4) and plastic pipe (assumed smooth) of a size to be selected in the design. The pump can be manufactured to be of any convenient size (measured in terms of the impeller diameter D) and can run at speeds between N 600 and N  1800RPM. The head produced for various flow rates are tabulated below (table 1) in terms of the Joe coeQcieni Kg and the head coeQc*ent, defined as follows :

There are two parts to this exercise, each worth 10 marks : Part A :
1. Erom the information given in table 1. evaluate the head H for flow Q for a pump of diameter 1.2 m running at speed N = 800RPM, and plot this on a graph. Also plot the efficiency p on the same graph.
2. Write down an expression for the head loss in the piping system (including vertical head Az).
3. On the same graph as for part 1; use this to plot head losa H vs. Q for a pipe of 70 cm diameter.
4. Use your graphs to estimate the flow rate in the system and the power required to run the pump.

Part B :
The knowledge gained from part A should enable you to produce a spreadsheet model of the system. A spreadsheet can be used to automate the calculation of the pipe head loss for a given pipe diameter d (changing d changes the flow speed V, thus the Reynolds number, and thus the friction factor and head loss in the pipe). It can also be used to automate the calculation of the head Zf and flow Q for a pump of diameter D and speed N, and plot the two curves; the intersection point represents the operating point of the system. Having set up the spreadsheet, you can then adjust parameters such as d, D and N and see the eBect on the system. Finally, given theae parameters and the costs of various components (see table 2), you can calculate the cost of the whole system.

Use your spreadsheet to develop your own design for the system. The design should be economical, both in capital costs and operating expense. Please also consider the carbon footprint of your installation. Write a short report detailing and justifying your design choices 
(append printouts of your spreadsheets) this should include the final design, head loss and cost (installation and running cost).

Table 1 : Pump characteristics
Kq         0.32 x 10 3  0.64 x 10 '  0.96 x 10 3  1.28 x 10 3  1.60 x 10*’
K   4.19 x 10   4.33 x 10   4.42 x 10   4.47 x 10   4.37 x 10   4.33 x 10*
13       25       35              48 1.92 x 10
4.19 x 10- 51 3.83xl0-
2.33 x 10-45
2.23 x 10—  2.55 x 10—  2.8T x 10—  3.19 x 10—  3.51 x 10—
4.03 x 10—  3.86 x 10—  3.57 x 10-  3.26 x 10—  2.79 x I0—
53            55      53      50

Thble 2 : Estimated costa
Item        Cost
Pump and motor  J4000 plus £ 1500 per cm of impeller size Pump speed   Between 600 and 1800RPM
Valves      Z‘500 plus £120 per cm of pipe size
Elbows      f‘100 plus £50 per cm of pipe size
Pipes       £2.20 per cm of diameter per m of length Electricity cost  8p per kilowatt-hour

TabIe 3 : Carbon footprint
Item        Details
Steel pipe     40 cm diameter
120 cm diameter

Concrete pipe   20 cm diameter
200 em diameter

Power generation Coal
Gas
Nuclear

Indicative carbon footprints are given for steel and concrete pipe (interpolate between these for intermediate values). Note that steel pipe may be regarded as smooth; concrete pipe is rough inside and will give a friction factor / = 0.008.