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The application of Appropriate Technology

i. Glossary

Term Description Units
a Acceleration Metres/Second2
A Area Metres2
At Reservoir Supply Pipe Area Metres2
D,d Pipe Diameter Metres/inches
E Energy Joules
Ek Kinetic Energy Joules
Ep Potential Energy Joules
F Force Newtons
f Friction Factor
fA-n Frictional Head Loss in Tap Supply Pipe Metres
fh Frictional Head Loss Metres
fhl Frictional Head Loss in Larger Diameter Pipe Metres
fhn Frictional Head Loss in Pipe n Metres
fhs Frictional Head Loss in Smaller Diameter Pipe Metres
fp Frictional Loss (Pressure) Newtons/Metre2
ft-A Frictional Head Loss in Reservoir Supply Pipe Metres
g Gravitational Acceleration Metres/Second2
h Height Metres
H Desired Frictional Head Loss Metres
hA Height of Junction A Metres
HA Head at Point A Metres
hB Height of Junction B Metres
Hmax Maiximum Static Head Metres
hn Height of nth Tap Metres
Hn Residual Head at Tap n Metres
ht Reservoir Height Metres
I Electrical Current Amps
L Length Metres
Ln nth Tap Supply Pipe Length Metres
Lt Reservoir Supply Pipe Length Metres
M Mass Kilogrammes
n Number of Taps
NRE Reynolds Number
P Pressure Newtons/Metre2
PA Pressure at Junction A Newtons/Metre2
PB Pressure at Junction B Newtons/Metre2
Pk Kinetic Energy as a Pressure Newtons/Metre2
Pn Residual Pressure at nth tap Newtons/Metre2
Pp Pump Pressure Newtons/Metre2
Pp Potential Energy as a Pressure Newtons/Metre2
Pt Turbine Pressure Newtons/Metre2
Q,q Volumetric Flow Rate Metre3/Second
qA Volumetric Flow Rate at Junction A Metre3/Second
S Distance Metres
t Time Seconds
v Velocity Metres/second
V Volume Metre3
V Voltage Volts
vA Velocity of Water in Reservoir Supply Pipe Metres/Second
vav Average Velocity Metres/Second
vn Velocity of Water in nth Tap Supply Pipe Metres/Second
W Power Watts
We Electrical Power Watts
Win Power Supplied to Pump Watts
Wout Power Supplied by Pump Watts
Δh Total Difference in Head between Tanks Metres
ΔH Residual Head Metres
ΔP Residual Pressure Newtons/Metre2
γ Pump Efficiency
μ Kinematic Viscosity Metres 2/Second
ρ Density (ro) Kilogrammes/Metre3

ii. Scope

This manual is intended to aid the water projects worker or volunteer in the following ways :

  1. To explain, from first principals and using basic physical relations, the origin of the equations that design water systems.
  2. To systematically outline the key equations and explain how to apply them to scenarios where there is no text book method readily available.
  3. To give step by step numerical solutions to some of the more common and also some special scenarios.
  4. To systematically lay down the design parameters for gravity flow water systems and show how they should be applied to a design.

Sections 2-7 explain the basic concepts, show how the core equations are derived, explain perfect and imperfect systems and cover the analysis of pumps and turbines.

Sections 8 and 9 show how to apply the core equations to a series of common and special scenarios.

The worked examples 1-8 show how to simplify the equations developed in Sections 8 and 9 for practical use and give step by step numerical examples for each scenario. In addition worked example 9 shows the design process applied to a sample gravity flow water system design.

Appendices 1-6 give more complex derivations of the core relations, explanations of useful processes in the calculations and additional technical data.

For the experienced water system designer I would suggest reading through Sections 8 and 9, Appendix 4 and Worked Example 9 in particular.

Any questions about this manual should be addressed to Dodger at dodger@irational.org.

iii. References

  1. A Handbook of Gravity-Flow Water Systems : Thomas D.Jordan Jnr. : Intermediate Technology Publications 1996.
  2. Basic Engineering Sciences and Structural Engineering for Engineer-in-Training Examinations : Apfelbaum & Ottesen : Hayden Book Company 1970.
  3. Friction Loss Characteristics Chart : Polyethylene (PE) SDR-Pressure Rated Tube : PISTA & Gustavo Urbano.

iv. Notes

  1. In the numerical calculations for the Worked Examples, the asterisk (*) denotes the multiplication sign and the slash (/) the divide sign.
  2. In general, metric fundamental units (Metres, Kilogrammes and Seconds) have been used in the Worked Examples, the two main exceptions being inches for pipe diameters and Litres/Second (LPS) for flow rates.