Pumping Systems
Pumps consumed a lot of energy in comparison to other sub-components of a facility. Almost every building and industry will have a pump system, be it a simple domestic pump to 1MW pumps at water treatment plants.
With so much energy wasted, why are pumps usually ignored when it comes to savings - this is probably due to the fact that before one can think about saving pumping energy, they have to evaluate (if existing) or design the piping system! This is where many falter and the fear of not having enough flow creates the tendency to overdesign a system.
For pumps, it starts with the pump curves of the pump itself. Without the pump curve, finding ways to optimize the system becomes a tedious effort because the pumps will behave differently when operating at different points of the pump curve. To understand a pump curve one needs to know the basics on reading the curve.
Reading the Curve
The curve is easy to read and understand! Pressure (usually
system) is shown in the vertical axis and flowrate on the
horizontal. The curve has a sloping nature which droops on
the right side. The higher the flowrate, the lower the
pressure and vice versa. A pump has a design point, i.e. a
preferred flowrate and pressure value BUT in the real world
it can work anywhere on the curve and in some extreme
cases, away from the curve!
Pressure is inversely propottional to flow. So when the
pressure in your system is higher than the design, the flow
reduces and if the pressure decreases ,the flow increases.
The system can be imbalanced if the design values do not
reflect the actual operating conditions, for example, a
designer incorrectly calculated the pressure and the in
actual operation the pressure is lower, this will increase
the flowrate and the overall performance will be affected.
A fluid in a piping system has to overcome three losses :
Static Pressure, Hs (simply the height between the bottom
to the top), Friction losses, Hf and Velocity losses, Hv
Thus the total head
is the sum of all three losses and this is the total
head or pressure the system has to overcome. Add the
flow into the fray and you will now have to find a
pump that provides you the desired flow and the energy
to overcome the friction losses