In the second example, we find that the water pump is insufficient to cater for the system curve.
P
system curve 1
26
dP
calculated operating point which
lies above the pump curve
19
pump curve
system curve 2
In order to use the mini chiller, it is necessary for the piping network to have a characteristic of
System Curve 2. The only way to do so is to redesign the piping system to give a lower friction
loss.
Alternatively, we can use the pump P-Q curve during commissioning of the hydronic system. To
do so, we need to measure the water pressure at the discharge port. This value is quite close to
the actual head pressure developed by the pump. By plotting this pressure on the P-Q curve, we
can then determine the approximate flowrate flowing through the system and compare it with the
design requirement. Appropriate action can then be taken to ensure sufficient and correct amount
of flowrate.
P1
Water pressure measurement
To load with a design
flowrate, q, and total
pressure loss, p
MINI CHILLER
P
Design point
Actual opening point
Measurement
P1
Q
q
Section 5 Page 78
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