If two pumps identical in all respects and each capable of delivering a discharge Q against a head H are connected in series, the resulting discharge is
Cavitation parameter a defined in terms of NPSH (net positive suction head) and net head H as, σ =
In a pump installation the local atmospheric pressure is 10 m of water, vapour pressure head is 0.4 m (abs), height of the pump above sump water level is 5 m. For a head loss in the suction side of 0.6 m, the NPSH is
Zs = elevation of pump above the liquid surface in the sump. If the pump is set below the liquid level in the sump then Zs would be negative.
Water is to be lifted by a net head of 184 m. Identical pumps with specific speed of 30 and rotative of 1500 rpm capable of discharging 200 L/s are available. The number of pumps required is [Take 1843/4 = 50]
∴ Q = 1000 L/s
Number of pumps = 1000/200 = 5
Water is pumped through a pipeline to a hieght of 10 m at the rate of 0.1 m3/s. Frictional and other minor losses are 5 m. Pumping power required, in kW is
Total manometric head,
H = 10 + 5 = 15 m
P = g Q H = 9:81 x 0.1 x 15
= 14.715 kW
In a reciprocating pump without air vessel, the friction head in the delivery pipe is maximum at the crank angle θ =
hfs is maximum at
The indicator diagram of a reciprocating pump is a plot of
Actual indicator diagram for a single stage "reciprocating pump is represented by
An air vessel in the delivery side of a reciprocating pump
Function ofair vessel fitted on delivery side:
(i) Almost constant delivery discharge is obtained.
(ii) Reduction in friction loss and hence saving in power.
Which one of the following is not a positive displacement pump?
Note that centrifugal pump is not positive displacement pump. It is a rotodynamic or dynamic pressure pump.