 #1
 83
 5
 Homework Statement:

A centrifugal pump has an NPSH of 4 metres. It is used to transfer hot wort from kettle, open to atm prsssure, to a whirlpool. Calculate the minimum vertical distance the pump must be positioned below the outlet of the kettle to enable effecient pump operation.
Wort flow rate is 200 hl h1
Vapour pressure of wort at 100 degrees C = 99 kPa
Wort density = 1065 kg m3
Pipe length from kettle to pump inlet = 8.5 m
Pipe internal diameter = 75 mm
Pipe friction factor = 0.002
Acc due to grav = 9.81 m s2
Atm pressure = 101.3 kPa
 Relevant Equations:

Darcys Friction Equation
Bernouilli Equation
Really need to help getting started with this one.
They've given NPSH = (Ps  Pvp)/qg
Where Ps = Suction pressure at pump inlet
Pvp = vapour pressure of liquid at temp of pumping
q = density of liquid
g = acc due to grav
They've also provided Darcys friction Equation
The examiners tip (its a past exam paper) said that people used equations that enable fast solutions, but expected way was Bernouilli Eq.
Bernouilli Eq:
P2/q + (V2^2)/2 + gz2 = P1/q + (V1^2)/2 + gz1
So P2 is 99,000 Pa
q = 1065 kg m3
V2 is 200 hl h1 = 5.5x10^3 m3/s
Z2 = 8.5m
P1 = atmospheric pressure?
I dont have V2
Im looking for z1.
Am I on the right track here, need some guidance please.
They've given NPSH = (Ps  Pvp)/qg
Where Ps = Suction pressure at pump inlet
Pvp = vapour pressure of liquid at temp of pumping
q = density of liquid
g = acc due to grav
They've also provided Darcys friction Equation
The examiners tip (its a past exam paper) said that people used equations that enable fast solutions, but expected way was Bernouilli Eq.
Bernouilli Eq:
P2/q + (V2^2)/2 + gz2 = P1/q + (V1^2)/2 + gz1
So P2 is 99,000 Pa
q = 1065 kg m3
V2 is 200 hl h1 = 5.5x10^3 m3/s
Z2 = 8.5m
P1 = atmospheric pressure?
I dont have V2
Im looking for z1.
Am I on the right track here, need some guidance please.