Calculating pump pressures and power (Bernouilli)

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The discussion focuses on calculating pump pressures and power using Bernoulli's equation, with specific parameters provided such as flow rate, pipe area, and frictional losses. The user attempts to determine the pressure at the inlet and outlet, as well as the necessary pumping power, but expresses uncertainty about the exact locations for these calculations. Initial calculations yield pressures of 47.87 kPa at the inlet and 107.71 kPa at the outlet, along with a power requirement of 8.53 kW, but the user suspects errors in their pressure calculations. Clarification is sought regarding the definition of pump inlet and outlet locations, as well as the height data needed for accurate calculations. The discussion highlights the importance of understanding system diagrams and the correct application of Bernoulli's principles in fluid mechanics.
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Homework Statement


http://imgur.com/ktfgCAL

flow rate: 0.057 m^3/s
cross sectional area of all pipes: 1.864*10^-2 m²
frictional losses inlet pipe: 1.83m
frictional losses outlet pipe: 3.66m
density: 1000 kg/m^3
g= 9.81 N/kg

Asked:
pressure at inlet
pressure at outlet
necessary pumping power

Homework Equations


Bernouilli: http://imgur.com/EEptkNX where h_A is the energy added by the pump and h_r and h_l are the losses
pumping power= q*rho*g*h

The Attempt at a Solution


first of all, i am not sure what location they actually mean exactly by pump inlet and outlet (is it in the tank or really at the pump?)

inlet: I assumed p1 to be 0, v1=v2 and z1=0 and z2=3.05m which results in a p2 of 47.87kPa (i assumed h_A to be equal to 0, not sure if this is correct)
outlet: using the previous value as p1 now, assuming v1=v2 and z1=0 and z2=12.2m i found a p2 of 107.71 kPa
power: 0.057*1000*9.81*15.25 = 8.53kW

Apparentely, all my answers seem to be wrong. I'm fairly sure that I am making a critical mistake for the pressure calculations, but I really don't understand what could be wrong in my power calculation.

Thanks in advance :)
 
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Xengine said:

Homework Statement


http://imgur.com/ktfgCAL

flow rate: 0.057 m^3/s
cross sectional area of all pipes: 1.864*10^-2 m²
frictional losses inlet pipe: 1.83m
frictional losses outlet pipe: 3.66m

Asked:
pressure at inlet
pressure at outlet
necessary pumping power

Homework Equations


Bernouilli: http://imgur.com/EEptkNX where h_A is the energy added by the pump and h_r and h_l are the losses
pumping power= q*rho*g*h

The Attempt at a Solution


first of all, i am not sure what location they actually mean exactly by pump inlet and outlet (is it in the tank or really at the pump?)

The pump inlet and outlet seem to be indicated pretty clearly on the system diagram. The pump outlet is located further away from the pump itself apparently to accommodate the shut-off valve.
 
SteamKing said:
The pump inlet and outlet seem to be indicated pretty clearly on the system diagram. The pump outlet is located further away from the pump itself apparently to accommodate the shut-off valve.

But there isn't any data given about the exact height of the outlet point for example, i think the arrow just indicates the inlet and outlet pipe rather than the specific point that the pressure needs to be calculated on, or am I missing something?
 
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