Fluid Mechanics
1. Using diagrams and/or graphs, explain the following terms:
a. Pressure Head pressure head [′presh·ər ‚hed]
(fluid mechanics)
Also known as head.
The height of a column of fluid necessary to develop a specific pressure.
The pressure of water at a given point in a pipe arising from the pressure in it.
b. Total Discharge Head
Total discharge head refers to the actual physical difference in height between the liquid level in the pit and the highest point of the discharge pipe or water level in the outlet.
c. NPSH
Net Positive Suction Head (NPSH). The measurement of liquid pressure at the pump end of the suction system, including the design of the pump.
d. Suction Lift
Pump Performance Curve
The pump characteristic is normally described graphically by the manufacturer as a pump performance curve. The pump curve describes the relation between flow rate and head for the actual pump. Other important information for proper pump selection is also included – efficiency curves, NPSHr curve, pump curves for several impeller diameters and different speeds, and power consumption.
Increasing the impeller diameter or speed increases the head and flow rate capacity - and the pump curve moves upwards.
The head capacity can be increased by connecting two or more pumps in series, or the flow rate capacity can be increased by connecting two or more
e. Pump Efficiency
Pump Efficiency
The term pump efficiency is used on all types of pumps to describe the ratio of power supply to the drive shaft against water horsepower.
Pump Efficiency ηp = Water horse power x 100%
Required power or
Pump Efficiency ηp = Q x H x ρ x g ω x T
Where: Q = capacity (m³/s)
H = total head/pressure (m)
ρ = fluid density (kg/m³) g = acceleration due to gravity (m/s²) ω = shaft angular velocity (rad/s)
T = shaft torque (Nm)
f. Available NPSH The difference between standard atmospheric pressure and the combination of atmospheric pressure at elevation, total dynamic suction lift, vapor
a. Pressure Head pressure head [′presh·ər ‚hed]
(fluid mechanics)
Also known as head.
The height of a column of fluid necessary to develop a specific pressure.
The pressure of water at a given point in a pipe arising from the pressure in it.
b. Total Discharge Head
Total discharge head refers to the actual physical difference in height between the liquid level in the pit and the highest point of the discharge pipe or water level in the outlet.
c. NPSH
Net Positive Suction Head (NPSH). The measurement of liquid pressure at the pump end of the suction system, including the design of the pump.
d. Suction Lift
Pump Performance Curve
The pump characteristic is normally described graphically by the manufacturer as a pump performance curve. The pump curve describes the relation between flow rate and head for the actual pump. Other important information for proper pump selection is also included – efficiency curves, NPSHr curve, pump curves for several impeller diameters and different speeds, and power consumption.
Increasing the impeller diameter or speed increases the head and flow rate capacity - and the pump curve moves upwards.
The head capacity can be increased by connecting two or more pumps in series, or the flow rate capacity can be increased by connecting two or more
e. Pump Efficiency
Pump Efficiency
The term pump efficiency is used on all types of pumps to describe the ratio of power supply to the drive shaft against water horsepower.
Pump Efficiency ηp = Water horse power x 100%
Required power or
Pump Efficiency ηp = Q x H x ρ x g ω x T
Where: Q = capacity (m³/s)
H = total head/pressure (m)
ρ = fluid density (kg/m³) g = acceleration due to gravity (m/s²) ω = shaft angular velocity (rad/s)
T = shaft torque (Nm)
f. Available NPSH The difference between standard atmospheric pressure and the combination of atmospheric pressure at elevation, total dynamic suction lift, vapor