Estimation of water pump head

Head, flow rate and power are important parameters for examining the performance of a pump:

1.The flow rate of a water pump is also called the water delivery volume. It refers to the amount of water delivered by the pump in a unit of time. It is represented by the symbol"Q", and its unit is liters/second, cubic meters/second, and cubic meters/hour.

2. The head of a pump refers to the height at which the pump can lift water. It is usually represented by the symbol "H", and its unit is meter. The head of the centrifugal pump is based on the centerline of the impeller and consists of two parts.

The vertical height from the centerline of the pump impeller to the surface of the water source, that is, the height at which the pump can suck up the water, is called the suction head, the vertical height from the centerline of the pump impeller to the water surface of the water tank, that is, the height at which the pump can press the water is called the pressure head.That is, pump head = suction head + pressurized head. It should be noted that the head shown on the nameplate refers to the head generated by the pump itself. It does not include the lost head caused by frictional resistance of the water flow in the pipeline. When choosing a water pump,attention can not to be ignored. Otherwise, water will not be pumped.

3.In a unit of time, the amount of work done by the machine is called power. It is usually represented by the symbol "N". Commonly used units are: kg·m/s, kilowatts, and horsepower. Usually the power unit of an electric motor is expressed in kilowatts; the power unit of a diesel or gasoline engine is expressed in horsepower. The power transmitted by the power machine to the pump shaft is called shaft power, which can be understood as the input power of the pump. Generally speaking, the pump power refers to the shaft power.

Due to the frictional resistance of the bearing and the packing, the friction with the water when the impeller rotates,the vortex of the water flow in the pump, the backflow of the gap,and the impact of the inlet and discharge,a certain amount of power is necessarily consumed, so it is impossible for the pump to completely change the input power of the water pump into effective power, it will have power loss, that is, the sum of the effective power of the pump and the power lost in the pump is the shaft power of the pump.

Pump head and flow rate calculation formula:

What does the pump head H = 25 mean?

Head H = 25 means that this machine can raise water up to 25 meters

Flow rate = cross-sectional area * flow rate

Flow rate needs to be measured by user: stopwatch

Pump head estimation:

The head of the pump has nothing to do with the power. It is related to the diameter of the pump impeller and the number of stages of the impeller. A pump with the same power may have a head of hundreds of meters, but the flow may be only a few cubic metres or the head may be only a few meters, but the flow may be hundreds of cubic metres. The general rule is that at the same power, the flow with high head is small, and the flow with low head is large. There is no standard calculation formula to determine the head.It is determined by using conditions and the model of the pump.

It can be calculated according to the pressure gauge of the pump outlet. For example, if the pump outlet is 1MPa (10kg/cm2), the head is about 100 meters, but the influence of suction pressure must also be considered.

For centrifugal pump, it has three heads: the actual suction head, the actual pressure water head, and the actual head. Unless otherwise specified, the head is generally considered to be the height difference between the two water surfaces.