Solution for High-Flow and Efficient Conveyance

Flow rate, also called displacement, refers to the amount of liquid discharged by a pump per unit time. It can be expressed in two ways: by volume and by weight.
Volumetric flow rate is denoted by Q, with units being cubic meters per second (m³/s) and liters per second (L/s).
Weight flow rate is denoted by G, with units being tons per hour (t/h) and kilograms per second (kg/s).
The relationship between weight flow rate and volumetric flow rate is:

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L/s→m³/s(International System of Units)
1L/s=0.001m3/s
Formula:
Flow (m3/s) = Flow (L/s) x 0.001
Example: 
20L/s=20 x 0.001=0.02m3
L/s→m³/h(Commonly used engineering units)
1L/s=3.6m3/h 
Formula:
Flow rate (m3/h) = Flow rate (L/s) × 3.6
1 hour = 3600 seconds
1L/s=0.001m3/s x3600s/h=3.6m3/h Example: 50L/s=50x3.6=180m3/h

The flow rate of a centrifugal pump is related to various parameters in a certain way. Usually, the relationship between the main performance parameters is represented by a curve graph, which is called the centrifugal pump performance curve. Essentially, the centrifugal pump performance curve is the external manifestation of the operating law of the liquid in the pump.
The performance curve of a centrifugal pump includes the performance curve of flow rate and head (Q-H), the performance curve of flow rate and efficiency (Q-η), the performance curve of flow rate and shaft power (Q-P), and the performance curve of flow rate and suction net positive suction head (Q-NPSH). These curves are obtained under a certain rotational speed. Different rotational speeds correspond to different performance curves. 
On the performance curve, for any given flow point, a set of corresponding parameters of relevant head, power and efficiency can be found. These parameters are usually referred to as operating conditions. The operating condition corresponding to the highest efficiency point and the operating point of the centrifugal pump is called the optimal operating condition, and it also represents the optimal flow parameter value. 
In production practice, it is necessary to select the operating point of the pump by referring to the performance curve of the pump. Only in this way can the pump always operate within the high-efficiency range. Only by using the performance curve of the pump can one normally monitor the operation of the pump and analyze the operating state of the liquid within the pump.

The Q-H curve represents the head (lift) of the pump at a certain flow rate. Head is usually measured in meters (m). The Q-H curve is not affected by the type of liquid being transported by the pump. As shown in the figure below: the higher the flow rate, the higher the head; the lower the flow rate, the lower the head.

The Q-P flow-power curve represents the relationship between flow rate and shaft power. Shaft power is the sum of the pump's water power and mechanical loss power. The shaft power (P) of a pump refers to the actual input power required by the pump shaft.
The formula for calculating shaft power:

Parameter explanation:
P: Shaft power (kW)
ρ: Liquid density (kg/m³, for water at room temperature, it is taken as 1000 kg/m³)
Q: Flow rate (m³/s, if the unit is m³/h, it needs to be divided by 3600 for conversion)
H: Head (m)
η: Pump efficiency (0~1, it needs to be checked from the pump performance curve or sample)
102: Conversion coefficient for units
Example: 
A certain water pump is used to convey clear water. The flow rate is 100 m³/h, the head is 32 meters, and the efficiency is 70%.
Flow conversion:
Axial power:

Motor selection: Shaft power multiplied by safety factor (usually 1.1 to 1.2) is taken as the motor's rated power.
Motor power: 12.41 × 1.15 = 14.27 kW. Select a 15 kW motor.
The relationship between shaft power consumption and flow rate is as shown in the following figure: Shaft power increases as the flow rate increases.
Axial power consumption
The Q-η flow efficiency curve refers to the efficiency changes of the pump at different flow rates. It usually takes the form of a parabola and there is a highest efficiency point (the optimal operating point).
The efficiency calculation formula

P Power calculation

Examples
The pump conveys clear water. ρ=1000kg/m³
Flow rate:
Head: 30 m
Synchronous power: 10 kW
Effective power:

The performance curves of flow rate and cavitation margin (Q-NPSH) will be analyzed separately in the next chapter on cavitation margin.