When analyzing the energy consumption of the split case pump under different adjustment methods, the article only analyzes the two adjustment methods currently widely used in valve adjustment and pump variable speed adjustment. Since the parallel and series operation of split case pumps aims to increase the pressure head or flow rate, they are not used much in the chemical industry, and their energy consumption can be analyzed, and the method is basically the same. How to reduce the energy loss of the split pump during operation, which is to reduce the price of the water pump on the other hand.
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1. Power consumption when the valve adjusts the flow rate
When the split case pump is running, the power N of the motor input to the pump shaft is:
N=vQH/η
where N——shaft power, w;
Q——The effective pressure head of the water pump, m;
H——The actual flow rate of the pump, m3/s;
V——The specific gravity of the pump fluid, N/m3;
Η——The efficiency of the water pump.
When using a valve to adjust the flow from Q1 to Q2, the shaft power consumed at the operating point A2 is:
NA2=vQ2H2/η
VQ2H3——The actual useful power, W;
VQ2H2-H3——The power lost on the valve, W;
VQ2H21/η-1——The power lost by the centrifugal pump, W.
2. Power consumption when adjusting the flow rate at a variable speed
Because the proportional law of the split case pump is used in the variable speed analysis, according to its application conditions, the following analysis means that the variable speed range of the centrifugal pump is within ±20%, and the efficiency of the split case pump itself does not change much. When the motor is used to adjust the flow rate to flow rate Q2 at a variable speed, the shaft power consumed by the pump at operating point A3 is:
NA3=vQ2H3/η
can also be transformed into:
NA3=vQ2H3+vQ2H31/η-1(2)
where vQ2H3——the actual useful power, W;
VQ2H31/η-1——The power lost by the pump, W.