Centrifugal pump: high outlet pressure but no flow rate at the outlet. What’s the reason?
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The heat exchanger is at the end of the pipeline; the water temperature drops from 121°C to 100°C. The pump is controlled via frequency variation to adjust the flow rate at the end of the pipeline. Currently, the outlet pressure of the pump has increased and its frequency has risen, but the flow rate remains unchanged or even decreases, resulting in severe vibration. .
Personal opinion: Within the 20% speed adjustment range, flow rate is proportional to the square of the speed, while head is proportional to the cube of the speed. Currently, the pressure at the pump outlet is increasing; both the head and the flow rate increase as well. This is in line with the pump’s characteristic curve. The characteristic curve of the pipeline shows an increase in flow rate and velocity, as well as an increase in pipeline resistance. For efficient heat transfer, it is generally necessary for the fluid to be in a turbulent regime, that is, within the region where resistance is proportional to the square of velocity, in order to achieve the highest heat transfer coefficient. The intersection point of the pump’s characteristic curve and the pipeline’s characteristic curve is the actual operating point of the pump.
“The pump is controlled via frequency variation to adjust the flow rate at the end point. Currently, the outlet pressure of the pump has increased and the frequency has risen, but the flow rate has not changed – in fact, it has decreased – along with severe vibration, which indicates that the pump’s flow rate has reduced; there is a valve somewhere between the pump’s outlet and the end of the pipeline that is causing throttling. When the pump has high outlet pressure and low flow rate, it vibrates significantly. At the same time, with the pipe diameter remaining constant, the flow velocity of the medium depends only on the flow rate; a decrease in flow velocity indicates throttling in the pipe.
First, it is necessary to determine whether the traffic has truly increased The outlet pressure of the pump increases and its frequency rises; if the flow rate decreases, vibration will definitely increase
Could this be related to the diameter of the inlet pipe?
The pump outlet has a gradual increase in diameter, with a section of smaller diameter followed by a larger diameter. . . Flowmeters also have a reduction in diameter, from large to small. .
The pump outlet has a gradual increase in diameter, with a section of smaller diameter followed by a larger diameter. . . Flowmeters also have a reduction in diameter, from large to small. .
The pump outlet has a gradual increase in diameter, with a section of smaller diameter followed by a larger diameter. . . Flowmeters also have a reduction in diameter, from large to small. .
When manually adjusted to 40, 50%, 20, and Hz, the situation indeed changed, and the flow rate gradually increased. . . .
Limit the pump frequency to no more than 50% to ensure the flow rate meets the requirements. . The flow rate gradually increases; there is no situation where the frequency keeps rising while the flow rate remains unchanged. What is the reason for this?
Is water at 121℃ pressurized condensate?