To understand the content of this post please read Wikipedia Page on Siphon.
Once through CW systems are relatively unknown in Thermal Power Plants being constructed today but there are many old ones. Let us look at following image on Wikipedia page.
B can be the top point of Condenser Water Box and C the end of the outlet pipe.
The Siphon works on the basis of height difference hc. In CW System hc may be zero but the CW Pump Head equal to hc will simulate it.
In case of Siphon both inlet and outlet pipes are under vacuum. In CW System the outlet pipe will be under vacuum but inlet pipe may be under positive pressure or slight vacuum at Condenser inlet.
Since the Cooling Water picks up heat in the Water Box the pressure in Water Box should be higher than Vapour Pressure of Water at Outlet Temperature with some margin.
During Start up Vacuum is created by Condenser Water Box Priming Ejector or Vacuum Pump.
The Priming Ejector/Vacuum Pump needs to be run periodically to remove liberated dissolved gases from Cooling Water from Condenser Water Box.
Recently I visited one Thermal Power Station where I had to tell them the importance of running Water Box Priming Ejector periodically.
Once through CW systems are relatively unknown in Thermal Power Plants being constructed today but there are many old ones. Let us look at following image on Wikipedia page.
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| From Wikipedia |
The Siphon works on the basis of height difference hc. In CW System hc may be zero but the CW Pump Head equal to hc will simulate it.
In case of Siphon both inlet and outlet pipes are under vacuum. In CW System the outlet pipe will be under vacuum but inlet pipe may be under positive pressure or slight vacuum at Condenser inlet.
Since the Cooling Water picks up heat in the Water Box the pressure in Water Box should be higher than Vapour Pressure of Water at Outlet Temperature with some margin.
During Start up Vacuum is created by Condenser Water Box Priming Ejector or Vacuum Pump.
The Priming Ejector/Vacuum Pump needs to be run periodically to remove liberated dissolved gases from Cooling Water from Condenser Water Box.
Recently I visited one Thermal Power Station where I had to tell them the importance of running Water Box Priming Ejector periodically.
