The target and function of vacuum pump on water chamber:
A)Before the system started and the head of water pump (for water circulation) is less than the request of condenser’s water chamber, the vacuum pump can build siphon on the side of condenser to ensure the water chamber of condenser can be filled up by circulation water.
B)The front and back side of condenser is negative pressure when system started, then some un-condensable gas will be released from circulation water and gather at the upside of water chamber, or even in the upper tubes to blockage the water flow, and finally lessen the cooling area. During when, vacuum pump can help to evacuate those gas to ensure high heat exchange efficiency and service life for condenser.
Purpose: the created siphon by vacuum pump can lower down the request on head of water pump, hence the power consumption of water pump can be reduced to finally reduce the operation fee of power plant.
The point O on seal level: the air on atmosphere (PO) dissolved on the water
At Point A (water chamber before condenser):
when the mixed gas of air and water vapor Pa<Po, the dissolution degree of air on water is reduced, then some air will be released from water; if the water chamber before condenser is in positive pressure, that is to say Pa>Po, then no air would be released from water.
At Point B (water chamber after condenser):
since the pressure of circulation water reduced but its temperature increased, the dissolution degree of air on water reduced continually, then some more air would be released from water.
Above description tells we can know total volume of gathered air, equaling to volume of evacuated air, on water chamber before and after condenser, through the dissolution degree of air on water in the whole process of water circulation. Followed sketch is the dissolution degree of air on varied water temperature for reference:
Conclusion:
a vacuum pump is necessary to lower the cost of power plants who want to use theory of siphon to reduce the amount of capital on cooling water system.
The released amount of water on two water chamber is decisive factor on vacuum pump selection.
Tags: liquid ring vacuum pump ,experience
Editor: Shell Hu– EVP Vacuum Solution
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