Among water ring vacuum pumps, steam pumps, and water pumps, which one has the best vacuum-pumping performance?

Each has its advantages; the key is to consider the characteristics of the medium, as well as the operating conditions and energy consumption.

The medium is the exhaust steam from the condensing steam turbine.

If the vacuum level requirement is not high, a water jet pump is the preferred choice: it has no moving parts and offers high reliability.

Steam ejectors, water ejectors, and water ring pumps each have their advantages and disadvantages; the appropriate type should be chosen based on the application, unless special requirements exist! The brief explanation is as follows: 1) Water ejectors are suitable for pumping out fluids containing large amounts of condensable gases, but not suitable for situations involving large amounts of non-condensable gases ； The pressure should not be too close to the saturated vapor pressure of the working fluid; it’s better if it is at least several dozen mbar higher! 2) Steam ejectors can be combined in multiple stages to achieve very high vacuum levels (very low pressures; it’s often a mistake to think that a very low vacuum level means a very high pressure, when in fact the opposite is true). The lowest-level ejectors available on the market can have 5 or 6 stages, enabling them to reach a pressure as low as 1 Pa ； However, steam ejectors have very low efficiency at the exhaust stage, and often a liquid ring pump is used as the final stage in multi-stage steam ejector systems. 3) Water ring pumps are used at pressures of 100 mbar to 200 mbar or higher (with normal water as the working fluid), and they are more efficient than water ejectors (for pumping non-condensable gases) and steam ejectors ； As long as the final stage (the stage for discharging air) permits it, it is best to use a water ring pump. 4) For vacuum extraction in power plant condensers, considering the vacuum system alone, the optimal configuration is a combination of a primary steam ejector + tubular condenser + water ring pump, which allows the advantages of each pump to be fully utilized. However, from the perspective of overall system heat recovery, using a three-stage or two-stage steam ejector system with condensate water as the cooling fluid is the most optimal approach, with no waste of heat or condensate water at all.

None is better; only the one that is most suitable matters – it depends on your processing conditions

After encountering a problem like this, you will seem more foolish in the eyes of others; 99% of the time you will think that a certain type of pump is more suitable for your processes – but in reality, there is no perfect pump, only ones that are more suitable! And this really depends entirely on your process conditions and requirements; in the vast majority of process systems, a compromise is adopted for such designs!