Ejector Stage Characteristics

The most commonly used steam is 100 psig with 10-15° superheat, the latter characteristic in order to avoid the erosive effect of liquids on the throats of the ejectors. In Figure 7.31 the steam consumptions are given as lb of motive steam per lb of equivalent air to the first stage. Corrections are shown for steam pressures other than 100 psig. When some portion of the initial suction gas is condensable, downward corrections to these rates are to be made for those ejector assemblies that have intercondensers. Such corrections and also the distribution of motive steam to the individual stages are problems best passed on to ejector manufacturers who have experience and a body of test data. 

The characteristics of a two-stage condensing ejector are shown in Figure 23-9. For simplicity, it is here assumed that the intercondenser removes all water vapor from the air load to the second stage. 

Figure 17.9 Typical characteristic of a multiple-stage ejector.

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