Page 411 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Ejectors and Mechanical Vacuum Systems 379

Table 6-14
Pressure-Temperature-Volume of Saturated Steam

Absolute Absolute Absolute
Pressure Temperature Volume Pressure Temperature Volume Pressure Temperature Volume
Ins. Hg oF. cu. ft./lb. Ins. Hg OF. cu. ft./lb. Ins. Hg OF. cu. ft./lb.
------
0.1803 32 3306 3.0 115.06 231.6 20.0 192.37 39.07
3.1 116.22 224.5 21.0 i94.68 37.32
3.2 117.35 217.9 22.0 196.90 35.73
3.3 118.44 211.8 23.0 199.03 34.28
0.20 34.57 2996.0 3.4 119.51 205.9 24.0 201.09 32.94
0.25 40.23 2423.7 3.5 120.56 200.3 25.0 203.08 31.70
0.30 44.96 2039.4 3.6 121.57 195.1 26.0 205.00 30.56
0.35 49.f)6 1761.0 3.7 122.57 190.1 27.0 i 206.87 29.50
0.40 52.tH 1552.8 3.8 123.53 185.5 28.0 208.67 28.52
0.45 55.89 1387.7 3.9 124.49 181.0 29.0 210.43 27.60
0.50 58.80 1256.4 29.922 212 26.80
0.60 63.96 1057. l 30 212.13 26.74
0.70 68A.1 913.8
0.80 72.32 805.7
0.90 75.84 720.8 Lb. Per Sq.
4.0 125.43 176.7 In. Abs.
4.5 129.78 158.2
5.0 133.76 143.25 14.696 212 26.80
5.5 137.41 131.00 15 213.0:3 26.29
1.00 79.03 652.3 6.0 140.78 120.72 20 227.96 20.089
1.10 81.96 596.0 6.5 143.92 112.00 30 250.33 13.746
1.20 84.64 549.5 7.0 146.86 104.46 40 267.25 10.498
1.30 I 87.17 509.1 7.5 149.63 97.92 50 281.01 I 8.515
1.40 89.51 474.9 8.0 152.24 I 92.16 60 292.71 7.175
1.50 91.72 444.9 8.5 154.72 87.08 70 302.92 6.206
1.60 93.81 418.5 9.0 157.09 82.52 i 80 312.03 5.472
1.70 95.78 395.3 9.5 159.48 78.48 90 320.27 4.896
1.80 97.65 374.7 100 327.81 4.432
1.90 99.43 356.2
125 344.33 3.587
150 358.42 I 3.015
2.00 101.14 339.2 10.0 161.49 74.76 175 370.75 ! 2.602
2.10 102.77 324.0 11.0 165.54 68.38 200 381.79 2.288
2.20 I 104.33 310.3 12.0 169.28 63.03 225 391.79 2.0422
2.30 105.85 297.4 13.0 172.78 58.47 250 400.95 1.8438
2.40 ! 107.30 285.8 14.0 176.05 54.55 275 409.43 1.6804
2.50 108.71 274.9 15.0 179.14 51.14
2.60 ll0.06 265.0 16.0 182.05 48.14
2.70 111.37 255.7 17.0 184.82 45.48 300 417.33 1.5433
2.80 112.63 247.2 18.0 187.45 43.11 350 431.72 1.3260
2.90 113.86 239.1 19.0 189.96 40.99 400 444.59 1.1613
I I
Values obtained directly or by interpolation from Keenan & Keyes-"Thermodynamic Properties of Steam," John Wiley & Sons, 1936
by permission and Courtesy C. H. Wheeler Co., Philadelphia, Pa.

tion at zero suction flow with the motive fluid maintaining tion of air ( 1) overloads the aftercondenser, the discharge
the required volume and energy to produce the necessary mixture can be recycled to control the pressure [3].
diffuser velocity. This is "shut-off" operation. A decrease in Figure 6-32 illustrates ejector systems with large con-
motive pressure below the stability point will cause a dis- densable loads which can be at least partially handled in
continuity in operation and an increase in suction pres- the precondenser, Controls are used to maintain constant
sure. If the motive fluid rate increases, the suction pressure suction pressure at varying loads (air bleed), or to reduce
will increase or capacity will decrease at a given pressure. the required cooling water at low process loads or low water
Figure 6-31 illustrates control schemes for the single temperatures [2]. The cooler water must not be throttled
stage unit wl ich allow greater stability in performance. As below the minimum (usually 30%-50% of maximum) for
the load changes for a fixed suction pressure, the process proper contact in the condenser. It may be controlled by
fluid is replaced by an artificial load (usually air; Figure 6- tailwater temperature, or by the absolute pressure.
31, item 1) to maintain constant ejector operation. An The controls for larger systems involve about the
artificial pressure drop can be imposed by valve (2), same principles unless special performance is under
although this is not a preferred scheme. Wben the addi- consideration.