Page 391 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Ejectors and Mechanical Vacuum Systems 359

320 320
I
I
280 280
Break Point 80%
� -
o_
Steam 20 psia
e 240 - Pressure""- I 240�
::, Back I -· -
Cl) -· ,.... ,.... Q.)
Cl)
'
e 200
a.. I .... 200 �
Q.)
Cl)
Cl)
::,
....
... 160 Cl) 160 a..
c
Q.)
0
Cl)
Q.)
(,) I .... c
Q,
::::, t ...
0
Cl') 120 " """
(,)
c / 0 � 120 (,,)
::>
c::,, CD 0) (/)
Cl) / \ Break Point 80% E .� Cb
Q.) 80 ::, .::: ' 80 c
Cl / Steam 19 psia ,also ·c �! -�
E
Cl)
/ 90% Steam 20 Q.)
0\0l!_'
40 v psia Back Pressure :i: � Q. 40 Cl
�Shut-off �
40 80 120 160 200 240 18 19 20 21 2l
Figure 6-14. Effect of steam back-pressure varia- Design Capacity % Maximum Safe- Discharge
1
tions with steam pressure. By permission, Freneau, Pressure ond System
P. [4]. Pressure, psio
Q) ...... --+--,.-,;.,'--+-�--1��--1-��-+-�--1,__����4-��
�6��...._.�
Cl)
Cl)
....
Q)
a..41+-,,-,.-+,,._�-+--�-+��-+-�--1��--1-����--l-��-1-�--1
"""
(,,)
0
ID 2tN�--t-�-1r-�-1-�-1r-�-t-�--t��-t-�--t��+-�-1
Figure 6-15. Effect of back-pressure on single-
stage exhausters. By permission, Ketema, Schutte
& Koerting Div. and Ketterer, S. G. and Blatchley, 50 100 150 200 250
C. G. [8]. Increase in Steam Consumption 1 %
The non-condensables leaving a surface condenser are 2. Barometric or Low Level Jet Condenser
saturated with water vapor at the temperature corre-
sponding to the pressure. For a process condenser the In this case the temperature at the air outlet of this
vapor corresponds to the process fluid. type condenser is generally assumed to be 5°F above the
inlet temperature of the cooling water. In addition to the
normally expected air leakage, an allowance must be
I. SU1f ace Condenser made for air liberated from the injection water [10].
Types of Loads
To provide for sufficient total capacity, the tempera-
ture at the air outlet of a well designed surface condenser Air Plus Water Vapor Mixtures
is generally assumed to be about 7.5°F below the temper-
ature of saturated steam at the absolute pressure in the The Heat Exchanger Institute [11] references all tests
condenser L 12]. and calculations for jet performance to 70°F air equiva-