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For standard pressure vessels, COMPRESS provides
two inputs for pressure: one for internal pressure
and one for external pressure. A positive numerical
value is entered in both cases. But for heat
exchangers only a single input is provided for
pressure. The single input may take positive values
for internal pressure, and will take negative
values for external pressure. Note that there is
provision for 8 possible sets
of design conditions; each set is a
combination of pressures
and temperatures for the shell side and tube side
chambers that exist concurrently. Component
dialogs for heat exchangers show the design
pressure and temperature but these values can be
changed only through the Heat Exchanger Wizard.
The COMPRESS Manual provides an example of an
exchanger designed for vacuum. Generally, a
different set of conditions out of the 8 possible
sets must be defined for internal or external
pressure condition for each chamber. Refer to the
COMPRESS Heat Exchanger Manual: select
COMPRESS Help menu,
select Heat Exchanger
Help, select the chapter on the Shell Side
Design Conditions and on the Tube Side Design
Conditions and refer to discussion of inputs
for Pressure.
You must activate additional sets of design
conditions by "checking" additional
options Design Condition
Active on the Tube
Side Design Conditions tab of the
Heat Exchanger dialog.
Enter the shell side and tube side pressure and
temperature for each set of design conditions.
Entering the general case of an exchanger designed
for internal pressure plus a vacuum condition for
shell side and tube side chambers will take 3 sets
of design conditions.
For example, for the following case:
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Tube side: 100 psi @ 500° F & full
vacuum @ 300° F
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Shell side: 250 psi @ 650° F & full
vacuum @ 325° F
The following design conditions would be input
into COMPRESS:
| |
Tube side |
Shell Side |
| Condition 1 - Operating |
100 psi @ 500° F |
250 psi @ 650° F |
| Condition 2 - Tube Side Vacuum |
−15 psi @ 300° F |
250 psi @ 650° F |
| Condition 3 - Shell Side Vacuum: |
100 psi @ 500° F |
−15 psi @ 325° F |
The inputs in the Heat
Exchanger Dialog should look like this:
Tube Side Design conditions:
Shell Side Design Conditions:
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