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Interactive
Mode
In interactive mode commercial
software runs in the background. This mode is only
implemented for aircooler calculation, and works as
follows:
·
The user creates a
complete plain tube design in ACOL or Xace. In the next stage,
this design, with the corresponding tube bundle Geometry,
Process and Property data is loaded into hiTRAN.SP.
·
In hiTRAN.SP the
user can then change the tube bundle geometry (tube length, number
of tubes, no of tube passes...). As an additional feature it is
also possible to alter the airflow face velocity to adapt it to
the changed geometry!
·
During this process
hiTRAN.SP assigns a unique hiTRAN wire matrix Insert
determined by the bundle geometry, the process conditions and the
property data. This wire matrix insert is designed to take up
the entire allowable pressure drop in order to achieve maximum
heat transfer performance!
- In the
last step the changed bundle Geometry data and the increased
hiTRAN tube side heat transfer coefficients are transferred in
the background to the calling commercial Software package (Xace,
ACOL) to calculate the overall exchanger performance!
In
this mode hiTRAN.SP can operate in manual and automatic mode.
In manual mode the user
has to change the bundle geometry until the required heat duty
for the air cooler
is archieved In automatic mode the
programme iterates the bundle geometry untill the required heat
duty is archieved.
In order to "guide" the iteration process certain boundary
conditions like tube length to bundle width ratio can be set.
Currently this mode is only available for Xace calculations.
A detailed flowsheet explaining
the different modes you can find in the picture below:
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Operator runs "plain tube" case
in checking mode with:
ACOL, Xace
Creating an corresponding Output file
(*.aci ; *.htri) |
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Output file delivers the
input
information for the hiTRAN.SP |
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hiTRAN.SP
calculates the tubeside heat transfer coefficient for a
hitran wire matrix insert with a maximum packing density to give
optimal performance using all the allowable pressure drop.
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For parameter change there are two modes possible
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Manual Mode:
The User determines the following Parameters:
Process:
-
Allowable bundle pressure drop
- Face Velocity
Geometry:
- No. of tube rows
- No. of tubes per row
- No. of tube passes / bundle
- Tube length
- unheated / unfinned length
With the changed geometry / process condition an
overall
exchanger performance is calculated by calling ACOL /
Xace which is running in the background.
This calculated design takes into account the improved tube side
conditions by using hitran Inserts.
The user then alters the above mentioned parameters till the desired
design is reached.
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Automatic mode:
(Currently only implemented for Xace from HTRI) The User determines the boundary condition for the
automatic iteration for a max. allowable pressure drop.
These conditions are:
- area ration tube length to bundle with
- min. no. of tube rows
In automatic mode the geometry is changed until
it meets the chosen constrains mentioned above. During
this process the commercial software is called in the
background to calculate the overall air coller performance
For a fine tuning after successful iteration the face air
velocity can be altered.
It is also possible to switch to the manual mode in order to
perform some minor changes.
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