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Monster Media 1996 #14
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Monster Media No. 14 (April 1996) (Monster Media, Inc.).ISO
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mixing10.zip
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TWOPHINS.TXT
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1990-05-20
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T W O P H A S E F L O W
GENERAL INSTRUCTIONS
The two phase flow program is designed to operate under MSDOS
and will work with all IBM and Compatible PC's. The files on
the disk called TWOPHASE.EXE, TWOPHASE.INP, and TWOPHASE.PIC
work together and should be transferred to the same sub-
directory of your Hard Disk. They are all part of the
program. The .PIC file contain the screens used by the
program, and the .INP file contains information for the
screen generator. The .EXE file contains the program logic.
The other files on the disk with the extension .TPH are
example program. When you save a file it will be saved with
this extension. The program is not copy protected, and can
be installed onto your hard disk in the normal manner by
copying all the files onto a sub directory of the hard disk.
The program can be started by inserting the program disk into
the A drive and giving the name of the program TWOPHASE.
The title screen will come up and you will be asked if you
wish to load an existing file or run a new problem. Input L
to load a file or R to run a new case. If you select L then
the two phase problems save on the disk will be shown on the
screen. You can pick one by moving the cursor to the desired
file and pressing the return key. The file will be loaded
and the Main operating screen will come up. If you pressed R
then this screen will come up with no input information
loaded.
The TWO PHASE program uses function key with a command line
prompt, and input windows. The system is very user friendly
and you will probably not require the use of these
instructions to use the program.
PROGRAM OPERATION
The Two phase program input screen will be the normal
operating environment for the program. You should start to
operate by filling in the required information to size the
lines.
The first field is the title for the problem. You can use
this field to identify the line by filling in the line number
or case description.
The pipe schedule can be selected by pressing the F2 key. The
default schedule is Schedule 40 CS. If you press the F2 key
a window will come up giving other choices. The schedule key
allows you to automatically give the true internal diameter
and pipe roughness for different standard pipes. These
values can be over ridden by the main input screen if non-
standard pipe is being used.
Input the Nominal diameter in inches and the internal
diameter and pipe roughness is calculated and is shown on the
screen. The program will go to these fields so that you can
override the values, if desired. To accept the computer
generated values then press the return key. The Arrow keys
that control the cursor will also move the cursor to various
fields to permit selected input on desired fields. However,
the return key must be pressed to input a new value.
After the pipe information has been given, the data must be
inputted to describe the fluids flowing through the pipe.
The Liquid information is filled in first. Give the liquid
flow rate in Lb/H, The Liquid Density in Lb/Ft3. The Liquid
Viscosity in Centipoise, and the liquid Surface Tension in
Dyne/Cm. Hydrocarbon systems have surface tension values of
approximately 10 or less, Water has a surface tension of
approximately 35.
The Vapor flow information is filled in next. Give the flow
rate in Lb/H, The vapor density in Lb/Ft3, and the Vapor
Viscosity in centipoise. The vapor density can be calculated
for the pipe conditions by pressing the F4 key. A window
will come up that asks for the pressure in Psia, temperature
in F, the MW of the gas and the Z or compressibility data.
Fill out this information and press the F10 key and the vapor
density will be calculated. For isothermal flow problems
where critical flow is not exceeded, the average pressure
between the inlet and outlet pressures can be used to give a
accurate result. This may be a trial and error procedure
that is made easily with this program.
When all data is filled in, the program can be run by
pressing the F10 key. If you do not press the F10 key then
the input cursor will return to the first input field, the
Case description and you can change the data.
When the F10 key is pressed the program calculates the flow
regime of the system by using the Baker Chart method. The
program give the Baker chart coordinates X and Y as well as
the flow regime. This data is described in the Methodology
section of these instructions.
The Lockhart and Martinelli method is used to calculate the
two phase pressure drop, and is explained in the Methodology
section. The method is based on a correlation of two phase
pressure drop from the pressure drops and flow regimes of the
liquid and vapor as if they were flowing independently
through the pipe. Consequently the program calculates and
presents the velocity, Reynolds Numbers, Friction Factors and
PSI/100 feet for both the liquid and vapor phases. The
Martinelli X^2 and Omega^2 are also presented. The two phase
pressure drop is usually considerably higher than either the
liquid or vapor phase pressure drop.
The total line pressure drop can be calculated by hand by
multiplying the pressure drop for two phase flow in Psi/100
ft by the total equivalent feet of the pipe system. This is
the straight length of pipe plus the pressure drop consumed
by fittings and bends ect. The effect of static head must
also be calculated for vertical pipe rises. The equivalent
feet of fitting, bends ect. is calculated by pressing the F3
key. A window will come up that allows you to enter the
fitting description, When all the data is inputted then
press the F10 key to calculate the total equivalent feet for
the pipe diameter used in the Main Screen.
For homogeneous flow regimes the hydrostatic head can be
calculated by pressing the F5 key. This screen will also
calculate criteria for erosion. The methodology section
reviews these procedures. When calculating static head
considerations for two phase flow, consider only the sum of
the vertical rises. Do not deduct for descending flow since
you do not get a reduction in the pressured drop for downflow
with two phase systems.
The F9 key will print a report of the two phase program to
your printer. First press F9 and then press the return key
when your printer is ready.
The F8 key will save the problem to disk for future work.
Press F8 and then F1 to save the file or F2 to load a new
file from the disk. The program will prompt you through the
disk operations from the command line. When saving a file
you should give an eight letter name, but do not include a
period or extension. The extension TPH is automatically
added to the name by the program for data files.
Press the ALT key and the Q key to quit the program. The
command line will ask if you really want to quit. Answer
with the Y key to exit.
PROGRAM LIMITATION
The program will be accurate for conventional two phase flow
process flow problems. It is not accurate for critical flow
and if the vapor velocity exceeds 300 ft per second then
alternative methods based upon equations of state are
required.
Alchemy Systems is interested in your comments regarding the
use of this program and future enhancements that may be
desired.