Monster Media 1996 #14/Monster Media No. 14 (April 1996) (Monster Media, Inc.).ISO/business/mixing10.zip/COMPFLOW.TXT

Text File | 1990-12-15 | 8KB | 185 lines

              C O M P R E S S I B L E   F L O W

GENERAL INSTRUCTIONS
The compressible flow program is designed to operate under
MSDOS and will work with all IBM and Compatible PC's.  The
files on the disk called COMPFLOW.EXE, SONIC.INP, and
SONIC.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 contains 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 .CFD are
example programs.  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 COMPFLOW.
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 problems saved 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, that shows the results of
the adiabatic flow for the saved case.  If you pressed R then
two screens will come on to permit you to enter the
information for the gas properties and pipe.

The COMPRESSIBLE FLOW  program uses function keys 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 required data for the gas properties and a description of
the pipe must be entered.  From the compressible flow results
screen, this information can be entered by pressing the F-10
key to input a new case.  The F-1 key will rerun the program
with new gas properties and the same pipe description.  The
F-2 key will rerun the problem with a revised pipe
description and the same gas properties.

GAS PROPERTIES INPUT
Input the required information fields, and press the return
key after each data entry.  You can simply press the return
key to accept the data suggesting by the computer.  You can
move between the data input fields by the use of the up or
down arrows on your key board.  After all the data is entered
the F-10 key is pressed to run the program.



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 other data that must be filled in are the gas flow rate
in Lb/H, molecular weight, viscosity, compressibility factor,
K ratio or Cp/Cv, and the temperature and pressure of the
source.  The program assumes these inlet conditions
correspond to a stagnant gas volume, such as within a vessel.

PIPE DATA SCREEN
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 are 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; 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.

The straight length and equivalent length for fittings must
be included.  The F-2 key will bring up a fittings menu to
develop the L/D ratios and equivalent feet for the fittings.

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 following options are available from the command line of
the main output screen by pressing the function keys.

F-1  Allows the gas input to be altered

F-2  Allows the pipe information to be altered

F-3  Will calculate the pressure drop of the pipe using the
gas properties at the source inlet.  This is an
incompressible flow solution.

F-4  Allows the flow rate of gas to be calculated through the
given pipe to meet a specified outlet pressure.  The outlet
pressure specified must be higher than the critical minimum
or sonic pressure at the outlet.



F-5  Will size the pipe diameter to meet a specified pressure
drop in PSI/100 ft.  standard pipe sizes are used up to 2 ft
diameter.

F-6  Will allow the type of pipe to be changed to rectangular
ducts or Annulus.

F-7  Not Used

F-8 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 CPF is automatically added to
the name by the program for data files.

F-9  Will print the problem results.  First press the F-9 key
and then press the return key when the printer is ready.
This can be aborted by pressing the ESC key.

F-10  Will erase the present problem and allow you to input a
new case.

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.

RESULTS SCREEN
The results screen gives the results of the compressible flow
problem for Isothermal and Adiabatic Flow.

The screen gives the internal diameter and total length of
the pipe plus the equivalent length of the fittings.

The Flow of the gas is given.

The temperature at the inlet of the pipe is given, as well as
at the outlet.  The temperature at the inlet for the
adiabatic flow case is lower than the source temperature
given on the gas input screen because it is adjusted for the
isentropic effects of the gas entering the pipe and
accelerating to the pipe inlet velocity.  The outlet
temperature of the gas for adiabatic flow is also reduced for
the energy lost to friction.

The density at the inlet and outlet conditions is given.

The velocity and Mach numbers are calculated for the inlet an
outlet conditions.  The Mach number is the velocity of the
gas divided by the speed of sound of the gas.

The Nre Reynold's number and friction factor used by the
program is given.

The Source pressure, the Inlet Pressure allowing for the
enterance effects, and the outlet pressure are given.

The critical pressure is given.  This is the pressure
corresponding to a Mach number of 1 for adiabatic flow and to
the point where the Mach number is equal to 1 / SQRT ( K )
for isothermal flow.

The critical temperature and density corresponding to the
above Mach number limits are given.

The Maximum length of pipe of the specified diameter is given
This is the length of pipe corresponding to the sonic
limitation for the gas.

The equations and methods used in this program are describe
in the Methods section.


Alchemy Systems is interested in your comments regarding the
use of this program and future enhancements that may be
desired.