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SF-Pressure Drop 3.0 für Windows 95

(c)  01.1997

Norbert Schmitz

Am Moenchhof 7a

D-67105 Schifferstadt

Germany

Phone/Fax: 0049 6235 / 82187

E-Mail: 101515.407@compuserve.com

General

Technical information

Quick instruction

Buttons

Menue File

Menue Edit

Menue Table

Menue Flow Medium

Menue Calculate

Menue Extras

Bibliography

Liability/Copyright


Allgemeines
General

Please excuse my terrible english, I hope you will understand my explanation.

SF-Pressure Drop Version 3.0 for Windows 95 calculates the pressure drops (caused by friction) of flowing liquids and gases in pipes.

Additionally you can calculate pressure drops caused by vertical difference of the pipe.

SF-Pressure Drop calculates also pressure drops caused by pipe elements (example: changes of direction) and diverse valves.

It's able to combine diverse elements and so to calculate the total pressure drop.

It's able to copy the whole calculating table to a spreadsheet .

SF-Pressure Drop calculates pressure drops of laminar and turbulent flows. But it's only possible to calculate pressure drops of newton-liquids berechnet werden.

To calculate the pressure drop you need data of pipes (rougness) and data of flow medium (density, viscosity). These data are available in a database.

Your own data you can save in a user-defined database.

Additionally are the following futures:

- Calculation of pressure drop dependent on rate of flow   (showing and printing of the characteristic curve)

- Calculation of a economic pipe-diameter at a known rate of flow

- Calculation of a minimum head of a pump at a known pressure drop

- Conversion of rate of flow to velocity and inverse at a known pipe diameter

- Conversion of diverse units

You can save and open SF-Pressure Drop project-files.

.


Fachliche Information
Technical Information

Pressure drop:

Pressure drop in pipes is caused by:

1.) Friction

2.) Vertical pipe difference

Calculation of pressure drop caused by friction in round pipes:

First we calculate the Reynolds Number:

(Nomenclature)

If the Reynolds number < 2320, than we have laminar flow. Is the Reynolds number > 2320, so we have turbulent flow.

Now we calculate the pipe friction number berechnet:

Pipe friction number at laminar flow:

(Nomenclature)

Pipe friction number at turbulent flow (in the most cases):

(Nomenclature)

Now we can calculate the pressure drop in round pipes:

(Nomenclature)

If we have valves than we calculate the pressure drop with resistance coefficients berechnet. The resistance coefficients are in the most cases found through practical tests. If the resistance coefficient is known, than we calculate the pressure drop:

(Nomenclature)

The pressure drop caused by vertical pipe difference we calculate so:

(Nomenclature)

Pressure drop of gases and vapor

Compressible fluids expands caused by pressure drops (friction) and the velocity will increase. Therefore is the pressure drop along the pipe not constant.

(Nomenclature)

We set the pipe friction number as a constant and calculate it with the input-data. The temperature, which is used in the equation, is the average of entrance and exit of pipe.

You can gases calculate as liquids, if the relative change of density is low (change of density/density = 0,02)..


Kurzanleitung
Quick instruction

1.) Choose the menue "Calculate/Select pipe element" oder press the button [image] und choose the element to calculate, example: Pipe entrance/sharp edged entrance.

2.) In the window "Element of pipe" do insert the data, example: Diameter of pipe D in mm: 50. Edit the quantity of elements.

3.) In the window "Flow medium" do insert the data, example:

Flow medium: Acetone

Rate of flow V in m^3/h: 200

Weight density in kg/m^3: 765

Absolute viscosity in 10^-6 kg/m s: 269

Also you can choose the menue "Flow medium" or press one of the buttons [image] [image] [image] [image] [image] [image]. Data, which you choose in the database, you can copy in the window "Flow medium".

4.) Choose the menue "Calculate/Pressure drop" or press the button [image].

5.) SF Pressure drop calculates now the pressure drop and shows the results in the table below.

6.) Now you can choose other elements and calculate pressure drops of its. The total pressure drop you can find at the bottom of the table.

After calculation you can save the project-file: Choose the menue "File/Save project" or press the button [image].

You can also the table print: Choose the menue "Table/Print table" or press the button [image].

You can gases calculate as liquids, if the relative change of density is low (change of density/density = 0,02)..


Menü Datei
Menue File

Menue "New project"

Opens a new table for the calculating results.

Menue "Open project"

You can open a saved calculation table, look also button  [image].

Menue "Save project"

You can save a table, look also button [image].

Menue "Save project as"

You can save a table with a new name. The extension of the file is DRU.

Menue "Exit"

Close SF-Pressure Drop..


Menü Bearbeiten
Menue Edit

Menue "Copy"

You can copy data of edit-fields into the clipboard.

Menue "Paste"

You can copy data of the clipboard into the edit-fields.

Menue "Delete"

You can delete data of edit-fields..


Menü Tabelle
Menue Table

Menue "Print table"

You can print your calculation table, you can also press the button [image]. The table will print with the actual font.

Menue "Change font"

You can change the font of the table, you can also press the button [image].

Menue "Zoom in"

You can zoom in the table, you can also press the button [image], factor ca. 1,2.

Menue "Zoom out"

You can zoom out the table, you can also press the button [image], factor ca. 1,2.

Menue "Change column width"

You can change the column width of the table, you can also press the button [image].

Menue "Delete select column"

You can delete the select column, you can also press the button [image].

Menue "Copy to Clipboard"

The whole calculating table will copy to the clipboard, you can also press the button [image]. You can insert this table to your spreadsheet  program.

Menüpunkt "Copy to edit-windows"

You can copy the contents of the select column to the edit-windows. You can also press the button [image]. .


Menü Fördermedium
Menue Flow medium

Menüpunkte "Properties...."

You open the databases of properties of flow medium. To calculate the pressure drop you need data of flow medium: Density and Viscosity. In these databases you found many properties.

Additonally you can choose a user-defined database, in which you can insert your own properties (look at Menue "User-defined database edit").

Also you can open the databases by pressing the buttons [image] [image] [image] [image] [image] [image].

You can copy the data in the window "Flow medium".

Menüpunkt "User-defined database edit"

Here you can save your own properties of flow medium. The data are saved in the file USER.DAT.


Menü Berechnen
Menue Calculate

Menue "Pressure drop"

You can calculate the pressure drop. Before you have to choose the pipe element and fill in the fields in the window Element of pipe and Flow medium. The results you find in the calculation tabel.

Menue "Select pipe element"

You can select the pipe element, also you can press the button [image].

Menue "Economic diameter of pipe"

You can calculate the economic diameter of pipe at a known rate of flow. The pipe diameter of liquids will show at a small viscosity and at a hight viscosity, of gases at small and hight pressure.

This calculation is only for round pipes.

Menue "Head"

After you have calculate a pressure drop perhaps you need a pump to compensate this pressure drop. For the selection of this pump you need the rate of flow and the head. Here you can calculate the minimum head of this pump.

Menue "Velocity to rate of flow"

You can calculate at a known velocity and a known pipe diameter the rate of flow.

This calculation is only for circular pipes.

Menue "Rate of flow to velocity"

You can calculate at a known rate of flow and a known pipe diameter the velocity of your flow medium.

This calculation is only for circular pipes.

Menue "Pressure drop = f (Rate of flow)"

You can calculate the pressure drop of one or more pipe elements as a function of rate of flow:

1.) Calculate the pressure drop of your pipe element(s) at any rate of flow. The used ements should be matched (example: same diameter). SF-Pressure drop is not able to check it.

The calculations of the elements are now in the table and will read out of SF-Pressure drop to calculate the characteristic curve.

2.) You should control the correctness of the data in the window Flow medium. Now you can select the Menue "Pressure drop = f (Rate of flow)".


Menü Extras
Menue Extras

Menue "Convert data"

You can convert some units of rate of flow and viscosity, also you can convert the kinematic viscosity to absolute viscosity..


Haftung/Copyright
Liability/Copyright

SF-Pressure drop was produced carefully. But no computer software is without bugs. Therefore the calculations are your own risk.

You are not allowed to modify this software.


Laminare Strömung
Laminar flow

Laminar flow is characterized by the gliding of concentric cylindrical layers past one another in orderly fashion. The volocity of the fluid is at its maximum at the pipe axis and decreases sharply to zero at the wall. The pressure drop caused by friction of laminar flow does not depend of the roughness of pipe.

Look also Turbulent flow


Turbulente Strömung
Turbulent flow

There is an irregular motion of fluid particles in directions transverse to the direction of the main flow. The velocity distribution of  turbulent flow is more uniform across the pipe diameter than in laminar flow.

The pressure drop caused by friction of turbulent flow depends on the roughness of pipe.

Look also Laminar flow


Newtonsche Flüssigkeit
Newtons fluid

The absolute viscosity of a newtons fluid depends only on temperature and pressure. The most fluids are newtons fluids.

.


Reynolds-Zahl
Reynolds number

The Reynolds number shows whether a flow is turbulent or laminar. It is a numerical value of a dimensionsless combination of pipe diameter, density, viscosity and velocity of fluid.

(Nomenclature)


Rohrreibungszahl
Pipe friction number

The pipe friction number is a dimensionsless number. The friction factor for laminar flow conditions is a function of Reynolds number only, for turbulent flow it is also a function of the character of the pipe wall.

Pipe friction number for laminar flow (circular pipes):

Pipe friction number at turbulent flow(circular pipes):

(Nomenclature)


Zeta-Wert
Resistance coefficient

The resistance coefficient is a number to calculate the pressure drop of valves or fittings. It is determined by practical tests.

Is the resisistance coefficient known than you can calculate the pressure drop:

(Nomenclature)


Rauhigkeitswert
Roughness

The (absolute) roughness of a pipe is the effective height of pipe wall irregularieties in mm.


Formelzeichen
Nomenclature


Dichte
Weight density

The weight density or specific weight of a fluid is its weight per unit volume. This is expressed in kg/m³.  The weight density is a function of temperature and pressure.  The effect of pressure on the weight of liquids is of no practical importance of flow problems.


Förderhöhe
Head

Head of a pump:

(Nomenclature)


Geodätische Höhe
Vertical difference

The vertical difference means:


Viskosität
Viscosity

The viskosity or absolute viscosity expresses the readiness with which a fluid flows when it is acted upon by an external force. The absolute viscosity of a fluid is a measure of its resistance to internal deformation or shear.

The kinematic viscosity is the ratio of the absolute viscosity to the mass density:

(Nomenclature)


Volumenstrom
Rate of flow

The rate of flow is a function of volume and time:

(Nomenclature)


Strömungsgeschwindigkeit
Velocity of flow

The velocity of flow is a function of rate of flow and the cross section of the pipe:

(Nomenclature)


Schaltflächen
Buttons

Window "Flow medium"

 This button opens the database "Properties of water". Look also Menue "Flow medium/Properties of water"

 This button opens the database "Properties of other fluids". Look also Menue "Flow medium/Properties of other fluids"

 This button opens the database "Properties of air". Look also Menue "Flow medium/Properties of air"

 This button opens the database "Properties of Saturated steam". Look also Menue "Flow medium/Properties of Saturated stem"

 This button opens the database "Properties of other gases". Look also Menue "Flow medium/Properties of other gases"

 This button opens the user-defined database of properties. Look also Menue "Flow medium/User-defined database"

Window "Element of pipe"

 You can calculate the pressure drop. Before you have to choose the pipe element and fill in the fields in the window Element of pipe and Flow medium. The results you find in the calculation tabel. Look also Menue "Calculate/Pressure drop"

 You can select the pipe element. Look also Menue "Calculate/Select pipe element"

Table

 This button prints the table. Look also Menue "Table/Print table"

 You can change the font of the table. Look also Menue "Table/Change font"

 This button zooms in the table (Factor ca. 1,2). Look also Menue "Table/Zoom in"

 This button zooms out the table (Factor ca. 1,2). Look also Menue "Table/Zoom out"

 This button changes the column width of the table. Look also Menue "Table/Change column width"

 This button deletes the select column. Look also Menue "Table/Delete select column"

 This button opens a saved calculation table. Look also Menue "File/Open Project"

 This button saves a table. Look also Menue "File/Save Project"

  The whole calculating table will copy to the clipboard. You can insert this table to your spreadsheet  program. Look also Menue "Table/Copy to clipboard"

 This button copies the contents of the select column to the edit-windows. Look also  Menue "Table/Copy to edit-windows"


Literaturquellen
Bibliography

Bohl - Technische Strömungslehre

Dubbel - Taschenbuch für den Maschinenbau

Hütte - Grundlagen der Ingenieurwissenschaften

Recknagel - Taschenbuch für Heizung und Klimatechnik

VDI - Wärmeatlas

Wagner - Praktische Strömungstechnik