INTRODUCTION:
PIPENET VISION Standard module is a tool for steady state flow modelling of networks of pipes and ducts. It can model incompressible and compressible flow networks. It is widely used for modelling ventilation systems in the nuclear and other industries. Such calculations are central to the design process in some industries because good design of ventilation systems is essential for safety.
We consider three examples in this section of the document.
· A simple extract system
· Balancing a system which has fans on the inlet and extract sides of the system
The first of the above examples will be covered in more detail with several examples of dialog boxes. The other example is equally important but have fewer dialog boxes in order to avoid repetition.
2. EXAMPLE 1:
The first example we look at is an extract system of the type you might get in a machine shop. The objective of the exercise is to take a system which has been manually designed; all the duct sizes and fan curve are known. We wish to verify that the system would work as required. The network as it is drawn in PIPENET is shown below.
The system with the duct labels is shown below:
2.1. Setting Up and Running the Problem
In this part of the training manual we will see how to set up this problem and run it. This example shows all the dialog boxes which are used in setting up the example.
2.1.1. Initialisation:
This is done by using the pull down menu ‘Options’.
Enter title:
Standard Options:
Select Colebrook-White equation as per Perry Formula for friction factor option and select proceed with calculation for warning controls.
Warnings control – PIPENET produces two types of diagnostic, namely, warnings and errors. Warnings are generally for information only. The user should check the input data and make sure that there is not mistake in the input. It may not stop a calculation from proceeding to successful completion. This switch instructs PIPENET to treat warnings as errors or proceed with calculation.
Node elevation – Elevation changes are taken into account by PIPENET. The default option used by PIPENET is pipe elevation – this is the difference between the elevation of the input and output nodes of a pipe. It is positive of the output node is higher than the input node, and is negative if the output node is lower than the input node. If node elevation is switched on then PIPENET expects the user to specify the elevations of all nodes with respect to a datum.
Use Colebrook-White equation as per Perry – The representation of the Moody diagram by the Colebrook equation is slightly different between different sources. This switch uses the form quoted in Perry’s Chemical Engineers Handbook. The Darcy option refers to the friction factor calculation as per the book by Coulson and Richardson. They are both methods of representing the Moody diagram and the basic format of the friction factor equations are the same.
Units:
The first step in most engineering calculations is to choose the units one wishes to work in. This is done by clicking on Init/Units and is shown in the following screen.
Length
m
Diameter
mm
Velocity
m/s
Temperature
Celcius
Viscosity
Pa.s
Pressure
In water gauge
Density
kg/m3
Flowrate
Ft3/min
Fluid:
We wish to use air at 15 Deg C and this is done by entering data in the following manner.
http://www.cadfamily.com/html/Article/Ventilation%20System%20Modeling%202-Part%20A_665_1.htm
http://www.cadfamily.com/html/Article/Ventilation%20System%20Modeling%202-Part%20A_665_2.htm
http://www.cadfamily.com/html/Article/Ventilation%20System%20Modeling%202-Part%20A_665_3.htm
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