Which are the different HiTrans v2 editions? Which are the differences between each edition?

HiTrans v2 is available in the following editions:

Which are the HiTrans v2.1 pipeline systems limitations?

Number of pipes and nodes
It depends on the HiTrans edition. HiTrans v2.1 Premium Edition limitation is systems composed for up to 100 pipes and 101 different nodes.

Scope, branching pipes and network modelling
HiTrans v2.1 is intended to solve main pipelines not branching pipes or networks. However the version v2.1 incorporates a new node control component which allows defining an incoming or out-coming flow rate in the nodes.

It is being developed the version v3 intended to solve branching pipelines and networks, and no limitations in the number of pipes and controls included in the model.

What is HiTrans?

HiTrans is a numerical modelling software to solve transient flows in pipeline systems (commonly known as water hammer). Water hammer is the name commonly given to the pressure fluctuations that develop in a pipe when the flow is suddenly changed. HiTrans models the transient flow solving the partial differential equations of movement by using the "method of characteristics" in one-dimensional systems.

With HiTrans V2.0 Premium Edition you can solve complex pipelines composed up to 100 different pipes and the following devices:

Valves

• Opening Valves
• Closing Valves
• Control Valves
• Pressure Relief Valves
• Fixed valves
• Check Valves

Tanks

• Constant Level Tanks
• Surge Tank
• One Way Surge Tank (Feed tanks)

And,

• Air Vessel (air chamber, surge alliviator)
• Pumps

HiTrans v2 includes 2 different estimators for unknown parameters, such as:

• Transient flow pressure wave speed
• Pump Inertia

To run HiTrans you just need to enter the system and these parameters

• Total simulation time
• Time Step
• Minimum number of intervals to be discretized the limiting pipe (normally the minimum number of division for the shortest pipe in the system)

HiTrans V2 internal algorithm will calculate all internal parameters to assure the solution's convergence and stability. For advanced users, is possible to see all internal calculations parameters.

HiTrans results includes:

Piezometric Head (m)

• Flow (m3/s); and
• Pressure (m, manometric)
• Summary results
• extreme values in each calculation point
• Animation: powerful tool to take a look about what is happening in your pipeline when the flow is changed
• Plots for any point, any magnitude against time
• Plots for certain nodes, any magnitude against time
• Numerical results also included: Piezometric Head (m), Flow (m3/s) and Pressure (m, manometric)
• Summary results: extreme values in each calculation point
• Detailed values for any point, any magnitude against time
• Detailed values for certain nodes, any magnitude against time
• All results can be exported to a text file to be used in spreadsheet software like MS Excel (*.csv format)

What's new in HiTrans v2.1?

I need more information about selecting an appropriate calculation step for using HiTrans

One of the most important parameter to get a successful modelling, is to select an appropriate time step. Selecting a time step for modelling is a compromise of a faster simulation, accuracy and an adequate representation for the processes involved in the system.

To run HiTrans it is required that user enters these parameters:

By default, HiTrans adopts for these parameters the values 19s, 0.1s and 1, respectively. Value 1 in this case indicates that the entered pipes will be divided at least in two sections (space calculation step, Dx equals the total pipe length /2). Note that the pipe of smaller length is the pipe with small calculation step in space.

Once the users entered the desired calculation parameters, HiTrans calculates (by an algorithm develop by Istec Ingenier�, a new time step to use for modelling. This new calculation time step is smaller that the desired time step, and is an internal value of HiTrans that assures the stability of the model for all pipes.

An important consequence of this procedure, is that usually, the time step to be used for calculation, is strongly influenced for the smallest space calculation step. As a result of that, if the user enters a large number of intervals for all pipes and there is a short pipe in the system, the calculation time step selected by HiTrans could be extremely small and the simulation will take a very long time.

HiTrans informs to the user the new value for the time step that will be used for calculations, the maximum number of intervals in which the limiting pipe will be divided, the total number of calculation intervals and the number of intervals in which results will be available to the user.

The parameter used by the HiTrans internal algorithm to select a time step suitable for calculation that assures the stability of the system, uses the pressure wave celerity in the pipes as a adjustment factor.

Then, the maximum error in the wave speed is also shown to the user.

This information allows advanced users to fit the entered calculation parameters until obtain an acceptable value in every one.

As a guide to the user: it is normal to admit a maximum error in the pressure wave celerity between 5 and 10%, since a small error in this wave speed normally does not strongly affect the modelling.

When I try to install HiTrans V2.1 the computer gives an error 1931 message windows.

When I try to install HiTrans V2.1 the computer gives an error 1931 message windows ("Error 1931: The Windows installer service cannot update the system file C:\.....dll because the file is protected by Windows. You may need to update your operating system for this program to work correctly.")

Error 1931 when installing HiTrans refers to a problem with "Microsoft Windows Installer 3.1" component of Widows 2000 and Windows XP installed in your computer. As a general rule, we advice to keep your windows operating system updated.

For more information about how to know which version of "Microsoft Windows Installer" is already installed in your PC and how to upgrade your "Microsoft Windows Installer" component visit http://support.microsoft.com/kb/898628/en-us.

Take in account that normally, if you press the "Ok" button in the error message the program will be installed correctly in your PC.

Cavitation and column break

When liquid pressure is reducing and vapour pressure is reached, the media will change its physical phase, from liquid to vapour, developing what is known as "cavitation". When cavitation appears on pipelines, the presence of vapour causes a discontinuity of the liquid media, normally called "column break". After this point, theoretical basis are not longer valid.

Once vapour pressure is reached, HiTrans simulation is paused automatically and it shows to the user a warning message with the time and location of the first point where cavitation develops.

When this point is reached in the numerical modeling, HiTrans results are not longer valid and are just a (sometimes useful) numerical presentation. When this message is displayed, HiTrans continue the numerical modelling up to final simulation time. This is done just to give the user an idea about how far results are from cavitation and where are the problematic points. This is why is possible to obtain HiTrans results without physical meaning, because pressure is lower than vapour pressure (for water at 20?C is possible to obtain pressure results lower than -10m).

From an engineering point of view this is not an important limitation in modeling since pipeline systems are normally designed to avoid cavitation (to eliminate the risk of high pressure pulses that develops when pressure raises again and physical phases change again) by using several control devices (surge tanks, air vessel, etc.).

A further concept is that vapour phase modeling 'state of the art' is not very accurate in all situations, and then in most cases the result than can be obtained must be regarded as an 'order of magnitude' value.

Then, we support the idea that modeling the liquid phase of the flow is not an important limitation in HiTrans to be used as a tool for engineering design.