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Flownex Blog

Flownex Simulation Environment - The Blog

Recent blog posts

How to model and analyze a natural gas combustion process using Flownex

 

By creating compound components for the specification and analysis of gas compositions and by wrapping the Flownex® Adiabatic Flame model and some associated scripts in another compound component, Flownex® may be used to perform extremely powerful combustion modeling in a very simple and efficient manner.

In the following case study, it has been shown that the results obtained are accurate and in close agreement with other available software. This extension enables Flownex® to be utilized as a complete heat and mass balance tool whilst simultaneously performing as a fluid dynamics, thermodynamics and heat transfer tool in this industry. The capability of extending the capabilities of Flownex® for any particular task through simple compound components sets Flownex® apart from other tools in the industry.

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Mine Explosion Modeling


The modeling of mine shaft explosions can successfully be executed using Flownex SE. This gives a fast and accurate systems level approach whereby engineers and managers are equipped to determine safe evacuation distances from the blast, as well as sufficient clearing time to allow ventilation of poisonous ANFO gases. This ensures that safety is respected as it should be, engineering time is minimized, and operation time is optimally utilized.

Powerful Flownex features like distance and time wise graphs are utilized to show the pressure wave propagation and Ammonia gas concentration distribution throughout the tunneling system in a visual pleasing way. Another excellent way to visualize the pressure wave propagation and Ammonia gas concentration distribution is through implementing Flownex’s colored result mask (result layers) functionality. This allows a color map of any fluid property over the mining system, making it easy to see what time frame is required to allow sufficient ventilation, and at what positions dangerous pressure forces will be experienced.

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Code-to-code comparison for analysing the steady-state heat transfer and natural circulation in an air-cooled RCCS using GAMMA+ and Flownex

The following article “Code-to-code comparison for analysing the steady-state heat transfer and natural circulation in an air-cooled RCCS using GAMMA+ and Flownex” describes how Flownex and GAMMA+ were both used in the analyses of the air-cooled RCCS system.

The abstract of the article is given below and the article can also be viewed by clicking on the link provided.

Abstract

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Pipe Stress Analysis with Flownex and ROHR2


One of the many applications of Flownex is to perform water hammer and pressure wave simulations. During these analysis Flownex has the ability to calculate the forces on the different components in the system. The calculated forces can be reported via the reporting mechanism and thereafter these forces can then be used as part of a pipe stress analysis simulation in pipe stress software.

 

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Superman, safety and fire protection system modelling

We all know Clark Kent. He is that shy, awkward guy that nobody notices, but when there is an emergency, then he is the guy that apparently flees, but comes to the rescue as Superman. It is the same with fire protection systems. You might see the sprinklers and fire houses around the workplace as an eyesore but one is incredibly grateful for them as soon as there is a fire hazard.

Fire protection systems are installed in power stations, petrochemical plants, warehouses and shopping centres to extinguish or suppress a fire. When it comes to the fire protection systems, it is essential that everything must work because of the combustibles positioned all around a plant. These combustibles can so easily ignite causing tremendous damage.

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Flownex backtracker functionality

Transient analysis for large networks and/or long time span simulations can be time consuming for the user. These simulations may have long waiting periods in which little happens. However, at a certain point in time, an event such as a pump start-up or valve closing event may be triggered which have an influential impact on the simulation results. To enable the user to replicate the event afterwards, an automatic snap functionally was created called the “Backtracker”.

In a recent project the “Backtracker” functionality was used to help develop the control philosophy for a Gas Drainage Plant (GDP) for an international coal mining company. The GDP is used to extract gas from an underground coal mine which in turn is used to generate electricity. The GDP control philosophy is required to minimise flaring or venting of the gas, thereby increasing electricity generation output.

The plant and proposed control philosophies was simulated using Flownex. As part of the project deliverables, the control set points and constants needed to be determined. The “Backtracker” functionality was used to obtain a number of snaps throughout the transiently simulated scenarios as defined by the client. In the event that improper control set points and constants caused unwanted behaviour at some point in the simulation, the engineer could select and reload a snap generated by the “Backtracker” at a time before the unwanted behaviour occurred. Using this snap as a starting point, the control set points and constants could be changed and the simulation rerun from that point without having to restart the simulation from the beginning. This saved a lot of simulation time. A picture of the network, controllers and the “Backtracker” window is shown.

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Container Interface component project application

Flownex’s newly developed Container Interface component has simplified and sped up the analyses of an existing prototype energy recovery plant. The prototype energy recovery plant forms part of a development phase for developing an energy recovery plant for a project in Chile. The client requested M-Tech Industrial to analyse their prototype energy recovery plant with the emphasis on certain thermo hydraulic phenomena occurring at higher operating pressures, which did not occur at the lower operating pressure envelope.

 

The proposed energy recovery plant will convert high pressure slurry (due to gravity feed) into high pressure water which in turn will be used to generate electricity. The energy recovery unit utilises vessels with a movable interface, separating the vessel into two variable volumes. By means of controlling the flow of slurry and water to the vessel, energy from the high pressure slurry is transferred to the water via the movable interface, allowing high energy transfer efficiency with minimal wear.

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Modelling moving membranes with new Container Interface components

Two new components were added to the Containers library in Flownex 2014 (Update 2), being the "Container Interface Top" and "Container Interface Bottom". These containers always operate in pairs, much similar to the heat-exchanger primary and secondary sides. The container pair essentially enables the user to model moving boundaries (dynamic varying volumes) in containers where two fluids streams are mechanically coupled through a force balance over a moving membrane. Any fluid type (liquid, gas or two-phase) can be specified on either side. These components are useful for modelling any volume displacement process between two fluid streams, for example pumping systems and energy recovery systems. Other typical applications include components such as valve actuators, hydraulic cylinders and accumulators.

 

During transient simulations the membrane position is tracked and the pressure in the two containers coupled through the force balance. When the membrane position reaches either end the force coupling is removed automatically, and both containers operate independently. When system parameters changes allowing movement of the membrane again, Flownex automatically activates the force coupling again. As an example, consider the hydraulic cylinder system shown:

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Excel Integration/Component - Some Useful New Features


The Excel component provides an easy way to integrate excel calculations into any simulation. It is also used a lot for pre and post processing, as well as a front end input sheet. In the new release drag and drop onto the Excel sheet of the Excel component has been added to make the setting up of inputs, outputs and links quicker. This as well as some other nice features are discussed in the video below.

 

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Excel Reporting - Now Even Easier


 

Reporting is an important part of the simulation process. Flownex have always supported reporting to Excel, but the reporting has been made more intuitive and easy to use for our upcoming release. Here is a video that shows how easy to use and powerful it is.

Tagged in: Excel Flownex Reporting
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Flownex - Fluent Server link


 

Using FlownexSE its very simple to create links to other software. With input from our partners at Leap Australia we created an easy to use and efficient link to Co-Simulate with Fluent. The link allows you to transfer any input or result from Flownex to any parameter or rpvar in Fluent. The video shows an example where a unknown flow component in Fluent is modelled as a resistance in a Flownex system.

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Deep mine ventilation - Where did all the cooling go?

The active mining depths in the South African gold mines can range between 2 and 4km. The rock wall temperatures at these depths increases the ventilation air to temperatures higher than that what a worker can cope with for a working shift. This necessitates the cooling of the ventilation air to the required wet bulb temperature of 25-30°C.

The cooling of ventilation air can be done with bulk air coolers (usually situated at the ventilation shaft on the surface or at a station underground) and cooling cars (usually situated in the haulages and cross cuts). For a blog regarding the modelling of a cooling car, see Thermal modelling of an underground mine cooling car.

The main services used to cool the working environment is ventilation air and chilled water (some mines also use ice which is added to the underground dams). The energy going to the mining places is transported with different streams and an integrated services model will be the best tool to track the amount throughout the mine.

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Modelling Tips: Sizing a Pump in Flownex®

In order to model a pump in Flownex®, the pump curve needs to be specified. If the pump curve is not available, a pump curve can easily be created by specifying the desired mass flow as a fixed mass flow rate and then using the volume flow rate and pressure rise results to create the pump curve. The fixed mass flow rate can be specified for the pump or another element, such as the flow resistance element or a pipe. In this example, a pump was used, as seen in the figure below:

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When a fixed mass flow is specified, Flownex® will fix the mass flow rate through the specific element to the value specified, regardless of the conditions that were specified for the element. This means that irrespective of the pump curve specified for the pump in this example, the mass flow rate will be equal to the specified fixed mass flow rate, which in this case is 23.8 kg/s.

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Dynamic force calculations for support structures with water hammer


The modelling capabilities in Flownex® can be used to analyse a pipeline for water hammer effects. The results can be used to implement mitigation methods to reduce the sudden increase in forces and prevent pipe rupture. These mitigation methods can also be analysed and compared in Flownex®.

Water hammer can occur after a pump trip or when a valve closes. For design cases we are especially interested in the first pressure spike. Flownex® has the built-in functionality to calculate the force on a pipe and at a bend because it provides the pressure and flow (velocity) field as an result.

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Important aspects to remember when modelling water hammer in Flownex

Flownex is an excellent tool to model water hammer and can be used to determine pressure pulse peaks, frequency, damping and helps to give an indication of when flashing can occur.  

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When modelling water hammer in Flownex, the following key aspects should be considered during the modelling approach.

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Steam Plant Analysis

Flownex’s new steam turbine component and shell side condensation heat transfer capability proved to be very useful in analysing the integrated performance of a waste heat recovery plant.

In a recent study, a client requested M-Tech Industrial to analyse the performance of their steam turbine and auxiliary plant which is used to generated electricity.  Off-gas produced during a manufacturing process is either used to generate steam in a Boiler or flared to atmosphere. The steam generated is used in a number of processes which include an electricity generation facility comprising of two turbo-generator sets. Induced draft wet cooling towers are used to reject the condenser heat to atmosphere.

The client is currently refurbishing the plant. The rated plant capacity is 10 MW per unit, which at the time of refurbishment was only achieving 8 MW per unit. High summer humidity conditions was initially thought to be the main reason for the high cooling water temperatures resulting in high condenser pressures which reduces the turbine’s generation capacity. M-Tech industrial was tasked to analyse the plant to determine the root cause resulting in the under performance as well as to propose a solution to improve plant performance.

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How new components are developed in Flownex

In this context a “component” is an element or block on the software GUI that represents a physical piece of equipment such as a pump, a heat exchanger, an electrical motor or a PID controller. In Flownex, they are all listed in the Library as in the figure below.

 

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Flownex 2014 Release

Flownex Release 2014

Where complexity & accuracy meet ease of use

 
28 years ago Flownex was brought to life by Professor Gideon Greywenstein, he had a vision to produce a tool that would create extraordinary value through engineering excellence. Flownex has ever since strived to keep his words true, and 2014 is a year that will resonate his vision.
It is unbelievable what we have achieved in the last 12 months; our approach of working closely with our clients and industry professionals to enhance Flownex’s capabilities has once again proven itself and allowed us to deliver a product that is well aligned to the ground-breaking advances our users are achieving…Tiaan Dercksen – Principal, Software Development

The major enhancements of Flownex 2014

Gas turbine secondary flow modelling

Flownex 2014 enables users to apply the unparalleled stability, solution speed and accuracy to detailed modelling of secondary flow in gas turbines. The key features include Swirl solver, rotating cavities, vortices, seals and rotating channel modelling.

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Flownex SE at ASME Turbo Expo 2014

The ASME Turbo Expo is an annual event in the gas turbine industry where industry leaders and researchers present papers in numerous technical sessions on gas turbine simulation, design and manufacturing. This year the Expo is being held in Dusseldorf, Germany the week of June 16 - June 20.

Flownex is used in the gas turbine industry for the modelling of gas turbine cycles and sub-systems, perform power matching and model heat transfer and flow distribution in gas turbine combustors. The upcoming 2014 Flownex release boasts a comprehensive secondary flow component library for the modelling of the bleed air system between compressor extraction and turbine blade/disc outlet, where it is usually applied for film cooling purposes. New components include a free and forced vortex, rotor-stator and rotor-rotor cavities, rotating nozzles as well as swirl boundary conditions. This new capability is being demonstrated at our Flownex booth (405) in the Exposition Hall. All existing clients and interested parties are invited to join us.

Below is a photo of our booth.

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Flownex training in South Korea

I had the opportunity to train some of our new Flownex clients in South Korea during April this year. I really enjoyed it to taste the different types of food available and to experience the culture.

 

The training was done over four days - two day basic training and two days advanced training. Below is a picture of the group during one of the training sessions.

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