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AFT Blog

Welcome to the Applied Flow Technology Blog.
Ben Keiser

Sonic Choking: Flow Areas vs. Sonic Areas

AFT Arrow can be used to model various types of choking such as restriction choking, endpoint choking, and expansion choking.  A useful parameter in AFT Arrow’s output is the “Sonic Flow Area” and this is the flow area in which sonic choking will occur.  Comparing the sonic flow area to the actual flow area can help determine the margin between not choking and choking. The figure below provides a conceptual understanding of comparing various sonic areas to the actual flow area of a compressible system.  If one defines their system such that the sonic area (ASonic,1) is less than the flow...
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Recent Comments
Guest — Bogdan
Ben, How do you obtain the CdA value (minimum possible flow area)?
Friday, 01 January 2016 00:27
Ben Keiser
Hi Bogdan, The CdA value is essentially an effective flow area and it can typically be somewhere between 90-95% of the orifice ar... Read More
Monday, 04 January 2016 17:26
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Trey Walters

Where Did the Name "Arrow" Come From?

A frequently asked question at our training seminars - usually during a break or over lunch - is how we came up with the name "Arrow". More completely, the product is named AFT Arrow™ and it is considered by many as the world's leading compressible pipe flow modeling software product. There is a similar story behind the naming of AFT Fathom™ and I told that story several months ago in my post entitled Where did the Name Fathom Come From? The story behind the Arrow name is rooted in the beginnings of Applied Flow Technology as a company. So let's go back to...
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Applied Flow Technology

Automatic Renumbering

All of the pipe numbers in Fathom must be unique. When adding a pipe to a model, the new pipe number will be incremented based on the highest pipe number currently in the model. For example, you may only have 25 pipes on the workspace, but if the highest pipe number is 100, a new pipe will automatically be assigned number 101. After several iterations of deleting and adding new pipes, the numbering scheme may be reduced to chaos. AFT Fathom provides three tools to quickly and easily renumber pipes. They can be found in the Edit menu.   The Renumbering...
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Trey Walters

May the Force Be With You: Evaluating Unbalanced Forces Caused by Waterhammer

A common task among pipe stress engineers is to evaluate loads on pipe systems caused by waterhammer. Since AFT Impulse 4.0 was released our users have had the ability to calculate waterhammer-induced unbalanced forces for use in any pipe stress analysis application. In addition, our users can create specially formatted transfer files for direct use in CAESAR II and TRIFLEX. However, the process of calculating such forces in AFT Impulse and then applying them in pipe stress software is not as straightforward as it sounds. Our customers have asked for assistance in this process. I have teamed with Jim Wilcox of CodeCAD...
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Applied Flow Technology

Calculating Energy Costs

AFT Fathom and AFT Arrow have the option to include energy costs in the Output. To utilize this option, first open and fill out the “Cost Settings” window which can be opened from the Analysis dropdown menu. Next open the specification windows for the pumps that you would like to calculate energy usage for, and select the option to “Include Cost in Report” from the “Cost” tab. After running the model, you will be able to review the new cost data in the output.  The cost report is configurable in the Output Control window.      
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Ben Keiser

Problems With Heat Exchanger Specified Heat Rate In Constants?

Using “Specified Heat Rate In Constants” for the thermal model of heat exchangers can often cause problems in system models.  The reason why is because this thermal model type causes the heat exchanger to act like an “assigned heat input” junction as does an assigned flow junction does for providing constant flow rates.  Another problem is that this thermal model can cause unrealistic temperature changes across a heat exchanger.  When the heat rate is specified and the mass flow rate and heat capacity are calculated based on the system solution, the temperature change will be whatever is required to maintain the...
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Recent Comments
Guest — Increasing Heat Exchanger Accuracy for Large Temperature Differences and Non-Linear Heat Capacity | Applied Flow Technology Blog
[...] use for each heat exchanger (see the following link for a discussion on this type of thermal model http://www.aft.com/suppor... Read More
Friday, 31 August 2012 20:13
Des Aubery
Very useful tip. Thank you. In many heat-exchangers, the relationship between heat-transfer & flow-rate would have a curve with c... Read More
Wednesday, 10 April 2013 09:37
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Trey Walters

My 50th Anniversary Visit to the Site of John Glenn’s First American Flight Into Space

Many of you probably saw in the news that today, Monday, February 20th, is the 50th anniversary of John Glenn’s flight into space. The flight was aboard a Mercury-Atlas rocket dubbed Friendship 7. This historic event was a significant step on the way to the Apollo missions to the moon. By good fortune the NASA contractors at Kennedy Space Center had scheduled an AFT training class last week, and I traveled to Florida to teach the class. I took some time to tour the Space Center and Cape Canaveral one evening and was able to visit Complex 14 where the launch took place. The...
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Guest — The Future of Engineering – Part 2 | Applied Flow Technology Blog
[...] I was teaching a training class a few months ago at Kennedy Space Center in Florida and had the good fortune to get a guided... Read More
Friday, 29 June 2012 19:35
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