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Welcome to the Applied Flow Technology Blog.
Abby Zimmerman

Using Branch Junctions to Model Desuperheaters

Superheated steam is often used in mechanical power applications, such as driving turbines. For heating or industrial processes, however, saturated steam is more efficient. Desuperheaters are used to lower the temperature of superheated steam, so that it can be more effectively used in industrial processes. A desuperheater lowers the temperature of the steam by injecting water. Now, the question is, how can you model a desuperheater within AFT Arrow? AFT Arrow  is a single-phase program for compressible flow, so it cannot model liquid water. Conveniently though, there is a feature built into the branch junction that can model a desuperheater....
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Erin Onat

Closing the Loop on Modeling Closed Loop Systems in AFT software

For several users of AFT software , it goes pretty predictably: first you place a pressure junction, then maybe a pump, then some sources of pressure drop including valves and heat exchangers, and then the model is finished off with another pressure junction. Of course, this is greatly oversimplifying the process and the vast array of systems that are modeled with AFT software, but here’s my point: most users are more familiar with modeling open systems that include individual pressure junctions located both upstream and downstream of the system. But what about modeling closed systems? The truth is that modeling...
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Recent Comments
Kevin
Really nice article! This greatly simplifies the thought process around closed systems. I think it's worth noting that the absol... Read More
Monday, 18 September 2017 22:05
Erin Onat
Kevin, The clarification you pointed out is vital, and I have updated my post to be more explicit about this point. Thank you for... Read More
Tuesday, 19 September 2017 16:54
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Scott Lang

Start your engines! Modeling an Inertial Pump Startup

There are many (six!) ways to define a pump transient event in AFT Impulse . This gives you great flexibility in creating a model that behaves the way you want it to. One thing true for all pumps is that they must be started at least once. Pump startups often cause significant transient effects on the system so you may wish to model this with AFT Impulse. Even narrowing your pump transient down to a startup, there are still four models left to choose from: Without Inertia Startup With Inertia and No Back Flow or Reverse Speed Startup With Inertia...
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Scott Lang

When to Begin? Time and Events in Transient Studies

To define any transient event in AFT Impulse or AFT Fathom XTS the application must know when it begins. To do so, the user should know how time and event logic is approached in AFT’s transient solvers. In this article, we will discuss the three different time bases used in the applications, the selection of a single or repeating event, and the many possible triggering events that can start the user defined transient. The user defines these items in the Initiation of Transient section of the junction’s Transient tab. The requirements for each junction can vary, but the general approach...
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Jake Miller

Calculating Pressure Drop Across Sharp-Edged Perforated Plates

Sometimes design engineers will install a screen to protect equipment like centrifugal pumps. Screens are available in a variety of configurations and each has its own head loss characteristics. As such, this article will strictly discuss thin-walled perforated plates with uniform diameter holes. AFT Fathom provides a screen junction that allows users to choose from four different screen types; Perforated Plate (Sharp-Edged), Perforated Plate (Round-Edged), Circular Wire, and Silk Thread Screen. Every screen has an open flow area that allows the working fluid to bypass the screen while restricting any foreign objects that are not able to pass through this...
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Aaron Ren
This article is very good! I got much things from your articles. I think it is much better if you can add a tool in AFT Fathom t... Read More
Wednesday, 27 December 2017 08:44
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Jake Miller

Thank Your Machinist for Me

Cutting through the mysteries of impeller trimming Centrifugal pumps are a common and integral part of many industrial applications related to fluid flow of any kind. They require significant amounts of energy to operate. Unfortunately, many pumps are oversized for their applications. When pumps are not properly sized this can lead to operational difficulties that must be addressed. A pragmatic solution to this problem may be to reduce the outer diameter of the pump impeller to better meet flow requirements and avoid costly operating procedures such as throttling or expensive replacements. Changing the impeller diameter will affect the performance of...
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Erin Onat

Inherent vs. Installed Control Valve Curves and How They Relate to AFT Software

As tech support engineers, we sometimes receive questions from users confused about what control valve characteristic curve (inherent or installed) they are inputting into AFT Fathom , AFT Arrow , or AFT Impulse . The inherent control valve characteristic curve plots the valve open percent versus the percent of maximum Cv. This curve is true regardless of the system effects on the valve. The installed control valve characteristic curve plots the valve open percent versus the flow through the valve, and this plot is dependent on the conditions specific to the system. For example, if the control valve flow setpoint...
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