I tend to reflect on the truly endless list of things I am so grateful for. While this list is by no means exhaustive, some of these things include my loved ones, my awesome job at AFT, the bounty of pumpkin-flavored treats that sweeten up my fall-time snacking options, and of course, AFT Impulse’s detection of artificial transients. While the dreaded Warning message that an artificial transient triggers can cause any engineer’s stomach to turn, I’ll explain why every AFT Impulse user should add this feature to his/her list of things to be thankful for as well. Let’s start with an...
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. You may...
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 closed systems...
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 is fixed at 250...
Trying to design and analyze piping systems can be a complicated, and difficult task for engineers. This was especially true before the advent of easily accessible computer technology. Hand calculations required hundreds of hours of painstaking work, by entire teams of people. Great care had to be taken to ensure the reliability and accuracy of the results. Human beings do make mistakes, after all.
In today’s engineering world, there are a multitude of computer tools designed to make the design process simpler, faster, and more reliable, such as AFT’s family of analysis products. AFT products revolve around graphically based, drag and drop interfaces that makes creating a computer model of piping systems quick, and easy. Being able to create simulation models with little effort, however, can be a bit of a double-edged sword.
Frequently in tech support, when a difficult-to-converge model comes in, one of the first things we check is whether or not any tees in the model are being modeled as detailed tees. The reason for this is that the hydraulic calculations involving detailed tees can be complex due to the interdependence between velocity and pressure loss for each pipe connected to the tee. Iteration must, therefore, be performed to find a pressure loss and flow through each connecting pipe that agrees with the rest of the flow and pressure solutions in the model. This begs the question, then, what calculations are...
November 21, 2016, marks AFT Impulse's 20th anniversary! Below is a timeline that captures a few of the most significant ways it has evolved from Version 1.0 to Version 6.0.
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