Process Modeling Simulation & Control

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Q: Does operation warning allow integration between Aspen EDR and simulation mode? A: Yes, operation warnings will be active when the Aspen EDR model is run in simulation mode. You can view them by opening the EDR Browser from the EDR Plate Fin tab. .

Q: Regarding hydraulics, how do you account for the equipment inlet / outlet nozzle elevation differences in Aspen HYSYS? A: In Aspen Plate Fin Exchanger and all of the other Aspen EDR programs, you can specify that gravitational pressure drop be taken into account. This can be very important in two phase applications, particularly if the exchanger is operating in thermosiphon mode. All of the Aspen EDR programs can factor in gravitational pressure drops and you can specify the elevations where necessary. .

Q: What is the Area Ratio and its significance? A: When you look at the sales gas exchanger, it stated that the area ratio was less than one meaning that the area was inadequate to give you the outlet temperatures. In other words, the outlet temperature couldn’t be achieved with the existing configuration. .

Q: Do the costs in Aspen EDR come from Aspen Capital Cost Estimator (ACCE)? A: The costs developed by Aspen EDR can be fine-tuned to increase estimate accuracy and ultimately be consistent with ACCE outputs, including major cost drivers such as material costs. Typically, the costs output by Aspen EDR are used as relative costs to compare one heat exchanger design to another. Later on, you may do rigorous costing for the entire project using one of the products from the Aspen Economic Evaluation suite, which includes stand-alone tools such as Aspen In Plant Cost Estimator or Activated Economics which is a feature in Aspen Plus and Aspen HYSYS. .

Q: What is the approach temp min / max for PFHX? A: Plate-fin exchangers can take advantage of very small temperature differences sometimes as low as 1 degree Kelvin. The maximum temperature approach is determined by thermal stress limitations of the equipment and with large temperature differences, another exchanger type might be more suitable. .

Q: Inside LNG exchangers in Aspen HYSYS, there is the possibility to simulate Wound Coil exchangers. Does Aspen EDR have this capability? A: There is a wound coil model in Aspen HYSYS, but it is not fully rigorous. .

Q: Is AspenTech currently working with vendors to have some standard products available as selectable models, similar to what has been done with plate frame models within Aspen EDR? A: Plate-fin exchangers are typically custom designed for each process application. Our design optimization suggests the appropriate geometry for each set of process conditions. .

Q: How do you properly design the layer patterns for a plate-fin? Does Aspen EDR do it by itself? A: You can directly specify layer patterns in Aspen Plate Fin Exchanger and look at interlayer effects. Many of the leading fabricators use our tool that way. When you’re designing and simulating the exchanger, for most purposes, the stream simulation used is more than adequate. If you want to get into the details of the design and ensure that the design will not be subject to high thermal stresses for example, then you can impose the layer pattern—but this is not an output of the first-shot design. This tends to be a detail that a plate-fin exchanger fabricator will specify to minimize the risk of damaging thermal stresses. It will have some impact on overall thermal performance, but usually this isn’t too significant. .

Q: How important was the hydraulic model for the design within Aspen EDR? A: The hydraulic model helped with the line drop, as well as the equipment drops. .

Q: Some plate-fin manufacturers have Fin Codes with geometric information of fin size, height, thickness, pitch, etc. Does Aspen HYSYS have a database with those Fins Codes? A: Aspen EDR finds the best geometry of fins to meet the process requirements. It looks at fin height and fin frequency, as well as fin type and whether it’s plain, perforated, or serrated fins then finds the best optimum. Our correlations are generally accepted in the industry and our single-phase, boiling, and condensing coefficients for these fin types are widely accepted. You can introduce fabricators coefficients into the system if you’d like to use those correlations, but ours are typically used as the baseline. .

Q: Can you change Aspen EDR to select the smallest exchanger dimensionally or the lightest exchanger? A: Two different demonstrations were done during this webinar—one on Rigorous Shell & Tube sizing from within Aspen HYSYS and the other for designing a plate-fin exchanger and importing the model into Aspen HYSYS. The Shell & Tube design can be calculated to find the minimum area or the minimum cost (typically what customers use). The plate-fin exchanger is good for quickly and accurately finding the configuration of a multi-stream exchanger. This also designs on the basis of minimizing the area of the exchanger. The weights are calculated as a result of the design found. .

Q: At the design stage of a new exchanger, we input the fouling factor. In debottlenecking, do we need to perform "fouling factor adjustment" to match actual exchanger performance, then perform the debottleneck? A: Typically, many clients would do this. In this case study, Petrofac tried to match the information from the client in the original case and then use the same fouling factors .

Q: If we have an existing plate-fin exchanger configuration, can we change the rating method from end point or weighted to EDR Plate Fin and run the model as usual to achieve the same results as going into the Aspen EDR environment? A: No, changing the model type to Aspen EDR will not run the Aspen EDR sizing optimization automatically. Once you change the model type to EDR Plate Fin in Aspen HYSYS, you will need to import the Aspen EDR file to specify the rigorous design. Once the file has been imported into Aspen HYSYS, the Aspen EDR model will run in simulation mode in the flowsheet, which means that the design will be fixed but the process conditions will be set by the Aspen EDR model. .