quickly making property calculations in CHEMCAD
Quick, what's the bubble point of the process stream entering one of your columns? What's the viscosity of the stream entering your heat exchanger? You may find yourself needing answers to these types of questions much more often than needing to model an entire process, and we've made it easy to access these calculations in CHEMCAD.
If you have an existing flowsheet with a stream already set up with the right composition, just double-click the stream, and you can immediately calculate bubble/dew point (T or P) or vapor fractions. Just remember Gibbs' phase rule and specify two of the three available fields (T, P, VF); then click the Flash button and you'll have your answer. To get at the thermophysical properties, just right-click the stream and select View Properties to get a quick report.
But what if you want to use a composition that isn't in your current flowsheet? If all the right chemicals are in your component list, and you've got the appropriate K-value and enthalpy methods selected, try this trick:
- Make sure no streams are selected (you can click in the white space of the flowsheet to be certain).
- On the CHEMCAD main menu, choose Specifications > Select Streams.
- In the input dialog, type a stream number not currently used in your flowsheet (like 999) and click OK.
You'll now be working with a 'dummy stream.' You can specify stream conditions and compositions, but nothing you do here will affect any of your actual flowsheet streams. By clicking Report > Stream Properties > Select Streams and entering that dummy stream number, you can even generate thermophysical property reports. The dummy stream will be accessible for as long as you have that flowsheet open (it's cleared from memory if you switch flowsheets or close CHEMCAD).
Don't let your investment in simulation sit around waiting for the large projects! CHEMCAD is like having your own chemical engineering calculator, and it's ready to supercharge all of your tasks.
Whether you're working on a simulation of your entire process, sizing a few pieces of equipment, or just looking for a quick property calculation, don't hesitate to get in touch with our technical staff for more best-practices tips.