Where Do I Even Start?
January 16, 2014
ProMax offers a large selection of variables that can be specified by the user, and for anybody new to simulation software this freedom can be quite daunting. How do you know which ones to set manually and which are better left for the program to calculate? Here are some tips to help get you started:
- Every process stream needs four degrees of freedom fulfilled to turn green – usually temperature, pressure, flow rate, and composition. For more detailed information, see the ProMax Help file “Degrees of Freedom (Required Specifications)."
- Inlet streams require all four to be set directly or indirectly by the user.
- Recycle block outlets require all four to be directly set by the user in the stream immediately leaving the recycle block.
- Many blocks (exchangers, columns, condensers, reboilers, reactors, and separators) require a user-defined pressure drop across the unit. The actual values vary between processes, but 2-5 psi is generally a good initial guess if you lack specific data.
- Heat exchangers with multiple sides should have a pressure drop specified for each side.
- Every time you have a pump or expander, you should specify an efficiency in the block, usually at or above 65% for centrifugal pumps, 70-75% for compressors and 75-80% for expanders.
- When adding other specifications, it’s helpful to think about the functions of each of your units. For example, the purpose of pumps, valves, and expanders is to change the pressure of a stream, so setting the pressure coming out of the block is logical. Similarly, heat exchangers change the temperature of a process flow, so you should consider setting the outlet temperature or heat duty from these units.
- Cross exchangers require two pressure drops (one for each side) and only one outlet temperature or heat duty, as the interaction between the two sides accounts for the temperature of the other outlet stream.
- A large number of example files are loaded with the ProMax software, and can be a great resource for beginning a similar simulation.
For more information on getting started, check out some of our basic web tutorials here: Support
Bryan Research and Engineering offers introductory training classes for ProMax: 100 Level: Oil & Gas Focus and 100 Level: Air Emissions. These are excellent opportunities to learn about the program and its capabilities, offered free of charge and taught by our highly trained engineering staff. A list of current training classes and locations can be found at: Training Sessions.