The first step in modeling any system is to consider the most efficient way to create the input and, more importantly, how to best review the results. After you determine how to best review the results, you can define the input node numbering scheme. Based on the node numbering scheme, you can then decide how to generate the model to take advantage of the various rotate, duplicate, and include options.
For this example system, the core piping is modeled using node numbers from 1000 to 1999, and the jacket is modeled using node numbers starting at 2000. Additionally, similar locations on the two systems will have the same base node number, that is, nodes 1110 and 2110 describe the same point on both the core and the jacket. Setting up the node numbers in this manner enables one of the systems to be generated from the other, using either the duplicate or the include options of the input preprocessor. You can also view the system individually in the plot by the Range command and breaking the model at node 1999. The other advantage to this numbering scheme is that when reviewing the output, you can immediately tell from the node number whether the point in question belongs to the core or the jacket.
Although not necessary for a small system such as this, additional node number ranges can be defined to differentiate parts of the model. To illustrate, the following additional constraints can be placed on the node numbers. The ground level piping will have nodes in the 100-400 series, while the second level piping will have nodes in the 500-900 series. For example, node 1110 will be a core node at ground level and node 2550 will be a jacket node on the second level. To indicate locations where external supports are applied to the system, node numbers will end in 5; all other points will be multiples of 10. Similar node numbering schemes can be used to differentiate branches from headers, pipe from structural steel, and various line sizes. Starting the modeling process with a clearly defined plan can ease both input verification and output review. For example, consider reviewing the input for this system and finding a spring hanger at node 1530. You can quickly recognize this as an error because the 1000 series nodes make up the core piping and cannot use spring hangers. Additionally, support node numbering should end with a 5.