Network User Element

The user can define and code his/her own gas network element. The process of doing so requires the following steps:

• decide whether the element should be pipe-like (i.e. the total temperature and static temperature at the end nodes differ) or chamber-connecting-like (i.e. the element connects large chambers and the total and static temperatures at the end nodes are equal).
• choose a type name. For a pipe-like element the name has to start with “UP” followed by 5 characters to be choosen freely by the user (UPxxxxx). For a chamber-connecting-like element it has to start with “U”, followed by a character unequal to “P” and followed by 5 characters to be choosen freely by the user (Uyxxxxx, y unequal to “P”).
• decide on the number of constants to describe the element. This number has to be specified on the *FLUID SECTION card with the CONSTANTS parameter.
• add an entry in the if-construct in subroutine user_network_element.f. Notice that the type labels in the input deck (just as everything else, except file names) are converted into upper case when being read by CalculiX.
• write an appropriate user network element subroutine, e.g. user_network_element_pxxxxx.f or user_network_element_yxxxxx.f. Details can be found in Section . This routine describes how the total pressure at the end nodes,the total temperature at the end nodes and the mass flow through the element are linked.
• add an entry in the if-construct in subroutine calcgeomelemnet.f (marked by START insert and END insert). This routine is used to determine the cross section area of the element (is used to calculate the static temperature from the total temperature).
• add an entry in the if-construct in subroutine calcheatnet.f (marked by START insert and END insert). This routine is used to calculate the heat generation e.g. due to centrifugal forces.