Abstract
This paper presents software for creation and manipulation of parametric shell and tube heat exchanger geometry. Presented software is a key part in developing software for mechanical design or check of shell and tube heat exchangers according to (EN 13445 Unfired pressure vessels, 2009), which will also have optimisation capabilities. Presented software is using only freely available open source software.
A shell and tube heat exchanger can be described by a group of parameters. Structural analysis methods evaluate individual components separately, but they usually require (among other things) thorough knowledge of surrounding components geometries. In case of checking an already manufactured exchanger, a user has to input all the necessary parameters into software for structural analysis just once, and evaluate the design very efficiently. However, in case of design, where the final geometry is not known yet, a designer has to check multiple designs while adjusting some parameters and keeping track of their dependencies. The last task could be simplified if the exchanger geometry was modelled as a parametric assembly with automatic update procedure for changing dependent parameters.
Shell and tube heat exchanger geometry can be easily represented as an assembly of parts, such as shells, heads, flanges, tubes, tubesheets, baffles, saddle supports, etc. Most of these part classes have a few shape types which are not developed further. Such parts can be prepared in a database as parametric models. Afterwards, the model of exchanger geometry can be easily assembled using these parametric parts and constraints.
Currently there is no software which would be able to optimise mechanical design of shell and tube heat exchangers according to (EN 13445 Unfired pressure vessels, 2009). Since in general, the strength of a component depends on surrounding components, single components cannot be optimised separately. There is obvious need for parametric model tailored for purposes of heat exchanger mechanical design optimisation. Parametric geometric assembly is a key part of the model.
Presented software used history-based multi-level assembly design. Parts and subassemblies are absolutely positioned in local subassembly coordinate systems. Items in assembly tree are ordered and their defining parameters may depend on the parameters of previous items. Parameters and low level connections can be visualised as an acyclic directed graph.
Software was created in the Python programming language. Libraries PythonOCC and wxPython were used for creating geometry and graphical user interface respectively. A user can add, modify or delete parts of predefined types and high level connections between them. When modifying a part, user is allowed to directly change only independent parameters. Thanks to PythonOCC, created geometry can be easily exported to standard STEP format and therefore can be used in other software e.g. for FEM or CFD analyses.
