I am interested in modeling gas networks distributing a gas mixture with different levels of hydrogen blending. Is it possible to specify in SAInt the chemical composition of a gas mixture that is different from natural gas? It would also be great to check how SAInt tracks gas composition and quality in the network.
Yes! SAInt provides you with a set of tools to model the transport and distribution of a user-specified gas mixture, as well as to track quality and composition at any off-take point.
Your first step is defining an object called “quality” in your network. In a “quality” object you specify the list of chemical components, their molar percentage in the mixture, and other energy- or thermodynamic-related properties. Your second step is linking a “quality” to an in-take point by defining its SQSETNAME property. The third and last step is to make sure that you don’t have an active network event of type QTOFF in your scenario, which would turn off the default quality calculations and tracking.
With those three steps, the user can analyze how the gas mixture quality and the gas components are changing in the system, in either a steady state scenario or a dynamic simulation. You can choose one specific gas component or the mixture GCV for your branch legend, and you are able to inspect the spatial distribution of the selected indicator. Or, in a dynamic simulation, you can make an animation showing how, for example, hydrogen is flowing and blending based on the patterns of injections and consumptions. Obviously, you can plot the molar percentage of a component at one node or extract a table instead. You can use the “pathplot” command to check how quality or composition-related properties are changing from node one to node two along a specified path and time step.
What is cool about SAInt is that you can either build a gas mixture using the predefined components library or describe a brand-new component and build around it a new gas “quality” that fits exactly your needs.
I also want to stress two other important modeling assumptions:
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SAInt assumes “perfect mixing” at the node. So, it is impossible to model how “pockets” of a certain component may move in the system because of imperfect mixing.
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SAInt has a separate calculation method for the Z factor when the mixtures may have a compressibility factor greater than one. Based on the relative density of the mixtures during the simulation, SAInt chooses the appropriate calculation method. This allows for accommodating a wide variety of chemical compositions, such as pure hydrogen flow.
I am not going to point you to any page of the Reference Guide (there you can find a lot to cover your question), but I prefer to redirect you to this How-To guide “Create and Edit a Gas Quality in the GUI”.