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Networks and Network Connections

Simscape™ Fluids™ models can include multiple fluid networks, each representing a single-fluid system. Only use one fluid properties block per network to avoid model compilation errors. Two fluid networks are distinct if they belong to different Simscape domains or if they are not directly connected.

You can use the blocks in the Fluid Network Interfaces library to connect different domains. For example, you can use the Condenser-Evaporator 2P-MA block to model heat exchange between a two-phase and moist air network.

Grounding Rules

The absence of a reference block, such as a Reservoir (TL) block, or dynamic component in a non-isothermal liquid domain may result in variable drift in your model. The internal node of a reference or dynamic component provides a state reference during momentum balance calculations. See for more information on internal volumes in dynamic components.

If you observe variable drift during your simulation, add grounding to your model.

Ground a Thermal Liquid Closed Loop

Simulating the example network below, consisting of two pipes connected to a Controlled Mass Flow Rate Source (TL) block, will result in a net increase in pipe temperature and pressure.

Model of a closed-loop thermal liquid network

Despite the lack of explicit heat transfer, the absence of thermal grounding in the network results in a net increase of energy due to energy conservation. The increase of energy in the system takes the form of a rise in temperature.

Plot of rising temperature and pressure in closed loop

You can mitigate this phenomenon by adding a dynamic component to your network. Add a Tank (TL) block just before the controlled Mass Flow Rate Source (TL). Right-click on the block and select Simscape > Block choices > Two inlets.

Model of a closed-loop thermal liquid network with grounding

In this scenario, the pipe pressure and temperature reach steady-state. The differential equations associated with the Tank (TL) internal volume reduce the stiffness of the model solution, removing the condition of gradually increasing system temperature and pressure.

Plot of steady temperature and pressure in closed loop

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