0D model and steady state

The library describes the components of a thermodynamic process at a system level, focusing on the interactions between inputs and outputs of a component. It is thus considered as a 0D modeling approach.

There is no detailed description of the physical phenomena, but a focus on the macro behaviour of the components. It is a thermalhydraulic description of the system, focusing on computing pressures, mass flow rates and enthalpies throughout the system. All MML models are described at steady state : there are no time depending equations.

MML was built based on the TSP library (https://thermosyspro.com/), but it has some some key differences :

• In MML3, flow is assumed to go only in one direction and cannot be reversed
• For enthalpy propagation, stream connectors are used instead of the h_vol solution used in TSP (and in previous versions of MML, until MML2.4)
• All components are acausal, you can impose different sets of physical quantities or conversely set the component characteristics, for the same model.

Flow, potential and stream variables

Here are the connector variables types we use in MML :

• Potential (meaning non flow, non causal, non stream) variable, used for the pressure
• flow variable used for mass flow rate and power
• stream variable used for enthalpy and mass fraction

Units

Reference units in all the library are defined by the International System of Units: Kelvin (K) for temperature, Pascal (Pa) for the absolute pressure, kg/s for the flow, and meters for the length.

For other units, sensors must be used and provides an automatic conversion. See Sensors

Locally balanced

Each component of the library is designed to be locally balanced to help the user to identify singularity of the global model during compilation. To understand the distinctions between global and local balances, the reader may read the following page :

What are local/global balances ?

Inheritance