modelPipeFlow_L4_Simple_ground

Information

Purpose of model

A simple model of a pipe flow with a VLE-fluid (Vapor liquid equilibrium) based on the three balance equations of energy, momentum and mass. The mass and the energy balance are dynamic, while the momentum balance is considered static. The balance equations are discretized with a finite volume method. The model uses n+2 fluid models from the TIL media to compute the fluid states at the inlet, outlet, and inside the control volumes of the pipe. Moreover, it uses a replaceable pressure loss model and a replaceable heat transfer model. The main difference compared to the PipeFlow_L4_Simple model is that it calculates parameters like alpha or delta_p for the calculation of the heat and pressure losses. Therefore, heat and pressure losses are considered. Heat losses are transferred through a heat port if the heat port is connected. However, the heat port doesn’t have to be connected for the model to function. The pipe model can be connected to other models via two fluid ports, which pass the pressure, the specific enthalpy, the mass fraction and the mass flow rate as variables. The model allows reverse flow. In the model are instances of iCom and summary, which are not relevant for the physical understanding of the model. The model was extended from the ClaRa library.

Level of detail, physical effects considered, and physical insight

The general physics of the model are described in ClaRa.Components.VolumesValvesFittings.Pipes.PipeFlow_L4_Simple.

The heat model is defined with constant heat transfer coefficent. The coefficient is calculated considering just heat conduction. The influence of the pipe wall on the heat conduction is assumed to be small. Just the insulation of the pipe and the underground are considered.

The nominal pressure loss is calculated using the method shown in [Krimmling,2011].

Limits of validity

The accuracy of the dynamic effects of the model depends on the number of control volumes. The thermal inertia of the pipe wall is neglected.

Interfaces

Governing Equations

The equations have been simplified for an easier description.

V*rho*dh/dt=m_in*h_in+m_out*h_out+Q_flow_out

drho/dt=m_in+m_out

p_in-p_out=delta_p

T and rho are determined with the fluid models

Validation

see ClaRa pipe for validation

References

The model was extended from the ClaRa library

Version History

Model created by Tobias Ramm (tobias.ramm@tuhh.de) November 2015

Model modified by Lisa Andresen (andresen@tuhh.de) December 2015

Model documented by Jan Westphal (j.westphal@tuhh.de) January 2025

Parameters

Connectors

Components