modelJoin

Information

Purpose of model

A model of a split/join that is used to split or join mass flow rates in a hydraulic circuit. It is based on the three balance equations of mass, energy, and momentum. It is not discretized and only features one control volume. No heat losses are considered, but a linear pressure loss model is implemented. The model is mainly used for the simulation of district heating networks.

The model is used as a junction in district heating networks and dwelling heat systems.

Level of detail, physical effects considered, and physical insight

L2 (defined in the CodingConventions)

• linear pressure loss
• thermal intertia
• constant fluid properties

Limits of validity

The volume of the split has to be known. Moreover, the chosen pressure loss model has to fit the investigation purpose.

Interfaces

Governing Equations

The equations have been simplified for an easier description of the model.

The equations have been simplified for an easier description of the model.

V*rho*dh/dt=m_in*h_in+m_out1*h_out1+m_out2*h_out2

p_in-p=delta_p(m_flow_in)

p-p_out1=delta_p(m_flow_out1)

p-p_out2=delta_p(m_flow_out2)

0=m_flow_in+m_flow_out1+m_flow_out2

References

The model was used and verified in the following publication:

[1] Westphal, J.; Brunnemann, J.; Speerforck, A.; Enabling the dynamic simulation of an unaggregated, meshed district heating network with several thousand substations;Energy; 2025

Version History

Model was inserted by Jan Westphal (j.westphal@tuhh.de) August 2025

Parameters

Connectors

Components