WOLFRAM SYSTEM MODELER

# TwoPhaseDensity

Calculation of mean density for two phase flow # Wolfram Language

In:= `SystemModel["Modelica.Fluid.Dissipation.Utilities.Functions.PressureLoss.TwoPhase.TwoPhaseDensity"]`
Out:= # Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

The gaseous and the liquid part of a fluid in a two phase flow are often discontinuously distributed. This complex behaviour is simplified for engineering calculations. The two phase flow of different fluid flow situations (e.g., bubble or stratified flow) is modelled as if the gaseous and the liquid phase are continuously distributed.

A mean density assuming a continuous distribution out of a discontinuous two phase fluid flow situation can be calculated with a homogeneous or a heterogeneous approach (see dp_twoPhaseOverall_DP).

The following modelling approaches can be used to calculate the mean density of two phase flow:

• homogeneous density (homogeneous approach)
• momentum flux density (heterogeneous approach)
• kinetic energy flow density (heterogeneous approach)

The heterogeneous approaches are analytically derived by minimising the momentum flux or the kinetic energy flow assuming implicitly that the two-phase flow will tend towards the minimum of this quantity.

#### References

VDI:
VDI - Wärmeatlas: Berechnungsblätter für den Wärmeübergang. Springer Verlag, 10th edition, 2006.

# Syntax

rho_2ph = TwoPhaseDensity(voidFractionApproach, massFlowRateCorrection, rho_g, rho_l, epsilon_A, x_flow)

# Inputs (6)

voidFractionApproach Default Value: Modelica.Fluid.Dissipation.Utilities.Types.VoidFractionApproach.Homogeneous Type: VoidFractionApproach Description: Choice of void fraction approach Default Value: false Type: Boolean Description: Consider heterogeneous mass flow rate correction Type: Density (kg/m³) Description: Density of gaseous phase Type: Density (kg/m³) Description: Density of liquid phase Type: Real Description: Void fraction (cross sectional averaged) Type: Real Description: Mass flow rate quality

# Outputs (1)

rho_2ph Type: Density (kg/m³) Description: Mean density of two phase flow

# Revisions

• 2 May 2011 by Stefan Wischhusen:
Corrected a logical error in use of input `massFlowRateCorrection`.