modelCell1Dim

1-D lumped fluid flow model (Real fluid model)
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Information

Model Cell1Dim describes the flow of fluid through a single cell. An overall flow model can be obtained by interconnecting several cells in series (see Flow1Dim).

Pressure and enthalpy are selected as state variables.

Two types of variables can be distinguished: cell variables and node variables. Node variables are characterized by the su (supply) and ex (exhaust) subscripts, and correspond to the inlet and outlet nodes at each cell. The relation between the cell and node values depends on the discretization scheme selected.

The assumptions for this model are:

  • Velocity is considered uniform on the cross section. 1-D lumped parameter model
  • The model is based on dynamic mass and energy balances and on a static momentum balance
  • Constant pressure is assumed in the cell
  • Axial thermal energy transfer is neglected
  • Thermal energy transfer through the lateral surface is ensured by the wall_int connector. The actual heat flow is computed by the thermal energy model

The model is characterized by two flow connector and one lumped thermal port connector. During normal operation the fluid enters the model from the InFlow connector and exits from the OutFlow connector. In case of flow reversal the fluid direction is inversed.

The thermal energy transfer through the lateral surface is computed by the ConvectiveHeatTransfer model which is inerithed in the Cell1Dim model.

Modelling options

In the General tab the following options are availabe:

  • Medium: the user has the possibility to easly switch Medium.
  • HeatTransfer: the user can choose the thermal energy model he prefers

In the Initialization tab the following options are availabe:

  • steadystate: If it sets to true, the derivative of enthalpy is sets to zero during Initialization

Numerical options

In this tab several options are available to make the model more robust:

  • Discretization: 2 main discretization options are available: UpWind and central difference method. The authors raccomand the UpWind Scheme - AllowsFlowReversal in case flow reversal is expected.
  • Mdotconst: assume constant mass flow rate at each node.
  • max_der: if true the density derivative is truncated during phase change
  • filter_dMdt: if true a first order filter is applied to the fast variations of the density with respect to time
  • max_drhodt: it represents the maximum value of the density derivative. It activates when using max_der is set to true
  • TT: it represents the integration time of the first order filter. It activates when filter_dMdt is set to true
  • ComputeSat: if false saturation properties are not computed in the fluid model and they can be passed as a parameter.

Parameters

TypeNameDefaultDescription
IntegerNt1Number of cells in parallel
RealpiModelica.Constants.pipi-greco
Modelica.SIunits.VolumeViVolume of a single cell
Modelica.SIunits.AreaAiLateral surface of a single cell
Modelica.SIunits.MassFlowRateMdotnomNominal fluid flow rate
Modelica.SIunits.CoefficientOfHeatTransferUnom_lif HTtype = LiqVap : Heat transfer coefficient, liquid zone
Modelica.SIunits.CoefficientOfHeatTransferUnom_tpif HTtype = LiqVap : heat transfer coefficient, two-phase zone
Modelica.SIunits.CoefficientOfHeatTransferUnom_vif HTtype = LiqVap : heat transfer coefficient, vapor zone
Initialization
Modelica.SIunits.PressurepstartFluid pressure start value
Medium.SpecificEnthalpyhstart1E5Start value of enthalpy
Numerical options
DiscretizationsDiscretizationThermoCycle.Functions.Enumerations.Discretizations.centr_diffSelection of the spatial discretization scheme
BooleanMdotconstfalseSet to yes to assume constant mass flow rate at each node (easier convergence)
Booleanmax_derfalseSet to yes to limit the density derivative during phase transitions
Booleanfilter_dMdtfalseSet to yes to filter dMdt with a first-order filter
Realmax_drhodt100Maximum value for the density derivative
Modelica.SIunits.TimeTT1Integration time of the first-order filter
BooleanComputeSatfalseCan be disabled if the flow is single-phase, or if saturation is passed as a parameter
Initialization › Intialization options
Booleansteadystatetrueif true, sets the derivative of h (working fluids enthalpy in each cell) to zero during Initialization

Connectors

TypeNameDefaultDescription
ThermoCycle.Interfaces.Fluid.FlangeAInFlow
ThermoCycle.Interfaces.Fluid.FlangeBOutFlow
ThermoCycle.Interfaces.HeatTransfer.ThermalPortLWall_int

Components

TypeNameDefaultDescription
Realsat_in{0, 0, 0, 0, 0, 0, 1E5, 0, 0, 0, 0, 0, 0, 300}
HeatTransferheatTransfer
Medium.ThermodynamicStatefluidState
Medium.SaturationPropertiessat
Medium.AbsolutePressurep
Modelica.SIunits.MassFlowRateM_dot_su
Modelica.SIunits.MassFlowRateM_dot_ex
Medium.SpecificEnthalpyhFluid specific enthalpy at the cells
Medium.TemperatureTFluid temperature
Medium.DensityrhoFluid cell density
Modelica.SIunits.DerDensityByEnthalpydrdhDerivative of density by enthalpy
Modelica.SIunits.DerDensityByPressuredrdpDerivative of density by pressure
Modelica.SIunits.SpecificEnthalpyhnode_suEnthalpy state variable at inlet node
Modelica.SIunits.SpecificEnthalpyhnode_exEnthalpy state variable at outlet node
RealdMdtTime derivative of mass in cell
Modelica.SIunits.HeatFluxqdotheat flux at each cell
RealxVapor quality
Modelica.SIunits.SpecificEnthalpyh_l
Modelica.SIunits.SpecificEnthalpyh_v
Modelica.SIunits.PowerQ_totTotal heat flux exchanged by the thermal port
Modelica.SIunits.MassM_totTotal mass of the fluid in the component

Contents

NameDescription
Medium
HeatTransfer