Modelica.Fluid.Vessels.BaseClasses

Information

Package Content

Name	Description
PartialLumpedVessel	Lumped volume with a vector of fluid ports and replaceable heat transfer model
HeatTransfer	HeatTransfer models for vessels
VesselPortsData	Data to describe inlet/outlet ports at vessels: diameter -- Inner (hydraulic) diameter of inlet/outlet port height -- Height over the bottom of the vessel zeta_out -- Hydraulic resistance out of vessel, default 0.5 for small diameter mounted flush with the wall zeta_in -- Hydraulic resistance into vessel, default 1.04 for small diameter mounted flush with the wall
VesselFluidPorts_a	Fluid connector with filled, large icon to be used for horizontally aligned vectors of FluidPorts (vector dimensions must be added after dragging)
VesselFluidPorts_b	Fluid connector with outlined, large icon to be used for horizontally aligned vectors of FluidPorts (vector dimensions must be added after dragging)

Modelica.Fluid.Vessels.BaseClasses.PartialLumpedVessel

Information

This base class extends PartialLumpedVolume with a vector of fluid ports and a replaceable wall HeatTransfer model.

The following modeling assumption are made:

• homogeneous medium, i.e., phase separation is not taken into account,
• no kinetic energy in the fluid, i.e., kinetic energy dissipates into the internal energy,
• pressure loss definitions at vessel ports assume incompressible fluid,
• outflow of ambient media is prevented at each port assuming check valve behavior. If fluidlevel < portsData_height[i] and   ports[i].p < vessel_ps_static[i] massflow at the port is set to 0.

Each port has a (hydraulic) diameter and a height above the bottom of the vessel, which can be configured using the  portsData record. Alternatively the impact of port geometries can be neglected with use_portsData=false. This might be useful for early design studies. Note that this means to assume an infinite port diameter at the bottom of the vessel. Pressure drops and heights of the ports as well as kinetic and potential energy fluid entering or leaving the vessel are neglected then.

The following variables need to be defined by an extending model:

• input fluidVolume, the volume of the fluid in the vessel,
• vessel_ps_static[nPorts], the static pressures inside the vessel at the height of the corresponding ports, at zero flow velocity, and
• Wb_flow, work term of the energy balance, e.g., p*der(V) if the volume is not constant or stirrer power.

An extending model should define:

• parameter vesselArea (default: Modelica.Constants.inf m2), the area of the vessel, to be related to cross flow areas of the ports for the consideration of dynamic pressure effects.

Optionally the fluid level may vary in the vessel, which effects the flow through the ports at configurable portsData_height[nPorts]. This is why an extending model with varying fluid level needs to define:

• input fluidLevel (default: 0m), the level the fluid in the vessel, and
• parameter fluidLevel_max (default: 1m), the maximum level that must not be exceeded. Ports at or above fluidLevel_max can only receive inflow.

An extending model should not access the portsData record defined in the configuration dialog, as an access to portsData may fail for use_portsData=false or nPorts=0.

Instead the predefined variables

• portsData_diameter[nPorts],
• portsData_height[nPorts],
• portsData_zeta_in[nPorts], and
• portsData_zeta_out[nPorts]

should be used if these values are needed.

Parameters

Name	Description
replaceable package Medium	Medium in the component
Ports
use_portsData	= false to neglect pressure loss and kinetic energy
portsData[if use_portsData then nPorts else 0]	Data of inlet/outlet ports
Assumptions
Dynamics
energyDynamics	Formulation of energy balance
massDynamics	Formulation of mass balance
Heat transfer
use_HeatTransfer	= true to use the HeatTransfer model
replaceable model HeatTransfer	Wall heat transfer
Initialization
p_start	Start value of pressure [Pa]
use_T_start	= true, use T_start, otherwise h_start
T_start	Start value of temperature [K]
h_start	Start value of specific enthalpy [J/kg]
X_start[Medium.nX]	Start value of mass fractions m_i/m [kg/kg]
C_start[Medium.nC]	Start value of trace substances
Advanced
Port properties
m_flow_nominal	Nominal value for mass flow rates in ports [kg/s]
m_flow_small	Regularization range at zero mass flow rate [kg/s]
use_Re	= true, if turbulent region is defined by Re, otherwise by m_flow_small

Connectors

Name	Description
ports[nPorts]	Fluid inlets and outlets
heatPort
Assumptions
Heat transfer
replaceable model HeatTransfer	Wall heat transfer

Modelica.Fluid.Vessels.BaseClasses.VesselPortsData

Information

Vessel Port Data

This record describes the ports of a vessel. The variables in it are mostly self-explanatory (see list below); only the ζ loss factors are discussed further. All data is quoted from Idelchik (1994).

Outlet Coefficients

If a straight pipe with constant cross section is mounted flush with the wall, its outlet pressure loss coefficient will be ζ = 0.5 (Idelchik, p. 160, Diagram 3-1, paragraph 2).

If a straight pipe with constant cross section is mounted into a vessel such that the entrance into it is at a distance b from the wall (inside) the following table can be used. Herein, δ is the tube wall thickness (Idelchik, p. 160, Diagram 3-1, paragraph 1).

If a straight pipe with a circular bellmouth inlet (collector) without baffle is mounted flush with the wall then its pressure loss coefficient can be established from the following table. Herein, r is the radius of the bellmouth inlet surface (Idelchik, p. 164 f., Diagram 3-4, paragraph b)

If a straight pipe with a circular bellmouth inlet (collector) without baffle is mounted at a distance from a wall then its pressure loss coefficient can be established from the following table. Herein, r is the radius of the bellmouth inlet surface (Idelchik, p. 164 f., Diagram 3-4, paragraph a)

Inlet Coefficients

If a straight pipe with constant circular cross section is mounted flush with the wall, its vessel inlet pressure loss coefficient will be according to the following table (Idelchik, p. 209 f., Diagram 4-2 with A_port/A_vessel = 0 and Idelchik, p. 640, Diagram 11-1, graph a). According to the text, m = 9 is appropriate for fully developed turbulent flow.

For larger port diameters, relative to the area of the vessel, the inlet pressure loss coefficient will be according to the following table (Idelchik, p. 209 f., Diagram 4-2 with m = 7).

References

Idelchik I.E. (1994):

Handbook of Hydraulic Resistance. 3rd edition, Begell House, ISBN 0-8493-9908-4

Parameters

Name	Description
diameter	Inner (hydraulic) diameter of inlet/outlet port [m]
height	Height over the bottom of the vessel [m]
zeta_out	Hydraulic resistance out of vessel, default 0.5 for small diameter mounted flush with the wall
zeta_in	Hydraulic resistance into vessel, default 1.04 for small diameter mounted flush with the wall

Modelica.Fluid.Vessels.BaseClasses.VesselFluidPorts_a

Information

Parameters

Name	Description
replaceable package Medium	Medium model

Contents

Name	Description
m_flow	Mass flow rate from the connection point into the component [kg/s]
p	Thermodynamic pressure in the connection point [Pa]
h_outflow	Specific thermodynamic enthalpy close to the connection point if m_flow < 0 [J/kg]
Xi_outflow[Medium.nXi]	Independent mixture mass fractions m_i/m close to the connection point if m_flow < 0 [kg/kg]
C_outflow[Medium.nC]	Properties c_i/m close to the connection point if m_flow < 0

Modelica.Fluid.Vessels.BaseClasses.VesselFluidPorts_b

Information

Parameters

Name	Description
replaceable package Medium	Medium model

Contents

Name	Description
m_flow	Mass flow rate from the connection point into the component [kg/s]
p	Thermodynamic pressure in the connection point [Pa]
h_outflow	Specific thermodynamic enthalpy close to the connection point if m_flow < 0 [J/kg]
Xi_outflow[Medium.nXi]	Independent mixture mass fractions m_i/m close to the connection point if m_flow < 0 [kg/kg]
C_outflow[Medium.nC]	Properties c_i/m close to the connection point if m_flow < 0