Package Modelica.​Fluid.​Machines.​BaseClasses
Base classes used in the Machines package (only of interest to build new component models)

Information

This icon shall be used for a package/library that contains base models and classes, respectively.

Extends from Modelica.​Icons.​BasesPackage (Icon for packages containing base classes).

Package Contents

NameDescription
PartialPumpBase model for centrifugal pumps
PumpCharacteristicsFunctions for pump characteristics
PumpMonitoringMonitoring of pump operation

Partial Model Modelica.​Fluid.​Machines.​BaseClasses.​PartialPump
Base model for centrifugal pumps

Information

This is the base model for pumps.

The model describes a centrifugal pump, or a group of nParallel identical pumps. The pump model is based on the theory of kinematic similarity: the pump characteristics are given for nominal operating conditions (rotational speed and fluid density), and then adapted to actual operating condition, according to the similarity equations.

Pump characteristics

The nominal hydraulic characteristic (head vs. volume flow rate) is given by the replaceable function flowCharacteristic.

The pump energy balance can be specified in two alternative ways:

Several functions are provided in the package PumpCharacteristics to specify the characteristics as a function of some operating points at nominal conditions.

Depending on the value of the checkValve parameter, the model either supports reverse flow conditions, or includes a built-in check valve to avoid flow reversal.

It is possible to take into account the mass and energy storage of the fluid inside the pump by specifying its volume V, and by selecting appropriate dynamic mass and energy balance assumptions (see below); this is recommended to avoid singularities in the computation of the outlet enthalpy in case of zero flow rate. If zero flow rate conditions are always avoided, this dynamic effect can be neglected by leaving the default value V = 0, thus avoiding fast state variables in the model.

Dynamics options

Steady-state mass and energy balances are assumed per default, neglecting the holdup of fluid in the pump; this configuration works well if the flow rate is always positive. Dynamic mass and energy balance can be used by setting the corresponding dynamic parameters. This is recommended to avoid singularities at zero or reversing mass flow rate. If the initial conditions imply non-zero mass flow rate, it is possible to use the SteadyStateInitial condition, otherwise it is recommended to use FixedInitial in order to avoid undetermined initial conditions.

Heat transfer

The Boolean parameter use_HeatTransfer can be set to true if heat exchanged with the environment should be taken into account or to model a housing. This might be desirable if a pump with realistic powerCharacteristic for zero flow operates while a valve prevents fluid flow.

Diagnostics of Cavitation

The replaceable Monitoring submodel can be configured to PumpMonitoringNPSH, in order to compute the Net Positive Suction Head available and check for cavitation, provided a two-phase medium model is used (see Advanced tab).

Extends from Modelica.​Fluid.​Interfaces.​PartialTwoPort (Partial component with two ports) and Modelica.​Fluid.​Interfaces.​PartialLumpedVolume (Lumped volume with mass and energy balance).

Parameters

TypeNameDefaultDescription
BooleanallowFlowReversalsystem.​allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
AbsolutePressurep_a_startsystem.​p_startGuess value for inlet pressure
AbsolutePressurep_b_startp_a_startGuess value for outlet pressure
MassFlowRatem_flow_startsystem.​m_flow_startGuess value of m_flow = port_a.m_flow
final VolumeFlowRateV_flow_single_initm_flow_start / rho_nominal / nParallelUsed for simplified initialization model
final Heightdelta_head_initflowCharacteristic(V_flow_single_init) - flowCharacteristic(0)Used for simplified initialization model
IntegernParallel1Number of pumps in parallel
AngularVelocity_rpmN_nominal Nominal rotational speed for flow characteristic
Densityrho_nominalMedium.density_pTX(Medium.p_default, Medium.T_default, Medium.X_default)Nominal fluid density for characteristic
Booleanuse_powerCharacteristicfalseUse powerCharacteristic (vs. efficiencyCharacteristic)
BooleancheckValvefalse= true to prevent reverse flow
VolumeV0Volume inside the pump
DynamicsenergyDynamicsTypes.​Dynamics.​SteadyStateFormulation of energy balance
DynamicsmassDynamicsTypes.​Dynamics.​SteadyStateFormulation of mass balance
final DynamicssubstanceDynamicsmassDynamicsFormulation of substance balance
final DynamicstraceDynamicsmassDynamicsFormulation of trace substance balance
final AbsolutePressurep_startp_b_startStart value of pressure
Booleanuse_T_starttrue= true, use T_start, otherwise h_start
TemperatureT_startif use_T_start then system.T_start else Medium.temperature_phX(p_start, h_start, X_start)Start value of temperature
SpecificEnthalpyh_startif use_T_start then Medium.specificEnthalpy_pTX(p_start, T_start, X_start) else Medium.h_defaultStart value of specific enthalpy
MassFractionX_start[Medium.nX]Medium.​X_defaultStart value of mass fractions m_i/m
ExtraPropertyC_start[Medium.nC]Medium.​C_defaultStart value of trace substances
Booleanuse_HeatTransferfalse= true to use a HeatTransfer model, e.g., for a housing
final Accelerationgsystem.​g 
final Booleanshow_NPSHafalseobsolete -- remove modifier and specify Monitoring for NPSH instead

Connectors

TypeNameDescription
FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)
HeatPort_aheatPort 

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