Modelica.Fluid.Machines.BaseClasses

Base classes used in the Machines package (only of interest to build new component models)

Information

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

Package Content

Name Description
Modelica.Fluid.Machines.BaseClasses.PartialPump PartialPump Base model for centrifugal pumps
Modelica.Fluid.Machines.BaseClasses.PumpCharacteristics PumpCharacteristics Functions for pump characteristics
Modelica.Fluid.Machines.BaseClasses.PumpMonitoring PumpMonitoring Monitoring of pump operation

Modelica.Fluid.Machines.BaseClasses.PartialPump 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), Modelica.Fluid.Interfaces.PartialLumpedVolume (Lumped volume with mass and energy balance).

Parameters

NameDescription
replaceable package MediumMedium in the component
Characteristics
nParallelNumber of pumps in parallel
replaceable function flowCharacteristicHead vs. V_flow characteristic at nominal speed and density
N_nominalNominal rotational speed for flow characteristic [rev/min]
rho_nominalNominal fluid density for characteristic [kg/m3]
use_powerCharacteristicUse powerCharacteristic (vs. efficiencyCharacteristic)
replaceable function powerCharacteristicPower consumption vs. V_flow at nominal speed and density
replaceable function efficiencyCharacteristicEfficiency vs. V_flow at nominal speed and density
Custom Parameters
fluidVolumeVolume [m3]
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
checkValve= true to prevent reverse flow
VVolume inside the pump [m3]
Dynamics
energyDynamicsFormulation of energy balance
massDynamicsFormulation of mass balance
Heat transfer
use_HeatTransfer= true to use a HeatTransfer model, e.g., for a housing
replaceable model HeatTransferWall heat transfer
Initialization
p_a_startGuess value for inlet pressure [Pa]
p_b_startGuess value for outlet pressure [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
p_startStart value of pressure [Pa]
use_T_start= true, use T_start, otherwise h_start
T_startStart value of temperature [K]
h_startStart 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
Diagnostics
replaceable model MonitoringOptional pump monitoring

Connectors

NameDescription
heatPort 
Characteristics
replaceable function flowCharacteristicHead vs. V_flow characteristic at nominal speed and density
replaceable function powerCharacteristicPower consumption vs. V_flow at nominal speed and density
replaceable function efficiencyCharacteristicEfficiency vs. V_flow at nominal speed and density
Assumptions
Heat transfer
replaceable model HeatTransferWall heat transfer
Advanced
Diagnostics
replaceable model MonitoringOptional pump monitoring
Automatically generated Thu Dec 19 17:20:10 2019.