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

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:

• use_powerCharacteristic = false (default option): the replaceable function efficiencyCharacteristic (efficiency vs. volume flow rate in nominal conditions) is used to determine the efficiency, and then the power consumption. The default is a constant efficiency of 0.8.
• use_powerCharacteristic = true: the replaceable function powerCharacteristic (power consumption vs. volume flow rate in nominal conditions) is used to determine the power consumption, and then the efficiency. Use powerCharacteristic to specify a non-zero power consumption for zero flow rate.

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).

allowFlowReversal	Value: system.allowFlowReversal Type: Boolean Description: = true to allow flow reversal, false restricts to design direction (port_a -> port_b)
energyDynamics	Value: Types.Dynamics.SteadyState Type: Dynamics Description: Formulation of energy balance
massDynamics	Value: Types.Dynamics.SteadyState Type: Dynamics Description: Formulation of mass balance
substanceDynamics	Value: massDynamics Type: Dynamics Description: Formulation of substance balance
traceDynamics	Value: massDynamics Type: Dynamics Description: Formulation of trace substance balance
p_start	Value: p_b_start Type: AbsolutePressure (Pa) Description: Start value of pressure
use_T_start	Value: true Type: Boolean Description: = true, use T_start, otherwise h_start
T_start	Value: if use_T_start then system.T_start else Medium.temperature_phX(p_start, h_start, X_start) Type: Temperature (K) Description: Start value of temperature
h_start	Value: if use_T_start then Medium.specificEnthalpy_pTX(p_start, T_start, X_start) else Medium.h_default Type: SpecificEnthalpy (J/kg) Description: Start value of specific enthalpy
X_start	Value: Medium.X_default Type: MassFraction[Medium.nX] (kg/kg) Description: Start value of mass fractions m_i/m
C_start	Value: Medium.C_default Type: ExtraProperty[Medium.nC] Description: Start value of trace substances
p_a_start	Value: system.p_start Type: AbsolutePressure (Pa) Description: Guess value for inlet pressure
p_b_start	Value: p_a_start Type: AbsolutePressure (Pa) Description: Guess value for outlet pressure
m_flow_start	Value: system.m_flow_start Type: MassFlowRate (kg/s) Description: Guess value of m_flow = port_a.m_flow
V_flow_single_init	Value: m_flow_start / rho_nominal / nParallel Type: VolumeFlowRate (m³/s) Description: Used for simplified initialization model
delta_head_init	Value: flowCharacteristic(V_flow_single_init * 1.1) - flowCharacteristic(V_flow_single_init) Type: Position (m) Description: Delta head for a 10% increase of flow at the initialization point
nParallel	Value: 1 Type: Integer Description: Number of pumps in parallel
N_nominal	Value: Type: AngularVelocity_rpm (rev/min) Description: Nominal rotational speed for flow characteristic
rho_nominal	Value: Medium.density_pTX(Medium.p_default, Medium.T_default, Medium.X_default) Type: Density (kg/m³) Description: Nominal fluid density for characteristic
use_powerCharacteristic	Value: false Type: Boolean Description: Use powerCharacteristic (vs. efficiencyCharacteristic)
checkValve	Value: false Type: Boolean Description: = true to prevent reverse flow
V	Value: 0 Type: Volume (m³) Description: Volume inside the pump
use_HeatTransfer	Value: false Type: Boolean Description: = true to use a HeatTransfer model, e.g., for a housing
g	Value: system.g Type: Acceleration (m/s²)
show_NPSHa	Value: false Type: Boolean Description: obsolete -- remove modifier and specify Monitoring for NPSH instead

fluidVolume	Default Value: V Type: Volume (m³) Description: Volume