.Modelica.Fluid.Machines.BaseClasses.PartialPump .Modelica.Fluid.Machines.BaseClasses.PartialPumpThis 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).
| Name | Description |
|---|---|
 flowCharacteristic |
Head vs. V_flow characteristic at nominal speed and density |
|
powerCharacteristic |
Power consumption vs. V_flow at nominal speed and density |
|
efficiencyCharacteristic |
|
 HeatTransfer |
|
 Monitoring |