This package contains models for fans and pumps. The same models are used for fans or pumps.
The models use performance curves that compute pressure rise, electrical power draw and efficiency as a function of the volume flow rate and the speed. These performance curves are described in Buildings.Fluid.Movers.BaseClasses.Characteristics.
The models Buildings.Fluid.Movers.FlowMachine_y and Buildings.Fluid.Movers.FlowMachine_Nrpm take as an input either a control signal between 0 and 1, or the rotational speed in units of [1/min]. From this input and the current flow rate, they compute the pressure raise. This pressure raise is computed using user-provided list of operating points that defines the fan or pump curve at full speed. For other speeds, similarity laws are used to scale the performance curves, as described in Buildings.Fluid.Movers.BaseClasses.Characteristics.pressure.
The models Buildings.Fluid.Movers.FlowMachine_dp and Buildings.Fluid.Movers.FlowMachine_m_flow take as an input the pressure difference or the mass flow rate. This pressure difference or mass flow rate will be provided by the fan or pump, i.e., the fan or pump has idealized perfect control and infinite capacity. These two models do not have a performance curve for the flow characteristics. The reason for not using a performance curve for the flow characteristics is that
All models compute the motor power draw P_{ele}, the hydraulic power input W_{hyd}, the flow work W_{flo} and the heat dissipated into the medium Q. Based on the first law, the flow work is
W_{flo} = | V Δp |.
The heat dissipated into the medium is as follows:
If the motor is cooled by the fluid, as indicated by
motorCooledByFluid=true
, then the heat dissipated into the medium is
Q = P_{ele} - W_{flo}.
If motorCooledByFluid=false
, then the motor is outside the fluid stream,
and only the shaft, or hydraulic, work W_{hyd} enters the thermodynamic
control volume. Hence,
Q = Q_{hyd} - W_{flo}.
The efficiencies are computed as
η = W_{flo} ⁄ P_{ele} = η_{hyd} η_{mot}
η_{hyd} = W_{flo} ⁄ W_{hyd}
η_{mot} = W_{hyd} ⁄ P_{ele}
where η_{hyd} is the hydraulic efficiency, η_{mot} is the motor efficiency and Q is the heat released by the motor.
If use_powerCharacteristic=true
,
then a set of data points for the power P_{ele} for different
volume flow rates at full speed needs to be provided by the user.
Using the flow work W_{flo} and the electrical power input
P_{ele}, the total efficiency is computed as
η = W_{flo} ⁄ P_{ele},
√η_{hyd} = √η_{mot} = η.
However, ifuse_powerCharacteristic=false
, then
performance data for
η_{hyd} and
η_{mot} need to be provided by the user, and hence
the model computes
η = η_{hyd} η_{mot}
P_{ele} = W_{flo} ⁄ η.
The efficiency data for the motor are a list of points
r_{V} and η_{mot},
where r_{V} is the ratio of actual volume flow rate divided by the
maximum volume flow rate V_flow_max
,
which is the volume flow rate at full speed and zero pressure raise.
The maximum flow rate V_flow_max
is obtained as follows:
The models
Buildings.Fluid.Movers.FlowMachine_y and
Buildings.Fluid.Movers.FlowMachine_Nrpm set
V_flow_max = V_flow(dp=0, r_N=1);
where r_N
is the ratio of actual to nominal speed.
Since
Buildings.Fluid.Movers.FlowMachine_dp and
Buildings.Fluid.Movers.FlowMachine_m_flow
do not have a flow versus pressure performance curve, the parameter
V_flow_max
is assigned in these two models as
V_flow_max = m_flow_nominal/rho_nominal,
where m_flow_nominal
is the maximum flow rate, which needs to be
provided by the user as a parameter for these models, and rho_nominal
is the
density at the nominal operating point.
All models can be configured to have a fluid volume at the low-pressure side. Adding such a volume sometimes helps the solver to find a solution during initialization and time integration of large models.
If motorCooledByFluid=true
, then
the enthalpy change between the inlet and outlet fluid port is equal
to the electrical power P_{ele} that is consumed by the component.
Otherwise, it is equal to the hydraulic work W_{hyd}.
The parameter addPowerToMedium
, which is by default set to
true
, can be used to simplify the equations.
If it is set to false
, then no enthalpy change occurs between
inlet and outlet other than the flow work W_{flo}.
This can lead to simpler equations, but the temperature raise across the component
will be underestimated, in particular for fans.
For a detailed description of the models with names FlowMachine_*
,
see their base class
Buildings.Fluid.Movers.BaseClasses.PartialFlowMachine.
The model Buildings.Fluid.Movers.FlowMachinePolynomial is in this package for compatibility with older versions of this library. It is recommended to use the other models as they optionally allow use of a medium volume that provides state variables which are needed in some models when the flow rate is zero.
The models with names FlowMachine_*
have similar parameters than the
models in the package Modelica.Fluid.Machines.
However, the models in this package differ primarily in the following points:
Modelica.Fluid
restrict the number of revolutions, and hence the flow
rate, to be non-zero.
port_b
.
medium.d
. Therefore, for fans, head would be converted to pressure using the density of air. However, for fans, manufacturers typically publish the head in millimeters water (mmH20). Therefore, to avoid confusion when using these models with media other than water,
we changed the models to use total pressure in Pascals instead of head in meters.
Extends from Modelica.Icons.Info (Icon for general information packages).