modelFanBase
Extends from Icons.Gas.Fan.
Information
This is the base model for the FanMech fan model.
The model describes a fan, or a group of Np identical fans, with optional blade angle regulation. The fan model is based on the theory of kinematic similarity: the fan characteristics are given for nominal operating conditions (rotational speed and fluid density), and then adapted to actual operating condition, according to the similarity equations.
In order to avoid singularities in the computation of the outlet enthalpy at zero flowrate, the thermal capacity of the fluid inside the fan body can be taken into account.
The model can either support reverse flow conditions or include a built-in check valve to avoid flow reversal.
Modelling options
The nominal flow characteristic (specific energy vs. volume flow rate) is given by the the replaceable function flowCharacteristic. If the blade angles are fixed, it is possible to use implementations which ignore the bladePos input.
The fan energy balance can be specified in two alternative ways:
- usePowerCharacteristic = 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.
- usePowerCharacteristic = 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.
Several functions are provided in the package Functions.FanCharacteristics 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.
If the in_Np input connector is wired, it provides the number of fans in parallel; otherwise, Np0 parallel fans are assumed.
It is possible to take into account the heat capacity of the fluid inside the fan by specifying its volume V at nominal conditions; this is necessary 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 a fast state variable in the model.
The CheckValve parameter determines whether the fan has a built-in check valve or not.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | Np0 | 1 | Nominal number of fans in parallel |
| SI.Volume | V | 0 | Fan Internal Volume |
| Boolean | CheckValve | false | Reverse flow stopped |
| Boolean | allowFlowReversal | system.allowFlowReversal | = true to allow flow reversal, false restricts to design direction |
| SI.VolumeFlowRate | q_single0 | w0/(Np0*rho0) | Nominal volume flow rate (single fan) |
| SI.SpecificEnergy | H0 | dp0/(rho0) | Nominal specific energy |
| Real | dH_dq_start | if useFlowModel then flowModel.dH_dq(q_single_start, bladePos_start) else dH_dq(q_single_start, bladePos_start) | Derivative of specific energy w.r.t. volume flow at start conditions |
| Real | dH_dn_start | 2*H_start/n_start - dH_dq_start*q_single_start/n_start | Derivative of flow characteristic w.r.t. fan speed at start conditions |
| SI.Power | W_eps | 1e-8 | Small coefficient to avoid numerical singularities |
| NonSI.AngularVelocity_rpm | n_eps | 1e-6 | |
| Characteristic curves | |||
| Boolean | useFlowModel | false | Use function from replaceable model for flow characteristic |
| Boolean | usePowerCharacteristic | false | Use powerCharacteristic (vs. efficiencyCharacteristic) |
| Nominal values | |||
| SI.PerUnit | bladePos0 | 1 | Nominal blade position |
| Medium.Density | rho0 | 1.229 | Nominal Gas Density |
| NonSI.AngularVelocity_rpm | n0 | 1500 | Nominal rotational speed |
| Medium.MassFlowRate | w0 | Nominal mass flow rate | |
| SI.Pressure | dp0 | Nominal pressure increase | |
| Initialisation | |||
| SI.VolumeFlowRate | q_single_start | q_single0 | Volume Flow Rate Start Value (single pump) |
| Medium.SpecificEnthalpy | hstart | 1e5 | Fluid Specific Enthalpy Start Value |
| Medium.Density | rho_start | rho0 | Inlet Density start value |
| NonSI.AngularVelocity_rpm | n_start | n0 | Rotational speed start value |
| SI.SpecificEnergy | H_start | H0 | Specific energy start value |
| SI.PerUnit | bladePos_start | bladePos0 | Blade position start value |
| Choices.Init.Options | initOpt | system.initOpt | Initialisation option |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| FlangeA | infl | ||
| FlangeB | outfl | ||
| Modelica.Blocks.Interfaces.IntegerInput | in_Np | Number of parallel pumps | |
| Modelica.Blocks.Interfaces.RealInput | in_bladePos |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.BaseProperties | inletFluid | Fluid properties at the inlet | |
| ThermoPower.System | system | System wide properties | |
| Medium.MassFlowRate | w_single | Mass flow rate (single fan) | |
| Medium.MassFlowRate | w | Np*w_single | Mass flow rate (total) |
| SI.VolumeFlowRate | q_single | Volume flow rate (single fan) | |
| SI.VolumeFlowRate | q | Np*q_single | Volume flow rate (totale) |
| SI.PressureDifference | dp | Outlet pressure minus inlet pressure | |
| SI.SpecificEnergy | H | Specific energy | |
| Medium.SpecificEnthalpy | h | Fluid specific enthalpy | |
| Medium.SpecificEnthalpy | hin | Enthalpy of entering fluid | |
| Medium.SpecificEnthalpy | hout | Enthalpy of outgoing fluid | |
| Units.LiquidDensity | rho | Gas density | |
| Medium.Temperature | Tin | Gas inlet temperature | |
| NonSI.AngularVelocity_rpm | n | Shaft r.p.m. | |
| Real | bladePos | Blade position | |
| Integer | Np | Number of fans in parallel | |
| SI.Power | W_single | Power Consumption (single fan) | |
| SI.Power | W | Np*W_single | Power Consumption (total) |
| SI.PerUnit | eta | Fan efficiency | |
| Real | s | Auxiliary Variable | |
| FlowCharacteristicModel | flowModel | Model for flow characteristic function with static parameters |
Contents
| Name | Description |
|---|---|
 Medium | Medium model |
 flowCharacteristic | |
| FlowCharacteristicModel | |
 powerCharacteristic | |
 efficiencyCharacteristic | |
| dH_dqprotected | Approximated partial derivative of flow characteristic w.r.t. volume flow |
Revisions
- 10 Nov 2005
by Francesco Casella:
Adapted from the Water.PumpBase model.