modelHeatingRod
Extends from AixLib.Fluid.Interfaces.TwoPortHeatMassExchanger.
Information
Model for a heating rod.
This model adds heat in the amount of Q_flow = u Q_flow_nominal to the medium. The input signal u and the nominal heat flow rate Q_flow_nominal can be positive or negative. A positive value of Q_flow means heating, and negative means cooling.
The outlet conditions at port_a are not affected by this model, other than for a possible pressure difference due to flow friction.
Optionally, this model can have a flow resistance. Set dp_nominal = 0 to disable the flow friction calculation.
For a model that uses as an input the fluid temperature leaving at port_b, use AixLib.Fluid.HeatExchangers.PrescribedOutlet
As output, the electrical energy required to supply Q_flow is calculated using the efficiency which is a parameter of the model.
Lastly, the number of times the heating rod switches on may be used as an output.
Limitations
This model does not affect the humidity of the air. Therefore, if used to cool air below the dew point temperature, the water mass fraction will not change.
Validation
The model has been validated against the analytical solution in the example AixLib.Fluid.HeatExchangers.Validation.HeaterCooler_u.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.HeatFlowRate | Q_flow_nominal | Heat flow rate at u=1, positive for heating | |
| Modelica.Units.SI.Volume | V | m_flow_nominal*tau/rho_default | Volume of heat exchanger |
| Real | eta | Efficiency of the heating rod | |
| Advanced › Diagnostics | |||
| Boolean | use_countNumSwi | true | Turn the counting of the number of heating rod uses on or off. |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealInput | u | Control input | |
| Modelica.Blocks.Interfaces.RealOutput | Pel | Electrical power used to provide current heat flow | |
| Modelica.Blocks.Math.Gain | gai_eta | Divide efficiency | |
| Modelica.Blocks.MathInteger.TriggeredAdd | triggeredAdd | To count on-off cycles | |
| Modelica.Blocks.Sources.IntegerConstant | integerConstant | ||
| Modelica.Blocks.Interfaces.IntegerOutput | numSwi | Number of on switches | |
| Modelica.Blocks.Logical.GreaterThreshold | greaterThreshold |
Revisions
- May 5, 2021, by Fabian Wuellhorst:
Added model.
This is for AixLib, #1092.