modelHeater
Idealized model for heater containing heat capacity of heat exchanger
Extends from Components.BaseClasses.PartialHeater (BaseClass for heat exchangers in air handling units).
Information
This model provides a idealized heater. The model considers the convective heat transfer from the heat transfer surface in the air stream. Moreover the heat capacity of the heating surface and the housing of the heat exchanger is considered.
Heat transfer model:
The model assumes a heat transfer in a plane gap. Hence the convective heat transfer coefficient is calculated using the Nusselt-correlation for a plane gap as described in the VDI-Wärmeatlas 2013 (p.800, eq. 45).
Num = 7.55 + (0.024 {Re Pr dh ⁄ l}1.14) ⁄ (1 + 0.0358 {Re Pr dh ⁄ l}0.64 Pr0.17)
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | use_T_set (from PartialHeater) | false | if true, a set temperature is used to calculate the necessary heat flow rate |
| Modelica.Units.SI.HeatFlowRate | Q_flow_nominal (from PartialHeater) | 45E3 | maximum heat output of heater at design point. Only used, if use_T_set = true |
| Advanced | |||
| Modelica.Units.SI.SpecificHeatCapacity | cpAir (from PartialComponent) | 1006 | specific heat capacity of dry air |
| Modelica.Units.SI.SpecificHeatCapacity | cpSteam (from PartialComponent) | 1860 | specific heat capacity of steam |
| Modelica.Units.SI.Density | rhoAir (from PartialComponent) | 1.2 | Density of air |
| Nominal conditions | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal (from PartialComponent) | nominal mass flow rate | |
| Modelica.Units.SI.PressureDifference | dp_nominal (from PartialComponent) | pressure drop at nominal mass flow rate | |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealInput | mAirIn_flow (from PartialComponent) | mass flow rate of incoming air | |
| Modelica.Blocks.Interfaces.RealInput | TAirIn (from PartialComponent) | Temperature of incoming air | |
| Modelica.Blocks.Interfaces.RealInput | XAirIn (from PartialComponent) | absolute humidity of incoming air | |
| Modelica.Blocks.Interfaces.RealOutput | mAirOut_flow (from PartialComponent) | mass flow rate of outgoing air | |
| Modelica.Blocks.Interfaces.RealOutput | TAirOut (from PartialComponent) | temperature of outgoing air | |
| Modelica.Blocks.Interfaces.RealOutput | XAirOut (from PartialComponent) | absolute humidity of outgoing air | |
| Modelica.Blocks.Interfaces.RealOutput | dp (from PartialComponent) | pressure difference | |
| Modelica.Blocks.Interfaces.RealInput | T_set (from PartialHeater) | ||
| Modelica.Blocks.Interfaces.RealOutput | Q_flow (from PartialHeater) | heat flow rate | |
| Modelica.Blocks.Interfaces.RealInput | u (from PartialHeater) | input connector scaling heat flow rate [0..1] |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.SpecificEnthalpy | hAirIn (from PartialComponent) | specific enthalpy of incoming air | |
| Modelica.Units.SI.SpecificEnthalpy | hAirOut (from PartialComponent) | specific enthalpy of outgoing air | |
| PartialPressureDrop | partialPressureDrop (from PartialHeater) |
Revisions
- April, 2019, by Martin Kremer:
First implementation.