modelRadiator_EN442
Extends from BuildSysPro.Systems.HVAC.Emission.Radiator.Components.CharacteristicEquation (Model for characteristic equation of a radiator (EN442)).
Information
Simple hot water radiator model for central heating system
Hypothesis and equations
This model is based on the characteristic equation (Qflow=Km DTN) described in the EN442 standard.
Depending on the model options, DT could be considered as followed:
- DT= T_HWR - Troom where Troom = Trad+Tconv/2 if
radEqua=BuildSysPro.BaseClasses.HeatTransfer.Components.BasedCharacteristicEquation1 - or 2 characteristic equations could be considered for radiative and convective heat transfers respectively : DTrad= T_HWR - Trad and DTconv= T_HWR - Tconv if
radEqua=BuildSysPro.BaseClasses.HeatTransfer.Components.BasedCharacteristicEquation2
Otherwise the model use common equations for energy balance and continuity equation (no mass accumulation).
Depending on the option useInertia, steady state or dynamic behaviour are computed. For dynamic computation, the energy balanced is calculated as :
This model does not considered a discretization along the fluid path.
This model relies also on an arithmetic mean temperature difference (AMTD), different from the theorical logarithmic mean temperature difference (LMTD) and should be used when the following condition is fulfilled :
Otherwise using AMTD leads to a deviation exceeding 10%.
Bibliography
This model was implemented following the EN442 standard and considering a single element.
Nilsson, P.E. and The Commtech Group, 2003. Achieving the Desired Indoor Climate: Energy Efficiency Aspects of System Design. Studentlitteratur AB.
Instructions for use
Connect the model to a distribution network through the WaterIn and WaterOut connectors.
Connect also the model to a thermal ambiance through the Conv and Rad heatports respectively for convective heat transfers and long wave radiation.
Known limits / Use precautions
The model is not discretized along the fluid path therefore in Dynamic mode, nominal operating conditions do not lead to the nominal heating power.
Validations
Simple validation based on operating point - Gilles Plessis 01/2016
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Licensed by EDF under a 3-clause BSD-license
Copyright © EDF 2009 - 2023
BuildSysPro version 3.6.0
Author : Gilles PLESSIS, EDF (2016)
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Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | Km (from CharacteristicEquation) | Pnom/DTnom^nNom | Km coefficient (sometimes refers as KS or UA coefficient) used in the Characteristic equation |
| EN442 - Nominal point | |||
| SI.EnergyFlowRate | Pnom (from CharacteristicEquation) | 411 | Nominal power for a DT=50 K, based on inlet temperature 75/65 |
| SI.TemperatureDifference | DTnom (from CharacteristicEquation) | 50 | Temperature difference (air to water) at nominal operating point |
| Real | nNom (from CharacteristicEquation) | 1.225 | Slope at nominal point |
| Real | FracRad (from CharacteristicEquation) | 0.35 | Radiative fraction of heat |
| Options | |||
| Boolean | useInertia | false | Steady state modelling of dynamics |
| Dynamic | |||
| SI.Mass | MediumMass | Mass of water | |
| SI.Mass | BodyMass | Radiator mass | |
| SI.SpecificHeatCapacity | cpBody | 500 | Specific heat capacity of the radiator body (ex. 500J/kg/K for cast iron) |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| BaseClasses.HeatTransfer.Interfaces.HeatPort_b | Rad (from CharacteristicEquation) | HeatPort for long wave radiation exchanges | |
| BaseClasses.HeatTransfer.Interfaces.HeatPort_b | Conv (from CharacteristicEquation) | HeatPort for convective heat transfers | |
| Modelica.Blocks.Interfaces.RealInput[2] | WaterIn | 1:Temp / 2:m_flow | |
| Modelica.Blocks.Interfaces.RealOutput[2] | WaterOut | 1:Temp / 2:m_flow |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| BuildSysPro.Systems.HVAC.Emission.Radiator.Components.BasedCharacteristicEquation1 | radEqua (from CharacteristicEquation) | ||
| SI.TemperatureDifference | DTlm | (WaterIn[1] - WaterOut[1])/Modelica.Math.log((WaterIn[1] - (Conv.T + Rad.T)/2)/(WaterOut[1] - (Conv.T + Rad.T)/2)) | Logaritmic mean temperature difference, given for information, EN442 being based on arithmetic mean temperature difference |
| SI.Temperature | T_HWR | Temperature of the hot water radiator |
Contents
| Name | Description |
|---|---|
 Medium |