Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses
Package with base classes for Buildings.Fluid.HeatExchangers.RadiantSlabs
Information
This package contains base classes that are used to construct the models in Buildings.Fluid.HeatExchangers.RadiantSlabs.
Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).
Package Content
| Name | Description |
|---|---|
 HeatFlowRateMultiplier
|
Multiplies the heat flow rate |
 PipeToSlabConductance
|
Convective heat transfer in pipes and fictitious resistance to average slab temperature |
 Slab
|
Base class for radiant slab |
 Functions
|
Functions for convective heat transfer |
Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.HeatFlowRateMultiplier
Multiplies the heat flow rate
Information
This model multiplies the heat flow rate so that
0 = port_b.Q_flow + k * port_Q.m_flow.
The temperature remains unchanged. Therefore, this model does not conserve energy. It is used in Buildings.Fluid.HeatExchangers.RadiantSlabs.ParallelCircuitsSlab to avoid having to instanciate multiple slab models in parallel, with each having the same mass flow rate and temperatures.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | k | Gain for mass flow rate |
Connectors
| Type | Name | Description |
|---|---|---|
| HeatPort_a | port_a | |
| HeatPort_b | port_b |
Modelica definition
model HeatFlowRateMultiplier "Multiplies the heat flow rate"
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a port_a;
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_b port_b;
parameter Real k "Gain for mass flow rate";
initial equation
assert( k > Modelica.Constants.small or -k < -Modelica.Constants.small,
"Gain must not be zero. Received k = " + String(k));
equation
// Energy balance. (Energy is not conserved by this model!)
port_b.Q_flow = -k*port_a.Q_flow;
port_a.T = port_b.T;
end HeatFlowRateMultiplier;
Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.PipeToSlabConductance
Convective heat transfer in pipes and fictitious resistance to average slab temperature
Information
Model to compute the convective heat transfer inside a straight pipe. The convective heat transfer coefficient is computed as a function of the mass flow rate using the function Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_overall_KC.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | Modelica.Media.Interfaces.Pa... | Medium in the component | |
| HeatTransfer | heatTransfer | Buildings.Fluid.HeatExchange... | Model for heat transfer between fluid and slab |
| Area | APip | Pipe inside surface area [m2] | |
| kc_overall_IN_con | kc_IN_con | Parameters for convective heat transfer calculation | |
| ThermalResistance | RFic | Average fictitious thermal resistance between pipe surface and plane that contains pipe [K/W] | |
| ThermalResistance | RWal | Thermal resistance through the pipe wall [K/W] | |
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable package Medium | Medium in the component | |
| input RealInput | m_flow | Fluid mass flow rate from port_a to port_b [kg/s] |
| input RealInput | T_a | Temperature at fluid port_a [K] |
| input RealInput | T_b | Temperature at fluid port_b [K] |
| HeatPort_a | solid | Heat port at solid interface |
| HeatPort_b | fluid | Heat port at fluid interface |
Modelica definition
model PipeToSlabConductance
"Convective heat transfer in pipes and fictitious resistance to average slab temperature"
replaceable package Medium =
Modelica.Media.Interfaces.PartialMedium "Medium in the component";
parameter Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.HeatTransfer
heatTransfer=
Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.HeatTransfer.EpsilonNTU
"Model for heat transfer between fluid and slab";
parameter Modelica.SIunits.Area APip "Pipe inside surface area";
parameter kc_overall_IN_con
kc_IN_con "Parameters for convective heat transfer calculation";
Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_overall_IN_var
kc_IN_var(
cp=Medium.specificHeatCapacityCp(fluSta),
eta=Medium.dynamicViscosity(fluSta),
lambda=Medium.thermalConductivity(fluSta),
rho=Medium.density(fluSta),
m_flow=m_flow) "Variables for convective heat transfer calculation";
parameter Modelica.SIunits.ThermalResistance RFic
"Average fictitious thermal resistance between pipe surface and plane that contains pipe";
parameter Modelica.SIunits.ThermalResistance RWal
"Thermal resistance through the pipe wall";
parameter Modelica.SIunits.MassFlowRate m_flow_nominal
"Nominal mass flow rate";
Modelica.Blocks.Interfaces.RealInput m_flow(unit="kg/s")
"Fluid mass flow rate from port_a to port_b";
Modelica.Blocks.Interfaces.RealInput T_a(unit="K")
"Temperature at fluid port_a";
Modelica.Blocks.Interfaces.RealInput T_b(unit="K")
"Temperature at fluid port_b";
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a solid
"Heat port at solid interface";
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_b fluid
"Heat port at fluid interface";
Modelica.SIunits.TemperatureDifference dT "= solid.T - fluid.T";
Modelica.SIunits.CoefficientOfHeatTransfer hCon
"Convective heat transfer coefficient";
Modelica.SIunits.ThermalResistance RTot
"Thermal resistance between the fluid and the fictious plane of heat transfer";
Modelica.SIunits.HeatFlowRate Q_flow "Heat flow rate from solid -> fluid";
// The records kc_overall_IN_con and kc_turbulent_IN_con are implemented
// because in the Modelica Standard Library 3.2.2, they have a bug
// that causes the pedantic model check in Dymola 2017 beta3 to fail.
record kc_overall_IN_con
"Input record for function kc_overall and kc_overall_KC"
//choices
Modelica.Fluid.Dissipation.Utilities.Types.HeatTransferBoundary target=Modelica.Fluid.Dissipation.Utilities.Types.HeatTransferBoundary.UWTuDFF
"Choice of heat transfer boundary condition";
extends kc_turbulent_IN_con;
end kc_overall_IN_con;
protected
record kc_turbulent_IN_con
"Input record for function kc_turbulent and kc_turbulent_KC"
extends Modelica.Fluid.Dissipation.Utilities.Records.HeatTransfer.StraightPipe;
Modelica.Fluid.Dissipation.Utilities.Types.Roughness roughness=Modelica.Fluid.Dissipation.Utilities.Types.Roughness.Considered
"Choice of considering surface roughness";
Modelica.SIunits.Length K=0 "Roughness (average height of surface asperities)";
end kc_turbulent_IN_con;
Medium.ThermodynamicState fluSta = Medium.setState_pTX(p=Medium.p_default, T=fluid.T, X=Medium.X_default)
"State of the medium";
Modelica.SIunits.SpecificHeatCapacity c_p = Medium.specificHeatCapacityCp(fluSta)
"Specific heat capacity of the fluid";
equation
hCon = Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_overall_KC(
IN_con=kc_IN_con, IN_var=kc_IN_var);
RTot = 1/hCon/APip + RFic + RWal;
if heatTransfer == Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.HeatTransfer.EpsilonNTU then
Q_flow = Functions.heatFlowRate(T_a=T_a,
T_b=T_b,
T_s=solid.T,
T_f=fluid.T,
c_p=c_p,
UA=1/RTot,
m_flow=m_flow,
m_flow_nominal=m_flow_nominal);
else
Q_flow = dT/RTot;
end if;
dT = solid.T - fluid.T;
solid.Q_flow = Q_flow;
fluid.Q_flow = -Q_flow;
end PipeToSlabConductance;
Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Slab
Base class for radiant slab
Information
This partial model is used to construct radiant slab models with one circuit or with multiple parallel circuits.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| SystemType | sysTyp | Radiant system type | |
| Distance | disPip | Pipe distance [m] | |
| Generic | pipe | Record for pipe geometry and material | |
| Construction | |||
| Generic | layers | layers(nLay(min=2)) | Definition of the construction, which must have at least two material layers |
| Integer | iLayPip | Number of the interface layer in which the pipes are located | |
| Initialization | |||
| Construction | |||
| Boolean | steadyStateInitial | false | =true initializes dT(0)/dt=0, false initializes T(0) at fixed temperature using T_a_start, T_c_start and T_b_start |
| Temperature | T_a_start | 293.15 | Initial temperature at surf_a, used if steadyStateInitial = false [K] |
| Temperature | T_b_start | 293.15 | Initial temperature at surf_b, used if steadyStateInitial = false [K] |
| Dynamics | |||
| Boolean | stateAtSurface_a | true | =true, a state will be at the surface a |
| Boolean | stateAtSurface_b | true | =true, a state will be at the surface b |
Connectors
| Type | Name | Description |
|---|---|---|
| HeatPort_a | surf_a | Heat port at construction surface |
| HeatPort_a | surf_b | Heat port at construction surface |
Modelica definition
partial model Slab "Base class for radiant slab"
parameter Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.SystemType
sysTyp "Radiant system type";
parameter Modelica.SIunits.Distance disPip "Pipe distance";
parameter Buildings.Fluid.Data.Pipes.Generic pipe
"Record for pipe geometry and material";
parameter HeatTransfer.Data.OpaqueConstructions.Generic layers(nLay(min=2))
"Definition of the construction, which must have at least two material layers";
parameter Boolean steadyStateInitial=false
"=true initializes dT(0)/dt=0, false initializes T(0) at fixed temperature using T_a_start, T_c_start and T_b_start";
parameter Integer iLayPip(min=1)
"Number of the interface layer in which the pipes are located";
parameter Modelica.SIunits.Temperature T_a_start=293.15
"Initial temperature at surf_a, used if steadyStateInitial = false";
parameter Modelica.SIunits.Temperature T_b_start=293.15
"Initial temperature at surf_b, used if steadyStateInitial = false";
parameter Boolean stateAtSurface_a=true
"=true, a state will be at the surface a";
parameter Boolean stateAtSurface_b=true
"=true, a state will be at the surface b";
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a surf_a
"Heat port at construction surface";
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a surf_b
"Heat port at construction surface";
end Slab;
Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.PipeToSlabConductance.kc_overall_IN_con
Input record for function kc_overall and kc_overall_KC
Information
This record is used as input record for the heat transfer function kc_overall and kc_overall_KC.
Implementation
This record is identical to Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_overall_IN_con, except that it extends from a local implementation of Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_turbulent_IN_con in order to correct the bug reported in MSL ticket 2066.
Extends from kc_turbulent_IN_con (Input record for function kc_turbulent and kc_turbulent_KC).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Choices | |||
| HeatTransferBoundary | target | Modelica.Fluid.Dissipation.U... | Choice of heat transfer boundary condition |
| Roughness | roughness | Modelica.Fluid.Dissipation.U... | Choice of considering surface roughness |
| Straight pipe | |||
| Diameter | d_hyd | 0.1 | Hydraulic diameter [m] |
| Length | L | 1 | Length [m] |
| Length | K | 0 | Roughness (average height of surface asperities) [m] |
Modelica definition
record kc_overall_IN_con
"Input record for function kc_overall and kc_overall_KC"
//choices
Modelica.Fluid.Dissipation.Utilities.Types.HeatTransferBoundary target=Modelica.Fluid.Dissipation.Utilities.Types.HeatTransferBoundary.UWTuDFF
"Choice of heat transfer boundary condition";
extends kc_turbulent_IN_con;
end kc_overall_IN_con;
Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.PipeToSlabConductance.kc_turbulent_IN_con
Input record for function kc_turbulent and kc_turbulent_KC
Information
This record is used as input record for the heat transfer function kc_turbulent and kc_turbulent_KC.
Implementation
This record is identical to Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_turbulent_IN_con, except that the bug reported in MSL ticket 2066.
Extends from Modelica.Fluid.Dissipation.Utilities.Records.HeatTransfer.StraightPipe (Input for straight pipe).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Straight pipe | |||
| Diameter | d_hyd | 0.1 | Hydraulic diameter [m] |
| Length | L | 1 | Length [m] |
| Length | K | 0 | Roughness (average height of surface asperities) [m] |
| Choices | |||
| Roughness | roughness | Modelica.Fluid.Dissipation.U... | Choice of considering surface roughness |
Modelica definition
record kc_turbulent_IN_con
"Input record for function kc_turbulent and kc_turbulent_KC"
extends Modelica.Fluid.Dissipation.Utilities.Records.HeatTransfer.StraightPipe;
Modelica.Fluid.Dissipation.Utilities.Types.Roughness roughness=Modelica.Fluid.Dissipation.Utilities.Types.Roughness.Considered
"Choice of considering surface roughness";
Modelica.SIunits.Length K=0 "Roughness (average height of surface asperities)";
end kc_turbulent_IN_con;