LBL logo

Buildings.Fluid.HeatExchangers.RadiantSlabs

Package with radiant slab models

Information

This package contains models for radiant slabs with pipes or a capillary heat exchanger embedded in the construction.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name Description
Buildings.Fluid.HeatExchangers.RadiantSlabs.UsersGuide UsersGuide User's Guide
Buildings.Fluid.HeatExchangers.RadiantSlabs.ParallelCircuitsSlab ParallelCircuitsSlab Model of multiple parallel circuits of a radiant slab
Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab SingleCircuitSlab Model of a single circuit of a radiant slab
Buildings.Fluid.HeatExchangers.RadiantSlabs.Types Types Package with type definitions
Buildings.Fluid.HeatExchangers.RadiantSlabs.Examples Examples Collection of models that illustrate model use and test models
Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses BaseClasses Package with base classes for Buildings.Fluid.HeatExchangers.RadiantSlabs

Buildings.Fluid.HeatExchangers.RadiantSlabs.ParallelCircuitsSlab Buildings.Fluid.HeatExchangers.RadiantSlabs.ParallelCircuitsSlab

Model of multiple parallel circuits of a radiant slab

Buildings.Fluid.HeatExchangers.RadiantSlabs.ParallelCircuitsSlab

Information

This is a model of a radiant slab with pipes or a capillary heat exchanger embedded in the construction. The model is a composition of multiple models of Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab that are arranged in a parallel.

The parameter nCir declares the number of parallel flow circuits. Each circuit will have the same mass flow rate, and it is exposed to the same port variables for the heat port at the two surfaces, and for the flow inlet and outlet.

A typical model application is as follows: Suppose a large room has a radiant slab with two parallel circuits with the same pipe spacing and pipe length. Then, rather than using two instances of Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab, this system can be modeled using one instance of this model in order to reduce computing effort. See Buildings.Fluid.HeatExchangers.RadiantSlabs.Examples.SingleCircuitMultipleCircuitEpsilonNTU for an example that shows that the models give identical results.

Since this model is a parallel arrangment of nCir models of Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab, we refer to Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab for the model documentation.

See the user's guide for more information.

Implementation

To allow a better comment for the nominal mass flow rate, i.e., to specify that its value is for all circuits combined, this model does not inherit Buildings.Fluid.Interfaces.PartialTwoPortInterface.

Extends from Buildings.Fluid.Interfaces.PartialTwoPort (Partial component with two ports), Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Slab (Base class for radiant slab), Buildings.Fluid.Interfaces.LumpedVolumeDeclarations (Declarations for lumped volumes), Buildings.Fluid.Interfaces.TwoPortFlowResistanceParameters (Parameters for flow resistance for models with two ports).

Parameters

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
SystemTypesysTyp Radiant system type
DistancedisPip Pipe distance [m]
Genericpipe Record for pipe geometry and material
IntegernCir1Number of parallel circuits
IntegernSegif heatTransfer == Types.Hea...Number of volume segments in each circuit (along flow path)
LengthlengthA/disPip/nCirLength of the pipe of a single circuit [m]
HeatTransferheatTransferTypes.HeatTransfer.EpsilonNTUModel for heat transfer between fluid and slab
Construction
Genericlayers Definition of the construction, which must have at least two material layers
IntegeriLayPip Number of the interface layer in which the pipes are located
AreaA Surface area of radiant slab (all circuits combined) [m2]
Nominal condition
PressureDifferencedp_nominalModelica.Fluid.Pipes.BaseCla...Pressure difference [Pa]
MassFlowRatem_flow_nominal Nominal mass flow rate of all circuits combined [kg/s]
Assumptions
BooleanallowFlowReversaltrue= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Initialization
Construction
BooleansteadyStateInitialfalse=true initializes dT(0)/dt=0, false initializes T(0) at fixed temperature using T_a_start, T_c_start and T_b_start
TemperatureT_a_start293.15Initial temperature at surf_a, used if steadyStateInitial = false [K]
TemperatureT_b_start293.15Initial temperature at surf_b, used if steadyStateInitial = false [K]
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
TemperatureT_startMedium.T_defaultStart value of temperature [K]
MassFractionX_start[Medium.nX]Medium.X_defaultStart value of mass fractions m_i/m [kg/kg]
ExtraPropertyC_start[Medium.nC]fill(0, Medium.nC)Start value of trace substances
ExtraPropertyC_nominal[Medium.nC]fill(1E-2, Medium.nC)Nominal value of trace substances. (Set to typical order of magnitude.)
Dynamics
Equations
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state
DynamicsmassDynamicsenergyDynamicsType of mass balance: dynamic (3 initialization options) or steady state
RealmSenFac1Factor for scaling the sensible thermal mass of the volume
Flow resistance
BooleancomputeFlowResistancetrue=true, compute flow resistance. Set to false to assume no friction
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistancefalse= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM0.1Fraction of nominal flow rate where flow transitions to laminar
Advanced
MassFlowRatem_flow_small1E-4*abs(m_flow_nominal)Small mass flow rate of all circuits combined for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed

Connectors

TypeNameDescription
HeatPort_asurf_aHeat port at construction surface
HeatPort_asurf_bHeat port at construction surface

Modelica definition

model ParallelCircuitsSlab "Model of multiple parallel circuits of a radiant slab" extends Buildings.Fluid.Interfaces.PartialTwoPort( port_a(p(start=p_start, nominal=Medium.p_default)), port_b(p(start=p_start, nominal=Medium.p_default))); extends Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Slab; extends Buildings.Fluid.Interfaces.LumpedVolumeDeclarations; extends Buildings.Fluid.Interfaces.TwoPortFlowResistanceParameters( dp_nominal = Modelica.Fluid.Pipes.BaseClasses.WallFriction.Detailed.pressureLoss_m_flow( m_flow=m_flow_nominal/nCir, rho_a=rho_default, rho_b=rho_default, mu_a=mu_default, mu_b=mu_default, length=length, diameter=pipe.dIn, roughness=pipe.roughness, m_flow_small=m_flow_small/nCir)); parameter Integer nCir(min=1) = 1 "Number of parallel circuits"; parameter Integer nSeg(min=1) = if heatTransfer==Types.HeatTransfer.EpsilonNTU then 1 else 5 "Number of volume segments in each circuit (along flow path)"; parameter Modelica.SIunits.Area A "Surface area of radiant slab (all circuits combined)"; parameter Modelica.SIunits.Length length = A/disPip/nCir "Length of the pipe of a single circuit"; parameter Modelica.SIunits.MassFlowRate m_flow_nominal "Nominal mass flow rate of all circuits combined"; parameter Modelica.SIunits.MassFlowRate m_flow_small(min=0) = 1E-4*abs(m_flow_nominal) "Small mass flow rate of all circuits combined for regularization of zero flow"; final parameter Modelica.SIunits.Velocity v_nominal= 4*m_flow_nominal/pipe.dIn^2/Modelica.Constants.pi/rho_default/nCir "Velocity at m_flow_nominal"; // Parameters used for the fluid model implementation parameter Boolean homotopyInitialization = true "= true, use homotopy method"; parameter Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.HeatTransfer heatTransfer=Types.HeatTransfer.EpsilonNTU "Model for heat transfer between fluid and slab"; // Diagnostics parameter Boolean show_T = false "= true, if actual temperature at port is computed"; Modelica.SIunits.MassFlowRate m_flow(start=0) = port_a.m_flow "Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) for all circuits combined"; Modelica.SIunits.PressureDifference dp(start=0, displayUnit="Pa") = port_a.p - port_b.p "Pressure difference between port_a and port_b"; Medium.ThermodynamicState sta_a=if homotopyInitialization then Medium.setState_phX(port_a.p, homotopy(actual=noEvent(actualStream(port_a.h_outflow)), simplified=inStream(port_a.h_outflow)), homotopy(actual=noEvent(actualStream(port_a.Xi_outflow)), simplified=inStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) if show_T "Medium properties in port_a"; Medium.ThermodynamicState sta_b=if homotopyInitialization then Medium.setState_phX(port_b.p, homotopy(actual=noEvent(actualStream(port_b.h_outflow)), simplified=port_b.h_outflow), homotopy(actual=noEvent(actualStream(port_b.Xi_outflow)), simplified=port_b.Xi_outflow)) else Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) if show_T "Medium properties in port_b"; Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab sla( redeclare final package Medium = Medium, final heatTransfer=heatTransfer, final sysTyp=sysTyp, final A=A/nCir, final disPip=disPip, final pipe=pipe, final layers=layers, final steadyStateInitial=steadyStateInitial, final iLayPip=iLayPip, final T_a_start=T_a_start, final T_b_start=T_b_start, final energyDynamics=energyDynamics, final massDynamics=massDynamics, final p_start=p_start, final T_start=T_start, final X_start=X_start, final C_start=C_start, final C_nominal=C_nominal, final allowFlowReversal=allowFlowReversal, final m_flow_nominal=m_flow_nominal/nCir, final m_flow_small=m_flow_small/nCir, final homotopyInitialization=homotopyInitialization, final from_dp=from_dp, final dp_nominal=dp_nominal, final linearizeFlowResistance=linearizeFlowResistance, final deltaM=deltaM, final nSeg=nSeg, final length=length, final ReC=4000) "Single parallel circuit of the radiant slab"; protected parameter Medium.ThermodynamicState state_default = Medium.setState_pTX( T=Medium.T_default, p=Medium.p_default, X=Medium.X_default[1:Medium.nXi]) "Start state"; parameter Modelica.SIunits.Density rho_default = Medium.density(state_default); parameter Modelica.SIunits.DynamicViscosity mu_default = Medium.dynamicViscosity(state_default) "Dynamic viscosity at nominal condition"; Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.MassFlowRateMultiplier masFloMul_a( redeclare final package Medium = Medium, final k=nCir) "Mass flow multiplier, used to avoid having to instanciate multiple slab models"; Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.MassFlowRateMultiplier masFloMul_b( redeclare final package Medium = Medium, final k=nCir) "Mass flow multiplier, used to avoid having to instanciate multiple slab models"; Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.HeatFlowRateMultiplier heaFloMul_a( final k=nCir) "Heat flow rate multiplier, used to avoid having to instanciate multiple slab models"; Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.HeatFlowRateMultiplier heaFloMul_b( final k=nCir) "Heat flow rate multiplier, used to avoid having to instanciate multiple slab models"; equation connect(sla.port_b, masFloMul_b.port_a); connect(masFloMul_b.port_b, port_b); connect(port_a, masFloMul_a.port_b); connect(masFloMul_a.port_a, sla.port_a); connect(sla.surf_a,heaFloMul_a. port_a); connect(heaFloMul_a.port_b, surf_a); connect(sla.surf_b,heaFloMul_b. port_a); connect(heaFloMul_b.port_b, surf_b); end ParallelCircuitsSlab;

Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab

Model of a single circuit of a radiant slab

Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab

Information

This is a model of a single flow circuit of a radiant slab with pipes or a capillary heat exchanger embedded in the construction. For a model with multiple parallel flow circuits, see Buildings.Fluid.HeatExchangers.RadiantSlabs.ParallelCircuitsSlab.

See the user's guide for more information.

Extends from Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Slab (Base class for radiant slab), Buildings.Fluid.FixedResistances.BaseClasses.Pipe (Model of a pipe with finite volume discretization along the flow path).

Parameters

TypeNameDefaultDescription
SystemTypesysTyp Radiant system type
DistancedisPip Pipe distance [m]
Genericpipe Record for pipe geometry and material
replaceable package MediumPartialMediumMedium in the component
IntegernSegif heatTransfer == Types.Hea...Number of volume segments
LengththicknessIns0Thickness of insulation [m]
ThermalConductivitylambdaIns0.04Heat conductivity of insulation [W/(m.K)]
Lengthdiameterpipe.dInPipe diameter (without insulation) [m]
LengthlengthA/disPipLength of the pipe [m]
HeatTransferheatTransferTypes.HeatTransfer.EpsilonNTUModel for heat transfer between fluid and slab
Construction
Genericlayers Definition of the construction, which must have at least two material layers
IntegeriLayPip Number of the interface layer in which the pipes are located
AreaA Surface area of radiant slab [m2]
Nominal condition
MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]
PressureDifferencedp_nominalModelica.Fluid.Pipes.BaseCla...Pressure difference [Pa]
Initialization
MassFlowRatem_flow.start0Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
PressureDifferencedp.start0Pressure difference between port_a and port_b [Pa]
Initialization
Construction
BooleansteadyStateInitialfalse=true initializes dT(0)/dt=0, false initializes T(0) at fixed temperature using T_a_start, T_c_start and T_b_start
TemperatureT_a_start293.15Initial temperature at surf_a, used if steadyStateInitial = false [K]
TemperatureT_b_start293.15Initial temperature at surf_b, used if steadyStateInitial = false [K]
TemperatureT_c_start(T_a_start*con_b[1].layers.R...Initial construction temperature in the layer that contains the pipes, used if steadyStateInitial = false [K]
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
TemperatureT_startMedium.T_defaultStart value of temperature [K]
MassFractionX_start[Medium.nX]Medium.X_defaultStart value of mass fractions m_i/m [kg/kg]
ExtraPropertyC_start[Medium.nC]fill(0, Medium.nC)Start value of trace substances
ExtraPropertyC_nominal[Medium.nC]fill(1E-2, Medium.nC)Nominal value of trace substances. (Set to typical order of magnitude.)
Dynamics
Equations
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Type of energy balance: dynamic (3 initialization options) or steady state
DynamicsmassDynamicsenergyDynamicsType of mass balance: dynamic (3 initialization options) or steady state
RealmSenFac1Factor for scaling the sensible thermal mass of the volume
Assumptions
BooleanallowFlowReversaltrue= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRatem_flow_small1E-4*abs(m_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Flow resistance
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistancefalse= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM0.1Fraction of nominal flow rate where flow transitions to laminar
RealReC4000Reynolds number where transition to turbulent starts

Connectors

TypeNameDescription
HeatPort_asurf_aHeat port at construction surface
HeatPort_asurf_bHeat port at construction surface
FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)

Modelica definition

model SingleCircuitSlab "Model of a single circuit of a radiant slab" extends Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Slab; extends Buildings.Fluid.FixedResistances.BaseClasses.Pipe( nSeg=if heatTransfer==Types.HeatTransfer.EpsilonNTU then 1 else 5, final diameter=pipe.dIn, length=A/disPip, final thicknessIns=0, final lambdaIns = 0.04, dp_nominal = Modelica.Fluid.Pipes.BaseClasses.WallFriction.Detailed.pressureLoss_m_flow( m_flow=m_flow_nominal, rho_a=rho_default, rho_b=rho_default, mu_a=mu_default, mu_b=mu_default, length=length, diameter=pipe.dIn, roughness=pipe.roughness, m_flow_small=m_flow_small), preDro(dp(nominal=200*length))); parameter Modelica.SIunits.Area A "Surface area of radiant slab"; parameter Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.HeatTransfer heatTransfer=Types.HeatTransfer.EpsilonNTU "Model for heat transfer between fluid and slab"; parameter Modelica.SIunits.Temperature T_c_start= (T_a_start*con_b[1].layers.R+T_b_start*con_a[1].layers.R)/layers.R "Initial construction temperature in the layer that contains the pipes, used if steadyStateInitial = false"; final parameter Modelica.SIunits.Velocity v_nominal= 4*m_flow_nominal/pipe.dIn^2/Modelica.Constants.pi/rho_default "Velocity at m_flow_nominal"; Buildings.HeatTransfer.Conduction.MultiLayer con_a[nSeg]( each final A=A/nSeg, each steadyStateInitial=steadyStateInitial, each layers( final nLay = iLayPip, final material={layers.material[i] for i in 1:iLayPip}, absIR_a=layers.absIR_a, absIR_b=layers.absIR_b, absSol_a=layers.absSol_a, absSol_b=layers.absSol_b, roughness_a=layers.roughness_a), each T_a_start=T_a_start, each T_b_start=T_c_start) "Construction near the surface port surf_a"; Buildings.HeatTransfer.Conduction.MultiLayer con_b[nSeg]( each final A=A/nSeg, each steadyStateInitial=steadyStateInitial, each layers( final nLay = layers.nLay-iLayPip, final material={layers.material[i] for i in iLayPip + 1:layers.nLay}, absIR_a=layers.absIR_a, absIR_b=layers.absIR_b, absSol_a=layers.absSol_a, absSol_b=layers.absSol_b, roughness_a=layers.roughness_a), each T_a_start=T_c_start, each T_b_start=T_b_start) "Construction near the surface port surf_b"; protected Modelica.Thermal.HeatTransfer.Components.ThermalCollector colAllToOne( final m=nSeg) "Connector to assign multiple heat ports to one heat port"; Modelica.Thermal.HeatTransfer.Components.ThermalCollector colAllToOne1( final m=nSeg) "Connector to assign multiple heat ports to one heat port"; final parameter Modelica.SIunits.ThermalInsulance Rx= Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Functions.AverageResistance( disPip=disPip, dPipOut=pipe.dOut, k=layers.material[iLayPip].k, sysTyp=sysTyp, kIns=layers.material[iLayPip+1].k, dIns=layers.material[iLayPip+1].x) "Thermal insulance for average temperature in plane with pipes"; BaseClasses.PipeToSlabConductance fluSlaCon[nSeg]( redeclare each final package Medium = Medium, each final APip=Modelica.Constants.pi*pipe.dIn*length/nSeg, each final RWal=Modelica.Math.log(pipe.dOut/pipe.dIn)/(2*Modelica.Constants.pi*pipe.k*( length/nSeg)), each final RFic=nSeg*Rx/A, each final m_flow_nominal=m_flow_nominal, each kc_IN_con= Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_overall_IN_con( d_hyd=pipe.dIn, L=length/nSeg, K=pipe.roughness), each heatTransfer=heatTransfer) "Conductance between fluid and the slab"; Modelica.SIunits.MassFraction Xi_in_a[Medium.nXi] = inStream(port_a.Xi_outflow) "Inflowing mass fraction at port_a"; Modelica.SIunits.MassFraction Xi_in_b[Medium.nXi] = inStream(port_b.Xi_outflow) "Inflowing mass fraction at port_a"; Modelica.Blocks.Sources.RealExpression T_a( final y=Medium.temperature_phX(p=port_a.p, h=inStream(port_a.h_outflow), X=cat(1,Xi_in_a,{1-sum(Xi_in_a)}))) "Fluid temperature at port a"; Modelica.Blocks.Sources.RealExpression T_b( final y=Medium.temperature_phX(p=port_b.p, h=inStream(port_b.h_outflow), X=cat(1,Xi_in_b,{1-sum(Xi_in_b)}))) "Fluid temperature at port b"; Modelica.Blocks.Sources.RealExpression mFlu_flow[nSeg](each y=m_flow) "Input signal for mass flow rate"; Modelica.Blocks.Routing.Replicator T_a_rep(final nout=nSeg) "Signal replicator for T_a"; Modelica.Blocks.Routing.Replicator T_b_rep(final nout=nSeg) "Signal replicator for T_b"; equation connect(colAllToOne1.port_b,surf_a); connect(colAllToOne.port_b,surf_b); connect(colAllToOne1.port_a, con_a.port_a); connect(colAllToOne.port_a, con_b.port_b); connect(fluSlaCon.fluid, vol.heatPort); connect(mFlu_flow.y, fluSlaCon.m_flow); connect(T_a.y, T_a_rep.u); connect(T_b.y, T_b_rep.u); connect(fluSlaCon.T_a, T_a_rep.y); connect(T_b_rep.y, fluSlaCon.T_b); connect(con_b.port_a, fluSlaCon.solid); connect(fluSlaCon.solid, con_a.port_b); end SingleCircuitSlab;
http://simulationresearch.lbl.gov/modelica