Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses

Name	Description
HeatFlowRateMultiplier	Multiplies the heat flow rate
MassFlowRateMultiplier	Model that multiplies the mass 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

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

Connectors

Modelica definition

Type	Name	Default	Description
Real	k		Gain for mass flow rate

Type	Name	Description
HeatPort_a	port_a
HeatPort_b	port_b

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.MassFlowRateMultiplier

Information

This model multiplies the mass flow rate so that 0 = port_b.m_flow + k * port_a.m_flow.

The specific enthalpy, the species concentration and the trace substance concentration remains unchanged. Therefore, this model does not conserve mass or 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

Connectors

Modelica definition

Type	Name	Default	Description
replaceable package Medium	PartialMedium	Medium in the component
Real	k		Gain for mass flow rate
Assumptions
Boolean	allowFlowReversal	true	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)

model MassFlowRateMultiplier "Model that multiplies the mass flow rate" extends Buildings.Fluid.Interfaces.PartialTwoPort; 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 // Pressure drop in design flow direction port_a.p = port_b.p; // Mass balance (mass is not conserved by this model!) port_b.m_flow = -k*port_a.m_flow; // Specific enthalpy flow rate port_a.h_outflow = inStream(port_b.h_outflow); port_b.h_outflow = inStream(port_a.h_outflow); // Transport of substances port_a.Xi_outflow = inStream(port_b.Xi_outflow); port_b.Xi_outflow = inStream(port_a.Xi_outflow); port_a.C_outflow = inStream(port_b.C_outflow); port_b.C_outflow = inStream(port_a.C_outflow); end MassFlowRateMultiplier;

Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.PipeToSlabConductance

Convective heat transfer in pipes and fictitious resistance to average slab temperature

Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.PipeToSlabConductance

Information

Parameters

Connectors

Modelica definition

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]

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

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 Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.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"; protected 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

Information

This partial model is used to construct radiant slab models with one circuit or with multiple parallel circuits.

Parameters

Connectors

Modelica definition

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		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]

Type	Name	Description
HeatPort_a	surf_a	Heat port at construction surface
HeatPort_a	surf_b	Heat port at construction surface

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"; 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;