Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses

Information

This package contains base classes that are used to construct the models in Buildings.Fluid.HeatExchangers.RadiantSlabs.

Package Content

Name	Description
InternalFlowConvection	Convective heat transfer in pipes
HeatFlowRateMultiplier	Multiplies the heat flow rate
MassFlowRateMultiplier	Model that multiplies the mass flow rate
Slab	Base class for radiant slab
Functions	Functions for convective heat transfer
Types	Types for radiant slab model

Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.InternalFlowConvection

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
Area	A		Pipe inside surface area [m2]
kc_overall_IN_con	kc_IN_con		Parameters for convective heat transfer calculation

Connectors

Type	Name	Description
replaceable package Medium		Medium in the component
HeatPort_a	solid	Heat port at solid interface
HeatPort_b	fluid	Heat port at fluid interface
input RealInput	m_flow	Fluid mass flow rate [kg/s]

Modelica definition

model InternalFlowConvection "Convective heat transfer in pipes"
  replaceable package Medium =
    Modelica.Media.Interfaces.PartialMedium "Medium in the component";
  Modelica.SIunits.HeatFlowRate Q_flow "Heat flow rate from solid -> fluid";
  Modelica.SIunits.TemperatureDifference dT "= solid.T - fluid.T";
  Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a solid 
    "Heat port at solid interface";
  Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_b fluid 
    "Heat port at fluid interface";
  parameter Modelica.SIunits.Area A "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";
  Modelica.Blocks.Interfaces.RealInput m_flow(unit="kg/s") 
    "Fluid mass flow rate";
  Modelica.SIunits.CoefficientOfHeatTransfer hCon 
    "Convective heat transfer coefficient";
protected 
  Medium.ThermodynamicState fluSta = Medium.setState_pTX(p=Medium.p_default, T=fluid.T, X=Medium.X_default) 
    "State of the medium";
equation 
  hCon = Modelica.Fluid.Dissipation.HeatTransfer.StraightPipe.kc_overall_KC(
     IN_con=kc_IN_con, IN_var=kc_IN_var);

  dT = solid.T - fluid.T;
  solid.Q_flow = Q_flow;
  fluid.Q_flow = -Q_flow;
  Q_flow = hCon*A*dT;
end InternalFlowConvection;

Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.HeatFlowRateMultiplier

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.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

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

Connectors

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)

Modelica definition

model MassFlowRateMultiplier 
  "Model that multiplies the mass flow rate"
  extends Modelica.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.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		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]

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.BaseClasses.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;