Buildings.Fluid.HeatExchangers.ActiveBeams.BaseClasses
Base classes for active beam models
Information
This package contains base classes that are used to construct the models in Buildings.Fluid.HeatExchangers.ActiveBeams.
Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).
Package Content
| Name | Description |
|---|---|
 Convector
|
Heat exchanger for the water stream |
 DerivativesCubicSpline
|
Cubic spline for interpolation |
 ModificationFactor
|
Factor to modify nominal capacity |
 Examples
|
Buildings.Fluid.HeatExchangers.ActiveBeams.BaseClasses.Convector
Heat exchanger for the water stream
Information
In cooling mode, this model adds heat to the water stream. The heat added is equal to:
QBeam = Qrated fΔT fSA fW
In heating mode, the heat is removed from the water stream.
Extends from Buildings.Fluid.Interfaces.PartialTwoPortInterface (Partial model transporting fluid between two ports without storing mass or energy), Buildings.Fluid.Interfaces.TwoPortFlowResistanceParameters (Parameters for flow resistance for models with two ports).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Generic | per | Performance data | |
| Integer | nBeams | nBeams(min=1) | Number of beams in parallel |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | per.mWat_flow_nominal*nBeams | Nominal mass flow rate [kg/s] |
| PressureDifference | dp_nominal | per.dpWat_nominal | Pressure difference [Pa] |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Flow resistance | |||
| Boolean | computeFlowResistance | true | =true, compute flow resistance. Set to false to assume no friction |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | linearizeFlowResistance | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | deltaM | 0.1 | Fraction of nominal flow rate where flow transitions to laminar |
| Dynamics | |||
| Nominal condition | |||
| Time | tau | 30 | Time constant at nominal flow (if energyDynamics <> SteadyState) [s] |
| Equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state |
| Initialization | |||
| AbsolutePressure | p_start | Medium.p_default | Start value of pressure [Pa] |
| Temperature | T_start | Medium.T_default | Start value of temperature [K] |
| MassFraction | X_start[Medium.nX] | Medium.X_default | Start value of mass fractions m_i/m [kg/kg] |
| ExtraProperty | C_start[Medium.nC] | fill(0, Medium.nC) | Start value of trace substances |
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) |
| input RealInput | mAir_flow | Air mass flow rate of a single beam [kg/s] |
| input RealInput | TRoo | Room air temperature [K] |
| output RealOutput | Q_flow | Actual capacity of a single beam [W] |
Modelica definition
model Convector "Heat exchanger for the water stream"
extends Buildings.Fluid.Interfaces.PartialTwoPortInterface(
final m_flow_nominal = per.mWat_flow_nominal*nBeams);
extends Buildings.Fluid.Interfaces.TwoPortFlowResistanceParameters(
final computeFlowResistance=true,
final dp_nominal = per.dpWat_nominal "Don't multiply with nBeams, as the beams are in parallel");
constant Boolean homotopyInitialization = true "= true, use homotopy method";
parameter Data.Generic per "Performance data";
parameter Integer nBeams(min=1) "Number of beams in parallel";
parameter Modelica.SIunits.Time tau = 30
"Time constant at nominal flow (if energyDynamics <> SteadyState)";
// Dynamics
parameter Modelica.Fluid.Types.Dynamics energyDynamics=Modelica.Fluid.Types.Dynamics.DynamicFreeInitial
"Type of energy balance: dynamic (3 initialization options) or steady state";
parameter Modelica.Fluid.Types.Dynamics massDynamics=energyDynamics
"Type of mass balance: dynamic (3 initialization options) or steady state";
// Initialization
parameter Medium.AbsolutePressure p_start = Medium.p_default
"Start value of pressure";
parameter Medium.Temperature T_start = Medium.T_default
"Start value of temperature";
parameter Medium.MassFraction X_start[Medium.nX](
final quantity=Medium.substanceNames) = Medium.X_default
"Start value of mass fractions m_i/m";
parameter Medium.ExtraProperty C_start[Medium.nC](
final quantity=Medium.extraPropertiesNames)=fill(0, Medium.nC)
"Start value of trace substances";
Modelica.Blocks.Interfaces.RealInput mAir_flow(
final unit="kg/s") "Air mass flow rate of a single beam";
Modelica.Blocks.Interfaces.RealInput TRoo(
final unit="K",
displayUnit="degC") "Room air temperature";
Modelica.Blocks.Interfaces.RealOutput Q_flow(final unit="W")
"Actual capacity of a single beam";
protected
HeaterCooler_u hex(
redeclare final package Medium = Medium,
final allowFlowReversal=allowFlowReversal,
final m_flow_nominal=m_flow_nominal,
final m_flow_small=m_flow_small,
final show_T=false,
final from_dp=from_dp,
final dp_nominal=dp_nominal,
final linearizeFlowResistance=linearizeFlowResistance,
final deltaM=deltaM,
final tau=tau,
final homotopyInitialization=homotopyInitialization,
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 Q_flow_nominal=-nBeams * per.Q_flow_nominal)
"Heat exchanger for the water stream";
ModificationFactor mod(
final nBeams=nBeams,
final per=per) "Performance modification for part load";
Modelica.Blocks.Sources.RealExpression senTem(final y=Medium.temperature(port_a_inflow))
"Actual water temperature entering the beam";
Medium.ThermodynamicState port_a_inflow=
Medium.setState_phX(port_a.p, inStream(port_a.h_outflow), inStream(port_a.Xi_outflow))
"state for medium inflowing through port_a";
Sensors.MassFlowRate senFloWatCoo(
redeclare final package Medium = Medium) "Mass flow rate sensor";
initial equation
assert(homotopyInitialization, "In " + getInstanceName() +
": The constant homotopyInitialization has been modified from its default value. This constant will be removed in future releases.",
level = AssertionLevel.warning);
equation
connect(hex.Q_flow, Q_flow);
connect(hex.port_b, port_b);
connect(mod.y, hex.u);
connect(senTem.y, mod.TWat);
connect(TRoo, mod.TRoo);
connect(mAir_flow, mod.mAir_flow);
connect(senFloWatCoo.port_a, port_a);
connect(senFloWatCoo.port_b, hex.port_a);
connect(senFloWatCoo.m_flow, mod.mWat_flow);
end Convector;
Buildings.Fluid.HeatExchangers.ActiveBeams.BaseClasses.DerivativesCubicSpline
Cubic spline for interpolation
Information
This model calculates the output based on the cubic hermite interpolation and linear extrapolation of predefined values. The predefined values must create a monotone curve.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | xd[:] | {0,0.5,1} | |
| Real | yd[size(xd, 1)] | {0,0.75,1} |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Independent variable for interpolation |
| output RealOutput | y | Interpolated value |
Modelica definition
model DerivativesCubicSpline "Cubic spline for interpolation"
extends Modelica.Blocks.Icons.Block;
parameter Real[:] xd={0,0.5,1};
parameter Real[size(xd, 1)] yd={0,0.75,1};
Modelica.Blocks.Interfaces.RealInput u
"Independent variable for interpolation";
Modelica.Blocks.Interfaces.RealOutput y "Interpolated value";
protected
parameter Real[size(xd, 1)] dMonotone(each fixed=false) "Derivatives";
Integer i "Counter to pick the interpolation interval";
initial algorithm
// Get the derivative values at the support points
dMonotone := Buildings.Utilities.Math.Functions.splineDerivatives(
x=xd,
y=yd,
ensureMonotonicity=true);
algorithm
i := 1;
for j in 1:size(xd, 1) - 1 loop
if u > xd[j] then
i := j;
end if;
end for;
// Extrapolate or interpolate the data
y :=
Buildings.Utilities.Math.Functions.cubicHermiteLinearExtrapolation(
x=u,
x1=xd[i],
x2=xd[i + 1],
y1=yd[i],
y2=yd[i + 1],
y1d=dMonotone[i],
y2d=dMonotone[i + 1]);
end DerivativesCubicSpline;
Buildings.Fluid.HeatExchangers.ActiveBeams.BaseClasses.ModificationFactor
Factor to modify nominal capacity
Information
This model determines the three modification factors described in Buildings.Fluid.HeatExchangers.ActiveBeams.UsersGuide by comparing the actual values of air mass flow rate, water mass flow rate and room-water temperature difference with the nominal values. The three modification factors are then multiplied. Input to this model are the total mass flow rates of all parallel beams combined.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nBeams | nBeams(min=1) | Number of beams in parallel |
| Generic | per | Performance data |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | TWat | Temperature of the water entering the beams [K] |
| input RealInput | mWat_flow | Mass flow rate of the water entering the beams [kg/s] |
| input RealInput | mAir_flow | Mass flow rate of the primary air entering the beams [kg/s] |
| input RealInput | TRoo | Room air temperature [K] |
| output RealOutput | y | Total modification factor [1] |
Modelica definition
model ModificationFactor "Factor to modify nominal capacity"
extends Modelica.Blocks.Icons.Block;
parameter Integer nBeams(min=1) "Number of beams in parallel";
parameter Data.Generic per "Performance data";
Modelica.Blocks.Interfaces.RealInput TWat(
final unit="K",
displayUnit="degC") "Temperature of the water entering the beams";
Modelica.Blocks.Interfaces.RealInput mWat_flow(
final unit="kg/s") "Mass flow rate of the water entering the beams";
Modelica.Blocks.Interfaces.RealInput mAir_flow(
final unit="kg/s") "Mass flow rate of the primary air entering the beams";
Modelica.Blocks.Interfaces.RealInput TRoo(
final unit="K",
displayUnit="degC") "Room air temperature";
Modelica.Blocks.Interfaces.RealOutput y(final unit="1")
"Total modification factor";
protected
Modelica.Blocks.Sources.Constant temDif_nom(
final k=1/per.dT_nominal)
"Nominal temperature difference between water and room air";
Modelica.Blocks.Sources.Constant watFlo_nom(final k=1/(nBeams*per.mWat_flow_nominal))
"Nominal water mass flow rate";
Modelica.Blocks.Sources.Constant airFlo_nom(final k=1/(nBeams*per.mAir_flow_nominal))
"Nominal water mass flow rate";
DerivativesCubicSpline temDif_mod(
final xd=per.dT.r_dT,
final yd=per.dT.f)
"Derivatives of the cubic spline for the temperature difference between room and water";
DerivativesCubicSpline watFlo_mod(
final xd=per.water.r_V,
final yd=per.water.f) "Derivatives of the cubic spline for the water flow";
DerivativesCubicSpline airFlo_mod(
final xd=per.primaryAir.r_V,
final yd=per.primaryAir.f)
"Derivatives of the cubic spline for the air flow";
Modelica.Blocks.Math.Product pro_3
"Ratio of actual/nominal temperature difference";
Modelica.Blocks.Math.Product pro_2 "Ratio of actual/nominal water flow rate";
Modelica.Blocks.Math.Product pro_1 "Ratio of actual/nominal air flow rate";
Modelica.Blocks.Math.MultiProduct mulPro(final nu=3)
"Product of the three modification factors";
Modelica.Blocks.Math.Add add(final k1=+1, final k2=-1)
"Temperature difference between water and room air";
equation
connect(mAir_flow, pro_1.u1);
connect(airFlo_nom.y, pro_1.u2);
connect(pro_1.y, airFlo_mod.u);
connect(mulPro.y, y);
connect(mWat_flow, pro_2.u1);
connect(pro_2.y, watFlo_mod.u);
connect(watFlo_nom.y, pro_2.u2);
connect(TWat, add.u1);
connect(add.u2, TRoo);
connect(temDif_nom.y, pro_3.u2);
connect(add.y, pro_3.u1);
connect(pro_3.y, temDif_mod.u);
connect(watFlo_mod.y, mulPro.u[1]);
connect(airFlo_mod.y, mulPro.u[2]);
connect(temDif_mod.y, mulPro.u[3]);
end ModificationFactor;