Buildings.DHC.Loads.HotWater.BaseClasses
Package with base classes that are used by multiple models
Information
This package contains base classes that are used to construct the classes in Buildings.DHC.Loads.Heating.DHW.
Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).
Package Content
| Name | Description |
|---|---|
 HeatExchangerPumpController
|
Controller for pump of storage tank with external heat exchanger |
 PartialFourPortDHW
|
A partial model for domestic water heating |
 TankChargingController
|
Controller to enable or disable storage tank charging |
 TankValveController
|
Controller to divert the water to the middle or bottom of the tank |
Buildings.DHC.Loads.HotWater.BaseClasses.HeatExchangerPumpController
Controller for pump of storage tank with external heat exchanger
Information
Controller for heat exchanger mass flow rate.
This controller outputs the set point for the head of the heat exchanger pump
on the heating side. The set point is calculated using a PI controller that tracks
the set point for the leaving domestic hot water temperature,
with a minimum controller output equal to yMin.
By default, yMin=0.3, which corresponds to a mass flow rate
of 10% of the design flow rate.
If the measured domestic hot water flow rate is close to zero, then the set point for the pump is also set to zero in order to stop the pump if there is no domestic hot water flow rate.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| MassFlowRate | mDom_flow_nominal | Domestic hot water design flow rate (used for scaling) [kg/s] | |
| PressureDifference | dpPum_nominal | Heating water pump head at full speed through heat exchanger [Pa] | |
| Real | k | 0.1 | Proportioanl gain of circulation pump controller |
| Real | Ti | 60 | Integrator time constant of circulation pump controller |
| Real | yMin | 0.3 | Minimum controller output when pump is on |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | mDom_flow | Domestic hot water mass flow rate [kg/s] |
| input RealInput | TDomSet | Temperature setpoint for domestic hot water source from heater [K] |
| input RealInput | TDom | Measured hot water temperature [K] |
| output RealOutput | dpPumHex | Set point for pump head on heating water side [Pa] |
Modelica definition
block HeatExchangerPumpController
"Controller for pump of storage tank with external heat exchanger"
parameter Modelica.Units.SI.MassFlowRate mDom_flow_nominal
"Domestic hot water design flow rate (used for scaling)";
parameter Modelica.Units.SI.PressureDifference dpPum_nominal(
displayUnit="Pa",
min=0)
"Heating water pump head at full speed through heat exchanger";
parameter Real k=0.1 "Proportioanl gain of circulation pump controller";
parameter Real Ti=60 "Integrator time constant of circulation pump controller";
parameter Real yMin(min=0) = 0.3 "Minimum controller output when pump is on";
Buildings.Controls.OBC.CDL.Interfaces.RealInput mDom_flow(
final unit="kg/s")
"Domestic hot water mass flow rate";
Modelica.Blocks.Interfaces.RealInput TDomSet(
final unit="K",
displayUnit="degC")
"Temperature setpoint for domestic hot water source from heater";
Modelica.Blocks.Interfaces.RealInput TDom(
final unit="K",
displayUnit="degC")
"Measured hot water temperature";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput dpPumHex(
final unit="Pa",
displayUnit="Pa")
"Set point for pump head on heating water side";
Buildings.Controls.OBC.CDL.Reals.Hysteresis hysMasFlo(
uLow=mDom_flow_nominal/1E4,
uHigh=2*mDom_flow_nominal/1E4,
y(start=false))
"Hysteresis used to switch secondary pump on and off";
Buildings.Controls.OBC.CDL.Reals.PIDWithReset conPI(
controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI,
k=k,
Ti=Ti,
yMin=0.03,
y_reset=0)
"PI controller for pump";
Buildings.Controls.OBC.CDL.Reals.Switch swi "Switch for pump control";
protected
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter pumHea(final k=dpPum_nominal)
"Gain for hex pump head";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant con(final k=0) "Outputs zero";
equation
connect(conPI.y, pumHea.u);
connect(hysMasFlo.y,conPI. trigger);
connect(hysMasFlo.u, mDom_flow);
connect(pumHea.y, swi.u1);
connect(con.y, swi.u3);
connect(hysMasFlo.y, swi.u2);
connect(swi.y, dpPumHex);
connect(TDomSet, conPI.u_s);
connect(TDom, conPI.u_m);
end HeatExchangerPumpController;
Buildings.DHC.Loads.HotWater.BaseClasses.PartialFourPortDHW
A partial model for domestic water heating
Information
This partial model can be used for different domestic hot water generation methods.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package MediumDom | Modelica.Media.Interfaces.Pa... | Medium for domestic water in the component | |
| replaceable package MediumHea | Modelica.Media.Interfaces.Pa... | Medium for heating source in the component | |
| Assumptions | |||
| Boolean | allowFlowReversalDom | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for domestic water |
| Boolean | allowFlowReversalHea | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for heating water |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable package MediumDom | Medium for domestic water in the component | |
| replaceable package MediumHea | Medium for heating source in the component | |
| FluidPort_a | port_aDom | Fluid connector for cold water (or recirculation water) |
| FluidPort_b | port_bDom | Fluid connector for heated domestic hot water |
| FluidPort_a | port_aHea | Fluid connector for heating water (positive design flow direction is from port_a to port_b) |
| FluidPort_b | port_bHea | Fluid connector b for heating water (positive design flow direction is from port_a to port_b) |
| input RealInput | TDomSet | Temperature setpoint for heated domestic water [K] |
Modelica definition
partial model PartialFourPortDHW
"A partial model for domestic water heating"
extends Modelica.Blocks.Icons.Block;
replaceable package MediumDom =
Modelica.Media.Interfaces.PartialMedium "Medium for domestic water in the component";
replaceable package MediumHea =
Modelica.Media.Interfaces.PartialMedium "Medium for heating source in the component";
parameter Boolean allowFlowReversalDom=true
"= false to simplify equations, assuming, but not enforcing, no flow reversal for domestic water";
parameter Boolean allowFlowReversalHea=true
"= false to simplify equations, assuming, but not enforcing, no flow reversal for heating water";
Modelica.Fluid.Interfaces.FluidPort_a port_aDom(
redeclare final package Medium = MediumDom,
m_flow(min=if allowFlowReversalDom then -Modelica.Constants.inf else 0),
h_outflow(start=MediumDom.h_default, nominal=MediumDom.h_default))
"Fluid connector for cold water (or recirculation water)";
Modelica.Fluid.Interfaces.FluidPort_b port_bDom(
redeclare final package Medium = MediumDom,
m_flow(max=if allowFlowReversalDom then +Modelica.Constants.inf else 0),
h_outflow(start=MediumDom.h_default, nominal=MediumDom.h_default))
"Fluid connector for heated domestic hot water";
Modelica.Fluid.Interfaces.FluidPort_a port_aHea(
redeclare final package Medium = MediumHea,
m_flow(min=if allowFlowReversalHea then -Modelica.Constants.inf else 0),
h_outflow(start=MediumHea.h_default, nominal=MediumHea.h_default))
"Fluid connector for heating water (positive design flow direction is from port_a to port_b)";
Modelica.Fluid.Interfaces.FluidPort_b port_bHea(
redeclare final package Medium = MediumHea,
m_flow(max=if allowFlowReversalHea then +Modelica.Constants.inf else 0),
h_outflow(start=MediumHea.h_default, nominal=MediumHea.h_default))
"Fluid connector b for heating water (positive design flow direction is from port_a to port_b)";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TDomSet(
final unit="K",
displayUnit="degC")
"Temperature setpoint for heated domestic water";
end PartialFourPortDHW;
Buildings.DHC.Loads.HotWater.BaseClasses.TankChargingController
Controller to enable or disable storage tank charging
Information
Controller that outputs charge=true if the domestic hot
water tank needs to be charged, and false otherwise.
Whether the tank needs to be charged depends on the difference between the measured top and bottom tank temperatures and the tank's set point. If the top temperature is below the set point with hysteresis, charging is enabled until the bottom temperature reaches the set point with hysteresis, at which point charging is disabled. The hysteresis is 5 Kelvin.
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | TTanTop | Measured temperature at top of tank [K] |
| input RealInput | TTanTopSet | Temperature setpoint for top section of hot water tank [K] |
| output BooleanOutput | charge | Outputs true if tank should be charged |
| input RealInput | TTanBot | Measured temperature at bottom of tank [K] |
Modelica definition
block TankChargingController
"Controller to enable or disable storage tank charging"
Buildings.Controls.OBC.CDL.Interfaces.RealInput TTanTop(
final unit="K",
displayUnit="degC") "Measured temperature at top of tank";
Modelica.Blocks.Interfaces.RealInput TTanTopSet(
final unit="K",
displayUnit="degC")
"Temperature setpoint for top section of hot water tank";
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput charge
"Outputs true if tank should be charged";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TTanBot(final unit="K", displayUnit=
"degC") "Measured temperature at bottom of tank";
Buildings.Controls.OBC.CDL.Logical.Latch lat;
Buildings.Controls.OBC.CDL.Logical.Not not1;
protected
Buildings.Controls.OBC.CDL.Reals.Hysteresis cha(uLow=-5, uHigh=0)
"Outputs true if tank should be charged";
Buildings.Controls.OBC.CDL.Reals.Subtract sub;
protected
Buildings.Controls.OBC.CDL.Reals.Hysteresis cha1(uLow=-5, uHigh=0)
"Outputs true if tank should be charged";
Buildings.Controls.OBC.CDL.Reals.Subtract sub1;
equation
connect(sub.u2, TTanTop);
connect(sub.u1, TTanTopSet);
connect(sub.y, cha.u);
connect(sub1.y, cha1.u);
connect(TTanTopSet, sub1.u1);
connect(TTanBot, sub1.u2);
connect(cha.y, lat.u);
connect(lat.y, charge);
connect(cha1.y, not1.u);
connect(not1.y, lat.clr);
end TankChargingController;
Buildings.DHC.Loads.HotWater.BaseClasses.TankValveController
Controller to divert the water to the middle or bottom of the tank
Information
Controller that outputs the commanded position for the valve that diverts the return water to the middle or bottom of the tank.
The controller changes its commanded valve position continuously between 0 and 1.
If the measured temperature TRet is below TSwi, the output is
0, otherwise it is 1. The controller has a hysteresis of 2 Kelvin.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Temperature | TSwi | 318.15 | Switching temperature for return water [K] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | TRet | Return water temperature [K] |
| output RealOutput | y | Valve position |
Modelica definition
block TankValveController
"Controller to divert the water to the middle or bottom of the tank"
parameter Modelica.Units.SI.Temperature TSwi = 318.15 "Switching temperature for return water";
Modelica.Blocks.Interfaces.RealInput TRet(final unit="K", displayUnit="degC")
"Return water temperature";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput y "Valve position";
Modelica.Blocks.Continuous.LimIntegrator ram(
k=1/120,
outMax=1,
outMin=0,
strict=false)
"Ramp signal for valve position";
Buildings.Controls.OBC.CDL.Conversions.BooleanToReal booToRea;
protected
Buildings.Controls.OBC.CDL.Reals.Hysteresis cha(uLow=TSwi - 1, uHigh=TSwi + 1)
"Outputs true if tank should be charged";
equation
connect(cha.y, booToRea.u);
connect(booToRea.y, ram.u);
connect(ram.y, y);
connect(cha.u, TRet);
end TankValveController;