modelPartialCoolingCoilHumidifyingHeating

Partial AHU model

Diagram of PartialCoolingCoilHumidifyingHeating

Extends from Buildings.Fluid.Interfaces.PartialFourPortInterface (Partial model with four ports and declaration of quantities that are used by many models), Buildings.Applications.DataCenters.ChillerCooled.Equipment.BaseClasses.AHUParameters (Essential parameters for air handling unit), Buildings.Fluid.Actuators.BaseClasses.ValveParameters (Model with parameters for valves), Buildings.Fluid.Interfaces.FourPortFlowResistanceParameters (Parameters for flow resistance for models with four ports).

Information

This model describes a partial air handling unit model, which contains a water-side valve, a cooling coil and a fan model.

The valve and fan are partial models, and should be redeclared when used in the air handling unit model.

Parameters

Type	Name	Default	Description
Boolean	homotopyInitialization	true	= true, use homotopy method
Buildings.Fluid.Movers.Data.Generic	perFan		Performance data for the fan
Assumptions
Boolean	allowFlowReversal1 (from PartialFourPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1
Boolean	allowFlowReversal2 (from PartialFourPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for medium 2
Nominal condition
Modelica.Units.SI.MassFlowRate	m1_flow_nominal (from PartialFourPortInterface)		Nominal mass flow rate
Modelica.Units.SI.MassFlowRate	m2_flow_nominal (from PartialFourPortInterface)		Nominal mass flow rate
Modelica.Units.SI.MassFlowRate	m_flow_nominal (from ValveParameters)		Nominal mass flow rate
Modelica.Units.SI.PressureDifference	dpValve_nominal (from ValveParameters)		Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint
Modelica.Units.SI.PressureDifference	dp1_nominal (from FourPortFlowResistanceParameters)		Pressure difference
Modelica.Units.SI.PressureDifference	dp2_nominal (from FourPortFlowResistanceParameters)		Pressure difference
Advanced
Medium1.MassFlowRate	m1_flow_small (from PartialFourPortInterface)	1E-4*abs(m1_flow_nominal)	Small mass flow rate for regularization of zero flow
Medium2.MassFlowRate	m2_flow_small (from PartialFourPortInterface)	1E-4*abs(m2_flow_nominal)	Small mass flow rate for regularization of zero flow
Advanced › Diagnostics
Boolean	show_T (from PartialFourPortInterface)	false	= true, if actual temperature at port is computed
Cooling coil
Modelica.Units.SI.ThermalConductance	UA_nominal (from AHUParameters)		Thermal conductance at nominal flow for sensible heat, used to compute time constant
Real	r_nominal (from AHUParameters)	2/3	Ratio between air-side and water-side convective heat transfer coefficient
Dynamics › Conservation equations
Modelica.Fluid.Types.Dynamics	energyDynamics (from AHUParameters)	Modelica.Fluid.Types.Dynamics.DynamicFreeInitial	Type of energy balance: dynamic (3 initialization options) or steady state
Flow Coefficient
Buildings.Fluid.Types.CvTypes	CvData (from ValveParameters)	Buildings.Fluid.Types.CvTypes.OpPoint	Selection of flow coefficient
Real	Kv (from ValveParameters)		Kv (metric) flow coefficient [m3/h/(bar)^(1/2)]
Real	Cv (from ValveParameters)		Cv (US) flow coefficient [USG/min/(psi)^(1/2)]
Modelica.Units.SI.Area	Av (from ValveParameters)		Av (metric) flow coefficient
Pressure-flow linearization
Real	deltaM (from ValveParameters)	0.02	Fraction of nominal flow rate where linearization starts, if y=1
Advanced › Nominal condition
Modelica.Units.SI.Density	rhoStd (from ValveParameters)		Inlet density for which valve coefficients are defined
Flow resistance › Medium 1
Boolean	computeFlowResistance1 (from FourPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp1 (from FourPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance1 (from FourPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM1 (from FourPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Flow resistance › Medium 2
Boolean	computeFlowResistance2 (from FourPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp2 (from FourPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	linearizeFlowResistance2 (from FourPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM2 (from FourPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Initialization
Medium2.AbsolutePressure	p_start	Medium2.p_default	Start value of pressure
Medium2.Temperature	T_start	Medium2.T_default	Start value of temperature
Medium2.MassFraction[Medium2.nX]	X_start	Medium2.X_default	Start value of mass fractions m_i/m
Medium2.ExtraProperty[Medium2.nC]	C_start	fill(0, Medium2.nC)	Start value of trace substances
Medium2.ExtraProperty[Medium2.nC]	C_nominal	fill(1E-2, Medium2.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Valve
Real	l	0.0001	Valve leakage, l=Kv(y=0)/Kv(y=1)
Dynamics › Valve
Boolean	use_strokeTime	false	Set to true to continuously open and close valve on the water-side
Modelica.Units.SI.Time	strokeTime	120	Time needed to open or close valve
Modelica.Blocks.Types.Init	initValve	Modelica.Blocks.Types.Init.InitialOutput	Type of initialization (no init/steady state/initial state/initial output)
Real	yValve_start	1	Initial value of output
Fan
Buildings.Fluid.Types.InputType	inputType	Buildings.Fluid.Types.InputType.Continuous	Control input type
Boolean	addPowerToMedium	true	Set to false to avoid any power (=heat and flow work) being added to medium (may give simpler equations)
Dynamics › Fan
Modelica.Units.SI.Time	tauFan	1	Time constant at nominal flow (if energyDynamics <> SteadyState)
Boolean	use_riseTime	true	Set to true to continuously change motor speed
Modelica.Units.SI.Time	riseTime	30	Time needed to change motor speed between zero and full speed
Modelica.Blocks.Types.Init	initFan	Modelica.Blocks.Types.Init.InitialOutput	Type of initialization (no init/steady state/initial state/initial output)
Real	yFan_start	0	Initial value of speed

Connectors

Type	Name	Description
Modelica.Fluid.Interfaces.FluidPort_a	port_a1 (from PartialFourPort)	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
Modelica.Fluid.Interfaces.FluidPort_b	port_b1 (from PartialFourPort)	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
Modelica.Fluid.Interfaces.FluidPort_a	port_a2 (from PartialFourPort)	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
Modelica.Fluid.Interfaces.FluidPort_b	port_b2 (from PartialFourPort)	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)
Modelica.Blocks.Interfaces.RealInput	uVal	Actuator position (0: closed, 1: open) on water side
Modelica.Blocks.Interfaces.RealInput	uFan	Continuous input signal for the fan
Modelica.Blocks.Interfaces.RealOutput	PFan	Electrical power consumed by the fan
Modelica.Blocks.Interfaces.RealOutput	yVal	Actual valve position
Modelica.Blocks.Interfaces.IntegerInput	stage	Stage input signal for the pressure head

Components

Type	Name	Default	Description
Medium1.MassFlowRate	m1_flow (from PartialFourPortInterface)	port_a1.m_flow	Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction)
Modelica.Units.SI.PressureDifference	dp1 (from PartialFourPortInterface)	port_a1.p - port_b1.p	Pressure difference between port_a1 and port_b1
Medium2.MassFlowRate	m2_flow (from PartialFourPortInterface)	port_a2.m_flow	Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction)
Modelica.Units.SI.PressureDifference	dp2 (from PartialFourPortInterface)	port_a2.p - port_b2.p	Pressure difference between port_a2 and port_b2
Medium1.ThermodynamicState	sta_a1 (from PartialFourPortInterface)	if allowFlowReversal1 then Medium1.setState_phX(port_a1.p, noEvent(actualStream(port_a1.h_outflow)), noEvent(actualStream(port_a1.Xi_outflow))) else Medium1.setState_phX(port_a1.p, inStream(port_a1.h_outflow), inStream(port_a1.Xi_outflow))	Medium properties in port_a1
Medium1.ThermodynamicState	sta_b1 (from PartialFourPortInterface)	if allowFlowReversal1 then Medium1.setState_phX(port_b1.p, noEvent(actualStream(port_b1.h_outflow)), noEvent(actualStream(port_b1.Xi_outflow))) else Medium1.setState_phX(port_b1.p, port_b1.h_outflow, port_b1.Xi_outflow)	Medium properties in port_b1
Medium2.ThermodynamicState	sta_a2 (from PartialFourPortInterface)	if allowFlowReversal2 then Medium2.setState_phX(port_a2.p, noEvent(actualStream(port_a2.h_outflow)), noEvent(actualStream(port_a2.Xi_outflow))) else Medium2.setState_phX(port_a2.p, inStream(port_a2.h_outflow), inStream(port_a2.Xi_outflow))	Medium properties in port_a2
Medium2.ThermodynamicState	sta_b2 (from PartialFourPortInterface)	if allowFlowReversal2 then Medium2.setState_phX(port_b2.p, noEvent(actualStream(port_b2.h_outflow)), noEvent(actualStream(port_b2.Xi_outflow))) else Medium2.setState_phX(port_b2.p, port_b2.h_outflow, port_b2.Xi_outflow)	Medium properties in port_b2
Fluid.HeatExchangers.WetCoilEffectivenessNTU	cooCoi		Cooling coil
Buildings.Fluid.Movers.BaseClasses.PartialFlowMachine	fan
Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValveKv	watVal

Revisions

June 30, 2021, by Antoine Gautier:
Changed cooling coil model. This is for issue #2549.
April 9, 2021, by Kathryn Hinkelman:
Removed kFixed redundancies. See IBPSA, #1472.
April 14, 2020, by Michael Wetter:
Changed homotopyInitialization to a constant.
This is for IBPSA, #1341.
May 12, 2017 by Yangyang Fu:
First implementation.