modelPartialDamperExponential

Partial model for air dampers with exponential opening characteristics

Extends from IBPSA.Fluid.BaseClasses.PartialResistance (Partial model for a hydraulic resistance), IBPSA.Fluid.Actuators.BaseClasses.ActuatorSignal (Partial model that implements the filtered opening for valves and dampers).

Information

Partial model for air dampers with exponential opening characteristics. This is the base model for air dampers and variable air volume flow boxes. The model implements the functions that relate the opening signal, the pressure drop and the mass flow rate. The model also defines parameters that are used by different air damper models.

For a description of the opening characteristics and typical parameter values, see the damper model IBPSA.Fluid.Actuators.Dampers.Exponential.

Parameters

Type	Name	Default	Description
Modelica.SIunits.MassFlowRate	m_flow_turbulent (from PartialResistance)		Turbulent flow if \|m_flow\| >= m_flow_turbulent
Boolean	use_deltaM	true	Set to true to use deltaM for turbulent transition, else ReC is used
Real	deltaM	0.3	Fraction of nominal mass flow rate where transition to turbulent occurs
Modelica.SIunits.Velocity	v_nominal	1	Nominal face velocity
Modelica.SIunits.Area	A	m_flow_nominal/rho_default/v_nominal	Face area
Boolean	roundDuct	false	Set to true for round duct, false for square cross section
Real	ReC	4000	Reynolds number where transition to turbulent starts
Real	kFixed		Flow coefficient of fixed resistance that may be in series with damper, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2).
Assumptions
Boolean	allowFlowReversal (from PartialTwoPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Nominal condition
Modelica.SIunits.MassFlowRate	m_flow_nominal (from PartialTwoPortInterface)		Nominal mass flow rate
Modelica.SIunits.PressureDifference	dp_nominal (from PartialResistance)		Pressure drop at nominal mass flow rate
Advanced
Modelica.SIunits.MassFlowRate	m_flow_small (from PartialTwoPortInterface)	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow
Boolean	from_dp (from PartialResistance)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	homotopyInitialization (from PartialResistance)	true	= true, use homotopy method
Boolean	linearized (from PartialResistance)	false	= true, use linear relation between m_flow and dp for any flow rate
Boolean	use_constant_density	true	Set to true to use constant density for flow friction
Advanced › Diagnostics
Boolean	show_T (from PartialTwoPortInterface)	false	= true, if actual temperature at port is computed
Dynamics › Filtered opening
Boolean	use_inputFilter (from ActuatorSignal)	true	= true, if opening is filtered with a 2nd order CriticalDamping filter
Modelica.SIunits.Time	riseTime (from ActuatorSignal)	120	Rise time of the filter (time to reach 99.6 % of an opening step)
Integer	order (from ActuatorSignal)	2	Order of filter
Modelica.Blocks.Types.Init	init (from ActuatorSignal)	Modelica.Blocks.Types.Init.InitialOutput	Type of initialization (no init/steady state/initial state/initial output)
Real	y_start (from ActuatorSignal)	1	Initial value of output
Damper coefficients
Real	a	-1.51	Coefficient a for damper characteristics
Real	b	0.105*90	Coefficient b for damper characteristics
Real	yL	15/90	Lower value for damper curve
Real	yU	55/90	Upper value for damper curve
Real	k0	1E6	Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure
Real	k1	0.45	Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Connectors

Type	Name	Description
Modelica.Fluid.Interfaces.FluidPort_a	port_a (from PartialTwoPort)	Fluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_b	port_b (from PartialTwoPort)	Fluid connector b (positive design flow direction is from port_a to port_b)
Modelica.Blocks.Interfaces.RealInput	y (from ActuatorSignal)	Actuator position (0: closed, 1: open)
Modelica.Blocks.Interfaces.RealOutput	y_actual (from ActuatorSignal)	Actual valve position

Components

Type	Name	Default	Description
Modelica.SIunits.MassFlowRate	m_flow (from PartialTwoPortInterface)	port_a.m_flow	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction)
Modelica.SIunits.PressureDifference	dp (from PartialTwoPortInterface)	port_a.p - port_b.p	Pressure difference between port_a and port_b
Medium.ThermodynamicState	sta_a (from PartialTwoPortInterface)	Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow)))	Medium properties in port_a
Medium.ThermodynamicState	sta_b (from PartialTwoPortInterface)	Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow)))	Medium properties in port_b
Medium.Density	rho		Medium density
Real	kDam		Flow coefficient of damper, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)
Real	k		Flow coefficient of damper plus fixed resistance, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)

Revisions

March 22, 2017, by Michael Wetter:
Added back v_nominal, but set the assignment of A to be final. This allows scaling the model with m_flow_nominal, which is generally known in the flow leg, and v_nominal, for which a default value can be specified.
This is for #544.
October 12, 2016 by David Blum:
Removed parameter v_nominal and variable area, to simplify parameterization of the model. Also added assertion statements upon initialization for parameters k0 and k1 so that they fall within suggested ranges found in ASHRAE 825-RP. This is for #544.
January 27, 2015 by Michael Wetter:
Set Evaluate=true for use_constant_density. This is a structural parameter. Adding this annotation leads to fewer numerical Jacobians for Buildings.Examples.VAVReheat.ClosedLoop with Buildings.Media.PerfectGases.MoistAirUnsaturated.
December 14, 2012 by Michael Wetter:
Renamed protected parameters for consistency with the naming conventions.
January 16, 2012 by Michael Wetter:
To simplify object inheritance tree, revised base classes IBPSA.Fluid.BaseClasses.PartialResistance, IBPSA.Fluid.Actuators.BaseClasses.PartialTwoWayValve, IBPSA.Fluid.Actuators.BaseClasses.PartialDamperExponential, IBPSA.Fluid.Actuators.BaseClasses.PartialActuator and model IBPSA.Fluid.FixedResistances.PressureDrop.
August 5, 2011, by Michael Wetter:
Moved linearized pressure drop equation from the function body to the equation section. With the previous implementation, the symbolic processor may not rearrange the equations, which can lead to coupled equations instead of an explicit solution.
June 22, 2008 by Michael Wetter:
Extended range of control signal from 0 to 1 by implementing the function exponentialDamper.
June 10, 2008 by Michael Wetter:
First implementation.