Buildings.Fluid.Sensors.BaseClasses

Information

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

Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).

Package Content

Name	Description
PartialAbsoluteSensor	Partial component to model a sensor that measures a potential variable
PartialDynamicFlowSensor	Partial component to model sensors that measure flow properties using a dynamic model
PartialFlowSensor	Partial component to model sensors that measure flow properties

Buildings.Fluid.Sensors.BaseClasses.PartialAbsoluteSensor

Information

Partial component to model an absolute sensor. The component can be used for pressure sensor models. Use for other properties such as temperature or density is discouraged, because the enthalpy at the connector can have different meanings, depending on the connection topology. For these properties, use Buildings.Fluid.Sensors.BaseClasses.PartialFlowSensor.

Connectors

Type	Name	Description
FluidPort_a	port

Modelica definition

partial model PartialAbsoluteSensor 
  "Partial component to model a sensor that measures a potential variable"

  replaceable package Medium=Modelica.Media.Interfaces.PartialMedium 
    "Medium in the sensor";

  Modelica.Fluid.Interfaces.FluidPort_a port(redeclare package Medium=Medium, m_flow(min=0));

equation 
  port.m_flow = 0;
  port.h_outflow = 0;
  port.Xi_outflow = zeros(Medium.nXi);
  port.C_outflow = zeros(Medium.nC);
end PartialAbsoluteSensor;

Buildings.Fluid.Sensors.BaseClasses.PartialDynamicFlowSensor

Information

Partial component to model a sensor that measures any intensive properties of a flow, e.g., to get temperature or density in the flow between fluid connectors.

The sensor computes a gain that is zero at zero mass flow rate. This avoids fast transients if the flow is close to zero, thereby improving the numerical efficiency.

Extends from PartialFlowSensor (Partial component to model sensors that measure flow properties).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Time	tau	1	Time constant at nominal flow rate [s]
Nominal condition
MassFlowRate	m_flow_nominal		Nominal mass flow rate, used for regularization near zero flow [kg/s]
Advanced
MassFlowRate	m_flow_small	1E-4*m_flow_nominal	For bi-directional flow, temperature is regularized in the region |m_flow| < m_flow_small (m_flow_small > 0 required) [kg/s]
Initialization
Init	initType	Modelica.Blocks.Types.Init.N...	Type of initialization (InitialState and InitialOutput are identical)
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

partial model PartialDynamicFlowSensor 
  "Partial component to model sensors that measure flow properties using a dynamic model"
  extends PartialFlowSensor;
  parameter Modelica.SIunits.Time tau(min=0) = 1 
    "Time constant at nominal flow rate";
  parameter Modelica.Blocks.Types.Init initType = Modelica.Blocks.Types.Init.NoInit 
    "Type of initialization (InitialState and InitialOutput are identical)";
protected 
  Real k(start=1) 
    "Gain to take flow rate into account for sensor time constant";
  final parameter Boolean dynamic = tau > 1E-10 or tau < -1E-10 
    "Flag, true if the sensor is a dynamic sensor";
  Real mNor_flow "Normalized mass flow rate";
equation 
  if dynamic then
    mNor_flow = port_a.m_flow/m_flow_nominal;
    k = Modelica.Fluid.Utilities.regStep(x=port_a.m_flow,
                                         y1= mNor_flow,
                                         y2=-mNor_flow,
                                         x_small=m_flow_small);
  else
    mNor_flow = 1;
    k = 1;
  end if;
end PartialDynamicFlowSensor;

Buildings.Fluid.Sensors.BaseClasses.PartialFlowSensor

Information

Partial component to model a sensor. The sensor is ideal. It does not influence mass, energy, species or substance balance, and it has no flow friction.

Extends from Modelica.Fluid.Interfaces.PartialTwoPort (Partial component with two ports).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Nominal condition
MassFlowRate	m_flow_nominal		Nominal mass flow rate, used for regularization near zero flow [kg/s]
Advanced
MassFlowRate	m_flow_small	1E-4*m_flow_nominal	For bi-directional flow, temperature is regularized in the region |m_flow| < m_flow_small (m_flow_small > 0 required) [kg/s]
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

partial model PartialFlowSensor 
  "Partial component to model sensors that measure flow properties"
  extends Modelica.Fluid.Interfaces.PartialTwoPort;
  parameter Medium.MassFlowRate m_flow_nominal(min=0) 
    "Nominal mass flow rate, used for regularization near zero flow";
  parameter Medium.MassFlowRate m_flow_small(min=0) = 1E-4*m_flow_nominal 
    "For bi-directional flow, temperature is regularized in the region |m_flow| < m_flow_small (m_flow_small > 0 required)";
equation 
  // mass balance
  0 = port_a.m_flow + port_b.m_flow;
  // momentum equation (no pressure loss)
  port_a.p = port_b.p;
  // isenthalpic state transformation (no storage and no loss of energy)
  port_a.h_outflow = inStream(port_b.h_outflow);
  port_b.h_outflow = inStream(port_a.h_outflow);
  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 PartialFlowSensor;