modelDifferenceEnthalpyFlowRate

Sensor outputting the difference between two enthalpy flow rates

Extends from Fluid.Interfaces.PartialFourPortInterface (Partial model with four ports and declaration of quantities that are used by many models).

Information

This model outputs the difference in enthalpy flow rate between two different streams: ΔḢ = ṁ₁ h₁ - ṁ₂ h₂. Optionally the time integral of this quantity can be output. The sensor is ideal, i.e., it does not influence the fluid.

By default

the parameter tau is zero, so the specific enthalpy that is used to compute each enthalpy flow rate is computed in steady-state,
the medium is the same in both streams but the model allows for specifying two different media to represent for instance the gaseous and liquid state of the same substance.

Parameters

Type	Name	Default	Description
Boolean	have_integrator	false	Set to true to output the time integral
Modelica.Units.SI.Time	tau	0	Time constant at nominal flow rate
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
Boolean	allowFlowReversal	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
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		Nominal mass flow rate
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
Medium1.MassFlowRate	m_flow_small	1E-4*abs(m_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
Initialization
Modelica.Blocks.Types.Init	initType	Modelica.Blocks.Types.Init.InitialState	Type of initialization (InitialState and InitialOutput are identical)
Modelica.Units.SI.SpecificEnthalpy	h1_out_start	Medium1.specificEnthalpy_pTX(p = Medium1.p_default, T = Medium1.T_default, X = Medium1.X_default)	Initial or guess value of measured specific enthalpy
Modelica.Units.SI.SpecificEnthalpy	h2_out_start	Medium2.specificEnthalpy_pTX(p = Medium2.p_default, T = Medium2.T_default, X = Medium2.X_default)	Initial or guess value of measured specific enthalpy

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)
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	dH_flow	Difference in enthalpy flow rate between stream 1 and 2
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	E	Time integral of enthalpy flow rate difference between stream 1 and 2

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.Sensors.EnthalpyFlowRate	senEntFlo1		Enthalpy flow rate of fluid stream 1
Fluid.Sensors.EnthalpyFlowRate	senEntFlo2		Enthalpy flow rate of fluid stream 2
Buildings.Controls.OBC.CDL.Reals.Subtract	dif		Compute the difference
Modelica.Blocks.Continuous.Integrator	int		Time integral computation

Revisions

October 8, 2020, by Antoine Gautier:
First implementation.