Buildings.Fluids.HeatExchangers

Package with heat exchanger models

Information

This package contains models for heat exchangers with and without humidity condensation.

Package Content

Name Description

BaseClasses Package with base classes for heat exchanger models

ConstantEffectiveness Heat exchanger with constant effectiveness

CoolingTowers Package with cooling tower models

DryCoilDiscretized Heat exchanger with discretization along the flow path

DryHexHAInput Simple heat exchanger with convective heat transfer as input

Examples Collection of models that illustrate model use and test models

HeaterCoolerIdeal Ideal electric heater or cooler, no losses, no dynamics

Radiators Package with radiators of hydronic space heating systems

WetCoilDiscretized Coil with condensation

Name	Description
BaseClasses	Package with base classes for heat exchanger models
ConstantEffectiveness	Heat exchanger with constant effectiveness
CoolingTowers	Package with cooling tower models
DryCoilDiscretized	Heat exchanger with discretization along the flow path
DryHexHAInput	Simple heat exchanger with convective heat transfer as input
Examples	Collection of models that illustrate model use and test models
HeaterCoolerIdeal	Ideal electric heater or cooler, no losses, no dynamics
Radiators	Package with radiators of hydronic space heating systems
WetCoilDiscretized	Coil with condensation

Buildings.Fluids.HeatExchangers.ConstantEffectiveness

Heat exchanger with constant effectiveness

Buildings.Fluids.HeatExchangers.ConstantEffectiveness

Information

Model for a heat exchanger with constant effectiveness.

This model transfers heat in the amount of

  Q = Q_max * eps,

where eps is a constant effectiveness and Q_max is the maximum heat that can be transferred.

For a heat and moisture exchanger, use Buildings.Fluids.MassExchangers.ConstantEffectiveness instead of this model.

Extends from Fluids.Interfaces.PartialStaticFourPortHeatMassTransfer (Partial element transporting two fluid streams between four ports without storing mass or energy), Buildings.BaseClasses.BaseIcon (Base icon).

Parameters

Type	Name	Default	Description
replaceable package Medium_1	Modelica.Media.Interfaces.Pa...	Medium 1 in the component
replaceable package Medium_2	Modelica.Media.Interfaces.Pa...	Medium 2 in the component
Real	eps	0.8	Heat exchanger effectiveness
Nominal condition
MassFlowRate	m0_flow_1		Nominal mass flow rate [kg/s]
MassFlowRate	m0_flow_2	m0_flow_1	Nominal mass flow rate [kg/s]
Initialization
MassFlowRate	m_flow_1.start	0	Mass flow rate from port_a1 to port_b1 (m_flow_1 > 0 is design flow direction) [kg/s]
Pressure	dp_1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m_flow_2.start	0	Mass flow rate from port_a2 to port_b2 (m_flow_2 > 0 is design flow direction) [kg/s]
Pressure	dp_2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
Assumptions
Boolean	allowFlowReversal_1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal_2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_1_small	1E-4*m0_flow_1	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m_flow_2_small	1E-4*m0_flow_2	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed
Initialization
AbsolutePressure	p_a1_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b1_start	p_a1_start	Guess value for outlet pressure [Pa]
AbsolutePressure	p_a2_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b2_start	p_a2_start	Guess value for outlet pressure [Pa]

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)

Modelica definition

model ConstantEffectiveness 
  "Heat exchanger with constant effectiveness"
  extends Fluids.Interfaces.PartialStaticFourPortHeatMassTransfer;
  extends Buildings.BaseClasses.BaseIcon;
  parameter Real eps(min=0, max=1) = 0.8 "Heat exchanger effectiveness";

  Modelica.SIunits.Temperature T_in1 "Inlet temperature medium 1";
  Modelica.SIunits.Temperature T_in2 "Inlet temperature medium 2";
  Modelica.SIunits.ThermalConductance C_flow_1 
    "Heat capacity flow rate medium 1";
  Modelica.SIunits.ThermalConductance C_flow_2 
    "Heat capacity flow rate medium 2";
  Modelica.SIunits.ThermalConductance CMin_flow(min=0) 
    "Minimum heat capacity flow rate";
  Modelica.SIunits.HeatFlowRate QMax_flow "Maximum heat flow rate";

equation 
  // Definitions for heat transfer effectiveness model
  T_in1 = if m_flow_1 >= 0 then sta_a1.T else sta_b1.T;
  T_in2 = if m_flow_2 >= 0 then sta_a2.T else sta_b2.T;

  // The specific heat capacity is computed using the state of the
  // medium at port_a. For forward flow, this is correct, for reverse flow,
  // this is an approximation.
  C_flow_1 = abs(m_flow_1)* Medium_1.specificHeatCapacityCp(sta_a1);
  C_flow_2 = abs(m_flow_2)* Medium_2.specificHeatCapacityCp(sta_a2);

  CMin_flow = min(C_flow_1, C_flow_2);
  QMax_flow = CMin_flow * (T_in2 - T_in1);

  // transferred heat
  Q_flow_1 = eps * QMax_flow;
  0 = Q_flow_1 + Q_flow_2;

  // no mass exchange
  mXi_flow_1 = zeros(Medium_1.nXi);
  mXi_flow_2 = zeros(Medium_2.nXi);

  // no pressure drop
  dp_1 = 0;
  dp_2 = 0;
end ConstantEffectiveness;

Buildings.Fluids.HeatExchangers.DryCoilDiscretized

Heat exchanger with discretization along the flow path

Buildings.Fluids.HeatExchangers.DryCoilDiscretized

Information

Model of a discretized coil with no water vapor condensation. The coil consists of nReg registers that are perpendicular to the air flow path. Each register consists of nPipPar parallel pipes, and each pipe can be divided into nPipSeg pipe segments along the pipe length. Thus, the smallest element of the coil consists of a pipe segment. These pipe segments are modeled by the instance ele. Each element has a state variable for the metal. Depending on the value of the boolean parameters steadyState_1 and steadyState_2, the fluid states are modeled dynamically or in steady state. If the parameter steadyStateDuctConnection is set the false then a mixing volume of length dl is added to the duct connection. This can help reducing the dimension of the nonlinear system of equations.

The convective heat transfer coefficients can, for each fluid individually, be computed as a function of the flow rate and/or the temperature, or assigned to a constant. This computation is done in the instance hA.

In this model, the water (or liquid) flow path needs to be connected to port_a1 and port_b1, and the air flow path need to be connected to the other two ports.

To model humidity condensation, use the model Buildings.Fluids.HeatExchangers.WetCoilDiscretized instead of this model, as this model computes only sensible heat transfer.

Extends from Fluids.Interfaces.PartialStaticFourPortInterface (Partial element transporting fluid between two ports without storing mass or energy).

Parameters

Type Name Default Description

replaceable package Medium_1 Modelica.Media.Interfaces.Pa... Medium 1 in the component

replaceable package Medium_2 Modelica.Media.Interfaces.Pa... Medium 2 in the component

Nominal condition

MassFlowRate m0_flow_1 Nominal mass flow rate [kg/s]

MassFlowRate m0_flow_2 m0_flow_1 Nominal mass flow rate [kg/s]

TemperatureDifference dT0 10 Temperature difference [K]

HeatFlowRate Q0_flow 1000 Heat transfer at dT0 [W]

ThermalConductance UA0 Q0_flow/dT0 Thermal conductance at nominal flow, used to compute heat capacity [W/K]

Pressure dp0_1 Pressure drop for all pipes [Pa]

Pressure dp0_2 Pressure drop inside duct [Pa]

Time tau_1 20 Time constant at nominal flow for medium 1 [s]

Time tau_2 1 Time constant at nominal flow for medium 2 [s]

Time tau_m 20 Time constant of metal at nominal UA value [s]

Initialization

MassFlowRate m_flow_1.start 0 Mass flow rate from port_a1 to port_b1 (m_flow_1 > 0 is design flow direction) [kg/s]

Pressure dp_1.start 0 Pressure difference between port_a1 and port_b1 [Pa]

MassFlowRate m_flow_2.start 0 Mass flow rate from port_a2 to port_b2 (m_flow_2 > 0 is design flow direction) [kg/s]

Pressure dp_2.start 0 Pressure difference between port_a2 and port_b2 [Pa]

MassFlowRate mStart_flow_a1 m0_flow_1 Guess value for mass flow rate at port_a1 [kg/s]

MassFlowRate mStart_flow_a2 m0_flow_2 Guess value for mass flow rate at port_a2 [kg/s]

Geometry

Integer nReg 2 Number of registers

Integer nPipPar 3 Number of parallel pipes in each register

Integer nPipSeg 4 Number of pipe segments per register used for discretization

Length dh_1 0.025 Hydraulic diameter for a single pipe [m]

Length dh_2 1 Hydraulic diameter for duct [m]

Assumptions

Boolean allowFlowReversal_1 system.allowFlowReversal = true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)

Boolean allowFlowReversal_2 system.allowFlowReversal = true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)

Dynamics

Dynamics energyDynamics_1 Modelica_Fluid.Types.Dynamic... Default formulation of energy balances for volume 1

Dynamics energyDynamics_2 Modelica_Fluid.Types.Dynamic... Default formulation of energy balances for volume 2

Dynamics ductConnectionDynamics Modelica_Fluid.Types.Dynamic... Default formulation of energy balances for duct connection

Length dl 0.3 Length of mixing volume for duct connection [m]

Advanced

MassFlowRate m_flow_1_small 1E-4*m0_flow_1 Small mass flow rate for regularization of zero flow [kg/s]

MassFlowRate m_flow_2_small 1E-4*m0_flow_2 Small mass flow rate for regularization of zero flow [kg/s]

Boolean from_dp_1 false = true, use m_flow = f(dp) else dp = f(m_flow)

Boolean from_dp_2 false = true, use m_flow = f(dp) else dp = f(m_flow)

Real deltaM_1 0.3 Fraction of nominal mass flow rate where transition to laminar occurs

Real deltaM_2 0.3 Fraction of nominal mass flow rate where transition to laminar occurs

Boolean linearized_1 false = true, use linear relation between m_flow and dp for any flow rate

Boolean linearized_2 false = true, use linear relation between m_flow and dp for any flow rate

Boolean use_dh_1 false Set to true to specify hydraulic diameter for pipe pressure drop

Boolean use_dh_2 false Set to true to specify hydraulic diameter for duct pressure drop)

Real ReC_1 4000 Reynolds number where transition to laminar starts inside pipes

Real ReC_2 4000 Reynolds number where transition to laminar starts inside ducts

Diagnostics

Boolean show_V_flow true = true, if volume flow rate at inflowing port is computed

Initialization

AbsolutePressure p_a1_start system.p_start Guess value for inlet pressure [Pa]

AbsolutePressure p_b1_start p_a1_start Guess value for outlet pressure [Pa]

AbsolutePressure p_a2_start system.p_start Guess value for inlet pressure [Pa]

AbsolutePressure p_b2_start p_a2_start Guess value for outlet pressure [Pa]

Heat transfer

Boolean waterSideFlowDependent false Set to false to make water-side hA independent of mass flow rate

Boolean airSideFlowDependent false Set to false to make air-side hA independent of mass flow rate

Boolean waterSideTemperatureDependent false Set to false to make water-side hA independent of temperature

Type	Name	Default	Description
replaceable package Medium_1	Modelica.Media.Interfaces.Pa...	Medium 1 in the component
replaceable package Medium_2	Modelica.Media.Interfaces.Pa...	Medium 2 in the component
Nominal condition
MassFlowRate	m0_flow_1		Nominal mass flow rate [kg/s]
MassFlowRate	m0_flow_2	m0_flow_1	Nominal mass flow rate [kg/s]
TemperatureDifference	dT0	10	Temperature difference [K]
HeatFlowRate	Q0_flow	1000	Heat transfer at dT0 [W]
ThermalConductance	UA0	Q0_flow/dT0	Thermal conductance at nominal flow, used to compute heat capacity [W/K]
Pressure	dp0_1		Pressure drop for all pipes [Pa]
Pressure	dp0_2		Pressure drop inside duct [Pa]
Time	tau_1	20	Time constant at nominal flow for medium 1 [s]
Time	tau_2	1	Time constant at nominal flow for medium 2 [s]
Time	tau_m	20	Time constant of metal at nominal UA value [s]
Initialization
MassFlowRate	m_flow_1.start	0	Mass flow rate from port_a1 to port_b1 (m_flow_1 > 0 is design flow direction) [kg/s]
Pressure	dp_1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m_flow_2.start	0	Mass flow rate from port_a2 to port_b2 (m_flow_2 > 0 is design flow direction) [kg/s]
Pressure	dp_2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
MassFlowRate	mStart_flow_a1	m0_flow_1	Guess value for mass flow rate at port_a1 [kg/s]
MassFlowRate	mStart_flow_a2	m0_flow_2	Guess value for mass flow rate at port_a2 [kg/s]
Geometry
Integer	nReg	2	Number of registers
Integer	nPipPar	3	Number of parallel pipes in each register
Integer	nPipSeg	4	Number of pipe segments per register used for discretization
Length	dh_1	0.025	Hydraulic diameter for a single pipe [m]
Length	dh_2	1	Hydraulic diameter for duct [m]
Assumptions
Boolean	allowFlowReversal_1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal_2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics_1	Modelica_Fluid.Types.Dynamic...	Default formulation of energy balances for volume 1
Dynamics	energyDynamics_2	Modelica_Fluid.Types.Dynamic...	Default formulation of energy balances for volume 2
Dynamics	ductConnectionDynamics	Modelica_Fluid.Types.Dynamic...	Default formulation of energy balances for duct connection
Length	dl	0.3	Length of mixing volume for duct connection [m]
Advanced
MassFlowRate	m_flow_1_small	1E-4*m0_flow_1	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m_flow_2_small	1E-4*m0_flow_2	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	from_dp_1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	from_dp_2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	deltaM_1	0.3	Fraction of nominal mass flow rate where transition to laminar occurs
Real	deltaM_2	0.3	Fraction of nominal mass flow rate where transition to laminar occurs
Boolean	linearized_1	false	= true, use linear relation between m_flow and dp for any flow rate
Boolean	linearized_2	false	= true, use linear relation between m_flow and dp for any flow rate
Boolean	use_dh_1	false	Set to true to specify hydraulic diameter for pipe pressure drop
Boolean	use_dh_2	false	Set to true to specify hydraulic diameter for duct pressure drop)
Real	ReC_1	4000	Reynolds number where transition to laminar starts inside pipes
Real	ReC_2	4000	Reynolds number where transition to laminar starts inside ducts
Diagnostics
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed
Initialization
AbsolutePressure	p_a1_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b1_start	p_a1_start	Guess value for outlet pressure [Pa]
AbsolutePressure	p_a2_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b2_start	p_a2_start	Guess value for outlet pressure [Pa]
Heat transfer
Boolean	waterSideFlowDependent	false	Set to false to make water-side hA independent of mass flow rate
Boolean	airSideFlowDependent	false	Set to false to make air-side hA independent of mass flow rate
Boolean	waterSideTemperatureDependent	false	Set to false to make water-side hA independent of temperature

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)

Modelica definition

model DryCoilDiscretized 
  "Heat exchanger with discretization along the flow path"
  extends Fluids.Interfaces.PartialStaticFourPortInterface;


  parameter Modelica.SIunits.TemperatureDifference dT0(min=0) = 10 
    "Temperature difference";
  parameter Modelica.SIunits.HeatFlowRate Q0_flow(min=0) = 1000 
    "Heat transfer at dT0";
  parameter Modelica.SIunits.ThermalConductance UA0(min=0) = Q0_flow/dT0 
    "Thermal conductance at nominal flow, used to compute heat capacity";
  parameter Integer nReg(min=2)=2 "Number of registers";
  parameter Integer nPipPar(min=1) = 3 
    "Number of parallel pipes in each register";
  parameter Integer nPipSeg(min=1) = 4 
    "Number of pipe segments per register used for discretization";
  parameter Boolean from_dp_1 = false 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
  parameter Boolean from_dp_2 = false 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
  parameter Real deltaM_1(min=0) = 0.3 
    "Fraction of nominal mass flow rate where transition to laminar occurs";
  parameter Real deltaM_2(min=0) = 0.3 
    "Fraction of nominal mass flow rate where transition to laminar occurs";
  parameter Boolean linearized_1 = false 
    "= true, use linear relation between m_flow and dp for any flow rate";
  parameter Boolean linearized_2 = false 
    "= true, use linear relation between m_flow and dp for any flow rate";
  parameter Boolean use_dh_1 = false 
    "Set to true to specify hydraulic diameter for pipe pressure drop";
  parameter Boolean use_dh_2 = false 
    "Set to true to specify hydraulic diameter for duct pressure drop)";

  parameter Modelica_Fluid.Types.Dynamics energyDynamics_1=
    Modelica_Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for volume 1";
  parameter Modelica_Fluid.Types.Dynamics energyDynamics_2=
    Modelica_Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for volume 2";

  Buildings.Fluids.HeatExchangers.BaseClasses.CoilRegister hexReg[nReg](
    redeclare each package Medium_1 = Medium_1,
    redeclare each package Medium_2 = Medium_2,
    each final allowFlowReversal_1=allowFlowReversal_1,
    each final allowFlowReversal_2=allowFlowReversal_2,
    each final nPipPar=nPipPar,
    each final nPipSeg=nPipSeg,
    each final UA0=Q0_flow/dT0/nReg,
    each final m0_flow_1=m0_flow_1/nPipPar,
    each final m0_flow_2=m0_flow_1/nPipPar/nPipSeg,
    each tau_1=tau_1,
    each tau_2=tau_2,
    each tau_m=tau_m,
    each final energyDynamics_1=energyDynamics_1,
    each final energyDynamics_2=energyDynamics_2,
    each allowCondensation=allowCondensation) "Heat exchanger register";
  Buildings.Fluids.HeatExchangers.BaseClasses.PipeManifoldFixedResistance
    pipMan_a(
    redeclare package Medium = Medium_1,
    final nPipPar=nPipPar,
    final m0_flow=m0_flow_1,
    final dp0=dp0_1,
    final dh=dh_1,
    final ReC=ReC_1,
    final mStart_flow_a=mStart_flow_a1,
    final linearized=linearized_1,
    final use_dh=use_dh_1,
    final deltaM=deltaM_1,
    final from_dp=from_dp_1,
    final allowFlowReversal=allowFlowReversal_1) "Pipe manifold at port a";
  Buildings.Fluids.HeatExchangers.BaseClasses.PipeManifoldNoResistance pipMan_b(
    redeclare package Medium = Medium_1,
    final nPipPar=nPipPar,
    final mStart_flow_a=-mStart_flow_a1,
    final allowFlowReversal=allowFlowReversal_1) "Pipe manifold at port b";
  Buildings.Fluids.HeatExchangers.BaseClasses.DuctManifoldNoResistance ducMan_b(
    redeclare package Medium = Medium_2,
    final nPipPar=nPipPar,
    final nPipSeg=nPipSeg,
    final mStart_flow_a=-mStart_flow_a2,
    final allowFlowReversal=allowFlowReversal_2) "Duct manifold at port b";
  Buildings.Fluids.HeatExchangers.BaseClasses.DuctManifoldFixedResistance
    ducMan_a(
    redeclare package Medium = Medium_2,
    final nPipPar = nPipPar,
    final nPipSeg = nPipSeg,
    final m0_flow=m0_flow_2,
    final dp0=dp0_2,
    final dh=dh_2,
    final ReC=ReC_2,
    final dl=dl,
    final mStart_flow_a=mStart_flow_a2,
    final linearized=linearized_2,
    final use_dh=use_dh_2,
    final deltaM=deltaM_2,
    final from_dp=from_dp_2,
    final allowFlowReversal=allowFlowReversal_2,
    final energyDynamics=ductConnectionDynamics) "Duct manifold at port a";
public 
  parameter Modelica.SIunits.Length dh_1=0.025 
    "Hydraulic diameter for a single pipe";
  parameter Real ReC_1=4000 
    "Reynolds number where transition to laminar starts inside pipes";
  parameter Real ReC_2=4000 
    "Reynolds number where transition to laminar starts inside ducts";
  parameter Modelica.SIunits.MassFlowRate m0_flow_1 
    "Mass flow rate at port_a1 for all pipes";
  parameter Modelica.SIunits.Pressure dp0_1 "Pressure drop for all pipes";
  parameter Modelica.SIunits.Length dh_2=1 "Hydraulic diameter for duct";
  parameter Modelica.SIunits.MassFlowRate m0_flow_2 
    "Mass flow rate at port_a_2 for duct";
  parameter Modelica.SIunits.Pressure dp0_2 "Pressure drop inside duct";
  Modelica.SIunits.HeatFlowRate Q_flow_1 
    "Heat transfered from solid into medium 1";
  Modelica.SIunits.HeatFlowRate Q_flow_2 
    "Heat transfered from solid into medium 2";
  parameter Modelica.SIunits.Time tau_1=20 
    "Time constant at nominal flow for medium 1";
  parameter Modelica.SIunits.Time tau_2=1 
    "Time constant at nominal flow for medium 2";
  parameter Modelica.SIunits.Time tau_m=20 
    "Time constant of metal at nominal UA value";

protected 
  BaseClasses.CoilHeader hea1[nReg/2](
      redeclare each final package Medium = Medium_1,
      each final nPipPar = nPipPar,
      each final mStart_flow_a=mStart_flow_a1,
      each allowFlowReversal=allowFlowReversal_1) if 
      nReg > 1 "Pipe header to redirect flow into next register";
  BaseClasses.CoilHeader hea2[nReg/2-1](
      redeclare each final package Medium = Medium_1,
      each final nPipPar = nPipPar,
      each final mStart_flow_a=mStart_flow_a1,
      each allowFlowReversal=allowFlowReversal_1) if 
      nReg > 2 "Pipe header to redirect flow into next register";
  Modelica.Blocks.Math.Gain gai_1(k=1/nReg) 
    "Gain medium-side 1 to take discretization into account";
  Modelica.Blocks.Math.Gain gai_2(k=1/nReg) 
    "Gain medium-side 2 to take discretization into account";
public 
  parameter Boolean waterSideFlowDependent = false 
    "Set to false to make water-side hA independent of mass flow rate";
  parameter Boolean airSideFlowDependent = false 
    "Set to false to make air-side hA independent of mass flow rate";
  parameter Boolean waterSideTemperatureDependent = false 
    "Set to false to make water-side hA independent of temperature";
  constant Boolean airSideTemperatureDependent = false 
    "Set to false to make air-side hA independent of temperature";
  BaseClasses.HADryCoil hA(
    final UA0=UA0,
    final m0_flow_a=m0_flow_2,
    final m0_flow_w=m0_flow_1,
    final waterSideTemperatureDependent=waterSideTemperatureDependent,
    final waterSideFlowDependent=waterSideFlowDependent,
    final airSideTemperatureDependent=airSideTemperatureDependent,
    final airSideFlowDependent=airSideFlowDependent) 
    "Model for convective heat transfer coefficient";
protected 
  constant Boolean allowCondensation = false 
    "Set to false to compute sensible heat transfer only";

protected 
  Modelica_Fluid.Sensors.TemperatureTwoPort temSen_1(
                                              redeclare package Medium = 
        Medium_1) "Temperature sensor";
  Modelica_Fluid.Sensors.MassFlowRate masFloSen_1(redeclare package Medium = 
        Medium_1) "Mass flow rate sensor";
  Modelica_Fluid.Sensors.TemperatureTwoPort temSen_2(
                                              redeclare package Medium = 
        Medium_2) "Temperature sensor";
  Modelica_Fluid.Sensors.MassFlowRate masFloSen_2(redeclare package Medium = 
        Medium_2) "Mass flow rate sensor";
public 
  parameter Modelica_Fluid.Types.Dynamics ductConnectionDynamics=
    Modelica_Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances for duct connection";
  parameter Modelica.SIunits.Length dl=0.3 
    "Length of mixing volume for duct connection";
  parameter Modelica.SIunits.MassFlowRate mStart_flow_a1=m0_flow_1 
    "Guess value for mass flow rate at port_a1";
  parameter Modelica.SIunits.MassFlowRate mStart_flow_a2=m0_flow_2 
    "Guess value for mass flow rate at port_a2";
initial equation 
  assert(dT0>0,     "Parameter dT0 is negative. Check heat exchanger parameters.");
  assert(Q0_flow>0, "Parameter Q0_flow is negative. Check heat exchanger parameters.");
equation 
  Q_flow_1 = sum(hexReg[i].Q_flow_1 for i in 1:nReg);
  Q_flow_2 = sum(hexReg[i].Q_flow_2 for i in 1:nReg);

  // air stream connections
  for i in 2:nReg loop
    connect(hexReg[i].port_a2, hexReg[i-1].port_b2);
  end for;
  connect(ducMan_a.port_b, hexReg[1].port_a2);
  connect(hexReg[nReg].port_b2, ducMan_b.port_b);
  connect(pipMan_a.port_b, hexReg[1].port_a1);
  connect(hexReg[nReg].port_b1, pipMan_b.port_b);
  connect(pipMan_b.port_a, port_b1);
  connect(ducMan_b.port_a, port_b2);
  for i in 1:2:nReg loop

  // header after first hex register
    connect(hexReg[i].port_b1, hea1[(i+1)/2].port_a);
    connect(hea1[(i+1)/2].port_b, hexReg[i+1].port_b1);
  end for;
  // header after 2nd hex register
  for i in 2:2:(nReg-1) loop
    connect(hexReg[i].port_a1, hea2[i/2].port_a);
    connect(hea2[i/2].port_b, hexReg[i+1].port_a1);
  end for;
  connect(masFloSen_1.m_flow, hA.m_flow_1);
  connect(port_a2, masFloSen_2.port_a);
  connect(masFloSen_2.port_b, temSen_2.port_a);
  connect(temSen_2.port_b, ducMan_a.port_a);
  connect(temSen_2.T, hA.T_2);
  connect(masFloSen_2.m_flow, hA.m_flow_2);
  connect(hA.hA_1, gai_1.u);
  connect(hA.hA_2, gai_2.u);
  for i in 1:nReg loop
    connect(gai_1.y, hexReg[i].Gc_1);
    connect(gai_2.y, hexReg[i].Gc_2);
  end for;
  connect(port_a1, masFloSen_1.port_a);
  connect(masFloSen_1.port_b, temSen_1.port_a);
  connect(temSen_1.port_b, pipMan_a.port_a);
  connect(temSen_1.T, hA.T_1);
end DryCoilDiscretized;

Buildings.Fluids.HeatExchangers.DryHexHAInput

Simple heat exchanger with convective heat transfer as input

Buildings.Fluids.HeatExchangers.DryHexHAInput

Information

Simple heat exchanger with convective heat transfer as input. The hA values are an input and energy storage in the metal and in the fluid is taken into account.

Extends from Fluids.Interfaces.PartialDynamicFourPortTransformer (Partial element transporting two fluid streams between four ports with storing mass or energy), Buildings.BaseClasses.BaseIcon (Base icon).

Parameters

Type Name Default Description

replaceable package Medium_1 Modelica.Media.Interfaces.Pa... Medium 1 in the component

replaceable package Medium_2 Modelica.Media.Interfaces.Pa... Medium 2 in the component

MixingVolumeDryAir vol_2 redeclare Buildings.Fluids.M... Volume for fluid 2

HeatCapacity C tau_m*UA0 Heat capacity of metal (= cp*m) [J/K]

Nominal condition

MassFlowRate m0_flow_1 Nominal mass flow rate [kg/s]

MassFlowRate m0_flow_2 m0_flow_1 Nominal mass flow rate [kg/s]

Time tau_1 60 Time constant at nominal flow [s]

Time tau_2 60 Time constant at nominal flow [s]

ThermalConductance UA0 Thermal conductance at nominal flow [W/K]

Time tau_m 2 Time constant of metal [s]

Initialization

MassFlowRate m_flow_1.start 0 Mass flow rate from port_a1 to port_b1 (m_flow_1 > 0 is design flow direction) [kg/s]

Pressure dp_1.start 0 Pressure difference between port_a1 and port_b1 [Pa]

MassFlowRate m_flow_2.start 0 Mass flow rate from port_a2 to port_b2 (m_flow_2 > 0 is design flow direction) [kg/s]

Pressure dp_2.start 0 Pressure difference between port_a2 and port_b2 [Pa]

Assumptions

Boolean allowFlowReversal_1 system.allowFlowReversal = true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)

Boolean allowFlowReversal_2 system.allowFlowReversal = true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)

Advanced

MassFlowRate m_flow_1_small 1E-4*m0_flow_1 Small mass flow rate for regularization of zero flow [kg/s]

MassFlowRate m_flow_2_small 1E-4*m0_flow_2 Small mass flow rate for regularization of zero flow [kg/s]

Diagnostics

Boolean show_V_flow true = true, if volume flow rate at inflowing port is computed

Initialization

AbsolutePressure p_a1_start system.p_start Guess value for inlet pressure [Pa]

AbsolutePressure p_b1_start p_a1_start Guess value for outlet pressure [Pa]

AbsolutePressure p_a2_start system.p_start Guess value for inlet pressure [Pa]

AbsolutePressure p_b2_start p_a2_start Guess value for outlet pressure [Pa]

Type	Name	Default	Description
replaceable package Medium_1	Modelica.Media.Interfaces.Pa...	Medium 1 in the component
replaceable package Medium_2	Modelica.Media.Interfaces.Pa...	Medium 2 in the component
MixingVolumeDryAir	vol_2	redeclare Buildings.Fluids.M...	Volume for fluid 2
HeatCapacity	C	tau_m*UA0	Heat capacity of metal (= cp*m) [J/K]
Nominal condition
MassFlowRate	m0_flow_1		Nominal mass flow rate [kg/s]
MassFlowRate	m0_flow_2	m0_flow_1	Nominal mass flow rate [kg/s]
Time	tau_1	60	Time constant at nominal flow [s]
Time	tau_2	60	Time constant at nominal flow [s]
ThermalConductance	UA0		Thermal conductance at nominal flow [W/K]
Time	tau_m	2	Time constant of metal [s]
Initialization
MassFlowRate	m_flow_1.start	0	Mass flow rate from port_a1 to port_b1 (m_flow_1 > 0 is design flow direction) [kg/s]
Pressure	dp_1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m_flow_2.start	0	Mass flow rate from port_a2 to port_b2 (m_flow_2 > 0 is design flow direction) [kg/s]
Pressure	dp_2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
Assumptions
Boolean	allowFlowReversal_1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal_2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_1_small	1E-4*m0_flow_1	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m_flow_2_small	1E-4*m0_flow_2	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed
Initialization
AbsolutePressure	p_a1_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b1_start	p_a1_start	Guess value for outlet pressure [Pa]
AbsolutePressure	p_a2_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b2_start	p_a2_start	Guess value for outlet pressure [Pa]

Connectors

Type Name Description

FluidPort_a port_a1 Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)

FluidPort_b port_b1 Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)

FluidPort_a port_a2 Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)

FluidPort_b port_b2 Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)

input RealInput Gc_1 Signal representing the convective thermal conductance of fluid 1 in [W/K]

input RealInput Gc_2 Signal representing the convective thermal conductance of fluid 2 in [W/K]

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)
input RealInput	Gc_1	Signal representing the convective thermal conductance of fluid 1 in [W/K]
input RealInput	Gc_2	Signal representing the convective thermal conductance of fluid 2 in [W/K]

Modelica definition

model DryHexHAInput 
  "Simple heat exchanger with convective heat transfer as input"
  extends Fluids.Interfaces.PartialDynamicFourPortTransformer(final C=tau_m*UA0);
  extends Buildings.BaseClasses.BaseIcon;


   parameter Modelica.SIunits.ThermalConductance UA0(min=0) 
    "Thermal conductance at nominal flow";
  parameter Modelica.SIunits.Time tau_m(min=0) = 2 "Time constant of metal";
  Modelica.Blocks.Interfaces.RealInput Gc_1 
    "Signal representing the convective thermal conductance of fluid 1 in [W/K]";
  Modelica.Blocks.Interfaces.RealInput Gc_2 
    "Signal representing the convective thermal conductance of fluid 2 in [W/K]";
equation 
  connect(Gc_1, con1.Gc);
  connect(Gc_2, con2.Gc);
end DryHexHAInput;

Buildings.Fluids.HeatExchangers.HeaterCoolerIdeal

Ideal electric heater or cooler, no losses, no dynamics

Buildings.Fluids.HeatExchangers.HeaterCoolerIdeal

Information

Model for an ideal heater or cooler.

This model adds heat in the amount of Q_flow = u Q0_flow to the medium. The input signal u and the nominal heat flow rate Q0_flow can be positive or negative.

Note that if the mass flow rate tends to zero, the temperature difference over this component tends to infinity for non-zero Q_flow, so add proper control when using this component.

Extends from Fluids.Interfaces.PartialStaticTwoPortHeatMassTransfer (Partial element transporting fluid between two ports without storing mass or energy), Buildings.BaseClasses.BaseIcon (Base icon).

Parameters

Type Name Default Description

replaceable package Medium Modelica.Media.Interfaces.Pa... Medium in the component

HeatFlowRate Q0_flow Heat flow rate at u=1, positive for heating [W]

Nominal condition

MassFlowRate m0_flow Nominal mass flow rate [kg/s]

Initialization

MassFlowRate m_flow.start 0 Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]

Pressure dp.start 0 Pressure difference between port_a and port_b [Pa]

Assumptions

Boolean allowFlowReversal system.allowFlowReversal = true to allow flow reversal, false restricts to design direction (port_a -> port_b)

Advanced

MassFlowRate m_flow_small 1E-4*m0_flow Small mass flow rate for regularization of zero flow [kg/s]

Diagnostics

Boolean show_V_flow true = true, if volume flow rate at inflowing port is computed

Initialization

AbsolutePressure p_a_start system.p_start Guess value for inlet pressure [Pa]

AbsolutePressure p_b_start p_a_start Guess value for outlet pressure [Pa]

Type	Name	Default	Description
replaceable package Medium	Modelica.Media.Interfaces.Pa...	Medium in the component
HeatFlowRate	Q0_flow		Heat flow rate at u=1, positive for heating [W]
Nominal condition
MassFlowRate	m0_flow		Nominal mass flow rate [kg/s]
Initialization
MassFlowRate	m_flow.start	0	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressure	dp.start	0	Pressure difference between port_a and port_b [Pa]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*m0_flow	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed
Initialization
AbsolutePressure	p_a_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b_start	p_a_start	Guess value for outlet pressure [Pa]

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)

input RealInput u

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)
input RealInput	u

Modelica definition

model HeaterCoolerIdeal 
  "Ideal electric heater or cooler, no losses, no dynamics"
  extends Fluids.Interfaces.PartialStaticTwoPortHeatMassTransfer;
  extends Buildings.BaseClasses.BaseIcon;

  parameter Modelica.SIunits.HeatFlowRate Q0_flow 
    "Heat flow rate at u=1, positive for heating";
  Modelica.Blocks.Interfaces.RealInput u;
equation 
  dp = 0;
  Q_flow = Q0_flow * u;
  mXi_flow = zeros(Medium.nXi); // no mass added or removed (sensible heat only)
end HeaterCoolerIdeal;

Buildings.Fluids.HeatExchangers.WetCoilDiscretized

Coil with condensation

Buildings.Fluids.HeatExchangers.WetCoilDiscretized

Information

Model of a discretized coil with humidity condensation. This model is identical to Buildings.Fluids.HeatExchangers.DryCoilDiscretized but in addition, the mass transfer from fluid 2 to the metal is computed. The mass transfer is computed based using similarity laws between heat and mass transfer, as implemented by the model Buildings.Media.PerfectGases.MoistAir and Modelica.Media.Air.MoistAir.

Extends from DryCoilDiscretized (Heat exchanger with discretization along the flow path).

Parameters

Type	Name	Default	Description
replaceable package Medium_1	Modelica.Media.Interfaces.Pa...	Medium 1 in the component
replaceable package Medium_2	Modelica.Media.Interfaces.Pa...	Medium 2 in the component
Nominal condition
MassFlowRate	m0_flow_1		Nominal mass flow rate [kg/s]
MassFlowRate	m0_flow_2	m0_flow_1	Nominal mass flow rate [kg/s]
TemperatureDifference	dT0	10	Temperature difference [K]
HeatFlowRate	Q0_flow	1000	Heat transfer at dT0 [W]
ThermalConductance	UA0	Q0_flow/dT0	Thermal conductance at nominal flow, used to compute heat capacity [W/K]
Pressure	dp0_1		Pressure drop for all pipes [Pa]
Pressure	dp0_2		Pressure drop inside duct [Pa]
Time	tau_1	20	Time constant at nominal flow for medium 1 [s]
Time	tau_2	1	Time constant at nominal flow for medium 2 [s]
Time	tau_m	20	Time constant of metal at nominal UA value [s]
Initialization
MassFlowRate	m_flow_1.start	0	Mass flow rate from port_a1 to port_b1 (m_flow_1 > 0 is design flow direction) [kg/s]
Pressure	dp_1.start	0	Pressure difference between port_a1 and port_b1 [Pa]
MassFlowRate	m_flow_2.start	0	Mass flow rate from port_a2 to port_b2 (m_flow_2 > 0 is design flow direction) [kg/s]
Pressure	dp_2.start	0	Pressure difference between port_a2 and port_b2 [Pa]
MassFlowRate	mStart_flow_a1	m0_flow_1	Guess value for mass flow rate at port_a1 [kg/s]
MassFlowRate	mStart_flow_a2	m0_flow_2	Guess value for mass flow rate at port_a2 [kg/s]
Geometry
Integer	nReg	2	Number of registers
Integer	nPipPar	3	Number of parallel pipes in each register
Integer	nPipSeg	4	Number of pipe segments per register used for discretization
Length	dh_1	0.025	Hydraulic diameter for a single pipe [m]
Length	dh_2	1	Hydraulic diameter for duct [m]
Assumptions
Boolean	allowFlowReversal_1	system.allowFlowReversal	= true to allow flow reversal in medium 1, false restricts to design direction (port_a -> port_b)
Boolean	allowFlowReversal_2	system.allowFlowReversal	= true to allow flow reversal in medium 2, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics_1	Modelica_Fluid.Types.Dynamic...	Default formulation of energy balances for volume 1
Dynamics	energyDynamics_2	Modelica_Fluid.Types.Dynamic...	Default formulation of energy balances for volume 2
Dynamics	ductConnectionDynamics	Modelica_Fluid.Types.Dynamic...	Default formulation of energy balances for duct connection
Length	dl	0.3	Length of mixing volume for duct connection [m]
Advanced
MassFlowRate	m_flow_1_small	1E-4*m0_flow_1	Small mass flow rate for regularization of zero flow [kg/s]
MassFlowRate	m_flow_2_small	1E-4*m0_flow_2	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	from_dp_1	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	from_dp_2	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	deltaM_1	0.3	Fraction of nominal mass flow rate where transition to laminar occurs
Real	deltaM_2	0.3	Fraction of nominal mass flow rate where transition to laminar occurs
Boolean	linearized_1	false	= true, use linear relation between m_flow and dp for any flow rate
Boolean	linearized_2	false	= true, use linear relation between m_flow and dp for any flow rate
Boolean	use_dh_1	false	Set to true to specify hydraulic diameter for pipe pressure drop
Boolean	use_dh_2	false	Set to true to specify hydraulic diameter for duct pressure drop)
Real	ReC_1	4000	Reynolds number where transition to laminar starts inside pipes
Real	ReC_2	4000	Reynolds number where transition to laminar starts inside ducts
Diagnostics
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed
Initialization
AbsolutePressure	p_a1_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b1_start	p_a1_start	Guess value for outlet pressure [Pa]
AbsolutePressure	p_a2_start	system.p_start	Guess value for inlet pressure [Pa]
AbsolutePressure	p_b2_start	p_a2_start	Guess value for outlet pressure [Pa]
Heat transfer
Boolean	waterSideFlowDependent	false	Set to false to make water-side hA independent of mass flow rate
Boolean	airSideFlowDependent	false	Set to false to make air-side hA independent of mass flow rate
Boolean	waterSideTemperatureDependent	false	Set to false to make water-side hA independent of temperature

Connectors

Type	Name	Description
FluidPort_a	port_a1	Fluid connector a1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_b	port_b1	Fluid connector b1 (positive design flow direction is from port_a1 to port_b1)
FluidPort_a	port_a2	Fluid connector a2 (positive design flow direction is from port_a2 to port_b2)
FluidPort_b	port_b2	Fluid connector b2 (positive design flow direction is from port_a2 to port_b2)

Modelica definition

model WetCoilDiscretized "Coil with condensation"
  extends DryCoilDiscretized(final allowCondensation=true,
  each hexReg(ele(redeclare each Buildings.Fluids.MixingVolumes.MixingVolumeMoistAir
          vol_2(
          final use_HeatTransfer = true,
          medium(T(stateSelect=StateSelect.never))))));
end WetCoilDiscretized;

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