modelParallelCircuitsSlab

Model of multiple parallel circuits of a radiant slab

Extends from Buildings.Fluid.Interfaces.PartialTwoPort, Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Slab, Buildings.Fluid.Interfaces.LumpedVolumeDeclarations, Buildings.Fluid.Interfaces.TwoPortFlowResistanceParameters.

Information

This is a model of a radiant slab with pipes or a capillary heat exchanger embedded in the construction. The model is a composition of multiple models of Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab that are arranged in a parallel.

The parameter nCir declares the number of parallel flow circuits. Each circuit will have the same mass flow rate, and it is exposed to the same port variables for the heat port at the two surfaces, and for the flow inlet and outlet.

A typical model application is as follows: Suppose a large room has a radiant slab with two parallel circuits with the same pipe spacing and pipe length. Then, rather than using two instances of Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab, this system can be modeled using one instance of this model in order to reduce computing effort. See Buildings.Fluid.HeatExchangers.RadiantSlabs.Examples.SingleCircuitMultipleCircuitEpsilonNTU for an example that shows that the models give identical results.

Since this model is a parallel arrangment of nCir models of Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab, we refer to Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlab for the model documentation.

See the user's guide for more information.

Implementation

To allow a better comment for the nominal mass flow rate, i.e., to specify that its value is for all circuits combined, this model does not inherit Buildings.Fluid.Interfaces.PartialTwoPortInterface.

Parameters

TypeNameDefaultDescription
BooleanhomotopyInitializationtrue= true, use homotopy method
IntegernCir1Number of parallel circuits
IntegernSegif heatTransfer == Types.HeatTransfer.EpsilonNTU then 1 else 5Number of volume segments in each circuit (along flow path)
Modelica.Units.SI.LengthlengthA/disPip/nCirLength of the pipe of a single circuit
Modelica.Units.SI.Velocityv_nominal4*m_flow_nominal/pipe.dIn^2/Modelica.Constants.pi/rho_default/nCirVelocity at m_flow_nominal
Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.HeatTransferheatTransferTypes.HeatTransfer.EpsilonNTUModel for heat transfer between fluid and slab
Construction
Modelica.Units.SI.AreaASurface area of radiant slab (all circuits combined)
Nominal condition
Modelica.Units.SI.MassFlowRatem_flow_nominalNominal mass flow rate of all circuits combined
Advanced
Modelica.Units.SI.MassFlowRatem_flow_small1E-4*abs(m_flow_nominal)Small mass flow rate of all circuits combined for regularization of zero flow
Advanced › Diagnostics
Booleanshow_Tfalse= true, if actual temperature at port is computed

Components

TypeNameDefaultDescription
Modelica.Units.SI.MassFlowRatem_flowport_a.m_flowMass flow rate from port_a to port_b (m_flow > 0 is design flow direction) for all circuits combined
Modelica.Units.SI.PressureDifferencedpport_a.p - port_b.pPressure difference between port_a and port_b
Medium.ThermodynamicStatesta_aif homotopyInitialization then Medium.setState_phX(port_a.p, homotopy(actual = noEvent(actualStream(port_a.h_outflow)), simplified = inStream(port_a.h_outflow)), homotopy(actual = noEvent(actualStream(port_a.Xi_outflow)), simplified = inStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow)))Medium properties in port_a
Medium.ThermodynamicStatesta_bif homotopyInitialization then Medium.setState_phX(port_b.p, homotopy(actual = noEvent(actualStream(port_b.h_outflow)), simplified = port_b.h_outflow), homotopy(actual = noEvent(actualStream(port_b.Xi_outflow)), simplified = port_b.Xi_outflow)) else Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow)))Medium properties in port_b
Buildings.Fluid.HeatExchangers.RadiantSlabs.SingleCircuitSlabslaSingle parallel circuit of the radiant slab

Revisions

  • April 14, 2020, by Michael Wetter:
    Changed homotopyInitialization to a constant.
    This is for IBPSA, #1341.
  • January 22, 2016, by Michael Wetter:
    Corrected type declaration of pressure difference. This is for #404.
  • June 9, 2015 by Michael Wetter:
    Changed base class from Modelica.Fluid.Interfaces.PartialTwoPort to Buildings.Fluid.Interfaces.PartialTwoPort.
  • October 10, 2013 by Michael Wetter:
    Added noEvent to the computation of the states at the port. This is correct, because the states are only used for reporting, but not to compute any other variable. Use of the states to compute other variables would violate the Modelica language, as conditionally removed variables must not be used in any equation.
  • October 8, 2013, by Michael Wetter:
    Removed parameter show_V_flow.
  • September 14, 2013, by Michael Wetter:
    Corrected assignment of start value for pressure at port_a and port_b, which used Medium.p_default instead of the parameter p_start.
  • June 27, 2012, by Michael Wetter:
    First implementation.