Air Conditioning Library - Release Information

Version 1.13...

  • ...

Library structure changes

  • The heat transfer correlation packages have been reorganized to make their intended usage clearer. They are now collected in the subpackages HTOnePhaseMedium for liquid fluids, HTTwoPhaseMedium for refrigerants and HTFin for air.
  • The pdf-version of the User's manual has been discontinued and all material is now found incorporated into the library info classes and model info layers.
  • Correlations that contained errors were replaced by corrected versions and moved to the folder ThermoFluidPro.HeatTransfer.Deprecated. Existing models are automatically converted to these models, in order to keep their possibly calibrated behavior. The deprecated models no longer appear in the drop-down list of the corresponding parameter dialog, but can still be used when entered in the text layer. To do this, choose first another heat transfer correlation from the drop down list, then go to the ThermoFluidPro.HeatTransfer.Deprecated package and double-click on the desired correlation, right-click, Copy path and paste in the correct location in the text layer of the heat exchanger ot system model.
  • The drop down lists for refrigerant side pressure drop correlations in liquid-coolant plate heat exchangers and the internal heat exchanger have been cleaned from duplicates that were intended for usage in pipe models. If those are still used in customer models, a warning is usually triggered, complaining about a non-matching sybtype.

New classes

  • HTOnePhaseMedium.HTPlateChevronChisholm, a new heat transfer correlation for one-phase fluids (coolant) in Chevron-type plate heat exchangers
  • HTOnePhaseMedium.KcUserDefinedSinglePhase, user defined correlation for liquid fluids
  • HTOnePhaseMedium.KcSinglePhaseCalibration, calibration correlation for liquid fluids, which allows to compute global Nusselt numbers with given heat exchanger power and inverted models
  • PLossHexChannel.PlossChevronMartin, a one-phase pressure drop correlation (coolant side) for Chevron-type plate heat exchangers.
  • Overview tables for available heat transfer and pressure drop correlations, which list the type of the correlation (e.g. semi-empirical, nominal operating point), the type of model (e.g. heat exchanger or pipe), the type of fluid (e.g. refrigerant, incompressible liquid, air) and the area of validity (e.g. one-or two-phase region, Reynolds numbers etc).

Conversion of user libraries

A conversion script is required to accommodate for the path name changes of the heat transfer correlations. In addition all usages of the bug fixed correlations are converted automatically to a deprecated copy of the previous bug containing version in order to retain the behavior of calibrated models. Important: The corresponding changes are found in the ThermoFluidPro Library. In oder to trigger the execution of the conversion script automatically, the user library needs to have the uses annotation also for ThermoFluidPro (see bottom of info layer, under "Uses:" both, "AirConditioning" and "ThermoFluidPro" have to appear). This should normally happen automatically, when the model is created with both libraries open.

Requirements

The AirConditioning Library 1.12 is based on the ThermoFluidPro Library 1.12, Modelica Standard Library 3.2.2. and UserInteraction 0.64.

It has been tested with:

  • Dymola 2017
  • Dymola 2016 FD01

Version 1.12 contains the changes described below.

Improvements

  • An error was corrected in the Chen correlation for refrigerant evaporation in heat exchangers. Heat exchanger results may be affected especially if heat transfer is limited by the refrigerant side. User models built with one of the previous versions are converted to the original correlation to retain possibly calibrated behavior.
  • An error was corrected in the Kandlikar correlation for refrigerant (R744) evaporation in heat exchangers. Heat exchanger results may be effected especially if heat transfer is limited by the refrigerant side. User models built with one of the previous versions are converted to the original correlation to retain possibly calibrated behavior.
  • A discontinuity in the separator model, occuring for _smooth media (R134a_smooth and R1234yf_smooth) when the receiver level reaches the top, has been removed. It had previously been the cause for stalling simulations at the liquid phase boundary. The receiver outlet quality smoothing has been applied in a way to retain the original behavior. Smaller deviations may still be observed in transient behavior of sensitive systems.
  • Splits and joins have been completed with an additional choice of flow resistance parameterization through nominal operating points and summary records.
  • Air mass flow rate in heat exchangers summary corresponds to inlet variable instead of outlet, which only is a difference in case of moisture condensation.

Library structure changes

  • The heat transfer correlation packages have been reorganized to make their intended usage clearer. They are now collected in the subpackages HTOnePhaseMedium for liquid fluids, HTTwoPhaseMedium for refrigerants and HTFin for air.
  • The pdf-version of the User's manual has been discontinued and all material is now found incorporated into the library info classes and model info layers.
  • Correlations that contained errors were replaced by corrected versions and moved to the folder ThermoFluidPro.HeatTransfer.Deprecated. Existing models are automatically converted to these models, in order to keep their possibly calibrated behavior. The deprecated models no longer appear in the drop-down list of the corresponding parameter dialog, but can still be used when entered in the text layer. To do this, choose first another heat transfer correlation from the drop down list, then go to the ThermoFluidPro.HeatTransfer.Deprecated package and double-click on the desired correlation, right-click, Copy path and paste in the correct location in the text layer of the heat exchanger ot system model.
  • The drop down lists for refrigerant side pressure drop correlations in liquid-coolant plate heat exchangers and the internal heat exchanger have been cleaned from duplicates that were intended for usage in pipe models. If those are still used in customer models, a warning is usually triggered, complaining about a non-matching sybtype.

New classes

  • HTOnePhaseMedium.HTPlateChevronChisholm, a new heat transfer correlation for one-phase fluids (coolant) in Chevron-type plate heat exchangers
  • HTOnePhaseMedium.KcUserDefinedSinglePhase, user defined correlation for liquid fluids
  • HTOnePhaseMedium.KcSinglePhaseCalibration, calibration correlation for liquid fluids, which allows to compute global Nusselt numbers with given heat exchanger power and inverted models
  • PLossHexChannel.PlossChevronMartin, a one-phase pressure drop correlation (coolant side) for Chevron-type plate heat exchangers.
  • Overview tables for available heat transfer and pressure drop correlations, which list the type of the correlation (e.g. semi-empirical, nominal operating point), the type of model (e.g. heat exchanger or pipe), the type of fluid (e.g. refrigerant, incompressible liquid, air) and the area of validity (e.g. one-or two-phase region, Reynolds numbers etc).

Conversion of user libraries

A conversion script is required to accommodate for the path name changes of the heat transfer correlations. In addition all usages of the bug fixed correlations are converted automatically to a deprecated copy of the previous bug containing version in order to retain the behavior of calibrated models. Important: The corresponding changes are found in the ThermoFluidPro Library. In oder to trigger the execution of the conversion script automatically, the user library needs to have the uses annotation also for ThermoFluidPro (see bottom of info layer, under "Uses:" both, "AirConditioning" and "ThermoFluidPro" have to appear). This should normally happen automatically, when the model is created with both libraries open.

Requirements

The AirConditioning Library 1.12 is based on the ThermoFluidPro Library 1.12, Modelica Standard Library 3.2.2. and UserInteraction 0.64.

It has been tested with:

  • Dymola 2017
  • Dymola 2016 FD01

Version 1.11 contains the changes described below.

Improvements

  • Improved library documentation.
  • Improved component icons for greater system readabilty.
  • Icons in the package browser.
  • User's Guide available in-built in the documentation layer of the library. Please note that the .pdf will be discontinued from the next version onwards.

Library structure changes

New classes

  • Numerous additions to AirConditioning.Information.UsersGuide
  • AirConditioning.Examples.Information
  • AirConditioning.Templates.Information
  • AirConditioning.AirHandling.Information
  • AirConditioning.Compressors.Information
  • AirConditioning.ControllersAndSensors.Information
  • AirConditioning.Cycles.Information
  • AirConditioning.HeatExchangers.Information
  • AirConditioning.Heating.Information
  • AirConditioning.Receivers.Information
  • AirConditioning.Reservoirs.Information
  • AirConditioning.Valves.Information
  • AirConditioning.SubComponents.Information
  • AirConditioning.Visualizers.Information
  • AirConditioning.PipesAndVolumes.Information

Conversion of user libraries

No conversion script is required.

Requirements

The AirConditioning Library 1.11 is based on the ThermoFluidPro Library 1.11 and Modelica Standard Library 3.2.1.  

It has been tested with:

  • Dymola 2016 FD01
  • Dymola 2016

Version 1.10 contains the changes described below.

New features

  • Introduction of a new system component System_ACL. Including this system component at the top level of a model makes it possible to set system settings, which will be propagated to component models using the inner/outer principle. A System_ACL component with its default values will not affect the behavior of the model. System_ACL will automatically be added to the translated model if it is not done by the user.
  • The refrigerant connector variables are changed: the enthalpy flow rate variable is replaced by a specific enthalpy stream variable. This has been done to avoid discontinuities when accessing upstream enthalpy at zero-flow. The stream variable permits access to specific enthalpies in neighboring volumes independent of flow direction; previously only the upstream value could be accessed from inside a component.

Improvements

  • New shut-off variable u in refrigerant pressure loss models. By default its value is 1 and will not affect any result. By setting this variable equal to e.g. an output signal from a ramp it is possible to shut-off the flow.
  • New boolean parameter generateEventAtPhaseTransition. Its value can be set in System_ACL and is by default false. Setting the value to true will trigger an event when a phase transition occurs in a control volume.
  • New boolean parameter generateEventAtCritical. Its value can be set in System_ACL and is by default false. Setting the value to true will trigger an event when a control volume enters or exits the supercritical zone.
  • New boolean parameter positiveFlow. Its value can be set in System_ACL and is by default true. If this parameter is set to true to the model assumes a positive flow direction.
  • Differentiating scheme options for the discretized refrigerant pipes, which can be changed in System_ACL. It is possible to use a hybrid scheme which includes diffusion effects at low flow rates. The diffusion factor can be set in different ways. One option permits the variation of the diffusion factor in function of the mass flow.
  • StateSelection option for using pressure difference instead of pressure as state variable, accessible in System_ACL.
  • Introduction of new pressure loss correlations with the possibility to switch to a simplified model during simulation, accessible in System_ACL.


Fixed issues

  • The air medium is correctly propagated in AirConditioning.HeatExchangers.HXBase and by extension also in some heat exchangers models.This did previously not cause any problem except if the heat exchanger was operated outside the operation range of the default air medium, using an air medium which was valid in that range.

Library structure changes

New classes

  • AirConditioning.System_ACL

Conversion of user libraries

No conversion script is required.

Any customized components may need to be adjusted due to the newly added stream variable in the two-phase flow connector.

Requirements

The AirConditioning Library 1.10 is based on the ThermoFluidPro Library 1.10 and Modelica Standard Library 3.2.1.  

It has been tested with:

  • Dymola 2015 FD01
  • Dymola 2016

A conversion script is necessary (opens automatically) for used evaporation heat transfer correlations, see note below. This release is based on MSL 3.2.1.

    1. Modifications:
      • Improved robustness for the refrigerant CO2 (R744) at the critical point.
      • A refrigerant flow source (Reservoirs.FlowSourceCharge) is introduced as an optional component in the liquid receiver model. This makes it more convenient to reach steady-state operating points in charge experiments, since the additional refrigerant is usually stored there and does not have to travel through the system.
      • Chens correlation for evaporative heat transfer is added. It is not dependent on the heat flux and therefore avoids this iterative loop in the non-linear equation systems. On the other hand it is known to be a little less accurate than other correlations
      • The parameter p_ambient, which is used in all air models is propagated to the top level of all heat exchangers. For numerical and efficiency reason this property is constant and not the time-varying downstream pressure. Making this parameter available at the component tops level makes it easier to simulate pressure levels different to the atmospheric pressure. The default behavior of the models is not influenced by this change.
      • A bug was fixed in the Dittus-Boelter function which is used in heat transfer correlations for evaporation. Deviations are expected, in case the air or incompressible liquid side is not limiting the heat transfer. For backward compatibility reasons, the conversion script converts the used correlation to the original bug-containing one with a new name. Calibrated existing components shall therefore not cause result deviations compared to previous library versions unless the default heat transfer correlation in the base class from the library has not been modified.
      • Wrong connector enthalpies in air components HeatExchangers.HXAirHandling.AirSplit1_2 and HeatExchangers.HXAirHandling.AirSplit1_2_n_segMtl were corrected.
      • Singularity for super-critical region in orifice tube model is removed.
      • Stability state as advanced feature included in refrigerant channel models. The variable twoPhaseFraction, which describes the fraction of a volume covered by two-phase fluid,is turned into an additional state with an artificial delay. This can in some cases avoid oscillations, which may occur for the hard-coupled dependency of the heat transfer coefficient on the amount of evaporated or condensed refrigerant in the volume. Note that activating this advanced feature may change the overall dynamic behavior of the component. The default behavior of the affected components is not influenced.
      • Improved Modelica compliance

09-05-2014

Available for: Dymola 2015

Dependencies: Modelica Standard Library Version: 

Conversion: 

New components:

  •   Air split and junctions

Improvements:

  • Steady-state initialization of evaporators with homotopy method
  • Correct propagation of initial wall temperature in internal heat exchangers

Bug fixes:

  • Deviation in saturation properties of refrigerants R152a and R32 corrected
  • Temperature display unit in superheat sensor changed from degC to K

 

Available for: Dymola 2014 FD01

DependenciesModelica Standard Library Version: 3.2.1

Conversion: None from 1.8.4 and 1.8.5

  • This release is based on MSL 3.2.1. Due to some structural modifications in the Modelica.Media base classes, small changes in ThermoFluidPro were necessary. Therefore, this version of AirConditioning is only compatible with MSL 3.2.1. Regression tests comfirmed unchanged simulation results for the models in this library, in some rare cases convergence of steady-state initialization was influenced. AirConditioning 1.8.5 is identical to version 1.8.6, but still based on MSL 3.2 and is recommended to be used instead in case MSL 3.2 is the chosen Modelica base library.

Available for: Dymola 2014 FD01

DependenciesModelica Standard Library Version: 3.2

Conversion: None from 1.8.4

  • A new information section is included directly in the library, with guidelines on component testbench and cycle initialization.
  • Handling of refrigerant properties at the receiver outlet is improved for low or zero-flow simulations.
  • In- and outlet pressures, enthalpies and pressures in heat exchanger summary records properly take into account headers, in case those are activated. Previously, only the active heat exchanger part was considered for temperature and enthalpy variables. Enthalpy deviations from previous results are only expected, if heat transfer between headers is possible, temperature may be slighthly different in the two-phase region, due to the additional pressure drop in the headers. This concerns only summary variables, other model variables are unaffected.
  • The variability of correction factors for heat transfer and pressure drop in heat exchangers (CF_ ...) has been increased. They are now declared as input variables, which may change over time. As a feature request by many users, this increases the flexibility for user defined modifications. The default behavior of existing models is not expected to change. Manual steps may be required for the conversion of models for pressure drop and heat transfer correlations, which were copied and modified from previous versions of the library. Please, contact support, if you experience problems.
  • Display units in the four-value display visualizer are corrected to be consistent with the actual value.