Air Conditioning Library - Release Information

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