.Buildings.Fluid.DXSystems.Heating.AirSource.Validation.SingleSpeed_TimedReverseCycleDefrost

Information

This model validates the model Buildings.Fluid.DXSystems.Heating.AirSource.SingleSpeed with the defrost time fraction calculation datDef.defTri set to DefrostTimeMethods.timed and the defrost operation type datDef.defOpe set to DefrostOperation.reverseCycle.

The difference in results of T_Out and X_Out at the beginning and end of the simulation is because the mass flow rate is zero. For zero mass flow rate, EnergyPlus assumes steady state condition, whereas the Modelica model is a dynamic model and hence the properties at the outlet are equal to the state variables of the model.

The EnergyPlus results were generated using the example file DXCoilSystemAuto.idf from EnergyPlus 22.2. The results were then used to set-up the boundary conditions for the model as well as the input signals. To compare the results, the Modelica outputs are averaged over 3600 seconds, and the EnergyPlus outputs are used with a zero order delay to avoid the time shift in results.

Note that EnergyPlus mass fractions (X) are in mass of water vapor per mass of dry air, whereas Modelica uses the total mass as a reference. Also, the temperatures in Modelica are in Kelvin whereas they are in Celsius in EnergyPlus. Hence, the EnergyPlus values are corrected by using the appropriate conversion blocks.

The plots compare the outlet temperature and humidity ratio between Modelica and EnergyPlus. They also compare the power consumption by the coil compressor as well as the heat transfer from the airloop.

Revisions

• April 2, 2023, by Karthik Devaprasad and Xing Lu:
  First implementation.