modelZhuTimeBasedDefrost

Time based defrost based on Zhus frosting map

Extends from BaseClasses.PartialDefrost (Partial model for defrost control).

Information

This defrost control uses a time-based approach from Zhu et al. coupled with their three frosting zones. The three zones depend outdoor air temperature and humidity. Depending on the zone, a different time-interval for defrost is applied, taken from Table 4 in Zhu et al: 30, 60 and 165 min for severe, moderate and mild zones, respectively. Contrary to Zhu et al, moderate and mild frosting zones are not further seperated. The 60 and 135 min defrost time are the average value for those zones reported in Zhu et al.

References

J.H. Zhu, Y.Y. Sun, W. Wang, S.M. Deng, Y.J. Ge, and L.T. Li. Developing a new frosting map to guide defrosting control for air-source heat pump units. Applied Thermal Engineering, November 2015 doi:10.1016/j.applthermaleng.2015.06.076.

Parameters

TypeNameDefaultDescription
RealminIceFac0.5Minimal allowed icing Factor to trigger the defrost

Connectors

TypeNameDefaultDescription
AixLib.Fluid.HeatPumps.ModularReversible.BaseClasses.RefrigerantMachineControlBussigBus (from PartialDefrost)Bus with the most relevant information for hp frosting calculation
Modelica.Blocks.Interfaces.BooleanOutputhea (from PartialDefrost)Heating mode for heat pump

Components

TypeNameDefaultDescription
Modelica.Blocks.Logical.HysteresishysFor the iceFac control. Output signal is used internally
Modelica.Blocks.Logical.Timertimer
Modelica.Blocks.Logical.Greatergreater
Modelica.Blocks.Sources.ConstantconstNoDefInfinite defrost time
Modelica.Blocks.Logical.Notnot1
Modelica.Blocks.Logical.OrorDefEither hys or critical min time
Modelica.Blocks.Logical.Andand1
Modelica.Blocks.Logical.LessEqualThresholdlesEquThr
Modelica.Blocks.Logical.AndandDefrostEither hys or crit min time
Modelica.Blocks.Logical.NotnotHeaIf defrost, we set hea=false
Modelica.Blocks.Logical.Switchswi
Modelica.Blocks.Sources.RealExpressioncritDefTim_internalMode from internal calcuations
AixLib.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.Frosting.BaseClasses.ZhuFrostingZonefroZonCurrent zone
Modelica.Blocks.Logical.AndandIsOnIn frosting zone and on leads to possible frosting
Modelica.Blocks.Math.IntegerToRealandIsOn1In frosting zone and on leads to possible frosting
Modelica.Blocks.Logical.GreaterThresholdposFroIf in any frosting zone

Revisions

  • December 22, 2025 by Fabian Roemer:
    First implementation (see issue AixLib #1623)