modelLiangAndZhuCalibrated

Measured velocities based on Liang et al. 2020 calibrated on own heat pump

Extends from AixLib.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.Frosting.BaseClasses.PartialVelocityBased (Partial model for velocity based frost modelling).

Information

This model calibrates the growth velocities from Liang et al., who base their work on the zones from Zhu et al., onto dynamic frost densities and a custom build heat pump at the Institute for Energy Efficient Buildings and Indoor Climate.

The calibration was performed and used for Römer et al. In addition to Liang et al., a time-delay after the last defrost is used before the frost starts to grow again. This was added based observed data from dynamic tests and is grounded in the fact that fins are warm after defrost, and, thus, don't directly accumulate frost.

For more information, see the base-model: AixLib.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.Frosting.BaseClasses.PartialVelocityBased .

References

Römer, Fabian and Fuchs, Nico and Fuchs, Nico and Müller, Dirk, Practical, Near-Optimal Design Rule Extraction for Heat Pumps in Single-Family Buildings (September 03, 2025). Available at SSRN: https://ssrn.com/abstract=5633891

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.

Liang, S., Wang, W., Sun, Y., Li, Z., Zhao, J., Lin, Y., and Deng, S. (2020). A novel characteristic index for frosting suppression based on the configuration and operation of air source heat pumps. International Journal of Refrigeration, 109, 161-171. https://doi.org/10.1016/j.ijrefrig.2019.10.009.

Parameters

TypeNameDefaultDescription
Modelica.Units.SI.AreaA (from PartialVelocityBased)15Area of heat exchanger, all fins from both sides
Booleanuse_reset (from PartialVelocityBased)false= true, if reset port enabled
RealtimeMiltimeSev*facSevMil
RealdefrostEfficiency0.65Defrost efficiency
RealfacSevMil1.358403
RealtimeSev1083.524850
RealcorCoeffSev0.231588Correction coefficient for severe zone
RealcorCoeffMod0.218708Correction coefficient for moderate zone
RealcorCoeffMil0.218708Correction coefficient for mild zone
Advanced › Medium properties
Modelica.Units.SI.SpecificHeatCapacitycpEva (from PartialIcingFactor)Evaporator medium specific heat capacity
Density
Booleanuse_varDen (from PartialVelocityBased)false=true to use variable density based on PT1 Element, e.g. Korn et al.
Modelica.Units.SI.Densityden_constant (from PartialVelocityBased)659Constant density of frost, based on Korn at -5 frost temperature
Realk (from PartialVelocityBased)3.77Gain
Modelica.Units.SI.TimeT (from PartialVelocityBased)8000Time Constant
Realden_min (from PartialVelocityBased)50Minimal density
Ice mass
BooleanestimateMaximalIceMass (from PartialVelocityBased)true=false to specify maximal ice mass directly
Modelica.Units.SI.MassmIce_max (from PartialVelocityBased)den_constant*A*d/2Maximal possible mass of ice on HE surface. This value is limited by the volume between the fin tube
Modelica.Units.SI.Distanced (from PartialVelocityBased)3e-3Distance between two fins. Used to calculate the maximal mass of ice on the HE
Melting
RealnatConvCoeff (from PartialVelocityBased)1e-7Parameter to be calibrated for natural defrost
Modelica.Units.SI.SpecificEnthalpyhWatFus (from PartialVelocityBased)333.5e3Fusion enthalpy of water

Connectors

TypeNameDefaultDescription
AixLib.Fluid.HeatPumps.ModularReversible.BaseClasses.RefrigerantMachineControlBussigBus (from PartialIcingFactor)Bus-connector used in a heat pump
Modelica.Blocks.Interfaces.RealOutputiceFac (from PartialIcingFactor)Icing factor from 0 to 1 to estimate influence of icing

Components

TypeNameDefaultDescription
Modelica.Blocks.Sources.RealExpressiongroRatFor_internal (from PartialVelocityBased)Growth rate for forced convection from internal calcuations
Modelica.Blocks.Sources.RealExpressiongroRatNat_internal (from PartialVelocityBased)Growth rate for natural convection from internal calcuations
Modelica.Blocks.Logical.SwitchswitchGrowthRate (from PartialVelocityBased)
Modelica.Blocks.Logical.SwitchswiMFloIce (from PartialVelocityBased)Switch between ice growth rates
Modelica.Blocks.Math.GaingaiADen (from PartialVelocityBased)Gain with area and density
Modelica.Blocks.Math.ProductgaiDenCoeff (from PartialVelocityBased)Gain with density coefficient
Modelica.Blocks.Math.GaingaiWatFus (from PartialVelocityBased)Negate and divide by fusion enthalpy
Modelica.Blocks.Logical.Andand1 (from PartialVelocityBased)Is on and heating
Modelica.Blocks.Math.GaindivIceMax (from PartialVelocityBased)Divide by maximal ice mass
Modelica.Blocks.Math.AddgaiADen2 (from PartialVelocityBased)Gain with area and density
Modelica.Blocks.Sources.ConstantconOne (from PartialVelocityBased)Upper efficiency limit
Modelica.Blocks.Sources.RealExpressiondenCoe_internal (from PartialVelocityBased)Internal density coefficient calculation based on zones
Modelica.Blocks.Routing.RealPassThroughreaPasThrTOda (from PartialVelocityBased)Outdoor air temperature
Modelica.Blocks.Math.ProductproAGroRatDen (from PartialVelocityBased)Gain with area and density
Modelica.Blocks.Sources.ConstantconDen (from PartialVelocityBased)Constant density
AixLib.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.Frosting.BaseClasses.IceMassIntegratoriceMassIntegrator (from PartialVelocityBased)
AixLib.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.Frosting.BaseClasses.FrostDensityKornfroDenKornPT1 (from PartialVelocityBased)Frost density according to Korn
AixLib.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.Frosting.BaseClasses.ZhuFrostingZonezhuFroZonCurrent frosting zone
Modelica.Blocks.Sources.RealExpressiontimeFirstFroTime of first frost after last defrost
Modelica.Blocks.Logical.TimertimeOnTime device is on since last defrost

Revisions

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