Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle

Package for chiller refrigerant cycle modules

Information

This package contains models and data to for dynamic refrigerant cycles with stationary data points, evaporator frosting, and cycle inertia.

Extends from Modelica.Icons.MaterialPropertiesPackage (Icon for package containing property classes).

Package Content

Name	Description
ConstantCarnotEffectiveness	Carnot EER with a constant Carnot effectiveness
TableData2D	Performance data based on condenser outlet and evaporator inlet temperature
TableData2DLoadDep	Data-based model dependent on evaporator and condenser entering or leaving temperarure and PLR
BaseClasses	Package with partial classes of performance Data

Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle.ConstantCarnotEffectiveness

Carnot EER with a constant Carnot effectiveness

Information

This model uses a constant Carnot effectiveness approach to compute the efficiency of the chiller.

PEle_nominal is computed from the provided QCoo_flow_nominal and other nominal conditions. PEle_nominal stays constant over all boundary conditions and is used to calculate PEle by multiplying it with the relative compressor speed. QEva_flow is computed using the Carnot approach:

QEva_flow = PEle_nominal * etaCarnot_nominal * yMea * (TEvaOut - TAppEva) / (TConOut + TAppCon - (TEvaOut - TAppEva))

PEle = PEle_nominal * yMea

These equations follow the same methods used in Buildings.Fluid.Chillers.Carnot_y Similarly, the variables TAppCon and TAppEva define the approach (pinch) temperature differences.

The approach temperatures are calculated using the following equation:

TApp = TApp_nominal * Q_flow / Q_flow_nominal

This introduces nonlinear equations to the model, which can lead to solver issues for reversible operation. You can use the nominal values as a constant by enabling use_constAppTem

Extends from Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle.BaseClasses.PartialChillerCycle (Partial model of refrigerant cycle used for chiller applications), Buildings.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.BaseClasses.PartialCarnot (Model with components for Carnot efficiency calculation).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle.TableData2D

Performance data based on condenser outlet and evaporator inlet temperature

Information

This model uses two-dimensional table data typically given by manufacturers as required by e.g. European Norm 14511 or ASHRAE 205 to calculate QEva_flow and PEle.

For different condenser outlet and evaporator inlet temperatures, the tables must provide two of the three following values: electrical power consumption, evaporator heat flow rate, and COP.

Note that losses are often implicitly included in measured data. In this case, the frosting modules should be disabled.

Scaling factor

For the scaling factor, the table data for evaporator heat flow rate (QEvaTabDat_flow) is evaluated at nominal conditions. Hence, the scaling factor is

scaFac = QEva_flow_nominal/QEvaTabDat_flow(TEva_nominal, TCon_nominal).

Using scaFac, the table data is scaled linearly. This implies a constant COP over different design sizes:

QEva_flow = scaFac * tabQEva_flow.y

PEle = scaFac * tabPel.y

Known Limitations

• Manufacturers are not required to provide the compressor speed at which the data are measured. Thus, nominal values may be obtained at different compressor speeds and, thus, efficiencies. To accurately model the available thermal output, please check that you use tables of the maximal thermal output, which is often provided in the data sheets from the manufacturers. This limitation only holds for inverter driven chillers.
• We assume that the efficiency is contant over the whole compressor speed range. Typically, efficiencies will drop at minimal and maximal compressor speeds. To model an inverter controlled chiller, the relative compressor speed yMea is used to scale the ouput of the tables linearly. For models including the compressor speed, check the SDF-Library dependent refrigerant cycle models in the AixLib Library.

References

EN 14511-2018: Air conditioners, liquid chilling packages and heat pumps for space heating and cooling and process chillers, with electrically driven compressors https://www.beuth.de/de/norm/din-en-14511-1/298537524

Extends from Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle.BaseClasses.PartialChillerCycle (Partial model of refrigerant cycle used for chiller applications), Buildings.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.BaseClasses.PartialTableData2D (Partial model with components for TableData2D approach for heat pumps and chillers).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle.TableData2DLoadDep

Data-based model dependent on evaporator and condenser entering or leaving temperarure and PLR

Information

This model serves as a wrapper class to integrate the block Buildings.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.BaseClasses.TableData2DLoadDep into chiller models. For a complete description of all modeling assumptions, please refer to the documentation of this block.

Extends from Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle.BaseClasses.PartialChillerCycle (Partial model of refrigerant cycle used for chiller applications).

Parameters

Connectors

Modelica definition