modelMerkelEnergyPlus
Validation with EnergyPlus model for Merkel's cooling tower
Extends from Modelica.Icons.Example (Icon for runnable examples).
Information
This model validates the model Buildings.Fluid.HeatExchangers.CoolingTowers.Merkel by comparing against results obtained from EnergyPlus.
The EnergyPlus results were obtained using the example file
CoolingTower:VariableSpeed, with the cooling tower evaluated as
the CoolingTower:VariableSpeed:Merkel model from EnergyPlus.
The difference in results of the cooling tower's leaving water temperature
(tow.TLvg and TLvg.EP)
during the middle and end of the simulation is because the mass flow rate is
zero. For zero mass flow rate, EnergyPlus assumes a 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.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Density | rhoWat | MediumWat.density(MediumWat.setState_pTX(MediumWat.p_default, MediumWat.T_default, MediumWat.X_default)) | Default density of water |
| Modelica.Units.SI.Density | rhoAir | MediumAir.density(MediumAir.setState_pTX(MediumAir.p_default, MediumAir.T_default, MediumAir.X_default)) | Default density of air |
| Modelica.Units.SI.SpecificHeatCapacity | cpWat | MediumWat.specificHeatCapacityCp(MediumWat.setState_pTX(MediumWat.p_default, MediumWat.T_default, MediumWat.X_default)) | Default density of water |
| Modelica.Units.SI.PressureDifference | dp_nominal | 6000 | Nominal pressure difference of cooling tower |
| Modelica.Units.SI.VolumeFlowRate | VWat_flow_nominal | 0.00109317 | Nominal volumetric flow rate of water (medium 2) |
| Modelica.Units.SI.VolumeFlowRate | VAir_flow_nominal | 0.561240 | Nominal volumetric flow rate of air (medium 1) |
| Modelica.Units.SI.Temperature | TAirInWB_nominal | 25.60 + 273.15 | Nominal outdoor wetbulb temperature |
| Modelica.Units.SI.TemperatureDifference | TRan | 5.50 | Range temperature (difference between water in and out) |
| Modelica.Units.SI.TemperatureDifference | TApp | 3.90 | Approach temperature (difference between water out and wetbulb) |
| Modelica.Units.SI.Temperature | TWatOut_initial | 33.019 + 273.15 | Nominal water inlet temperature |
| Modelica.Units.SI.Power | PFan_nominal | 213.27113 | Nominal fan power |
| Real[:] | r_VEnePlu | {0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1} | Fan control signal |
| Real[:] | r_PEnePlu | {0, 0.020982275, 0.027843038, 0.046465108, 0.082729139, 0.142515786, 0.231705701, 0.356179538, 0.521817952, 0.734501596, 1} | Fan power output as a function of the signal |
| Modelica.Units.SI.MassFlowRate | mWat_flow_nominal | VWat_flow_nominal*rhoWat | Nominal mass flow rate of water (medium 2) |
| Modelica.Units.SI.MassFlowRate | mAir_flow_nominal | VAir_flow_nominal*rhoAir | Nominal mass flow rate of air (medium 1) |
| Real | ratWatAir_nominal | mWat_flow_nominal/mAir_flow_nominal | Nominal water-to-air ratio |
| Modelica.Units.SI.Temperature | TWatIn_nominal | TWatOut_nominal + TRan | Nominal water inlet temperature |
| Modelica.Units.SI.Temperature | TWatOut_nominal | TAirInWB_nominal + TApp | Nominal water outlet temperature, 29.5 in EnergyPlus |
| Modelica.Units.SI.HeatFlowRate | Q_flow_nominal | mWat_flow_nominal*cpWat*(TWatOut_nominal - TWatIn_nominal) | Cooling capacity at design conditions |
| Data.Merkel.Generic | dat | Cooling tower performance data |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Sources.CombiTimeTable | datRea | Reader for "CoolingTower_VariableSpeed_Merkel.idf" energy plus example results | |
| Buildings.Fluid.HeatExchangers.CoolingTowers.Merkel | tow | Merkel-theory based cooling tower | |
| Sources.MassFlowSource_T | souWat | Water source to the cooling tower | |
| Sources.Boundary_pT | sinWat | Water sink from the cooling tower | |
| Controls.OBC.UnitConversions.From_degC | TEntWat | Block that converts entering water temperature | |
| Controls.OBC.UnitConversions.From_degC | TAirWB | Block that converts entering air wetbulb temperature | |
| Modelica.Blocks.Sources.RealExpression | TLvg_EP | EnergyPlus results: cooling tower leaving water temperature | |
| Modelica.Blocks.Sources.RealExpression | Q_flow_EP | EnergyPlus results: cooling tower heat flow rate | |
| Modelica.Blocks.Sources.RealExpression | PFan_EP | EnergyPlus results: fan power consumption |
Contents
| Name | Description |
|---|---|
 MediumAir | Air medium model |
 MediumWat | Water medium model |
Revisions
-
April 27, 2026, by Michael Wetter:
Refactored for new cooling tower implementation.
This is for issue 4567. -
April 30, 2025, by Kathryn Hinkelman:
Corrected the wetbulb valueTAirInWB_nominaland added intermediate equations from E+ to model.
This is for #4189. -
December 23, 2019, by Kathryn Hinkelman:
First implementation.