blockDryCoolerUA
Block that computes UA, effectiveness, and heat transfer of a dry cooler
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Information
Block that computes the overall thermal conductance UA, the heat exchanger effectiveness ε, and the heat flow rate Q̇ for a dry cooler.
Main relationships
The overall conductance is computed from the
convective heat transfer coefficients on the coolant side
hACoo and the air side hAAir as
UA = corUA ⁄ (1 ⁄ hAcoo + 1 ⁄ hAair),
where corUA is a correction factor that reduces UA in the free-convection regime when the fan is off.
The effectiveness–NTU method is used to compute the heat flow rate transferred from water to air.
Assumptions
- The heat exchanger flow configuration is treated as cross-flow with both streams unmixed.
- The specific heat capacity of air is evaluated at nominal conditions.
- The specific heat capacity of the cooling fluid is evaluated at the inlet temperature.
References
For further documentation, see Buildings.Fluid.HeatExchangers.CoolingTowers.DryCooler.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Fluid.HeatExchangers.CoolingTowers.Data.DryCooler.Generic | dat | Performance data record | |
| Modelica.Units.SI.ThermalConductance | UA_nominal | NTU_nominal*CMin_flow_nominal | Thermal conductance at nominal flow, used to compute heat capacity |
| Real | eps_nominal | dat.Q_flow_nominal/((dat.TAirIn_nominal - dat.TCooIn_nominal)*CMin_flow_nominal) | Nominal heat transfer effectiveness |
| Real | NTU_nominal | Buildings.Fluid.HeatExchangers.BaseClasses.ntu_epsilonZ(eps = min(0.99999, max(1E-6, eps_nominal)), Z = Z_nominal, flowRegime = Integer(Buildings.Fluid.Types.HeatExchangerConfiguration.CrossFlowUnmixed)) | Nominal number of transfer units |
| Real | Z_nominal | CMin_flow_nominal/CMax_flow_nominal | Ratio of capacity flow rate at nominal condition |
| Modelica.Units.SI.Temperature | TAirOut_nominal | dat.TAirIn_nominal - abs(dat.Q_flow_nominal)/CAir_flow_nominal | Nominal leaving air drybulb temperature |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal | Nominal mass flow rate of water | |
| Fan | |||
| Modelica.Units.SI.MassFlowRate | mAir_flow_nominal | m_flow_nominal/dat.ratCooAir_nominal | Nominal mass flow rate of air |
| Real | yMin | Minimum control signal until fan is switched off (used for smoothing between forced and free convection regime) | |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealInput | y | Fan control signal | |
| Modelica.Blocks.Interfaces.RealInput | mAir_flow | Air mass flow rate | |
| Modelica.Blocks.Interfaces.RealInput | mCoo_flow | Cooling fluid mass flow rate | |
| Modelica.Blocks.Interfaces.RealInput | TCooIn | Inlet water temperature | |
| Modelica.Blocks.Interfaces.RealInput | TAirIn | Entering air dry bulb temperature | |
| Modelica.Blocks.Interfaces.RealInput | hACoo | Convective heat transfer coefficient times area on the coolant side | |
| Modelica.Blocks.Interfaces.RealInput | hAAir | Convective heat transfer coefficient times area on the air side | |
| Modelica.Blocks.Interfaces.RealOutput | Q_flow | Heat removed from water |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Real | eps | Heat exchanger effectiveness | |
| Modelica.Units.SI.SpecificHeatCapacity | cpCoo | Heat capacity of cooling loop fluid | |
| Modelica.Units.SI.ThermalConductance | CAir_flow | Heat capacity flow rate of air | |
| Modelica.Units.SI.ThermalConductance | CCoo_flow | Heat capacity flow rate of water | |
| Modelica.Units.SI.ThermalConductance | CMin_flow | Minimum heat capacity flow rate | |
| Modelica.Units.SI.HeatFlowRate | QMax_flow | Maximum heat flow rate into air | |
| Modelica.Units.SI.ThermalConductance | UA | Thermal conductance |
Contents
| Name | Description |
|---|---|
 Medium | Medium in the component |
 Airprotected | Package of medium air |
Revisions
-
June 24, 2026, by Michael Wetter:
Corrected flow regime which was inconsistent between computation of parameters and time domain simulation.
This is for Buildings, #4648. -
April 27, 2026, by Michael Wetter:
First implementation.