Buildings.Fluid.HeatExchangers.CoolingTowers.Data

Cooling tower performance data

Information

Package with performance data for cooling towers.

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

Package Content

Name Description
Buildings.Fluid.HeatExchangers.CoolingTowers.Data.UAMerkel UAMerkel UA correction factors for Merkel cooling towers

Buildings.Fluid.HeatExchangers.CoolingTowers.Data.UAMerkel Buildings.Fluid.HeatExchangers.CoolingTowers.Data.UAMerkel

UA correction factors for Merkel cooling towers

Information

This data record contains the cooling tower performance data for Buildings.Fluid.HeatExchangers.CoolingTowers.Merkel. Similar to the CoolingTower:VariableSpeed:Merkel model in EnergyPlus, Merkel's theory is modified to include Scheier's adjustment factors that adjust UA values at off-design conditions. The three factors are:

The user can update the values in this record based on the performance characteristics of their cooling tower.

These three adjustment factors are used to calculate the UA value as

UAe = UA0 · fUA,wetbulb · fUA,airflow · fUA,waterflow,

where UAe and UA0 are the equivalent and design overall heat transfer coefficent-area products, respectively.

The factors fUA,wetbulb, fUA,airflow, and fUA,waterflow adjust the current UA value for the current wetbulb temperature, air flow rate, and water flow rate, respectively. These adjustment factors are third-order polynomial functions defined as

fUA,x = cx,0  + cx,1 x + cx,2 x2 + cx,3 x3,

where x = {(T0,wetbulb - Twetbulb),   ṁair ⁄ ṁ0,air,   ṁwat ⁄ ṁ0,wat} for the respective adjustment factor, and the coefficients cx,0, cx,1, cx,2, and cx,3 are the user-defined values for the respective adjustment factor functions obtained from Buildings.Fluid.HeatExchangers.CoolingTowers.Data.UAMerkel.

Extends from Modelica.Icons.Record (Icon for records).

Parameters

TypeNameDefaultDescription
Performance curves
RealcDifWB[3]{1,0.0081,0}Polynomial coefficients for correction of design wet bulb minus actual wet bulb temperature
RealcAirFra[3]{0,1.3,-0.3}Polynomial coefficients for correction for fractional air flow rate
RealcWatFra[3]{0.1082,1.667,-0.7713}Polynomial coefficients for correction for fractional water flow rate
RealFRAirMin0.2Minimum value for air flow fraction
RealFRAirMax1.0Maximum value for air flow fraction
RealFRWatMin0.3Minimum value for water flow fraction
RealFRWatMax1.0Maximum value for water flow fraction
TemperatureDifferenceTDiffWBMin-10Minimum value for leaving evaporator temperature difference [K]
TemperatureDifferenceTDiffWBMax25Maximum value for leaving evaporator temperature difference [K]

Modelica definition

record UAMerkel "UA correction factors for Merkel cooling towers" extends Modelica.Icons.Record; parameter Real cDifWB[3]={1,0.0081,0} "Polynomial coefficients for correction of design wet bulb minus actual wet bulb temperature"; parameter Real cAirFra[3]={0,1.3,-0.3} "Polynomial coefficients for correction for fractional air flow rate"; parameter Real cWatFra[3]={0.1082,1.667,-0.7713} "Polynomial coefficients for correction for fractional water flow rate"; parameter Real FRAirMin(min=0) = 0.2 "Minimum value for air flow fraction"; parameter Real FRAirMax(min=0)= 1.0 "Maximum value for air flow fraction"; parameter Real FRWatMin(min=0) = 0.3 "Minimum value for water flow fraction"; parameter Real FRWatMax(min=0) = 1.0 "Maximum value for water flow fraction"; // Range for the curves parameter Modelica.SIunits.TemperatureDifference TDiffWBMin( max=0, displayUnit="K")= -10 "Minimum value for leaving evaporator temperature difference"; parameter Modelica.SIunits.TemperatureDifference TDiffWBMax( min=0, displayUnit="K")= 25 "Maximum value for leaving evaporator temperature difference"; end UAMerkel;