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:
cDifWB
- Corrected UA based on the difference between the
current wetbulb temperature and the design wetbulb temperature.
cAirFra
- Corrected UA based on the ratio of the current air
flow rate and the design air flow rate.
cWatFra
- Corrected UA based on the ratio of the current water
flow rate and the design water flow rate.
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
UA_{e} = UA_{0} · f_{UA,wetbulb} · f_{UA,airflow} · f_{UA,waterflow},
where UA_{e} and UA_{0} are the equivalent and design overall heat transfer coefficent-area products, respectively.
The factors f_{UA,wetbulb}, f_{UA,airflow}, and f_{UA,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
f_{UA,x} = c_{x,0} + c_{x,1} x + c_{x,2} x^{2} + c_{x,3} x^{3},
where x = {(T_{0,wetbulb} - T_{wetbulb}), ṁ_{air} ⁄ ṁ_{0,air}, ṁ_{wat} ⁄ ṁ_{0,wat}} for the respective adjustment factor, and the coefficients c_{x,0}, c_{x,1}, c_{x,2}, and c_{x,3} are the user-defined values for the respective adjustment factor functions obtained from Buildings.Fluid.HeatExchangers.CoolingTowers.Data.UAMerkel.