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

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:

• 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 = UA₀ · f_UA,wetbulb · f_UA,airflow · f_UA,waterflow,

where UA_e and UA₀ 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 x² + c_x,3 x³,

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.

Revisions

• October 22, 2019, by Yangyang Fu:
  First implementation.