Here's a plot comparing the models over a wide range of conditions. The range that I ran them over was:

• Inlet drybulb from 40 to 100 deg-F
• Inlet humidity ratio from 0.004 to 0.023
• Inlet water temperature from 65 to 100 deg-F
• Airflow ratio from 0.4 to 1.0
• Waterflow ratio from 0.4 to 1.0

The CoolTools model generally tended to underpredict the heat rejection rate compared to the YorkCalc model. I'm not sure of the reason for this. Here's a comparison of the two models vs a finite difference solution. Again, the CoolTools model tended to underpredict.