Evaluating Water Package Unit Chiller effeciency

Hi all,

I have to evaluate the efficiency of water package unit chiller to determine the real needs of cooling capacity for replacing the old chiller. It still uses R -22 as refrigrant. My question is about how to calculate thermal side to determine the efficiency. I think there are two way to calculate it :

1. Calculating the heat rate (J/s) of refrigerant in evaporative coil by measuring the temperature and pressure at the refrigeration cycle so I get the enthalpy difference in before and after coil by looking the R-22 graph. OR

2. Calculating the heat rate (J/s) of water in evaporative coil by measure the temperature and velocity of air to get mass flow rate.

Am I right? and if I am right, Which way is better in accuracy and easiness to do?

Thank you for your help.