The Coil:Cooling:DX objects have an input value for Condenser Type, where you can specify EvaporativelyCooled. Other relevant inputs are 'Evaporative Condenser Effectiveness', 'Evaporative Condenser Air Flow Rate' and 'Evaporative Condenser Pump Rated Power Consumption'. Also note this part of the effectiveness input description, which I believe is relevant to your case:

If the user wishes to model an air-cooled condenser that has evaporative media placed in front of it to cool the air entering the condenser coil, then the user should specify Condenser Type = Evap Cooled. The user must also enter the appropriate evaporative effectiveness for the media. In this case, the Total Cooling Capacity Modifier Curve (function of temperature) and the Energy Input Ratio Modifier Curve (function of temperature) input fields for this object should reference performance curves that are a function of outdoor dry-bulb temperature. Be aware that the evaporative media will significantly reduce the dry-bulb temperature of the air entering the condenser coil, so the Total Cooling Capacity and EIR Modifier Curves must be valid for the expected range of dry-bulb temperatures that will be entering the condenser coil.

You'll notice that those input fields are not exposed in the OpenStudio app, so you'll have to use API methods to change/set those fields. Here is an existing measure that will set the DX cooling coils in the air loop of your choice to have evaporatively-cooled condensers.