Effectiveness of an Evaporative Condenser

A1) Compare it current effectiveness with the "as commissioned" records, and look at what has changed.

A2) Please define the abbreviation <...TDS...>.

Q3) Does the address <...Gentlemen...> exclude those not fitting that label from answering?

The effectiveness should be rather obvious, is it doing the job...? The performance can be determined measuring the amount of heat being removed, outgoing temp minus incoming temp of the coolant...

https://www.gradko.com/environmental/environmental-resources/technical-resources/technical-data-sheets/ammonia-technical-data-sheet.pdf

Maybe this will help:

http://business.edf.org/files/2014/03/Cooling-Tower-Handbook_FINAL.pdf

Here is an example that might help...

https://www.sciencedirect.com/topics/engineering/evaporative-condenser

Also this:

https://www.mdpi.com/1996-1073/12/11/2079/pdf

The term "effectiveness" is perhaps not the term you want to use. More likely, you seek to know the capacity of a prospective unit. None of the replies so far really addresses that.

For an industrial-size ammonia evap condenser, the capacity is typically listed in thousands of Btu/h (MBH) at various operating conditions on both the ammonia and water sides. Ordinarily a system designer or purchaser does not calculate this, but rather looks it up in mfrs' catalogs. You can get such literature on line from such companies as BAC, Evapco, Vilter, WatCo, and others.

However, if you are designing a unit from the ground up, there is much more involved in heat-exchange calculations than just a few formulas sharable in forum replies.

For the question about TDS levels, Rixter's link should have good info. Another good source is local water treatment experts.