I understand that your DWC isnt the "R" version, so this may be just too much work to be much use to you, but this is how I chill my nutrients without a chiller...
I have two General Hydro Rainforest Aeroponic systems that I gutted and made into a 12 site RDWC system (I only use 4 sites to due crowding). This season, ay the beginning, I decided to add a chiller. I bought a 1/4 HP unit for 50 gallons worth of liquid refreshment and it showed up thrashed. It sounded like a box of broken Mason jars when you shook it... This thing was chooched. At the time the weather was 106. I grow in a insulated shed in the backyard. Inside the shed air was way over 90(air conditioner wasnt in yet) but my nutrients were 84! I'm thinking im gonna end up giving a funeral, and starting over. So I put in a window AC, i decided to run ducting and an inline fan (6") from my air conditioner to a 6 inch hole in my res lid. I only use 1/3 of the output fron the AC. At that time i just rested the lid on the res. So the cold air could escape. Bottom line is, in less than 12 hours i was down to 74 degrees. I was using Subculture from Gen Hyd. and I have 2 large air pumps with 12" diffusers, so air wasn't really an issue. I have since gotten the nute temp down to 60 while trying to make my Ayahuasca Purple, purple. That's next. When it gets toward the end of the grow, in about 4 weeks and it cools off a but more I will chill the nutes, and air to get some color in my flowers.
I've never heard of anyone using the AC to cool their water like this, but I'm sure it's been done. It's too easy not to have been done before. Anyway, if you ever link your pots together and add a central res. you may want to think about it.