Cool Tubes - Help!

Hey guys,
I've got a 6 x 8 ft area with 3 x 600w cool tubes, being cooled by a 5" 280 m3/hr fan. I currently have the "S" shape series setup, however the tubes obviously get progressively hot (especially the 3rd which is practically the same heat as it would be without the fan). This makes my room about 31 Degrees C in the winter, so I really need to loose 5 degrees or more.

Do you guys think I need just the one fan & a change in setup to parallel to get these puppies cool enough to be right above my plants & bring down the room temp? If so should I get one that is 400-700 m3/hr+ or should I get more fans?

Also, having looked at 5" fans, most of them are super expensive when you get past the 300-400 m3/hr range.
Say I went for a 6 or 7 inch fan... Would it be a mistake to funnel this from a 5" hole using a a reducer, then on the other side of the fan have another reducer so it links to my cool tubes? I'm thinking this will increase the pressure & therefore circulate much more cool air into the system.

Any help would be very much appreciated!

All the best,
W

im really new to growing, but just going off of basics on heat and air and shit like that, i would assume the parallel setup is waaay better than the S shape, i imagine that its getting really hot!. but like i said im new to growing, currently on my first grow.

I'd do the "s" and add a fan on each bend

Every turn or even slight deflection slows air velocity. The straighter the shot the less chance of it getting hot. However your diagram showing 2 equal legs and the shorter center section?The center will run the coolest. Equal length as much as possible for efficiency.