Well, you may not want to revent the hot air from the HPS back into the room if you can avoid it and if I understand the set up correctly. I would think about trying to use the larger of the two fans you have and put it on the cool tube and the scrubber and use the smaller fan to draw fresh air into the area. Also, put a small rotating fan in there to creat some air circulation that will help strengthen the plants stems and branches and remove and carry O2, CO2 and moisture that the plant is disapating and absorbing from and into its leaves.
Hope this helps some
Adieu