In this amazing video of multiple camera angles of Endeavour landing and post-landing processing, at around the 15:45–15:56 minute mark, we see a large propeller running in front of the Orbiter.
It seems to be perfectly aligned with the Orbiter's centerline (see orange mark).
What is its purpose, and what is it called?
I first thought it might be there to provide airflow to carry fumes into a defined direction in case of a spill of Hydrazine or other nasty chemicals, but actually, there is a lot of people working downwind near the back of the Orbiter. Also, by this point, the guys in the hazmat suits seen earlier in the video, would have already removed those chemicals, I guess.
So, the only other reason I can come up with, is cooling. However, isn't it a little bit small and too far away for that, or am I misjudging the power of a ~4m propeller? And what exactly is it cooling? The tiles, the crew compartment, the crew van?