The arrows in my screenshot point to fans, not the thrusters. The closer you get to a heat source, the faster they spin.
http://i.imgur.com/iXmsX8X.jpg
Those are attitude control thrusters. It's how your ship changes pitch/roll/yaw and slows down or reverses.
Don't ask me why they have fan blades or why they spin or even why they might seem to spin faster in a given situation.
Maybe they're jet turbines for future atmospheric flight, but those are in fact RCS thrusters and have nothing to do with heat dissipation.
Switch to external camera mode while you're flying and maneuver your ship around, you'll see the thrusters firing.
I can't switch to my Python right now but you can see the RCS thrusters firing on my Anaconda in the photo below as I pitch my nose down.
The bow dorsal thrusters push down, and you can't it see here, but the stern ventral thrusters fire to push the rear up.
In your photo, you can see the heat radiators glowing which are how your ship dissipates heat.
Your radiator vents are open, probably because you're near a star.