Akhilrajau :
I ordered Corsair CS 550M psu for my new build. My cabinet is Corsair 400R. So smps is bottom mounted.
My confusion is my PSU fan is intake or exhaust?
For a bottom mounted PSU, it is usually best to flip it upside down -so that i pulls air in through the bottom and spits it out the back: this gives the PSU its own little "eco system." If you put it in with the fan facing up/inside case -it will constantly pull hot air from the case out and through itself. This can lead to a hot PSU.
Just make sure you have clearance on the floor so the PSU/case is not flush against the carpet and not getting intake -an inch or two is fine.