Cooling Pipe: Need Options for 45° Temp Drop

[rlingineni]

I have a pipe that needs to be 5 degrees below the external temperature outside(eg- 45 degrees outside means 40 degrees within). I cannot remove the pipe or anything, all I can change is the what the pipe passes through, for example if it passes a block of ice then technically the pipe would cool also. So basically do you guys have any suggestions for what I can use to cool the pipe(also no sending anything through it besides air.

I would appreciate any suggestions.
Thank You,
Raviteja Lingineni

 

[Redbelly98]

Moderator's note: thread moved from General Physics to Mechanical Engineering.