Dear brian21954,
You have only stated two miles(10560 feet),the other data required is diameter,material of construction,fluid properties or The fluid ,the initial temperature,the prevaling wind speed in your location(for overground pipe)..
There are graphs,indicating heat loss per square foot of exposed area (BTU/SQ FT),from which you can calculate the heat lost ,which then can be translated into temperature drop for your inside fluid.
If you have a temperature sensitive case,then you should insulate to avoid any problems..
For references,check in Kern (Process Heat Transfer)
Regards,
Whylie