Hi, I am involved in a project that cools outside air to underground temperatures at 6' below ground in Florida soil. we are using thin wall PVC @ 4" diameter. i am looking for an equation that will tell me how long to make the pipe and what the ideal cfpm should be to achieve desired temperature for exiting air. this is my first time visiting a forum of any type and my experience in physics is limited. i have been educated in algebra, that should come in handy.