You can do the dry ice thing... but, IMO, it's really impractical.
I think you need to see it for yourself...
I like that you're "thinking outside the box", but, again, just my opinion, it's impractical.
But hey, try it if you want!

Temperatures:::
1- good fans.. you can have good airflow in there. That will help.
Nothing beats an air conditioning unit... but it's completely do-able without!

2- cool tube... these help tons. And are easy to build your own.
You can check the FAQs for build your own... and/or eBay for "Bake-A-Round"



Best,

-turtle420
.