How to install a window a/c unit outside

I shed with a very small window, which I use mainly for storage, but I have a little piece of work on the bench, etc. I also have a window mounted air conditioners that I have received from mostly free (trade). The unit is probably old, but my friend said that he had not used much. This evaporative cooler, by the way. The regular, 220 volts AC. I am planning to establish a reserve for him (from treated wood) near the outer wall of the barn and even putting a little roof over it. I then route air through the barn wall, using a round air duct (s) — The use of 8 or 10-inch channel (s), I think. I fully with the novice / C and the front of missing air-conditioning, so I am not sure exactly how it works. I assume that the upper area of food and reduce air pollution events. So, I know if I need two separate channels, or if I can just run through every single channel? Using two separate channels, it did not matter if the channels are physically close together inside the shed? Can I just set it to suck the air from the outside shed, and then open the window? Air conditioning is much, much more than I really need. The 28,000 BTU capacity and shed about 300 square feet of open sound and very little insulation and four small air vents in the roof. I did not shed much use can be 20 or 30 hours a year. So, the electric bill is not the issue. In hot weather, as we are now, though, is to shed about 100 degrees, so I would like to be able to cool, and cool off quickly when I do need to do a small project, etc. I guess I will have to go to a local sheet-metal shop and fabricated something, I wonder, but if I could just make something of canvas and PVC pipe, for example. / C unit will be behind the barn, where it does not show, so it does not matter if your looks a bit kludgy.