Swamp ACs won't work when the humidity is high. I have a portable AC and I have made a window adapter for it since we are renting and a regular window AC is not allowed. Portable air conditioners do come with an adapter but for a casement window you're probably going to need to rig something. In my case I used a think piece of plywood that fits in to where the screen goes and made holes in it for the hoses. Then I drilled through the factory window adapter and bolted it to the plywood. It works very well.
The one I use is the Whynter ARC-126MDB. Before that one I had a Danby. It lasted about 3 years and the fan broke on it. I replaced it and it broke again about a year later so I went with a different unit. I think the motor was out of balance and the vibration cracked the plastic squirrel cage fan.
Now I have a two hose unit. This is better than a single hose like the last one. This makes it so there is a send and a return through the condenser both going outside so the inside air (which has been cooled) isn't being pulled outside with negative pressure, as well as hot air from other rooms. It makes it much more efficient.
Before buying I recommend checking as many reviews as possible on it. These things are typically built very cheap and when parts break it can take months to order replacement parts. Getting inside to service them is not for the faint of heart. I often go to Amazon.com just to read reviews then shop around for the best deal.
