I have seen these things for sale a lot lately and they do not make any sense to me. How could you have an air-conditioner in the middle of your room? I thought that air-conditioners are basically heat-pumps, and that they, by their very nature, had to produce more heat than cold. How do these portable versions work? Do they maybe have a tank of water that they heat while cooling the air?
There’s an exhaust hose that you hang out a window. The cold air is released into the room, while the hot air goes through the exhaust hose and out of the room.
Could the heat be stored inside the unit, like in a tank of water as you suggest? I suppose so. But then you’d have to turn off the AC every so often to dump the hot water; otherwise, you’d risk an explosion.
If you’re seeing ads for portable coolers that don’t use exhaust hoses, they’re probably swamp (evaporative) coolers, not air conditioners.
There’s an exhaust hose you run out a window to blow out the hot air, and a drip pan to collect the water that condenses on the evaporator coils that you have to periodically empty. Other than that, they work exactly like a window unit. That, and they cost about $300 more than a similar cooling capacity window unit.
Are you talking about something like this? If so, they do have hoses that vent to the outdoors, not unlike the vent from a dryer. I believe that you usually run the hoses out a window.
Of course, I don’t actually own one of these, so I could be off-base.
Ahh, I feel relieved. When I was discussing this with my grandma I did wonder if their my be a hose.
Thanks for the quick and helpful response. Another score for the SDMB. 
There are also devices called “swamp coolers” which are quite effective if you remain within the “cone” of the cooler fan’s output. They’re great for sleeping. They’re entirely self-contained; there are no hoses or anything to drag out to a window or anything like that.
You get about 20 degrees cooling over ambient temperature, and contrary to some claims, they work just fine even in fairly high humidity (although the performance begins decreasing when you get to around 95% humidity).
I own one and I consider it to have been a good purchase, even though I have central air, too.
Unless you have an anti-Kelvin air conditioner. =) Although, if you want to get like that, it’s not producing cold, it’s transferring heat from one side of the device to the other, which has the effect of reducing the temperature on one side and increasing the temperature by a larger amount on the other.