There is a type of portable AC which dumps the heat (or tries to) into the water it pulls out of the air as it dehumidifies. You can tell them apart because they don't have a hose to send hot exhaust air or water out the window. I don't have much experience with them, aside from knowing you need to empty the water tray occasionally or it'll overflow.
This is not correct. Portable a/c units have either 1 or 2 air ducts. With a single duct unit, some air is drawn from the conditioned space, through the condenser, and then outside. This is not ideal because you are wasting cool air, and creating a negative pressure in the space which will draw warm moist air back into the space. The 2 duct units are better because they draw outside air into the unit, through the condenser, and back out, so the heat rejection air is completely separate from the conditioned air. Most a/c units DO re-evaporate the condensate they produce, but they do so using the compressor's hot refrigerant gas discharge line. This actually helps efficiency a bit because some of the condensing is done before the condenser, but the primary purpose is so that you don't have to drain the condensate.
All portable a/c units have at least one duct. If there are no ducts then it is a dehumidifier not an air conditioner.
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