A portable air conditioners should be connected to an "exhaust hose" or "vent hose" to remove the the hot air they eject. Most portable air conditioners extract hot from the room in which it is located, that hot air is then discharged out the of the a/c unit. An exhaust hose can be connected to the portable ac unit to lead the warm air out of the window.
The most efficient way to remove hot air from a room is when you connect a flexible exhaust hose to the back of your portable ac unit and connect the other end of the hose to a window venting kit.