Hi friend.
The ac portable has 2 streams of cold air and 2 hot, one enters and one exits.
The hot part, usually at the bottom of the ac, has only outside out, so it picks up the cool air from the environment and throws out, with full and all ..
A functional solution is to adapt a new duct in the entrance of the hot air, coming from outside, passing through the hot part and coming back out. So you keep circulating only cold air inside without removing anything.
I hope you understand what the free translator has explained to you, lucky.