Hull weren't the only club keen on Carvalho but owner Acun Ilicali told Sky Sports News that the deal is almost agreed.
"We agreed all terms with him. I'm very happy to say he's going to wear the Hull shirt. It's almost done. The announcement has to be done, that's all. The club will do it," he said.
"So many clubs wanted him and he chose us. It's because of the way we are playing the game. Liam Rosenior has a big effect on that, playing nice football.
"He wants to go to a place where he will enjoy football. Hull is the best place for him to improve his talents. We are a fantastic club with fantastic players and a fantastic coach. Everything is so good here."