This is a really good question. I would say he probably just enters a deep sleep. He's already undead and Death is his servant. I think when death is beaten, he's not necessarily sent to Hell, as much as he is dismissed to being powerless in this world for a certain number of years against his enemies, like the Belmonts and can't really attack and try to end ones life before fate unless their time is up on earth. Dracula though just probably retreats to a deep hibernation as a way of building his strength and the whole being killed and resurrection thing could just be a distraction to the Belmonts. (and other foes of Dracula)