What do you mean by "effective in the knowledge transfer"?
Remember that Scrum is a framework not a methodology or process. I don't quite understand what you expect to find in the Scrum framework specifically to knowledge transfer. In my opinion, knowledge transfer is usually accomplished by some set of tasks which would make it procedural.
However, Scrum does advocate the transparency of information and continuous collaboration. Both of those facilitate knowledge transfer. So while is it not specifically mentioned, there are inferences to activities, events, and artifacts that lead to knowledge transfer.
Scrum helps to build transparency among Scrum teams. Scrum builds teams, their knowledge, skills and ability to deliver working product increment end of the sprint. There is no anything specific in SG about the topic, but such a environment (transparency, focus on teams not individuals) is a great place to transfer the knowledge to the others.
The knowledge transfers actually happens implicitly, during ceremonies, discussions, working on PBI items etc. - when new developer joins.