tv series may be understood as like released in parts -1,2,3,4,5......... tv serial mean which is like a drama of episodes for a long run whether daily or weekly.

"TV series" refers to a television program running for multiple episodes. This can be from nearly any genre. A series can run for one season, or many seasons. This generally does not include something like a news program, but will include cartoons, reality TV, dramas, and even talk shows. "TV serial" refers to a television series that has a long running plot (ie. something where you need to watch the episodes in order to make sense of them). This is not a term used in common everyday English though. People normally refer to this type of show as a series as well.