Catalysis of the reaction: D-ribitol + NAD+ = D-ribulose + H+ + NADH.
Synonyms:
related_synonym:
adonitol dehydrogenase activity; ribitol dehydrogenase A (wild type); ribitol dehydrogenase B (mutant enzyme with different properties); ribitol dehydrogenase D (mutant enzyme with different properties); ribitol:NAD+ 2-oxidoreductase activity