You write in an evaluation your findings (in an experiment, etc.) by a systematic determination of its worth or significance using criteria against a set of standards. You find out whether it meets the standards or it did not meet the standards.
You write in a conclusion your findings whether your proposition is arrived up after a thorough consideration of evidence, arguments or other premises, or not.
evaluation sums up your findings, what could have been done better, if anything went wrong, what you would do differently next time.
the conclusion basically concludes your findings. go back to the original experiment - did your findings support what your theory was? if not, why not?