In order to help knowledge acquirement and accumulation from past experiences, we propose a KFC (Knowledge Feedback Cycle) framework among engineers and researchers. Three tools (Empirical Project Monitor, Simulator, and Replayer) are used to circulate captured knowledge in KFC. The Project Replayer is a most characteristic tool used to review data of past projects derived from development logs; CVS, bug reports and e-mails. With the Project Replayer, past projects can be easily revisited and complicated phenomena of the past projects can be investigated. As a result of preliminary experiments, we have confirmed that the Project Replayer helps researchers construct and validate hypotheses of software process. We also confirmed that developers have acquired new knowledge about a certain problem extracted from past projects.