Abstract: A baffle for partitioning fluid circulating passages that are provided in a structure for heat transfer purposes. The baffles are inserted without the need for extra drilling and tapping of the structure, and include an elongated, substantially flat body which is inserted into a passage to thereby partition the passage into two conduits, which act as supply and return conduits for fluid flow. The baffle further extends into another passage, through which fluid flows, to thereby block the flow of fluid and force the fluid to flow through the partitioned passage via the defined conduits. The baffle is held into position by resilient arms which project outwardly from the baffle and are received fully within the non-partitioned passage.