Abstract: A motionless fluid mixing device having a tubular conduit in which right-hand and left-hand primary helical baffles are alternatingly arranged in spaced, serial relation with smaller helical connecting baffles extending centrally in the conduit between the primary baffles. The conduit has an entrance and exit end, each connecting baffle being helically curved oppositely to the primary baffle on the entrance end side of the connecting baffle for preventing center channeling of fluids flowing through the conduit by obstructingly deflecting and turbulently diffusing outwardly the portion of fluids flowing centrally in the conduit.