Abstract: The fluid processing apparatus of the present invention comprises a housing having a first fluid inlet and a first fluid outlet; a fluid processing tubular means received in the housing; partitions securing the opposed ends of the fluid processing tubular means to the housing in a fluid tight seal to partition the housing interior into a first fluid chamber in fluid communication with the first fluid inlet and the first fluid outlet and a second fluid chamber defined in the fluid processing tubular means; a second fluid inlet and a second fluid outlet in fluid communication with the second fluid chamber; and projections formed on an inner surface of one end portion of the housing so as to project toward the nearer end opening of the housing, said partition of the one end portion side of said housing being secured to the one end portion of the housing so that the projections are positioned within the partition.