Patent ID: 7695675

Claim:
A method of irradiating a fluid with ultraviolet radiation from an axially disposed elongated UV source, said method comprising the steps of: (a) moving the fluid in a primary axial flow along the UV source; and (b) inducing within the moving fluid a circulating secondary flow superimposed on the primary flow, circulating transversally or radially relative to the surface of the UV source, the circulating secondary flow moving the fluid toward and away from the UV source wherein the UV source is at least one elongated UV lamp and wherein step (a) includes defining a reaction chamber surrounding the UV lamp and moving the fluid in a primary flow along the reaction chamber and wherein the circulating secondary flow is achieved by either a rotating agitator disposed within the reaction chamber, passing the flow through a spiral wound tube surrounding the UV lamp and defining a plurality of individual windings, the windings being formed with a D-shaded cross-section having a rectilinear or flat surface adjacent the UV lamp and a curved outer surface, passing the flow through a spiral wound tube surrounding the UV lamp and defining a plurality of individual windings having a rectangular cross section, or passing the fluid through a helical channel that spirals continuously around the UV lamp, whereas the helical channel approaches but does not engage the UV lamp and this defines a series of passages between each turn of the helical channel and the UV lamp.