TUBE OF A HEAT EXCHANGER AND PROCEDURE OF MANUFACTURING OF A HELIX FOR SUCH A TUBE
A heat exchanger tube with elliptical or oval cross-section in a stream of external gas, esp. air, has the internally flowing liq., esp. water, turbidified by a helically bent strip varying in width so that its edges are in contact with the tube walls along both major and minor axes of the cross-section. The pitch of the helix depends on difference between these axes. Before twisting to helical form, e.g. by rollers, the initial strip is cut from flat metal or plastic stock by forming wavy sepn. lines from adjacent strips along both edges, with the wave shapes in conformity to avoid forming cutting scrap. Twisting may also be provided on leaving an extrusion nozzle, or by multiple punches.