Swirl flow with twisted tape

B23. Bundy, R. D., Gambill, W. R., and Wansborough, R. W., Heat transfer, burn-out and pressure drop for water in swirl flow through tubes with internal twisted tapes, Natl. Heat Transfer Conf, 4th, A.I.Ch.E., August 1960. 

The enhancement of heat transfer inside a circular duct is often achieved by inserting a thin, metal tape in such a way that the tape is twisted about its longitudinal axis, as indicated in Fig. 5.47. Swirl flow is created in this manner. The width of the tape is usually the same as the internal diameter of the duct. The tape twist ratio XL is defined as H/d. When XL approaches infinity, the circular duct with the twisted tape becomes two semicircular straight ducts separated by the tape. 

Swirl-flow devices include a number of geometric arrangements or tube inserts for forced flow that create rotating and/or secondary flow inlet vortex generators, twisted-tape inserts, and axial-core inserts with a screw-type winding. 

W. R. Gambill, R. D. Bundy, and R. W. Wansbrough, Heat Transfer, Burnout, and Pressure Drop for Water in Swirl Flow Tubes With Internal Twisted Tapes, Chem. Eng. Prog. Symp. Ser. (57/32) 127-137,1961. 

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