The Influence of Twisted Tapes in Subcritical, Once-Through Vapor Generators in Counter flow

The swirl flow of Freon 12 in a tubular heat exchanger, indirectly heated by forced convection of water in an annular gap, is studied. Two identical situations are compared, with and without a twisted tape, to deduce the influence of the swirl flow in the particularly interesting boundary condition of indirect heating by another fluid (and not simply of uniform Joule heating). The heat transfer is greatly increased by the swirl flow, up to a factor of two at the burnout or dryout point.