Condensation heat transfer in a mixed flow regime

Experiments were performed on condensing steam within a horizontal pipe to determine a valid criterion for the flow transition from the initial annular regime to the final stratified regime. It was established that the stress ratio, F = tausub(w)/plgdelta, determined the flow regime. Thus: F > 29 annular, 29 >= F >= 5 transition, F < 5 stratified, describes the relevant flow regime. On this basis, a Nusselt number correlation is proposed: Nsub(tr) = Nsub(an) + (Nsub(an)-Nsub(str))(F-29)/24. A Nusselt number computed on the basis of this correlation exhibits errors of similar magnitude to established methods for annular and stratified flow condensation. (author)