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 = solτwρLgδ, 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: Ntr = Nan + F−2924(Nan−str). A Nusselt number computed on the basis of this correlation exhibits errors of similar magnitude to established methods for annular and stratified flow condensation.