Inundation effect, decrease of condensation heat transfer coefficient (CHTC) induced by both falling condensate from the neighboring tubes above and condensing condensate form the vapor, significantly affects the CHTC of tube bundles composed of smooth and enhanced tubes. This paper experimentally studied the inundation effect of smooth tube and three kinds of enhanced tubes (3D-A, 3D-B and 2D-A), put forward a scheme to eliminate the inundation effect caused by falling condensate and check it by experimental investigation. HFC134a and HFC245fa (substitutes of CFC12 and CFC11, respectively) were condensed in the experiment. Nominal diameter and active length of each test tube is 19.05mm and 500mm, respectively. Diversion ducts were fixed into the test tube bundle to eliminate tube row effect (part of the inundation effect caused by the falling condensate). Drainage strip was equipped on the test tubes to abate the inundation effect induced by condensed condensate. The (These) experimental results show: (1) Inundation effect of HFC 134a and HFC245fa on smooth tube bundle is not as severe as that predicted by Kern’s model. (2) 3D-B enhanced tube is dramatically affected by the inundation effect caused by falling condensate; (3) The equipped diversion ducts can eliminate tube row effect and improve the CHTC of tube bundles composed of smooth and 3D-B tubes. (4) The equipped drainage strip can further enhance the CHTC of 3D-A and 2D-A tubes in the tube bundle.

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