ARTICLE:

• DROPWISE CONDENSATION ON PLASMA-ION-IMPLANTED SMALL HORIZONTAL TUBE BUNDLES  download article

A. B. Kananeh
Universität Erlangen-Nürnberg, Erlangen, Germany

A. P. Froba
Universität Erlangen-Nürnberg, Erlangen, Germany

Alfred Leipertz
Lehrstuhl für Technische Thermodynamik (LTT), Universität Erlangen-Nürnberg, Am Weichselgarten 8, D-91058 Erlangen, Germany

ABSTRACT

Stable dropwise condensation of saturated steam was achieved on stainless steel tube bundles implanted with nitrogen ions by plasma-ion-implantation. For the investigation of the efficiency of plasma-ion-implantation regarding the condensation process a condenser was constructed in order to measure the heat flow Q and the overall heat transfer coefficient H_o for the condensation of steam on the outside surface of the tube bundles. For a horizontal tube bundle of nine tubes implanted with an ion dose of 10¹⁶ N·cm⁻², the enhancement ratio ε_Ho, which represents the ratio of the overall heat transfer coefficient of the implanted tube bundle to that of the unimplanted one, was found to be 1.12 for a Re value of 21231. The heat flux and the overall heat transfer coefficient were increased by the increase in the steam pressure. The maximum H_o which could be achieved was 2.22 kW·m⁻²·K⁻¹ at a steam pressure of 2000 mbar and a Re value of 22656. At these conditions, more condensate was formed on the upper tube rows and the lowest row received more condensate which converted the condensation to at those tubes to filmwise condensation.

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CSN-03 pages

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