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DROPWISE CONDENSATION OF STEAM ON HARD COATED SURFACES

Alfred Leipertz
Lehrstuhl fur Technische Thermodynamik (LTT), Universitat Erlangen-Nurnberg,Am Weichselgarten 8, D-91058 Erlangen, Germany; ESYTEC Energie- und Systemtechnik GmbH Erlangen, Am Weichselgarten 6, D-91058 Erlangen, Germany

Gerd Koch
Lehrstuhl fur Technische Thermodynamik (LTT) Universitat Erlangen-Niirnberg Am Weichselgarten 8 D-91058 Erlangen Germany

Abstract

At atmospheric pressure dropwise condensation (DWC) has been studied on the surfaces of different hard coated copper discs of 60 mm diameter and copper plates of size 200 mm × 60 mm. The different coating systems were produced by using different modifying elements (F, Si, Si/O) during the plasma-enhanced chemical vapor deposition coating process generating for each system different surface energies which have been measured by the contact angle of equilibrium 0 between the condensing fluid and the surface (θ between 65° and 100°). Stable and well reproducible measurements of the DWC heat transfer coefficient as function of the surface subcooling temperature have been performed. Additionally results are presented on the influence of the orientation of the surface (surface inclination angle), of the disc base material (besides copper also aluminium, brass and steel) and of incomplete surface coatings which gives information on the operation conditions if the coating would not be mechanically stable enough. The investigated coating system, however, promise long operation times with very stable DWC conditions and thus an application in real technical condensation systems.

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