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Interfacial Phenomena and Heat Transfer
ESCI SJR: 0.258 SNIP: 0.574 CiteScore™: 0.8

ISSN Druckformat: 2169-2785
ISSN Online: 2167-857X

Interfacial Phenomena and Heat Transfer

DOI: 10.1615/InterfacPhenomHeatTransfer.2015012042
pages 85-113

DROPWISE CONDENSATION OF METAL VAPORS UNDERNEATH INCLINED SUBSTRATES

Basant Singh Sikarwar
Department of Mechanical Engineering, Amity University Uttar Pradesh, Noida, U.P., India
Sameer Khandekar
Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur (UP) 208016, India
Krishnamurthy Muralidhar
Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India

ABSTRAKT

Dropwise condensation of metallic vapor underneath inclined textured substrates is encountered in specialized applications such as power generation and materials processing. Its long-term sustainability poses several challenges. Quantification of substrate wear rate requires knowledge of local wall shear stress and local heat fluxes. In this context, we propose a mathematical model and validate its predictions for condensation of water vapor. The model computes drop size until instability, fluid flow and heat transfer inside the drop, wall shear stresses, and local and average transport coefficients. The extension of the model to liquid metals is presented. The liquid metals considered are mercury, potassium, and sodium. Analysis at the drop scale shows that the skin friction coefficient is inversely proportional to the Reynolds number and decreases with increasing contact angle. The Nusselt number is practically independent of the Reynolds number, but increases with contact angle. Drop sizes at criticality of fall-off and slide-off underneath horizontal and inclined surfaces are determined from gravitational stability. The condensation model is simulated until a dynamic steady state is reached. Instantaneous condensation patterns of metal vapor underneath horizontal and inclined surfaces are compared with those of water. The model shows good agreement with mercury experiments. In metals the minimum drop size is larger whereas the critical drop size and cycle time of condensation are smaller compared with those for water. For this reason, we obtain a higher time-averaged wall shear stress and heat transfer coefficient. For a horizontal surface, condensation properties depend on the properties of the three fluids. This distinction is markedly smaller on a vertical surface.


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