Experimental Investigation of Large-Scale Vertically Coated Tubes for Enhanced Air–Steam Condensation Heat Transfer

Zengqiao Chen, Keyuan Zhang () and Naihua Wang ()
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Zengqiao Chen: School of Energy and Power Engineering, Shandong University, Jinan 250061, China
Keyuan Zhang: Institute of Thermal Science and Technology, Shandong University, Jinan 250061, China
Naihua Wang: Institute of Thermal Science and Technology, Shandong University, Jinan 250061, China

Energies, 2024, vol. 17, issue 18, 1-16

Abstract: Non-condensable gas plays a significant role in steam condensation, primarily by reducing heat transfer efficiency. Enhanced condensation heat transfer in the presence of non-condensable gas is crucial for improving thermal efficiency, reducing energy consumption, and lowering costs. However, experimental studies on applying coatings to enhance condensation heat transfer in large-scale vertical outer tubes with non-condensable gas are scarce. This study investigates the condensation heat transfer performance of vertical stainless steel- and brass-coated tubes compared to their bare counterparts at different air concentrations (0.4, 0.3, 0.15, and 0.08). All tubes have an outer diameter of 19 mm and an effective length of 1080 mm. Visualizations reveal that condensate flow rates as high as 0.5 m/s on bare tubes cause significant disturbances to the diffusion layer. At various air concentrations, the maximum condensation heat transfer coefficient of the coated stainless steel tube exhibited increases of 22.2%, 11.9%, 4.2%, and 19.6% compared with the uncoated stainless steel tube. Similarly, the maximum condensation heat transfer coefficient for the coated brass tube showed significant increases of 58.9%, 53.5%, 68.0%, and 70.7% compared with the uncoated brass tube. Notably, the enhancement effect on heat transfer performance is more pronounced when the same type of modified surface is applied to the brass tube compared with the stainless steel tube.

Keywords: condensation heat transfer; non-condensable gas; vertical tube; surface modification; condensate dynamics (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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