Abstract
Vapor condensation is routinely used as an effective means of transferring heat or separating fluids. Dropwise condensation, where discrete droplets form on the condenser surface, offers a potential improvement in heat transfer of up to an order of magnitude compared to filmwise condensation, where a liquid film covers the surface. Low surface tension fluid condensates such as hydrocarbons pose a unique challenge since typical hydrophobic condenser coatings used to promote dropwise condensation of water often do not repel fluids with lower surface tensions. Recent work has shown that lubricant infused surfaces (LIS) can promote droplet formation of hydrocarbons. In this work, we confirm the effectiveness of LIS in promoting dropwise condensation by providing experimental measurements of heat transfer performance during hydrocarbon condensation on a LIS, which enhances heat transfer by ≈450% compared to an uncoated surface. We also explored improvement through removal of noncondensable gases and highlighted a failure mechanism whereby shedding droplets depleted the lubricant over time. Enhanced condensation heat transfer for low surface tension fluids on LIS presents the opportunity for significant energy savings in natural gas processing as well as improvements in thermal management, heating and cooling, and power generation.
Highlights
In the present work, we quantitatively confirmed the effectiveness of lubricant infused surfaces (LIS) in promoting dropwise condensation
To create the CuO nanostructures, a bare copper tube cleaned as described for the hydrophilic samples above was immersed into a hot (96 ± 3 °C) alkaline solution composed of NaClO2, NaOH, Na3PO412H2O, and DI water (3.75 : 5 : 10 : 100 wt.%)[27,33]
The condensation heat transfer coefficient, hc, and subcooling, ∆T = Tv − Tw, were calculated from the thermal resistance network shown in Fig. 1(c), where the thermal resistances of the internal flow and conduction through the tube wall are known
Summary
The heat transfer performance was determined during condensation of the hydrocarbon toluene (γ ≈ 28 mN/m) on bare and hydrophobic flat surfaces in the filmwise mode and on LIS-coated tubes in the dropwise mode at a range of supersaturations typical for natural gas processing applications. From these results, the heat transfer coefficient for hydrocarbon condensation on LIS was obtained experimentally. The ≈450% experimentally observed improvement in heat transfer for low surface tension fluids condensing on LIS presents the opportunity for significant energy savings in natural gas processing and in applications such as thermal management, heating and cooling, and power generation.
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