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Enhancing dropwise condensation through active transport of drops using electrowetting

Hoek, H.J. (2020) Enhancing dropwise condensation through active transport of drops using electrowetting.

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Abstract:Dropwise condensation is used for heat transfer applications, including industrial coolers and water harvesting. Most research aimed on increasing heat transfer is focussed on passive approaches like surface engineering. More recently the active approach of electrowetting has been used to enhance heat transfer. Motivated by these studies, we use electrowetting on functionalized substrates to actively trans- port condensate drops off the surface. In this research we explain the workings of active transport and investigate its effect on the heat transfer. By experimentally measuring the condensation rate as well as looking at indirect signs of improved heat transfer on the breath figure, we show that active transport does improve heat transfer. The electrode design used in this study for active transport is not optimized. We introduce a force balance model that we use to predict the critical radius, and thus efficiency of thousands of different electrode designs for active transport. This model can be used to further enhance active transport. In this research we present a new experimental setup designed and built to experimentally determine the condensation rate. This modular setup we use to de- termine the condensation rates for different types of functionalized substrates. We show that, contrary to what was published before, zigzag interdigitated electrodes do not enhance but actually decrease the condensation rate due to pinning at the electrical traps. Interdigitated electrodes show a slight increase in condensation rate, but not as much as with active transport. We investigate several methods to determine the condensation rate, both exper- imentally based water collection methods and image analysis based techniques. We show that even though most techniques show comparable condensation rates, only one method proved to be accurate enough to distinguish differences between different types of substrates. Even though dropwise condensation shows superior heat transfer over filmwise condensation, it is barely used in (industrial) applications due to surface degrada- tion. We study surface degradation during dropwise condensation with electrowet- ting and use Liquid Infused surfaces in an attempt to create durable surfaces as a first step towards applications of dropwise condensation with electrowetting.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:33 physics
Programme:Applied Physics MSc (60436)
Link to this item:http://purl.utwente.nl/essays/80626
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