Composite Structured Surfaces for Durable Dropwise Condensation

Chang, Ho Chan; Rajagopal, Manjunath C.; Hoque, Muhammad Jahidul; Oh, Junho; Li, Longnan; Li, Jiaqi; Zhao, Hanyang; Kuntumalla, Gowtham; Sundar, Sreenath; Meng, Yuquan; Shao, Chenhui; Ferreira, Placid M.; Salapaka, Srinivasa M.; Sinha, Sanjiv; Miljkovic, Nenad

doi:10.1016/j.ijheatmasstransfer.2020.119890

Cited by 26 publications

(8 citation statements)

References 75 publications

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“…However, thicker structures increase the conduction thermal resistance between the heated substrate and structure surface exposed to the liquid ( 12 , 17 ), thus reducing evaporation within structures and lengthening τ CE . Furthermore, even if the thickness and porosity of the structures are identical, the effective cross-plane thermal resistance is notably affected by structure features, such as pore diameters, tortuosity, interconnectedness, and pore neck diameter, thus affecting the experimentally observed evaporation time ( 47 ). Therefore, the evaporated volume flux does not increase monotonically, indicating the existence of an upper limit for CHF enhancement using the model developed here.…”

Section: Discussionmentioning

confidence: 99%

Liquid film–induced critical heat flux enhancement on structured surfaces

Kang

Rabbi

et al. 2021

Sci. Adv.

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Enhancing critical heat flux (CHF) during boiling with structured surfaces has received much attention because of its important implications for two-phase flow. The role of surface structures on bubble evolution and CHF enhancement remains unclear because of the lack of direct visualization of the liquid- and solid-vapor interfaces. Here, we use high-magnification in-liquid endoscopy to directly probe bubble behavior during boiling. We report the previously unidentified coexistence of two distinct three-phase contact lines underneath growing bubbles on structured surfaces, resulting in retention of a thin liquid film within the structures between the two contact lines due to their disparate advancing velocities. This finding sheds light on a previously unidentified mechanism governing bubble evolution on structured surfaces, which has notable implications for a variety of real systems using bubble formation, such as thermal management, microfluidics, and electrochemical reactors.

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Section: Discussionmentioning

confidence: 99%

Liquid film–induced critical heat flux enhancement on structured surfaces

Kang

Rabbi

et al. 2021

Sci. Adv.

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“…An effective thermal conductivity, , approximates the local thermal resistances such that under a known amount of steady heat ( ), the temperature change (Δ ) can be predicted using a single thermal property, . The effective thermal conductivity is a function of the type of heat input (line, surface, or volumetric) [58], and the location of the temperature measurement. Typically, the measured temperatures can be volume averaged ( − ), surface average ( − ), volume maximum ( − ), or surface maximum ( − ).…”

Section: Revisiting the Effective Thermal Conductivity Approximationmentioning

confidence: 99%

Cellular Thermometry Considerations for Probing Biochemical Pathways

Rajagopal

Sinha

2021

Cell Biochem Biophys

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Temperature is a fundamental thermodynamic property that can serve as a probe of biochemical reactions. Extracellular thermometry has previously been used to probe cancer metabolism and thermoregulation, with measured temperature changes of ~1-2 K in tissues, consistent with theoretical predictions. In contrast, previous intracellular thermometry studies remain disputed due to reports of >1 K intracellular temperature rises over 5 min or more that are inconsistent with theory. Thus, the origins of such anomalous temperature rises remain unclear. An improved quantitative understanding of intracellular thermometry is necessary to provide a clearer perspective for future measurements. Here, we develop a generalizable framework for modeling cellular heat diffusion over a range of subcellular-to-tissue length scales. Our model shows that local intracellular temperature changes reach measurable limits (> 0.1 K) only when exogenously stimulated. On the other hand, extracellular temperatures can be measurable (> 0.1 K) in tissues even from endogenous biochemical pathways. Using these insights, we provide a comprehensive approach to choosing an appropriate cellular thermometry technique by analyzing thermogenic reactions of different heat rates and time constants across length scales ranging from sub-cellular to tissues. Our work provides clarity on cellular heat diffusion modeling and on the required thermometry approach for probing thermogenic biochemical pathways.

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“…The value range for the thermal conductivity coefficients was determined based on potential coating materials (e.g. approximately 0.2 W m -1 K -1 for PTFE and 10 W m -1 K -1 for composite coatings [43]).…”

Section: Definition Of Input Parameter Spacementioning

confidence: 99%

Global sensitivity analysis of a pure steam dropwise condensation heat transfer model

Sablowski¹,

Unz²,

Beckmann³

2020

Preprint

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In recent years, established heat transfer models for dropwise condensation (DWC) have been refined to consider the influence of wetting behavior, surface structure and nucleation dynamics on the heat transfer rate in more detail. Despite these efforts to develop more sophisticated models, uncertainties of the model parameters still lead to a high variation of the calculated heat transfer rate. In this study, we apply quantitative sensitivity analysis to a pure steam DWC heat transfer model in order to attribute the variation of the model result to its input parameters. Four scenarios with different variations of the model parameters are discussed and sensitivity coefficients for each parameter are calculated. Our results show that the contact angle and the nucleation site density have the greatest influence on the model result if no additional coating layer is considered. The influence of the nucleation site density is mainly due to the large uncertainties associated with this parameter. In scenarios with an additional coating layer, the heat flux is mainly governed by the thickness of the coating layer, underlining the need for thin conformal coatings to effectively promote DWC. Furthermore, trends within the heat transfer model are discussed and beneficial conditions for a high heat flux are identified for each scenario. The results underline that the wetting properties of functional surfaces should be tailored towards medium contact angles in the range of 70° to 130° and low contact angle hystereses below 10° to achieve high heat flux DWC.

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Composite Structured Surfaces for Durable Dropwise Condensation

Cited by 26 publications

References 75 publications

Liquid film–induced critical heat flux enhancement on structured surfaces

Liquid film–induced critical heat flux enhancement on structured surfaces

Cellular Thermometry Considerations for Probing Biochemical Pathways

Global sensitivity analysis of a pure steam dropwise condensation heat transfer model

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