You, Seung M.

Permanent URI for this collectionhttps://hdl.handle.net/10735.1/5616

Seung You joined the UT Dallas faculty in 2013 and is Professor of Mechanical Engineering. He also serves as an associate department head. Dr. You has extensive experience in thermal science. He has developed an experimental method to investigate nucleate boiling heat transfer mechanisms by measuring departing bubbles' frequency, size, and velocity. He also proposed the use of nanofluids and nanoporous structures for enhancing Critical Heat Flux, and invented a novel microporous coating that modifies the microstructure of surfaces resulting in a significant boiling and evaporation heat transfer improvement. His innovative micro/nano-scale thermal science technologies have contributed to thermal management in electronic components and energy-efficient sustainable design of thermal systems. His current research interests include:

3-D embedded thermal management using digital microfluidics thermal ground planes
Portable evaporative refrigerator for vaccine delivery
Enhancing multiple effect distillation (MED) by microporous coating
Superhydrophilic nanoporous coating process by nucleation
Convective heat transfer and fluid flow
Nucleate boiling heat transfer
Thermal management of high-heat-flux microelectronics
Heat transfer in thermal energy systems

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Flow Boiling Heat Transfer from Downward-Facing Thick Heater Block in an Inclined Channel with Plain and Microporous Coated Surfaces
(Pergamon-Elsevier Science Ltd, 2019-02) Song, Kiwon; Jun, Seongchul; You, Seung M.; Kim, Hwan Yeol; Kim, Moo Hwan; Revankar, Shripad T.; Jun, Seongchul; You, Seung M.
Flow boiling experiments were carried out with water on a 300 mm x 120 mm area and 85 mm thick downward-facing heated copper block at 1.4 bar pressure in a channel inclined 10° upwards with respect to horizontal. Heat transfer studies were conducted on a plain and microporous coated surfaces with heat fluxes up to 550 kW/m² for various flow rates and subcoolings. The results showed enhanced heat transfer coefficient on the microporous coated surface by a factor of two compared to the plain surface. Flow visualization study indicated that this heat transfer enhancement is due to enhanced microbubble generation on the microporous coated surface. Boiling curves were compared with the ones obtained from the small size heaters from previous researches. The local dryout or local critical heat flux was observed on the plain surface at around 450 kW/m². When heat flux was increased beyond the critical heat flux level, transition boiling occurred instead of direct excursion to the film boiling. Visualization studies of transition and film boiling regions were also carried out and were analyzed using transient temperature data.
Development of a Stable Boehmite Layer on Aluminum Surfaces for Improved Pool Boiling Heat Transfer in Water
(Elsevier Ltd, 2019-04-19) Godinez, J. C.; Fadda, D.; Lee, J.; You, S. M.; Godinez, Juan C.; Fadda, Dani; You, Seung M.
Oxidation layers that develop on an aluminum surface can cause changes in the surface wettability. When the aluminum surface is used as a heating surface, these changes result in inconsistencies in the nucleate boiling heat transfer performance and critical heat flux (CHF). Data is presented in this paper to define a “Boehmite treatment,” which is developed by placing the aluminum surface in boiling water for 180 min. The Boehmite treatment results in a favorable and stable oxidation layer. The layer is found to cause a reduction in the water contact angle from 55° to a sustainable range of 12–13°. Successive pool boiling tests, using this aluminum surface as a horizontal flat heater, are used to demonstrate the stability of the Boehmite layer. Comparisons are made against pool boiling results using a copper surface. The CHF for a Boehmite treated aluminum surface is 80% higher than that for a copper surface with similar surface roughness due to the highly wettable Boehmite layer on the aluminum surface. This work is performed using distilled saturated water at atmospheric pressure. ©2019 Elsevier Ltd
Droplet Velocity in an Electrowetting on Dielectric Digital Microfluidic Device
(MDPI AG) Nahar, M. M.; Nikapitiya, J. B.; You, Seung M.; Moon, H.; You, Seung M.
In many electrowetting on dielectric (EWOD) based microfluidics devices, droplet actuation speed is a crucial performance-controlling parameter. Our present study aims to characterize and study droplet speed in a typical EWOD device. First, a practical droplet speed measurement method has been methodically demonstrated and some related velocity terms have been introduced. Next, influence of electrode shape on droplet speed has been studied and a new design to enhance droplet speed has been proposed and experimentally demonstrated. Instead of using square shaped electrodes, rectangular electrodes with smaller widths are used to actuate droplets. Additionally, different schemes of activating electrodes are studied and compared for the same applied voltage. The experiments show that a particular scheme of activating the array of rectangular electrodes enhances the droplet speed up to 100% in comparison to the droplet speed in a conventional device with square shaped electrodes.
Effect of Subcooling on Pool Boiling of Water from Sintered Copper Microporous Coating at Different Orientations
(Hindawi Limited) Jun, Seongchul; Kim, Jinsub; You, Seung M.; Kim, H. Y.; 0000-0003-3235-0649 (Jun, S); Jun, Seongchul; Kim, Jinsub; You, Seung M.
The subcooling effect on pool boiling heat transfer using a copper microporous coating was experimentally studied in water for subcoolings of 10 K, 20 K, and 30 K at atmospheric pressure and compared to that of a plain copper surface. A higherature thermally conductive microporous coating (HTCMC) was made by sintering copper powder with an average particle size of 67 μm onto a 1 cm × 1 cm plain copper surface with a coating thickness of 300 μm. The HTCMC surface showed a two times higher critical heat flux (CHF), 2,000 kW/m2, and up to seven times higher nucleate boiling heat transfer (NBHT) coefficient, 350 kW/m2K, when compared with a plain copper surface at saturation. The results of the subcooling effect on pool boiling showed that the NBHT of both the HTCMC and the plain copper surface did not change much with subcooling. On the other hand, the CHF increased linearly with the degree of subcooling for both the HTCMC and the plain copper surface. The increase in the CHF was measured to be 60 kW/m2 for every degree of subcooling for both the HTCMC and the plain surface, so that the difference of the CHF between the HTCMC and the plain copper surface was maintained at 1,000 kW/m2 throughout the tested subcooling range. The CHFs for the HTCMC and the plain copper surface at 30 K subcooling were 3,820 kW/m2 and 2,820 kW/m2, respectively. The experimental results were compared with existing CHF correlations and appeared to match well with Zuber's formula for the plain surface. The combined effect of subcooling and orientation of the HTCMC on pool boiling heat transfer was studied as well.

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