Browsing by Author "Chu, Yu-Cheng"

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Enhancing Condensation Heat Transfer on Three-Dimensional Hybrid Surfaces
(2019-11-20)
Lo, Ching-Wen
;
Chu, Yu-Cheng
;
Yen, Ming-Han
;
Lu, Ming-Chang
;
機械工程學系
In recent years, micro/nanostructured surfaces have been applied to enhance condensation heat transfer. However, condensation heat transfer is greatly deteriorated by the flooding phenomenon that occurs at high subcooling temperatures. Here, we propose a three-dimensional (3D) hybrid surface to enhance the condensation at high subcooling temperatures. The 3D hybrid surface consisted of superhydrophobic (SHB) Si nanowire (SiNW) arrays and hydrophilic microchannels. The microchannels could confine the liquid-film thickness, and the liquid bridges formed on the 3D hybrid surfaces could be self-removed. Both of these characteristics prevent the surfaces from flooding. In addition, liquid droplets formed in the SiNW regions were dragged into the microchannels, which also improved the heat transfer. The heat transfer coefficient on the 3D hybrid surface could be enhanced over a large subcooling range. More remarkably, a record high heat flux of 655 +/- 10 kW.m(-2) was obtained on the 3D hybrid surface.
On Effective Design and Operating Conditions of Desiccant Dehumidification System
(2018-01-01)
Chu, Yu-Cheng
;
Weng, Ling-Chia
;
Tseng, Pen-Chang
;
Kang, Yu-Hao
;
Wang, Chi-Chuan
The present study investigates the effect of air flowrate on the adsorption systems both numerically and experimentally. Tests are performed with Zeolite 4A adsorbent. The size of test desiccant channel section is 10cm x 10cm x 10cm, and three test sections in series connections are used as the test section during adsorption and desorption. During adsorption, the inlet pressure is kept at 9bar while it is reduced to 1.16bar during desorption. The simulation is first validated with the experimental data. The simulation indicates though a higher airflow during adsorption can produce dry air quickly but may not be able to attain a prescribed very low dew point temperature. Yet lower airflow can dehumidify more moisture and attain much lower dew point but requires substantial time. For the required energy to generate the same dry air flow volume in cyclic operation, it was obvious that a lower flowrate like 150 standard liter per minutes (SLPM) is about 4% lower than that of a higher flowrate of 400 SLPM. For effective regeneration during desorption, a non-uniform heating provided at the first section is proved to be much effective than the uniform heating. It is found that the desiccant loading for only heating at the first section outperforms other arrangements, giving 10% lower desiccant loading than the uniform heating.