scholarly journals Multiscale Micro/Nanostructured Heat Spreaders for Thermal Management of Power Electronics

2021 ◽  
Author(s):  
Huihe Qiu ◽  
Yinchuang Yang
Keyword(s):  
Thermal Performance ◽  
Superhydrophobic Surface ◽  
Evaporation Rate ◽  
Nucleate Boiling ◽  
Nanostructured Surface ◽  
Vapor Chamber ◽  
Nanostructured Surfaces ◽  
Patterned Surface ◽  
Heat Spreaders ◽  
Surface Modification Techniques

In this chapter, we describe surface modification techniques for enhancing heat/mass transfer and evaporation on heated surfaces. The effect of asymmetrical structure in designing a vapor chamber, patterned with multiscale micro/nanostructured surfaces will be introduced. The wettability patterned surface and its mechanism for improving the evaporation rate of a droplet and the thermal performance of nucleate boiling are discussed. An ultrathin vapor chamber based on a wettability patterned evaporator is introduced as a case for the application of the wettability pattern. Besides, modifying the surface with nanostructure to form a multiscale micro/nanostructured surface or superhydrophobic surface also enhances the phase change. Several types of heat spreaders are proposed to investigate the effects of multiscale micro/nanostructured surface and nanostructured superhydrophobic condenser on the thermal performance of the heat spreaders, respectively. The effects of multiscale micro/nanostructured evaporator surfaces with wettability patterns will be analyzed and experimental data will be presented.

Comparison of Droplet Evaporation and Nucleate Boiling Mechanisms on Nanoporous Superhydrophilic Surfaces

2019 ◽  
Author(s):  
Samuel Cabrera ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Droplet Evaporation ◽  
Transfer Performance ◽  
Nanostructured Surface ◽  
Nanostructured Surfaces ◽  
Droplet Vaporization

Abstract Recent studies have indicated that at slightly superheated surface temperatures, droplet evaporation on a nanoporous superhydrophilic surface exhibits onset of nucleation and nucleate boiling effects similar to pool boiling processes. This paper discusses water droplet evaporation experiments and pool boiling experiments conducted on nanostructured surfaces of a 45° downward facing pyramid copper and aluminum substrate. The nanostructured surfaces were used to conduct both droplet evaporation experiments and pool boiling experiments and thus allow direct comparison of the underlying heat transfer performance and mechanisms for these two different processes. The four surfaces tested were the following: bare copper surface, nanostructured surface on copper, bare aluminum surface, and nanostructured surface on aluminum. Mean heat flux values at varying superheats were obtained through temperature and time measurements. To better understand the heat performance of each surface, the wetting and wicking characteristics of each surface were also tested. Experimental results indicate that many of the mechanisms associated with pool boiling may also play a role in droplet vaporization, and their presence can produce levels of heat transfer performance comparable to, or even higher than, that observed in pool boiling at a comparable wall superheat. The results demonstrate that the nanostructured surface affects onset of nucleate boiling and maximum heat flux in both droplet vaporization and nucleate boiling on these surfaces. The implications of these results for strategies to enhance spray cooling and pool boiling are also discussed.

Thermal performance of thin loop-type vapor chamber

2015 ◽  
Vol 61 ◽  
pp. 130-143 ◽  
Author(s):  
Shyy Woei Chang ◽  
Kuei Feng Chiang ◽  
Tsung Han Lee
Keyword(s):  
Thermal Performance ◽  
Vapor Chamber

scholarly journals Electrochemical Surface Biofunctionalization of Titanium through Growth of TiO2 Nanotubes and Deposition of Zn Doped Hydroxyapatite

Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 69
Author(s):  
Diana Maria Vranceanu ◽  
Elena Ungureanu ◽  
Ionut Cornel Ionescu ◽  
Anca Constantina Parau ◽  
Adrian Emil Kiss ◽  
...  
Keyword(s):  
Anatase Phase ◽  
Pure Titanium ◽  
Chemical Properties ◽  
Secondary Phase ◽  
Xrd Analysis ◽  
Electrochemical Treatment ◽  
Titania Nanotubes ◽  
Nanostructured Surface ◽  
Nanostructured Surfaces ◽  
Zn Content

The current research aim is to biofunctionalize pure titanium (Ti, grade IV) substrate with titania nanotubes and Zn doped hydroxyapatite-based coatings by applying a duplex electrochemical treatment, and to evaluate the influence of Zn content on the physico-chemical properties of hydroxyapatite (HAp). The obtained nanostructured surfaces were covered with HAp-based coatings doped with Zn in different concentrations by electrochemical deposition in pulsed galvanostatic mode. The obtained surfaces were characterized in terms of morphology, elemental and phasic composition, chemical bonds, roughness, and adhesion. The nanostructured surface consisted of titania nanotubes (NT), aligned, vertically oriented, and hollow, with an inner diameter of ~70 nm. X-Ray Diffraction (XRD) analysis showed that the nanostructured surface consists of an anatase phase and some rutile peaks as a secondary phase. The morphology of all coatings consisted of ribbon like-crystals, and by increasing the Zn content the coating became denser due to the decrement of the crystals’ dimensions. The elemental and phase compositions evidenced that HAp was successfully doped with Zn through the pulsed galvanostatic method on the Ti nanostructured surfaces. Fourier Transform Infrared spectroscopy (FTIR) and XRD analysis confirmed the presence of HAp in all coatings, while the adhesion test showed that the addition of a high quantity leads to some delamination. Based on the obtained results, it can be said that the addition of Zn enhances the properties of HAp, and through proper experimental design, the concentration of Zn can be modulated to achieve coatings with tunable features.

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