scholarly journals A Interfacial Dynamics and Heat Transfer of Microdroplets on Biphilic Micro/Nanostructured Surfaces

2019 ◽  
Author(s):  
Huihe Qiu
Keyword(s):  
Heat Transfer ◽  
Interfacial Dynamics ◽  
Nanostructured Surfaces

Phenomenon and Mechanism of Spray Cooling on Nanowire Arrayed and Hybrid Micro/Nanostructured Surfaces

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Jian-nan Chen ◽  
Rui-na Xu ◽  
Zhen Zhang ◽  
Xue Chen ◽  
Xiao-long Ouyang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
High Speed ◽  
Spray Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Enhancement ◽  
Nanostructured Surfaces ◽  
New Energy ◽  
Dry Out

Enhancing spray cooling with surface structures is a common, effective approach for high heat flux thermal management to guarantee the reliability of many high-power, high-speed electronics and to improve the efficiency of new energy systems. However, the fundamental heat transfer enhancement mechanisms are not well understood especially for nanostructures. Here, we fabricated six groups of nanowire arrayed surfaces with various structures and sizes that show for the first time how these nanostructures enhance the spray cooling by improving the surface wettability and the liquid transport to quickly rewet the surface and avoid dry out. These insights into the nanostructure spray cooling heat transfer enhancement mechanisms are combined with microstructure heat transfer mechanism in integrated microstructure and nanostructure hybrid surface that further enhances the spray cooling heat transfer.

scholarly journals PREFACE: INTERFACIAL DYNAMICS AND HEAT TRANSFER

2017 ◽  
Vol 5 (4) ◽  
pp. v
Author(s):  
Hitoshi Asano ◽  
BoFeng Bai ◽  
Irina Graur Martin ◽  
Hang Guo
Keyword(s):  
Heat Transfer ◽  
Interfacial Dynamics

Heat Transfer Enhancement Effect of Nanostructured Surface Made of Carbon Nanotube on SiC Ceramics

2013 ◽  
Author(s):  
Hiroki Noguchi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Enhancement ◽  
Chemical Vapor ◽  
Enhancement Effect ◽  
Nanostructured Surface ◽  
Transfer Enhancement ◽  
Energy Agency ◽  
Nanostructured Surfaces ◽  
Surface Decomposition

The Japan Atomic Energy Agency (JAEA) has been conducting research and development on the thermo-chemical iodine–sulfur (IS) process, which is one of the most attractive water-splitting hydrogen production methods using the nuclear heat of a high-temperature gas-cooled reactor (HTGR). In researching this IS process, a silicon carbide (SiC) heat exchanger with good corrosion resistance was used in a corrosive situation in boiling sulfuric acid. With the aim of enhancing heat transfer in the SiC heat exchanger, a nanostructured surface made of carbon nanotubes (CNTs) was produced on a SiC substrate by surface decomposition. Two types of SiC, one produced by pressureless sintering (PLS-SiC) and one by chemical vapor deposition (CVD-SiC), were used as substrates. CNTs formed by the surface decomposition of SiC can vary depending on the crystal structure of the substrates. Additionally, in order to investigate surface wettability, nanostructured surfaces on the CVD-SiC with hydrophilicity and hydrophobicity were produced. The effects of heat transfer enhancement by the nanostructured surfaces were evaluated by a convective heat transfer test using de-ionized water. The nanostructured surface on the CVD-SiC with hydrophilicity was the only surface that showed any heat transfer enhancement. However, this enhancement was much smaller than those previously reported. The experiment showed that the small size of the nanopores influenced the heat transfer enhancement and that the wettability of the nanostructured surface was related to heat transfer enhancement.

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.

Pool Boiling Heat Transfer of N-Pentane and Acetone on Nanostructured Surfaces by Electrophoretic Deposition

2018 ◽  
Author(s):  
Zan Wu ◽  
Anh Duc Pham ◽  
Zhen Cao ◽  
Cathrine Alber ◽  
Peter Falkman ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Electrophoretic Deposition ◽  
Boiling Heat Transfer ◽  
Smooth Surface ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Working Fluids ◽  
Pool Boiling Heat Transfer ◽  
Nanostructured Surfaces ◽  
Coated Surfaces

This work aims to investigate pool boiling heat transfer enhancement by using nanostructured surfaces. Two types of nanostructured surfaces were employed, gold nanoparticle-coated surfaces and alumina nanoparticle-coated surfaces. The nanostructured surfaces were fabricated by an electrophoretic deposition technique, depositing nanoparticles in a nanofluid onto smooth copper surfaces under an electric field. N-pentane and acetone were tested as working fluids. Compared to the smooth surface, the pool boiling heat transfer coefficient has been increased by 80% for n-pentane and acetone. Possible mechanisms for the enhancement in heat transfer are qualitatively provided. The increase in active nucleation site density due to multiple micro/nanopores on nanoparticle-coated surfaces is likely the main contributor. The critical heat flux on nanostructured surfaces are approximately the same as that on the smooth surface because both smooth and modified surfaces show similar wickability for the two working fluids.

scholarly journals Review of Micro–Nanoscale Surface Coatings Application for Sustaining Dropwise Condensation

Coatings ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 117 ◽  
Author(s):  
Shoukat Alim Khan ◽  
Furqan Tahir ◽  
Ahmer Ali Bozdar Baloch ◽  
Muammer Koc
Keyword(s):  
Heat Transfer ◽  
Noble Metals ◽  
Power Plants ◽  
Contact Angle Hysteresis ◽  
Surface Hydrophobicity ◽  
Future Research ◽  
Dropwise Condensation ◽  
Nanostructured Surfaces ◽  
Research Guidelines ◽  
Coating Methods

Condensation occurs in most of the heat transfer processes, ranging from cooling of electronics to heat rejection in power plants. Therefore, any improvement in condensation processes will be reflected in the minimization of global energy consumption, reduction in environmental burdens, and development of sustainable systems. The overall heat transfer coefficient of dropwise condensation (DWC) is higher by several times compared to filmwise condensation (FWC), which is the normal mode in industrial condensers. Thus, it is of utmost importance to obtain sustained DWC for better performance. Stability of DWC depends on surface hydrophobicity, surface free energy, condensate liquid surface tension, contact angle hysteresis, and droplet removal. The required properties for DWC may be achieved by micro–nanoscale surface modification. In this survey, micro–nanoscale coatings such as noble metals, ion implantation, rare earth oxides, lubricant-infused surfaces, polymers, nanostructured surfaces, carbon nanotubes, graphene, and porous coatings have been reviewed and discussed. The surface coating methods, applications, and enhancement potential have been compared with respect to the heat transfer ability, durability, and efficiency. Furthermore, limitations and prevailing challenges for condensation enhancement applications have been consolidated to provide future research guidelines.

A Systematic Study of Pool Boiling Heat Transfer on Multiscale Structured Surfaces

2014 ◽  
Author(s):  
Russell P. Rioux ◽  
Eric C. Nolan ◽  
Calvin H. Li
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Multiple Scales ◽  
Pool Boiling ◽  
Theoretical Models ◽  
Sintering Process ◽  
Structured Surfaces ◽  
Pool Boiling Heat Transfer ◽  
Nanostructured Surfaces ◽  
Modified Surfaces

A study has been conducted to examine the effects of macroscale, microscale, and nanoscale surface modifications in water pool boiling heat transfer and to determine the effects of combining the multiple scales. Nanostructured surfaces were created by acid etching, while microscale and macroscale surfaces were manufactured through a sintering process. Six structures were studied as individual and/or collectively integrated surfaces: polished plain, flat nanostructured, flat porous, modulated porous, nanostructured flat porous, and nanostructured modulated porous. Boiling performance was measured in terms of critical heat flux (CHF) and heat transfer coefficient (HTC). Both HTC and CHF have been greatly improved on all modified surfaces compared to the polished baseline. The CHF and HTC of the hybrid multiscale modulated porous surface have achieved the most significant improvements of 350% and 200% over the polished plain surface, respectively. Nanoscale, microscale, and macroscale integrated surfaces have been proven to have the most significant improvements on HTC and CHF. Experimental results were compared to the predictions of a variety of theoretical models with an attempt to evaluate both microscale and nanoscale models. It was concluded that models for both microscale and nanoscale structured surfaces needed to be further developed to be able to have good quantitative predictions of CHFs on structured surfaces.

Nucleate Boiling on Biotemplated Nanostructured Surfaces

2012 ◽  
Author(s):  
Md. Mahamudur Rahman ◽  
Stephen M. King ◽  
Emre Olceroglu ◽  
Matthew McCarthy
Keyword(s):  
Heat Transfer ◽  
Self Assembly ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Pool Boiling Heat Transfer ◽  
Nanostructured Surfaces ◽  
Transfer Capability ◽  
Good Agreement

The fabrication and characterization of biotemplated nanostructured surfaces for enhanced pool boiling heat transfer is reported. By introducing micro/nano-porosity and surface roughness at the liquid-vapor interface, significant enhancement in surface heat transfer capability can be achieved during nucleate boiling. This work uses the self-assembly and mineralization of the Tobacco mosaic virus (TMV) to create superhydrophilic (∼9°), superhydrophobic (∼163°), and mixed hydrophilic-hydrophobic (∼70°) surfaces to investigate the effects of surface wettability and heterogeneity on boiling heat transfer performance. Pool boiling results showing CHF and HTC values for nickel-coated TMV, Teflon-coated TMV, mixed nickel + Teflon coated TMV, flat silicon, and flat Teflon are reported. The mixed surfaces demonstrate a CHF enhancement of ∼ 70% compared to flat silicon and ∼140% compared to flat Teflon. The results are in good agreement with the literature and will guide the design of optimized surfaces for further enhancement. This work demonstrates the feasibility of enhancing pool boiling heat transfer using TMV based nanostructured coatings.

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