Evaporation of Silver-Graphene Hybrid Nanofluid Droplet on its Nanostructured Residue and Plain Copper Surfaces at Elevated Temperatures

2020 ◽  
Author(s):  
Farooq Riaz Siddiqui ◽  
Chi Yan Tso ◽  
Sau Chung Fu ◽  
Huihe Qiu ◽  
Christopher Yu Hang Chao
Keyword(s):  
Substrate Temperature ◽  
Evaporation Rate ◽  
Elevated Temperatures ◽  
Droplet Evaporation ◽  
Copper Surface ◽  
Copper Plate ◽  
Hybrid Nanofluid ◽  
Copper Surfaces ◽  
Latent Energy ◽  
Droplet Sizes

Abstract Droplet evaporation is an efficient process as it removes a large amount of heat by using the latent energy, making it suitable for heat transfer applications. In this research, evaporation of the silver-graphene hybrid nanofluid (SGHF) droplet, because of its synergistic thermal conductivity, is investigated for substrate temperature in a range of 25–100 °C. The experiments for droplet evaporation were performed in an environmental facility for two droplet sizes, 3 μL and 30 μL volume, on a copper plate. A 100 W silicone heater mat was used to heat the copper plate from the underside, while two T-type thermocouples were used to monitor its surface temperature. As droplet evaporation ended, a porous residue was formed on the copper surface. Subsequently, a 3 μL volume of the SGHF droplet was dispensed on the porous residue surface. The results showed a tremendous rise in the evaporation rate (up to 160%) for the subsequent SGHF droplet sitting on the porous residue as compared to the non-wetted copper surface. Moreover, the evaporation rate of the SGHF droplet on the copper surface increased up to 56% as compared to the water droplet for a substrate temperature range of 25–100 °C.

Droplet Evaporation of Cu–Al2O3 Hybrid Nanofluid Over Its Residue and Copper Surfaces: Toward Developing a New Analytical Model

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Farooq Riaz Siddiqui ◽  
Chi Yan Tso ◽  
Sau Chung Fu ◽  
Huihe Qiu ◽  
Christopher Y. H. Chao
Keyword(s):  
Analytical Model ◽  
Evaporation Rate ◽  
Heat Dissipation ◽  
High Heat ◽  
Droplet Evaporation ◽  
Copper Surface ◽  
Hybrid Nanofluid ◽  
High Heat Flux ◽  
High Heat Transfer ◽  
Critical Residue

Abstract Droplet evaporation-based cooling techniques, such as the spray cooling, give high heat transfer rates by utilizing latent energy and are usually preferred in thermal applications. However, with the significant rise in heat dissipation levels for high heat flux devices, these devices cannot be thermally managed due to the limited cooling capacity of existing thermal fluids. In this paper, we report the evaporation of the Cu–Al2O3 hybrid nanofluid (HNF) droplet on a copper surface as well as its own residue surface, developed from the evaporation of the first Cu–Al2O3 HNF droplet. As the main novelty, we identify the critical residue size and investigate the residue size effect, above and below the critical residue size, on evaporation rate of the succeeding Cu–Al2O3 HNF droplet resting over a residue surface. We also develop a new analytical model to estimate the Cu–Al2O3 HNF droplet evaporation rate and compare our results with other existing models. The results show that the Cu–Al2O3 HNF droplet gives 17% higher evaporation rate than a water droplet on a copper surface. Also, the evaporation rate of the Cu–Al2O3 HNF droplet on a residue surface sharply increases by 106% with increasing residue size up to the critical residue size. However, further increasing the residue size above its critical value has a negligible effect on the droplet evaporation rate. Moreover, the evaporation rate of the Cu–Al2O3 HNF droplet on its residue surface is enhanced up to 104% when compared to a copper surface.

Experimental Investigation on Silver-Graphene Hybrid Nanofluid Droplet Evaporation and Wetting Characteristics of its Nanostructured Droplet Residue

2019 ◽  
Author(s):  
Farooq R. Siddiqui ◽  
Edwin C. Y. Tso ◽  
Sau C. Fu ◽  
Christopher Y. H. Chao ◽  
Huihe Qiu
Keyword(s):  
Evaporation Rate ◽  
Volume Fraction ◽  
Spray Cooling ◽  
Droplet Evaporation ◽  
Copper Surface ◽  
Nanoporous Structure ◽  
Hybrid Nanofluid ◽  
Mixing Ratios ◽  
Static Contact ◽  
Wide Range

Abstract Droplet evaporation is a complex phase change process with a wide range of cooling applications, such as spray cooling and dropwise hotspot cooling in microelectronics, to name a few. The hybrid nanofluid droplet evaporation and its residue effects on evaporation of the subsequent hybrid nanofluid droplet is investigated in this research. Silver-graphene (Ag-GNP) hybrid nanofluid exhibiting synergistic thermal properties is investigated and prepared by dispersing silver nanoparticles along with graphene nanoplatelets in water at 0.1% volume fraction and with different mixing ratios, followed by ultrasonication. The evaporation rate and wetting characteristics of a 3 μl volume of Ag-GNP hybrid nanofluid droplet on a copper surface were studied using an optical tensiometer. Once dried, the nanoporous structure of the residue surface was examined using a scanning electron microscope, while the surface roughness was measured using an optical profiler. Experiments were continued to further investigate the evaporation rate and wetting effects of the subsequent Ag-GNP hybrid nanofluid droplet over the residue surface. The results showed improved wetting characteristics, with 88% reduction in initial static contact angle and 163–196% enhancement in evaporation rate of the subsequent Ag-GNP hybrid nanofluid droplets over the residue surfaces as compared to the copper surface.

Evaporation of Silver-Graphene Hybrid Nanofluid Droplet on Its Nanostructured Residue and Plain Copper Surfaces at Elevated Temperatures

2021 ◽  
Author(s):  
Farooq Riaz Siddiqui ◽  
Chi Yan TSO ◽  
Sau Chung Fu ◽  
Huihe Qiu ◽  
Christopher Yu Hang Chao
Keyword(s):  
Elevated Temperatures ◽  
Hybrid Nanofluid ◽  
Copper Surfaces

High Resolution Leed Study of The Fe Growth Mode on Cu(100), Cu(110) and Cu (111) Surfaces

1991 ◽  
Vol 237 ◽  
Author(s):  
Yuqun Cao ◽  
Pedro A. Montano
Keyword(s):  
High Resolution ◽  
Substrate Temperature ◽  
Epitaxial Growth ◽  
Copper Surface ◽  
Growth Mode ◽  
Diffraction Spot ◽  
Sudden Increase ◽  
Copper Surfaces ◽  
Single Crystal Surfaces ◽  
Before And After

ABSTRACTWe have investigated the growth mode of iron on clean Cu(100), Cu (110) and Cu(111) surfaces using high resolution LEED. We studied the effect of substrate temperature on the growth of epitaxial fee iron. Iron metal was evaporated from an electron beam source under UHV conditions and deposited on the copper single crystal surfaces at three different temperatures (173 K, 300 K and 473 K). A high resolution LEED system was used to measure the diffraction spot profiles. The samples were studied as a function of temperature after deposition on the copper substrates. The clean Cu surfaces were also measured and used as references for the Fe:Cu system. The diffraction spot profiles show Gaussian line shape before and after the Fe deposition. The effect of iron grown on the Cu surface is to reduce the coherent length. This effect is observed for all the copper surfaces. The intensity of the diffraction spots exhibit a sudden increase above 470 K, simultaneously a larger coherent length is observed. This effect occurs for all copper surfaces. The epitaxial growth of Fe is better on Cu (100) than on the other surfaces. The best epitaxial growth is obtained for the highest substrate temperature. A careful Auger study reveals that the anomalous increase observed on the intensity of the diffraction spots is related to the evaporation of iron from the copper surface. The spot profiles at low temperature are very broad and are suggestive of very poor epitaxy, random islands growth with a high probability of bec iron inclusions.

scholarly journals The passive state and adhesion

1930 ◽  
Vol 126 (803) ◽  
pp. 630-631 ◽  
Keyword(s):  
Aqueous Solution ◽  
Copper Surface ◽  
Copper Plate ◽  
Passive State ◽  
Metallic Surfaces ◽  
Absolute Alcohol ◽  
Surface Layers ◽  
Copper Surfaces ◽  
Chemical Substances ◽  
Magnesia Powder

In the course of an investigation into the tensile strength of joints formed by thin films of pure chemical substances between surfaces of steel or copper (‘Roy. Soc. Proc.,’ A, vol. 118, p. 209 (1928)), a curious effect due to the production of passivity at a copper surface was noticed. In making such measurements it is, of course, essential that the metallic surfaces should be absolutely clean and dry. Owing to the ease with which copper surfaces acquire a tarnish film, their cleaning presented some difficulty. On one occasion the copper plate was boiled in absolute alcohol and plunged, whilst still hot, into water containing a few drops of concentrated nitric acid, in order that it might cool in a non-tarnishing medium. When taken out, the surface was found to have assumed a uniform dull reddish tint quite unlike the patchy appearance produced by the usual visible tarnish film. This appearance persisted when the plate was boiled in alcohol or water and cooled in air and also when it was left exposed to impure damp air for several hours, i. e. , it survived conditions under which a normal copper surface would have tarnished rapidly. Gentle polishing with very finely divided magnesia powder on silk did not remove the reddish-tint, although abrasion with fine emerypaper, by removing the upper surface layers did. Normality was most conveniently restored by boiling the plate in a 2-5 per cent. aqueous solution of ammonia when the surface tarnished and blackened in patches; this tarnish was removed by polishing with magnesia powder on a wet leather and the process repeated until the surface tarnished uniformly. The surface of the plate, after removal of this tarnish, was found to be normal.

Leidenfrost Evaporation of Liquid Nitrogen Droplets

1994 ◽  
Vol 116 (4) ◽  
pp. 999-1006 ◽  
Author(s):  
S. Chandra ◽  
S. D. Aziz
Keyword(s):  
Surface Temperature ◽  
Liquid Nitrogen ◽  
Glass Surface ◽  
Evaporation Rate ◽  
Ambient Pressure ◽  
Droplet Diameter ◽  
Droplet Evaporation ◽  
Copper Surface ◽  
Droplet Impact ◽  
Bubble Nucleation

The evaporation of a single droplet of liquid nitrogen, levitated during film boiling above a solid, impervious surface, was studied experimentally. The droplet initial diameter (1.9 mm), surface temperature (~20°C), ambient temperature (~20°C), and ambient pressure (~0.1 MPa) were held constant. The principal parameters varied were the surface material (copper or glass), and roughness (0.35 to 50 μm). Measurements were made of the droplet diameter evolution and the surface temperature variation during droplet impact. Predictions from existing models of droplets in Leidenfrost evaporation agree well with measurements of the droplet evaporation rate. The droplet lifetime was found to be slightly longer on the glass surface than it was on the copper surface, corresponding to the greater cooling of the glass surface during droplet impact. The droplet evaporation rate was unchanged by small increases in surface roughness. However, ridges on the surface with a height of the same magnitude as the thickness of the vapor film under the drop caused vapor bubble nucleation in the droplet, and significantly reduced the droplet evaporation time.

WATER DROPLET EVAPORATION IN A CHAMBER ISOLATED FROM THE EXTERNAL ENVIRONMENT

2020 ◽  
Vol 6 (3) ◽  
pp. 8-22
Author(s):  
KSENIA A. Batishcheva ◽  
ATLANT E. Nurpeiis
Keyword(s):  
Water Vapor ◽  
Evaporation Rate ◽  
External Environment ◽  
Heat Removal ◽  
Droplet Evaporation ◽  
Droplet Volume ◽  
Evaporation Time ◽  
Aluminum Alloy Amg6 ◽  
Evaporation Of Droplets ◽  
Contact Diameter

With an increase in the productivity of power equipment and the miniaturization of its components, the use of traditional thermal management systems becomes insufficient. There is a need to develop drip heat removal systems, based on phase transition effects. Cooling with small volumes of liquids is a promising technology for microfluidic devices or evaporation chambers, which are self-regulating systems isolated from the external environment. However, the heat removal during evaporation of droplets into a limited volume is a difficult task due to the temperature difference in the cooling device and the concentration of water vapor that is unsteady in time depending on the mass of the evaporated liquid. This paper presents the results of an experimental study of the distilled water microdrops’ (5-25 μl) evaporation on an aluminum alloy AMg6 with the temperatures of 298-353 K in an isolated chamber (70 × 70 × 30 mm3) in the presence of heat supply to its lower part. Based on the analysis of shadow images, the changes in the geometric dimensions of evaporating drops were established. They included the increase in the contact diameter, engagement of the contact line due to nano roughening and chemical composition inhomogeneous on the surface (90-95% of the total evaporation time) of the alloy and a decrease in the contact diameter. The surface temperature and droplet volume did not affect the sequence of changes in the geometric dimensions of the droplets. It was found that the droplet volume has a significant effect on the evaporation time at relatively low substrate temperatures. The results of the analysis of droplet evaporation rates and hygrometer readings have shown that reservoirs with salt solutions can be used in isolated chambers to control the concentration of water vapor. The water droplets evaporation time was determined. The analysis of the time dependences of the evaporation rate has revealed that upon the evaporation of droplets in an isolated chamber under the conditions of the present experiment, the air was not saturated with water vapor. The latter did not affect the evaporation rate.

scholarly journals Experimental study on the evaporating progress of hexane lens on immiscible liquid：Spreading and receding

2021 ◽  
Vol 321 ◽  
pp. 01017
Author(s):  
Aiqiang Chen ◽  
Jinghong Yin ◽  
Huiqin Wang ◽  
Bin Liu ◽  
Rachid Bennacer
Keyword(s):  
Evaporation Rate ◽  
Droplet Evaporation ◽  
Immiscible Liquid ◽  
Deionized Water ◽  
Maximum Diameter ◽  
Evaporation Process ◽  
Droplet Spreading ◽  
Minimum Diameter ◽  
Base Solution ◽  
Evaporation Intensity

The change of evaporation liquid on another immiscible liquid has important guiding significance for many applications. In this experiment, the geometric temperature distribution and evaporation rate of n-hexane droplets were observed and recorded by changing the temperature of deionized water. The results show that with the increase of temperature of deionized water-based solution, the maximum diameter of n-hexane droplet spreading after titration increases gradually, while the minimum diameter of n-hexane droplet disappearing decreases gradually. Meanwhile, the evaporation rate of n-hexane droplet is constant during the whole evaporation process. It should also be mentioned that if the base solution is changed from deionized water to a certain concentration of salt solution, the maximum diameter of n-hexane droplet spreading will be reduced, and the evaporation intensity will be relatively reduced. These experimental results will give us a better understanding of the mechanism and characteristics of droplet evaporation.

Pool Boiling Heat Transfer of Water on Hydrophilic Surfaces With Different Wettability

2016 ◽  
Author(s):  
Adam R. Girard ◽  
Jinsub Kim ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Copper Surface ◽  
Contact Angles ◽  
Copper Surfaces ◽  
Nanoscale Structures ◽  
Flat Surfaces ◽  
Hydrophilic Surfaces ◽  
Alkali Solutions

The effect of wettability on boiling heat transfer (BHT) coefficient and critical heat flux (CHF) in pool boiling of water on hydrophilic surfaces having different contact angles was investigated. Hot alkali solutions were utilized to promote cupric and cuprous oxide growth which exhibited micro and nanoscale structures on copper surfaces, with thicknesses on the order of a couple of micrometers. These structure and surface energy variations result in different levels of wettability and roughness while maintaining the effusivity of the bare copper surface. The study showed that the BHT coefficient has an inverse relationship to wettability; the BHT coefficient decreases as wettability increases. Furthermore, it was shown that this dependency between BHT coefficient and wettability is more significant than the relationship between BHT coefficient and surface roughness. The CHF was also found to increase with increases in wettability and roughness. For the most hydrophilic surface tested in this study, CHF values were recorded near the 2,000 kW/m2 mark. This value is compared with maximum values reported in literature for water on non-structured flat surfaces without area enhancements. Based on these results it is postulated that there exists a true hydrodynamic CHF limit for pool boiling with water on flat surfaces, very near 2,000 kW/m2, independent of heater material, representing an 80% increase in the limit suggested by Zuber [1].

Studies of Copper Surfaces modified by Thermal and Plasma Treatments

2000 ◽  
Vol 612 ◽  
Author(s):  
G.P. Beyer ◽  
M. Baklanov ◽  
T. Conard ◽  
K. Maex
Keyword(s):  
Chemical Composition ◽  
Thermal Treatment ◽  
Photoelectron Spectroscopy ◽  
Hydrogen Plasma ◽  
Copper Film ◽  
Copper Surface ◽  
Ex Situ ◽  
Clean Room ◽  
Copper Surfaces ◽  
The Difference

AbstractIt was found that copper surfaces, which had been exposed to a clean room atmosphere, were covered by a layer, whose chemical composition can be described by Cu(OH)2·CuCO3. This layer can effectively be removed by either a short thermal treatment in vacuum at 350°C, a hydrogen plasma treatment, or a combination of both. Ex-situ photoelectron spectroscopy measurements show little difference of the chemical composition of the surface after the respective treatments. The thermal treatment, however, gives rise to re-crystallisation of the copper film due to the difference in temperature of deposition and the anneal. Ex-situ ellipsometry measurements indicate that the hydrogen plasma not only removes Cu(OH)2·CuCO3 but also passivates the copper surface.

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