scholarly journals Study on Heat Transfer Performance and Anti-Fouling Mechanism of Ternary Ni-W-P Coating

2020 ◽  
Vol 10 (11) ◽  
pp. 3905
Author(s):  
Lu Ren ◽  
Yanhai Cheng ◽  
Jinyong Yang ◽  
Qingguo Wang
Keyword(s):  
Heat Transfer ◽  
Surface Energy ◽  
Transition State ◽  
Heat Transfer Performance ◽  
High Surface ◽  
Deposition Process ◽  
Oxidation Products ◽  
Transfer Efficiency ◽  
Transfer Performance ◽  
Heat Transfer Efficiency

Since the formation of fouling reduces heat transfer efficiency and causes energy loss, anti-fouling is desirable and may be achieved by coating. In this work, a nickel-tungsten-phosphorus (Ni-W-P) coating was prepared on the mild steel (1015) substrate using electroless plating by varying sodium tungstate concentration to improve its anti-fouling property. Surface morphology, microstructure, fouling behavior, and heat transfer performance of coatings were further reported. Also, the reaction path, transition state, and energy gradient change of calcite, aragonite, and vaterite were also calculated. During the deposition process, as the W and P elements were solids dissolved in the Ni crystal cell, the content of Ni element was obviously higher than that of the other two elements. Globular morphology was evenly covered on the surface. Consequently, the thermal conductivity of ternary Ni-W-P coating decreases from 8.48 W/m·K to 8.19 W/m·K with the increase of W content. Additionally, it goes up to 8.93 W/m·K with the increase of heat source temperature 343 K. Oxidation products are always accompanied by deposits of calcite-phase CaCO3 fouling. Due to the low surface energy of Ni-W-P coating, Ca2+ and [CO3]2− are prone to cross the transition state with a low energy barrier of 0.10 eV, resulting in the more formation of aragonite-phase CaCO3 fouling on ternary Ni-W-P coating. Nevertheless, because of the interaction of high surface energy and oxidation products on the bare matrix or Ni-W-P coating with superior W content, free Ca2+ and [CO3]2− can be easy to nucleate into calcite. As time goes on, the heat transfer efficiency of material with Ni-W-P coating is superior to the bare surface.

Experimental Study on the Thermal Properties and Stability of Hybrid Nanofluids and Evaluation of its Heat Exchange Efficiency

2020 ◽  
Author(s):  
Yubai Xiao ◽  
Hu Zhang ◽  
Junmei Wu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
High Thermal Conductivity ◽  
Transfer Efficiency ◽  
Working Fluid ◽  
Transfer Performance ◽  
Heat Transfer Efficiency ◽  
Hybrid Nanofluids

Abstract In recent years, hybrid nanofluids, as a new kind of working fluid, have been widely studied because they possessing better heat transfer performance than single component nanofluids when prepared with proper constituents and proportions. The application of hybrid nanofluids in nuclear power system as a working fluid is an effective way of improving the capability of In-Vessel Retention (IVR) when the reactor is in a severe accident. In order to obtain hybrid nanofluids with excellent heat transfer performance, three kinds of hybrid nanofluids with high thermal conductivity are measured by transient plane source method, and their viscosity and stability are also investigated experimentally. These experimental results are used to evaluate the heat transfer efficiency of hybrid nanofluids. The results show that: (1) The thermal conductivity of hybrid nanofluids increases with increasing temperature and volume concentration. When compared to the base fluid, the thermal conductivity of Al2O3-CuO/H2O, Al2O3-C/H2O and AlN-TiO2/H2O nanofluids at 0.25% volume concentration increased by 36%, 24%, and 22%, respectively. (2) Surfactants can improve the stability of hybrid nanofluids. The Zeta potential value is related to the thermal conductivity of the hybrid nanofluids, and it could be used to explain the relationship between the thermal conductivity of the hybrid nanofluids and the dispersion. It also could provide a reference for subsequent screening of high thermal conductivity nanofluids. (3) The addition of C/H2O can effectively reduce the dynamic viscosity coefficient of hybrid nanofluids. (4) The analysis of heat transfer efficiency of the hybrid nanofluids found that both Al2O3-CuO/H2O and Al2O3-C/H2O have better heat transfer ability than water under certain mixing conditions. This study is conducive to further optimizing hybrid nanofluids and its application to the In-Vessel Retention in severe reactor accidents.

scholarly journals Effect of Environmental Wind on Performance of a 600MW Direct Air-cooled Unit Based on FLUENT

2019 ◽  
Vol 118 ◽  
pp. 02019
Author(s):  
Junfeng Xu ◽  
Taoying Wang ◽  
Minmin Zhao
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Flow Field ◽  
Wind Direction ◽  
Heat Transfer Performance ◽  
Air Flow ◽  
Transfer Efficiency ◽  
Windward Side ◽  
Transfer Performance ◽  
Heat Transfer Efficiency

The external flow field of a 600MW air-cooled unit is numerically simulated based on FLUENT. The distribution law of air flow field of air-cooled unit under different wind speed and wind direction conditions is studied. The influence of wind speed and wind direction on the heat transfer performance of air-cooled unit is analyzed. Predict the exhaust pressure of direct air-cooled unit under the influence of environmental wind. The results show that in the +X direction environmental wind, the first row of air-cooled unit on the windward side is prone to backflow; in the +Y direction environmental wind, the first row of air-cooled unit on the windward side is prone to hot air recirculation. As the wind speed increases, the heat transfer efficiency of the air-cooled unit decreases. The dominant wind direction (WNW) environmental wind has the least impact on the heat transfer efficiency, and the furnace wind (+Y direction wind) has the greatest influence on the heat transfer efficiency. To improve the heat transfer performance of the air-cooled unit under windy conditions, it is necessary to narrow the range of the negative pressure zone below the air-cooled unit and increase the cooling air flow rate of the air-cooled unit.

Influence of Microscale Surface Modification on Impinging Flow Heat Transfer Performance

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
T. J. Taha ◽  
L. Lefferts ◽  
T. H. Van der Meer
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Transfer Performance ◽  
Deposition Process ◽  
Silicon Sample ◽  
Transfer Performance ◽  
Surface Area Ratio ◽  
Enhancement Of Heat Transfer ◽  
Flow Heat ◽  
Impinging Flow

An experimental approach has been used to investigate the influence of a thin layer of carbon nanotubes (CNTs) on the convective heat transfer performance under impinging flow conditions. A successful synthesis of CNT layers was achieved using a thermal catalytic vapor deposition process (TCVD) on silicon sample substrates. Three different structural arrangements, with fully covered, inline, and staggered patterned layers of CNTs, were used to evaluate their heat transfer potential. Systematic surface characterizations were made using scanning electron microscope (SEM) and confocal microscopy. The external surface area ratio of fully covered, staggered, and inline arrangement was obtained to be 4.57, 2.80, and 2.89, respectively. The surface roughness of the fully covered, staggered, and inline arrangement was measured to be (Sa = 0.365 μm, Sq = 0.48 μm), (Sa = 0.969 μm, Sq = 1.291 μm), and (Sa = 1.668 μm, Sq = 1.957 μm), respectively. On average, heat transfer enhancements of 1.4% and − 2.1% were obtained for staggered and inline arrangement of the CNTs layer. This is attributed to the negligible improvement on the effective thermal resistance due to the small area coverage of the CNT layer. In contrast, the fully covered samples enhanced the heat transfer up to 20%. The deposited CNT layer plays a significant role in reducing the effective thermal resistance of the sample, which contributes to the enhancement of heat transfer.

Effect of Jet Arrays and Structured Surfaces on Two-Phase Impingement Heat Transfer

2007 ◽  
Author(s):  
Xin Feng ◽  
James E. Bryan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Jet Impingement ◽  
Heat Fluxes ◽  
Transfer Efficiency ◽  
Surface Wetting ◽  
Two Phase ◽  
Structured Surfaces ◽  
Heat Transfer Efficiency ◽  
Impingement Heat Transfer

When heat fluxes and heat transport exceed 100 W/cm2, heat transfer efficiencies decrease rapidly. Experimental work will be presented exploring how micro jet arrays and structured surfaces can be used to increase heat transfer efficiency. Using water, ethanol, and HFE-7000 as working fluids, the effect of jet momentum, subcooling temperature and surface wetting are experimentally investigated on 1cm2 smooth and structured surfaces. From results obtained so far, heat transfer efficiency increases with increasing surface tension (decreasing surface wetting) with micro-jet arrays. Further, existing correlations for two-phase jet impingement cannot predict the heat transfer performance with acceptable accuracy as they do not account for surface wetting characteristics.

Experimental investigation of Silver / Water nanofluid heat transfer in car radiator

2021 ◽  
Vol 15 (1) ◽  
pp. 7743-7753
Author(s):  
H. T. Jarrah ◽  
S. S. Mohtasebi ◽  
E. Ettefaghi ◽  
F. Jaliliantabar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Volume Fraction ◽  
Cooling System ◽  
Pure Water ◽  
Research Work ◽  
Inlet Temperature ◽  
Transfer Performance ◽  
Heat Transfer Efficiency ◽  
Low Concentrations

Currently available fluids for heat transfer including refrigerants, water, ethylene glycol mixture, etc., have been widely exploited in various fields, especially in automobile cooling systems, for many years. However, these fluids possess poor heat transfer capability which means that to achieve acceptable heat transfer activity, high compactness and effectiveness of heat transfer systems are essential. This research work concentrates on preparation and use of water based Silver containing nanofluids in automobile cooling system. Nanoparticles volume fraction, fluid inlet temperature, coolant and air Reynolds numbers were optimized so that the heat transfer performance of the car radiator system was totally improved. It was found that increasing these parameters leads to enhancement of the heat transfer performance. In the best condition, the Ag/water nanofluids with low concentrations could amend heat transfer efficiency up to 30.2% in comparison to pure water.

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