Thermal conductivity of anodized aluminum oxide layer: The effect of electrolyte and temperature

Lee, Junghoon; Kim, Yonghwan; Jung, Uoo-Chang; Chung, Wonsub

doi:10.1016/j.matchemphys.2013.05.058

Cited by 39 publications

(29 citation statements)

References 40 publications

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“…The equations below show how a response is calculated for the motored and fired engine results. In equation (14), the coefficient C P is chosen for EOP C, coefficient C E is used for EOP B and A response = C 0 + C TBC + C CR 3 CR Ã + C R a 3 R a Ã + C S (motored engine) ð13Þ response = C 0 + C TBC + C AB + C CR 3 CR Ã + C R a 3 R a Ã + C P =C E (fired engine) ð14Þ factor Ã = 2 3 factor À factor median factor max À factor min ; Figure 16. MLR model coefficients for the energy flow distribution under motored conditions.…”

Section: Resultsmentioning

confidence: 99%

“…As the volume of the oxide is twice that of the aluminum, 0.10 mm was machined off the surface where the coating was formed. Typical values for thermal conductivity and heat capacity for this type of coating are 0.7-1.3 W/m K and 860-890 J/kg K. 14 The zirconia TBC with the same target thickness of 200 mm was applied by plasma-spraying after sandblasting the surface and application of a 150mm-thick metallic bond coat. The bond coat and top coat materials were acquired from Oerlikon, with the specifications Amdry 365-2 and Metco 204b-ns, respectively.…”

Section: Test Object Detailsmentioning

confidence: 99%

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Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine

Somhorst

Oevermann

Bovo

et al. 2019

International Journal of Engine Research

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The effect of two thermal barrier coatings and their surface roughness on heat transfer, combustion, and emissions has been investigated in a single-cylinder light-duty diesel engine. The evaluated thermal barrier coating materials were plasma-sprayed yttria-stabilized zirconia and hard anodized aluminum, which were applied on the piston top surface. The main tool for the investigation was cylinder pressure analysis of the high-pressure cycle, from which the apparent rate of heat release, indicated efficiency, and heat losses were derived. For verification of the calculated wall heat transfer, the heat flow to the piston cooling oil was measured as well. Application of thermal barrier coatings can influence engine operating conditions like charge temperature and ignition delay. Therefore, extra attention was paid to choosing stable and repeatable engine operating points. The experimental data were modeled using multiple linear regression to isolate the effects of the coatings and of the surface roughness. The results from this study show that high surface roughness leads to increased wall heat losses and a delayed combustion. However, these effects are less pronounced at lower engine loads and in the presence of soot deposits. Both thermal barrier coatings show a reduction of cycle-averaged wall heat losses, but no improvement in indicated efficiency. The surface roughness and thermal barrier coatings had a significant impact on the hydrocarbon emissions, especially for low-load engine operation, while their effect on the other exhaust emissions was relatively small.

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Section: Resultsmentioning

confidence: 99%

Section: Test Object Detailsmentioning

confidence: 99%

Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine

Somhorst

Oevermann

Bovo

et al. 2019

International Journal of Engine Research

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show abstract

“…The aluminum was considered to have an anodized surface, which has an emissivity of 0.84. 48 The surface of the copper is covered with a layer of black oxide that makes the ε equals 0.78. 49 Such a simulation can be costly, both in terms of processing time and memory size.…”

Section: Governing Equationsmentioning

confidence: 99%

“…In fact, in the current study, only the net radiative heat flux from the heat sink to the ambient has been considered and the refractive index has been assumed equal to the unity. The aluminum was considered to have an anodized surface, which has an emissivity of 0.84 48 . The surface of the copper is covered with a layer of black oxide that makes the ε equals 0.78 49…”

Section: Heat Transfer Modelmentioning

confidence: 99%

Optimization and feasibility analysis of a microscale pin‐fins heat sink of an ultrahigh concentrating photovoltaic system

et al. 2020

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Nowadays, the most recent optical configuration based on Cassegrain and Fresnel lens designs of concentrator photovoltaic(CPV) has shown a race to achieve the ultrahigh concentration ratio. Still, none of those has experimentally shown an optical concentration ratio (GC) beyond 2000 suns. This is because their energy concentration ratios are challenged by the excessive temperature raised throughout the optical stages, which diminishes the efficiency of the solar cell. In this context, this research work aims to numerically investigate a microscale pin-fins heat sink configuration to enhance the thermal performance and the cost-competitivity of ultrahigh CPV thermal receiver. The impacts of the solar cell area, cell efficiency, and heat sink's material have been analyzed and discussed. The results showed that a circular pin-fins heat sink could accomplish a drop of 23.28% in the maximum operating cell temperature at 10 000 suns for cell area of 1 × 1 mm 2 relatively compared to the conventional flat-plate heat sink. Furthermore, for a circular pin-fins heat sink with a cell area of 2 × 2 mm 2 , the cell temperature started exceeding the safe operating range of temperature (80 C) at 8000 suns with an average temperature of 96.1 C and reaching a maximum of 113.91 C at 10 000 suns. A gradient temperature on the planar direction of the aluminum circular pin-fins heat sink was about 1.187 C at 10 000 suns whereas 0.703 C was recorded in the case of a copper circular pin-fins heat sink. The circular pin-fins heat sink showed the highest thermal performance resulting in maintaining the solar cell temperature within its safe operating range even beyond 10 000 suns. From an economic point of view, aluminum circular pin-fins heat sink has been found to be less costly than the copper one. Finally, it was found that at 8000 suns, the flat-plate heat sink cost is more expensive than the traditional pin-fins heat sink by 14.7%, where the flat-plate heat sink becomes the worst economic configuration at 10 000 suns. At that concentration ratio, the cost has increased by 43.38%, 5.75%, and 10.61% compared to the traditional pin-fins heat sink, cylindrical pin-fins heat sink, and circular pin-fins heat sink, respectively.

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“…Furthermore, their low dielectric strength and thermal conductivity (seen in Table 1) limited the application on high power electronic devices. Preparing aluminum nitride or alumina coating on the substrate can enhance the heat dissipation efficiency of the substrate [17]. Although aluminum nitride coating can provide higher thermal conductivity, its dielectric strength is 8 kV/mm, while its thickness is difficult to exceed 5 µm, and the coating size is limited to less than 4.5 square inches.…”

Section: Materials Dielectric Strength (Kv/mm) Thermal Conductivity (mentioning

confidence: 99%

Fabrication of a Thick Crystalline Al2O3 Coating with Insulation and High Thermal Conductivity via Anodic Oxidation and Subsequent Mic Arc Discharge Treatment

Song

Jiang

2020

Coatings

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Amorphous Al2O3 coating with a thickness of 143 μm was firstly prepared by anodic oxidation, then the amorphous Al2O3 was transformed into crystalline Al2O3 through applying micro arc discharge. The crystal structure of the Al2O3 coatings was analyzed with an X-ray diffractometer. Results indicated that the coating consisted of amorphous and crystalline Al2O3. The microstructure of the coating was characterized by scanning electron microscopy, which showed that the coating had a compact structure. The thermal conductivity of the coating was 23.7 W/m·K, which is significantly higher than that of amorphous Al2O3 coating. The total and specific breakdown voltages of the coating were 3.85 kV and 26.92 kV/mm, which is suitable to apply for high power LED heat sink substrate.

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Thermal conductivity of anodized aluminum oxide layer: The effect of electrolyte and temperature

Cited by 39 publications

References 40 publications

Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine

Evaluation of thermal barrier coatings and surface roughness in a single-cylinder light-duty diesel engine

Optimization and feasibility analysis of a microscale pin‐fins heat sink of an ultrahigh concentrating photovoltaic system

Fabrication of a Thick Crystalline Al2O3 Coating with Insulation and High Thermal Conductivity via Anodic Oxidation and Subsequent Mic Arc Discharge Treatment

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