Apparent Emissivity of Combustion Soot Aggregate Coating at High Temperature

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Tai Ran Fu ◽  
Ji Bin Tian ◽  
Hua Sheng Wang
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Room Temperature ◽  
Spectral Emissivity ◽  
Radiative Properties ◽  
Nickel Substrate ◽  
Soot Aggregate ◽  
Different Temperatures ◽  
Few Data ◽  
Total Hemispherical Emissivity

Soot aggregates frequently occur during combustion or pyrolysis of fuels. The radiative properties of soot aggregates at high temperature are important for understanding soot characteristics and evaluating heat transfer in combustion systems. However, few data for soot radiative properties at high temperature were available. This work experimentally investigated the apparent emissivity of the soot aggregate coating at high temperature using spectral and total hemispherical measurements. The soot aggregate coatings were formed on nickel substrates by a paraffin flame. The surface and inner morphology of the coatings were characterized by scanning electron microscope (SEM). The thickness of the coating was 30.16 μm so the contribution of the smooth nickel substrate to the apparent radiation from the coating could be neglected. The total hemispherical emissivity of the coating on the nickel substrate was measured using the steady-state calorimetric method at different temperatures. The spectral directional emissivity of the coating was measured for the wavelength of 0.38–16.0 μm at the room temperature. The measurements show that the total hemispherical emissivity decreases from 0.895 to 0.746 as the temperature increases from 438 K to 1052 K. The total hemispherical emissivity of the coating deposited on the nickel substrate is much larger than those of the nickel substrate and a nickel oxidization film. The measured spectral emissivity of the coating at the room temperature was used to theoretically calculate the total hemispherical emissivity at different temperatures by integration with respect to wavelength. The measured and calculated total hemispherical emissivities were similar, but their changes relative to temperature were completely opposite. This difference is due to the fact that the spectral emissivity of the coating is a function of temperature. The present results provide useful reference data for analyzing radiative heat transfer at high temperature of soot aggregates in combustion processes.

scholarly journals Investigation of Fatigue Behavior of ABS and PC-ABS Polymers at Different Temperatures

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1818
Author(s):  
Andrea Mura ◽  
Alessando Ricci ◽  
Giancarlo Canavese
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Working Condition ◽  
Fatigue Behavior ◽  
Polymeric Materials ◽  
Cyclic Loads ◽  
Structural Components ◽  
Working Temperature ◽  
Different Temperatures ◽  
Positive Effect

Plastics are widely used in structural components where cyclic loads may cause fatigue failure. In particular, in some applications such as in vehicles, the working temperature may change and therefore the strength of the polymeric materials. In this work, the fatigue behavior of two thermoplastic materials (ABS and PC-ABS) at different temperatures has been investigated. In particular, three temperatures have been considered representing the working condition at room temperature, at low temperature (winter conditions), and high temperature (summer conditions and/or components close to the engine). Results show that high temperature have big impact on fatigue performance, while low temperatures may also have a slight positive effect.

High Temperature Properties of CoFe/CoNi and Fe/CoNi Biphase Microwires

2015 ◽  
Vol 233-234 ◽  
pp. 265-268 ◽  
Author(s):  
Irene Iglesias ◽  
Rhimou El Kammouni ◽  
Kseniay Chichay ◽  
Manuel Vazquez ◽  
Valeria Rodionova
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Single Phase ◽  
Amorphous Structure ◽  
Magnetic Behaviour ◽  
Heating Process ◽  
Saturation Magnetostriction ◽  
Magnetostriction Constant ◽  
Different Temperatures ◽  
Drawing Technique

The objective of this work has been to analyze the high-temperature behavior of magnetically single-and biphase microwires because of its interest from fundamental and applications viewpoints. Two alloy compositions with amorphous structure covered by glass have been prepared as magnetically single phase microwires by quenching & drawing technique: CoFe-based with near zero saturation magnetostriction constant and Fe-based with positive saturation magnetostriction constant. The same wires were used as the core for magnetically biphase microwires. Second CoNi phase was deposited by electroplating. Magnitudes as saturation magnetization and hysteresis parameters are determined in the temperature range from room temperature up to 1200 K. We proceed to a comparative analysis of their magnetic behaviour at different temperatures as well as after cooling down to room temperature. Information on the Curie temperature of different phases and on the influence of heating process on the magnetic properties is thus derived.

An Ultrasonic Non-Contact Handling Device from Quartz Glass for Middle and High Temperature Applications

2014 ◽  
Vol 1018 ◽  
pp. 31-38
Author(s):  
Edgars Locmelis
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Manufacturing Processes ◽  
Mechanical Contact ◽  
High Temperature Region ◽  
Handling Device ◽  
Design And Manufacturing ◽  
Different Temperatures ◽  
Small Change

Ultrasonic non-contact handling is used to manipulate surface sensitive and fragile workpieces, e.g. wafers and glass plates, without mechanical contact. While the technology is available forapplications at room temperature, some of the manufacturing processes of products mentioned aboverequire handling at elevated temperatures. To enable this technology for handling in thermal processesan ultrasonic system for increased working temperatures is required. In order to adapt the ultrasonicsystem to the limited working temperature of the actuator, the handling system has to be operated attwo different temperatures. Due to the small change of the Young's modulus over temperature, quartzglass was chosen as material for the components in the high temperature region. The paper presentsthe design and manufacturing of a novel ultrasonic system operated at 790 °C while the actuator iskept at room temperature.

Thermal Assessment of a Latent Heat Energy Storage Module Using a High Temperature Phase Change Material With Enhanced Radiative Properties

2014 ◽  
Author(s):  
Antonio Ramos Archibold ◽  
Abhinav Bhardwaj ◽  
Muhammad M. Rahman ◽  
D. Yogi Goswami ◽  
Elias L. Stefanakos
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Natural Convection ◽  
Phase Change ◽  
Temperature Response ◽  
High Temperature Phase ◽  
Radiative Properties ◽  
Temperature Phase ◽  
Measured Temperature ◽  
Numerical Predictions

This paper presents a comprehensive analysis of the heat transfer during the melting process of a high temperature (> 800°C) PCM encapsulated in a vertical cylindrical container. The energy contributions from radiation, natural convection and conduction have been included in the mathematical model in order to capture most of the physics that describe and characterize the problem and quantify the role that each mechanism plays during the phase change process. Numerical predictions based on the finite volume method has been obtained by solving the mass, momentum and energy conservation principles along with the enthalpy porosity method to track the liquid/solid interface. Experiments were conducted to obtain the temperature response of the TES-cell during the sensible heating and phase change regions of the PCM. Continuous temperature measurements of porcelain crucibles filled with ACS grade NaCl were recorded. The temperature readings were recorded at the center of the sample and at the wall of the crucible as the samples were heated in a furnace over a temperature range of 700 °C to 850 °C. The numerical predictions have been validated by the experimental results and the effect of the controlling parameters of the system on the melt fraction rate, total and radiative heat transfer rates at the inner surface of the cell have been evaluated. Results showed that the natural convection is the dominant heat transfer mechanism. In all the experimental study cases, the measured temperature response captures the PCM melting trends with acceptable repeatability. The uncertainty analysis of the experiment yielded an approximate error of ±5.81°C.

On the Role of Radiation in Low Density Silicon Carbide Foams

2012 ◽  
Author(s):  
Charles C. Tseng ◽  
Ruth L. Sikorski ◽  
R. Viskanta ◽  
Ming Y. Chen
Keyword(s):  
Heat Transfer ◽  
Silicon Carbide ◽  
High Temperature ◽  
Thermal Radiation ◽  
Thermal Protection ◽  
Mie Scattering ◽  
Radiative Properties ◽  
Void Space ◽  
Insulation Systems ◽  
Foam Properties

There are a variety of foams that can be used in thermal protection and/or thermal insulation systems. At high temperature (> 1000 K) thermal radiation may be important or dominate heat transfer in a foam; however, studies based on more detailed thermal radiation analysis are limited. In this paper foams are considered to be semitransparent, because radiation can penetrate through the pore (or void) space and/or foam skeleton (ligament), depending on the materials from which the foams are made. Of particular interest of this study is to understand how the properties of foam material such as its density, mean cell size, etc. affect the radiative transfer through silicon carbide (SiC) foams. In the paper, the dimensionless strut diameter is considered an important parameter of foams, and the radiative properties of the foams are analyzed by Mie scattering theory. The attenuation/extinction behavior of SiC foams can be considered as a function of the dimensionless strut diameter of the foam. The results reveal that the foam properties can significantly reduce radiative heat transfer through the high temperature foam used for the thermal protection.

STRAIN RATE DEPENDENCE ON THE HIGH TEMPERATURE MECHANICAL BEHAVIOR OF THE NI-18SI-3.0NB-1.0CR-0.2B INTERMETALLIC ALLOY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1040-1046 ◽  
Author(s):  
CHIH-CHIANG FU ◽  
JASON SHIAN-CHING JANG ◽  
I-SUI LEE ◽  
HUEI-SEN WANG
Keyword(s):  
High Temperature ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Fracture Pattern ◽  
Strain Rates ◽  
Dispersion Phase ◽  
Air Atmosphere ◽  
Different Temperatures

The effect of strain rate and temperature on the mechanical behavior of the Ni -18 Si -3.0 Nb -1.0 Cr -0.2 B alloy was investigated by atmosphere-controlled tensile testing in vacuum and air atmosphere at different strain rates and different temperatures. The results reveal that the Ni -18 Si -3.0 Nb -1.0 Cr -0.2 B alloy exhibits ductile mechanical behavior (UTS > 1200 MPa, ε > 8%) at room temperature under different atmosphere conditions. In addition, both of the ultimate tensile strength and elongation exhibit quite insensitive response with respect to the loading strain rate when tests are held at temperatures below 973K. The elongation of the samples tested in vacuum and air for the Ni -18 Si -3 Nb -1 Cr -0.2 B alloy exhibits a significantly increase with temperature from 973K to 1073K. In addition, all fracture surfaces tested at 1073K in vacuum and air atmosphere presents a typical ductile fracture surface, a fully dimpled fracture pattern. The fact of increasing in elongation at high temperature (1073K) is suggested to be attributed by the dynamic recrystallization that occurs preferentially around the dispersion phase or grain boundaries and so as to enhance the ductility by reducing the stress concentration at or near grain boundaries.

Analysis on Residual Capacity of Steel after High Temperature

2013 ◽  
Vol 827 ◽  
pp. 322-327
Author(s):  
Xiu Ying Yang
Keyword(s):  
High Temperature ◽  
Carrying Capacity ◽  
Room Temperature ◽  
Numerical Models ◽  
Physical And Mechanical Properties ◽  
Steel Beams ◽  
Steel Material ◽  
Different Temperatures ◽  
Residual Capacity ◽  
Steel Properties

Steel material is very sensitive to temperature, the physical and mechanical properties at high temperature are distinct with those at room temperature. Taking steel beams as the research objects, based on EUROCODE3 for the steel properties at high temperature, this paper established numerical models and analyzed the carrying capacity of steel beams under different temperatures. According to the analysis, it is concluded that the higher the temperature, the lower the subsequent carrying capacity of the steel beam, and the formulas between them are defined by fitting the data.

Study on the Mechanical Property of Concrete Materials under High Temperature (Fire)

2012 ◽  
Vol 166-169 ◽  
pp. 3018-3022
Author(s):  
Man Li Ou ◽  
Wei Jun Cao ◽  
Long Min Jiang
Keyword(s):  
Mechanical Property ◽  
Compressive Strength ◽  
High Temperature ◽  
Room Temperature ◽  
Holding Time ◽  
Water Cooling ◽  
Different Temperatures ◽  
Concrete Materials

The performance of concrete materials under high temperature is more complex than that under room temperature. This paper, by analyzing the mechanical property of concrete materials under high temperature(fire), probes into the changing law of the concrete materials' compressive strength under different temperatures (16 °C-800 °C) and different static placing time and makes a comparison on the concrete materials' strength between natural cooling and water cooling; illustrates the relationships of concrete materials' compressive strength and temperature, holding time and cooling and other factors under high temperature(fire).

Theoretical Predictions of Spectral Emissivity for Coal Ash Deposits

2013 ◽  
Author(s):  
Dong Liu ◽  
Yuan-Yuan Duan ◽  
Zhen Yang
Keyword(s):  
Heat Transfer ◽  
Chemical Composition ◽  
Coal Ash ◽  
Spectral Emissivity ◽  
Radiative Properties ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Chemical Compositions ◽  
Boiler Efficiency ◽  
Ash Deposit

Ash deposits decrease the boiler efficiency, reduce the generating capacity and cause unscheduled outages. The radiative heat transfer is the major heat transfer mechanism in utility boilers; thus, the ash deposit emissivity is critical to boiler efficiency and safety. This paper presents a radiative transfer model to predict the spectral emissivities of coal ash deposits. The model includes the effects of the microstructure, chemical composition and temperature. Typical ash deposit microstructures are generated using diffusion-limited aggregation (DLA). The radiative properties are then calculated using the Generalized Multiparticle Mie-solution (GMM). The combined GMM and DLA model predicts spectral emissivity better than the original Mie theory and Tien’s dependent scattering theory with the average relative difference between predicted results and experimental data decreasing from 17.7% to 8.1% for sample 1 and from 16.5% to 4.2% for sample 2. Maxwell-Garnett effective medium theory is used to calculate the ash deposit optical constants based on the chemical compositions to include the effect of chemical composition. Increasing temperatures increase the particle diameters and particle volume fractions and, thus, the spectral emissivities. The spectral emissivity ultimately remains constant and less than one. The homogeneous slab model gives the upper limit of the ash deposit spectral emissivity.

Investigation of tetragonal distortion in the PbTiO3–BiFeO3 system by high-temperature x-ray diffraction

1995 ◽  
Vol 10 (5) ◽  
pp. 1301-1306 ◽  
Author(s):  
V.V.S.S. Sai Sunder ◽  
A. Halliyal ◽  
A.M. Umarji
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Room Temperature ◽  
Tetragonal Distortion ◽  
X Ray Diffraction ◽  
Solution System ◽  
X Ray ◽  
Lattice Constants ◽  
Solid Solution System ◽  
Different Temperatures

Compositions in the (Pb1−xBix (Ti1−xFex)O3 solid solution system for x ⋚ 0.7 show unusually large tetragonal distortion. High-temperature x-ray diffraction was used to study the tetragonal distortion as a function of temperature (25–700 °C) for compositions (x = 0–0.7) using powders prepared by solid-state reaction in the above system. Large changes in the lattice parameters were observed over a narrow temperature range near Curie temperature (TC) for compositions near the morphotropic phase boundary (MPB) (x ≃ 0.7). Compositions near MPB showed a c/a ratio of 1.18 at room temperature. Polar plots of lattice constants at different temperatures indicated strong anisotropic thermal expansion with zero thermal expansion along the [201] direction.

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