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Crossley, Jacob, A. N. M. Taufiq Elahi, Mohammad Ghashami i Keunhan Park. "Characterization of commercial thermoelectric modules for precision heat flux measurement". Review of Scientific Instruments 93, nr 11 (1.11.2022): 114903. http://dx.doi.org/10.1063/5.0115915.
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In this article, we present a cost-effective approach to the precision measurement of heat flux using commercial thermoelectric modules (TEMs). Two different methods of measuring heat flux with TEMs are investigated, namely, passive mode based on the Seebeck effect and active mode based on the Peltier effect. For both modes, a TEM as a heat flux meter is calibrated to show a linear relation between the voltage across the TEM and the heat flux from 0 to ∼450 W m−2. While both modes exhibit sufficiently high sensitivities suitable for low heat flux measurement, active mode is shown to be ∼7 times more sensitive than passive mode. From the speculation on the origin of the measurement uncertainty, we propose a dual TEM scheme by operating the top TEM in passive mode while its bottom temperature maintains constant by the feedback-controlled bottom TEM. The dual TEM scheme can suppress the sensitivity uncertainty up to 3 times when compared to the single-TEM passive mode by stabilizing the bottom temperature. The response time of a 15 × 15 mm2 TEM is measured to be 8.9 ± 1.0 s for heating and 10.8 ± 0.7 s for cooling, which is slower than commercial heat flux meters but still fast enough to measure heat flux with a time resolution on the order of 10 s. We believe that the obtained results can facilitate the use of a commercial TEM for heat flux measurement in various thermal experiments.
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Brosse, A., P. Naisson, H. Hamdi i J. M. Bergheau. "Temperature measurement and heat flux characterization in grinding using thermography". Journal of Materials Processing Technology 201, nr 1-3 (maj 2008): 590–95. http://dx.doi.org/10.1016/j.jmatprotec.2007.11.267.
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Siddapureddy, Sudheer, i SV Prabhu. "Experimental and numerical simulation studies on heat transfer to calorimeters engulfed in diesel pool fires". Journal of Fire Sciences 35, nr 2 (marzec 2017): 156–76. http://dx.doi.org/10.1177/0734904117694047.
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Characterization of heat transfer to calorimeters engulfed in pool fires is extremely important. To estimate the heat flux to the calorimeters, experiments are performed with horizontal stainless steel 304L pipes engulfed in diesel pool fires. The concept of adiabatic surface temperature is applied to predict the incident heat flux to horizontally oriented calorimeters engulfed in diesel pool fires. Plate thermometers are used to measure the adiabatic surface temperature for diesel pool fires. The estimated subsurface temperatures inside the steel pipes using the adiabatic surface temperature concept and the measured temperatures are in good agreement. Adiabatic surface temperature is also computed from fire simulations. The incident heat fluxes to the steel pipes engulfed in fire predicted from the simulations are found to be in good agreement with the experiments. The fire numerical code is validated against the 1 m pool fire experimental results of centerline temperature distribution and irradiances away from fire. A correlation is provided for the estimation of adiabatic surface temperature for large diesel pool fires. These results would provide an effective way for thermal test simulations.
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Liu, Yongfu, i Peng Tan. "Numerical investigation on heat transfer characterization of liquid lithium metal in pipe". Journal of University of Science and Technology of China 52, nr 1 (2022): 7. http://dx.doi.org/10.52396/justc-2021-0043.
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<p>Liquid Li metal is a promising nuclear reactor coolant; however, relevant research regarding its heat transfer characteristics remains insufficient. In this study, a steady-state two-dimensional mathematical model is established to describe the heat transfer process of liquid Li in a straight pipe. A numerical analysis is conducted to investigate the effects of inlet velocity, inlet temperature, and wall heat flux on heat transfer in liquid Li. The results indicate the advantage of using liquid Li for improving heat transfer at high inlet temperatures (> 1000 K) compared with using liquid sodium and lead–bismuth eutectic. Considering the mechanism of the outlet radial heat flow model, the ratio of turbulent to molecular diffusion coefficients presents a parabolic distribution along the radius of the pipe. Increasing the inlet velocity, decreasing the inlet temperature, and decreasing the wall heat flux can effectively weaken the dominant role of molecular heat transfer owing to the low Prandtl number of liquid Li. The heat transfer of liquid Li is investigated comprehensively in this study, and the results provide a basis for the practical application of liquid Li as a promising coolant.</p>
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Zhang, Congchun, Jianze Huang, Juan Li, Shenyong Yang, Guifu Ding i Wei Dong. "Design, fabrication and characterization of high temperature thin film heat flux sensors". Microelectronic Engineering 217 (wrzesień 2019): 111128. http://dx.doi.org/10.1016/j.mee.2019.111128.
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Martínez, Germán, Francisco Valero i Luis Vázquez. "Characterization of the Martian Surface Layer". Journal of the Atmospheric Sciences 66, nr 1 (1.01.2009): 187–98. http://dx.doi.org/10.1175/2008jas2765.1.
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Abstract The authors have estimated the diurnal evolution of Monin–Obukhov length, friction velocity, temperature scale, surface heat flux, eddy-transfer coefficients for momentum and heat, and turbulent viscous dissipation rate on the Martian surface layer for a complete sol belonging to the Pathfinder mission. All these magnitudes have been derived from in situ wind and temperature measurements at around 1.3-m height and simulated ground temperature (from 0600 sol 25 to 0600 sol 26). Previously, neither values of turbulent viscous dissipation rate and eddy-transfer coefficients from in situ measurements for the Martian surface layer nor diurnal evolutions of all the previously mentioned turbulent parameters for the Pathfinder had been obtained. Monin–Obukhov similarity theory for stratified surface layers has been applied to obtain the results. The values assigned to the surface roughness and the applied parameterization of the interfacial sublayer will be discussed in detail with respect to the results’ sensitivity to them. The authors have found similarities concerning the order of magnitude and qualitative behavior of Monin–Obukhov length, friction velocity, and turbulent viscous dissipation rate on Earth and on Mars. However, quantities directly related to the lower Martian atmospheric density and thermal inertia, like temperature scale and hence surface heat flux, range over different orders of magnitude. Additionally, turbulent exchanges in the first few meters have been found to be just two orders of magnitude higher than the molecular ones, whereas on Earth around five orders of magnitude separate both mechanisms.
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Criscuolo, Gennaro, Wiebke Brix Markussen, Knud Erik Meyer, Björn Palm i Martin Ryhl Kærn. "Experimental Characterization of the Heat Transfer in Multi-Microchannel Heat Sinks for Two-Phase Cooling of Power Electronics". Fluids 6, nr 2 (26.01.2021): 55. http://dx.doi.org/10.3390/fluids6020055.
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This study aims to characterize experimentally the heat transfer in micro-milled multi-microchannels copper heat sinks operating with flow boiling, in the attempt to contribute to the development of novel and high heat flux thermal management systems for power electronics. The working fluid was R-134a and the investigation was conducted for a nominal outlet saturation temperature of 30 ∘C. The microchannels were 1 cm long and covered a square footprint area of 1 cm2. Boiling curves starting at low vapor quality and average heat transfer coefficients were obtained for nominal channel mass fluxes from 250 kg/m2s to 1100 kg/m2s. The measurements were conducted by gradually increasing the power dissipation over a serpentine heater soldered at the bottom of the multi-microchannels, until a maximum heater temperature of 150 ∘C was reached. Infrared thermography was used for the heater temperature measurements, while high-speed imaging through a transparent top cover provided visual access over the entire length of the channels. The average heat transfer coefficient increased with the dissipated heat flux until a decrease dependent on hydrodynamic effects occurred, possibly due to incomplete wall wetting. Depending on the channel geometry, a peak value of 200 kW/m2K for the footprint heat transfer coefficient and a maximum dissipation of 620 W/cm2 at the footprint with a limit temperature of 150 ∘C could be obtained, showing the suitability of the investigated geometries in high heat flux cooling of power electronics. The experimental dataset was used to assess the prediction capability of selected literature correlations. The prediction method by Bertsch et al. gave the best agreement with a mean absolute percent error of 24.5%, resulting to be a good design tool for flow boiling in high aspect ratio multi-microchannels as considered in this study.
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Kohári, Zs, Gy Bognár, Gy Horváth, A. Poppe, M. Rencz i V. Székely. "Cross-Verification of Thermal Characterization of a Microcooler". Journal of Electronic Packaging 129, nr 2 (15.02.2007): 167–71. http://dx.doi.org/10.1115/1.2721089.
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The thermal behavior of a microcooler has been investigated using two different measurement methods to verify their feasibility. On the one hand structure function derived from the thermal measurements was used, while on the other hand, characterization was done with a heat-flux sensor array. The measurement sample was a square nickel plate microcooler holding 128 microchannels in radial arrangement. In our previous studies it was attached to a power transistor which was used as a dissipator and a temperature sensor. The thermal transient response to a dissipation step of the transistor was recorded in the measurement. The measured transients (cooling curves) were transformed into structure functions from which the partial thermal resistance corresponding to the cooling assembly was identified. In the current study the measurement setup was completed by a heat-flux sensor inbetween the dissipator and the microcooler to be able to verify the results extracted via structure functions. In this way we could compare the heat-transfer coefficient (HTC) values obtained from the identified thermal resistances to those calculated directly from the measured heat-flux values. Good matching of the HTC values resulting from the two different methods was found.
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Sauter, Tobias, i Stephan Peter Galos. "Effects of local advection on the spatial sensible heat flux variation on a mountain glacier". Cryosphere 10, nr 6 (24.11.2016): 2887–905. http://dx.doi.org/10.5194/tc-10-2887-2016.
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Abstract. Distributed mass balance models, which translate micrometeorological conditions into local melt rates, have proven deficient to reflect the energy flux variability on mountain glaciers. This deficiency is predominantly related to shortcomings in the representation of local processes in the forcing data. We found by means of idealized large-eddy simulations that heat advection, associated with local wind systems, causes small-scale sensible heat flux variations by up to 100 Wm−2 during clear sky conditions. Here we show that process understanding at a few observation sites is insufficient to infer the wind and temperature distributions across the glacier. The glacier-wide hourly averaged sensible heat fluxes are both over- and underestimated by up to 16 Wm−2 when using extrapolated temperature and wind fields. The sign and magnitude of the differences depend on the site selection, which is used for extrapolation as well as on the large-scale flow direction. Our results demonstrate how the shortcomings in the local sensible heat flux estimates are related to topographic effects and the insufficient characterization of the temperature advection process.
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Ji, Xuan, Nora Bailey, Daniel Fabrycky, Edwin S. Kite, Jonathan H. Jiang i Dorian S. Abbot. "Inner Habitable Zone Boundary for Eccentric Exoplanets". Astrophysical Journal Letters 943, nr 1 (1.01.2023): L1. http://dx.doi.org/10.3847/2041-8213/acaf62.
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Abstract The climate of a planet can be strongly affected by its eccentricity due to variations in the stellar flux. There are two limits for the dependence of the inner habitable zone boundary (IHZ) on eccentricity: (1) the mean stellar flux approximation ( S IHZ ∝ 1 − e 2 ), in which the temperature is approximately constant throughout the orbit, and (2) the maximum stellar flux approximation (S IHZ ∝ (1 − e)2), in which the temperature adjusts instantaneously to the stellar flux. Which limit is appropriate is determined by the dimensionless parameter Π = C BP , where C is the heat capacity of the planet, P is the orbital period, and B = ∂ Ω ∂ T s , where Ω is the outgoing long-wave radiation and T s is the surface temperature. We use the Buckingham Π theorem to derive an analytical function for the IHZ in terms of eccentricity and Π. We then build a time-dependent energy balance model to resolve the surface temperature evolution and constrain our analytical result. We find that Π must be greater than about ∼1 for the mean stellar flux approximation to be nearly exact and less than about ∼0.01 for the maximum stellar flux approximation to be nearly exact. In addition to assuming a constant heat capacity, we also consider the effective heat capacity including latent heat (evaporation and precipitation). We find that for planets with an Earthlike ocean, the IHZ should follow the mean stellar flux limit for all eccentricities. This work will aid in the prioritization of potentially habitable exoplanets with nonzero eccentricity for follow-up characterization.
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Xi, Ya, Gaoyong He, Xiang Zan, Kang Wang, Dahuan Zhu, Laima Luo, Rui Ding i Yucheng Wu. "Characterization of the Crack and Recrystallization of W/Cu Monoblocks of the Upper Divertor in EAST". Applied Sciences 13, nr 2 (5.01.2023): 745. http://dx.doi.org/10.3390/app13020745.
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The microstructure of and damage to the upper divertor components in EAST were characterized by using metallography, EBSD, and SEM. Under the synergistic effect of heat load and plasma irradiation, cracking, recrystallization, and interface debonding were found in the components of the upper divertor target. The crack propagates downward from the heat loading surface along the heat flux direction, and the crack propagation mode is an intergranular fracture. The thermal loads deposited on the edge of monoblocks raise the temperature higher than the recrystallization temperature of pure tungsten, and the microstructure changes from being in a rolled state to being recrystallized. Additionally, cracks exist in both recrystallized and rolled areas. EBSD boundary maps show that the range of the recrystallization area is determined via the heat flux distribution. The Cu/CuCrZr interface of the cooling components near the thermal loading area is debonded, and the structural integrity is destroyed.
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Legrand, Nicolas, Daniel Weisz-Patrault, Jaroslav Horský, Tomáš Luks, Nathalie Labbe, Michel Picard i Alain Ehrlacher. "Characterization of Roll Bite Heat Transfers in Hot Steel Strip Rolling and their Influence on Roll Thermal Fatigue Degradation". Key Engineering Materials 554-557 (czerwiec 2013): 1555–69. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.1555.
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A temperature sensor with a thermocouple placed at ~0.5 mm from roll surface is used in hot rolling conditions to evaluate by inverse calculation heat transfers in the roll bite. Simulation analysis in industrial hot rolling conditions with short contact lengths (e.g. short contact times) and high rolling speeds (7 m./sec.) show that the temperature sensor + inverse analysis with a high acquisition frequency (> 1000 Hz) is capable to predict with a good accuracy (5 to 10% error) the roll bite peak of temperature as well as the roll surface temperature evolution all around the roll rotation. However as heat flux is more sensitive to noise measurement, the peak of heat flux in the bite is strongly under-estimated (40% error) by the inverse calculation and thus only an average roll bite heat flux could be expected from the sensor (these simulation results will be verified with an industrial trial that is being prepared). Rolling tests on a pilot mill with low rolling speeds (from 0.3 to 1.5 m./sec.) and strip reductions varying from 10 to 40% have been performed with the temperature sensor. Analysis of the tests by inverse calculation show that at low speed (<0.5 m="" sec="" and="" large="" contact="" lengths="" reduction:="" 30="" to="" 40="" the="" roll="" bite="" peak="" of="" heat="" flux="" reconstructed="" by="" inverse="" calculation="" is="" correct="" at="" higher="" speeds="" 1="" 5="" smaller="" reduction="" :="" 10-20="" reconstruction="" incorrect:="" in="" under-estimated="" though="" its="" average="" value="" analysis="" reveals="" also="" that="" transfer="" coefficient="" htc="" sub="">roll-bite (characterizing heat transfers between roll and strip in the bite) is not uniform along the roll bite but is proportional to the local rolling pressure. Finally, based on the above results, simulations with a roll thermal fatigue degradation model in industrial hot rolling conditions show that the non uniform roll bite Heat Transfer Coefficient HTCroll-bite may have in certain rolling conditions a stronger influence on roll thermal fatigue degradation than the equivalent (e.g. same average) HTCroll-bite taken uniform along the bite. Consequently, to be realistic the roll thermal fatigue degradation model has to incorporate this non uniform HTCroll-bite.
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Wang, Z., M. M. Ren, J. X. Zhao, Z. K. Zhang, H. Wang, A. L. Hu i Y. R. Cui. "Characterization and analysis on the hemispherical point temperature uncertainty problem of mold flux with volatiles". Journal of Mining and Metallurgy, Section B: Metallurgy, nr 00 (2022): 19. http://dx.doi.org/10.2298/jmmb211209019w.
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In hemisphere point temperature (Thp) measurement of continuous casting mold flux, the evaporation of volatiles under high temperature will have a strong impact on the results. Based on the comprehensive analysis of hemisphere point method and its influencing factors, the corresponding volatile-containing mold flux and non-volatile mold flux were selected to get Thp with different heating rates. Combined with the Thp measurement and TG-DSC results, the effect of relevant factors during measuring process were analysed and the way to characterize and evaluate the effects were suggested. Furthermore, an improved method of mold flux melting point test was put forward. The results showed that for non-volatile mold flux, the temperature hysteresis has a greater effect than heat transfer delay and fractional melting. And for mold flux with volatile, the effect of evaporation is greater than other factors. Traditional hemisphere-point method is no longer suitable for the volatile mold flux. In order to get through this problem, improved methods were proposed. One is measuring Thp by traditional way, correcting the composition at the Thp, corresponding Thp with the corrected composition. Another is taking the initial composition, revising the hemispherical point temperature Thp, matching the revised Thp with the initial composition.
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Kang, Jiyuan, Fumiaki Takahashi i James S. T’ien. "In situ thermal-conductivity measurements and morphological characterization of intumescent coatings for fire protection". Journal of Fire Sciences 36, nr 5 (16.08.2018): 419–37. http://dx.doi.org/10.1177/0734904118794955.
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Thermal insulating performance and char-layer properties have been studied for water-based intumescent coatings for structural steel fire protection using a new laboratory-scale mass-loss cone apparatus. A specimen (100 × 100 mm mild steel plate; the initial coating thickness: 0.3–2.0 mm) is placed horizontally and exposed to a constant incident radiant heat flux (25, 50, or 75 kW/m2). The apparent thermal conductivity of the expanding char layer is determined in situ based on real-time measurements of the temperature distribution in the char layer and the heat flux transmitted through the char layer. Three-dimensional morphological observations of the expanded char layer are made using a computed tomographic–based analytical method. The vertical variation of the porosity of the expanded char layer is measured. The measured heat-blocking efficiency is correlated strongly with the incident heat flux, which increases the expanded char-layer thickness, and porosity for sufficiently large initial coating thicknesses (>0.76 mm). For a thin coating (0.30 mm), violent off-gassing disrupts the intumescing processes to form a consistent char layer after abrupt exposure to higher incident heat fluxes, thus resulting in lower heat-blocking efficiency. Therefore, the product application thickness must exceed a proper threshold value to ensure an adequate thermal insulation performance.
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Galipeau, James, i George Slama. "Characterization and Reliability Testing on an LTCC Transformer Operable to 250 °C". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, HITEC (1.01.2012): 000354–60. http://dx.doi.org/10.4071/hitec-2012-tha24.
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Environments prone to vibration and shocks can cause premature failure in small wire-wound transformers due to cracked cores and broken wires. These problems are only exacerbated by temperatures exceeding 200 °C where the heat causes organic compounds to age rapidly. As more electronics are used in harsh, high temperature environments, high reliability, compact transformers for use in power, filtering, and isolation applications are needed. To address this need monolithic low-temperature co-fired ceramic transformers were developed. In this work transformers were made from a low-temperature, co-fire compatible, ferrite with a Curie temperature of 350 °C. The transformers were first subjected to a 2,000 hour life test at 250 °C in which the transformer was used to charge a load capacitor once every two seconds. The inductance, resistance, core loss, and saturation flux density of the transformers were measured at various temperatures. Additional testing focused on the effect of temperature on the device's frequency profile and performance changes under thermal cycling.
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Hernández-Morales, Bernie, J. S. Téllez-Martínez i G. Sánchez-Sarmiento. "Characterization of the Heat Transfer Boundary Conditions during Cooling of a Horizontal Disk with a Water Column". Materials Science Forum 539-543 (marzec 2007): 2479–84. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.2479.
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To model the microstuctural and mechanical responses of quenched metallic components, the evolution of the thermal field must be known precisely; the latter, in turn, depends on accurate values of the thermal boundary conditions. In this work, the heat transfer boundary conditions on both sides of a stainless steel disk, held horizontally while a water column impinged on its lower surface to cool it from 850°C to room temperature, were characterized as heat flux histories which are functions of the radial coordinate. Thermal responses, measured with embedded thermocouples and a computer-controlled data acquisition system, were used to estimate the heat flux histories by solving the corresponding inverse heat conduction problem (IHCP), considering radial symmetry. The optimization problem also included the estimation of sub-areas associated with different heat extraction rates on both the lower and upper surfaces of the disk. The fluctuating interaction between the water column and the cooling disk was captured in the estimated heat flux histories. The estimated thermal boundary conditions were validated by computing the thermal response at the thermocouple locations by solving the direct heat conduction problem (DHCP) with a computer program based on the finite-element method. A good agreement between experimentally determined and computed thermal responses was observed, thus verifying the methodology employed.
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Straatman, A. G., N. C. Gallego, Q. Yu i B. E. Thompson. "Characterization of Porous Carbon Foam as a Material for Compact Recuperators". Journal of Engineering for Gas Turbines and Power 129, nr 2 (28.06.2006): 326–30. http://dx.doi.org/10.1115/1.2436562.
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Experiments are presented to quantify the convective heat transfer and hydrodynamic loss that is obtained by forcing water through blocks of porous carbon foam (PCF) heated from one side. The experiments were conducted in a small-scale water tunnel instrumented to measure the pressure drop and temperature rise of the water passing through the blocks and the base temperature and heat flux into the foam block. In comparison to similar porosity aluminum foam, the present results indicate that the pressure drop across the porous carbon foam is higher due to the large hydrodynamic loss associated with the cell windows connecting the pores, but the heat transfer performance suggests that there may be a significant advantage to using PCF over aluminum foam for extended surface convection elements in recuperators and electronic cooling devices.
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Ankener, Werner, David Böttger, Marek Smaga, Yasmine Gabi, Benjamin Strass, Bernd Wolter i Tilmann Beck. "Micromagnetic and Microstructural Characterization of Ferromagnetic Steels in Different Heat Treatment Conditions". Sensors 22, nr 12 (11.06.2022): 4428. http://dx.doi.org/10.3390/s22124428.
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The paper addresses the investigation of microstructures from AISI 52100 and AISI 4140 in hardened as well as in quenched and tempered conditions. The specimens are compared in terms of their magnetic hysteresis and their microstructural and mechanical properties. Material properties were determined by hardness, microhardness, and X-ray diffraction measurements. Two different approaches were used to characterize magnetic properties via a hysteresis frame device, aiming, on the one hand, to record the magnetic hysteresis with established proceedings by setting a constant magnetic flux and, on the other hand, by offsetting a constant field strength to facilitate reproducibility of the results with other micromagnetic measurement systems. Comparable differences in both the micromagnetic and the mechanical material properties could be determined and quantified for the specifically manufactured specimens. The sensitivity of the magnetic hysteresis and, determined from that, the relationship between magnetic flux and magnetic field strength were confirmed. It was shown that a consistent change in hysteresis shape from hardened to high temperature tempered material states develops and that this change allows the characterization of different materials without the need to adjust magnetization parameters. Repeatedly, an increase in remanence with decreasing hardness was found for both test approaches. Likewise, a decreasing coercivity and increasing maximum magnetic flux could be detected with decreasing retained austenite content. The investigated correlations should thus contribute to the calibration of comparable measurement systems through the holistic characterized specimens.
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Khamouli, Farida, Mosbah Zidani, Kaltoum Digheche, Adel Saoudi, Hend Moussi i L'Hadi Atoui. "Chemical Characterization of the Crystalline Phases in Agglomerated Fluxes and Slags for Shielded Metal Arc Welding (SMAW)". Solid State Phenomena 297 (wrzesień 2019): 151–64. http://dx.doi.org/10.4028/www.scientific.net/ssp.297.151.
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The aim of this work is to study the difference between the crystalline phases of used fluxes and obtained slags after Shielded Metal Arc Welding (SMAW). It is well known that The weld pool solidifies into the weld metal while the lighter molten flux floats on the top surface and solidifies as a slag layer that can be easily removed .The effects of individual flux ingredients as well as their interaction effects on weld metal composition have been investigated in this paper. The mass concentrations between fluxes (FA, FB and FC) and slags (SA, SB and SC) summarize the physico-chemical behavior of elements transfer between base metal, filler metal, flux and slag forming during welding of pipelines by SMAW process. The analysis of different fluxes phases and slags by X-ray diffraction allowed to detect the presence of different crystalline phases, which were formed at low temperature (T <1000°C) heat treatments, and during fluxes confection. As for the slags, the presence of new crystalline phases which have been formed at high temperatures.
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Masquere, M., P. Freton i J. J. Gonzalez. "AN INVERSE METHOD FOR THE EXPERIMENTAL CHARACTERIZATION OF AN ANODE MATERIAL - HEAT FLUX AND TEMPERATURE FIELD". High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes) 11, nr 3 (2007): 405–19. http://dx.doi.org/10.1615/hightempmatproc.v11.i3.80.
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Almoselhy, Rania I. M. "Applications of Differential Scanning Calorimetry (DSC) in Oils and Fats Research. A Review". American Research Journal of Agriculture 6, nr 1 (22.12.2020): 1–9. http://dx.doi.org/10.21694/2378-9018.20002.
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This review is designed to be a comprehensive review in a new way to help you to understand the principle and theory of Thermal Analysis with special emphasis on Differential Scanning Calorimetry (DSC) as a new fast-growing and important technique used for authentication, characterization and detecting adulterations of oils and fats. DSC is a powerful instrument that measures the energy absorbed or released as a function of time or a controlled temperature profile. The sensor of the DSC is the heat flux plate which is designed to give superior performance and rugged reliability. The heat flux plate is capable of measuring small energy changes over the entire temperature range. Examples of measurements with DSC are Oxidative Stability, Melting Enthalpy, Glass Transition, Heat of Crystallization, Purity Determination and Heat Capacity. DSC can be used as a rapid method for assessment of oxidative stability, prediction of shelf life and evaluation of the quality of edible oils during refining. DSC holds a potential to be used as the reliable and reproducible technique for the detection of adulteration of animal body fat added in ghee individually and in combination of vegetable oil. DSC method is faster, require less sample size and no chemicals or solvents compared to other conventional, modern oxidative stability methods and conventional shelf life estimation.
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Roberts, J. Brent, Franklin R. Robertson, Carol A. Clayson i Michael G. Bosilovich. "Characterization of Turbulent Latent and Sensible Heat Flux Exchange between the Atmosphere and Ocean in MERRA". Journal of Climate 25, nr 3 (1.02.2012): 821–38. http://dx.doi.org/10.1175/jcli-d-11-00029.1.
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Abstract Turbulent fluxes of heat and moisture across the atmosphere–ocean interface are fundamental components of the earth’s energy and water balance. Characterizing both the spatiotemporal variability and the fidelity of these exchanges of heat and moisture is critical to understanding the global water and energy cycle variations, quantifying atmosphere–ocean feedbacks, and improving model predictability. This study examines the veracity of the recently completed NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA) product in terms of its turbulent surface fluxes. This assessment employs a large dataset of directly measured turbulent fluxes as well as other turbulent surface flux datasets. The spatial and temporal variability of the surface fluxes are examined in terms of their annual-mean climatologies, their seasonal covariability of near-surface bulk parameters, and their representation of extremes. The impact of data assimilation on the near-surface parameters is assessed through evaluation of the incremental analysis update tendencies. It is found that MERRA turbulent surface fluxes are relatively accurate for typical conditions but have systematically weak vertical gradients in moisture and temperature and a weaker covariability between the near-surface gradients and wind speed than found in observations. This results in an underestimate of the surface latent and sensible heat fluxes over the western boundary current and storm-track regions. The assimilation of observations generally acts to bring MERRA closer to observational products by increasing moisture and temperature near the surface and decreasing the near-surface wind speeds.
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Schmidt, C., M. Bayer-Raich i M. Schirmer. "Characterization of spatial heterogeneity of groundwater-stream water interactions using multiple depth streambed temperature measurements at the reach scale". Hydrology and Earth System Sciences Discussions 3, nr 4 (10.07.2006): 1419–46. http://dx.doi.org/10.5194/hessd-3-1419-2006.
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Abstract. Streambed temperatures can be easily, accurately and inexpensively measured at many locations. We obtained 140 vertical streambed temperature profiles along a 220 m section of a small artificial stream to characterize patterns of groundwater-stream water interaction with a high spatial resolution. Groundwater temperature at a sufficient depth remains nearly constant while stream water temperatures vary seasonally and diurnally. In summer, streambed temperatures of groundwater discharge zones are relatively colder than downwelling zones of stream water. Assuming vertical flow in the streambed, the observed temperatures can be correlated to the magnitude of water fluxes. The water fluxes can then be estimated by applying a simple analytical solution of the heat diffusion-advection equation to the observed vertical temperature profiles. The calculated water fluxes through the streambed ranged between 10.0 Lm−2 d−1 of stream water entering the streambed and 455.0 Lm−2 d−1 of groundwater discharging to the stream. The investigated reach was dominated by groundwater discharge with two distinct high discharge locations accounting for 50% of the total flux on 20% of the reach length.
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Schmidt, C., M. Bayer-Raich i M. Schirmer. "Characterization of spatial heterogeneity of groundwater-stream water interactions using multiple depth streambed temperature measurements at the reach scale". Hydrology and Earth System Sciences 10, nr 6 (16.11.2006): 849–59. http://dx.doi.org/10.5194/hess-10-849-2006.
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Abstract. Streambed temperatures can be easily, accurately and inexpensively measured at many locations. To characterize patterns of groundwater-stream water interaction with a high spatial resolution, we measured 140 vertical streambed temperature profiles along a 220 m section of a small man-made stream. Groundwater temperature at a sufficient depth remains nearly constant while stream water temperatures vary seasonally and diurnally. In summer, streambed temperatures of groundwater discharge zones are relatively colder than downwelling zones of stream water. Assuming vertical flow in the streambed, the observed temperatures are correlated to the magnitude of water fluxes. The water fluxes are then estimated by applying a simple analytical solution of the heat conduction-advection equation to the observed vertical temperature profiles. The calculated water fluxes through the streambed ranged between 455 Lm−2 d−1 of groundwater discharging to the stream and approximately 10 Lm−2 d−1 of stream water entering the streambed. The investigated reach was dominated by groundwater discharge with two distinct high discharge locations accounting for 50% of the total flux on 20% of the reach length.
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DAHAMNI, S., A. BENAROUS i P. A. G. PILOTO. "Towards a thermal characterization of a firefighter's protective cloth-ing". Mechanics 26, nr 5 (20.10.2020): 435–41. http://dx.doi.org/10.5755/j01.mech.26.5.22532.
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In the present work, an unsteady analysis is carried out for the thermal characterisation of a firefighter protective clothing. Coupled radiative and conduction heat transfers are considered inside the clothing with a focus on the thermal level on the first skin layer. The protective garment is modelled as a 1D solid medium, featuring three layers of tissues, separated by several air-gaps. A parametric analysis is performed in the aim to predict the effect of conductive and radiative tissue's properties fluctuation on the first skin's layer temperature. The thermal balance equations are written in a finite element (FE) formulation and solved using the COMSOL Multiphysics® software. Predictions were provided for the temperature and heat flux distributions in the fabric, skin, and air-gap as a function of time, as well as the time to receive skin burn injuries. The results obtained were compared with stationary 2-D calculations, and faced to unsteady simulations, based on the finite volume method. A 50% relative reduction in the absorptivity of the skin (in the case of wearing a fine knitted fabric) makes it possible to reduce the surface temperature of the skin to a tolerable value.
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Tarakanova, V. A., D. P. Kasymov, O. V. Galtseva i N. V. Chicherina. "Experimental characterization of firebrand ignition of some wood building materials". Bulletin of the Karaganda University. "Physics" Series 100, nr 4 (30.12.2020): 14–21. http://dx.doi.org/10.31489/2020ph4/14-21.
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Paper presents investigation on behaviour of wood construction material samples (plywood, oriented strand board, chipboard) in laboratory conditions as a result of a heat flux effect from naturally occurring flaming and glowing firebrands. The data of comparing ignition delay time of pine wood and wood-based construction materials (plywood, oriented strand board, chipboard) depending on the size and quantity of firebrands, initial temperature of samples, as well as the presence of air flow in firebrands falling zone is obtained. Ignition probability and conditions of wood construction materials as a result of the thermal effect of flaming and glowing pine firebrands are also studied. The obtained data allowed one to judge that according to chosen experimental parameters, the ignition time decreased with increasing air flow, as well as with an increase in the size and number of particles. It was experimentally confirmed that particle size plays a significant role in igniting of building structure. If the characteristic particle size is less than a certain characteristic value, which can be defined as the ratio of its volume to the surface area in contact with wood, then ignition mode with an abrupt maximum of temperature near phase boundary is not appear.
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WANG, XINCHANG, JIANGUO ZHANG, TAO ZHANG, BIN SHEN i FANGHONG SUN. "SIMULATION OPTIMIZATION OF THE HEAT TRANSFER CONDITIONS IN HFCVD DIAMOND FILM GROWTH INSIDE HOLES". Surface Review and Letters 20, nr 03n04 (sierpień 2013): 1350031. http://dx.doi.org/10.1142/s0218625x13500315.
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Finite volume method (FVM) is adopted in the present investigation to simulate the temperature and reactant gas velocity distributions in hot filament chemical vapor deposition (HFCVD) diamond film growth inside holes, using a detailed 3D computational model well in accordance with the actual reactor. The influences of the heat transfer characteristic of the substrate and the auxiliary heat transfer conditions are firstly studied by control variable method (CVM), including the thermal conductivity of the substrate k, the size of the red bronze support block V(x × y × z), the cooling water flux Qw, the reactant gas flux Qg, the arrangement of the gas outlets A out and the emissivities of the different solid surfaces ϵ. Thereafter, the substrate temperature data measured in the actual HFCVD reactor with three chosen groups of parameters are compared with those obtained from the simulations, presenting similar trends and small deviations less than 5%. Moreover, the auxiliary heat transfer conditions are optimized for both the WC- Co and SiC substrates based on the simulation and measurement results, and corresponding deposition parameters are also determined. Furthermore, HFCVD diamond films are deposited on the inner surfaces of both the substrates under the optimized conditions. The characterization results show that high-quality diamond films with uniform thickness and fine-faceted crystals are obtained, indicating that this optimization method focusing on the heat transfer conditions is feasible and correct.
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Sadiq, Muhammad Adil, i Tasawar Hayat. "Characterization of Marangoni Forced Convection in Casson Nanoliquid Flow with Joule Heating and Irreversibility". Entropy 22, nr 4 (10.04.2020): 433. http://dx.doi.org/10.3390/e22040433.
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The Marangoni forced convective inclined magnetohydrodynamic flow is examined. Marangoni forced convection depends on the differences in surface pressure computed by magnetic field, temperature, and concentration gradient. Casson nanoliquid flow by an infinite disk is considered. Viscous dissipation, heat flux, and Joule heating are addressed in energy expressions. Thermophoresis and Brownian motion are also examined. Entropy generation is computed. The physical characteristics of entropy optimization with Arrhenius activation energy are discussed. Nonlinear PDE’s are reduced to highly nonlinear ordinary systems with appropriate transformations. A nonlinear system is numerically computed by the NDSolve technique. The salient characteristics of velocity, temperature, concentration, entropy generation, and Bejan number are explained. The computational results of the heat-transfer rate and concentration gradient are examined through tables. Velocity and temperature have reverse effects for the higher approximation of the Marangoni number. Velocity is a decreasing function of the Casson fluid parameter. Temperature is enhanced for higher radiation during reverse hold for concentration against the Marangoni number. The Bejan number and entropy generation have similar effects for Casson fluid and radiation parameters. For a higher estimation of the Brinkman number, the entropy optimization is augmented.
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Inagaki, S., N. Tamura, K. Ida, K. Tanaka, Y. Nagayama, K. Kawahata, S. Sudo, K. Itoh, S.-I. Itoh i A. Komori. "Characterization of bifurcation induced by long distance correlation between heat flux and temperature gradient in toroidal plasmas". Plasma Physics and Controlled Fusion 52, nr 7 (26.05.2010): 075002. http://dx.doi.org/10.1088/0741-3335/52/7/075002.
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Chi, Ri-Guang, i Seok-Ho Rhi. "Oscillating Heat Pipe Cooling System of Electric Vehicle’s Li-Ion Batteries with Direct Contact Bottom Cooling Mode". Energies 12, nr 9 (5.05.2019): 1698. http://dx.doi.org/10.3390/en12091698.
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Recently, the use of electrical vehicles has abruptly increased due to environmental crises. The high energy density of lithium-ion batteries is their main advantage for use in electric vehicles (EVs). However, the thermal management of Li-ion batteries is a challenge due to the poor heat resistance of Lithium ions. The performance and lifetime of lithium ion batteries are strongly affected by the internal operating temperature. Thermal characterization of battery cells is very important to ensure the consistent operation of a Li-ion battery for its application. In the present study, the OHP (Oscillating Heat Pipe) system is proposed as a battery cooling module, and experimental verification was carried out. OHP is characterized by a long evaporator section, an extremely short condenser section, and almost no adiabatic section. Experimental investigations were conducted using various parameters such as the filling ratio, orientation, coolant temperature, and heat flux. Average temperature of the heater’s surface was maintained at 56.4 °C using 14 W with 25 °C coolant water. The experimental results show that the present cooling technology basically meets the design goal of consistent operation.
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Denager, Tanja, Torben O. Sonnenborg, Majken C. Looms, Heye Bogena i Karsten H. Jensen. "Point-scale multi-objective calibration of the Community Land Model (version 5.0) using in situ observations of water and energy fluxes and variables". Hydrology and Earth System Sciences 27, nr 14 (31.07.2023): 2827–45. http://dx.doi.org/10.5194/hess-27-2827-2023.
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Abstract. This study evaluates water and energy fluxes and variables in combination with parameter optimization of version 5 of the state-of-the-art Community Land Model (CLM5) land surface model, using 6 years of hourly observations of latent heat flux, sensible heat flux, groundwater recharge, soil moisture and soil temperature from an agricultural observatory in Denmark. The results show that multi-objective calibration in combination with truncated singular value decomposition and Tikhonov regularization is a powerful method to improve the current practice of using lookup tables to define parameter values in land surface models. Using measurements of turbulent fluxes as the target variable, parameter optimization is capable of matching simulations and observations of latent heat, especially during the summer period, whereas simulated sensible heat is clearly biased. Of the 30 parameters considered, the soil texture, monthly leaf area index (LAI) in summer, stomatal conductance and root distribution have the highest influence on the local-scale simulation results. The results from this study contribute to improvements of the model characterization of water and energy fluxes. This work highlights the importance of performing parameter calibration using observations of hydrologic and energy fluxes and variables to obtain the optimal parameter values for a land surface model.
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Wheler, Brett A., i Gwenn E. Flowers. "Glacier subsurface heat-flux characterizations for energy-balance modelling in the Donjek Range, southwest Yukon, Canada". Journal of Glaciology 57, nr 201 (2011): 121–33. http://dx.doi.org/10.3189/002214311795306709.
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AbstractWe apply a point-scale energy-balance model to a small polythermal glacier in the St Elias Mountains of Canada in order to investigate the applicability and limitations of different treatments of the glacier surface temperature and subsurface heat flux. These treatments range in complexity from a multilayer subsurface model that simulates snowpack evolution, to the assumption of a constant glacier surface temperature equal to 0°C. The most sophisticated model includes dry densification of the snowpack, penetration of shortwave radiation into the subsurface, internal melting, refreezing of percolating meltwater and generation of slush layers. Measurements of subsurface temperature and surface lowering are used for model validation, and highlight the importance of including subsurface penetration of shortwave radiation in the model. Using an iterative scheme to solve for the subsurface heat flux as the residual of the energy-balance equation results in an overestimation of total ablation by 18%, while the multilayer subsurface model underestimates ablation by 6%. By comparison, the 0°C surface assumption leads to an overestimation of ablation of 29% in this study where the mean annual air temperature is about −8°C.
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Mertens, Robert G., Louis Chow, Kalpathy B. Sundaram, R. Brian Cregger, Daniel P. Rini, Louis Turek i Benjamin A. Saarloos. "Spray Cooling of IGBT Devices". Journal of Electronic Packaging 129, nr 3 (18.05.2007): 316–23. http://dx.doi.org/10.1115/1.2753937.
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The popularity and increased usage of insulated gate bipolar transistors (IGBTs) in power control systems have made the problem of cooling them a subject of considerable interest in recent years. In this investigation, a heat flux of 825W∕cm2 at the die was achieved when air-water spray cooling was used to cool IGBTs at high current levels. The junction temperature of the device was measured accurately through voltage-to-temperature characterization. Results from other cooling technologies and other spray cooling experiments were reviewed. A discussion of electrical power losses in IGBTs, due to switching and conduction, is included in this paper. Experiments were conducted on 19 IGBTs, using data collection and software control of the test set. Three types of cooling were explored in this investigation: single-phase convection with water, spray cooling with air-water and spray cooling with steam-water. The results of these experiments show clear advantages of air-water spray cooling IGBTs over other cooling technologies. The applications of spray cooling IGBTs are discussed in open (fixed) and closed (mobile) systems. Current and heat flux levels achieved during this investigation could not have been done using ordinary cooling methods. The techniques used in this investigation clearly demonstrate the superior cooling performance of air-water spray cooling over traditional cooling methods.
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Sabri, Firouzeh, Stephen W. Allison, Makunda Aryal, Josh Collins i Howard Bell. "Thermal and optical characterization of up-converting thermographic phosphor polymer composite films". MRS Advances 3, nr 60 (2018): 3489–94. http://dx.doi.org/10.1557/adv.2018.486.
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AbstractUp-converting thermographic phosphors are of significant interest due to specific advantages for temperature measurement applications over traditional contact-based methods. Typically, infrared excitation stimulates visible fluorescence only from the target phosphor and not the surrounding medium. This is in contrast to ultraviolet excitation which may also produce interfering luminescence from cells and other biological tissue in the vicinity, for instance. When traversing a material, usually infrared losses due to scattering and absorption are less than for ultraviolet wavelengths. An example is human skin. This investigation follows logically from earlier efforts incorporating thermographic phosphors into elastomers and aerogels and their function as a reusable temperature sensor has been previously demonstrated by the authors. Layered phosphor/PDMS/aerogel composites are also currently under investigation by the authors for heat flux sensing. For maximum utility and understanding; physical, optical and thermal properties are characterized over a wide range of temperatures. Y2O2S:Yb,Er and La2O2S:Yb,Er up-converting phosphor composites with a fixed doping concentration were synthesized for this study and fully characterized as a function of temperature. The excitation/ emission characteristics of the powder alone and the prepared composites were investigated between -50 °C and +200 °C in an environmental chamber and the decay behavior of each sample type was measured. Here, the authors report on decay behavior and emission intensity of the PDMS composites as a function of temperature. Results were compared with powder –only parameters and are reported here.
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Alghfeli, Abdalla, Mostafa Abuseada i Timothy S. Fisher. "Solar-thermal cold-wall chemical vapor deposition reactor design and characterization for graphene synthesis". Journal of Vacuum Science & Technology B 40, nr 6 (grudzień 2022): 064205. http://dx.doi.org/10.1116/6.0002091.
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Manufacturing processes are often highly energy-intensive, even when the energy is primarily used for direct heating processes. The required energy tends to derive from local utilities, which currently employ a blend of sources ranging from fossil fuels to renewable wind and solar photovoltaics, among others, when the end manufacturing need is thermal energy. Direct solar-thermal capture provides a compelling alternative that utilizes renewable energy to reduce greenhouse gas emissions from industrial processes, but one that has rarely been employed to date. In this study, a 10 kW[Formula: see text] custom-built high flux solar simulator (HFSS) that closely approximates the solar spectrum produces a heat flux distribution with an adjustable peak between 1.5 and 4.5 MW/m[Formula: see text]. The HFSS system is coupled to a cold-wall chemical vapor deposition (CVD) system that is equipped to automate graphene synthesis while providing safe operation, precise control, and real-time monitoring of process parameters. A numerical heat transfer model of a thin copper substrate is derived and validated to compute the substrate’s temperature profile prior to the synthesis process. The peak substrate temperature is correlated to the HFSS supply current and vacuum pressure, as it serves as a critical design parameter during graphene synthesis. We report the synthesis of high-quality graphene films on copper substrates with an average Raman peak intensity ratio [Formula: see text] of 0.17. Backscattered electron microscopy reveals a characteristic grain size of 120 [Formula: see text]m, with an area ratio of 16 when compared to that of low-quality graphene on copper. The reported solar-thermal CVD system demonstrates the ability to produce a high-value product, namely, graphene on copper, directly from a renewable energy resource with process control and automation that enables synthesis under a variety of conditions.
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Bouaziz, Amina Manel, M. N. Bouaziz i A. Aziz. "Influences of Zero Mass Flux and Active Conditions on the Predictions of Double Dispersion and Double Diffusive Boundary Layer in Darcy/Non Darcy Nanofluid Flow". International Journal of Engineering Research in Africa 57 (9.11.2021): 49–65. http://dx.doi.org/10.4028/www.scientific.net/jera.57.49.
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Free convective of nanofluid inside dispersive porous medium adjacent to a vertical plate under the effects of the zero mass nanoparticles flux condition and the thermal and solutal dispersions is studied. Buongiorno's model revised is used considering Darcy and non Darcy laminar flows, and isothermal or convective flux outer the wall. Dimensionless governing equations formulated using velocity, temperature, concentration and nanoparticle volume fraction have been solved by finite difference method that implements the 3-stage Lobatto collocation formula. The numerical data obtained with semi or full dispersions cases are compared to predictions made using the non dispersive porous medium. Taking into account the dispersions, the influence of the zero mass nanoparticles flux condition is examined to test the validity of the control active nanoparticle assumption. It is found mainly that the thermal transfers can reach more than 100% in connection with the case where of a semi-dispersion of the porous medium is applied. Realistic condition, i.e. zero mass flux should be addressed for the heat transfer rate rather than the mass transfer rate, discovered markedly different to the active condition. This signifies the importance of considering the zero nanoparticles mass flux and dispersions in the performance characterization of nanofluid flow in porous media.
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Carmele, Dagmar, Thomas Rieger, Klaus Herrmann, Stephan Meyer, Thomas Lippmann, Andreas Stark, Wolfgang Bleck i Uwe Klemradt. "Very Hard Synchrotron X-Ray Radiation as an Advanced Characterization Method Applied to Advanced High-Strength Steels". Advanced Materials Research 409 (listopad 2011): 660–65. http://dx.doi.org/10.4028/www.scientific.net/amr.409.660.
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Innovative steel materials of the third generation of advanced high-strength steel (AHSS) are based on complex multiphase microstructures on a submicron scale, which are adjusted in a heat treatment procedure. Established methods for microstructural characterization are usually applied after the heat treatment process (ex-situ) at room temperature and comprise amongst others X-ray analysis based on laboratory tubes with photon energies of several keV. The corresponding penetration depths are on the micron scale. Additionally, the results may be affected by the metallographic preparation process. Using very hard synchrotron X-ray radiation with photon energies of up to 100 keV, penetration depths in the millimetre range are realized and macroscopic volumes (mm³) can be investigated. Furthermore the photon flux of synchrotron sources is several orders of magnitude higher compared to laboratory tubes. Consequently in-situ measurements during a heat treatment process can be performed. Using the example of the standardized multiphase TRIP steel HCT690T, a microstructural investigation with high energy synchrotron X-ray radiation is discussed and compared to established diffraction methods using Co-and Cu-Kα-radiation. In-situ diffraction measurements during a heat treatment are exemplarily shown.
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Soares, Willames De Albuquerque. "Impact of spineless cactus cultivation (O. Ficus-indica) on the thermal characteristics of soil". Ambiente e Agua - An Interdisciplinary Journal of Applied Science 13, nr 1 (16.02.2018): 1. http://dx.doi.org/10.4136/ambi-agua.2148.
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Temperature is a fundamentally important factor for understanding the physical, chemical, and biological processes that occur in soil. However, there are few studies in the Brazilian semiarid zone that seek to understand how soil degradation affects its thermal characteristics. The objective of this study was to evaluate the influence of cultivation techniques on the thermal characterization of soil, using the model proposed by Johansen. The study was conducted in the Agreste region of the state of Pernambuco, Brazil on two plots of land, one with native vegetation (Caatinga) and the other with spineless cactus (O. ficus - indica). It was observed that the procedures used to prepare the soil for cultivation of spineless cactus caused a reduction in the capacity to transmit the surface temperature to the interior of the soil. Changes in the physical properties of the soil required for cultivation resulted in a reduction in the average value of the volumetric heat capacity of about 22%; an increase of approximately 5% in the average volumetric heat capacity and a 26% increase in the thermal diffusivity of the soil, as well as a reduction of approximately 50% in the heat flux from the surface of the soil.
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Aljundi, K., A. Vieira, J. Maranha, J. Lapa i R. Cardoso. "Effects of temperature, test duration and heat flux in thermal conductivity measurements under transient conditions in dry and fully saturated states". E3S Web of Conferences 195 (2020): 04007. http://dx.doi.org/10.1051/e3sconf/202019504007.
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In shallow geothermal energy systems (SGES) thermal conduction can be considered the dominant process in the heat transfer between the primary circuit (borehole heat exchanger or thermoactive geostructure) and the surrounding ground. Thus, a proper characterization of soil thermal properties, namely of its thermal conductivity, is mandatory for evaluating this energy exchange. There are difficulties associated to the assessment of soil thermal conductivity by laboratory methods related, among other factors, to the samples’ quality and to the measuring method itself. The purpose of this work is to analyse the effect of changing test control parameters in thermal conductivity measurements in transient conditions by means of a high accuracy thermal probe in both dry and fully saturated states. In order to eliminate potential measurements’ deviations and errors due to sample variability the same reconstituted samples were used several times. In each condition the sand samples were systematically tested under different ambient temperatures (10ºC, 20ºC, and 40ºC) controlled by means of a climatic chamber. The effects of changing the tests heating time and imposed thermal fluxes were also analysed.
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Poignand, Gaelle, Come Olivier i Guillaume Penelet. "Test-bench for the experimental characterization of porous material used in thermoacoustic refrigerators". Journal of the Acoustical Society of America 152, nr 5 (listopad 2022): 2804–15. http://dx.doi.org/10.1121/10.0015051.
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The design of thermoacoustic coolers involves an adequate modeling of the thermoacoustic core's performance, which requires, in particular, a precise knowledge of their thermo-physical properties. Materials such as wire mesh stacks, foams, or compressed fibrous media are hard to describe, and their thermo-physical properties are rarely well enough quantified. Moreover, the classical linear thermoacoustic theory is not sufficient to accurately describe the performance of these materials. This paper deals with the experimental performance characterization of various materials for thermoacoustic heat pumping. A dedicated experimental test-bench has been specially developed, which is composed of two loudspeakers placed at opposite ends of a waveguide containing the porous material and a feedback loop to control the acoustic field in the porous material. Its originality is attributable to the possibility of identifying the optimal acoustic field, specific to each material, that maximizes the temperature difference at the ends of the material. Moreover, a specific protocol is implemented to access and compare the thermoacoustic heat flux through various materials at these optimal acoustic fields. Comparison of the experimental and theoretical results shows a reasonable agreement.
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Wang, Keyong, Kambiz Vafai i Dazhong Wang. "Analytical characterization of gaseous slip flow and heat transport through a parallel-plate microchannel with a centered porous substrate". International Journal of Numerical Methods for Heat & Fluid Flow 26, nr 3/4 (3.05.2016): 854–78. http://dx.doi.org/10.1108/hff-09-2015-0364.
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Purpose – The purpose of this paper is to analytically perform gaseous slip flow and heat transfer analysis within a parallel-plate microchannel partially filled with a centered porous medium under local thermal non-equilibrium (LTNE) condition. Heat transfer of gaseous flow in a porous microchannel is analytically studied. Energy communication at the porous-fluid interface is considered by two approaches: the gas rarefaction negatively impacts the heat transfer performance, and the optimum ratio of porous thickness is found to be around 0.8. Design/methodology/approach – Both Models A and B are utilized to consider the heat flux splitting for the fluid and solid phases at the porous-fluid interface. Findings – Analytical solutions for the fluid and solid phase temperature distributions and the Nusselt number are derived. In the no-slip flow limit, the present analytical solutions are validated by the partially and fully filled cases available in the literature. Research limitations/implications – The continuum flow (no-slip flow) is only a special case of the slip flow. Meanwhile, the effects of pertinent parameters on the heat transfer are also discussed. Practical implications – A survey of available literature mentioned above indicates a shortage of information for slip flow and heat transfer in partially filled porous systems. The main objective of the present study is to investigate the slip flow and heat transfer characteristics for forced convection through a microchannel partially filled with a porous medium under LTNE condition. The porous substrate is placed at the center of the microchannel. Analytical solutions for the temperature distributions of the fluid and solid phases and the Nusselt number at the microchannel wall are obtained. Originality/value – Heat transfer of gaseous flow in a porous microchannel is analytically studied. Energy communication at the porous-fluid interface is considered by two approaches: the gas rarefaction negatively impacts the heat transfer performance, and the optimum ratio of porous thickness is found to be around 0.8. Gaseous slip flow and heat transfer analysis is analytically performed within a parallel-plate microchannel partially filled with a centered porous medium under LTNE condition. Analytical solutions for the fluid and solid phase temperature distributions and the Nusselt number are derived for the first time. The effects of pertinent parameters on the heat transfer are also discussed. Compared with the results obtained for the continuum flow regime, the gas rarefaction negatively impacts the heat transfer efficiency and has little influence on the optimal porous thickness.
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Wasim, M. F., S. Ali, M. W. Ashraf, A. Rafique, J. Ahmad, M. I. Akhter, A. Qadeer, S. Tayyaba i Z. Ahmad. "Synthesis and characterization Al2O3-ZrO2 bio-nanostructures with sintering effect, residual and thermally stable analysis". Digest Journal of Nanomaterials and Biostructures 16, nr 3 (lipiec 2021): 1163–71. http://dx.doi.org/10.15251/djnb.2021.163.1163.
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The thermal stability of nano composite materials is the important aspect of the modern era. In the advance modern devices, the nanostructures and nano composite material are used for the biological and other applications. The aluminum oxide is the most prominent oxides and composite at nano scale that show different structures, electrical and thermal properties which make it useful in different applications. Sol-Gel technique was used for synthesis to grow these nanostructures of Al2O3-ZrO2. Thermal stability was achieved and thermo-gravimetric (TGA) graphical analysis of synthesized material was performed. Size, phase and structure validation about the productive material was studied by X-Ray diffraction powder technique. Reaction completion and idea about annealing temperature of the synthesized material had pointed out by DSC-TGA (SDT) graphical peaks. Effect of the temperatures with equal variation from 500 0C, 700 0C, 900 0C and 1100 0C was performed to achieve the target thermal stability. Thermal analysis was also conducted in ANSYS workbench to visualize the thermal distributes like heat flux through the material. Optical properties such as band gap variation with temperature were studied by UV-vis analysis. Fourier transform infrared (FTIR) analysis was also performed. This work provides useful information related to nanostructures with sintering effect, residual and thermally stable analysis.
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Blackburn, Hannah, Andrea Vecchiotti, Joseph Vignola, Diego Turo i Teresa J. Ryan. "Using machine learning to identify and assess cloud coverage". Journal of the Acoustical Society of America 153, nr 3_supplement (1.03.2023): A328. http://dx.doi.org/10.1121/10.0019026.
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This machine learning project is part of ongoing longitudinal long distance atmospheric acoustic propagation research being conducted at the East Carolina University Outer Banks campus in Wanchese, NC. The overall project seeks to connect changes in the atmosphere by taking concurrent acoustic and meteorological readings and relating them to differences in sound propagation. Wide angle images of the sky are used to correlate cloud cover with concurrent near-surface temperature gradient measurements. The camera is mounted on a mast that houses the temperature logger array. Images are imported, segmented, and labeled in MATLAB and used as both a training and test image set. The results of this project enable more accurate characterization of cloud cover. This information supplements knowledge of heat flux between ground and the atmosphere which in turn supports improved modeling of long distance sound propagation.
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Ju, Lei, Jiangjiang Zhang, Cheng Chen, Laosheng Wu i Lingzao Zeng. "Water flux characterization through hydraulic head and temperature data assimilation: Numerical modeling and sandbox experiments". Journal of Hydrology 558 (marzec 2018): 104–14. http://dx.doi.org/10.1016/j.jhydrol.2018.01.008.
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de Rubeis, Tullio, Giovanni Pasqualoni, Domenica Paoletti i Dario Ambrosini. "Thermal Characterization of Different Insulating Materials via Experimental Analysis in a Guarded Hot Box". Tecnica Italiana-Italian Journal of Engineering Science 65, nr 2-4 (30.07.2021): 230–35. http://dx.doi.org/10.18280/ti-ijes.652-414.
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The thermal characterization of building envelope materials is a crucial phase in understanding the building energy performance, and it is commonly evaluated through the thermal transmittance, often synthetically indicated as U-value. There are several ways to experimentally assess the U-value of insulating materials and multi-layers systems, usually defined by means of experimental in-situ heat flux measurements, where, however, a considerable variation of the boundary conditions may occur, making the measurement difficult. In this work, the experimental thermal characterization of different insulating materials applied to an X-lam wall is presented. The analysis is carried out using a Guarded Hot Box, which allowed to reproduce real, repeatable, and controlled operating conditions. Two different insulating materials were selected: expanded polystyrene (EPS) with graphite and hemp. The experimental tests were carried out by imposing a temperature difference reproducing the common operating conditions (0°C in cold chamber and 20°C in hot chamber). Steady-state conditions (constant temperature in the chambers) have been imposed to determine the thermal properties of the multi-layer systems. The tests, lasted 72 hours each, showed U-values equal to 0.15 W/m2K ± 3.1% for EPS with graphite and 0.19 W/m2K ± 3.1% for hemp.
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Mendioroz, Arantza, Alazne Castelo, Ricardo Celorrio i Agustín Salazar. "Vertical Cracks Excited in Lock-in Vibrothermography Experiments: Identification of Open and Inhomogeneous Heat Fluxes". Sensors 22, nr 6 (17.03.2022): 2336. http://dx.doi.org/10.3390/s22062336.
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Lock-in vibrothermography has proven to be very useful to characterizing kissing cracks producing ideal, homogeneous, and compact heat sources. Here, we approach real situations by addressing the characterization of non-compact (strip-shaped) heat sources produced by open cracks and inhomogeneous fluxes. We propose combining lock-in vibrothermography data at several modulation frequencies in order to gather penetration and precision data. The approach consists in inverting surface temperature amplitude and phase data by means of a least-squares minimization algorithm without previous knowledge of the geometry of the heat source, only assuming knowledge of the vertical plane where it is confined. We propose a methodology to solve this ill-posed inverse problem by including in the objective function penalty terms based on the expected properties of the solution. These terms are described in a comprehensive and intuitive manner. Inversions of synthetic data show that the geometry of non-compact heat sources is identified correctly and that the contours are rounded due to the penalization. Inhomogeneous smoothly varying fluxes are also qualitatively retrieved, but steep variations of the flux are hard to recover. These findings are confirmed by inversions of experimental data taken on calibrated samples. The proposed methodology is capable of identifying heat sources generated in lock-in vibrothermography experiments.
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MacKellar, Mellissa C., Hamish A. McGowan i Stuart R. Phinn. "Spatial Heterogeneity of Air–Sea Energy Fluxes over a Coral Reef—Heron Reef, Australia". Journal of Applied Meteorology and Climatology 51, nr 7 (lipiec 2012): 1353–70. http://dx.doi.org/10.1175/jamc-d-11-0120.1.
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AbstractThe thermal environment of a coral reef is moderated by complex interactions of air–sea heat and moisture fluxes, local to synoptic-scale weather and reef hydrodynamics. Measurements of air–sea energy fluxes over coral reefs are essential to understanding the reef–atmosphere processes that underpin coral reef environmental conditions such as water temperature, cloud, precipitation, and local winds (such as during coral bleaching events). Such measurements over coral reefs have been rare, however, and the spatial heterogeneity of surface–atmosphere energy exchanges due to the different geomorphic and biological zones on coral reefs has not been captured. Accordingly, the heterogeneity of coral reefs with regard to substrate, benthic communities, and hydrodynamic processes has not been considered in the characterization of the surface radiation budget and energy balance of coral reefs. Here, the first concurrent in situ eddy covariance measurements of the surface energy balance and radiation transfers over different geomorphic zones of a coral reef are presented. Results showed differences in radiation transfers and sensible and latent heat fluxes over the reef, with higher Bowen ratios over the shallow reef flat zone. The energy flux divergence between sites increased with wind speed and during unstable, southeasterly trade winds with the net flux of heat being positive and negative over different geomorphic zones. The surface drag coefficient at measurement height ranged from 1 × 10−3 to 2.5 × 10−3, with no significant difference between sites. Results confirm that spatial variation in radiation and air–reef–water surface heat and moisture fluxes occurs across a lagoonal platform reef in response to local meteorological conditions, hydrodynamics, and benthic–substrate cover.
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Younes, Rassim, Youcef Mouadji, Houcine Touati i Mohand Amokrane Bradai. "Modeling Temperature of Contact Generated in Coatings of Pure Alumina Ceramic onto Low Carbon Steel Type 1.0060 Obtained by the Thermal Spraying Process". Advanced Materials Research 1178 (25.07.2023): 59–71. http://dx.doi.org/10.4028/p-snm0zd.
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In previous research problem statement occur in hardness to reach the thermal flux between surfaces during movement. The aim of the present investigation has been conducted to study the thermal behavior of ceramic Al2O3 (AL-99) coated on a low carbon steel type 1.0060 by using a thermal flame spray technique. The key methods used is microstructural characterization and comparing between experimental data record and numerical program.SEM showed that the Al2O3 coatings have a dense microstructure, lamellar morphology and complex of several phases. The XRD analysis of the coating after the spray showed a majority phase of α -Al2O3 rhombohedral structure and secondary phase of γ-Al2O3 orthorhombic structure. The experimental data recorded From wear indicate two step, first one corresponds to the phase of accommodation between surfaces (samples/ disc), the contact temperature gradually increases to a value Of 75 °C for both pairs, the second step , we could remark from experimental and numerical simulation, it reach 95°C for experimental test and 85 for numerical model.The important findings in tribological results showed that the temperature at the contact is related to the shear stress that will result from the increase of the heat flux. From these results it can be said that the measured temperature increases with the increase of the charge and converges with the contact time. The gap of temperature between experimental and numerical results is probably due to the parameter of microstructure, where in experimental porosities improve convection in the area, in contrast the numerical materials don't add this phenomena.
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Jarzyna, Jadwiga A., Stanisław Baudzis, Mirosław Janowski i Edyta Puskarczyk. "Geothermal Resources Recognition and Characterization on the Basis of Well Logging and Petrophysical Laboratory Data, Polish Case Studies". Energies 14, nr 4 (6.02.2021): 850. http://dx.doi.org/10.3390/en14040850.
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Examples from the Polish clastic and carbonate reservoirs from the Central Polish Anticlinorium, Carpathians and Carpathian Foredeep are presented to illustrate possibilities of using well logging to geothermal resources recognition and characterization. Firstly, there was presented a short description of selected well logs and methodology of determination of petrophysical parameters useful in geothermal investigations: porosity, permeability, fracturing, mineral composition, elasticity of orogeny and mineralization of formation water from well logs. Special attention was allotted to spectral gamma-ray and temperature logs to show their usefulness to radiogenic heat calculation and heat flux modelling. Electric imaging and advanced acoustic logs provided with continuous information on natural and induced fracturing of formation and improved lithology recognition. Wireline and production logging were discussed to present the wealth of methods that could be used. A separate matter was thermal conductivity provided from the laboratory experiments or calculated from the results of the comprehensive interpretation of well logs, i.e., volume or mass of minerals composing the rocks. It was proven that, in geothermal investigations and hydrocarbon prospection, the same petrophysical parameters are considered, and well-logging acquisition equipment and advanced methods of processing and interpretation, developed and improved for almost one hundred years, can be successfully used in the detection and characterization of the potential geothermal reservoirs. It was shown that the newest (current investment)—as well as the old type (archive)—logs provide useful information.
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Lertvijitpun, Pisak, i Piyorose Promdirek. "Influence of Flux-Core Arc Welding Parameters on Erosion Resistance of Stellite 12". Key Engineering Materials 658 (lipiec 2015): 91–95. http://dx.doi.org/10.4028/www.scientific.net/kem.658.91.
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Due to high wear resistance, Cobalt-based alloys, such as Stellite12 (52Co30Cr8.5W), have presently been used as materials for hardfacing in several applications. Thermowell, a protecting part for thermocouple in petrochemical production, is also coated by Stellite12. Because of high deposition rate, the flux-core arc welding (FCAW) method was selected to be hardfacing process in the research. However, their welding parameters should be exactly controlled in order to obtain desired properties, depending on the microstructure of this material. The objective of this experiment is to study the influence of the FCAW parameters on the erosion resistance of AISI 304 (Fe-18Cr-8Ni-0.06C) welded by the cobalt base alloy filler, Stellite12 (Co-30Cr-8.5W-1.5C) as the hardfacing layer. The studied parameters were welding speed in the range of 2.1-8.5 mm s-1, and wire feed speed in the range of 42.3-67.7 mm s-1, leading to different heat inputs and cooling rates. The erosion resistance was investigated by using solid particle erosion test rig at ambient temperature. Surface characterization was then carried out by SEM equipped EDX and XRD. The results showed the relationship between erosion resistance and microstructure in welding and HAZ zone. The erosion resistance was depended on the formation of interdendritic phase in the welding zone. According to the surface examination, it was found that the formation of interdendritic, including size and shape played an important role on the erosion resistance. The heat input and cooling rate concerned with welding parameters was further discussed with the erosion behavior in this research.Keywords Stellite12, Cobalt base alloys, Flux-core arc welding, FCAW, Erosion-resistance