Hot Layer Research Articles

DETECTION OF THERMAL EMISSION FROM A SUPER-EARTH

We report on the detection of infrared light from the super-Earth 55 Cnc e, based on four occultations obtained with Warm Spitzer at 4.5 microns. Our data analysis consists of a two-part process. In a first step, we perform individual analyses of each dataset and compare several baseline models to optimally account for the systematics affecting each lightcurve. We apply independent photometric correction techniques, including polynomial detrending and pixel-mapping, that yield consistent results at the 1-sigma level. In a second step, we perform a global MCMC analysis including all four datasets, that yields an occultation depth of 131+-28ppm, translating to a brightness temperature of 2360+-300 K in the IRAC-4.5 micron channel. This occultation depth suggests a low Bond albedo coupled to an inefficient heat transport from the planetary dayside to the nightside, or else possibly that the 4.5-micron observations probe atmospheric layers that are hotter than the maximum equilibrium temperature (i.e., a thermal inversion layer or a deep hot layer). The measured occultation phase and duration are consistent with a circular orbit and improves the 3-sigma upper limit on 55 Cnc e's orbital eccentricity from 0.25 to 0.06.

The rewetting of PWR fuel cladding during post-LOCA reflood: a proposed physical explanation for the micro-scale high-frequency sputtering observed

Following a loss of coolant accident in a light water reactor, reflooding of the core to quench overheating fuel is urgent. The process of quenching hot metal with liquid water has been much studied, in large part because of its great importance in this context. There is good experimental evidence such as quenching occurs via multiple micro-scale wettings of the surface, followed by vapour-driven ejection of liquid water. It is only after some tens of such wettings that permanent wetting seems to take place. In this article, we investigate this process, and put forward a physical mechanism that seems to explain this cyclical behaviour. The mechanism involves the need for some time to elapse following wetting of a hot body for heat to be conducted from within the depths of the body into the liquid water, such as to form a layer of water hot and deep enough to accommodate a critically sized bubble and thus cause ejection of the water film. Simple one-dimensional calculations using this model produce results that are in broad accord with experimental observations.

An imperialist competitive algorithm for optimal design of plate-fin heat exchangers

This paper presents the application of imperialist competitive algorithm (ICA) for optimization of a cross-flow plate fin heat exchanger. Minimization of total weight and total annual cost are considered as objectives. Seven design parameters, namely, heat exchanger length at hot and cold sides, fin height, fin frequency, fin thickness, fin-strip length and number of hot side layers are selected as optimization variables. A case study from literature is presented to show the effectiveness of the proposed algorithm. The numerical results reveal that ICA can find optimum configuration with higher accuracy in less computational time when compared to conventional genetic algorithm (GA).

Neural-Net–Based Predictive Modeling of Spout Eye Size in Steelmaking

Gas stirring is commonly used in pyrometallurgical vessels to enhance mass and heat transfer and to promote impurity removal. In the case of secondary steelmaking, the spout eye area is caused by the escape of the gas from the top of the smelt where the liquid steel is directly exposed to the air, and oxygen can be picked up through the spout eye area that can reduce the quality of steel. Thus, controlling the size of the spout eye area is very important to improving the quality of the steel and to keeping the consistency of the product. The set of prevailing models to predict spout eye size are based on specific practically difficult variables, e.g., height of slag in hot upper layer of vessels and gas flow rate at nozzle exit. Recently, the cold model results showed that the stirring process can be conveniently monitored by the signals such as (1) the image signal from the top of the vessel, (2) the sound of the stirring process, and (3) the vibration on the wall of the vessel. This article outlines the key details of a novel research investigation using neural-network–based predictive modeling such as general regression neural networks (GRNN) with genetic adaptive calibrations. Predictive capacities and generalization potentials of five model constructs (i.e., with different sets of input parameters) were explored, and the neural net modeling yielded encouraging outcomes, e.g., (1) excellent goodness-of-fit generalization measures including high values of correlation and R 2 validation parameters (e.g., r = 0.921 and R 2 = 0.845 in a model validation), and (2) low values of root mean square of errors (e.g., 3.034). Overall, the research outlined in this article demonstrates that the spout eye size can be effectively predicted by predictive neural net modeling with convenient and practically measurable variables such as sound and vibration observations on the steelmaking vessels. These results have only been demonstrated for a cold model of the process, and further work is required to show that this approach can be extended to industrial operations.

Study on flashover in a single chamber lined with combustible materials

SUMMARYWith the theories of fire dynamics and relevant parameters of combustible lining materials, a predicted model of hot gas layer temperature during pre‐flashover stage of enclosure fires was established, and the effects of lining materials on the likelihood of flashover were theoretically analyzed. By using common commercial lining materials, such as wall papers, foam plastics, wood‐based panels, and fabric‐upholstered wall panel, the phenomenon of flashover was reproduced in a small‐scale firebox of 1/4 sizes of ISO 9705 test chamber. By comparing the theoretical results with experimental data, the equation predicting the hot gas layer of quasi‐steady enclosure fires was gained; an indicator IFO to reflect overall the hazards of flashover and to classify flashover fires was proposed, and its application was initially studied. The study results can be helpful to explain further and overall the effects of lining materials on enclosure fires and can be used to guide the prevention of flashover by choosing appropriate interior decoration materials. Copyright © 2012 John Wiley & Sons, Ltd.

Characterizing Heat Release Rates Using an Inverse Fire Modeling Technique

A ubiquitous source of uncertainty in fire modeling is specifying the proper heat release rate (HRR) for the fuel packages of interest. An inverse HRR calculation method is presented to determine an inverse HRR solution that satisfies measured temperature data. The methodology uses a predictor-corrected method and the Consolidated Model of Fire and Smoke Transport (CFAST) zone model to calculate hot gas layer (HGL) temperatures in single compartment configurations. The inverse method runs at super-real-time speeds while calculating an inverse HRR solution that reasonably matches the original HRR curve. Examples of the inverse method are demonstrated by using a multiple step HRR case, complex HRR curves, experimental temperature data with a constant HRR, and a case with an experimentally measured HRR. In principle, the methodology can be applied using any reasonably accurate fire model to invert for the HRR.

An oxygen fugacity profile through the Siberian Craton — Fe K-edge XANES determinations of Fe3 +/∑Fe in garnets in peridotite xenoliths from the Udachnaya East kimberlite

The Udachnaya East kimberlite sampled garnet peridotite xenoliths from a pressure range of 1.2 to 7.1GPa in the underlying Siberian cratonic lithosphere. Samples derived from <5.2GPa lie close to a typical cratonic geotherm of 40mWm−2, whereas more deeply derived samples have temperatures ≥100°C above this geotherm. Minor and trace element compositions of garnet and clinopyroxene indicate the presence of both depleted and metasomatically enriched material in the suite. Depleted material derives from the entire sampled depth interval, but enriched material is confined to pressures of 4.5 to 6.6GPa. Thus, the Siberian cratonic lithosphere under the Undachnaya pipe consisted of a relatively cool and depleted upper layer about 150km deep, underlain by a hotter layer which extended to at least 210km depth and contained both depleted and enriched material. Fe K-edge XANES was applied to garnets from this suite to measure their Fe3+/∑Fe values, enabling determination of a redox profile through the lithospheric section represented by the xenolith suite. ΔlogƒO2[FMQ] varied from −2.5 to nearly −6.0 over the sampled pressure interval. An overall trend to lower ΔlogƒO2[FMQ] values with increasing pressure was defined mostly by the depleted samples. A superimposed oxidation trend to ΔlogƒO2[FMQ] values 1–2 units higher than the main trend mostly affected the deeper, enriched samples, indicating a clear link between metasomatism and oxidation. The amount of oxidation was insufficient to de-stabilize diamond in the deep lithosphere. A possible mechanism for metasomatic enrichment relates to localized, low degree “redox melting”, whereby upwardly percolating CH4±H2O fluids would encounter progressively more oxidizing peridotite wall-rock resulting in diamond crystallization and increased water activity in the fluid. This could lead to local partial melting and enriched melts could migrate into cooler parts of the lithosphere and crystallize, thus enriching parts of the lithosphere. Melts thus formed are expected to be relatively enriched in Fe3+ as it is moderately incompatible during partial melting. Lithospheric domains metasomatised by solidification of these melts would be relatively enriched in Fe3+ and garnets may therefore have higher Fe3+/∑Fe values, thus recording relatively higher ΔlogƒO2[FMQ] values.

Flow-field analysis of anti-kidney vortex film cooling

Film cooling is an important measure to enable an increase of the inlet temperature of a gas turbine and, thereby, to improve its overall efficiency. The coolant is ejected through spanwise rows of holes in the blades or endwalls to build up a film shielding the material. The holes often are inclined in the downstream direction and give rise to a kidney vortex. This is a counter-rotating vortex pair, with an upward flow direction between the two vortices, which tends to lift off the surface and to locally feed hot air towards the blade outside the pair. Reversing the rotational sense of the vortices reverses these two drawbacks into advantages. In the considered case, an anti-kidney vortex is generated using two subsequent rows of holes both inclined downstream and yawed spanwise with alternating angles. In a previous study, we performed large-eddy simulations (which focused on the fully turbulent boundary layer) of this anti-kidney vortex film-cooling and compared them to a corresponding physical experiment. The present work analyzes the simulated flow field in detail, beginning in the plenum (inside the blade or endwall) through the holes up to the mixture with the hot boundary layer. To identify the vortical structures found in the mean flow and in the instantaneous flow, we mostly use the λ 2 criterion and the line integral convolution (LIC) technique indicating sectional streamlines. The flow regions (coolant plenum, holes, and boundary layer) are studied subsequently and linked to each other. To track the anti-kidney vortex throughout the boundary layer, we propose two criteria which are based on vorticity and on LIC results. This enables us to associate the jet vortices with the cooling effectiveness at the wall, which is the key feature of film cooling.

The&lt;i&gt; In Situ&lt;/i&gt; Shear Strength of Roller Compacted Concrete in the Dam of Jinghong Hydropower Station

For roller compacted concrete with the admixtures of grinding limestone powder and water quenched iron slag powder (shortly called double admixture RCC) in dam of Jinghong Hydropower station, the raw materials and the mix proportion of the RCC were studied. Then one experiment on in situ shear strength are carried out between hot rise layer and cold rise layer at the altitude of 573.3 meters of RCC in dam block 23 based on the flat push-situ shear test program. The shear strength indexes of hot rise layer and cold rise layer in RCC for Jinghong Hydropower Station are tested by the experiment subsequently. The study results show that the index for interlayer shear strength of the cold rise layer of RCC with 90 days ages in dam are the friction coefficient of 1.12, and the cohesion of 1.22 MPa. The index for interlayer shear strength of the hot rise layer of RCC with 90 days ages in dam are the friction coefficient of 1.32, and the cohesion of 1.24 MPa. The study results also show that the construction processes meet the requirements of the RCC construction and the integrity of hot rise layer of RCC in the dam is better.

2005年8月15日関東に発生した短時間強雨をもたらした大気安定度に対する境界層パラメタリゼーションの感度分析

Sensitivity of boundary layer parameterizations to atmospheric stability preceding heavy rainfall is investigated using the 5th-generation NCAR Mesoscale Model (MM5). Four turbulence parameterizations [MRF, Blackadar, Gayno-Seaman and Eta] and four surface flux schemes [Carlson-Boland, Garratt, Zilitinkevich and Janjic] are selected for evaluation. The Carlson-Boland surface flux scheme produces deep convection and causes hot and dry boundary layer regardless of the turbulence parameterizations. The combination of the MRF turbulence parameterizations and the Garratt surface flux scheme well reproduce local heavy rainfall which observed at Tokyo on 15 August 2005.

Research of Microstructure and Properties of Ni-based Alloy Hot Sprayed-welding Layers by Laser Remelted and Aging Treatment

Microstructure changes of laser remelted Ni-based alloy hot sprayed-welding layers after different aging treatment are studied by means of optical microscope(OM),scanning electron microscopy(SEM) and X-ray diffraction(XRD),and microhardness is also compared.The results show that,after laser remelting,microstructure of hot sprayed-welding layers has been significantly refined and improved,the remelted layers mainly consist of fine dendrites with small lamellar eutectic structure in their branches.When aging temperature is kept constant(600 ℃),with the extention of aging time,the morphology of dendrites remain original,but the eutectic structures nodulize and lose their lamellar structure.And at the same time,a lot of hard phase precipitate in the matrix,which enable matrix a high hardness;When aging time is kept constant(6 h),with the increasing of aging temperature,the morphology of dendrites become equiaxial apparently,meanwhile,precipitated carbide grow up together and its type has also changed,which led to a decline of layer hardness;When aging temperature exceed 800 ℃,the hardness of remelted layer fall sharply.

Development of The new measuring system for the Sinter Process

We have developed and implemented the new four measuring system for Sinter plant. They are the Moisture measuring system, the temperature measuring system in the sinter zone, the air leakage monitoring system for the pallets and the red hot layer monitoring system. And we are utilizing their information to operate the sinter process efficiently.

A Comparison of Cover Coat Methods for Electronic Flexible Printed Circuit (E-FPC) Based on Peeling Strength

In electronic flexible printed circuit (E-FPC) manufacturing procedure, the cover laminating process in which the line circuit (copper wire) is covered with hot cover layer on the printed circuits is importance process. This process will help to increase elasticity, strength and corrosion protection to the product therefore this process can affect directly to quality of the printed circuit. The process for laminating printed circuits can be classified into two methods by coating with industry iron and hot bar machine. This article compares the quality of the electrical circuit between industry iron and hot bar machine methods in the cover coating process by using Peeling Strength to indicate the quality in the same temperature and time condition. The experimental result illustrates the electrical circuits using the hot bar machine method give Peeling Strength value in the acceptable range and the laminating surface of circuits is smooth and uniform. On the other hand, Peel Strength value of electrical circuits using the industry iron method is unsteady and lower than the acceptable range. Moreover the result circuit product has wrinkled coating surface and become the waste product.

Full-scale experimental and numerical studies on compartment fire under low ambient temperature

Abstract A fire experiment with wood crib was conducted in a concrete building under low ambient temperature of −10 °C to explore fire development and temperature distribution. The concrete building consists of a two-storey compartment with the size of 9.0 m by 5.0 m by 4.8 m high and a four-storey stairwell with the size of 5.0 m by 2.4 m by 10.0 m high. The fuel mass loss rate and temperatures at different positions were measured. Two fire cases, with different assumed ambient temperatures of −10 °C and 20 °C respectively, were then simulated by using FDS software to investigate the effect of ambient temperature and compare with the experimental results. The numerical results show that the calculated heat release rate is in reasonably good agreement with the measured full-scale result before water suppression. The calculated temperatures in the hot combustion gas layer at different positions agree also very well with the measured values. However, the measured fresh air temperature at the floor level near the fire source is higher than the calculated value. This discrepancy may partly depend on measuring errors as analyzed in the paper.

Heat can cool near-critical fluids

We report experiments with very compressible fluids near the liquid-gas critical point. These experiments are performed (i) under microgravity in low Earth orbit by using SF(6) at liquidlike density and (ii) under Earth's gravity with CO(2) at gaslike density. The sample fluid is filled in an interferometer cell with its walls maintained at constant temperature. In situ thermistors measure the local fluid temperature. One of the thermistors is also used as a heat source to generate heat pulses. With no gravity-induced fluid convection, the evolution of fluid temperature is governed by the balance of heat flux between the thermal boundary layer of the heat source, which compresses the bulk fluid, and the thermal boundary layer at the wall, which expands it. When heat pulses are applied to the fluid under weak or Earth's gravity, a long thermal transient is observed at the end of the heat pulse where the bulk fluid temperature reaches significantly below the initial temperature. This unconventional cooling originates from the fast decompression of the fluid, which is induced by the rapid convectively disappearing hot boundary layer at the heat source, and the persistence of an anomalously thin cold boundary layer convectively induced at the cell wall. This striking phenomenon is observed in a large range of temperature, density, and various thermodynamic conditions. This anomalous cooling effect persists for an appreciable period of time corresponding to the diffusive destruction of the cold boundary layer. We found that the effect is also more pronounced when the free fall acceleration is large. We have analyzed the result by using a simple one-dimensional model with ad hoc convective heat losses.

Heat Conduction in a Rectangular Tube With Eccentric Hot Spots

The current paper presents the results of an analytical study of steady state heat conduction in a rectangular tube with eccentric hot spots on both the top and the bottom surfaces. The rectangular domain is assumed to be adiabatic on the lateral surfaces and a single or multiple eccentric hot spots can be applied on the top and bottom surfaces. Isothermal, heat flux, or convection boundary conditions can be applied on the hot spots. Because the hot spots are eccentric, the spreading resistance becomes a dominant factor in heat conduction in the tube. The multiple hot spots, multiple layers and combination problems are also studied in the current paper. The solutions can be applied to the thermal management of three-dimensional stacks of electronic devices, the interconnect layers and the thermoelectric devices.

Constraints on mantle plumes on Venus: Implications for volatile history

The analysis of Venus’ gravity field and topography suggests the presence of a small number of deep mantle plumes (∼9). This study predicts the number of plumes formed at the core–mantle boundary, their characteristics, and the production of partial melt from adiabatic decompression. Numerical simulations are performed using a 3D spherical code that includes large viscosity variations and internal heating. This study investigates the effect of several parameters including the core–mantle boundary temperature, the amount of internal heating, and the mantle viscosity. The smallest number of plumes is achieved when no internal heating is present. However, scaling Earth’s radiogenic heating to Venus suggests a value of ∼16 TW. Cases with internal heating produce more realistic lid thickness and partial melting, but produce either too many plumes or no plumes if a high mantle temperature precludes the formation of a hot thermal boundary layer. Mantle viscosity must be reduced to at least 10 20 Pa s in order to include significant internal heating and still produce hot plumes. In all cases that predict melting, melting occurs throughout the upper mantle. Only cases with high core temperature (>1700 K) produce dry melting. Over time the upper mantle may have lost significant volatiles. Depending on the water content of the lower mantle, deep plumes may contribute to present-day atmospheric water via volcanic outgassing. Assuming 50 ppm water in mantle, 10 plumes with a buoyancy flux of 500 kg/s continuously erupting for 4 myr will outgas an amount of water on the order of that in the lower atmosphere. A higher level of internal heating than achieved to date, as well as relatively low mantle viscosity, may be required to achieve simulations with ∼10 plumes and a thinner lid. Alternatively, if the mantle is heating up due to the stagnant lid, the effect is equivalent to having lower rates of internal heating. A temperature increase of 110 K/byr is equivalent to −13 TW. This value along with the internal heating of 3 TW used in this study may represent the approximate heat budget of Venus’ mantle.

X-RAY IONIZATION OF HEAVY ELEMENTS APPLIED TO PROTOPLANETARY DISKS

The consequences of the Auger effect on the population of heavy-element ions are analyzed for the case of relatively cool gas irradiated by keV X-rays with intended applications to the accretion disks of young stellar objects. Highly charged ions are rapidly reduced to the doubly charged state in neutral gas, so the aim here is to derive the production rates for these singly and doubly charged ions and to specify their transformation by recombination, charge transfer, and molecular reactions. The theory is illustrated by calculations of the abundances of 11 of the most cosmically abundant heavy elements in a model of a typical T Tauri star disk. The physical properties of the gas are determined with an X-ray irradiated thermal–chemical model, which shows that the disk atmosphere consists of a hot atmosphere overlaying the mainly cool body of the disk. There is a warm transition layer where hydrogen, carbon, and oxygen are transformed from atomic to molecular species and the ionization drops by several orders of magnitude. The doubly charged ions are then largely confined to the hot outer layers of the disk. The nature of the dominant ions below the transition depends sensitively on the poorly constrained abundances of the heavy elements. Observational consequences and connections with the active layers of the magnetorotational instability are briefly discussed.

Smoke oxidation kinetics for application to prediction of clean burn patterns

SUMMARYSmoke deposition patterns are a potentially rich source of information concerning the behavior of a fire. Clean burn patterns are smoke‐free areas where smoke deposits have been oxidized away. In order to predict the formation of clean burn patterns, smoke oxidation kinetics are required. Smoke oxidation kinetics were studied for smokes from acrylonitrile butadiene styrene, polymethylmethacrylate, polypropylene, and gasoline. The fuels were burned below a hood, and smoke samples were collected from the hot gas layer and from the wall surfaces. The smokes from various polymers and gasoline were found to contain no measurable volatile organic chemicals. The kinetics of the smokes from the polymers and gasoline were found to be satisfactorily modeled as first order in both smoke and oxygen with the same kinetic constants for all fuels tested. The activation energy was calculated to be 211 kJ/mol, and the pre‐exponential factor was found to be 4.7 × 1010/s. These kinetic parameters provide a basis for modeling clean burn pattern generation. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Thin oceanic crust and flood basalts: India‐Seychelles breakup

Recent seismic experiments showed that separation of India from the Seychelles occurred in two phases of rifting. The first brief phase of rifting between India and the Laxmi Ridge formed the Gop Rift, which is characterized by thick oceanic crust and underplating of the adjacent continental margins. The age of the Gop Rift is uncertain, initiation of seafloor spreading being some time between 71 and 66 Ma. This was then followed by rifting and seafloor spreading between the Laxmi Ridge and the Seychelles, the onset of which is well dated by magnetic anomalies at 63.4 Ma and characterized by thin oceanic crust. Both of these rift events occurred within 1000 km of the center of the Deccan flood basalts, which formed at 65 ± 1 Ma. To constrain the age of the Gop Rift and to explore the reasons for the change in crustal structure between the Gop Rift and Seychelles‐Laxmi Ridge margins, we employ a geodynamic model of rift evolution in which melt volumes, seismic velocity, and rare earth element (REE) chemistry of the melt are estimated. We explore the consequences of different thermal structures, hydration, and depletion on the melt production during the India‐Seychelles breakup to understand the reasons behind the thin oceanic crust observed. Magmatism at the Gop Rift is consistent with a model in which the seafloor spreading began at 71 Ma, ca. 6 Myr prior to the Deccan. The opening occurred above a hot mantle layer (temperature of 200°C, thickness of 50 km) that we interpret as incubated Deccan material, which had spread laterally beneath the lithosphere. This scenario is consistent with observed lower crustal seismic velocities of 7.4 km s−1 and 12 km igneous crustal thickness. The model indicates that when the seafloor spreading migrated to the Seychelles‐Laxmi Ridge at 63 Ma, the thermal anomaly was reduced significantly but not sufficient to explain the observed reduction in breakup magmatism. From observations here of 5.2 km oceanic crust, lower crustal seismic velocities of 6.9 km s−1 and a flat REE profile, we infer that breakup occurred in a region of mantle that became depleted by prior extension related to the Gop Rift.