Hot Layer Research Articles

Research on Water Temperature Change of Hot Dry Rock Fracture Storage Layer in Shenyang

Hot dry rock(HDR) provides heat through fracture storage layer. The purpose of research on water temperature change of hot dry rock fracture is to study that whether heat energy can satisfy five months winter heating or not. Research method is establishing model of hot dry rock fractured storage layer by means of numerical simulation software FLUENT according to the rock physical properties in Shenyang region. The depth of drilling is 4000m and the water flow rate is 1cm/s. Research principle is high temperature underground rock transfer heat to medium water in the fracture by coupling. Conclude water temperature change equation every two weeks. The results of the study is that fracture water temperature distribution can be approximated taken as linear distribution. According to the slope K, we can conclude water temperature change formula(3.10), and we can use it to infer fracture water temperature.

Experimental Friction and Temperature Investigation on Aircraft Tires

ABSTRACT For modeling an aircraft tire using the brush model method, the friction coefficient μ between rubber and asphalt should not only be described in terms of the applied pressure and sliding velocity/slip ratio, but also by local temperature inside the contact area. Its influence cannot be neglected, since it leads to significant material property changes. Therefore, investigations on different test rigs are analyzed using thermal recordings of an infrared camera. First measurements are done on a high speed linear tester (HiLiTe), a test rig at the Institute of Dynamics and Vibration Research (IDS) at Leibniz University Hanover, Germany. It allows testing single tread block samples with a constant slip ratio of 100%, that is, pure sliding, on a variety of surfaces such as dry and wet asphalt or concrete, as well as on snow and ice. Results in this paper show that the convection has a smaller impact on tread block cooling than the actual contact between runway surface and sample. Since colder surface temperatures lead to higher friction, this effect antagonizes the excitation frequency, which heats up the rubber sample at high velocities. On long-lasting test sequences a quasi–steady-state friction coefficient might be achieved once these effects start to converge. Still, owing to permanent slip, the abrasion leads to cooling as the hot top layer of the rubber is removed occasionally. In addition to these quasi–steady-state measurements on HiLiTe, the thermal behavior of an aircraft tire is investigated with an autonomously running test rig. It allows realistic testing on an airfield runway by altering load, speed, and slip angle of the tire within and beyond the regions of a passenger aircraft. During the measurements, new and partially unknown effects could be observed. The temperature is mostly influenced by the slip angle followed by speed and load. Furthermore, the contact between tire and runway leads to cooling of the tread but does not affect the temperature inside the grooves. They heat up separately and tend to transfer heat to the tread if the cooling by the runway becomes too low.

Effects of fire-fighting on a fully developed compartment fire: Temperatures and emissions

This study evaluates the effects and consequences of fire-fighting operations on the main characteristics of a fully-developed compartment fire. It also presents data and evaluation of the conditions to which fire-fighters are exposed. A typical room enclosure was used with ventilation through a corridor to the front access door. The fire load was wooden pallets. Flashover was reached and the fire became fully developed before the involvement of the fire-fighting team. The progression of the fire-fighters through the corridor and the main-room suppression attack – in particular the effect of short, medium and long water pulses on either the hot gas layer or the fire seat – was charted against the compartment temperatures, heat release rates, oxygen levels and toxic species concentrations. The fire fighting team was exposed to extreme conditions, heat fluxes in excess of 35kW/m2 and temperatures of the order of 250°C even at crouching level. The fire equivalence ratio showed rich burning with high toxic emissions in particular of CO and unburnt hydrocarbons very early in the fire history and a stabilisation of the equivalence ratio at about 1.8. The fire fighting operations made the combustion temporarily richer and the emissions even higher.

Distribution and diversity of Verrucomicrobia methanotrophs in geothermal and acidic environments

Recently, methanotrophic members of the phylum Verrucomicrobia have been described, but little is known about their distribution in nature. We surveyed methanotrophic bacteria in geothermal springs and acidic wetlands via pyrosequencing of 16S rRNA gene amplicons. Putative methanotrophic Verrucomicrobia were found in samples covering a broad temperature range (22.5-81.6°C), but only in acidic conditions (pH 1.8-5.0) and only in geothermal environments, not in acidic bogs or fens. Phylogenetically, three 16S rRNA gene sequence clusters of putative methanotrophic Verrucomicrobia were observed. Those detected in high-temperature geothermal samples (44.1-81.6°C) grouped with known thermoacidiphilic 'Methylacidiphilum' isolates. A second group dominated in moderate-temperature geothermal samples (22.5-40.1°C) and a representative mesophilic methanotroph from this group was isolated (strain LP2A). Genome sequencing verified that strain LP2A possessed particulate methane monooxygenase, but its 16S rRNA gene sequence identity to 'Methylacidiphilum infernorum' strain V4 was only 90.6%. A third group clustered distantly with known methanotrophic Verrucomicrobia. Using pmoA-gene targeted quantitative polymerase chain reaction, two geothermal soil profiles showed a dominance of LP2A-like pmoA sequences in the cooler surface layers and 'Methylacidiphilum'-like pmoA sequences in deeper, hotter layers. Based on these results, there appears to be a thermophilic group and a mesophilic group of methanotrophic Verrucomicrobia. However, both were detected only in acidic geothermal environments.

Control of convective heat transfer by changing the right-angle position and the base angle of triangular storages: lattice Boltzmann simulation

The study of natural convection in triangular enclosures has many practical applications. In this paper, natural convection heat transfer inside triangular cavities with two different right-angle positions is studied numerically by the second-order lattice Boltzmann method. The effects of Rayleigh number and geometrical parameters of the cavity on the flow field and heat transfer for various base angles are completely analyzed. The combination of the two topics (different base angles in triangular cavities and different right-angle positions in the cavity) is the main novelty of the present study. When the right angle of the cavity is located at the bottom left corner, the local Nusselt number is continuously increased from the horizontal wall to the singular point. In contrast, when the right angle is at the top left corner, the obtained results show a minimum value in the local Nusselt number as a function of triangle angle. Strictly speaking, this is physically due to the effects of interaction of the cold fluid layer (near the vertical wall) with the hot fluid layer moving upward. By analysis of different base angles, as the base angle of the cavity increases, the location of the observed minimum Nusselt number moves away from the intersection point between the hot and cold walls. Our work extends the previous paper of Kent et al. (Int J Heat Mass Transf 44:187–200, 2007) by the analysis of different triangular cavities.

Bremsstrahlung of Waves Polarized Linearly Across a Strong Magnetic Field in Low-Energy Electron–Nucleus Collisions

We analyze bremsstrahlung which accompanies the low-energy electron–nucleus collisions in a strong magnetic field under the condition that the electron Larmor radius is less than the characteristic impact parameter of close Coulomb collisions in the absence of the magnetic field. We calculate the spectral emissive power at frequencies below the electron cyclotron frequency, which is stipulated by the electric drift of the electron gyration axis in the Coulomb field of a nucleus and the external magnetic field. The electric drift produces the nonzero bremsstrahlung and collisional absorption of linearly polarized waves transverse to an external magnetic field. We show that in thermal equilibrium the absorption coefficient of the extraordinary waves in a rarefied plasma reaches a minimum at the corresponding frequency. The minimum can ensure that these waves exit from the deeper and hotter layers in the photosphere of an isolated magnetic white dwarf compared with the ordinary waves. This effect can stipulate the observed linear polarization of the star emission in the band below the electron cyclotron frequency.

The Catastrophe Mechanism of Flashover in Biomass Boiler

The flashover phenomenon in biomass boiler causes serious damages to the equipments performance as well as security of people due to people are not clear about biomass boiler running, and thus preventing flashover from happening has a positive significance on boiler running. The characteristics of biomass fuel particles have been analyzed at first, and then simplifying the structure of boiler in order to model conveniently. This essay focus on justifying the stability of combustion system of biomass boiler with catastrophe theory in combination with the measured and calculated data, it demonstrates that swallowtail catastrophe conforms to the flashover mechanism. By building energy equation, conducting dimensionless treatment and carrying out the swallowtail catastrophe research method, the instability point is obtained. The gained critical flashover temperature of hot smoke layer is 686.71°C which is similar to predecessors studies, Then changing the parameters values for the sake of calculating different hot gas layer temperatures. The higher the hot gas layer temperature is, more hazardous the flashover tends to be. The research reveals that increasing the initial temperature of air or aggrandizing area of fire grate (larger than 3.36m2) contribute to increase flashover temperatures. However, augment of vapor heat and heat transfer area have the opposite effects.

Evaluation of Thermal Stratification Induced Stress in Pipe and its Impact on Fatigue Design

Thermal stratification is a phenomenon where a hot layer of fluid flows over a cold layer of fluid due to density difference. Thermal stratification is dominant in NPP piping where hot and cold fluids coexist or separated by a leaking valve. This phenomenon produces stresses in axial and tangential direction which causes damage during thermal cycling induced due to thermal stratification. These stresses produce additional damage during fatigue which is not incorporated in earlier plant piping design. This paper comprises a detail study of thermal stresses induced due to thermal stratification and its impact on fatigue life of piping. In this study the variation in support conditions are also analyzed along with their effect on the stress distribution of the pipe. The categorization of axial stress distribution is carried out with finite element model for a thermally stratified pipe. An analytical model for calculation of different thermal stress considering intermixing layer between hot and cold layer is formulated during a thermal stratification condition. The formulation is also validated with the results available in literature on thermal stratification. A case study for damage evaluation due to thermal stratification was carried out for a thermally stratified typical NPP surge line.

A Simplified Relation Between Hot Layer Height and Opening Mass Flow

The mass flow of air through an opening in a well-mixed compartment fire can be calculated with a simple expression. Similar simple models are lacking for the stratified pre-flashover case. Usually an advanced computer model is required to calculate the mass flow through an opening in a pre-flashover compartment fire. However, two equations for the opening mass flow through an opening are presented and validated in this paper. The presented equations are predominantly valid for temperatures above 200°C and predictions with the equations are shown to be within 10% of results from computer simulations and experimental measurements. The equations can also be combined with existing plume models in order to give an estimate of the hot layer height in a compartment fire with a predefined heat release rate.

Development of an analytical model to quantify downward smoke displacement caused by a water spray for zone model simulations

A stand-alone analytical model for downward smoke layer displacement caused by a water spray is developed. The model can be implemented into two-zone model calculations. Smoke flow into and out of the water spray envelope is incorporated, as well as a model for the heat exchange between the smoke and the water droplets. The model input quantities are water flow rate, orifice diameter, droplet diameter, spray angle, initial smoke layer thickness and temperature, and ambient air temperature. The quality of the model predictions is illustrated for a range of experimental conditions. Results are shown to be sensitive to the mean droplet diameter and the spray angle. Then, the combinations of values of these parameters are suggested for the sprinkler considered. A practically important phenomenon of abrupt strong downward smoke layer displacement is explained in that the upward buoyancy flow diminishes due to the entrainment of cool air into the water spray envelope. This only occurs for high enough water flow rates and as long as the smoke layer thickness is below a critical value. Therefore, this is particularly dangerous during the smoke layer build-up phase. Finally, the accuracy of the model for the heat transfer rate from the hot smoke layer to the droplets and the smoke temperature inside the spray region are evaluated by comparison to experimental data.

Growth behavior and properties of atomic layer deposited tin oxide on silicon from novel tin(II)acetylacetonate precursor and ozone

In this work, a novel liquid tin(II) precursor, tin(II)acetylacetonate [Sn(acac)2], was used to deposit tin oxide films on Si(100) substrate, using a custom-built hot wall atomic layer deposition (ALD) reactor. Three different oxidizers, water, oxygen, and ozone, were tried. Resulting growth rates were studied as a function of precursor dosage, oxidizer dosage, reactor temperature, and number of ALD cycles. The film growth rate was found to be 0.1 ± 0.01 nm/cycle within the wide ALD temperature window of 175–300 °C using ozone; no film growth was observed with water or oxygen. Characterization methods were used to study the composition, interface quality, crystallinity, microstructure, refractive index, surface morphology, and resistivity of the resulting films. X-ray photoelectron spectra showed the formation of a clean SnOx–Si interface. The resistivity of the SnOx films was calculated to be 0.3 Ω cm. Results of this work demonstrate the possibility of introducing Sn(acac)2 as tin precursor to deposit conducting ALD SnOx thin films on a silicon surface, with clean interface and no formation of undesired SiO2 or other interfacial reaction products, for transparent conducting oxide applications.

Study on Influencing Factors for Service Performance of Anti-sliding Layer with Hot Melting Macadam

This paper presents a new treatment to icy road, anti-sliding layer with hot melting macadam. Experiments were done to investigate the different factors influencing the effect of hot melting macadam anti-sliding layer. The friction coefficient and texture depth of anti-sliding layer were taken as the quantitative index. The icy layer thickness, macadam particle size and macadam temperature were taken as influencing factors, and the full-scale test including three factors was carried out. The BPN (British pendulum number) was measured using British pendulum test, and the status of macadam spalling was observed at the same time. The TD (texture depth) was measured by handle sand patch, the significant analysis, multiple comparison and regression analysis were used to analyze the experimental data. Experimental phenomenon and data analysis show that the three experiment factors have remarkable effect on the design indexes, and there are also prominent interactions among them; the application result of hot melt macadam anti-sliding layer is optimum when icy layer is 2cm. At last 9.5mm particle size of macadam and 90°C temperature of macadam were recommend to use when the thickness of icy layer is 1cm∼3cm.

HYDROGEN BURNING ON ACCRETING WHITE DWARFS: STABILITY, RECURRENT NOVAE, AND THE POST-NOVA SUPERSOFT PHASE

We examine the properties of white dwarfs (WDs) accreting hydrogen-rich matter in and near the stable burning regime of accretion rates as modeled by time-dependent calculations done with Modules for Experiments in Stellar Astrophysics (MESA). We report the stability boundary for WDs of masses between 0.51 solar masses and 1.34 solar masses as found via time-dependent calculations. We also examine recurrent novae that are accreting at rates close to, but below, the stable burning limit and report their recurrence times and ignition masses. Our dense grid in accretion rates finds the expected minimum possible recurrence times as a function of the WD mass. This enables inferences to be made about the minimum WD mass possible to reach a specific recurrence time. We compare our computational models of post-outburst novae to the stably burning WDs and explicitly calculate the duration and effective temperature (Teff) of the post-novae WD in the supersoft phase. We agree with the measured turnoff time - Teff relation in M31 by Henze and collaborators, infer WD masses in the 1.0-1.3 solar masses range, and predict ejection masses consistent with those observed. We close by commenting on the importance of the hot helium layer generated by stable or unstable hydrogen burning for the short- and long-term evolution of accreting white dwarfs.

Thermodynamic and Economic Optimization of Plate Fin Heat Exchangers Using the Bees Algorithm

This study presents the successful application of the bees algorithm (BA) for optimal design of a cross‐flow plate fin heat exchanger by offset strip fins. The ε – NTU method is used to approximate the heat exchanger effectiveness and pressure drop. Two different objective functions including the minimization of total annual cost (sum of investment and operational costs) and total number of entropy generation units for certain heat duty required under given space constraints are considered as targets of optimization separately. Based on the applications, seven design parameters (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. Two examples from the literature are presented to illustrate the efficiency and accuracy of the proposed algorithm. Results showed that the BA can detect an optimum configuration with higher speed (short computational time) and accuracy compared to the imperialist competitive algorithm (ICA) and the genetic algorithm (GA). © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(5): 427–446, 2014; Published online 3 October 2013 in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21087

The Study on Heat Transfer Model and Algorithm of Multi-Sectional Regenerative Air Heater in Power Plant Boiler Based on Analytical Method

Tri-sectional regenerative air heater is used widely because of its compactness and better performance. Study on the matching analytical calculation method of heat transfer is rarely carried out because of the complicated heat transfer process. This paper developed a model to solve the heat transfer calculation of multi-sectional regenerative air heaters, which usually have several layers. Then we designed the computational procedure to carry out the model. One example of a tri-sectional regenerative air heater with hot layer and cold layer shows the effectiveness of the algorithm, and the results suggest that this approach is valid. The impact of leakage on performance of the regenerative air heater was discussed. There is a negative linear correlation between exhaust gas temperature and air leakage, and boiler efficiency has a nearly linear negative correlation with air leakage.

Film Cooling Using Antikidney Vortex Pairs: Effect of Blowing Conditions and Yaw Angle on Cooling and Losses

A film-cooling configuration generating an antikidney vortex pair is studied. The configuration features cylindrical cooling holes inclined at an angle of α=35 deg and arranged in two spanwise rows with row-wise alternating yaw angles ±β. Results of several large-eddy simulations are presented with varying blowing conditions and yaw angles. The effects on the achieved cooling and the generated losses are studied. The film-cooling Reynolds number (based on the fully turbulent hot boundary layer along a flat plate and the cooling hole diameter) is 6570 and the Mach number is 0.2. The density as well as mass-flux ratios (DR and M) range from 1 to 2 and the yaw angles from β=±30 deg to ±60 deg. We identify scaling parameters and explain relevant mechanisms. Moreover, the flow field is subdivided into three regions featuring different physical mechanisms: the single-jet, the jet-interaction, and the diffusion region. A strong antikidney vortex pair occurs for high momentum ratios I. For the highest ratio, I = 2.3, our configuration may provide even better effectiveness than cooling with particular fan-shaped holes.

Contribution of Galvanizing Layer to Hydrogen Induced Cracking Failure of AISI 4140 Bolt for Padeye Fixing in Marine Environment

A high strength bolt with hot dip galvanizing treatment failed shortly after being installed for two days on a padeye of mooring dolphin. The bolt was installed with increasing stress on the second day in which the value was nearly twice. Investigation results showed the bolt fractured with the nut head separated from the pin. Corroded fracture surface with brittle characteristic and no plastic deformation observed dominating the failed area. Characterization of hardness and chemical composition followed with microstructure and fractography observation on the fracture surface then conducted in order to analyze the reason for this brittle fracture occurrence. Results indicate that, while the bolt conforms to the material specification in term of chemical composition, the hardness value was high. The microstructure observation reveals a transgranular crack propagation and cleavage failure occurred. The cleavage failure was clearly observed under fractography observation using scanning electron microscope. Failed galvanize layer due to mechanical failure becomes preferential site for hydrogen evolution in marine environment, which leads to hydrogen diffusion into the matrix, thus results in hardness increase. The increasing stress during installation become detrimental to the bolt and facilitate the hydrogen induce cracking. Detrimental effect of hot dip galvanize layer is pointed out in the application of high strength material in marine environment.

On the energy of ions at the expansion of a hot plasma layer into vacuum

A theoretical model has been developed to describe the expansion of a plasma layer into vacuum for an arbitrary electron temperature. The limit transitions to the previous results for quasineutral scattering and Coulomb explosion have been demonstrated. Comparison with the numerical simulation shows a high accuracy of the theory.

Draft Genome Sequence of the Lignocellulose Decomposer Thermobifida fusca Strain TM51

Here, we present the complete genome sequence of Thermobifida fusca strain TM51, which was isolated from the hot upper layer of a compost pile in Hungary. T. fusca TM51 is a thermotolerant, aerobic actinomycete with outstanding lignocellulose-decomposing activity.

Analysis of observations of the dwarf nova pegasi 2010

Analysis of photometric and spectroscopic observations of GSC 02197-00886 at the outburst maximum (on May 8, 2010) and at the stage of relaxation towards the quiescent (on August 4, 2010) was performed. Radiation of an optically thick accretion disc with a hot boundary layer dominates the spectra, which are consistent with the spectra of a WZ Sge-type dwarf novae. In the relaxation phase, an optically thin accretion disc with radiation in the HI and HeI emission lines is observed against the background of the absorption spectrum of a white dwarf. The parameters of GSC 02197-00886, which were determined by combining the radial velocities of the components with the assumption that the secondary component is close to mainsequence stars, differ significantly from the parameters that characterize other WZ Sge-type systems. We hypothesize that the secondary component was excited in the course of the outburst and experienced long-lasting relaxation towards the main-sequence state.