Changes In Temperature Field Research Articles

Effects of the Preheated Temperature and the Change in Gas Composition on Soot Formation in the Gas Reforming Process by Partial Combustion Method

Partial combustion can be an effective way to reform fuel gases. The possible application we assume is reforming of tar in a producer gas from woody biomass gasification. The reforming process of tar by partial combustion of the producer gas is conducted in a gas reformer by the combination of oxidative cracking and thermal cracking of tar. The partial combustion type gas reformer is an apparatus stage subsequent to the biomass gasifier. The inverse diffusion flame is formed when the oxidizer for partial combustion is supplied to the producer gas. Cracking and polymerization of the tar occur simultaneously at proximity of the inverse diffusion flame. This polymerization of tar into soot is, however, a significant problem in the gas reformer, e.g. the reduction of the carbon conversion ratio and the change in temperature field by radiation from soot. The experimental and numerical study have been performed to clarify effects of hydrogen addition to the oxidizer on soot formation and growth of the polycyclic aromatic hydrocarbons (PAHs) that is precursor of soot. The main results from experiments are as follows. The increase in the preheated temperature of model producer gas suppresses soot formation. This is because the increase in preheated temperature leads the fraction of toluene to be low. TSI (Threshold Sooting Index) of toluene (model tar) is relatively high within components in the model producer gas.

Nanoscale oxides shape up

Reversible strains up to 14% driven by changes in temperature or electric field have been realized in a thin film of bismuth ferrite oxide.

Forcing of stratospheric chemistry and dynamics during the Dalton Minimum

Abstract. The response of atmospheric chemistry and dynamics to volcanic eruptions and to a decrease in solar activity during the Dalton Minimum is investigated with the fully coupled atmosphere–ocean chemistry general circulation model SOCOL-MPIOM (modeling tools for studies of SOlar Climate Ozone Links-Max Planck Institute Ocean Model) covering the time period 1780 to 1840 AD. We carried out several sensitivity ensemble experiments to separate the effects of (i) reduced solar ultra-violet (UV) irradiance, (ii) reduced solar visible and near infrared irradiance, (iii) enhanced galactic cosmic ray intensity as well as less intensive solar energetic proton events and auroral electron precipitation, and (iv) volcanic aerosols. The introduced changes of UV irradiance and volcanic aerosols significantly influence stratospheric dynamics in the early 19th century, whereas changes in the visible part of the spectrum and energetic particles have smaller effects. A reduction of UV irradiance by 15%, which represents the presently discussed highest estimate of UV irradiance change caused by solar activity changes, causes global ozone decrease below the stratopause reaching as much as 8% in the midlatitudes at 5 hPa and a significant stratospheric cooling of up to 2 °C in the mid-stratosphere and to 6 °C in the lower mesosphere. Changes in energetic particle precipitation lead only to minor changes in the yearly averaged temperature fields in the stratosphere. Volcanic aerosols heat the tropical lower stratosphere, allowing more water vapour to enter the tropical stratosphere, which, via HOx reactions, decreases upper stratospheric and mesospheric ozone by roughly 4%. Conversely, heterogeneous chemistry on aerosols reduces stratospheric NOx, leading to a 12% ozone increase in the tropics, whereas a decrease in ozone of up to 5% is found over Antarctica in boreal winter. The linear superposition of the different contributions is not equivalent to the response obtained in a simulation when all forcing factors are applied during the Dalton Minimum (DM) – this effect is especially well visible for NOx/NOy. Thus, this study also shows the non-linear behaviour of the coupled chemistry-climate system. Finally, we conclude that especially UV and volcanic eruptions dominate the changes in the ozone, temperature and dynamics while the NOx field is dominated by the energetic particle precipitation. Visible radiation changes have only very minor effects on both stratospheric dynamics and chemistry.

2-D Simulation of Heat and Mass Transfer Effects on Charge/Discharge Characteristics of a Solid Oxide Redox Flow Battery

A time-dependent 2-D numerical simulation was performed on a solid oxide redox flow battery (SORFB) in order to reveal the fundamental characteristics of this new system. SORFB is a rechargeable battery consisting of solid oxide electrochemical cell (SOEC) and redox metal. The simulation considers heat and mass transfer in the system taking both electrochemical and redox reactions into account. The numerical results clearly showed the time-dependency of the thermal field, particularly in discharge operation. The spatial and temporal changes of temperature field associated with the change of the current density distribution were results of combined effects of heat generation/absorption by the electrochemical and redox reactions and heat release by air convection. It was also found that the active reaction region in redox metal evolutes with time. Since these physical quantities affect the battery performance, the heat transfer and gas diffusion should be carefully designed.

Numerical Simulation and Parameter Analysis on Low-Temperature Geothermal System in Homogeneous Porous Medium

According to the mass and energy conservation principle of simulation program TOUGH2 used for non-isothermal multi-phase fluid and heat flow in porous and fractured media, the heat transport mathematical model of low-temperature shallow geothermal system is set up in homogeneous porous medium. The fundamental scientific issues on heat transfer characteristics and distribution of transient temperature field of heat exchange wells in summer is discussed in this paper. In addition, the significance and correlation between the changes of hydrogeology parameters and temperature field of the soil is analyzed. So as to the practical application of geothermal energy development can be guided by the achievements of the research.

Phase-field simulation of dendritic growth in a forced liquid metal flow coupling with boundary heat flux

A phase-field model with forced liquid metal flow was employed to study the effect of boundary heat flux on the dendritic structure forming of a Ni-40.8%Cu alloy with liquid flow during solidification. The effect of the flow field coupling with boundary heat extractions on the morphology change and distributions of concentration and temperature fields was analyzed and discussed. The forced liquid flow could significantly affect the dendrite morphology, concentration and temperature distributions in the solidifying microstructure. And coupling with boundary heat extraction, the solute segregation and concentration diffusion were changed with different heat flux. The morphology, concentration and temperature distributions were significantly influenced by increasing the heat extraction, which could relatively make the effect of liquid flow constrained. With increasing the initial velocity of liquid flow, the lopsided rate of the primary dendrite arm was enlarged and the transition of developing manner of the secondary arms moved to the large heat extraction direction. It was the competition between heat flux and forced liquid flow that finally determined microstructure forming during solidification.

Hydrodynamic Characteristics in a Valley Type Tributary Bay during the Raising and Falling Temperature Periods

The heat changes and distribution in water body provide one of the most important elements of structure influencing a host of chemical and biological processes. After the river-type reservoir was constructed, backwater entered into some tributaries, resulting in slow flow velocities in these tributaries. This paper made a reasonable description on the physical mechanism of hydrodynamic and water temperature distributions in a typical tributary bay, basing the hydrodynamic & water temperature coupled three-dimensional mathematical model. Through a large number of measured hydrologic, temperature and meteorological data, the paper simulated and obtained the hydrodynamic and water temperature distribution structure of the typical tributary bay and its evolution process, and described the hydrodynamic characteristics with precise values during the raising and falling temperature period; it is shown from the results that velocity vectors change displayed the water flow moved in a two-way circulation due to non-equilibrium warming and cooling on riverway cross-section, and the maximum flow velocity, turbulent kinetic energy and vorticity appeared on the surface water body, as well as wall near the tributary bay, and the turbulent kinetic energy is minimum on the center of tributary bay. The simulation experiment accurately captured the circulation phenomena caused by temperature difference, and proposed detailed distributions of flow field and related turbulent physical quantity, showed the strong coupling of flow field and temperature field change.

Smart metamaterials with tunable auxetic and other properties

Auxetic and other mechanical metamaterials are typically studied in situations where they are subjected solely to mechanical forces or displacements even though they may be designed to exhibit additional anomalous behaviour or tunability when subjected to other disturbances such as changes in temperature or magnetic fields. It is shown that externally applied magnetic fields can tune the geometry and macroscopic properties of known auxetics that incorporate magnetic component/s, thus resulting in a change of their macroscopic properties. Anomalous properties which are observed in such novel magneto-mechanical systems include tunable Poisson’s ratios, bi-stability or multi-stability, depending on the applied magnetic fields, and other electromagnetic–mechanical effects such as strain dependent induced electric currents and magnetic fields. The properties exhibited depend, amongst other things, on the relative position and orientation of the magnetic insertion/s within the structure, the geometry of the system and the magnetic strength of the magnetic components, including that of the external magnetic field.

Numerical Simulation of Cavity Flow within the Flow Field

Analysis of numerical simulation was used on flow field and temperature field in mechanical seal cavity. It borrowed a new calculation method, which was more visual and simpler than before. And this method analysed the change in temperature field of mechanical seal ring and the distribution of temperature and pressure in the flow field when mechanical seal was working. The result showed that the numerical simulation method was effect to the flow field in centrifugal pump.

Laboratory and Flight Test Analysis of Rubidium Frequency Reference Performance

The performance of Rubidium frequency standards is well-documented for stationary operation. In dynamic environments that include changes in orientation, acceleration, temperature, pressure, and magnetic field, the performance of frequency references for position, velocity, and timing applications is not well characterized in the literature. This paper includes results from laboratory and flight test experiments. Laboratory tests were conducted to characterize Rubidium oscillator performance under varying gravity and magnetic field conditions. Three Rubidium oscillators were flight tested. Each of the oscillators was connected to a GPS receiver for error characterization. The frequency stability performance is profiled against the flight dynamics based on a navigation-grade inertial navigation system. The goal of the paper is to increase the awareness of Rb oscillator error sources that affect in-flight frequency stability, with an emphasis on gravity sensitivity and magnetic field susceptibility. Copyright © 2013 Institute of Navigation.

Simulation Analysis of Groundwater Source Heat Pump’s Underground Temperature Field Changes under Different Pumping and Injecting wells Modes

Through the establishment of the coupled model of groundwater flow and temperature, the changing tread of groundwater temperature and the basic characteristics of thermal breakthrough under the different layout wells modes were simulated and analyzed. The results showed that, the similar wells distance didn’t affect the thermal breakthrough significantly, the distance of pumping wells and irrigating wells affected pumping temperature significantly and thermal breakthrough. The more number of pumping and injecting didn’t extend the time of thermal breakthrough, and didn’t affect pumping temperature significantly from the results of long-running, the layout pattern of wells with one pumping and two injecting presented significant advantages in practical engineering.

Simulation of dynamic temperature field during selective laser sintering of ceramic powder

It is difficult to obtain the dynamic temperature field and the variation pattern with the experimental method as the temperature field changes very fast in the laser sintering process. In this study, a mathematical model for the dynamic temperature field was established during selective laser sintering (SLS) with nano-hydroxyapatite (HAP) ceramic powder. The dynamic loading of a moving laser heat source with a Gaussian distribution was realized with ANSYS Parameter Design Language. The variation pattern of a three-dimensional transient temperature field at different speeds of the moving laser heat source was analysed as the change of thermal physical parameters with temperature was taken into account in the developed model. The results show that the maximum temperature point on the sintered layer surface is slightly lagged from the laser spot centre with the moving laser heat source when the offset distance is 0.4 mm, laser power is 10 W, laser spot diameter is 2 mm and laser speed is 200 mm/min. The temperature decreases rapidly with the increase of sintering depth. The temperature field that the characteristic microstructure of the sintered parts represents coincides with that by the analysis with finite element calculation. This study may provide useful guidance for selecting the reasonable processing parameters during SLS.

Structure evolution and entropy change of temperature and magnetic field induced magneto-structural transition in Mn1.1Fe0.9P0.76Ge0.24

The compound Mn1.1Fe0.9P0.76Ge0.24 has been studied using neutron powder diffraction (NPD), differential scanning calorimeter (DSC), and magnetic measurements, in order to clarify the nature of the magnetic and structural transition and measure the associated entropy change (ΔS). The strongly first order transition occurs from a paramagnetic (PM) to a ferromagnetic (FM) phase and can be induced either by temperature or by an applied magnetic field. Our investigations indicate that the two processes exhibit identical evolutions regarding the crystal and magnetic structures, indicating they should have the same entropy change. We, therefore, conclude that the ΔSDSC obtained by the DSC method (where the transition is temperature induced) is valid also for the magnetically induced transition, thus avoiding uncertainties connected with the magnetic measurements. We have obtained the ΔSDSC = 33.8 J/kg · K for this sample upon cooling, which would increase to 42.7 J/kg · K for a impurity-free and completely homogeneous sample. For comparison, the magnetic entropy changes (ΔSM) induced by magnetic field and calculated using the Maxwell relation yields a ΔSM = 46.5J/kg · K, 38% higher than ΔSDSC. These entropy results are compared and discussed.

Dependence of century-scale projections of the Greenland ice sheet on its thermal regime

AbstractObservations show that the Greenland ice sheet has been losing mass at an increasing rate over the past few decades, which makes it a major contributor to sea-level rise. Here we use a three-dimensional higher-order ice-flow model, adaptive mesh refinement and inverse methods to accurately reproduce the present-day ice flow of the Greenland ice sheet. We investigate the effect of the ice thermal regime on (1) basal sliding inversion and (2) projections over the next 100 years. We show that steady-state temperatures based on present-day conditions allow a reasonable representation of the thermal regime and that both basal conditions and century-scale projections are weakly sensitive to small changes in the initial temperature field, compared with changes in atmospheric conditions or basal sliding. We conclude that although more englacial temperature measurements should be acquired to validate the models, and a better estimation of geothermal heat flux is needed, it is reasonable to use steady-state temperature profiles for short-term projections, as external forcings remain the main drivers of the changes occurring in Greenland.

Measurement of Temperature Field for the Spindle of Machine Tool Based on Optical Fiber Bragg Grating Sensors

The change of spindle temperature field is an important factor which influences machining precision. Many methods of spindle temperature field measurement have been proposed. However, most of the methods are based on the electric temperature sensors. There exist some defects (e.g., anti-interference, multiplexing, and stability capacity are poor). To increase the temperature sensitivity and reduce strain sensitivity of the bare Fiber Bragg Grating (FBG) sensor, a cassette packaged FBG sensor is proposed to measure spindle temperature field. The temperature characteristics of the packaged FBG sensor are studied by comparative experiment with traditional thermal resistor sensor. The experimental results show that the packaged FBG sensor has the same capacity of temperature measurement with the thermal resistor sensor but with more remarkable antiinterference. In the further measurement experiment of the temperature field, a spindle nonuniform temperature field is acquired by the calibrated FBG sensors. It indicates that the packaged FBG sensor can be used to measure the temperature field for the spindle of machine tool.

Validation of a Heat Input Model for the Prediction of Thermomechanical Deformations during NC Milling

During roughing in NC milling, heat is introduced into the workpiece. For the manufacturing of large structural components, a constantly changing temperature field is created due to the rapid movement and the varying contact conditions between tool and workpiece. Therefore, significant deformations can cause form errors that lead to rejects in the production process. In this paper, a simulation system for the prediction of transient workpiece temperatures is presented. In order to calibrate the system, simple experiments have been conducted, and a model for the introduction of energy into the workpiece via cutting has been developed. The newly developed cutting-energy input model makes it possible to perform fast simulations. Therefore, it can be used to perform simulations of the thermoelastic workpiece deformations during milling of complex shaped parts.

Laser Transmission Welding of Thermoplastics With Dual Clamping Devices

Abstract Beside well chosen process parameters a geometrical joining partner design suitable for laser transmission welding and adequate clamping pressure appliance is necessary to form high quality welds. Amongst other clamping techniques Dual Clamping Devices (DCD) are a promising approach to fulfill the process needs and to get to a robust and also fail safe clamping. When using DCD the laser beam has to pass thin non transmitting bars while a weld seam is formed. So the laser beam is partial refracted, reflected and absorbed. Here the influences of the bars onto the laser beam intensity distribution behind the bars rather in the interaction zone of the laser beam and the two joining partners are investigated. Welding experiments with DCD are carried out and discussed. Based on the experimental results thermal process simulations are performed, to get a deeper knowledge about the effect of the bars onto the spatially and temporally changing temperature field within the joining partners.

Isothermal and non-isothermal viscoelastic flow of PTT fluid in lid-driven polar cavity

The isothermal and non-isothermal viscoelastic flow of Phan-Thien-Tanner (PTT) fluids is considered in liddriven polar cavity geometry, using a numerical solution method with parameter continuation technique. Thermoelastic effects, in terms of elastic/elongational effects and viscous dissipation, are demonstrated by the changes in vortical structure, temperature/stress distributions and heat transfer characteristics in the curved cavity. Central vortex/maximum temperature location shifts are observed under elastic and elongational (strain hardening and strain softening/shear thinning) effects for isothermal and non-isothermal conditions. The growth in size and strength of a secondary vortex is denoted in the downstream stationary corner of the cavity for the viscoelastic fluid under strain hardening, which also introduces an increase in stress gradients. Viscous heating is observed with elongational effects near the central vortex in the cavity. Stress components and their gradients decrease under viscous dissipation. The changes in temperature field and heat transfer properties in the cavity are revealed.

Experimental Research on the Temperature Field of High and Hollow-Thin Pier

To study the temperature field changing regulation of hydration heat and control concrete cracks caused by great temperature difference in the construction of hollow-thin pier, testing the temperature field of the high and hollow-thin pier of Cha Jiugou Bridge and it got changing regulation of the temperature. The finite element analysis on the pier was also carried out and the temperature stress contours and curves of the hydration heat of the concrete are obtained. It can be seen that the outer surface and the center of the pier are compressive within 10 hours in the pouring early. With the temperature difference, the center generates the compressive stress, the surface generates tensile stress.

Simulation on Parameters Temperature Field by Gas-Solid Coupling in Goaf

For solution the complex and rapidly changing question of temperature field in mining goaf, the simulation on dynamic temperature field of parameters coupling is carried out under different working coditions based on high-efficiency finite volume method (FVM) and the moving characteristic of working face. The theory analysis, the laboratory experiment, the simulation of software and the example confirmation, above all methods are used in order to find the change of temperature field in goaf. The result is found that there has spontaneous combustion in goaf when the moving speed of working face is below 1.2m/d; besides that the temperature in goaf fall and the high-temperature region is extend to the deep of goaf. Another result is exist that there has the linear increase relationship of the intensity of leak air and the temperature in goaf, and the high-temperature region is extend to the deep of goaf contrary to the effect of the coal oxidation properties, which increases the risk of coal spontaneous combustion in goaf. Especially , all the data of temperature is visualization by picture of 3D, so the distribution map of temperature in goaf is visualized distinctly. The research results provide a theoretical basis for understanding the real situation and preventing spontaneous combustion in goaf.