Study on Temperature Distribution and Smoke Spreading Behavior of Different Fire Source Locations in the UnderwaterW-Shaped Island-Crossing Tunnel

Called island-crossing tunnels,some specific underwater tunneling projects face constraints imposed by geological and water conditions,necessitating their passage through artificial or natural islands.The longitudinal of the tunnel follows aW-shaped distribution.The congestion situation does not allowfor immediate longitudinal smoke exhaust at the early stage of the fire,and the natural spread of smoke is complicated.An exhaustive investigation was carried out to analyze the smoke behaviors during a fire incident,employing the fire dynamics software FDS,considering five slopes and four fire locations.The simulation results reveal that the layer of high-temperature smoke becomes thicker as one gets closer to the fire source.The thermal pressure difference significantly impacts the temperature distribution within the tunnel and the distance of smoke spread.The value of the thermal pressure difference is significantly affected by changes in slope.It reaches a maximum of 157 Pa at a 5%slope,while it is only 41 Pa at a 1%slope when the fire occurs at the V-point.Fire hazards vary across locations within the W-shaped tunnel,necessitating separate consideration of the V-point and inverted V-point fire characteristics.The mass flow rate in small and large slope tunnels shows different decay rates due to variations in the main forces acting on the movement.Hence,two equations have been developed to predict the smoke mass flow rate,indicating a nonlinear relationship with the tunnel slope and the distance fromthe fire source.The tunnel slope inversely affects the smoke mass flowrate at the same location.The results can be utilized as a reference for conducting evacuation operations and aiding rescues during aW-shaped tunnel fire.

Numerical Analysis on Temperature Distribution in a Single Cell of PEFC Operated at Higher Temperature by1D Heat Transfer Model and 3D Multi-Physics Simulation Model

This study is to understand the impact of operating conditions, especially initial operation temperature (Tini) which is set in a high temperature range, on the temperature profile of the interface between the polymer electrolyte membrane (PEM) and the catalyst layer at the cathode (i.e., the reaction surface) in a single cell of polymer electrolyte fuel cell (PEFC). A 1D multi-plate heat transfer model based on the temperature data of the separator measured using the thermograph in a power generation experiment was developed to evaluate the reaction surface temperature (Treact). In addition, to validate the proposed heat transfer model, Treact obtained from the model was compared with that from the 3D numerical simulation using CFD software COMSOL Multiphysics which solves the continuity equation, Brinkman equation, Maxwell-Stefan equation, Butler-Volmer equation as well as heat transfer equation. As a result, the temperature gap between the results obtained by 1D heat transfer model and those obtained by 3D numerical simulation is below approximately 0.5 K. The simulation results show the change in the molar concentration of O2 and H2O from the inlet to the outlet is more even with the increase in Tini due to the lower performance of O2 reduction reaction. The change in the current density from the inlet to the outlet is more even with the increase in Tini and the value of current density is smaller with the increase in Tini due to the increase in ohmic over-potential and concentration over-potential. It is revealed that the change in Treact from the inlet to the outlet is more even with the increase in Tini irrespective of heat transfer model. This is because the generated heat from the power generation is lower with the increase in Tini due to the lower performance of O2 reduction reaction.

Numerical simulation of downhole temperature distribution in producing oil wells

An improved numerical simulation method is presented to calculate the downhole temperature distribution for multiple pay zones in producing oil wells. Based on hydrodynamics and heat transfer theory, a 2-D temperature field model in cylindrical coordinates is developed. In the model, we considered general heat conduction as well as the heat convection due to fluid flow from porous formation to the borehole. We also take into account the fluid velocity variation in the wellbore due to multiple pay zones. We present coupled boundary conditions at the interfaces between the wellbore and adjacent formation, the wellbore and pay zone, and the pay zone and adjacent formation. Finally, an alternating direction implicit difference method （ADI） is used to solve the temperature model for the downhole temperature distribution. The comparison of modeled temperature curve with actual temperature log indicates that simulation result is in general quite similar to the actual temperature log. We found that the total production rate, production time, porosity, thickness of pay zones, and geothermal gradient, all have effects on the downhole temperature distribution.

Study of Temperature Distribution Along an Artificially Polluted Insulator String

Insulator becomes wet partially or completely, and the pollution layer on itbecomes conductive, when collecting pollutants for an extended period during dew, light rain, mist,fog or snow melting. Heavy rain is a complicated factor that it may wash away the pollution layerwithout initiating other stages of breakdown or it may bridge the gaps between sheds to promoteflashover. The insulator with a conducting pollution layer being energized, can cause a surfaceleakage current to flow (also temperature-rise). As the surface conductivity is non-uniform, theconducting pollution layer becomes broken by dry bands (at spots of high current density),interrupting the flow of leakage current. Voltage across insulator gets concentrated across drybands, and causes high electric stress and breakdown (dry band arcing). If the resistance of theinsulator surface is sufficiently low, the dry band arcs can be propagated to bridge the terminalscausing flashover. The present paper concerns the evaluation of the temperature distribution alongthe surface of an energized artificially polluted insulator string.

Effect of pulsed current on temperature distribution,weld bead profiles and characteristics of gas tungsten arc welded aluminum alloy joints

Temperature distribution and weld bead profiles of constant current and pulsed current gas tungsten arc welded aluminium alloy joints were compared. The effects of pulsed current welding on tensile properties, hardness profiles, microstructural features and residual stress distribution of aluminium alloy joints were reported. The use of pulsed current technique is found to improve the tensile properties of the weld compared with continuous current welding due to grain refinement occurring in the fusion zone.

Temperature distribution study during the friction stir welding process of Al2024-T3 aluminum alloy

Heat flux characteristics are critical to good quality welding obtained in the important engineering alloy A12024- T3 by the friction stir welding （FSW） process. In the present study, thermocouples in three different configurations were amxed on the welding samples to measure the temperatures： in the first configuration, four thermocouples were placed at equivalent positions along one side of the welding direction; the second configuration involved two equivalent thermocouple locations on either side of the welding path; while the third configuration had all the thermocouples on one side of the layout but with unequal gaps from the welding line. A three-dimensional, non-linear ANSYS computational model, based on an approach applied to A12024-T3 for the first time, was used to simulate the welding temperature profiles obtained experimentally. The experimental thermal profiles on the whole were found to be in agreement with those calculated by the ANSYS model. The broad agreement between the two kinds of profiles validates the basis for derivation of the simulation model and provides an approach for the FSW simulation in A12024-T3 and is potentially more useful than models derived previously.

Effect of contact thermal resistance on temperature distributions of concrete-filled steel tubes in fire

To predicate the temperature distribution of concrete-filled steel tubes(CFSTs) being exposure to fire,a finite element analysis model was developed using a finite element package,ANSYS.A suggested value of contact thermal resistance was therefore proposed with the supporting of massive numbers of collected test data.Parametric analysis was conducted subsequently towards the cross-sectional temperature distribution of CFST columns in four-side fire,in which the exposure time,width of the cross section,steel ratio were taken into account with considering contact thermal resistance.It was found that contact thermal resistance has little effect on the overall temperature regulation with the exposure time,the width of cross-section or the change of steel ratio.However,great temperature dropping at the concrete adjacent to the contact interface,and gentle temperature increase at steel tube,exist if considering contact thermal resistance.The results of the study are expected to provide theoretical basis for the fire resistance behavior and design of the CFST columns being exposure to fire.

Microstructure and Temperature Distribution in ZnAl_2O_4 Sintered Body by Pulse Electric Current

Microstructure of reaction sintering of ZnAl2O4 at 1500℃ by hot-pressing(HP) and pulse electric current was investigated. The results indicated that the existed cracks in sintered body were caused by structure mismatch. It is the evidence that periodical temperature field existed during pulse electric current sintering of nonconductive materials. The distance between high temperature areas was related to die diameter.

Temperature Distribution and Scuffing of Tapered Roller Bearing

In the field of aerospace, high-speed trains and automobile, etc, analysis of temperature filed and scuffing failure of tapered roller bearings are more important than ever, and the scuffing failure of elements of such rolling bearings under heavy load and high speed still cannot be effectively predicted yet. A simplified model of tapered roller bearings consisted of one inner raceway, one outer raceway and a tapered roller was established, in which the interaction of several heat sources is ignored. The contact mechanics model, temperature model and model of scuffing failure are synthesized, and the corresponding computer programs are developed to analyze the effects of bearings parameters, different material and operational conditions on thermal performance of bearings, and temperature distribution and the possibility of surface scuffing are obtained. The results show that load, speed, thermal conductivity and tapered roller materials influence temperature rise and scuffing failure of bearings. Ceramic material of tapered roller results in the decrease of scuffing possibility of bearings to a high extent than the conventional rolling bearing steel. Compared with bulk temperature, flash temperature on the surfaces of bearing elements has a little influence on maximum temperature rise of bearing elements. For the rolling bearings operated under high speed and heavy load, this paper proposes a method which can accurately calculate the possibility of scuffing failure of rolling bearings.

Effects of pin angle and preheating on temperature distribution during friction stir welding operation

Friction stir welding （FSW） is applied extensively in industry for joining of nonferrous metals especially aluminum. A three-dimensional model based on finite element analysis was used to study the thermal characteristic of copper C I 1000 during the FSW process. The model incorporates the mechanical reaction of the tool and thermo-mechanieal characteristics of the weld material, while the friction between the material and the probe and the shoulder serves as the heat source. It was observed that the predicted results about the temperature were in good compatibility with the experimental results. Additionally, it was concluded that the numerical method can be simply applied to measuring the temperature of workpiece just beneath the tool. The effects of preheating temperature and pin angle on temperature distribution were also studied numerically. The increase of pin angle enhances the temperature around the weld line, but preheating does not affect temperature distribution along the weld line considerably.

Visualization of 3-D temperature distribution in a 300 MW twin-furnace coal-fired boiler

Until now, it has been difficult to obtain on-line three-dimensional (3-D) temperature distribution information which can reflect the overall combustion condition in the furnace of a coal-fired power plant boiler. A combustion monitoring system is introduced which can solve the problem efficiently. Through this system, the 3-D temperature distribution in a coal-fired boiler furnace can be obtained using a novel flame image processing technique. Briefly, we first outline the visualization principle. Then, the hardware and software design of the system in a 300 MW twin-furnace coal-fired boiler are introduced in detail. The visualization of the 3-D temperature distribution in the twin-furnace boiler is realized with an industrial computer and the Distributed Control System (DCS) of the boiler. The practical operation of the system shows that it can provide valuable combustion information of a furnace and is useful for the combustion diagnosis and adjustment in coal-fired power plants.

Flow Pattern and Temperature Distribution in HMCZ Silicon Melt

The axial and radial convective flow,temperature fluctuation and distribution in the HMCZ silicon melt are studied tentatively.The experimental results show that the axial and radial convective speeds,the tempera- ture variation and the radial temperature gradient,parallel to magnetic field and near melt surface,all decrease,but the axisymmetry of temperature distribution no longer exists when the magnetic field is applied.

Temperature Distribution and Heat Flux on the EAST Divertor Targets in H-Mode

An infrared camera （IR） has been put into operation in the Experimental Advanced Superconducting Tokamak （EAST）, which is used to measure the temperature distribution on the surface of lower divertor target plates. With a finite difference method, the heat flux onto the divertor target plates is calculated from the surface temperature profile. The high confinement mode （H-mode） with type-III edge localized modes （ELMs） has been obtained with about 1 MW lower-hybrid wave power on the EAST in the autumn experiment in 2010. The analyzed H-mode discharges were lower single null X-point diverted discharges with a density range of 〈 ne 〉 （1 - 4） × 10^19 m-3. The surface temperature of the inner target plate increases with heating power. The peak temperature on the surface of target plates is lower than 200 ~C with about 2.4 MW heating power. Comparison among the heat flux profiles occurring in different phases in the same discharge has been performed. It indicates that the heat flux profile obviously changes from the ohmic phase to the H-mode phase, and the full width at half maximum （FWHM） of the heat flux profile is the narrowest during the ELM-free H-phase. On the outer target plate, the peak heat flux exceeds 2 MW/m2 during the ELMy H-mode phase, whereas it is only about 0.8 MW/m2 during the ELM-free phase in the same discharge.

Determination of temperature distribution and control parameter in a two-dimensional parabolic inverse problem with overspecified data

In this paper, we present a new algorithm to solve a two-dimensional parabolic inverse problem with a source parameter, which appears in many physical phenomena. A linearized compact difference scheme for this problem is constructed using the finite difference method. The discretization accuracy is second-order in time and fourth-order in space. We obtain the unique solvability and present an alternating direction implicit algorithm to solve this difference scheme. The results of numerical experiments are presented to demonstrate the accuracy of this algorithm.

Investigation on the temperature distribution and strength of flat steel ribbon wound cryogenic high-pressure vessel

By analyzing heat transfer on the wall of fiat steel ribbon wound vessel （FSRWV）, a numerical model of temperature distribution on the entire wall （including inner core wall, flat steel ribbons, outside cylinder of jacket and insulating layer） was established by the authors. With the model, the temperature distribution and the length change in the vessel walls and flat steel ribbons in low temperature are calculated and analyzed. The results show that the flat steel ribbon wound cryogenic high-pressure vessel is simpler in structure, safer and easier to manufacture than those of conventional ones.

Simulation study on reconstruction model of three-dimensional temperature distribution within visible range in furnace

This paper presents a reconstruction model of three-dimensional temperature distribution in furnace based on radiative energy images captured by charge-coupled device （CCD） cameras within the visible wavelength range. Numerical simulation case was used in this study and a zigzag eccentric temperature distribution was assumed to verify the model. Least square QR-factorization （LSQR） method was introduced to deal with reconstruction equation. It is found that the reconstructed temperature distributions in low-temperature areas had some fluctuations and high-temperature areas were reconstructed well. The whole reconstruction relative error was mainly due to errors in low-temperature areas and the relative error for highest-temperature reconstruction was quite small.

Temperature distributions in concrete box girders due to heat of concrete hydration

Based on heat transfer theory,a two-dimensional complex exponential function was used to compute heat of concrete hydration.A concrete box girder consisting of a single box with two cells used on Harbin Songpu Bridge was measured on site.The two coefficients in the complex exponential function were determined to best fit the field measured data.ABAQUS program was used to simulate the heat transfer and determine the temperature distribution in the concrete box girders during concrete setting.The calculated temperature distribution in the box girders were compared with the field measured data and good agreement was observed.The temperature distribution and gradient in the entire box section,webs and bottom slab were analyzed using the measured and calculated results during the course of concrete hydration.

Study on visualization simulation of temperature distributions in surrounding rock of tunnels in a deep mine

Based on the mathematical model for rock temperature distribution in a geo-thermal field,the properties of rock temperature distribution in geothermal field for fourkinds of surrounding rock cross-sections of tunnels in a deep mine were simulated by us-ing finite element method.It is shown that the relationship for rock temperature distributionvaried with the geothermal parameters,time and space.Namely, 2-dimensionaltime-dependent isograms clearly showed the process for rock temperature variation anddistribution in a geothermal field which has been redisplayed with visualization numericalsimulation.

3-D temperature distribution of a full size BF copper stave with oblate channel

An experiment of a new type full size copper stave for a real blast furnacewas carried out in a special-designed experimental system. The 3-D temperature distribution insidethe stave including isotherm was obtained based on the experiment data. And the effects of thetemperature of cooling water and the velocity of the water as well as the temperature of the furnaceon the 3-D temperature distribution were obtained. The experimental and calculation results showthat the highest temperature of the hot surface is lower than 90 deg C which is very good for thesolidified slag formation on the hot surface and protecting the stave.

Analysis on Temperature Distributions in Single Cell of Polymer Electrolyte Fuel Cell When Operated in High Temperature Range

This study is to understand the impact of operating condition, especially initial operation temperature （Tini） which is set in high temperature range, on the temperature profile of the interface between PEM （polymer electrolyte membrane） and catalyst layer at the cathode （i.e., the reaction surface） in a single PEFC （polymer electrolyte fuel cell）. A 1D multi-plate heat transfer model based on the temperature data of separator measured using thermograph in a power generation experiment was developed to evaluate the reaction surface temperature （Treact）. This study investigated the effects of flow rate, relative humidity and type of supply gas as well as Tini on the temperature distribution on reaction surface. The results obtained in 02 supply case show that, the temperature rise at the segments near the outlet of cell decreases with increasing Tini irrespective of relative humidity of supply gas （RH）, while it is not seen in air supply case. Regarding the segments except near the outlet in 02 supply case, Treact - Tini increases with increasing Tini for 40% RH. The temperature distribution on reaction surface in 02 supply case is wider with increasing Tini as well as decreasing RH, though that in air supply case is relatively even.