Types Of Heat Sources Research Articles

Investigation on weldability of magnesium alloy thin sheet T-joints: arc welding, laser welding, and laser-arc hybrid welding

Four welding methods, including laser welding, gas tungsten arc (GTA) welding, laser–GTA hybrid welding, and laser–GTA hybrid welding with cold welding wire, are used to investigate the weldability of T-joints of magnesium alloy thin sheet. Stake welding process is presented in this paper in order to overcome the defects, such as stress concentration and deformation, and improve the accessibility of T-joints in fillet welding process. The effect of heat source type on weldability of T-joints is analyzed. The microstructures and mechanical properties are investigated. Experimental results indicate that comparing with the other three welding methods, laser–GTA hybrid welding with cold welding wire is the most effective process for T-joints of magnesium alloy thin sheet. In this process, T-joints are full penetration and the toes are smooth and round, and besides, reinforcement forms on the upside of weld bead by the filled wire. The mechanical properties of T-joints made with laser–GTA hybrid welding with cold welding wire achieve 90 % of that of base metal and are superior to that without welding wire.

ChemInform Abstract: Design of Particles by Spray Pyrolysis and Recent Progress in Its Application

AbstractReview: 158 refs.

Periodically varying heat source response in a functionally graded microelongated medium

The present paper deals with the response due to periodically varying heat sources in the neighborhood of the origin of a functionally graded isotropic unbounded microelongated medium, in the context of generalized thermoelastic theory. The expressions for displacement, microelongation and temperature fields have been obtained in Laplace–Fourier transformed domain. After computing the inverse Fourier transforms by contour integration technique, the inversion of Laplace transforms has been obtained numerically. The changes of displacement, microelongation, and normal strain have been shown graphically for different types of heat source.

Effects of grilling and roasting on the levels of polycyclic aromatic hydrocarbons in beef and pork

The concentrations of seven polycyclic aromatic hydrocarbons (PAHs) viz. chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, and indeno(1,2,3-c,d)pyrene in 150 samples of commercial meat products were determined. The PAHs were extracted with hexane, purified with Sep-Pak Florisil cartridges and determined by high-performance liquid chromatography using a fluorescence detector. Levels of PAHs were dependent on the method of cooking and type of heat source used. Relatively high levels of PAHs, 10.2μg/kg on average, were found in charcoal-grilled pork samples. Average PAH levels in beef did not exceed 0.80μg/kg. Charcoal grilling of pork samples resulted in extremely high levels of benzo(a)pyrene (3.0μg/kg), while the average benzo(a)pyrene levels in charcoal-grilled beef samples were 0.15μg/kg. These data can be used to estimate the dietary exposure of consumers to PAHs and to assess any potential risk associated with the ingestion of these foods.

Modeling Heat Transfer in Thin Fire Blanket Materials under High External Heat Fluxes

To investigate the performance of thin fire blanket materials for house protection from wildland fires, a one-dimensional numerical model, which combines conductive and radiative heat transfer, has been developed, solved and compared with bench-scale experiments. Two types of incident heat sources are studied: convective heating from a burner flame and radiative heating from a cone heater. Radiative heat exchange between the blanket and the environment is critical in the performance of the blankets at high temperatures. The treatment of radiation includes the solution of radiative transfer equation by discrete ordinate method since in-depth absorbing, emitting and scattering are believed to be important in these thin blanket materials. A number of material combinations were tested and analyzed, including single and double layers of fiberglass fabric with and without aluminum foil on the front and back surfaces. It is found that high heat-blocking efficiencies can be obtained using thin blankets. Interestingly, it is also found that protecting a house from convective heating is a more difficult challenge than protecting it from radiant heating.

Modeling Heat Transfer in Thin Fire Blanket Materials under High External Heat Fluxes

To investigate the performance of thin fire blanket materials for house protection from wildland fires, a one-dimensional numerical model, which combines conductive and radiative heat transfer, has been developed, solved and compared with bench-scale experiments. Two types of incident heat sources are studied: convective heating from a burner flame and radiative heating from a cone heater. Radiative heat exchange between the blanket and the environment is critical in the performance of the blankets at high temperatures. The treatment of radiation includes the solution of the radiative transfer equation by the discrete ordinate method since in-depth absorbing, emitting and scattering are believed to be important in these thin blanket materials. A number of material combinations were tested and analyzed, including single and double layers of fiberglass fabric with and without aluminum foil on the front and back surfaces. It is found that high heat-blocking efficiencies can be obtained using thin blankets. Interestingly, it is also found that protecting a house from convective heating is a more difficult challenge than protecting it from radiant heating.

Design of particles by spray pyrolysis and recent progress in its application

Spray pyrolysis is a promising aerosol process to produce “designer particles” of precisely controlled morphology with decorations on surfaces or inside particles. Need of precise control of properties has sparked researches on aerosol process that may replace conventional processes such as solid state reaction process or liquid precipitation method. However, productivity is the biggest obstacle in the development of a commercial scale process because the aerosol process is essentially operated at low particle concentration compared to liquid phase processes. In this review, by reviewing publications for the last 10 years we discuss how researchers on spray pyrolysis circumvent this inherent limitation of the aerosol process. First, the process of particle design by spray pyrolysis is introduced. Some key criteria are explained for selecting each component of spray pyrolysis: precursor, additive, carrier gas, heat source, and reactor type. Second, key contributions of major groups in Korea, Japan, Europe, and America are described. Third, some of named processes to overcome productivity of spray aerosol process are introduced. Fourth, applications of spray pyrolysis to materials related to alternative energy, environmental cleaning, information processing and display, and biomaterials are considered. Finally, future prospects of spray pyrolysis are discussed along with current standing issues for further progress of spray pyrolysis.

Study of species, temperature distributions and the solid oxide fuel cells performance in a 2-D model

A two-dimensional mathematical model for a planar SOFC (solid oxide fuel cell) is constructed. The distribution of the chemical species, the temperature and the performance (power) and the current density were calculated using a single-unit model with double channels of co-flow pattern. The finite volume method was employed for the calculation. The method was based on the fundamental conservation laws of continuity, momentum, energy and mass. The equations are implemented in FORTRAN language. The effects of several heat sources and flow rates on the calculated results were also investigated. The reference SOFC polarization curve has been calculated by imposing a uniform temperature of 800 K, a pressure equal to 1 atm; H2 and O2 molar fractions equal to 0.97 and 0.21 respectively. Results of temperature, chemical species distributions, performance and efficiency under several heat sources are shown and discussed. At a current density of about 23500 A/m2, the power densities under all sources and chemical sources reached their maximums of 12965 W/m2 and 16209 W/m2 (i.e. 25% lower) respectively. However the temperature increment in the anode is analyzed toward all sources and chemical reaction. The temperature maximum values for each heat source type reached 1005.81 K and 984.69 K respectively.

Effects of Different Heat Flux Schemes in Modelling of Transport Phenomena during Gas Tungsten Arc Welding of AA1050

A three-dimensional model is utilized to predict temperature distribution and fluid flow during the process of gas tungsten arc welding (GTAW). In order to evaluate the effect of the heat flux model on the accuracy of predictions, two types of heat sources — with different natures based on Gaussian surface heat flux and volumetric Goldak's double-ellipsoid heat flux distributions — are taken into account. These heat flux schemes are input into a model simulation of GTAW of AA1050. In the next stage, the transient temperature distribution within the metal being welded is predicted for each heat flux model using FLUENT computational fluid dynamics software. The fusion and heat-affected zones are then determined and compared with each other as well as with experimental observations. The results show that the distribution and intensity of heat flux over the top surface of a workpiece have an important effect on the shape and dimensions of predicted weld pool geometry. Furthermore, the double-ellipsoid heat flux model results produced more realistic data than the Gaussian surface heat flux distribution for the welding conditions considered here.

Effects of heat sources on the performance of a planar solid oxide fuel cell

This paper presents an analysis of the effects of heat sources on performance of a planar anode-supported solid oxide fuel cell (SOFC). Heat sources in SOFCs include ohmic heat losses, heat released by chemical and electrochemical processes and radiation. We take into account the first three types of heat source here while neglecting the last type as it is supposed to be negligibly small. The cell is working under conditions of direct internal reforming of methane and with co-flow configuration. The composite electrodes are discretized allowing the heat source associated with the electrochemical processes to be implemented in a layer of finite thickness. Two cases are investigated, one where the electrochemical heat source is implemented on the anode side (base case) and another where it is implemented on the cathode side. Results for temperature, current density and chemical species distribution of the base case are shown and discussed. Moreover, the effects of magnitude and location of the heat sources are discussed. The results show that including ohmic heating in the cell model does have a significant effect on the predicted cell performance. Comparisons between the two cases indicate that the location of the electrochemical heat source does not affect the cell performance.

Temperature field, H2 and H2O mass transfer in SOFC single cell: Electrode and electrolyte thickness effects

Abstract The temperature increment in electrodes and electrolyte of a fuel cell is mainly attributed to the chemical reaction and the irreversibilities. The aim of this work is to study the increasing temperature of a SOFC single cell under the influence of the electrode and electrolyte thicknesses for its type of heat source. The hydrogen and water field are also discussed according to anode thickness. The results of a self-developed mathematical model show the increasing temperature in the solid side of SOFC; anode, electrolyte and cathode by heat source types “Joule effect” at the several geometric configurations of SOFC. The maximum temperature value is also discussed for several cathode thicknesses under the activation polarization effect. Moreover, mass transfer for both hydrogen and water is studied according to anode thickness.

Temperature field and ventilation simulation of stope in Hongtoushan mine

Hongtoushan copper mine was studied by analyzing the type of heat source, the calculation method about thermal releasing in stope, thermal transfer between rock and air, distribution of temperature in stope were formulated. With CFD (Computational Fluid Dynamics, DFD) simulation and Fluent software, geometrical model of a stope was built, boundary conditions was initialized, then the temperature distribution, velocity and pressure field, concentration of oxygen and CO2 of air were simulated. In order to validate the simulation result, the parameters of the stope were measured with meter, and comparing with the data of simulation. The result shows that the data of measuring and simulating are compatible. According to the distribution of temperature and velocity, some ways such as flow angle and flow velocity are put forward, simulation and parameter optimization made also, a satisfied result is acquired. The conclusion can be used on ventilation designing and stope improving.

Analytical studies on thermal behaviour and geometry of weld pool in pulsed current gas metal arc welding

In view of the criticality of pulsed current gas metal arc welding (P-GMAW) due to simultaneous influence of the pulse parameters on thermal and metal transfer behaviour of the process an analytical model has been developed for predicting the temperature and geometry of the weld pool by appropriately considering two types of heat sources of different nature. The model considers the impact of heat in droplets of filler metal depositing in the weld pool in addition to initial arc heating. The model assumes the primary heat transfer to weld pool is the initial arc heating considered as continuous heat source (arc heat source) of double ellipsoidal nature followed by deposition of superheated filler metal considered as point heat source of interrupted nature superimposed on the first one. The dissimilar nature of the two heat sources is treated by different analytical techniques to estimate their temperature distribution in weld pool and HAZ at its vicinity. The geometry of the weld pool has been estimated by evaluation of the weld isotherms causing melting of the base metal under the influence of two heat sources acting on the weld pool. The impact of impinging droplets on weld pool has been considered to determine the depth at which the droplets transfer their heat in it. The predicted temperature and geometry of the weld pool as well as the temperature of HAZ are found well in agreement to the experimental values with a deviation of the order of ±10% in case of the weld deposition of Al–Mg alloy and commercial aluminium especially at high mean current of the order of 180 A and beyond the transition current of the filler wire. However, prediction of weld pool temperature and weld geometry is relatively different at comparatively lower mean current of 150 A below the transient current of the filler wires is not up to the mark.

Ni基単結晶超合金の表面溶融部の組織学的検討

Crystal growth behavior in the surface-melted region of Ni-base single crystal superalloy CMSX-4 was investigated. The surface melting was conducted using 2kW diode laser or gas tungsten arc. Laser power and scanning speed in laser surface melting were varied while defocusing distance and shielding gas (Ar) flow rate were fixed. For arc surface melting, arc current and welding speed were varied. Specimen surfaces were arranged parallel to the (001) of the base metal. The microstructure and crystal orientation in the melted region were analyzed by using optical microscopy, scanning electron microscopy(SEM) and electron backscattered pattern analysis(EBSP). The microstructure and crystal orientation in laser surface-melted region were markedly influenced by heat input. The laser surface-melted region under low heat input conditions was found to be solidified as the single-crystalline state with unidirectional dendrites which grew along the [001] directions. The laser surface-melted region under intermediate heat input conditions was also single-crystalline with dendrites which grew along the [001], [010] and [100] directions. In contrast, in the case of high heat input conditions, the laser surface-melted region was consisted of polycrystal with stray crystals. Such tendencies were also observed in the melted region with gas tungsten arc. These results demonstrate that heat input significantly affects single-crystallinity regardless of the type of heat source, such as laser and arc. Furthermore, stray crystal formation in surface-melted region was investigated in detail by using SEM and EBSP. From the results of these experiments, it is revealed that stray crystal formation was affected by constitutional supercooling and dendrite growth direction.

Laser-Assisted Bending

When sheets of high-strength (HS) and ultra-high-strength (UHS) steels are bent by a press brake the process suffers from large bending forces, considerable springback, and eventual cracks. Additionally, some unpredictable effects, such as lost contact to the punch, caused by strain hardening may occur producing a bend with erroneous radii. The strain hardening of the bending line may make further processes, such as forming or welding, more complex. One solution to these problems is to anneal the bending line with a laser in advance. Of course, it is also possible to utilise other types of heat sources, but the laser can offer the most precisely controlled heat treatment. The proper process parameters depend on the material, and it has been noticed that inadequate process parameters may harden the material instead of annealing. In this work some experiments on bending sheet metal samples of HS or UHS steel with previously laser-annealed bending lines have been carried out and the outcome analysed. The results show that the annealing produces better bending results compared to the conventional procedure. This includes lower springback, less hardening in the bending line and more precise geometry of the bend. It can be even suggested that proper annealing with strain hardening in bending will produce the original material structure. Obviously, more theoretical and experimental work is required to optimise the process parameters including the laser power and speed for each pair of material strength and thickness.

In‐depth composition study of zirconia‐coated steel sheet by XPS

AbstractZirconia was deposited by spray pyrolysis on large‐area aluminized steel sheets using two different types of heat sources: infrared radiation or white light. XPS in‐depth composition study has shown that the carbon concentration is 4 at.% when using white light but 15 at.% when using infrared radiation. This carbon is found as zirconium carbide, formed as a diluted phase in the zirconia coatings. In the case of using infrared radiation, reflectance spectroscopy revealed a partial degradation of the optical properties of the coatings due to an incomplete pyrolysis of the precursor. These findings are of direct interest for unglazed solar façade elements made of steel, in which the zirconia coating will act as a barrier layer against the degradation of the steel sheet during long‐term outdoor exposure. Copyright © 2006 John Wiley & Sons, Ltd.

Energy conservation in domestic rice cooking

Energy conservation in cooking rice is an important area for scientific investigation. Experiments were conducted to measure the energy consumption during normal and controlled cooking of both unsoaked and presoaked rice using two types of domestic cooking appliance, namely, an electric rice cooker and a pressure cooker. Cooking rice with controlled energy input, under pressure and with presoaking were the three approaches, which resulted in saving of energy. Electric rice cooker was found to be the most energy-efficient among the different combinations of cooking appliance and the types of heat source used in the study. The energy consumption was much less (23–57%) compared to other methods. Prior soaking of rice generally reduced energy consumption as well as cooking time, more prominently during normal cooking. Controlled cooking offered more savings in energy compared to presoaking rice. Considering the energy consumption and cooking time, controlled cooking of presoaked rice was found to be the best among the several approaches investigated. Measurement of water evaporation loss appears to be a good indirect method of assessing the efficiency of heat utilization. Controlled energy input is another useful method that optimizes the energy utilization for cooking, besides presoaking and pressure cooking. Controlled cooking is desirable in all types of rice cooking.

Evaluation of energy efficiency in biofuel drying by means of energy and exergy analyses

The calculation of heat consumption is based on the First Law and it gives quantitative information about the energy used in drying. However, it does not pay any attention to the quality of the energy used in drying. To take into account the quality of the energy, attention must be paid to the Second Law, too. Especially in those cases where the energy used in drying may be converted to mechanical work, it is important to consider the Second Law is. In this paper, the energy efficiency of biofuel drying in a pulp and paper mill is evaluated on the basis of energy and exergy analysis. The evaluation is based on the determination of the heat consumption and the irreversibility rate for energy and exergy analysis, respectively. The evaluation methods are applied to two different drying systems, single-stage-drying with partial recycle of spent air, and multi-stage-drying. Both drying systems are also provided with a heat recovery unit in which the inlet air is pre-heated using the outlet air of the dryer. There are two alternative heat sources available for the drying energy, steam at a pressure of 3 bar and water at a temperature of 80 °C. The results show that the heat consumption is only dependent to a small extent on the heat source type or the drying system. On the other hand, the irreversibility rate depends to a considerable on the heat source and the drying system.

Thermal Imaging Analysis of Stimulated Heat Diffusion in Sheet Metal for Non-Destructive Metrology and Testing

Recent developments in infrared camera technology, testing methods and data processing algorithms have brought significant progress for high resolution spatial and temporal analysis of thermal radiation. Together with industry standard automation technology and specific infrared image data processing it became possible to non destructively inspect laser welded seams and other types of joints using heat flux analysis subsequent to thermal stimulation. High thermal diffusion coefficients of the usually metallic samples under test make the availability of high-speed infrared cameras as a key hardware component indispensable. Since high-speed infrared cameras with frame rates of at least 500 Hz have become available for commercial applications, non-destructive testing systems with a new class of performance were designed, manufactured, and implemented at industrial sites. Heat flux analysis as a new and robust method of non-destructive testing has been implemented for various types of equipment, ranging from off-line tools for laboratory use to automated robot based systems enabling fast and operator-free in-line inspection. Depending on environment, implementation surroundings, and geometry of objects to be inspected, different types of pulsed or continuous operating heat sources (e.g. flash light, laser, … ) are selected. Due to its outstanding industrial relevance non-destructive testing of laser welded seams in automobile manufacturing is shown in detail in this paper.

Adaptive-Weighting Input-Estimation Approach to Nonlinear Inverse Heat-Conduction Problems

The inverse heat-conduction problem involves surface-heat-flux or heat-source estimation that requires only the temperatures measured at an insulated wall. This problem becomes nonlinear if the thermal properties are temperature-dependent. Innovative adaptive-weighting input-estimation inverse methodology for estimating a time-varying unknown heat source from a nonlinear thermal system is presented. This algorithm includes the extended Kalman filter (EKF) and the recursive least-square estimator. EKF recursively estimates the interior temperature of a body under a system involving noisy measurement and modeling errors. During the EKF estimation procedure, an important regression equation between the observable bias residual innovation and the thermal unknown is provided. Based on this regression model, a recursive least-square estimator weighted by the adaptive weighting factor is proposed to estimate these unknowns, defined as the input. The Kalman tuning parameter is used first to analyze the interactive relationship between measurement noise and modeling-error variance. The superior capabilities of the proposed algorithm are demonstrated through two simulated examples with different types of time-varying heat sources as the unknown inputs. Nomenclature