Concentration Of Heat Sources Research Articles

Thermal Elasto-Plastic Analysis of Large Steel Plate Cutting Using Layered Shell Elements

In this study, plasma cutting deformation of a large plate was simulated by applying a thermal elasto-plastic analysis technique using a layered shell elements. First, plasma cutting heat source model was proposed based on double Gaussian distribution model. And the proposed heat source model was compared with the experimental results through heat source parameter tuning. In addition, by applying the adaptive element division technique, we increase the heat flux input accuracy for the heat source concentration in a cutting area. And by applying the element de-activating technique, it was possible to simulate the melted part extinguished by cutting. Thermal elasto-platsic analysis of cutting of large plates was performed using the developed heat source model. To this end, layered shell element was used, and heat flux was applied to each layer of the layered shell element to improve the accuracy of analysis. The analysis result was compared with the experimental result to confirm the analysis accuracy. Through the analysis results, the occurrence of rotational deformation and bending deformation that affect the dimensional quality of large plates was verified, and its validity was reviewed by comparing them with the experimental measurement results.

HEAT SOURCE FOR TIG WELDING MODELLING

A new model of heat source applicable to TIG welding is proposed. The model uses three calibration parameters - efficiency, effective heating spot radius and heat source concentration factor. Based on the experimental results, the model was calibrated and the results obtained for the form of penetration were compared with the experimental ones.

Heat Source Characteristics of Ternary-Gas-Shielded Tandem Narrow-Gap GMAW.

The characteristics of the welding heat source for tandem narrow-gap gas metal arc welding are examined for different ternary shielding gas (Ar-CO2-He) compositions. Results of previous calculations of arc properties for bead-on-plate geometry are adapted to the narrow-gap geometry to predict these characteristics. The heat source concentration factor decreases and the maximum heat flux density increases as the helium content increases, which leads to an increased welding heat efficiency. Addition of CO2 up to around 10% also increases the heat efficiency. When the CO2 content exceeds 10%, the heat source concentration factor increases significantly and the heat efficiency decreases. The shielding gas composition also affects the heat source distribution. The heat source characteristics are applied to a computational fluid dynamic model of the weld pool to predict the weld shape, and the predictions are verified by experiment. The results indicate that the appropriate addition of helium to the shielding gas can increase the heat transferred to the peripheral regions of the arc and increase the sidewall penetration.

Study on the Resistive Heat Source in a Two-Phase Medium at High-Frequency Electrosurgical Intervention

Numerical analysis of distribution of resistive heat source in two-phase conducting medium (copper electrode – biological tissue) was carried out. Axisymmetric two-dimensional elliptic problem, with boundary conditions of the first and second kind was solved in the environment of MATLAB mathematical package, using the method of finite differences. Analysis results show that heat source concentration and other parameters are determined by skin effect. This fact should be taken into account in development of new effective methods of surgical treatment and respective instruments. This mathematical model can be applied in a wide frequency range for conducting materials with different conductivities.

Heat source reconstruction from noisy temperature fields using a gradient anisotropic diffusion filter

This paper presents a post-processing technique for noisy temperature maps based on a gradient anisotropic diffusion (GAD) filter in the context of heat source reconstruction. The aim is to reconstruct heat source maps from temperature maps measured using infrared (IR) thermography. Synthetic temperature fields corrupted by added noise are first considered. The GAD filter, which relies on a diffusion process, is optimized to retrieve as well as possible a heat source concentration in a two-dimensional plate. The influence of the dimensions and the intensity of the heat source concentration are discussed. The results obtained are also compared with two other types of filters: averaging filter and Gaussian derivative filter. The second part of this study presents an application for experimental temperature maps measured with an IR camera. The results demonstrate the relevancy of the GAD filter in extracting heat sources from noisy temperature fields.

Analysis of trends in the development of cities’ heat supply systems

New challenges—including the modern urban development policy, formation of the market of energy efficient technologies and different types of equipment of a broad power capacity range, tightening requirements to reliability, quality, and economic accessibility of heat supply—enhance the competitiveness of decentralized heat supply. In addition, its spontaneous growth and not always reasonable implementation lead to unjustified expenses, low efficiency, and ecological inconsistency. This proves the relevance of solving the problems of dividing an urban territory into zones of centralized heating (CH) and decentralized heating (DCH) along with their planning and justification, as well as determining a reasonable level of heat supply centralization and concentration of heat sources' power capacity. Solving these problems using the suggested method will allow optimizing the application areas for various types of heat supply and heat sources, justifying the degree of heat power capacity concentration and the extent of the systems as early as at the phase of a detailed urban planning project and then refining them during the design of urban heat supply systems. This will dramatically improve the reasonability of the decisions made and will simplify the procedure of their implementation. For criteria of limiting the extent (radius) of heat supply systems and defining their type, we suggest using standard values—the density of heat load per unit length of the pipeline and per unit area of urban territory. Standard values must be differentiated across the territory of Russia taking into account regional climatic and economic conditions and unique characteristics of heat supply development in cities and towns. The present article continues and develops the statements made in the previous articles created within the framework of the Theory of Hydraulic Circuits and takes into account the current situation and emerging trends in heat supply.

Power generation characteristics of a sandwich-type self-heating thermoelectric generator with spatially varying embedded heat source

Summary Power generation characteristics of a sandwich-type thermoelectric generator in which the heat source is embedded into thermoelectric elements are investigated. Our previous work on a similar concept only considered a uniform heat source distribution inside thermoelectric elements. In this work, the effect of the spatial distribution of a heat source is examined. In particular, the effect of the concentration of heat source near the one end, that is, the hot end, is intensively studied as a potential means of improving the efficiency of the device. Although the effects of heat source concentration in impractical cases without heat transfer limitations on the cold side remain ambiguous, it become clear that heat source concentration indeed has positive effects in more realistic cases with finite heat transfer coefficients imposed on the cold side. Because of the relatively low efficiency of typical thermoelectric generation, a significant amount of heat must be dissipated from the cold end of the thermoelectric element. Greater heat source concentration near the hot end leads to more effective utilization of available heat source, reduces the amount of heat rejected at the cold end, and lowers the hot end temperature of the thermoelectric element. Overall, it is suggested that heat source concentration can be used as a method to achieve more efficient operation and better structural integrity of the system. Copyright © 2015 John Wiley & Sons, Ltd.

Asymmetric thermal evolution of the Moon

The Moon possesses a clear dichotomy in geological processes between the nearside and farside hemispheres. The most pronounced expressions of this dichotomy are the strong concentration of radioactive heat sources on the nearside in a region known as the Procellarum KREEP Terrane (PKT) and the mare basaltic lava flows that erupted in or adjacent to this terrane. We model the thermochemical evolution of the Moon using a 3‐D spherical thermochemical convection code in order to assess the consequences of a layer enriched in heat sources below the PKT on the Moon's global evolution. We find that in addition to localizing most of the melt production on the nearside, such an enriched concentration of heat sources in the PKT crust has an influence down to the core‐mantle boundary and leaves a present‐day temperature anomaly within the nearside mantle. Moderate gravitational and topographic anomalies that are predicted in the PKT, but not observed, may be masked either by crustal thinning or gravitational anomalies from dense material in the underlying mantle. Our models also predict crystallization of an inner core for sulfur concentrations less than 6 wt %.

Heat production in the continental crust, part I: data converted from seismic velocities and their attempted interpretation

When using the simple exponential distribution of radiogenic heat production ( A) with depth ( z), A( z) = A o exp(− z/ D), the statistical analysis of a large number of heat production profiles, converted from the observed seismic velocity vs. depth profiles and the experimental knowledge of the relationship between seismic velocity and heat production, disclosed certain relations between the logarithmic decrement ( D-value) and heat flow, tectonic age and crustal thickness. The D-valuein this respect characterizes the depth rate of the differentiation of the heat production. In all tectonic units the D-parameter decreases with depth. As the next step, the more complicated distribution law A( z) = A o exp(− z/ D)− a was applied, where a characterizes the quantity of removed heat sources by the processes accompanying the crustal evolution (such as remelting, metamorphosis, leaching by underground waters, etc.). All parameters A o , a and D are constant within each particular tectonic province and parameter D does not depend on depth, contrary to the former law. The amount of removed heat sources a reflects the initial concentration of heat sources, and is higher in young tectonic terranes, in areas of high heat flow and in regions of thin crust.

Remelting mechanisms for shallow source regions of mare basalts

Two mechanisms are studied which could induce remelting at shallow depths within the Moon: a radioactive heating model in which remelting is the result of lateral variations of the heat source concentration emplaced by the end of the initial differentiation event, and a thermal insulation model in which remelting is induced by lateral variations of near-surface conductivity as a result of a high-porosity ejecta blanket created by basin-forming impacts. The effects of these perturbations are studied by evaluating the thermal evolution of an otherwise radially symmetric lunar model. The radioactive heating models predict extensive pre-basin volcanism, which would probably remove from the source region many of the heat-producing elements potentially responsible for melting. Therefore, localized high concentrations of heat-producing elements emplaced early would most probably not be heat sources for the basin-filling mare basalts; however, they are plausible heat sources for pre-basin mare basalts. The thermal insulation model predicts a delay of about 200 m.y. between impact and volcanism. Thermal insulation may also allow for the persistence of source regions for young basalts at shallow depths. If greater basin ages are correct, from 4.2 to 3.9 Ga, and most volcanism occurred between 3.8 and 3.6 Ga, then the thermal insulation model may explain the delay between impact and basin filling. If the basins formed during a terminal cataclysmic event at about 3.9 Ga, then the earliest stages of basin filling at about 3.8 Ga may have been a result of melting beneath the basin as a result of mantle uplift. Basin filling may have been characterized by a migration of the source region from beneath the basin to beneath the adjacent highlands. Cooling of the top 200 km beneath the basin after 200 m.y. because of its high surface conductivity is consistent with the mascon support requirement.

Origin, evolution and present thermal state of the Moon

The relative absence of lunar volcanism in the last 3 × 10 9 y and the Apollo 15 heat flow measurement suggest that present-day temperatures in the Moon are approximately steady-state to depths of ≈ 100 km. An exponential distribution of heat sources with depth may then be scaled by equating the surface heat flow to the integrated heat production of this exterior shell. Presumed present-day interior temperatures, as well as the present-day surface heat flow of ≈ erg/cm 2 · s, may be obtained with an intial temperature roughly corresponding to the Apollo 11 basalt solidus, the exponential scaling of heat sources, and a parameter Q/ U 0 K = 1.6 × 10 −4 K/ppm( U 0) · cm ( U 0) is the surface concentration of U in ppm, K is the average thermal conductivity in erg/cm · K · s and Q is the present-day surface heat flow in erg/cm 2 · s); the nonuniqueness is constrained by the observations of U 0 and Q and inferences concerning K. The “best” models require strong concentration of heat sources in the upper 100–200 km, within the √( kτ) depth of ≈ 300 km for which the buried heat sources may be felt at the Moon's surface. The concentrations of U for an originally homogeneous Moon are estimated to be ≈ 9 × 10 −8 g/g, close to that measured for eucrites and infrared for primative inclusions of the Allende meteorite. The estimated surface material and inferences to modest depth, and the short accretion time of the Moon necessary to provide large-scale differentiation at 4.6 AE suggest that the Moon had its origin in the rapid accretion of compounds first condensing from the protoplanetary nebula. Accretion of the Earth and Moon may well have kept pace with condensation in the originally hot nebula. In the later stages of accretion-condensation, the Moon competed unsuccessfully with the more favorably disposed Earth. The present thermal state of the Moon may well involve at least some partial melting through all of the lunar interior deeper than 200 km. This would eliminate the large density changes which would otherwise occur for CaAl rich compositions at depth. Such a present-day thermal configuration in neither inconsistent with temperatures inferred from electrical conductivity studies now with the nonhydrostatic shape of Moon. In the first place, the lunar interiors is probably more deficient in total. Fe than had previously been suspected, and in the second place the Moon is closer to being in hydrostatic equilibrium than is the aseismicity of the Moon need only reflect the absence of plate motions, as they are known on the Earth, rather than a “cold” interior. For otherwise “hot” interiors, plate motions seem less likely on the Moon than on Earth for simple geometrical reasons.

Surface heat flow from a differentiated Earth

Numerical calculations have been carried out on the development of surface heat flow in model earths. The bulk radioactivity of the earth is taken equal to that of chondritic meteorites. The initial temperature reaches 2600° at 1200 km. The heat flow for a model in which the radioactivity is uniformly distributed in the outer 600 km is 90 ergs/cm2/sec. If the radioactivity is concentrated in the outer 100 km, the present-day surface heat flow is 68 ergs/cm2/sec. The initial heat contributes about one-fifth the surface heat flow. The examination of the relations between initial heat, radioactive distribution, and heat flow suggests that if the earth has the radioactive composition of chondritic meteorites, then a near-surface concentration of heat sources must have proceeded at temperatures well below the melting point of silicates. Radioactivity lower by a factor of 2 would remove the indicated discrepancies.