Heat Flow Density Distribution Research Articles

Study on flow and heat transfer characteristics of 3D molten aluminum droplet printing process

The molten metal droplet printing technology can effectively realize a precise preparation of complex electronic devices at the micro scale by relying on the metallurgical bonding among the tiny molten metal droplets, which can improve the metallographic structure and mechanical properties of the fabricated parts. In this paper, the interaction process between metal droplets and movable substrates during the preparation of electronic devices is studied based on the coupled level set volume of fluid method (CLSVOF) and equivalent heat capacity method. The influence of the micro-bubbles and wall infiltration characteristics on the impingement spreading flow of metal droplets and their heat transfer cooling process is also investigated. The evolution mechanisms of droplet geometry and the distribution characteristics of droplet internal temperature and heat flow density during the impingement spreading process are discussed. The mechanism of high-temperature region formation under superhydrophobic wall conditions is analyzed. Results show that the microbubbles inhibit the spread of molten metal droplet. Under the same conditions, the spreading radius of hollow metal droplet is smaller than that of solid droplet, and their spreading height is higher than that of solid droplet. Different wall infiltration characteristics have similar degrees of influence on the spread of solid and hollow droplets. A larger wall contact angle for the same impingement mode at the same moment corresponds to a smaller droplet spreading radius and the higher the spreading height. With the participation of microbubbles, the heat transfer cooling process inside metal droplet becomes slow and demonstrates a less uniform temperature and heat flow density distribution. A high-temperature region is easily formed inside droplet under superlyophobic wall conditions, which triggers an uneven heat transfer cooling process at the bottom of the droplet. The results benefit to reveal the law of metal microdroplet impingement molding on different working surfaces and provide a theoretical reference for the preparation of electronics-related devices.

Metallographic method for temperature measurement: Reconstruction of grinding temperature field based on critical austenitizing depth and cyclic feedback algorithm

Effectively measuring and predicting the grinding temperature is significant for accurately controlling machined surface quality. However, the spatial limitations of the contact area and the time-varying of heat sources make the accurate acquisition of grinding temperature challenging. Existing methods have made critical achievements, but further exploration is still desired. To this end, a metallographic method for temperature measurement is proposed, which uses the thermal reference reflected by metallographic images combined with a cyclic feedback algorithm to reconstruct the grinding temperature field. Specifically, dry grinding thermal-force synchronous measurement experiments are carried out for carbon steel, and the mapping relationship between the grinding heat transient characteristics and metallurgical transformations diversity in the surface material is established. The improved image recognition algorithm is applied with metallographic detection to achieve accurate localization of the critical austenitizing depth. Afterwards, a cyclic feedback algorithm based on differential heat transfer is proposed to solve the dynamic distribution of the grinding temperature field (error within 10%) under random heat sources. The results show that the parabolic heat source can better describe the distribution of heat flow density in the contact area under dry grinding, and the heat flow into the workpiece is about 30% of the total energy. This study fills the blank of the metallographic method for solving grinding temperature, which helps profoundly understand the interaction mechanism between processing heat and metallurgical transformation and promotes the development of advanced temperature measurement and prediction technology.

Mapping of Western Siberian heat flow (southeast)

This paper maps the heat flow density from the pre-Jurassic basement within a large territory of oil accumulation (circa 120 thousand sq. km) in the South-East of Western Siberia. Values of heat flow, calculated for 201 deep wells, comprise a dataset for developing the map with contour lines for every 2 mW/m2. These values were calculated by solving the inverse problem of Geothermy — one-dimensional initial-boundary value problem for equation of thermal conductivity in a solid with the moving upper boundary. The accepted mathematical statement is sufficiently accurate for modeling near horizontal bedded sedimentary section: existence of heat flow convectional component is taken into account via calculation of an effective heat flow value. The map shows different types of anomalous features of heat flow density distribution. Previously it was stated for Western Siberian Plate that values of deep heat flow within positive tectonic structures of sedimentary cover are 5—20 % higher than within negative tectonic structures. As it is, combined analysis of deep heat flow density distribution and location of tectonic structures (Kaimysov arch, Parabelmegaarch, especially Alexandrov arch and Pudino mega swell) shows tendency among positive tectonic structures for increasing deep heat flow value. However, it is not always so. For example, there is the utterly different correlation for the Srednevasyugan mega swell. This structure is characterized with lower heat flow. The location of the Nizhnevartovsk arch is almost untraceable in the deep heat flow density distribution. Concerning oil-and-gas potential ... (?) A large positive anomaly has formed in the zone around the Traigorodsko-Kondakov field in the north. Two positive anomalies are in the central part of the map: around the Snezhnoe field and close by the Lomovoe, the Ozernoe and the Katylgin fields. Such fields as the Rybalnoe, the Pindzhin and the Mirnoe surround a positive anomaly in the southeastern part of the map.
 This paper contains a catalogue of discrete values (by wells) and a map of heat flow, which may be used as a «framework» in basin modeling. Upcoming research concerning origin of heat flow density anomalies — graded assessment of possible influence of tectonics, material composition and oil-and-gas potential of basement rocks has theoretical and practical significance.

Numerical analysis of meshing heating of involute spur gear

Involute spur gears generate heat due to tooth surface meshing friction. Excessive temperature rising affects transmission accuracy and reduces work reliability.. By establishing the normalized coordinates of the meshing curve and based on the frictional heat generation theory, the mathematical analysis model of the meshing surface heating is studied, the factors affecting the average heat flux density of meshing are explored, and the distribution law of these factors along the normalized coordinate of the meshing is analysed. The analysis shows that the tangential velocity of the meshing point and the half-bandwidth of the time domain contact have the greatest influence on the average heat flow density; the average heat flow density distribution of the driving wheel and the driven wheel are similar. The heat flow density of the driving wheel is greater than that of the driven wheel. Tooth shape modification minimizes tooth surface meshing contact stress, reduces meshing heat generation, controls temperature rise and improves transmission reliability.

Geothermy and zoning of shale oil prospects of the Koltogor-Urengoy paleorift (southeastern part of West Siberia)

Zoning of shale oil content at the southern segment of the Koltogor-Urengoy paleorift were done and it were correlated with geothermal field in the after Jurassic time. Territory of research is the north-western oil fields of the Tomsk region. The thermal history of the source rocks is criteria for predicting centers of oil generation and the formation of shale reservoir. It is cumulatively taking into account the temperatures of localized paleocenteres of oil generation. Researches are based on solving a direct problem of geothermy for a set of horizontal layers located in the lower half-space. Distribution of the oil generation density has been obtained and zones for searching for shale Bazhenov oil have been identified — it is the northwestern slope of the Northern-Parabel’ megamonocline; the northeastern slope of the Kaimysov arch; the Cheremshanskaya mesosaddle and the Traygorod mezoswell. The prediction is confirmed by direct signs of the oil content of the Bazhenov suite. Distribution of the oil generation density of the Bazhenov oil in different structural-tectonic conditions has shown that the intensity of hydrocarbons generation on positive structures is similar to the generation density in depression. “Traces” of anomalous heat flow are not in the rift zone there during the Cenozoic period. Zone does not correlate with the paleotemperatures distribution in the after Jurassic time. There is the reflection of the paleorift; as an object with anomalous structural characteristic; in the distribution of generation density at the Upper Jurassic shale oil. The energy relationship of the paleorift with the distribution of heat flow density and paleotemperatures of the source rocks has not been identified. Zoning of the shale oil determined promising territories for setting up geological survey. The results are worth of attention in the context of the theoretical foundations of oil and gas geology of Western Siberia; the theory of rift systems and the oil and gas potential of the West Siberian plate.

Thermal modeling and heat flow density interpretation of the onshore Northwest Java Basin, Indonesia

Studies pertaining to heat flow density distribution in Indonesian tertiary sedimentary basins have been conducted intermittently throughout more than two decades. Even so, all of these studies have always concentrated on the basic compilations of thermal gradient, thermal conductivity, and terrestrial heat flow datasets or the study of basin thermal history rather than on the investigations into their present thermal regime. In addition, syntheses on the possible causes to the observed heat flow density distribution in these basins have been largely determined only on the basis of its correlation with geological and geophysical evidences. One basin experiencing this particular problem is the onshore Northwest Java Basin, where knowledge of the present-day subsurface temperature structure is virtually absent and interpretation of heat flow distribution has been mainly qualitative. For these reasons, in this study we have attempted to quantitatively characterize the present subsurface temperature distribution and surface heat flow density of the onshore Northwest Java Basin using a simple numerical thermal modeling approach, based on the most recent heat flow datasets. Taking into account a conductive heat transfer process, the modeling exercise is aimed at deriving a 3-D subsurface temperature distribution. The temperature distribution is translated into the predicted surface heat flow distribution. The modeled temperature field reveals its dependence on the geometrical aspects of the basin’s basement. Comparison between the computed and the observed heat flow densities, taking into account the uncertainties of both, suggests that advective heat transport by groundwater flow may be present, in addition to conduction. The modeling results are thus capable of demonstrating the importance of a quantitative approach in studying the present thermal state of a sedimentary basin.

Thermal conditions for geothermal energy exploitation in the Transcarpathian depression and surrounding units

Abstract The contribution presents the results acquired both by direct cognitive geothermic methods and by modelling approaches of the lithosphere thermal state in the region of the Transcarpathian depression and surrounding units. The activities were aimed at the determination of the temperature field distribution and heat flow density distribution in the upper parts of the Earth’s crust within the studied area. Primary new terrestrial heat flow density map was constructed from values determined for boreholes, from their interpretations and from newest outcomes of geothermal modelling methods based on steady-state and transient approaches, and also from other recently gained geophysical and geological knowledge. Thereafter we constructed the maps of temperature field distribution for selected depth levels of up to 5000 m below the surface. For the construction we have used measured borehole temperature data, the interpolation and extrapolation methods, and the modelling results of the refraction effects and of the influences of source type anomalies. New maps and other geothermic data served for the determination of depths with rock temperatures suitable for energy utilization namely production of electric energy minimally by the binary cycles. Consequently the thermal conditions were used to identify the most perspective areas for geothermal energy exploitation in the region under study.

Regional and local phenomena influencing the thermal state in the Flysch belt of the northeastern part of Slovakia

Abstract The locality of the northeastern most part of Slovakian Flysch belt belongs to interesting areas in terms of the interpretation of geothermal conditions in mutual relation with the lithosphere structure and their tectonic development. The evaluation of the geothermal energy sources parameters of this locality is likewise worthwhile. The region under study has the centre in position of the borehole Zboj ZB-1 and spreads out Slovakia also in Poland and Ukraine. Our contribution provides the analyses of existing geothermal data enhanced by the construction of temperature field models corresponding to the global and local aspects that influence the temperature and heat flow density distributions. The analyses are related to the structures and effects of separate phenomena along as well as across the Carpathian arc. The model calculations were carried out both by analytical and numerical methods of solving the heat transfer equations including their steady state forms and transient cases too. Besides the regional trend of thermal activity decrease in direction from East-Slovakian Basin to the outer Carpathian units the combined local influences are applied: subsurface thermophysical parameters of rock complexes distributions, non-stationary sources from supposed subvolcanic bodies in close surroundings of borehole Zboj ZB-1, and the effects of the hydrological factors. Considering the observed higher thermal activity in arched zone along the Carpathian structures we discussed the thermal effects of rock complexes supposed as a source of regional Carpathian Conductivity Anomaly and the transfer of heat from East-Slovakian Basin to Outer Carpathian Flysch units. The analysis and the modelling results suggest that the mentioned activity is caused by the influences of source type phenomena mainly related to deep fault systems at the margin of the European Platform. That means the anomalies in heat flow density distribution can reach the value 70 mW/m2 and more in the zone above the thermally active deep-fault system with the presence of volcanism and hydrothermal activities.

Numerical Study on Heat-Flow Density of Aerospace Plane

Relying on the status of existing thermal protection system and existing flight parameters, appropriate metal thermal protection system being able to reproduced are designed. Then, based on the highest temperature thermal protection materials can bear, flying height of aerospace plane and Mach number, the numerical method was utilized to reveal the heat-flow density of stagnation point on the sharp- nose and the distribution of heat-flow density.

Numerical Study on Structure Thermal Protection of Aerospace Plane

The letter relying on the status of existing thermal protection system and existing flight parameters, appropriate metal thermal protection system being able to reproduced are designed; according to the distribution of heat-flow density we make certain the structure and thickness of the heat shield, structure of cooling bed and pressure of cooling air, velocity of flow and so on. The distributions of temperature of points on the nose and the inside of skin are calculated.

The flow and heat transfer characteristics of double droplets impacting on flat liquid film

A coupled level set and volume of fluid (CLS-VOF) method is applied to simulate the process of double droplets which continuously impact on a hot liquid film on a wall of constant temperature, and the evolution processes after the double droplets impinge on the hot flat liquid film are studied. Influences of vertical spacing between the two droplets, impact velocity, film thickness and droplet diameter on the flow and heat transfer characteristics are discussed. It is found that the average heat flux density of the wall increases with the rise of impact velocity. The influences of vertical spacing between the two droplets, droplet diameter, and liquid film thickness on the average heat flux density are small, but they have an important effect on the distribution of heat flow density in the impact area and the border area.

Influence of Secondary Vortices of Thermogravitational Convection on the Liquid Metal Heat Exchange in a Horizontal Tube in a Magnetic Field

The results of the experimental study of heat transfer in the liquid-metal coolant flow in a horizontal heated tube are presented. We considered different variants of heating a tube with a heat flow density distribution that is homogeneous along the length and in the general case is inhomogeneous along the perimeter of the tube cross section. Measurements have been made of the three-dimensional fields of the averaged and oscillation temperatures and the coefficients of heat transfer along the tube length, as well as of the profiles of the longitudinal and transverse velocity components in the presence and in the absence of magnetic fields (MF). A strong influence of thermogravitational convection (TGC) on the temperature fields and the heat transfer coefficients has been revealed. TGC having the form of large-scale vortices swirled around the longitudinal axes leads to intensification of heat transfer in a horizontal tube. The wall temperature distribution in the tube cross section becomes inhomogeneous. A magnetic field can enhance the TGC effects.

Geothermal reconnaissance of the Marmara Sea region (NW Turkey): surface heat flow density in an area of active continental extension

Northwestern Anatolia is an area of significant neotectonic activity. The Northern Anatolian Fault splits into different branches and the tectonic regime changes from translation to a combination of extension and translation. High seismicity as well as frequent and in places large hot springs are related to these tectonic features. The present study aims at characterising the geothermal situation of this area by detailed heat flow density mapping and thermal spring studies. High-resolution temperature logs and measurements of rock thermal conductivity were used to determine the terrestrial heat flow density. Because of the shallowness of the available drillholes (maximum depth of 200 m), hydraulic influences on the thermal profiles had to be taken into account. Conductive heat flow density was calculated considering possible convective effects due to vertical water movements. In spite of these hydraulic influences, the temperature distribution showed stability over a time period of at least one year. Stationary models could therefore be applied. Terrestrial surface heat flow density varies regionally from 35 to 115 mW/m 2, with a mean value of 60 mW/m 2. The heat flow density map shows that the extensional tectonics of the region south of the Marmara Sea is characterised by higher heat flow density values. Regions with low tectonic activity such as parts of European Turkey or regions with compressional and translational tectonics have average or slightly lower values. The spatial pattern of thermal springs in the Marmara Sea region does not coincide with the terrestrial heat flow density distribution. Their appearance is bound to neotectonic faults (= locally enhanced vertical permeabilities).

A simple heat-flow quality function and appraisal of heat-flow measurements and heat-flow estimates from the UK Geothermal Catalogue

A comprehensive database of temperature, heat flow, thermal conductivity and geochemistry is the basis of geothermal modelling. The latest revision (1987) of the UK Geothermal Catalogue (UKGC) contains over 2600 temperatures at over 1150 sites and over 200 observations of heat flow. About 93% of the temperature data are from depths less than 2000 m and about 50% are Bottom Hole Temperatures (BHT). Heat-flow density distribution models can be expanded to include estimates of heat flow derived from BHT and thermal conductivity data contained in the UKGC. A simple quantitative assessment of the quality of individual heat-flow measurements has been devised, based on the type and frequency of temperature and conductivity measurements and the borehole depth. The dimensionless quality function (hfQ) has been defined so that for a heat-flow borehole with two equilibrium temperature measurements made across an interval with a mean depth of 1 km or greater, with complementary thermal conductivity determinations made at intervals of 1 m across this zone, the heat-flow quality function is 1.0. Over 50% of the UK heat-flow dataset has a hfQ function less than 0.10; the 4 highest quality observations have values above 1.0. The same function can be used to assess the quality of estimates of heat flow by assigning quality functions to various types of temperature and thermal conductivity observation schemes. Appraisal of the UK heat-flow dataset indicates that some of the observational data have a similar quality rating to estimates of heat flow derived from convolution of temperature and thermal conductivity data for deep boreholes within the catalogue. In eastern England, the heat-flow density pattern is significantly modified by incorporation of estimates of heat flow from deep boreholes which have hfQ values comparable with early heat-flow measurements made in this region.

Heatflow density distribution in the Red Sea

A new heatflow density (HFD) map of the Red Sea was compiled from 467 heatflow density values collected by various organisations during the last 20 years. The map shows that the complicated heatflow distribution can only be explained if we assume considerable convective transport of heat through water circulating in the sediments and crust, as well as convection in small volumes of mobilized magma associated with the deeps along the morphologic depression of the Red Sea. The HFD values are twice as high as the world mean at the flanks of the rift and reach values of 5 to 8 times the world mean in the graben and the deeps. One-dimensional stationary computations of the distribution of the isotherms showed that at 15 to 18 km depth the temperatures are sufficiently high to partially mobilize the upper mantle. Distribution of the HFD anomalies can only be explained if we assume that part of the rift development can be accounted for by the development of pull-apart basins that dominated the early stages of rifting and pure shear combined with wrench faulting active now.