Heat Flow Distribution Research Articles

Study on Testing Environment Simulation Method for Thermal Flux Density of Aerothermal

This paper presents the use of forced convection heat transfer approach to near-space thermal environment of hypersonic aerodynamic ground simulation test method for surface heat flux with a great gradient and temperature gradient of the tip wedge (rn=1.5mm) shape component level thermal test. In the test device test section, two different high subsonic speed airflow were nested within each of the two vents from the exhaust, the impact of the specimen heated to test sharp wedge surface heat flow and temperature distribution in line with a hypersonic flight state aerodynamic heat distribution patterns. Numerical results show that under this scenario, the specimen rear stagnation point heat flux and heat flux can be adjusted two ways to adjust the air flow; test methods within a certain accuracy-related parts for the superb aerodynamic vehicle thermal environment simulation.

Acoustothermal Effects with Nonlinear Resonance Oscillations of a Gas in an Open Tube

The results of theoretical and experimental studies of thermal secondary effects arising from nonlinear oscillations of gas in an open tube are presented. The heat flow distributions along the tube at the transition through resonance for different amplitudes of the piston displacement are obtained. It is established that the heat flow decreases from the piston to the open end. A good agreement between theoretical calculations and experimental data was obtained.

A simple temperature calculating method of flame tube inclined multi-hole wall

Inclined multi-hole full-coverage film cooling, as a practical cooling scheme, has received widespread application in combustion chambers. In the initial stage of combustion chamber design, the numerical simulation of three-dimensional structure is a long calculation period. A simple one-dimensional program can shorten the design cycle, which is used to preliminaries calculate heat transfer characteristics and flow distribution. A simple temperature calculating method of inclined multi-hole wall temperature in the high temperature combustor flame tube was developed. The flow and heat transfer characteristics in the combustor can be expected by this method. Heat transfer in the combustor flame tube is researched based on the plate flow field. The coupling effects of heat transfer, wall heat conduction and radiation heat transfer are considered, such as convective and Radiative heat transfer between primary flame flow and the hot wall side, convective heat transfer in the film holes, convection and radiative heat transfer between the cool wall side and the annular cooling air flow, radial heat conduction inside the wall. In the initial stage of combustion chamber with inclined multi-hole design, the design cycle can be shortened by this method, using relatively simple calculation to know the combustion chamber wall temperature.

Methodology for the Measurement of the Heat Partitioning by Thermal Imaging in the Orthogonal Cutting Process

The thermal conditions like temperature distribution and heat fluxes during metal cutting have a major influence on the machinability, the tool life time, and the metallurgical structure of the work piece material. Though numerous analytical and experimental efforts have been developed in order to understand the thermal conditions in metal cutting, many questions still prevail. So, the exact form, distribution, and intensity of heat sources in the primary and secondary shear zone, which may describe the observed temperature distributions, are not explored to a satisfactory extend. On the other hand, the influence of the material properties like friction coefficient, heat conductivity, and shear strength is not yet fully understood. Another essential question is the heat flux partition among chip, work piece, and tool depending on process parameters and material. The particular novelty of the current investigation is a new methodological approach using modern thermal measurement system and postprocessing methods in order not only to measure the entire temperature field in the orthogonal cutting zone but also to calculate the affiliated heat flow distribution in the cutting process. Thus, the cutting process is treated as energy conversation process of the governing mechanical power into sensible heat. This point of view offers compatibility across process parameters and materials, thus new possibilities for process design.

Measurement and Modeling of Heat Partitions and Temperature Fields in the Workpiece for Cutting Inconel 718, AISI 1045, Ti6Al4V, and AlMgSi0.5

Abstract The quantification of the heat flow distribution in the metal cutting process depending on the cut material and the process parameters is a research area with a long history. However, a quantification of the heat flow distribution between chip, tool, and workpiece is still a not fully solved problem and remains a necessary input value for the further modeling of temperature fields and subsequent tool wear and thermal induced surface alterations, which may impair the workpiece functionality. Thus, the following publication shows the results of orthogonal cutting in order to investigate the heat flow distribution between the chip and workpiece. Therefore, the heat partitions in the cutting process were calculated by a thermodynamic methodology. This methodology considers the temperature rise in the workpiece and the chip, measured by thermography and pyrometry, as the effect of the cutting work dissipated into sensible heat. Four metals, Inconel 718, AISI 1045, Ti6Al4V, and AlMgSi0.5, were cut at varying undeformed chip thicknesses and cutting velocities. By formulating a dimensionless number for the cutting process, the Péclet number, the thermal diffusivity was included as an evaluation criterion of heat partitioning between the chip and workpiece across material properties and process settings. In this way, the validity of the Péclet number as an evaluation criterion for heat partitions in cutting and as a valuable heuristic for process design was confirmed. Another goal was to extend the state of the art approach of empirical process analysis by orthogonal cuts with regard to specific cutting forces into the thermal domain in order to provide the basis for further temperature modeling in cutting processes. The usage of the empirical data basis was finally demonstrated for the analytical modeling of temperature fields in the workpiece during milling. Therefore, the specific heat inputs into the workpiece measured in the orthogonal cuts were transferred to the milling process kinematics in order to model the heat flow into the workpiece during milling. This heat flow was used as input for an existing analytical model in order to predict stationary temperature fields in the milling process for the two-dimensional case.

Improving efficiency of machining the geometrically complex shaped surfaces by milling with a fixed shift of the cutting edge

In order to improve efficiency of machining by milling geometrically complex shaped surfaces, mainly the methods related to improvement of properties of the tool material, change of composition and properties of the tool surface layer, application of thin film coatings, reduction of roughness of the working surfaces and improvement of operating conditions of the tool using lubricant-cooling media are mainly used. Proceeding from the above stated, scientifically grounded technical and technological solutions consisting in development of a new highly effective method for machining geometrically complex shaped surfaces by means of disk rotary cutters with a reciprocatively rocking feed motion were studied and set forth in this work. This machining method can increase the period of durability of tools by 1.7 times and milling performance by 1.6 times by means of a fixed kinematic shift of the cutting edge relative to the machined surface. A mathematical apparatus of the method of milling with a fixed shift of the cutting edge was proposed. Analysis of this method with the help of numerical functions has enabled establishment of analytical dependences for determining thickness and volume of a unit cut-off layer. Thickness of the cut-off layer is mainly affected by feed per tooth, Sz, and the angle υ influences its volume which determines normal cutting conditions. A model of distribution of heat flows in the cutting wedge for the method of milling with a reciprocatively rocking feed motion taking into consideration the amplitude of rocking motion of the workpiece was studied. A temperature decrease to 330.2...395.5 °C was established, that is by 80.6...181.6 °C for the stamp steel 9CRSI and to 193.8...285 °С, that is, by 56.6...120.2 °C for steel 45 compared to conventional milling. It was found that total length of the cutting edge increases 2.4 times with 1.5 times temperature decrease

HYDRODYNAMICS, DISTRIBUTION OF FLOWS AND THERMAL EFFICIENCY OF COIL HEAT EXCHANGERS IN UNITS OF HEAT-USING APPARATUS OF TUBE FURNACES

The theoretical foundations of construction, mathematical description and engineering calculation of heat exchangers of the serpentine type in blocks of heat-using equipment of tube furnaces and other types of reactors designed for carrying out endothermic reactions (in particular, reforming of natural gas with water vapor) are considered. It is shown that the thermal efficiency of heat exchangers of the coil type is significantly affected by the correct choice of parameters ensuring a uniform distribution of energy flows over the surface of heat-resistant heat exchange tubes. This technological problem is solved by compiling the heat balance and selecting the system of the corresponding equations, which allows to calculate the temperature contour of the coil heat exchanger, its hydrodynamic characteristics and the distribution of mass and heat flows through the heat exchange tubes. The use of the tensor form of the Boussinesq hypothesis is considered, with which the Reynolds equation describing a turbulent flow is transformed to a partial differential equation for a single unknown function and its averaged form is obtained. In relation to the problem under consideration, the correctness of the chosen approach was confirmed both theoretically and experimentally. It is shown that in the core of a turbulent flow with an intense suction or injection, the liquid behaves almost as ideal and the well-known Helmholtz – Friedmann theorem holds with the necessary accuracy. From the aforementioned averaged equation, expressions are obtained that are suitable for describing heat fluxes in channels with suction or injection. According to this theoretical model, thermal calculations of coil-type heat exchangers were carried out, a more accurate assessment of the temperature of the heated medium in each coil tube was made, and the temperature gradient of the external heat carrier over the cross section of the gas duct was found. For the first time in the practice of calculations when choosing the parameters of coils, a number of boundary conditions were taken into account, such as the condition of the coil layout, the necessary heat exchange surface, permissible restrictions on hydraulic resistance, etc.

3D-Basin Modeling of the Changling Depression, NE China: Exploring Petroleum Evolution in Deep Tight Sandstone Reservoirs

The Changling Depression is the largest and most resource-abundant reservoir in the South Songliao Basin, NE China. The petroleum evolution rules in the Lower Cretaceous deep tight sandstone reservoir are unclear. In this study, 3D basin modeling is performed to analyze the large-scale petroleum stereoscopic migration and accumulation history. The Changling Depression has a complex fault system and multiple tectonic movements. The model is calibrated by the present formation temperatures and observed maturity (vitrinite reflectance). We consider (1) three main erosion episodes during the burial history, one during the Early Cretaceous and two during the Late Cretaceous; (2) the regional heat flow distribution throughout geological history, which was calibrated by abundant measurement data; and (3) a tight sandstone porosity model, which is calibrated by experimental petrophysical parameters. The maturity levels of the Lower Cretaceous source rocks are reconstructed and showed good gas-generation potential. The highest maturity regions are in the southwestern sag and northern sag. The peak hydrocarbon generation period contributed little to the reservoir because of a lack of seal rocks. Homogenization temperature analysis of inclusions indicated two sets of critical moments of gas accumulation. The hydrocarbon filling in the Haerjin and Shuangtuozi structures occurred between 80 Ma and 66 Ma, while the Dalaoyefu and Fulongquan structures experienced long-term hydrocarbon accumulation from 100 Ma to 67 Ma. The homogenization temperatures of the fluid inclusions may indicate a certain stage of reservoir formation and, in combination with the hydrocarbon-accumulation simulation, can distinguish leakage and recharging events.

Temperature-depth curves and heat flow in central part of Anatolia, Turkey

The objective of this study is to determine the crustal thermal regime of Central Anatolia Province and its relationship with regional tectonics. Investigations include new temperature-depth measurements in wells, calculations of geothermal gradients from new and previously measured temperature logs, and determinations of heat flow with terrain corrections if necessary. The results provide us with a better understanding of the regional distribution of subsurface temperatures and heat flow within the study area. Although Central Anatolia Province is bordered with tectonically active areas, moderate heat flow values (64 ± 16 mW m−2) are generally observed within the region in accordance with the relatively less tectonic activity. Two thermally anomalous zones are indicated in the vicinity of Kırşehir and Kızılcahamam with heat flow values of higher than 100 mW m−2. Anomalous heat flow in these areas can best be explained by high radioactivity of basement rocks although this is not directly confirmed for the Kızılcahamam anomaly. The high elevation and recent volcanic activity in the region indicate that thermal activity may be present at lithospheric levels but have not yet reached up to crustal levels. Also, no surface heat flow anomaly due to fault activity was observed at the section of the North Anatolia fault within the study area.

PROBATION OF THE APPARATUS FOR LOW-TEMPERATE PROCESSING OF MEAT CULINARY PRODUCTS BY IR-RADIATION

The improvement of existent technological processes of making meat culinary products and development of the correspondent principally new resource-effective equipment is an urgent task. There was probated the developed apparatus of the low-temperature processing of meat culinary products by IR-radiation with the further qualitative assessment of ready culinary products for solving it. The results of the conducted studies provide making high-quality, juicy meat products without a crust that generally provides spreading the assortment of products under conditions of their low-temperature processing in a price category, attractive for a consumer. A flexible film resistive electric heater of the radiating type (FFREhRT) was used as a heating element for providing the even low-temperature processing of meat products at the expanse of taking the working geometry of a chamber of the apparatus by it. For providing the autonomy of the work of air-ejecting ventilators, there was offered to use Peltier elements that allow to transform secondary heat of FFREhRT in the low-voltage feeding tension and to provide cooling of the external surface of the apparatus synchronously. The apparatus is mobile that provides its displacement directly in places of realization. At the studies, there was established the culinary readiness degree of meat products of the spheric form with diameter 0,1±0,01m by reaching temperature 53…85 оС in the product center. The evenness of the heat flow distribution within the working chamber was proved by the data, obtained from thermocouples, placed on the metal spheric model of a meat product sample in real time by 7 thermocouples. As a result of analyzing the geometric model of placing Peltier elements, it has been established, that for providing the low-voltage tension of ventilators at level 3,55 V, 10 successively connected elements are necessary. The offered innovative construction-technological solutions allow to make high-quality, juicy meat products without a crust that generally provides spreading the assortment of products under conditions of their low-temperature processing.

Terrestrial heat flow of continental China: Updated dataset and tectonic implications

Terrestrial heat flow is a crucial parameter to indicate the thermal state within the Earth, containing integrated information of the ground temperature, thermal conductivity, and crustal/mantle heat flow. We present an updated heat flow dataset and map in continental China. The data increases from 862 to 1230 observations since the year 1999 and the sites cover the major tectonic units, although their spatial distribution remains uneven. Excluding the local anomalies related to hydrothermal activities, the background heat flow values display a range from 30 to 140 mW m–2 with a mean of 60.4 ± 12.3 mW m–2. The updated heat flow map exhibits a heat flow pattern consisted of four heat flow provinces in continental China: eastern mantle-induced high flow province, southwestern crust-induced high heat flow province, central normal heat flow province and northwestern low heat flow province. The major heat flow provinces correspond to the Cenozoic lithosphere-scale tectonic units. The heat flow shows good correlation with crustal thickness and elevation, agreeing with the thermal isostasy. The heat flow distribution also corresponds with the Meso-Cenozoic tectonic activities. The present heat flow-tectonic pattern in continental China is formed by the Meso-Cenozoic geodynamic processes, including the Cenozoic India-Eurasian collision and the Mesozoic-Cenozoic western subduction of the Pacific Plate.

Distribution of heat flow during electrical discharges diamond grinding

Distribution of heat flow during electrical discharges diamond grinding

INTRODUCING PASSIVE NUCLEAR SAFETY IN WATER-COOLED REACTORS - NUMERICAL SIMULATION AND VALIDATION OF NATURAL CONVECTION HEAT TRANSFER AND TRANSPORT IN PACKED BEDS OF HEATED MICROSPHERES

Current light water reactors (LWR) designs have been optimized over decades, and required improvements cannot be based on mere redesign but will require novel technologies. The introduction of an advance fuel in the form of coated micro-fuel particles under Helium atmosphere in the cladding tubes of light water reactor fuel assemblies is a novel technology proposed in this study. This will ensure retention of radioactive fission products by the fuel making LWR attain a passive safety status and among other advantages, higher fuel enrichment in the proposed nuclear fuel will provide higher burn-up. A slender geometrical model with tube-to-particle diameter ratio N = 2.503 and porosity ε = 0.546 mimicking the proposed nuclear fuel in the cladding was numerically simulated using hydrogen as the working fluid. A commercial code, Star CCM+ is used to investigate the heat transfer characteristics and flow distribution under buoyancy driven force expected in the cladding tube of the proposed nuclear fuel. Random packing of the particles is achieved by Discrete Element Method (DEM) simulation. The temperature contour and velocity vector profile obtained can be said to be good illustration of anticipated heat transfer and transport phenomenon to occur in the proposed design. Simulated results for particle-to-fluid heat transfer coefficient, Nusselt number, and Rayleigh number which are of prime importance when analyzing heat transfer performance in fixed bed reactors were validated. Simulated results show close agreement with results obtained in high temperature reactor HTR such as the PBMR.

Investigation of transient temperature fields in the milling cutter under CO2 cooling by means of an embedded thermocouple

The quantification of the heat flow distribution in the cutting zone is still a not solved problem in particular if cooling lubrication is involved. The publication introduces a model extended measuring approach in order to monitor heat and coolant flows in the milling process under CO2 – MQL cooling lubrication. The system featured a telemetry system in order to transmit the temperature measured by a tool-embedded thermocouple. By further data post processing of the temperature, the heat flow into the tool was inversely determined by comparison of the measured temperature a distinct point with analytically modeled, transient temperatures.

Effects of Mold Current on Slag Skin and Heat Flow Distribution During Electroslag Remelting at Given Power Input

A transient model including the electromagnetic field, fluid flow, and heat transfer has been developed based on the volume-of-fluid model and dynamic mesh technique. At given power input, two cases were simulated to investigate the effects of the mold current on the slag skin and heat flow distribution. The calculated melt rate and slag skin thickness were compared with measurements to validate the model. At given power input, with the mold current, the slag–metal pool interface shows a higher temperature, resulting in a thinner slag skin of 1.2 mm. Due to the more uniform slag temperature, the heat flow to the slag/mold interface reaches 34.7%, resulting in a low melt rate of 75 kg/h. In a laboratory-scale electroslag remelting unit, the heat transferred to the metal pool by convection approached 28% of the power input, independent of whether the mold current is considered or not.

A DEM-based heat transfer model for the evaluation of effective thermal conductivity of packed beds filled with stagnant fluid: Thermal contact theory and numerical simulation

The Effective thermal conductivity (keff) is one of the key thermal properties for packed beds in the presence of a stagnant fluid. In this study, a thermal discrete element model (DEM) based on the original Cheng-Yu-Zulli analytical model for mono-sized packed beds has been improved and implemented especially for mixed beds of different particle sizes or materials. In order to perform the DEM simulation for packed beds, a thermal contact theory considering three heat transfer mechanisms (solid contact conduction, solid-fluid-solid conduction and radiation) was derived and applied in the network of Voronoi cells obtained by radical Voronoi tessellation of the relevant beds. The numerical model was validated through a comparison with experimental results already reported in literature and a good prediction for the effective thermal conductivity was obtained for both mono-sized and multi-sized packed beds in a wide range of solid-to-fluid conductivity ratio. The model also showed a good performance to study the heat flow distribution as well as the coupled thermo-mechanical behavior of packed beds.

Key parameters of the structure and evolution of the Okinawa Trough: Modelling results constrained by heat flow observations

Heat flow data (664 measurements) in the Okinawa Trough and adjacent areas are edited and analysed in this study. The distribution of heat flow in the study area is obviously correlated with tectonic zones. The heat flow is extremely high and variable in the back‐arc basin and extremely low in the trench. A 2D transient heat conduction‐advection model is used to test and determine the thermal structure and evolution of the Okinawa Trough under the heat flow distribution constraint. The results show that (a) high sedimentation rates can reduce heat flow by 30–35%; lower heat flow in the southern than in the central‐northern Okinawa Trough might be caused by the thick sediment covering due to the Taiwan orogenic uplift. (b) Heat flow can be enhanced dramatically by mantle upwelling, but magma intrusion accompanied by ascending fluid is necessary for the extremely high heat flow along the central Okinawa Trough axis. A magma intrusion age of 0.5 Ma, an intrusion depth of 1 km, and a fluid flow speed in the magma of 9 cm/year are the best fit parameters for the central Okinawa Trough. (c) Given the distribution of heat flow, we suggest that the evolutionary model differs between the central‐northern and the southern Okinawa Trough. The rifting in the central‐northern Okinawa Trough began at 10 Ma with a mean rate of 0.4 cm/a, while the rifting in the south Okinawa Trough started at 6 Ma with a higher rate of 0.6 cm/a. (d) A double magma chamber may exist underneath the axis of the Okinawa Trough at depths of 10 and 24–30 km beneath the seafloor. The temperatures and pressures at these depths support the existence of partial melting, which became the primary basis for maintaining the extremely high heat flow currently observed in the Okinawa Trough.

Heat and mass transfer in confined jet plasma reactor with peripheral vortex flow

A fundamentally new solution for the creation of a peripheral vortex flow is proposed: by the means of rotation of a rotor placed in a reactor. Experimental studies have been performed based on which the distributions of the heat fluxes to the wall of the plasma reactor were obtained by creating a vortex flow by a rotating rotor. It is established that the presence of a vortex flow leads to a significant change in the distribution of heat and mass flow to the reactor wall. The presence of a vortex flow leads to a change in the distribution of the isotherms in the mixing zone of the high-temperature paraxial flow with the gaseous medium of the reactor.

The Development of a Method for Calculating the Nodal Prices of the Thermal Energy by Modeling the Thermal and Hydraulic Regimes of the Heat Supply Systems for Solving Control and Optimization Problems

The article deals with the issues of energy saving and increasing the efficiency of thermal energy. Energy saving issues are inextricably linked to the cost of heat for consumers. The costs of thermal energy transfer depend directly on thermal and hydraulic regimes of the heat supply system. A mathematical model and a method for calculating differential heat energy prices for all nodes and consumers of a heat supply system are discussed considering various heat production costs, the actual heat flow distribution, the location of the consumers in the network (the distance from the source), the structure and parameters of the network, and numerous internal and external disturbances of both a systematic and an accidental character. The above factors are taken into account by means of a thermo-hydraulic model for calculating the regimes of the heat supply system with intermediate temporal control nodes that serve as a basis for determination of the heat amount in every node at every time point. The proposed approach to the calculation of nodal prices can be interpreted as a method for solving the problem of distribution of the “price field” over the network for a given distribution of heat flows. The approach is based on three main principles, viz., the nodal balance of the heat cost, the equality of prices for the flows from the common node, and a differentiated increment of prices due to the variable component for the transfer of thermal energy for each of the sections of the calculation scheme. The proposed method for calculating the nodal prices of thermal energy can be used for multicriteria optimization of thermal and hydraulic regimes. The maximum utilization of the cheapest energy in the system or the minimum price of thermal energy for consumers can be the optimization criteria. The proposed approach makes it possible to differentiate prices within the regulatory period currently adopted in accordance with the process conditions of the heat supply system, namely, summer, autumn–spring, and winter conditions, including using peak-load sources. The operating modes have significant differences in the parameters of the heat-transfer medium, such as the flow rate and temperature of the network water.

Numerical Study on Melting Heat Transfer in Dendritic Heat Exchangers

The dendritic fin was introduced to improve the solid-liquid phase change in heat exchangers. A theoretical model of melting phase change in dendritic heat exchangers was developed and numerically simulated. The solid-liquid phase interface, liquid phase rate and dynamic temperature change in dendritic heat exchanger during melting process are investigated and compared with radial-fin heat exchanger. The results indicate that the dendritic fin is able to enhance the solid-liquid phase change in heat exchanger for latent thermal storage. The presence of dendritic fin leads to the formation of multiple independent PCM zones, so the heat can be quickly diffused from one point to across the surface along the metal fins, thereby making the PCM far away from heat sources melt earlier and faster. In addition, the dendritic structure makes the PCM temperature distribution more uniform over the entire zone inside heat exchangers due to high-efficient heat flow distribution of dendritic fins. As a result, the time required for the complete melting of the PCM in dendritic heat exchanger is shorter than that of the radial-fin heat exchanger.