Thermal Energy Distribution Research Articles

The Westcott convention converted in the extended version of the modified Høgdahl convention

In k0-NAA it is common practice to use the modified Hogdahl convention for the description of (n, γ) activation. This convention is based on the principle that the activation cross-section in the thermal neutron range is following a 1/v shape, which results in an activation rate is independent of the speed distribution of the neutron density. For some isotopes, this is not the case. We call these isotopes “non-1/v”. For these nuclides, the activation rate in k0-NAA theory is described by the Westcott convention. Westcott uses a Maxwellian thermal neutron energy distribution comprised in a neutron temperature dependent “g”-factor. For the activation by epithermal neutrons a “s”-factor is defined. In this paper, the original Westcott convention is converted into an extension of the Hogdahl convention. The benefit is that Hogdahl’s flux parameters can be used. The epithermal flux description defined by Westcott is used to calculate extended QE’s with their appropriate effective resonance energies, Er. Since Westcott flux descriptions are neutron temperature dependent, the QE’s and Er’s are as well. All the data needed for the evaluation of concentrations for Lu, Eu and Yb based on their non-1/v nuclides using the standard Hogdahl flux parameters are presented.

Improving a resource­saving surfacing technology using two ribbon electrodes with a controlled transfer of electrode's metal

This paper reports results of research into a resource-saving technology of surfacing with two ribbon electrodes with a controlled transfer of the electrode's metal from the end sides of ribbon electrodes and with an adjustable ratio between the ribbon electrodes' feed speed. To implement the proposed technology of surfacing, we designed a device that makes it possible to change the ratio between feed speeds of the first and second electrodes in a wide range. That provides for a controlled heat-mass transfer to the welding bath. As well as, accordingly, a controlled fusion of ribbon electrodes and the distribution of thermal energy throughout a welding bath. This makes it possible to improve quality of the surfaced products using a simple and reliable resource-saving device. A given design makes it possible to optimize parameters for a pulsed mechanical transfer and prevent the deformation of ribbon electrodes, to ensure an alternating reciprocation motion of the ribbon electrodes' end sides at optimal frequency and amplitude. That provides for the optimal size of the surfaced bead while making it possible to reduce the consumption of an electrode's metal for loss and overheating, and, accordingly, the consumption of energy for melting, as well as ensure a resource saving technology of surfacing. The process of surfacing with two electrodes, even when using fluxes recommended for arc welding, occurs partially similar to the electroslag process, because a certain percentage of current is shunted by the molten slag. This helps reduce the depth of welding and lowers the share of the base metal in the surfaced metal. The main advantage of surfacing with two ribbon electrodes is obtaining the surfaced metal with the required chemical composition as early as in the first or second layer, in contrast to the single-electrode surfacing where it is necessary to apply from 3 to 5 layers. Results of research into the influence of oscillation frequency of ribbon electrodes have revealed that the maximum increase in a melting coefficient occurs at oscillation frequency in the range of 45‒55 Hz regardless of other mode parameters

Energetic Analysis of the Aircraft Diesel Engine

The analysis of the distribution of thermal energy generated during the combustion process in internal combustion engines and the estimation of individual losses are important regarding performance and efficiency. The article analyses the energy balance of the designed two-stroke opposed piston diesel engines with offset, i.e. the angle by which the crankshaft at the side of exhaust ports is ahead of the crankshaft at the side of intake ports. Based on the developed zero-dimensional engine model, a series of simulations were performed in steady-state conditions using the AVL BOOST software. The values of individual energy losses, including cooling losses, exhaust gas losses, friction losses were obtained. The influence of decreasing and increasing the offset on the performance of the tested engine was analysed.

Thermal Energy Approach for Aluminium Process Simulations: Source-Capacity Technique

The multi-physical and multi-phased industrial process simulations for aluminium processes have many benefits which become clear by exploring what is actually happening during the process. For numerical simulations of continuous and semi-continuous material processes (i.e., casting…), to account for continuous thermal energy input (melt flow) and output (thermal dissipation, cooling, radiation…), a thermal balanced technique is developed. In the research work herein, the continuous melt flow (and thermal energy input) is simulated using novel evolving domain technique where stepwise layers of numerical grid are added to existing domain considering dynamic boundary changes and special new thermal energy distribution technique

Thermodynamics analysis of S-CO<sub>2</sub> recompression-reheating cycle for coal fired power plant

As a kind of fossil energy, coal plays an important role in global energy structure. In China, coal fired power plants provide more than 60% of the total electricity supply. Compared to the water-steam Rankine cycle, the supercritical carbon dioxide (S-CO2) Brayton cycle exhibits advantages in simpler cycle layout and higher efficiencies. The objective of this paper is to explore the possibility that the S-CO2 Brayton cycle can be used for large scale coal fired power plant. Such application presents challenges in the thermodynamic cycle construction, arrangement of heat transfer components and residual heat utilization of flue gas. Here, the S-CO2 recompression cycle, incorporating reheating/double-reheating technique, is integrated with the coal fired power plant. The performance of the power plant is analyzed by coupling the thermodynamics cycle, boiler pressure drops in heat transfer components, and thermal energy distribution of flue gas in the boiler tail flue. The residual heat of flue gas is absorbed by the S-CO2 cycle, an additional flue gas cooler (FGC) and two air preheaters to satisfy the energy cascade utilization principle. The results show that, if the S-CO2 recompression cycle is used alone without reheating, the low-temperature flue gas energy is difficult to be absorbed to cause non-acceptable outlet flue gas temperature such as higher than 120°C. By neglecting pressured drops in heat transfer components, the S-CO2 recompression cycle incorporating reheating increases the system thermal efficiency, but makes it difficult to recover the residual heat of flue gas. When pressure drops are considered, we show that, for the first time, the curves of thermal efficiencies versus reheater pressure drops are crossed between the S-CO2 recompression-reheating cycle and the S-CO2 recompression-double-reheating cycle. Based on this finding, the criterion is proposed to judge at what condition a single-reheating cycle is needed, and at what condition a double-reheating cycle is necessary. It is demonstrated that the CO2 temperature entering the boiler can be decreased by elevating the main vapor pressure. Thus, the adjusting main vapor pressure method is proposed to absorb the residual heat of flue gas. The system efficiency is sharply increased with increase of main vapor pressures. Because the main vapor temperature T 5 and pressure P 5 are strongly coupled, for example, P 5 reaches 43.6 MPa at T 5=615°C and the secondary air temperature of 500°C, the adjusting main vapor pressure method challenges the material pressure tolerance limit. Adding a flue gas cooler (FGC) not only recovers the residual heat of flue gas, but also ensures that the pressure is within the material pressure tolerance limit. The optimal scheme of the FGC integrated with the thermal cycle is investigated, among which, a smaller CO2 flow rate stream consecutively extracted from the main compressor outlet, being heated by the low temperature flue gas, and entering the outlet of the low temperature recuperator heat exchanger, is the best. By using the S-CO2 recompression-reheating cycle together with a FGC, the system thermal efficiency and boiler efficiency attain 50.82% and 94.43%, respectively. This paper gives a clue to design and operate high efficiency, simple layout and compact S-CO2 coal fired power plant.

Development of High Efficiency and Cost Effective Energy Generation Novel Technology

During last, many years the electrical energy is generated in large Thermal Power Plants (TPP) and Nuclear Power Plants (NPP). Thermal Power Plants are the main electricity generating stations that are functioning based on the principle of thermal energy conversion into mechanical and finally into electrical energy. The noted conversion is accomplished by the condensation type of thermodynamic cycle that is called “Rankin” cycle. There are in use Co - generation heat and power plants too, which are functioning based on “Bryton” thermodynamic combined cycle. These plants are assigned for simultaneous generation and distribution of thermal and electrical energy. For this reason, they are more efficient. However, all mentioned cycles and conforming to them power plants serving for generation and distribution of large quantity of electricity from energy generating centralized stations to large number of consumers, which are located in significantly long distance from generating stations. The analysis of existing practice of use of mentioned types of electricity generating powerful centralized stations because of large losses of energy are not enough efficient and cost effective. For instance, the COP of electricity generating station, working by well-known Rankin cycle, makes only 30%, because about 70% of produced thermal energy should be lost to the surrounding environment for providing required conditions of electricity production. It is obvious that such big energy loses extremely pollute the environment, provoke global climate change and forces Governments adopting more forceful approaches to reduce carbon and other harmful gases rejections, increase efficiency of energy generation and improve environmental situation. For this reason, after having studied the potential possibilities of reduction of harmful gases rejections and increase of energy efficiency of electricity generation conventional mods the authors of this article became convinced in impossibility of assigned task and have decided to suggest novel and higher efficiency technology for electric energy generation. From this, point of view this article may become a guideline that can help to improve the present environmental and economic situations.

Study of factors affecting the reliability of turbochargers

The thermal loading factors of the turbocharger affecting the reliability are considered. The ways of reducing the heat load of the turbocharger elements are analyzed. The scheme of the turbocharger rotor thermal optimization, as well as options for changing the shape of the rotor. The thermal analysis of the rotor by the finite element method is performed. The temperature distribution on the surface and in the rotor section is obtained. Composed vector representation of the heat flux at the nodes of the rotor. The conclusion about the influence of changes in the shape of the turbocharger rotor on the distribution of thermal energy is given.

Development of the Device for Two-Strip Cladding with Controlled Mechanical Transfer

A two-tape electrodes surfacing device with controlled transfer of electrode metal is proposed. The kinematical scheme and parameters of the process were investigated. It is established that the application of the developed device allows providing a more equable distribution of thermal energy across the width of the tape electrodes and a controlled dropping of liquid metal droplets.

Study of ocean thermal energy resources in Para’baya, West Sulawesi

Ocean thermal is one of the renewable energy resources. In 1981, a design of Ocean Thermal Energy Conversion (OTEC) pilot power plant was proven could produce electricity. The performance of OTEC depends on the possible temperature differences of the warm and cold seawater, at least 20°C. In the coastal of Para’baya, this requirement can be satisfied since the distance to reach the 1000 m depth is less than 10,000 m from the shore. The result of ocean thermal power calculation in Makassar Strait shows that Para’baya could produce higher power than any other place in west coast of Sulawesi, with an average power output of 120.35 kW. This ocean thermal study, in the coast of Para’baya, used sea surface temperatures (SST) data from the result of Long-term Indonesian Throughflow Model Simulation (LITHMOS) over 24 years (1982 – 2006), and sea temperature data at 1000 m depth from the World Ocean Atlas (WOA) 2009. The result shows that ocean thermal energy distributions in the Makassar Strait were affected by the combination of gust, wind direction, and sun position which varies in each season. Maximum ocean thermal power is reached during the first transitional season (March, April, May) with output power of 128 kW, and the minimum power is achieved during the dry season (June, July, August) with an output power of 114 kW.

Wall Temperature Measurements Within a High-Power Inductive Plasma Discharge

Electromagnetic plasma generators (inductive and helicon) are commonly used for planetary entry simulation and increasingly for electric propulsion applications. However, one obstacle in increasing the power and efficiency of these systems is a lack of knowledge regarding the distribution of tube wall temperature. The tube wall temperature acts as a mechanical limit to the thruster/generator operating conditions and is directly related to the distribution of thermal energy within the discharge volume. This paper presents the results of an experimental investigation to determine spatially resolved wall temperatures in a 180 kW inductive plasma generator. This investigation showed that significant wall heating does not occur until the midpoint of the inductive coil, increasing rapidly to reach peak temperature over a distance 15% of the total tube. During this rapid heating phase, one-third of the total tube heat flux is produced, assisting in quantifying previously observed mechanical failures due to thermal stress. The peak temperature difference between inner and outer wall surfaces was recorded as 619.1 K, approximately twice that of the previously proposed limit which considered integral rather than spatially resolved values. Using the results of this investigation, a refined estimate of critical wall temperatures for various tube thicknesses has been developed, allowing more targeted cooling systems to be implemented in the future generator designs.

The District Heating in the Context of the Active Consumers Development in Smart Energy Systems

The paper defines the main factors of the smart energy systems that influence on the district heating. Noted increase in the regulatory impact of electric energy system on the district heating and increase in roles of the distribution and consumption of thermal energy. Urban population and other consumers of energy become equal partners of the utilities and acquire the status of "active" consumers. The heating supply companies need to develop a new model of management of heating regimes with dynamic synchronization with energy system and "active" consumers. One of the most important conditions of the achievement of the cost reduction, reliability and quality increase in community facilities is active consumer's behavior.

Modelling of Direct Connection of Heat Consumers to District Heating with Ejectors

Energy requirements by thermal consumers are continually increasing as a result of the growing standards of living conditions. Thus, to meet the demands with thermal energy, and to use thermal energy more efficiently it was seen a reason to do the following analysis with the purpose of finding the influence of the most efficient distribution of thermal energy for the district heating of Pristina city. The current paper describes the operation of the ejectors applied for direct connection by mixing the hot water from district heating network with the cold water used for heating systems. This paper is, based on the simulations analysis of the water supply temperatures at the secondary network t ws2 , which are, derived from the modelling of ejector compared with water supply temperatures, which uses the enterprise of Termokos with heat exchangers. Furthermore, the results gained by CFD modelling have shown considerable thermal energy savings potentials and will be useful for the maintained engineer of district heating of Pristina City to make a suitable prediction of the design specifications to use thermal energy more efficiently.

Effects of geometrical structure on spatial distribution of thermal energy in two-dimensional triangular lattices

Employing the correlation matrix technique, the spatial distribution of thermal energy in two-dimensional triangular lattices in equilibrium, interacting with linear springs, is studied. It is found that the spatial distribution of thermal energy varies with the included angle of the springs. In addition, the average thermal energy of the longer springs is lower. Springs with different included angle and length will lead to an inhomogeneous spatial distribution of thermal energy. This suggests that the spatial distribution of thermal energy is affected by the geometrical structure of the system: the more asymmetric the geometrical structure of the system is, the more inhomogeneous is the spatial distribution of thermal energy.

Synchrotron Polarization of Relativistic Thermal Electrons

Abstract Relativistic electrons accelerated by both the first-order and the second-order Fermi accelerations in some synchrotron sources have a hybrid shape of thermal and nonthermal energy distribution. This particle acceleration result is supported by some recent numerical simulations. We calculate the synchrotron polarization by applying this electron energy distribution. The polarization degrees in the cases of active galactic nucleus jets and gamma-ray bursts are given as examples. The possible application for the polarization study of Sgr A* is also mentioned. We finally suggest high-energy polarization measurements for these synchrotron sources to test our results.

Microstructural properties of a dissimilar friction stir welded thick aluminum aa6082-t6 and aa7075-t6 alloy

Friction stir welding is a severe plastic deformation process. This solid state welding procedure has recently received a general acceptance in the aerospace industry for joining difficult to weld aluminum alloy using the conventional method. A 10mm thick AA6082 and AA7075 in tempered form (T6) were friction stir welded in butt configuration as against the previous research on 4mm, 6mm and 8mm thicknesses respectively. The response of the stir zone (SZ) microstructure to processing parameters was evaluated using optical microscope (OM), Stereo microscope (SM) and scanning electron microscope (SEM) respectively. The magnitude forge force (kN) at the tool shoulder directly affect the flow of the extruded materials through the tool probe. The distribution of thermal energy, dissolution, precipitation and re-precipitation of solute influences the materials flow and properties evolution. Hence, equiaxed grain structures observed were due to the dynamic recrystallization mechanism at the weld nugget. Some microstructure imperfection were observed at the weld nugget when AA6082 aluminum plates were clamped on the retreating side to the backing plate. However, the material flow and mixing was not sufficient to establish good bonding and quality welds due to deviation in the positioning of the aluminum plates.

Non-invasive tests of precast cantilever balcony in OWT-67 system

This article presents a non-invasive tests report of precast cantilever balcony support in OWT-67 large-panel system. During field testing, the balcony's reinforced concrete structure was subjected to radiometric analysis in the context of thermal energy distribution as well as from the point of view of mycology - to the possible presence of spores of domestic fungi. The temperature distribution tests carried out by means of the electromagnetic wave detection in the infrared spectrum clearly confirmed the significant losses of thermal energy caused by the effect of the thermal constructional bridge located in the balcony. Mycological diagnosis was carried out using the rapid test of the Mycometer bacterial meter, which allows fluorimetric evaluation of the presence of the enzyme presence in filamentous fungi. In the conducted study, no spores of the house mushroom were found on the inside surface of the Z-type balcony supporting beam as a place where condensation of water vapor may occur. The summary also presents a design solution that allows to eliminate this physical problem.

Semantic Segmentation of Human Model Using Heat Kernel and Geodesic Distance

A novel approach of 3D human model segmentation is proposed, which is based on heat kernel signature and geodesic distance. Through calculating the heat kernel signature of the point clouds of human body model, the local maxima of thermal energy distribution of the model is found, and the set of feature points of the model is obtained. Heat kernel signature has affine invariability which can be used to extract the correct feature points of the human model in different postures. We adopt the method of geodesic distance to realize the hierarchical segmentation of human model after obtaining the semantic feature points of human model. The experimental results show that the method can overcome the defect of geodesic distance feature extraction. The human body models with different postures can be obtained with the model segmentation results of human semantic characteristics.

Investigating the Thermodynamic Performances of TO-Based Metamaterial Tunable Cells with an Entropy Generation Approach

Active control of heat flux can be realized with transformation optics (TO) thermal metamaterials. Recently, a new class of metamaterial tunable cells has been proposed, aiming to significantly reduce the difficulty of fabrication and to flexibly switch functions by employing several cells assembled on related positions following the TO design. However, owing to the integration and rotation of materials in tunable cells, they might lead to extra thermal losses as compared with the previous continuum design. This paper focuses on investigating the thermodynamic properties of tunable cells under related design parameters. The universal expression for the local entropy generation rate in such metamaterial systems is obtained considering the influence of rotation. A series of contrast schemes are established to describe the thermodynamic process and thermal energy distributions from the viewpoint of entropy analysis. Moreover, effects of design parameters on thermal dissipations and system irreversibility are investigated. In conclusion, more thermal dissipations and stronger thermodynamic processes occur in a system with larger conductivity ratios and rotation angles. This paper presents a detailed description of the thermodynamic properties of metamaterial tunable cells and provides reference for selecting appropriate design parameters on related positions to fabricate more efficient and energy-economical switchable TO devices.

Ultrafast carrier thermalization in lead iodide perovskite probed with two-dimensional electronic spectroscopy

In band-like semiconductors, charge carriers form a thermal energy distribution rapidly after optical excitation. In hybrid perovskites, the cooling of such thermal carrier distributions occurs on timescales of about 300 fs via carrier-phonon scattering. However, the initial build-up of the thermal distribution proved difficult to resolve with pump–probe techniques due to the requirement of high resolution, both in time and pump energy. Here, we use two-dimensional electronic spectroscopy with sub-10 fs resolution to directly observe the carrier interactions that lead to a thermal carrier distribution. We find that thermalization occurs dominantly via carrier-carrier scattering under the investigated fluences and report the dependence of carrier scattering rates on excess energy and carrier density. We extract characteristic carrier thermalization times from below 10 to 85 fs. These values allow for mobilities of 500 cm2 V−1 s−1 at carrier densities lower than 2 × 1019 cm−3 and limit the time for carrier extraction in hot carrier solar cells.

Doppler cooling thermometry of a multilevel ion in the presence of micromotion

We study the time-dependent fluorescence of an initially hot, multi-level, single atomic ion trapped in a radio-frequency Paul trap during Doppler cooling. We have developed an analytical model that describes the fluorescence dynamics during Doppler cooling which is used to extract the initial energy of the ion. While previous models of Doppler cooling thermometry were limited to atoms with a two-level energy structure and neglected the effect of the trap oscillating electric fields, our model applies to atoms with multi-level energy structure and takes into account the influence of micromotion on the cooling dynamics. This thermometry applies to any initial energy distribution. We experimentally test our model with an ion prepared in a coherent, thermal and Tsallis energy distributions.