Heating Regime Research Articles

Solar Flare Ribbon Fronts. I. Constraining Flare Energy Deposition with IRIS Spectroscopy

Spectral lines formed at lower atmospheric layers show peculiar profiles at the “leading edge” of ribbons during solar flares. In particular, increased absorption of the BBSO/GST He i λ10830 line, as well as broad and centrally reversed profiles in the spectra of the Mg ii and C ii lines observed by the IRIS satellite, has been reported. In this work, we aim to understand the physical origin of such peculiar IRIS profiles, which seem to be common of many, if not all, flares. To achieve this, we quantify the spectral properties of the IRIS Mg ii profiles at the ribbon leading edge during four large flares and perform a detailed comparison with a grid of radiative hydrodynamic models using the RADYN+FP code. We also studied their transition region (TR) counterparts, finding that these ribbon front locations are regions where TR emission and chromospheric evaporation are considerably weaker compared to other parts of the ribbons. Based on our comparison between the IRIS observations and modeling, our interpretation is that there are different heating regimes at play in the leading edge and the main bright part of the ribbons. More specifically, we suggest that bombardment of the chromosphere by more gradual and modest nonthermal electron energy fluxes can qualitatively explain the IRIS observations at the ribbon leading front, while stronger and more impulsive energy fluxes are required to drive chromospheric evaporation and more intense TR emission in the bright ribbon. Our results provide a possible physical origin for the peculiar behavior of the IRIS chromospheric lines in the ribbon leading edge and new constraints for the flare models.

Thermal creep of hybrid steel columns comprising ultra-high strength steel tubes and stainless steel plates under transient fire conditions

This paper investigates the behavior of an innovative steel column section both at room temperature and under the transient heating regime of building fires. The column consists of Grade 1200 ultra-high strength steel (UHSS) tubes welded to the corners of Grade 304 stainless steel plates, forming a square-shaped hybrid cross-section. First, through performing compressive tests on 780 mm long stub columns of the hybrid section at room temperature, its vulnerability to local buckling is assessed; accordingly, decision is made on the appropriate width of the plates. Then, six transient fire tests are conducted on the hybrid stub columns under three different compressive load levels. Due to the very fast heating rate of standard fire curves such as the ISO 834, the thermal creep of steel columns may be overlooked using these heating regimes, which may lead to an overestimation of the column’s resistance against building fires. Thus, a distinctive heating regime is adopted for the fire tests in this study; at any load level, two fast and slow heating rates are applied to the specimens. In this way, by comparing the results obtained, the effect of thermal creep on the fire resistance of the columns can be assessed. More importantly, the fire tests are used to verify finite element (FE) models developed for these hybrid columns in ABAQUS software; specifically, the creep model already developed for the UHSS tube and stainless steel plate materials is verified for component-level simulations. The verified FE modeling framework is then employed to perform an extensive parametric study on the effects of length, utilization factor, axial restraint stiffness ratio, and heating rate on the hybrid columns’ fire resistance. Finally, based on the results obtained from the parametric study, simplified design equations in the temperature domain are obtained for the axially-restrained hybrid steel columns under transient fire.

Approximate analytical method for calculating the heating process of concrete structures in heating formwork

The use of electric heating of concrete during construction in winter makes it possible to create an optimal thermal regime in which the hardening process takes place, and to obtain a structure of the required quality. When developing a system for automatic control of the heating process, it is necessary to determine the law of regulating the power of heaters. This article presents a method for calculating the thermal heating regime of concrete structures in heating formwork, the essence of which is to reduce the boundary value problem of thermal conductivity to a system of equivalent integral equations. To solve this problem, a theoretical study was carried out, a theoretical study of the heat transfer process in concrete structures heated during winter concreting was carried out, and a mathematical description of this process was presented in the form of a system of differential equations. After the transformations of the above system of equations and the application of the Green function of the second kind to it for the plate and rod, an approximate solution of the equivalent equation was obtained. As a result of the application of the asymptotic method to the solution of the integral equation, an analytical solution of the problem under consideration is obtained. The resulting solution makes it possible to determine the temperature fields on the concrete surface, as well as the value of the specific heat flux from electric heaters. In order to automate the process of performing the thermal calculation of heating concrete structures with the help of heating forms, a program for calculating temperature fields in heating forms has been developed based on the solution obtained, which makes it possible to effectively solve the tasks of monitoring and controlling the concrete hardening process. The developed program makes it possible to calculate temperature fields not only at constant heater power, but also when it changes with the help of regulators. The presented method of thermal calculation with a hardware and software complex for regulating the power of electric heaters allows solving a fairly wide range of tasks related to maintaining a constant temperature field.

AN EXPERIMENTAL STAND FOR RESEARCHING THE PROPERTIES OF SPENT FUEL ASSEMBLY DRY STORAGE

The paper analyzes the modern methods of storing spent nuclear fuel and its processing, taking into account the finding of fuel in spent fuel assemblies. Currently, the most common methods involve storage in containers for fuel assemblies filled with a substance that has a high thermal conductivity. Therefore, experimental methods of researching the storage properties of spent fuel assemblies in containers are promising. In the work, research was carried out in the indicated directions with the help of the created experimental stand. A description of the stand itself and the sequence of conducting the experiment are given, as a result of which the necessary experimental data should be obtained. Namely, the heating regimes in the experimental heater were determined, which are close to the real processes of heating spent fuel assemblies loaded into the container. For this purpose, a laboratory autotransformer with a capacity of 4.6 kW was used. The next task was to determine the time required for the heater to go into constant operation. For this purpose, the concept of constant time of the heating process was introduced. FLIR ONE thermal imager was used to determine this parameter, as well as devices that allowed to determine the voltage on the laboratory autotransformer. This made it possible to determine the dependence of the change in the temperature of the heater on time and voltage, as well as the voltage of the heater, which simulates real heating modes. The paper presents the thermographic results of thermal imager measurement of the main areas of the stand. Taking into account that the power of the heater should be about 1.5 kW, the stand was made airtight with pressure control and taking into account the real conditions of storage of spent fuel assemblies, where there may be damage and cracks in the container. As a result of the conducted experimental studies, the optimal heating modes of the heater were determined.

ВЛИЯНИЕ ПРОГРЕВА ИНКУБАЦИОННЫХ ЯИЦ ПЕКИНСКИХ УТОК КРОССА “STAR 53” НА КАЧЕСТВО СУТОЧНОГО МОЛОДНЯКА

The investigation resulted in some optimal regime of preliminary heating of peking “Star 53” cross ducks hatching eggs in these eggs keeping after laying. For example eggs heating during three days after laying has increased profit for 1 daily duckling to 30.8 rubles and profitability level to 44.5%.

Friction force determination between the inclined piles of the cotton gin drum from small impurities and seed of the fiber

Comprehensive measures are being implemented in our republic to develop cotton and textile clusters, modernize and re-equip cotton ginning enterprises, increase the profitability of production and primary processing of raw materials, and at the same time increase the competitiveness of products. One of the important issues is to provide cleaning equipment with cotton uninterruptedly and taking into account the heat and humidity regime, that is, the creation of an effective technology for preparing cotton for the cleaning process. Based on the experience of Jaxon, large-scale research and development work is being carried out to improve the technique and technology of primary processing of cotton. In this area, among other things, it is important to create an effective technology for cleaning cotton from impurities, optimizing the moisture-thermal parameters when cleaning cotton, creating resource-saving efficient designs of suppliers, optimizing modes and performance indicators. In this article, a formula is obtained for determining the friction force created by seeding the fiber on the surface of the pile, installed obliquely on the surface of the cleaning drum from small impurities. Based on the analysis of the connection graphs, built on the basis of a numerical solution, the recommended values of the parameters of the pile drum were determined.

Urban environment as a factor in the formation of the area microclimate

The growth of the leading countries’economies leads to the rapid development of megacities and changes in urban areas. Currently, more and more modern high-rise civil buildings are being built, resulting in an increasing density of urban areas and the activity of transport infrastructure. This causes major changes in the structure of urban development, which leads to a change in aeration and microclimatic conditions in urban areas. Solar radiation plays an active role in shaping the microclimate of the urban space, which aggravates the heat and wind regime of the urban environment. This is especially acute in the southern cities with hot climatic conditions. The article analyzes modern urban areas and factors affecting their microclimate. The role of temperature inversions in the formation of microclimatic conditions is indicated. Using the example of the yard space in Dushanbe, measurements and field studies were carried out; graphs of the climatic indicators of the urban area were plotted. The role of solar radiation in the formation of convective flows and microclimatic conditions of urban space is discussed.

Reducing the thickness of the insulation layer of building walls based on the study of their temperature and moisture regime

The thickness of the building insulation is calculated with the table values of the moisture of building materials, which is included in the regulatory documents with a margin. The study proposes the method for determining the thickness of the insulation layer using the values of operational moisture. To determine the operational moisture of materials, the equation based on the moisture potential is applied, the solution of which is sought using a discrete-continuum approach. The proposed equation makes it possible to determine the distribution of the moisture potential function in the wall enclosing structure. Thereafter, using the moisture potential scale, the distribution of mass moisture over the thickness of the enclosure for the period of maximum moisture accumulation is determined. The equation for determining the thickness of the insulation layer, in which the calculated value of the operational moisture is explicitly substituted, is derived. An algorithm for calculating the thickness of the insulation layer, taking into account the unsteady-state heat and moisture regime of the building envelope, is given. The application of the proposed method on a wall enclosing structure with insulation from expanded polystyrene boards is illustrated. It was found that the thickness of the insulation can be reduced by 26 mm from 120 mm to 94 mm while maintaining the reduced heat transfer resistance of the building wall. It is noted that the proposed method can be applied in the design of new wall enclosing structures.

Deformation Behavior under Tension with Pulse Current of Ultrafine-Grain and Coarse-Grain CP Titanium

The problem of the real existence of the electroplastic effect during deformation of metallic materials of different nature is still relevant. At the same time, the influence of structure refinement is not considered enough. In this work, the deformation behavior of ultrafine-grained (UFG) titanium Grade 4 is compared with that of coarse-grained (CG) titanium under tension with pulse current of the low duty cycle. The deformation curves of both structure states are presented for different regimes of pulsed current and thermal heating from an external source. Structure studies by optical and scanning electron microscopy, as well as microhardness measurements have been carried out. It is shown that Grade 4 titanium under tension accompanied by pulsed current exhibits electroplastic effect (EPE) in the form of a flow stress reduction. EPE in UFG state is much stronger than in CG state. An increase in the density and duration of the current pulse leads to a multiple decrease in the flow stresses in CG and UFG titanium. The contribution in the flow stress reduction from heating by an external source was less than that from tension with pulse current at the same temperatures. The impact of pulsed current during tension does not influence microhardness and grain size.

Residual bond‐slip behavior in reinforced concrete members exposed to elevated temperatures

AbstractMany reinforced concrete (RC) structures survive fire events, after which investigation of their residual performance becomes essential. The elevated temperatures experienced by structural members during a fire negatively impact the mechanical properties of concrete and steel, as well as their mutual bond. This paper investigates the bond behavior in RC members exposed to elevated temperatures to help designers check the safety of RC structures after a fire. Thirteen modified beam‐end specimens were designed and fabricated with two diameters of longitudinal bar (14 and 22 mm), two concrete strengths (30 and 50 MPa) and two confinement levels (0.8% and 1.6%). After being exposed to a variety of heating regimes and naturally cooling down to room temperature, the specimens were tested by applying a monotonic pull‐out force to their eccentric longitudinal bar. The results showed that after short‐term exposure to 400, 600, and 700°C, the residual bond strength may decrease by 23%, 58%, and 65%, respectively. The equations for the pull‐out failure proposed in the fib Model Code 2010 were found to yield realistic results in terms of upper and lower bounds for the bond behavior under monotonic loading, and the dependency of the residual bond strength on the square root of the residual compressive strength of the concrete was confirmed. Results were used to develop recommendations for the evaluation of the residual bond strength and of the development length in RC members exposed to elevated temperatures.

INCREASING CORROSION RESISTANCE OF WELDED JOINTS AS A RESULT OF HEAT TREATMENT

Welded joints with corrosion-resistant steels and heat-resistant alloys, which require different modes of heat treatment to achieve the level of mechanical properties specified in the design documentation, are used for the manufacture parts and assemblies of the rocket engine turbopump unit. Problem statement. In the production of rocket engine parts and components, due to difficulties in supplying materials from EU countries, Ukrainian machine-building enterprises have to substitute semi-finished products. It is necessary to replace sheet metal from high-alloy alloys with one alloy with a high complex of physical and mechanical characteristics. Materials and methodology. Inconel 718 alloy is selected as a substitute for heat-resistant alloys in welded joints with 316L steel. Results. As a result of comparative studies for resistance to intergranular corrosion of welded joints of heat-resistant alloy Inconel 718 with stainless steel after different modes of heat treatment the regime of low-temperature heating during soldering at 950 °С is recommended. Samples of welded joints treated according to the recommended mode showed increased corrosion resistance. Scientific novelty. The sensitivity to intergranular corrosion was found to result from the structural heterogeneity of the grain boundaries and the separation of secondary phases. Practical value. On the basis of experimental researches the mode of heat treatment with heating to 950 ± 10 0С, cooling to 300 0С − with the furnace, further − in air, instead of existing high-temperature heating to 1 200 0С is recommended, that promotes energy saving at welding of alloys.

Reduction of red blood spots in cooked marinated chicken breast meat by combined microwave heating and steaming

One of the defects commonly found in cooked marinated chicken breast products is a red blood spot (RBS), which is caused by undercooked blood in vessels. This problem was alleviated by microwave (MW) pre-heating for 6 to 7 min, followed by steaming. RBS formation decreased when samples were heated to a core temperature of 80°C and were completely eliminated at a core temperature of 82°C and 85°C when a MW pre-heating step was applied for 7 min. Based on synchrotron-based Fourier transform infrared spectroscopy (SR-FTIR), blood remaining in the blood vessel had a lower α-helical content when samples were cooked by the combination of MW heating and steaming as compared with those prepared by steaming alone (P < 0.05). MW pre-heating decreased cooking time by 28 to 48% as compared with steaming alone. Heating regimes had no effect on cooking loss, pH, water-holding capacity, and shear force. MW pre-heating for 7 min followed by steaming to a core temperature of 82°C appeared to be an effective heating regime to reduce the occurrence of RBS, with acceptable cooking loss.

Ionizing radiation source-open type fabrication using additive technology and spark plasma sintering

The paper presents an original method for open-type ionizing radiation source (IRS) fabrication by the means of spark plasma sintering-reactive synthesis (SPS-RS) of SrTiO3 ceramics as an active zone component reinforced by the titanium alloy framework produced by additive technology. Rapid heating regimes of SPS-RS are described with the focus on fabrication of perovskite-phase SrTiO3 crystalline ceramics integrated within the reinforcing Ti–Al–V framework yielding defect- and pore-free monolith. The product is characterized by the excellent crack resistance, Vickers microhardness (480–554 HV), and hydrolytic stability (leaching rate as low as 10−5 g/cm2·day). Presented results show bright prospects for high-tech radioisotope production in the form of open-type IRS meeting the requirements of international standards.

Efficient Multi-Layer Wall Panel

A comprehensive analysis of the multilayer wall panel has been performed. The heat-insulating layer, the thickness of which affects both the dimensions of the enclosing structure and the heat-shielding efficiency of the wall panel, has been studied,. Reducing the thickness of the thermal insulation layer is an important issue, since the production of three-layer panels is expensive in energy and material terms. The features of using a different number of screens to reduce the size of the thermal insulation layer are presented. An example of the possibility of a maximum reduction in the size of the heat-insulating layer, when the thickness of the interlayer din cannot be less than 3–5 mm is given. It is shown that the total thickness of the thermal insulation layer will be 0.057 m in the presence of the maximum possible number of screens – 12. For these conditions, the temperatures in the enclosure planes are calculated, according to the values of which the values of the maximum partial pressures E and partial pressures of water vapor e are determined (for the variants of perforated е¢ and non-perforated е¢¢ screens). According to the obtained values the dependences E, е¢, е¢¢ on the temperature in the planes of the fence are constructed. The calculations carried out and a general assessment of the heat and humidity regime in the enclosing structures were confirmed with the help of the compiled program and the calculation of the necessary parameters е and t in the layers of the structure. It has been established that various shielding materials can be used to exclude condensation zones during the operation of enclosing structures.

Rapid microwave sintering of centimetric zirconia: Scalability and electromagnetic‐thermal‐fluid‐dynamic simulation

AbstractMicrowave sintering is a method presenting the following advantages for flash sintering: contactless/volumetric heating, and the possibility to control the heating cycle of the microwave power. In this study, the transition from a typical 100 K/min to an ultra‐rapid heating rate of 500 K/min is studied. The heating homogeneity of the typical hybrid configuration using silicon carbide susceptors is tested up to the stability limit of the system. We show that zirconia specimens as thick as 10 mm can be heated and sintered up to 500 K/min heating rate at which thermal cracks appear. However, the centimetric size of the specimens seems to favor coarsening implying an important remaining porosity in the end. A comprehensive simulation including microwave heating and convection has allowed the determination of the heating regime transition during the flash process and the quantification of each specimen's cooling fluxes.

Zeno crossovers in the entanglement speed of spin chains with noisy impurities

We use a noisy signal with finite correlation time to drive a spin (dissipative impurity) in the quantum XY spin chain and calculate the dynamics of entanglement entropy (EE) of a bipartition of spins, for a stochastic quantum trajectory. We compute the noise averaged EE of a bipartition of spins and observe that its speed of spreading decreases at strong dissipation, as a result of the Zeno effect. We recover the Zeno crossover and show that noise averaged EE can be used as a proxy for the heating and Zeno regimes. Upon increasing the correlation time of the noise, the location of the Zeno crossover shifts at stronger dissipation, extending the heating regime.

Fire induced concrete spalling in combination with size effects

The size effect has its origin in fracture mechanics and describes the formation as well as propagation of cracks in brittle and solid materials in dependence of the specimen size. However, the size effect in concrete spalling describes the damage behaviour on a macroscopic scale for different sized specimens in case of fire. Concrete spalling is a very complex and yet not fully understood phenomenon. To reduce the effort of fire tests to analyse the spalling behaviour of concrete mixtures, this study investigates the susceptibility to spalling for six different concrete mixtures and three specimen sizes. The sizes were divided in full scale slabs (1.8 m × 1.2 m × 0.3 m), intermediate scale cuboids (0.6 m × 0.6 m × 0.3 m) and small scale cylinders (Ø0.15 m × 0.3 m). For this purpose, a novel test set-up was built to test six intermediate scale or twelve small scale specimens simultaneously to ensure a similar heating regime for every specimen. All specimens were fire exposed on one side and remained unrestrained. A size effect occurred for four of the six concrete mixtures. Compared to the full scale specimens the spalling was reduced significantly for all smaller specimen sizes. Additionally, spalling did not occur for the small scale specimens. The results show that the specimen size is an essential parameter to investigate the susceptibility to spalling of a concrete mixture. For future investigations the testing conditions must be adjusted for the intermediate scale specimens to recreate the conditions of the slabs.

Quadrupole Antenna and Diagnostic Complex for Ion Cyclotron Plasma Heating and Current Drive at the L-2M Stellarator

—A quadrupole antenna has been designed and produced at the L-2M stellarator for experiments on ion cyclotron plasma heating and current drive. Using a power meter of the incident and reflected waves, the first measurements of the radiation resistance of the antenna have been performed in the ohmic heating regime. The radiation resistance of the antenna has been measured as a function of the mean plasma density. It is shown that the fraction of absorbed power ensured by the coaxial modes is 25%. The created quadrupole antenna can also be used for current drive. The proposed method is based on the conversion of fast magnetosonic waves to slow magnetosonic waves with their subsequent absorption by plasma electrons, which is accompanied by current drive processes.

The Results of Different Heating Temperatures on Activities of Bioactive Proteins in Human Milk.

The most utilized pasteurization method in donor human milk banks is Holder pasteurization (heating 62.5 °C for 30 min). However, many bioactive proteins are heat sensitive and are inactivated. To determine the results of a range of heating regimes on the activities of xanthine oxidase, lactoperoxidase and lysozyme, the concentrations of immunoglobulin A and lactoferrin, as well as bacterial inactivation. This prospective, cross-sectional, intervention study was designed to measure the influence of heating temperatures on bioactive components in donor human milk. Milk samples were processed at 40, 50, 55, 62.5, 75, 127 °C and the activities of the enzymes, and the concentration of immune proteins, were measured. No bacterial colonies were detectable, using standard culture methods, after heating above 50 ºC. All proteins studied retained over 60% concentrations or activities when the pasteurization temperature was 50 ºC or lower, while their concentrations or activities were lost at higher temperatures. For lactoferrin, the residual concentration was above 80% when heating temperature was under 55 °C, while only 20% remained after Holder pasteurization. Both xanthine oxidase and lactoperoxidase had little residual activity when temperatures were above Holder pasteurization. Lysozyme retained a greater proportion of residual activity than other proteins, following heating at all temperatures. The concentrations or activities of immune proteins and bioactive enzymes decreased when heated above 50 °C. The results of this study can be used to design temperature control guidance during alternative methods of pasteurization.

In situ spectroscopic ellipsometry for temperature control in molecular beam epitaxy of HgCdTe

In situ temperature control is required to obtain HgCdTe layers of high crystalline perfection by molecular beam epitaxy. To solve this problem, we used spectroscopic ellipsometry. Various methods have been developed for measuring the temperature before the start of epitaxy. They are based on the analysis of different regions of the ellipsometric spectra of the CdTe buffer layer. An experimental comparison of the suggested methods shows that the temperature measurement accuracy is several degrees, and the sensitivity reaches fractions of a degree. At the stage of stationary growth of layers, it is possible to determine the change in temperature and composition from the kinetics of ellipsometric spectra. Ellipsometric measurements made during the growth of HgCdTe with a sharp change in the heating regime showed correlated changes in both temperature and composition.