Thermal Radiation Intensity Research Articles

Particle temperature and potassium release during combustion of single pulverized biomass char particles

This work investigated the combustion characteristics of single pulverized biomass-derived char particles. The char particles, in the size range 224–250 µm, were prepared in a drop tube furnace at pyrolysis temperatures of 1273 or 1473 K from four types of biomass particles – wheat straw, grape pomace, kiwi branches and rice husk. Subsequently, the char particles were injected upward into a confined region of hot combustion products produced by flat flames stabilized on a McKenna burner, with mean temperatures of 1460, 1580 and 1670 K and mean O2 concentrations of 4.5, 6.5 and 8.5 vol%. The data reported include particle temperature, obtained using a two-color pyrometry technique, and potassium release rate, measured using a laser-induced photofragmentation fluorescence imaging technique. In addition, particle ignition delay time and burning time, obtained from the temporal evolution of the thermal radiation intensity of the burning char particles, are also reported. The results indicated that ignition of the char particles occurs simultaneously with the starting of the potassium release, then the particle burning intensity increases rapidly until it reaches a maximum, after which both the particle temperature and the potassium release rate remain approximately constant until the end of the char oxidation process. The char ignition process is temperature controlled, and the char oxidation process is oxygen diffusion controlled, with the total potassium release being independent of the oxygen concentration and the temperature of the combustion products. The combustion behavior of the chars studied is more affected by the char type than by the conditions used to prepare them.

Physical characteristics of the thermal impact of an emergency fire

The article is devoted to the identification and analysis of the physical characteristics and thermal effects of a fire in an emergency situation. The main purpose of the work is to study the influence of physical damaging factors on the degree of danger of a potentially hazardous object. The article considers a deterministic method for assessing the effects of the action of a physical damaging factor (intensity of thermal radiation). The study is an effort to analyze the physical damaging factors of the fire, because it is the physical basis for an objective assessment of the danger and risk of an accident at the researched object.

Research on the influence of environmental factors on solid heat collection system

Heat collection from thermal radiation in the hydronic system of slab simulated to the solar collection on road in the summer was studied. An experimental system of thermal radiation was established to study influences of objective factors and their functions, such as thermal radiation intensity, wind speed, etc. The radiation intensity and wind speed of the slab surface experiments include the studies of heat collection quantity per surface area, temperature difference per pipe length, heat collection efficiency, and temperature of collection surface. The result showed that with increase of radiation intensity of slab surface, heat collection quantity increased but heat collection efficiency decreased. Under the unimodal dynamic radiation density, variation curves of the parameters which characterize the heat collection capacity follow an unimodal form, while variation curve of the heat collection efficiency is contrary to that of radiation intensity. The thermal response to this solid structure collection system has a significant delaying effect, in which heat capacity of solid structure is an important constraining factor. Therefore, these influencing factors and their effects have considerable importance for designing a solar energy collection system on road.

Industrial and ecological safety analysis for modeling oil and petroleum products spills in the Arctic waters of the Kola Bay

The paper analyses the industrial safety of the coastal and water areas of the Kola Bay of the Barents Sea when modeling the spill of oil or petroleum products. It gives a brief description of the methods and stages of liquidation of oil spills in the water and coastal areas as well as the main causes of accidents. It presents the results of physical and mathematical calculations in theoretical modeling of oil and petroleum products spills, namely: fire risk analysis, calculation of the minimum amount of combustible substance with partial destruction of the tank, calculation of probable areas of hazard boundary during an accident at the pump station, results of calculating the probability of explosion at the pumping station, and individual, collective and social risks. The most likely scenario is an event with partial depressurization (the probability will be 3.9·10−5 1/year): partial depressurization of the tank with liquid oil or petroleum products → oil slick formation → oil slick fire → personnel and equipment present in the hazardous area → exposure of people to thermal radiation. It was found that a minimum of 1182 kg of spilled crude oil is required for uncontrolled combustion to occur with an intensity of thermal radiation of not more than 4.2 kW/m2 m. The time to reach the maximum volumetric average temperature (894 K) in an accident at the pumping station is 136.8 minutes. In these calculations, the individual risk Rind = 3.31·10−5 1/year exceeds the regulatory standard, which shows an urgent need to reduce this risk. The collective risk is: Rcol total = 1.98·10−4 persons/year. Regarding the social risk, we can conclude that the minimum number of injured people will be three in case of an accident at the pump station or during the spill of oil or petroleum products into the Kola Bay, taking into account the fire development. The presented theoretical accident models will reduce the risk of major accidents involving petrochemical pollution of environmental objects, thereby preventing environmental damage, and the problem of the management of large oil spills at various facilities and technological systems of industrial enterprises will be solved.

The upgrade heat flux sensor application for early fire detection

The paper focuses on the description of the characteristics of the upgrade heat flux sensor, as well as the consideration of various models of its application to identify the source of combustion. The device uses a photovoltaic cell used to determine the thermal radiation intensity. The value thus defined is subsequently digitized and applied to determine the location of the radiation source. Among other things, this enables to use the device for finding the fire coordinates in order to extinguish it effectively using robotized fire complex. It is proposed to upgrade the device, which is to extend the temperature range of operation, and also to increase the speed and number of detectors in the line. The paper also provides a structural diagram of the functional sensor elements. A patent has been received for an improved device. Since the photovoltaic cell of a new sample with improved properties is used in the device, the article also provides an analysis of its characteristics, influence curves of the intensity of the heat radiation source on distance, as well as lines of constant signal strength. The data obtained were used to create three types of fire detection models, depending on the geometric parameters of the protected premises and the location of the combustible content source.

Интенсивность теплового излучения и радиусы зон разрушения установки первичной переработки нефти «атмосферно-вакуумная трубчатка»

Интенсивность теплового излучения и радиусы зон разрушения установки первичной переработки нефти «атмосферно-вакуумная трубчатка»

Pyrolysis and combustion characteristics and reaction kinetics of carbon fiber/epoxy composites

The pyrolysis and combustion characteristics and reaction kinetics of epoxy resin matrix and carbon fiber/epoxy composites based on epoxy resin were studied by cone calorimetry and thermogravimetry. The results show that with the increase in thermal radiation intensity (increase from 25 kW m−2 to 55 kW m−2), the average ignition time of the experimental samples decreases, the peak heat release rate increases, and the peak appears earlier. Carbon fiber can inhibit the pyrolysis and combustion of epoxy resin. It can effectively inhibit the droplet and splash phenomenon during the combustion process. The time of ignition, heat release, and the peak value of the heat release rate are delayed. The ignition temperature of foam core materials in carbon fiber/epoxy foam laminates is low, which makes the average ignition time and peak heat release rate appear earlier. The theoretical critical heat fluxes of four experimental samples (epoxy resin matrix, carbon fiber/epoxy bidirectional woven fabric, carbon fiber/epoxy prepreg, and carbon fiber/epoxy foam laminate) were obtained by calculation. The theoretical critical heat fluxes are 12.12 kW m−2, 13.21 kW m−2, 11.12 kW m−2, and 0.93 kW m−2, respectively. The pyrolysis of carbon fiber/epoxy bidirectional woven fabric can be divided into three stages: two stages of epoxy resin matrix decomposition and carbon fiber decomposition. The heating rate has a significant influence on the pyrolysis process. With the increase in heating rate, the maximum weight loss rate temperature moves toward high temperature. The Kissinger method and Flynn-Wall-Ozawa method were used to analyze the pyrolysis kinetics. The apparent activation energy and pre-exponential factors were obtained at different heating rates. The results obtained by the two methods are basically the same. When the pyrolysis temperature of the three composites reached 450 °C, the mass loss was 20%, 17%, and 28%, respectively. This shows that the thermal stability of carbon fiber/epoxy prepreg is the best, the thermal stability of the two-way woven fabric of carbon fiber is better, and the thermal stability of the carbon fiber sandwich board is the weakest. It is consistent with this rule at any temperature.

Infrared and Visible Image Fusion via L0 Decomposition and Intensity Mask

Image fusion integrates complex information about a target scene from multiple sensors into a single image. The fused image can further be utilized for human perception or different machine vision tasks. In the case of infrared and visible images, infrared images have the advantage of capturing thermal radiation intensity, whereas visible images are superior in gradient texture. In order to effectively fuse thermal intensity of infrared image and texture advantage of visible image, we propose a novel fusion method based on L0 decomposition and intensity mask. The proposed method first acquires base and detail layers of images (visible & infrared) using L0 decomposition. Next, an intensity mask is obtained using the basic global thresholding method on base layers of infrared image. The layers (base layers and detail layers) and visible images are divided images into three parts by the use of intensity mask, namely, mask-base layers, mask-detail layers, and texture-background. The first and second parts effectively achieve intensity blending, whereas the third part achieves the fused image with a clear gradient texture. The proposed method shows superior performance when compared with five state-of-the-art methods (on publicly available databases).

Effects of Detection Wavelengths on Soot Volume Fraction Measurements Using the Auto-Compensating LII Technique

ABSTRACT Soot particles in the detection volume in general have different temperatures due to non-uniform laser fluence and particle size distribution. The thermal radiation intensity displays different temperature dependence at different wavelengths. The effective soot temperature inferred from the ratio of laser-induced incandescence (LII) signals in the auto-compensating LII (AC-LII) technique is dependent on the detection wavelengths and affects the measured soot volume fraction. This paper numerically investigates the effects of detection wavelengths on the inferred soot effective temperature and volume fraction under conditions relevant to laminar diffusion flames at atmospheric pressure and for three representative laser fluence distributions. Numerical calculations were conducted using an LII model for a laser pulse of 5.8 ns FWHM and 1064 nm and assuming a lognormal primary particle size distribution and neglecting the aggregation effect. LII signals were modeled at four wavelength bands centered at 420, 560, 680, and 790 nm and the effective soot temperature was derived over three pairs of LII signals, namely [420, 560 nm], [560, 680 nm], and [680, 790 nm]. The two shortest and two longest detection wavelengths respectively result in the highest and lowest effective soot temperature when the laser fluence is non-uniform. The inferred soot volume fraction displays the opposite trend as the effective soot temperature. The effective soot temperature is biased toward the highest values and AC-LII always underestimates the soot volume fraction. The detection wavelengths should be carefully selected to minimize the impact of non-uniform laser fluence and at the same time to maximize the accuracy of effective soot temperature.

Incandescent Light Bulbs Based on a Refractory Metasurface

A thermal radiation light source, such as an incandescent light bulb, is considered a legacy light source with low luminous efficacy. However, it is an ideal energy source converting light with high efficiency from electric power to radiative power. In this work, we evaluate a thermal radiation light source and propose a new type of filament using a refractory metasurface to fabricate an efficient light bulb. We demonstrate visible-light spectral control using a refractory metasurface made of tantalum with an optical microcavity inserted into an incandescent light bulb. We use a nanoimprint method to fabricate the filament that is suitable for mass production. A 1.8 times enhancement of thermal radiation intensity is observed from the microcavity filament compared to the flat filament. Then, we demonstrate the thermal radiation control of the metasurface using a refractory plasmonic cavity made of hafnium nitride. A single narrow resonant peak is observed at the designed wavelength as well as the suppression of thermal radiation in wide mid-IR range under the condition of constant surface temperature.

Оптимизация методик расчета интенсивности теплового излучения

Оптимизация методик расчета интенсивности теплового излучения

Measurement of Thermal Cycle at Multi-Pass Layer Build-Up with Different Travel Path Strategies during DLMD Process

The shape of the parts, created by the technology of direct laser metal deposition (DLMD), is influenced by various parameters, for example, the power and diameter of the laser source spot. The contribution of energy from the laser affects the temperature distribution in the formed layers. The changing temperature in the working area entails a change in the geometry of the layers and affects the stability of the process. In this paper, experiments on the measurement of temperature cycles in the DLMD process with different directions of the filling track are carried out. An infrared camera was used to measure thermal cycles. The correspondence table between the intensity of thermal radiation of the material and the absolute temperature was developed. The experiments are carried out with the filler material 316L. The effect of the maximum temperature on the layer height is shown, and thermal cycles in the formation of layers for different filling strategies are presented.

Zinc oxide aluminum doped slabs for heat-eliminating coatings of spacecrafts

This paper discuss a possibility for using a thin-film functional coating based on transparent conducting thin films of aluminum doped zinc oxide (AZO) as a heat-eliminating material on the surface of a spacecraft. The structure of the functional coating has been chosen taking into account the plasmonic properties of AZO and silver and represents the AZO slabs with embedded silver nanoparticles deposited on AZO layer and AZO slabs with embedded silver nanoparticles deposited on thin film fused quartz layer. The paper contains COMSOL finite element simulations of the scattering cross section for thermal radiation in the IR band in the case the investigated coating deposited on a reflective aluminum film, and absorption cross section in the near UV and visible spectral bands when the coating deposited on silicon solar panels. The calculations demonstrate an increase in the scattering cross-section in the spectral band of blackbody radiation by several orders of magnitude, with the maximum in the scattering spectrum of the AZO slabs/ AZO /Al structure corresponding to the maximum intensity of the blackbody thermal radiation, which has been heated to 100 °C in the case the lattice period of the AZO slabs is equal to the resonance wavelength for AZO. Also an increase in the absorption cross-section of AZO slabs/ AZO /Si structure in visible spectral band is observed corresponding to plasmon absorption of embedded silver nanoparticles.

Forecasting of technogenic risks in draining and filling operations at Svirsk gas station

In Svirsk, oil is supplied through the petrol station. Petrol stations are a source of technogenic danger as they use flammable substances - liquid motor fuel. It is necessary to assess the emergency risks during the loading and unloading operations. The simulation of emergency situations of tanker depressurization was performed. The software package TOXI+Risk was used for modeling. It was used to estimate the zones of damage factors in the emergency situation causing oil spilling and assess potential risks. The precition modeling of emergency situations during depressurization of a tanker was carried out. Possible causes of emergency oil spilling were identified and the graph-analytical model "failure tree" and "event tree" based on the logical-probabilistic approach was developed. During the tanker depressurization, fires are probable. The damage factors (intensity of thermal radiation) were determined a distance of up to 30 m. The simulation of consequences of explosions of the fuel-air mixture (FAM) showed the probability of damaging factors that cause damage and injuries. Collective and social risks for the personnel and third parties were calculated; fields of potential risk were developed. Zones of damaging factors cover only the territory of gas stations and do not reach residential areas. Predictive analysis of technogenic risks showed the possibility of emergency situations caused by tank depressurization, fuel leakage and fire. The predicted accident is of local character.

Human thermal risk prediction in indoor hyperthermal environments based on random forest

Indoor hyperthermal environments pose a huge threat to the occupants. Predicting workers’ thermal risk in indoor hyperthermal environments contributes to the health and safety at work and the control strategies of indoor hyperthermal environments. Moreover, the quantitative effects of heat acclimation (HA) on the thermal risk are unknown and the weightings of the factors influencing thermal risk need to be determined. To these ends, the simulation experiments were conducted in a climate chamber. The subjects were asked to do treadmill exercise to simulate manual labor. During the experiments, core temperature, heart rate, and subjective perception were recorded. Significant differences were found on the physiological strain index and perceptual strain index before and after HA, which indicate that HA could reduce the thermal risk. Air temperature (Ta), relative humidity (RH), thermal radiation intensity (TRI), clothing insulation (CI), intensity index of physical work (IIPW), and labor hour (LH) were selected as the predictors of the human thermal risk. Given the effect of HA, the non-HA and HA model were built using random forest (RF) with the accuracy of 95.15% and 94.01%, respectively. In addition, the weightings of six contributing factors were determined, and Ta and LH were the most important among them.

How hot is the wire: Optical, electrical, and combined methods to determine filament temperature

The filament temperature T is a key parameter in hotwire-assisted chemical vapor deposition (HWCVD). Three common methods for the in-situ determination of T are based on the measurement of electrical resistance, electrical power, or intensity of thermal radiation at one or more wavelengths λ. This work discusses the errors due to assumptions in these methods, primarily when an assumed resistivity ρ(T) or spectral emittance εs(λ,T) does not match the sample. Further, a method is introduced to find the temperature of a filament behind a viewport with unknown transmittance, and without the need to have references for ρ(T) or εs(λ,T). This method combines multiple thermal radiation spectra at varied radiating power and assumes that εs(λ,T) is independent of T within the resulting variation in T. The combined optical-electrical method is within 30 K in agreement with pyrometry around 2000 K for the real-life filament, and within 20 K of the true T when applied to simulated data of a W filament for which T is known.

Application of phase-change material in solar hot-water system

In this paper, hydrated salts of disodium hydrogen phosphate dodecahydrate and disodium sulfate decahydrate are employed to compose a composite hydrated salt with a ratio of 9·5:0·5. The composite hydrated salt has been used as a phase-change thermal storage material in a solar hot-water system to study the effect of phase-change material on the thermal conversion efficiency of such a system. The phase-change material is packaged in a plastic container. The experimental results show that the thermal conversion efficiency is significantly affected by the amount of thermal storage medium and solar radiation intensity. The solar thermal conversion efficiency for the 2 m2 solar panel collector could reach up to 66·4% for a thermal storage medium consisting of 38·1 kg phase-change thermal storage material and 124·7 kg water and with an averaged radiation intensity of 1243 w/m2, even at lower ambient temperatures between −7·0°C in the morning and 1·0°C at 15:00. It indicates that the use of phase-change materials in a solar water-heating system could improve the solar thermal conversion efficiency of such a system.

A Laser Joining System for Titanium and Polyethylene Terephthalate Plastic Controlled by Multiple Signal Sources

Laser direct joining of metal and plastic plays a significant role in manufacturing of multiple material structures. To improve the strength of the joint, a controllable laser joining system was developed for polyethylene terephthalate plastic and titanium based on the detected multiple signal sources. The main contribution of this paper lies in sensing 1) the intensity of thermal radiation to control process heat by adjusting the laser power; and 2) the reflection of the helium–neon laser to control the movement of the specimens. The response speeds of thermal radiation intensity when increasing or decreasing the laser powers were measured to guide the adjustment of laser power. The intensities of reflective light before and after the joining process were measured to guide the movement control. Then, the integrated control process was set up. Width, tensile shear strength, and fracture position of the joint produced by the controllable joining system were compared with those produced by the conventional constant power method, which validated the advantage of this newly developed system.

Study of thermal radiation of the elastic-damping elements of the air suspension of the seat on the hydropulsator test bench

Air suspension of seat is one of the most important components of the system of vibration protection of the human operator of the vehicle. All vibrational energy transmitted through the suspension of the seat from the cab floor to the driver is stored, absorbed and later dissipated by means of elastic damping elements, turning into heat. An assessment of the intensity of thermal radiation from the air spring and the shock absorber during operation may further improve the design of existing seat suspension systems. As an example, we can mention the possibility of vibrational energy recovery, which in regular passive suspensions turns into heat when extinguished. The article presents the results of tests of the air suspension of the seat of the company Sibeco on a single-support test bench with a hydraulic drive manufactured by the Indian company BiSS. The purpose of the test is to study the thermograms of the surfaces of the elasticdamping elements during operation. An experimental setup, which includes the metal elements of the connection of the actuator of the hydropulsator test bench with a shock absorber and the suspension of the seat as a whole, as well as a force sensor built into the design of the stand, is described. The working diagrams of the shock absorber and air suspension of the seat at each fixed point in time of one minute are obtained. To measure the values of temperature and read surface thermograms the Testo thermal imager was used. The study was conducted on the harmonic mode of exposure. During processing and analyzing the obtained data, the nature of the heating of the outer surface of the shock absorber and the air spring, as well as the fact of reaching stabilization temperatures, were revealed. In conclusion, the reasons for the discrepancy between the intensity of thermal radiation of the air spring and the shock absorber of the seat suspension are given.

Effects of forced convection and thermal radiation on high expansion foam used for LNG vapor risk mitigation

Liquefaction of natural gas is an effective way of easily storing and transporting natural gas because of its high ratio of liquid to vapor densities. Any spill of liquefied natural gas (LNG) can result in the formation of a vapor cloud, which cannot only cause asphyxiation but can also migrate downwind near ground level because of a density greater than air and has the potential to ignite. The NFPA recommends the use of high expansion foam to mitigate the vapor risk due to cryogenic LNG. This paper studies the effects of heat transfer mechanisms, such as forced convection and thermal radiation on high expansion foam breakage, with and without a cryogenic liquid. A lab scale foam generator was used to produce high expansion foam and carry out experiments to evaluate the rate of foam breakage, the amount of liquid drained from foam, the vaporization rate of the cryogenic liquid, and the temperature profile through the foam. High expansion foam breakage was found to depend on the amount of wind induced forced convection and thermal radiation. At the highest wind speed (2.5 m/s) and thermal radiation intensity (270 W/m2) measured, foam breakage was found to be nearly 3 and 5 times the value without any wind or thermal radiation, respectively. Liquid drainage from the foam was found to affect the vaporization rate of the cryogenic liquid, especially immediately after foam application. Accounting for external factors such as forced convection and thermal radiation can help provide a better estimate for the amount of foam that needs to be applied for effective vapor risk mitigation.