scholarly journals Changes in the Distribution of Temperature in a Coal Deposit and the Composition of Gases Emitted during Its Heating and Cooling

2018 ◽  
Vol 10 (10) ◽  
pp. 3587 ◽  
Author(s):  
Marek Więckowski ◽  
Natalia Howaniec ◽  
Eugene Postnikov ◽  
Mirosław Chorążewski ◽  
Adam Smoliński
Keyword(s):  
Fire Hazard ◽  
Hot Spot ◽  
Measuring System ◽  
Hard Coal ◽  
Coal Deposit ◽  
Hazard Indices ◽  
Heating And Cooling ◽  
Cooling Phase ◽  
Percentage Share ◽  
The Given

This article presents the results of tests conducted on a measuring system for monitoring changes in the distribution of temperature in a coal deposit during the heating and cooling phases, and their correlation with the analysis of the concentration of gases. The tests were conducted on five samples of hard coal collected in deposits mined in Poland. Measurements of the changes in temperature and changes in gas concentration were conducted from the temperature of 35 to 300 °C, for the heating phase, and from 300 to 35 °C, for the cooling phase. The percentage share of coal of given temperatures was calculated. When comparing the percentage share for the same temperature in the hot spot, for the heating and cooling phase, significant differences in the distribution of the given percentages were observed. Changes in gas concentrations during heating and cooling were analyzed and the dynamics of changes in gas concentrations were determined for the coals tested. Changes in the values of fire hazard indices were analyzed. There were significant differences in the concentration of gases and the values of fire hazard indices between the heating and the cooling phase. The application of different criteria to assess coal during heating and cooling was proposed.

scholarly journals Assessment of Heating and Cooling of a Spontaneous Fire Source in Coal Deposits—Effect of Coal Grain Size

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 907
Author(s):  
Marek Więckowski ◽  
Natalia Howaniec ◽  
Adam Smoliński
Keyword(s):  
Carbon Monoxide ◽  
Hazard Assessment ◽  
Fire Hazard ◽  
Temperature Drop ◽  
Coal Bed ◽  
Coal Deposit ◽  
Fire Source ◽  
Heating And Cooling ◽  
Spontaneous Fire ◽  
The Impact

Fire hazard assessment in coal mines is performed on the basis of concentrations of particular gases emitted from the heating coal deposit, but more precise criteria and indicators are needed to assess fire hazard properly—both during the temperature rise phase and in the coal bed cooling phase. In the paper the impact of coal grinding on hazard assessment of spontaneous fire development in the coal deposit during heating and cooling the fire source was analyzed. The intensity of desorption of ethane, ethylene, propane, propylene, acetylene, carbon monoxide and hydrogen is the resultant of temperature and grinding of coal samples. The results proved that the ratio of concentrations emitted by standard versus coarsely crushed coal for each of the gases, changed both in the growth phase as well as in the temperature drop phase. It was found that as the temperature rose, the effect of coal grinding on the release of ethane, ethylene, propane, propylene and carbon monoxide decreased. The greatest effect of coal grinding was observed in the case of ethane and propane, while the lowest in the case of hydrogen and carbon monoxide.

scholarly journals Effect of flow rates of gases flowing through a coal bed during coal heating and cooling on concentrations of gases emitted and fire hazard assessment

2019 ◽  
Vol 7 (1) ◽  
pp. 107-121 ◽  
Author(s):  
Marek Więckowski ◽  
Natalia Howaniec ◽  
Adam Smoliński
Keyword(s):  
Fire Hazard ◽  
The Self ◽  
Coal Bed ◽  
Flow Rates ◽  
Coal Beds ◽  
Heating And Cooling ◽  
Heating Phase ◽  
Two Samples ◽  
Cooling Phase ◽  
Phase Temperature

AbstractThe flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal. The assessment of fire hazard is performed on the basis of concentrations of particular gases in a mine air. These concentrations differ in coal heating and cooling phase which was proven in the study. This paper presented the results of the experimental study on temperature distribution in a simulated coal bed in heating (50–250 °C) and cooling (250–35 °C) phases as well as its correlation to variations in concentration of gases released in these phases and flow rates of gases flowing through the coal bed. The research was performed on twenty-two samples of bituminous coals acquired from various coal beds of Polish coal mines. Considerable differences were observed between heating and cooling phases in terms of the concentrations of gases taken into account in calculations of self-combustion index. In the heating phase temperature increase resulted in the decrease of concentrations ratios of ethane, ethylene, propane, propylene and acetylene, while in the cooling phase these ratios increased systemically. The effect of air (in heating phase) and nitrogen (in cooling phase) flow rate on the self-ignition index CO/CO2 was also determined.

Direct observation of three-dimensional transient temperature distribution in SiC Schottky barrier diode under operation by optical-interference contactless thermometry (OICT) imaging

2022 ◽  
Author(s):  
Keiya Fujimoto ◽  
Hiroaki Hanafusa ◽  
Takuma Sato ◽  
Seiichiro HIGASHI
Keyword(s):  
Temperature Distribution ◽  
Schottky Barrier ◽  
Hot Spot ◽  
Local Heating ◽  
Three Dimensional ◽  
Schottky Barrier Diode ◽  
Transient Temperature ◽  
Optical Interference ◽  
Transient Temperature Distribution ◽  
Heating And Cooling

Abstract We have developed optical-interference contactless thermometry (OICT) imaging technique to visualize three-dimensional transient temperature distribution in 4H-SiC Schottky barrier diode (SBD) under operation. When a 1 ms forward pulse bias was applied, clear variation of optical interference fringes induced by self-heating and cooling were observed. Thermal diffusion and optical analysis revealed three-dimensional temperature distribution with high spatial (≤ 10 μm) and temporal (≤ 100 μs) resolutions. A hot spot that signals breakdown of the SBD was successfully captured as an anormal interference, which indicated a local heating to a temperature as high as 805 K at the time of failure.

The impact of technology on architecture in Iran with focus on saving in energy consumption

2015 ◽  
Vol 16 (SE) ◽  
pp. 97-103
Author(s):  
Allah Bakhsh Kavoosi ◽  
Shahin Heidari ◽  
Hamed Mazaherian
Keyword(s):  
Energy Consumption ◽  
Energy Demand ◽  
Industrial Revolution ◽  
Demand Prediction ◽  
Interior Spaces ◽  
Heating And Cooling ◽  
Impact Of Technology ◽  
Contemporary Architecture ◽  
The Impact ◽  
The Given

Growth and development of technology caused enormous transformation and change in the world after Industrial Revolution. The contemporary human has prepared the platform for their realization in many activities that the humans were unable to do it in the past time and struck the dream of their realization in their mind so that today doing many of those activities have been apparently practical by human. This accelerating growth accompanied with consuming a lot of energy where with respect to restriction of the given existing resources, it created energy crises. On the other hand, along with growth in industry and requirement for manpower and immigration from village to city and basic architectural changes in houses, which have emerged due to change in social structure it has led to change in lifestyle and type and quantity of consuming energy in contemporary architecture. Inter alia, with increase in human’s capability, cooling and heating and acoustic and lighting technologies were also changed in architecture and using mechanical system was replaced by traditional systems. Application of modern systems, which resulted from growth of industry and development of technology and it unfortunately, caused further manipulation in nature and destruction of it by human in addition to improving capability and potential of human’s creativity. With respect to growth of population and further need for housing and tendency to the dependent heating and cooling systems to them in this article we may notice that the housing is assumed as the greatest consumer of energy to create balance among the exterior and interior spaces in line with creating welfare conditions for heating and cooling and lighting. The tables of energy demand prediction in Iran show that these costs and energy consumption will be dubbed with energy control smart management in architecture.

scholarly journals Heat Localization in the Medium in Blow-Up Regime

2020 ◽  
Keyword(s):  
Temperature Distribution ◽  
Blow Up ◽  
Maximum Temperature ◽  
Heating Regime ◽  
Heating And Cooling ◽  
Localized Heating ◽  
Finite Period ◽  
Equation Of Heat Conduction ◽  
The Given ◽  
Heat Front

The existence of the effect of heat metastable localization in the medium in the blow-up heating regime was experimentally proved. This is the regime in which the heating energy for a finite period of time tends to infinity. Previous theoretical studies have shown that in this case some regions, inside of which the temperature increases, may arise, while their size remains constant or decreases with time (heat localization regions). These regions exist as long as there is some energy input from the outside. An installation for the experimental study of the thermal blow-up regimes in a solid was developed. The object of research was an aluminum rod with a heater at its end. The temperature distribution along the rod was measured with thermocouples. The temperature of the rod end could vary according to the given law. Calibration of the installation was performed. The sensitivity of thermocouples was determined. The inertia of the heating and cooling process was estimated. The mathematical description of the thermal processes, occurring during the experiment, was made. The nonlinear equation of heat conduction for the rod was solved, with the heat exchange with the environment by convection and radiation taken into account. The thermal regime at the boundary, which is necessary to create the thermal structures, was determined. The temperature distribution in the rod in the blow-up regime and non-blow-up regime was measured. In the blow-up regime the heat front (the coordinate of the point with the temperature equal to half the maximum temperature) initially shifts from the heat source, and then in the opposite direction, and the size of the area under heating decreases. In the non-blow-up regime the size of the heated region increases all the time. The predicted effect was supposed to be used in installations for thermonuclear fusion where the target was heated by laser radiation pulses of a special shape. This effect can also be used for localized heating in cutting and welding, when the adjacent regions are not to get very hot, and in other similar situations.

Inverse Design of Cooling of Electronic Chips Subject to Specified Hot Spot Temperature and Coolant Inlet Temperature

2015 ◽  
Author(s):  
Sohail R. Reddy ◽  
George S. Dulikravich
Keyword(s):  
Heat Flux ◽  
Hot Spot ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Maximum Temperature ◽  
Fluid Temperature ◽  
Cooling Fluid ◽  
Pin Fin ◽  
The Given

Most methods for designing electronics cooling schemes do not offer the information on what levels of heat fluxes are maximally possible to achieve with the given material, boundary and operating conditions. Here, we offer an answer to this inverse problem posed by the question below. Given a micro pin-fin array cooling with these constraints: - given maximum allowable temperature of the material, - given inlet cooling fluid temperature, - given total pressure loss (pumping power affordable), and - given overall thickness of the entire electronic component, find out the maximum possible average heat flux on the hot surface and find the maximum possible heat flux at the hot spot under the condition that the entire amount of the inputted heat is completely removed by the cooling fluid. This problem was solved using multi-objective constrained optimization and metamodeling for an array of micro pin-fins with circular, airfoil and symmetric convex cross sections that is removing all the heat inputted via uniform background heat flux and by a hot spot. The goal of this effort was to identify a cooling pin-fin shape and scheme that is able to push the maximum allowable heat flux as high as possible without the maximum temperature exceeding the specified limit for the given material. Conjugate heat transfer analysis was performed on each of the randomly created candidate configurations. Response surfaces based on Radial Basis Functions were coupled with a genetic algorithm to arrive at a Pareto frontier of best trade-off solutions. The Pareto optimized configuration indicates the maximum physically possible heat fluxes for specified material and constraints.

Experimental Study on Dynamic Elastic Properties of Gas Hydrate Bearing Sediments

2012 ◽  
Vol 446-449 ◽  
pp. 1396-1399
Author(s):  
Ling Dong Li ◽  
Yuan Fang Cheng ◽  
Xiao Jie Sun
Keyword(s):  
Elastic Properties ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Hot Spot ◽  
Confining Pressure ◽  
Measuring System ◽  
Fundamental Parameters ◽  
Hydrate Saturation ◽  
Hydrate Bearing Sediments

As a kind of emerging energy with massive reserves, natural gas hydrates are becoming the hot spot of global research. The elastic properties of gas hydrate bearing sediments (HBS) are the fundamental parameters for gas hydrates exploration and resource evaluations. As the original coring in HBS is difficult and expensive, experimental method is important to study the problem. An acoustic wave in-situ measuring system for HBS was developed. Using the in-situ method, hydrate bearing rock samples of different hydrate saturation were synthesized, of which the supersonic wave measurement was carried out under different confining pressure. According to the elasticity theory, the dynamic elastic parameters were obtained using the measured ultrasonic wave velocity. The results show that compressional and shear waves increase with the confining pressure and hydrate saturation increasing, and so the dynamic elastic modulus is.

scholarly journals Preliminary results of tests on nitrogen cushion for combating fire hazard in longwalls rich in methane

2020 ◽  
Vol 174 ◽  
pp. 01066
Author(s):  
Dawid Szurgacz ◽  
Leszek Sobik ◽  
Jarosław Brodny ◽  
Maxim Grigashkin
Keyword(s):  
Fire Hazard ◽  
Main Idea ◽  
Extraction Process ◽  
Coal Extraction ◽  
Hard Coal ◽  
High Tendency ◽  
Preventive Actions ◽  
Wide Range ◽  
Endogenous Fire ◽  
Roof Support

Ventilation hazard is the most dangerous phenomena occurring in the hard coal extraction process. This particularly applies to endogenous fire hazard. In order to reduce it, it is necessary to improve the effectiveness of preventive measures. Hence this paper presents new solutions that substantially improve fire prevention effectiveness. The main idea is to develop and create an additional nitrogen cushion in the zone behind the powered roof support operating in a longwall face. The solution is based on installations for inerting of goafs and sections of the powered roof support. The nitrogen cushion restricts the access of air and oxygen to the area of goafs and limits the possibility of fire. Practical application of the developed solution allowed for effective reduction of fire hazard in conditions of a very high tendency of coal to self-ignite at short incubation period. This, in turn, enables safe exploitation and decommissioning of the longwall. Undoubtedly, the solution presented and the results obtained constitute a new approach to preventive actions in mines. It is the result of the work of theoretical and practical researchers. The solution is a combination of the potential of these two environments. The developed solution should find wide range of applications in the areas where endogenous fire and methane hazards occur.

Numerical Calculation of Dry-Type Transformer and Temperature Rise Analysis

2013 ◽  
Vol 753-755 ◽  
pp. 1025-1030 ◽  
Author(s):  
Chao Lu ◽  
Hui Gang Sun ◽  
Qing Zheng ◽  
Yi Ren Liu ◽  
Jian Sheng Chen
Keyword(s):  
Boundary Condition ◽  
Temperature Rise ◽  
Fire Hazard ◽  
Hot Spot ◽  
Original Data ◽  
Key Factors ◽  
Convection Model ◽  
Electro Magnetic ◽  
Winding Insulation ◽  
Prototype Design

Comparing to oil transformer, the dry-type transformer minimizes explosion and fire hazard, as well as long product life. Meanwhile winding insulation plays an important role in the reliability, yet winding temperature rise may cause deterioration to the insulation. So it is critical to have temperature rise analysis for hot spot and prediction in the period of prototype design using finite element method, such as CFD. The key factors like completed boundary condition and coupling of electro-magnetic with thermal fluid will be obtained from experiment which could provide more accurate heat transfer coefficient for new design. Relative to method of thermal network, CFD has provided more accurate air convection model and different boundary condition definition, thus it could be an original data for other serial product simulation.

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