Papers by Keyword: Air

Abstract: One of the basic measures of energy efficiency in residential buildings is the reduction of heat and coolant pressure, when external structures - walls, ceilings - contain thermal insulation material, as a result of which heat and cold losses are reduced, as a result of air-and moisture permeability. Their number is largely determined by the climatic zone of the building, construction, sources of heat and cold, fuel and electricity prices in this region. In such practice, first of all, attention is paid to the problems of the optimal thickness of the thermal insulator, the installation location, since improper installation in the structure can cause water condensation, which will lead to partial wear of the structure, since the properties of reinforced-concrete layers will deteriorate. This concerns the peculiarities of carrying out thermal insulation works and their necessity both in under construction and in buildings in use. However, even in these conditions, when discussing the thermal effect of thermal insulation on structures, due attention is not paid to individual structures, especially walls, moisture problems. Consideration of insulators with more or less efficient energy and heat engineering characteristics, when it was found that there is a significant difference between their results and effects, aroused particular interest in the study of the problem. This is followed by a study of the influence of the presence of thermal insulation in the structure on the cold load required for cooling, revealed a pattern of cost changes in the case of insulating materials with more or less properties - foam.

Abstract: Carbon-free electrosynthesis of ammonia using water (H₂ source) and air (N₂ source) is promising technology to reduce the global CO₂ emission resulting from the industrial ammonia production process (Haber-Bosch). In this study, electrocatalysis activity of non-noble metal perovskite-based catalyst (La_0.75Sr_0.25Cr_0.5Fe_0.5O_3-δ-Ce_0.8Gd_0.18Ca_0.02O_2-δ, LSCrF-CGDC) for ammonia synthesis directly from air and water was explored. Ammonia was successfully from wet air (3%H₂O) synthesized in a single-chamber type reactor. The highest ammonia formation rate and Faradaic efficiency of about 1.94×10^-11 mol s^-1 cm^-2 and 2.01% were achieved at 375 oC and 1.2 V, respectively. The observed ammonia formation rate is higher than reported for an expensive noble metal-based catalyst (Ru/MgO). The obtained results indicated that the direct synthesis of ammonia from air and water is a promising technology for green and sustainable ammonia synthesis.

Abstract: Kinetics of the siderite ore roasting in the air, helium and hydrogen flows has been studied in a gasometrical unit with continuous mass variation logging. We have derived the expression for determination of an apparent degree of calcination and identified its dependence on the size of the prill, the heat treatment duration, and gas-phase composition. Using a generalized chemical kinetics equation, we have obtained a formula for calculation of the decomposition period for siderite ore samples. It has been found that calcination rate increases with the temperature rise, irrespective of the sample size and atmospheric composition. Calcination process has been studied at low temperatures. We have demonstrated that it is feasible to describe the process of siderite ore thermal dissociation by a first-order kinetics equation. We have obtained the expression to calculate the duration of this process depending on different parameters. Using a generalized chemical kinetics equation, we have obtained a formula for checking the expressions that describe the experimental data. We have studied kinetics of the reduction of roasted ore samples at various temperatures using different sizes of the samples. The obtained results have been applied for optimization of the design values and operating conditions of the siderite ore roasting in shaft furnaces. These will also be used for designing a shaft furnace consisting of a calcination zone, reduction zone (metallization zone) and metallized product cooling zone, which will increase iron content in the end-product to 65-70%.

Abstract: Everyday there are about 7 million passengers commuting by subway in Shanghai, China. Although Shanghai has one of the largest subway networks in the world, yet this subway system is still full of passengers during the rush hours. Extracting air and smoke is important part of the station ventilation system which supplies enough fresh air in the crowded station. As we know, the underground subway stations are built in an enclosed space where needs air circulation far more than other type of station. This paper focuses on the designs of duct layout and valve control in an underground subway station. The authors give three solutions to return air and exhaust smoke in the underground station platform area and entrance area. The goal of this paper is to compare these three ventilation solutions in the normal time and in the fire accident. The result of analyzing and applying these solutions are concluded in the paper.

Abstract: Vehicle transportation is now an important part of our civilization and as it happened with much other technological advancement, the negative aspects are becoming more and more pronounced. One of them is air pollution from vehicles exhaust gases. This pollution has many adverse effects, whose manifestation and character varies depending on the geographical scale in consideration. The relative contribution of different combustion sources is a function of economic, social and technological factors, but all mixtures contain certain primary gaseous pollutants, such as volatile organic compounds (VOC), nitrogen oxides (NO_x) and carbon monoxide (CO), that are emitted directly from combustion sources, as well as secondary pollutants, such as ozone (O₃), that are formed in the atmosphere from directly emitted pollutants. The elevated concentrations generally occur with in a few hundred meters of the road, although his distance may vary depending on traffic patterns, environmental conditions, and the presence of near roadway urban structures. For the realized study it was choose a route from the historical centre of the Brasov City. In this study is presented the methodology for a prediction model for urban air pollution.

Abstract: The problem of cavitation is highly discussed and published phenomenon not only in a negative sense, but in the positive use also. In hydraulic systems the cavitation is undesirable phenomena specific by cavitation wear and noise. These systems operate at ever-increasing operating conditions (pressure and flow). For this reason, this phenomenon occurs in many technical applications. The problem cavitation is very large, so it is necessary to define the area of scientific interest. Currently, there is an increasing interest in the fields of mathematical and experimental research in hydraulic elements and systems engineering practice. The paper is focused on modelling of shape of cavitation area and influence of air content primarily on the simple geometry of plane nozzle, where the water is flowing.

Abstract: The 23 air samples were collected from Tianjin Dongli industrial zone from July 2010 to May 2011 for the analysis of 84 PCB congeners to investigate the gas/particle partitioning. The total PCBs concentration ranged from 71.08 to 567.36 pg m^-3 with the mean value as 307.78±137.45 pg m^-3 and the seasonal trends were summer >winter >spring >autumn. Gas PCBs accounted for 77.47% of the total PCBs. The fraction of each gas PCB homolog increased with the decreasing chlorine atoms. The contribution of gas PCBs to total PCBs showed a strong seasonal variation with summer (92.44%)> autumn (85.16%) > spring (80.61%) > winter (42.70%). Tri-, tetra-, penta-PCBs and di-PCBs were the predominantly homologs in atmosphere from industrial zone in Tianjin. The natural logarithm of partial pressure of PCBs were well correlated with the inverse absolute environmental temperature (R=0.77). The steep slope of-3764 obtained from Clausius–Clapeyron plot indicated the influence of local PCBs sources.

Abstract: The air quality in the classrooms of primary schools is an issue that is high on the agenda. They are devoted to the study and Europe. They show a wide variation in air requirements by occupancy class. During weekends and holidays, it is not necessary to meet the health requirements for air taking into account the presence of students. It is possible to specify boundary conditions, which influenced thermal requirements for building envelopes, by finding and setting various intensities of air exchange, depending on the occupation and function of the building. This fact should result to improving of the energy efficiency of primary school buildings and reducing of operating energy costs.

Abstract: Based on the characteristics and special function of gymnasiums, this thesis made a comprehensive assessment on mode selection of air distribution in gymnasiums by proposing that air distribution in gymnasiums be totally evaluated from the standpoints of degree of satisfaction in auditoriums and playing areas, improved air exchange efficiency and improved afterheat elimination efficiency. The thesis made a general conclusion of evaluation system of air distribution established by domestic researchers on gymnasiums, hoping to make contributions to the gymnasium undertaking of our country.

Abstract: MWCNTs was purified by air treatment. When MWCNTs are treated in air at 350 °C for 4 h, the initial decomposition temperature of MWCNTs is the highest. The result can also be verified by the contrast of SEM photographs of untreated and treated MWCNTs.