Influence of the building energy efficiency on indoor air temperature: The case of a typical school classroom in Serbia

Greenhouse gases emission as well as total energy consumption in buildings of public importance, such as schools, municipal buildings, health care centers, can be significantly reduced by increasing buildings’ energy efficiency. Buildings’ energy consumption adds up to 37% of total energy consumption in the EU countries. In the Republic of Serbia this amount is significantly higher, about 50%. School buildings are considered as one of the most diverse structures from the point of energy-efficient design and construction. The main aim of this paper is to determine the most appropriate settings for possible improvements in energy efficiency and temperature comfort inside a typical primary school classroom in Serbia. The energy efficiency analysis was performed during the heating season for the naturally ventilated primary school classroom located in the eastern Serbia region. The analysis was performed using novel CFD model, suggested in this paper. The suggested model was used to solve two hypothetical scenarios. The first scenario simulates the temperature field in classroom with current energy characteristic envelope of the school building. The calculated numerical data from the first scenario were compared with in-situ measurements values of temperature and wall heat fluxes and showed satisfying accuracy. The second scenario was simulated to indicate possible improvements, which would allow energy consumption decrease and thermal quality enhancement. The analyzed results, calculated using the suggested numerical model under the second scenario conditions, showed that using appropriate set of measures, it is possible to obtain desired temperature comfort levels without need for increase in the building energy consumption

Modeliranje turbulentnog dvofaznog toka aero-smeše sprašenog uglja u gorioničkim kanalima sa jednostepenim turbulatorima

The subject of this work is turbulent two-phase flow through air-coal channel(s) of complex geometry. The aim of this work is numerical optimization of fluid flow and coal particle distribution in reconstructed air-coal mixture channels. The single blade turbulator has been used to increase turbulence in the vertical section of an air-coal mixture channel. Standard k-ω turbulent model has been used for modeling turbulence. Lagrangian multiphase model has been used for discrete phase (coal particles) modeling. Although better particle distribution is reached using single blade turbulators, particle concentration in the evaluation section (where plasma generators will be built in) still remains anisotropic. Because uniform coal particle distribution is of great importance for the proper work of plasma generators, other solutions for achieving this goal will be the object of the future analysis.Predmet ovog rada je turbulentno dvofazno strujanje kroz gorioničke kanale aero-smeše sprašenog uglja kompleksne geometrije. Cilj ovog rada je numerička optimizacija strujnog toka i raspodele čestica sprašenog uglja u rekonstruisanim gorioničkim kanalima. Za povećanje turbulencije, u vertikalnom delu gorioničkog kanala aero smeše ugrađen je jednostepeni turbulator. Za modeliranje turbulencije korišćen je standardni k-ω turbulentni model. Lagranžeov pristup je korišćen za modeliranje sekundarne faze (čestica sprašenog uglja). Iako je upotrebom jednostepenih turbulatora postignuta bolja raspodela čestica sprašenog uglja, koncentracija čestica u prelaznom delu (u kome će biti ugrađeni plazma generatori) ostaje neravnomerna. Kako je ravnomerna raspodela čestica sprašenog uglja od esencijalnog značaja za pravilan rad plazma generatora, druga rešenja za postizanje ravnomerne raspodele čestica će biti predmet buduće analize

Experimental and numerical investigation of thermal and flow conditions inside a large pharmaceutical storage after the ventilation system failure

Safe storage of pharmaceutical products is of great importance due to potential hazards for human health. The aim of this study was to assess the ability of pharmaceutical storage to recover design temperature during ventilation system recovery. The performed CFD simulations showed good agreement with experimental temperature measurements. Numerical results allowed in-depth analysis of flow field and temperature distribution inside the storage. It was discovered that the flow field is highly non-uniform, which consequently leads to an uneven temperature distribution of pallets with products. However, a high inlet mass-flow rate ensured that all pallets reach the designed temperature

Novel Fragmentation Model for Pulverized Coal Particles Gasification in Low Temperature Air Thermal Plasma

New system for start-up and flame support based on coal gasification by low temperature air thermal plasma is planned to supplement current heavy oil system in Serbian thermal power plants in order to decrease air pollutions emission and operational costs. Locally introduced plasma thermal energy heats up and ignites entrained coal particles, thus starting chain process which releases heat energy from gasified coal particles inside burner channel. Important stages during particle combustion, such as particle devolatilisation and char combustion, are described with satisfying accuracy in existing commercial computer fluid dynamics codes that are extensively used as powerful tool for pulverized coal combustion and gasification modeling. However, during plasma coal gasification, high plasma temperature induces strong thermal stresses inside interacting coal particles. These stresses lead to thermal shock and extensive particle fragmentation during which coal particles with initial size of 50-100 mu m disintegrate into fragments of at most 5-10 mu m. This intensifies volatile release by a factor 3-4 and substantially accelerates the oxidation of combustible matter. Particle fragmentation, due to its small size and thus limited influence on combustion process is commonly neglected in modelling. The main focus of this work is to suggest novel approach to pulverized coal gasification under high temperature conditions and to implement it into commercial comprehensive code ANSYS FLUENT 14.0. Proposed model was validated against experimental data obtained in newly built pilot scale direct current plasma burner test facility. Newly developed model showed very good agreement with experimental results with relative error less than 10%, while the standard built-in gasification model had error up to 25%

Results of the modernization of the electrostatic precipitator at unit B1 of the Thermal Power Plant Kostolac B

The electrostatic precipitator system of the lignite fired 350 MWe unit B1 of Thermal Power Plant Kostolac B has been modernized during 2014. The results of complex in site measurements, performed in the frame of performance control test at the beginning of the exploitation period of the upgraded electrostatic pre-cipitator proved that, under normal and guarantee working conditions of the boiler and precipitator, the emission of particulate matter do not exceed limiting value. After the period of precipitator further adjustments, five series of meas-urements in the frame of acceptance test were performed in accordance with rel-evant standards. This paper presents results of the investigation of particulate matter concentration, laboratory analysis of the lignite, fly and bottom ash sam-ples, working parameters of the unit and upgraded electrostatic precipitator as well as results of the calculations. The averaged mean particulate concentration at the exit of upgraded electrostatic precipitator of the unit B1 during Acceptance test was below guaranteed value. It is confirmed that adjustments of electrostatic precipitator electrical parameters have improved electrostatic precipitator effi-ciency, as well that electrostatic precipitatorcould work highly efficiently in en-ergy save mode with lower power consumption. © 2018 Society of Thermal Engineers of Serbia

Percolation theory applied in modelling of Fe2O3 reduction during chemical looping combustion

The study presents a new modelling approach applied to hematite to magnetite reduction, which is the dominant reaction in atmospheres with a high CO2/CO ratio, expected in chemical looping combustion. The structure of the Fe2O3 particle was simulated using the percolation theory, while the reduction was modelled using the stochastic approach to simulate nucleation, gaseous diffusion, solid-state diffusion, and chemical reaction. To account for differences between 3-D and 2-D pores, the model allowed for pore-hopping. The obtained results agreed with experimental results for Fe2O3 derived from natural ore (pyrite), and, to a lesser extent, with results for lab-synthesised Fe2O3 particles. The model provides useful insight into the complexity of the investigated process. For materials with undeveloped porosity, a simple shrinking-core approximation will be sufficient. In contrast, for materials with well-developed porosity, the models should incorporate information about the particle structure. © 2020 Elsevier B.V

Probabilistic Simulation of Incremental Lifetime Cancer Risk of Children and Adults Exposed to the Polycyclic Aromatic Hydrocarbons – PAHs in Primary School Environment in Serbia, Model Development and Validation

Polycyclic aromatic hydrocarbons (PAHs) are considered to be major air pollutants with a strong negative influence on human health. Many of them are toxic with high carcinogenic potential. Children and school staff spend a significant portion of daytime at schools, mostly indoors. Therefore, the hypothesis can be made that air quality significantly impacts their health. A health risk assessment, performed by calculating Incremental lifetime cancer risk (ILCR), was conducted in the framework of this study. Indoor and outdoor PAHs concentrations were measured in typical Serbian primary school. Total suspended particles (TSP) and gas-phase PAHs from the air were collected both inside the school building and in the outside school environment. Average indoor and outdoor PAHs concentrations were used to calculate benzo[a]pyrene equivalent (BaPeq) concentration. A significantly higher BaPeq was observed in the gas-phase than in the TSP, due to a high amount of low molecular PAHs present in the gas-phase. The measured BaPeq concentration values were fitted to the appropriate mathematical distribution and used as an input parameter for stochastic ILCR modeling. Different body weight and inhalation rate distributions were used for sampling during ILCR calculations. The performed sensitivity analysis showed that the two different recommended values of cancer slope factor had a major impact on the ILCR values. Based on this, it was decided to perform simulations using cancer slope factors for individual PAHs. The obtained ILCR values for both children and adults were greater than the allowed level, indicating high potential lung cancer risk. It may be concluded that it is necessary to improve indoor air quality in schools applying measures for lowering TSP PAHs with high carcinogenic potential. © Springer Nature Switzerland AG 2020.In: Mitrovic N., Milosevic M., Mladenovic G. (eds) Computational and Experimental Approaches in Materials Science and Engineering. CNNTech 2018. Lecture Notes in Networks and Systems, vol 90. Springer, Cha

Sensitivity analysis of different devolatilisation models on predicting ignition point position during pulverized coal combustion in O-2/N-2 and O-2/CO2 atmospheres

Oxy-fuel combustion is considered as a promising solution to reduce greenhouse-gases and pollutant emissions. The main advantage of oxy-fuel combustion over other technologies for pollution reduction from pulverized coal combustion is that it can be applied to the existing coal-fired power plants. However, switching from conventional to oxy-fired coal combustion brings significant challenges. One of the most important is change of pulverized coal ignition characteristics. This paper presents the results of experimental and numerical analysis of ignition phenomena under oxy-fuel conditions. The main focus of the presented paper is to evaluate the effectiveness of the mathematical devolatilisation sub-model, in predicting the ignition point of pulverized coal flames under oxy-firing conditions. Regarding this, the performance of several devolatilisation models, from simple to more complex ones, in predicting ignition point position have been investigated. Numerically determined values of the ignition point position, and ignition temperature for various O-2-N-2 and O-2-CO2 conditions were compared with experimental data from the laboratory ignition test facility. Obtained results pointed out that network devolatilisation models (CPD and FG) give more accurate results in comparison with standard devolatilisation models (single rate and two competing rates). The best performance is achieved using FG devolatilisation model. Thus, newly implemented FG model will be used for future numerical simulations of oxy-fuel pulverized coal combustion on 0.5 MW pilot plant facility. (C) 2011 Elsevier Ltd. All rights reserved.8th European conference on coal research and its applications, Sep 06-10, 2010, Leeds, Englan

Sensitivity analysis of different kinetic factors for numerical modeling of Serbian lignite devolatilization process

Numerical modeling is widely used tool for prediction of combustion processes. Computational Fluid Dynamics - CFD models use three kinetic rates for description of the coal combustion processes: coal devolatilization, volatile combustion and char combustion. Reported rates for coal devolatilization vary considerably among the authors depending on the type of experimental systems used in describing the phenomenon. Accurate representation of devolatilization process is necessary in order to perform successful CFD calculations of pulverized coal combustion and gasification. The subject of this work is numerical modeling of Serbian lignite pulverized coal devolatilization in drop tube type laboratory scale reactor. The aim of this study is to evaluate the influence of different devolatilization kinetic factors on total devolatilization time in numerical modeling of pulverized Serbian lignite devolatilization. Nine different devolatilization kinetic rates mostly used in devolatilization numerical modeling are compared in the presented work. (c) 2014 Elsevier Ltd. All rights reserved