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1
Chaczykowski, Maciej. "Organic Rankine Cycle for Residual Heat to Power Conversion in Natural Gas Compressor Station. Part II: Plant Simulation and Optimisation Study." Archives of Mining Sciences 61, no. 2 (June 1, 2016): 259–74. http://dx.doi.org/10.1515/amsc-2016-0019.
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Abstract After having described the models for the organic Rankine cycle (ORC) equipment in the first part of this paper, this second part provides an example that demonstrates the performance of different ORC systems in the energy recovery application in a gas compressor station. The application shows certain specific characteristics, i.e. relatively large scale of the system, high exhaust gas temperature, low ambient temperature operation, and incorporation of an air-cooled condenser, as an effect of the localization in a compressor station plant. Screening of 17 organic fluids, mostly alkanes, was carried out and resulted in a selection of best performing fluids for each cycle configuration, among which benzene, acetone and heptane showed highest energy recovery potential in supercritical cycles, while benzene, toluene and cyclohexane in subcritical cycles. Calculation results indicate that a maximum of 10.4 MW of shaft power can be obtained from the exhaust gases of a 25 MW compressor driver by the use of benzene as a working fluid in the supercritical cycle with heat recuperation. In relation to the particular transmission system analysed in the study, it appears that the regenerative subcritical cycle with toluene as a working fluid presents the best thermodynamic characteristics, however, require some attention insofar as operational conditions are concerned.
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Ren, Qian, Yao, Gan, and Zhang. "Thermodynamic Evaluation of LiCl-H2O and LiBr-H2O Absorption Refrigeration Systems Based on a Novel Model and Algorithm." Energies 12, no. 15 (August 6, 2019): 3037. http://dx.doi.org/10.3390/en12153037.
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An absorption refrigeration system (ARS) is an alternative to the conventional mechanical compression system for cold production. This study developed a novel calculation model using the Matlab language for the thermodynamic analysis of ARS. It was found to be reliable in LiCl-H2O and LiBr-H2O ARS simulations and the parametric study was performed in detail. Moreover, two 50 kW water-cooled single effect absorption chillers were simply designed to analyze their off-design behaviors. The results indicate that LiCl-H2O ARS had a higher coefficient of performance (COP) and exergetic efficiency, particularly in the lower generator or higher condenser temperature conditions, but it operated more restrictively due to crystallization. The off-design analyses revealed that the preponderant performance of LiCl-H2O ARS was mainly due to its better solution properties because the temperature of each component was almost the same for both chillers in the operation. The optimum inlet temperature of hot water for LiCl-H2O (83 °C) was lower than that of LiBr-H2O (98 °C). The cooling water inlet temperature should be controlled within 41 °C, otherwise the performances are discounted heavily. The COP and cooling capacity could be improved by increasing the temperature of hot water or chilled water properly, contrary to the exergetic efficiency.
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BOUSHABA, Hicham, Abdelaziz MIMET, and Mohammed El GANAOUI. "Prototype’s seizing and design of a solar refrigerator based on solid adsorption." MATEC Web of Conferences 307 (2020): 01013. http://dx.doi.org/10.1051/matecconf/202030701013.
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Solar refrigerator machines based on solid adsorption present a highly interesting solution to the Industry of Cooling Production. In one hand, they are significantly attractive economy ways because of the abundance of the solar energy resources. In the other hand, they are environment friendly. As a result, these machines could present one of the most competitive solutions to the improvement of this very industry. The aim of this paperwork is to provide an accurate study on how to design, seize and build a prototype of an adsorption solar refrigerator using activated-carbon/ammonia pair: Firstly, we used a static model, which is based on the use of state equations (vapor/liquid) at thermodynamic equilibrium. This model computes the cycled mass and the cycle coefficient of performance (COPc) for each four characteristic temperatures of the cycle. Secondly, we develop a dynamic simulation program based on conservation equations of energy and mass in the reactor, this program allow the calculation of the temperature, the pressure inside the reactor, the adsorbed mass and the solar coefficient of performance (COPs). Finally, in the light of our results, we design this prototype, it would consist of the reactor: a solar panel, size 1 m2contain tubes with a diameter of 10cm, an air condenser, and a cold chamber containing an air evaporator.
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Poullikkas, Andreas, Ioannis Hadjipaschalis, and George Kourtis. "Comparative Assessment of an Innovative Dry-Cooled CSP System." Conference Papers in Energy 2013 (May 28, 2013): 1–10. http://dx.doi.org/10.1155/2013/849407.
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A comparative optimization assessment is carried out in order to identify the competitiveness of an innovative modular air-cooled condenser (MACC) system in relation to conventional water- or air-cooled condensers. Specifically, the technoeconomic performance of the combined cycle gas turbine (CCGT) technology, the parabolic trough concentrated solar power (CSP) technology, and the solar tower CSP technology are compared when all are integrated (a) with a MACC condenser of an optimum tube geometry and size, (b) with a conventional water-cooled condenser, and (c) with a conventional dry-cooled condenser. The comparison is performed across three different solar potential levels. The simulations are carried out using an optimization model based on the IPP v2.1 algorithm for the calculation of the electricity unit cost and other financial indicators of each technology under investigation. The results demonstrate that, under certain parameters, the investigated MACC condenser system can become a cost-competitive alternative to water- or dry-cooled condensers in various solar potential environments.
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Ni, Weiming, Zhihua Ge, Lijun Yang, and Xiaoze Du. "Piping-Main Scheme for Condensers against the Adverse Impact of Environmental Conditions on Air-Cooled Thermal Power Units." Energies 13, no. 1 (December 30, 2019): 170. http://dx.doi.org/10.3390/en13010170.
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To improve the adaptability of direct air-cooled power generating units to the variations of both meteorological condition and power load, a piping-main arrangement of air-cooled condensers was proposed. The heat and mass transfer models of the air-side were established for the air cooling system of 2 × 600 MW thermal power generating units. The coupled model for both flow resistance loss and condensate flow rate distributions of exhaust steam inside air-cooled condensers were developed based on the temperature fields through numerical simulation. Calculation results, including the condensate flow rate, back pressure, and coal consumption rate, were acquired under different ambient temperatures and wind velocities. The results show that the proposed piping-main arrangement can weaken the ambient wind impacts and reduce the backpressure significantly in summer by adjusting the number of air-cooled condenser cells in operation. The steam flow rate can be uniformed effectively by adjusting the number of operating air-cooled condenser cells during winter. It can also avoid the freezing accident in winter while cooling the exhaust steam of two turbines by part air-cooled condenser cells.
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Cong, Jiang, and Yu Hui. "Research on the Thermo-Economics Calculation Model for Indirect Air-Cooled System." Advanced Materials Research 953-954 (June 2014): 876–79. http://dx.doi.org/10.4028/www.scientific.net/amr.953-954.876.
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Based on the research about the part load operation calculation model of condenser pressure and theoretical scrupulous induction,this paper provides the calculation model about the influence parameters of cold end system for thermo-economics in Hailler indirect air-cooled system,and it can provide a strong theoretical basis for improving the performance of Hailler cold end system.
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Lv, Yi, Hui Zhang, Yu Jin Yue, Li Jun Yang, and Xiao Dong Zhang. "Deviation Analysis on Flow and Heat Transfer Model of Large Air-Cooled Steam Condenser Unit." Advanced Materials Research 860-863 (December 2013): 656–62. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.656.
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Many power plants adopt air-cooled condensers (ACC) with finned tubes, using ambient air to condense turbine exhaust steam. Each condenser unit is mainly composed of two heat transfer surfaces like A and large diameter axial flow fans driving air. In the study of environmental wind effects, etc, due to the condenser unit size is bigger, it is necessary to simplify the condenser unit internal flow and heat transfer calculation, but the deviations introduced by these simplifies failed to get enough attention. In view of one condenser unit, three kinds of flow and heat tansfer combinated model were respectively investigated. A computational fluid dynamics software (CFD) is used to solve the problem.Research priority is analyzing the deviations of internal flow and heat transfer features in the condenser unit according to the extracted datum. The study gives some useful informatin to the design of a thermal power plant with an ACC system.
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Keshvarparast, Adele, Seyed Soheil Mousavi Ajarostaghi, and Mojtaba Aghajani Delavar. "Thermodynamic analysis the performance of hybrid solar-geothermal power plant equipped with air-cooled condenser." Applied Thermal Engineering 172 (May 2020): 115160. http://dx.doi.org/10.1016/j.applthermaleng.2020.115160.
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Zhou, Dong Yi, and Chu Ping Shi. "Design of Multi-Function Refrigerator with Refrigeration and Constant Temperature and Hot Water." Advanced Materials Research 860-863 (December 2013): 1670–73. http://dx.doi.org/10.4028/www.scientific.net/amr.860-863.1670.
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A new model of the refrigerator with refrigeration and constant temperature and hot water has been trial-produced. The new refrigerator can not only keep refrigerated food quality, but also be used for heating or keeping food temperature constant, and supply hot water for us. The subsystems of condenser have been analyzed and designed including air-cooled method and water-cooled method. According to the theoretical calculation, the temperature in constant temperature box can keep about 50°C and 18.46 Kg hot water can be provided per hour.
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Ghettini, Simone, Alessandro Sorce, and Roberto Sacile. "Data-Driven Air-Cooled Condenser Performance Assessment: Model and Input Variable Selection Comparison." E3S Web of Conferences 197 (2020): 10003. http://dx.doi.org/10.1051/e3sconf/202019710003.
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This paper presents a data–driven model for the estimation of the performance of an aircooled steam condenser (ACC) with the aim to develop an efficient online monitoring, summarized by the condenser pressure (or vacuum) as Key Performance Indicator. The estimation of the ACC performance model was based on different dataset from three different combined cycle power plants with a gross power of above 380 MWe each, focusing on stationary condition of the steam turbine. The datasets include both boundary (e.g. Ambient Temperature, Wind Speed) and operative parameters (e.g. steam mass flow rate, Steam turbine power, electrical load of the ACC fans) acquired from the power plants and some derived variable as the incondensable fraction, which calculation is here proposed as additional parameter. After a preliminary sensitivity analysis on data correlation, the paper focuses on the evaluation of different ACC Condenser models: Semi-Empirical model is described trough curves typically based on steam mass flow rate (or condenser load) and the ambient temperature as main parameters. Since monitoring based on ACC design curves Semi-Empirical models, provides biased poor results, with an error of about 15%, the curves parameters were estimated basing on training data set. Other two data driven models were presented, basing on a neural network modelling and multi linear regression technique and compared on the base of the reduced number of input at first and then including aldo the other process variables in the prediction of the condenser back pressure. Estimate the parameters of the Semi-Empirical model, results in a better prediction if just steam mass flow rate and ambient temperature are available, with an error of the 7%, thanks to the knowledge contained within the “curves shapes”, with respect to linear regression (8.3%) and Neural Network models (7.6%). Higher accuracy can be then obtained by considering a larger number of operative parameters and exploiting more complex data-driven model. With a higher number of features, the neural network model has proved a higher accuracy than the linear regression model. In fact, the mean percentage error of the NN model (2.6%), in all plant operating conditions, is slightly lower than the error of the linear regression model, but presents and much lower than the mean error of the Semi-Empirical model thanks to the additional data-based knowledge.
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Bourouis, M., M. Vallès, M. Medrano, and A. Coronas. "Performance of air-cooled absorption air-conditioning systems working with water-(LiBr + Lil + LiNO3 + LiCl)." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 219, no. 2 (May 1, 2005): 205–13. http://dx.doi.org/10.1243/095440805x8601.
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The potential of the fluid mixture water-(LiBr + Lil+ LiNO3 +LiCl) (5:1:1:2 molar) is studied for air-cooled absorption air-conditioning systems. This multicomponent system shows a considerably higher solubility than that of water-LiBr and is also less corrosive. It is, therefore, one of the potential alternatives to replace water-LiBr in future air-cooled absorption chillers. A comparative study based on thermodynamic simulation of the single-and double-effect cycles with water-LiBr and the new fluid mixture is first reported. Once the operating conditions were established in terms of temperature and concentration in the generator and the absorber, the absorption process of a falling film flowing on the inner surface of a vertical tube at typical air cooling thermal operating conditions of the absorber was modelled in order to compare the absorption rates of the multicomponent salt mixture with those of water-LiBr. This study was completed by an experimental characterization of the absorption process in a vertical falling film tube. The results show that the multicomponent salt solution is more suitable than water-LiBr if the temperatures in the generator and absorber/condenser are low and high, respectively. Therefore this new working fluid can be recommended for air-cooled absorption air-conditioning systems driven by low temperature heat sources.
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Martinez-Frias, Joel, Salvador M. Aceves, J. Ray Smith, and Harry Brandt. "Thermodynamic Analysis of Zero-Atmospheric Emissions Power Plant." Journal of Engineering for Gas Turbines and Power 126, no. 1 (January 1, 2004): 2–8. http://dx.doi.org/10.1115/1.1635399.
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This paper presents a theoretical thermodynamic analysis of a zero-atmospheric emissions power plant. In this power plant, methane is combusted with oxygen in a gas generator to produce the working fluid for the turbines. The combustion produces a gas mixture composed of steam and carbon dioxide. These gases drive multiple turbines to produce electricity. The turbine discharge gases pass to a condenser where water is captured. A stream of pure carbon dioxide then results that can be used for enhanced oil recovery or for sequestration. The analysis considers a complete power plant layout, including an air separation unit, compressors and intercoolers for oxygen and methane compression, a gas generator, three steam turbines, a reheater, two preheaters, a condenser, and a pumping system to pump the carbon dioxide to the pressure required for sequestration. This analysis is based on a 400 MW electric power generating plant that uses turbines that are currently under development by a U.S. turbine manufacturer. The high-pressure turbine operates at a temperature of 1089 K (1500°F) with uncooled blades, the intermediate-pressure turbine operates at 1478 K (2200°F) with cooled blades and the low-pressure turbine operates at 998 K (1336°F). The power plant has a net thermal efficiency of 46.5%. This efficiency is based on the lower heating value of methane, and includes the energy necessary for air separation and for carbon dioxide separation and sequestration.
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Moore, J., R. Grimes, E. Walsh, and A. O'Donovan. "Modelling the thermodynamic performance of a concentrated solar power plant with a novel modular air-cooled condenser." Energy 69 (May 2014): 378–91. http://dx.doi.org/10.1016/j.energy.2014.03.028.
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Njoku, Ifeanyi Henry, Chika Oko, and Joseph Ofodu. "Performance Analysis of a Combined Cycle Power Plant with Simultaneous Cooling of Inlet Air Streams to the Compressor and Condenser." No 1 4, no. 1 (June 1, 2018): 2–25. http://dx.doi.org/10.51141/ijatr.2018.4.1.1.
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Abstract: This paper presents the thermodynamic performance analysis of an existing combined cycle power plant to be retrofitted with a waste heat driven aqua lithium bromide absorption refrigerator for cooling the inlet air streams to the compressor and air-cooled steam condenser. The power plant is located in the hot and humid tropical region of Nigeria, latitude 4°45′N and longitude 7°00′E. This was achieved by performing energy and exergy analysis of the integrated system. Using the operating data of the existing combined cycle power plant, the results of the analysis showed that by cooling the inlet air streams to 15oC at the compressors, and to 29oC at the air-cooled steam condenser, the net power output, thermal and exergy efficiencies of the combined cycle plant increased by 7.7%, 8.1% and 7.5% respectively while the plant total exergy destruction rate and specific fuel consumption dropped by 10.8% and 7.0% respectively. The stack flue gas exit temperature reduced from 126oC to 84oC in the absorption refrigerator, thus reducing the environmental thermal pollution. The COP and exergy efficiency of the refrigeration cycle was 0.60 and 27.0%, respectively. Results also show that the highest rate of exergy destruction in the combined cycle power plant occurred in the combustion chamber while the highest rate of exergy destruction in the absorption refrigeration cycle occurred in the evaporator followed by the absorber.
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Zabet, Ion, and Gratiela Maria Tarlea. "Mathematical Simulation of the Thermodynamic Processes Associated with the Vapour-Injected Scroll Compressor." E3S Web of Conferences 111 (2019): 06057. http://dx.doi.org/10.1051/e3sconf/201911106057.
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Both the major energetic crisis and the global warming, which influence the worldwide economy and the future of the society, determine the development of energetic and ecological performances of both the refrigeration equipment and air conditioning systems. Thus, there is a worldwide supported effort made in order to decrease the carbon dioxide emissions resulted from the burning of fossil fuels and the other greenhouse effect gas emissions. This article presents a refrigeration system design model using a vapour injection scroll compressor and tube in tube evaporators working with refrigerant R407C. The refrigerant circuit comprises of a main evaporator, a secondary evaporator (for the injection process), scroll compressor, condenser and five expansion valves. Furthermore it uses R407C as refrigerant. The secondary refrigerant for both the main and the secondary evaporator is a 50% concentration solution of propylene-glycol and water. Secondary circuit comprises of a pump, an electric boiler, an expansion vessel and a by-pass circuit made of many stop valves. The condenser is cooled with mains water.
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Joachimiak, Magda, Damian Joachimiak, and Piotr Krzyślak. "Analysis of heat flow in a tube bank of a condenser considering the influence of air." Archives of Thermodynamics 38, no. 3 (September 1, 2017): 119–34. http://dx.doi.org/10.1515/aoter-2017-0019.
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Abstract The pressure of wet water vapor inside a condenser has a great impact on the efficiency of thermal cycle. The value of this pressure depends on the mass share of inert gases (air). The knowledge of the spots where the air accumulates allows its effective extraction from the condenser, thus improving the conditions of condensation. The condensation of water vapor with the share of inert gas in a model tube bank of a condenser has been analyzed in this paper. The models include a static pressure loss of the water vapor/air mixture and the resultant changes in the water vapor parameters. The mass share of air in water vapor was calculated using the Dalton’s law. The model includes changes of flow and thermodynamic parameters based on the partial pressure of water vapor utilizing programmed water vapor tables. In the description of the conditions of condensation the Nusselts theory was applied. The model allows for a deterioration of the heat flow conditions resulting from the presence of air. The paper contains calculations of the water vapor flow with the initial mass share of air in the range 0.2 to 1%. The results of calculations clearly show a great impact of the share of air on the flow conditions and the deterioration of the conditions of condensation. The data obtained through the model for a given air/water vapor mixture velocity upstream of the tube bank allow for identification of the spots where the air accumulates.
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O'Donovan, Alan, and Ronan Grimes. "A theoretical and experimental investigation into the thermodynamic performance of a 50 MW power plant with a novel modular air-cooled condenser." Applied Thermal Engineering 71, no. 1 (October 2014): 119–29. http://dx.doi.org/10.1016/j.applthermaleng.2014.06.045.
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Labay, V. Yo, V. Yu Yaroslav, O. M. Dovbush, and A. Ye Tsizda. "Mathematical modeling bringing the operation of air split conditioners heat pumps to the same internal temperature conditions." Mathematical Modeling and Computing 8, no. 3 (2021): 509–14. http://dx.doi.org/10.23939/mmc2021.03.509.
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Nowadays, the use of heat pumps (HP) of air split-conditioners in air conditioning and heating systems of small industrial, public and residential facilities is becoming more common. It is known that the nominal heat capacity of HP of air split-conditioners is given in catalogs or reference literature under standard outdoor temperature conditions, namely: outdoor air temperature +7oС, indoor air temperature +21oС. At the same time, manufacturers of air split-conditioners do not ensure that, regardless of the size of heating capacity, all air split-conditioners have the same internal temperature conditions, namely: the evaporation temperature of the refrigerant and its condensation temperature. In this case, the thermodynamic efficiency, which can be best assessed by the exergetic output-input ratio (OIR) of different heating capacity of HP of air split-conditioners, is different; this, in our opinion, is incorrect. However, today there is a lack of mathematical models of bringing the operation of air split-conditioners HP to the similar internal temperature conditions, which will allow us to obtain the same exergetic OIR for different heating capacity of HP. To create the mathematical model of bringing the operation of HP of air split-conditioners to the equal internal temperature conditions, we have proposed them, namely: the evaporation temperature of the refrigerant +0.7oC and its condensation temperature +40oC. Taking these temperatures on the basis of the heat balances of the HP evaporator and HP condenser of air split-conditioners, we obtained the dependences for calculating air flow rates on the evaporator and condenser, which respectively maintain the proposed temperatures.
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Larionov, Alexey V., Ludmila Y. Udoeva, and Vladimir M. Chumarev. "Thermodynamic simulation of oxidation process of the Moss-Mo3Si hypoeutectic alloy, doped with scandium or neodymium." Butlerov Communications 57, no. 2 (February 28, 2019): 90–100. http://dx.doi.org/10.37952/roi-jbc-01/19-57-2-90.
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In order to study the effect of yttrium additives on the oxidation of molybdenum silicide alloys, thermodynamic modeling of the interaction in Mo-Mo3Si-Sc5Si3 и Mo-Mo3Si-NdSi systems with dry and moist air was performed in the temperature range 25-2000 °C. The calculations were performed using the HSC Chemistry 6.12 software, into the database of which the calculated missing thermochemical characteristics silicates, molybdates of scandium and neodymium were entered. Based on the obtained dependences of the composition of phases on temperature and charge of the oxidant (air or vapor-air mixture), the sequence of phase formation was determined and the compositions of oxidation products were estimated. It is shown that, under equilibrium conditions, the oxidation process with dry and moist air proceeds almost equally, since the interaction of the components of the alloy with oxygen is thermodynamically preferable than with water vapor. According to the obtained thermodynamic models, the oxidation process of the Mo-5Si-3(Sc, Nd) (wt.%) alloys involves a sequence of the following chemical transformations: at the beginning Mo and Sc (Nd) silicides oxidize forming Sc2O3 ( Nd2O3), SiO2 and elemental Mo, then molybdenum is oxidized to MoO2 and Sc2O3 or Nd2O3 interacts with SiO2 with the formation of appropriate silicates Sc2Si2O7 или Nd2Si2O7. As a result of the complete oxidation of the alloy, MoO3 and Sc2(MoO4)3 or Nd2Mo4O15 are added to the condensed product, and molybdenum oxide (MoO3)n vapor appears in the gas phase. In addition, the formation of Nd2Mo2O7 and Nd2 (MoO4)3 is possible. During the oxidation of the Mo-5Si-3Nd alloy at T> 1700 oC, Nd(OH)3 can be formed in the condensed reaction products. According to the results of complete thermodynamic analysis, the formation of silicates and molybdates of scandium and neodymium can promote to the formation of a protective film on the surface of the alloys, which limits the diffusion of oxygen in them, and as a result, the oxidation resistance of alloys should increase.
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Clegg, S. L., M. J. Kleeman, R. J. Griffin, and J. H. Seinfeld. "Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model – Part 1: Treatment of inorganic electrolytes and organic compounds in the condensed phase." Atmospheric Chemistry and Physics 8, no. 4 (February 27, 2008): 1057–85. http://dx.doi.org/10.5194/acp-8-1057-2008.
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Abstract. Air quality models that generate the concentrations of semi-volatile and other condensable organic compounds using an explicit reaction mechanism require estimates of the physical and thermodynamic properties of the compounds that affect gas/aerosol partitioning: vapour pressure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co-workers (e.g., Griffin et al., 2003; Kleeman et al., 1999) assumes that aerosol particles consist of an aqueous phase, containing inorganic electrolytes and soluble organic compounds, and a hydrophobic phase containing mainly primary hydrocarbon material. Thirty eight semi-volatile reaction products are grouped into ten surrogate species which partition between the gas phase and both phases in the aerosol. Activity coefficients of the organic compounds are calculated using UNIFAC. In a companion paper (Clegg et al., 2008) we examine the likely uncertainties in the vapour pressures of the semi-volatile compounds and their effects on partitioning over a range of atmospheric relative humidities. In this work a simulation for the South Coast Air Basin surrounding Los Angeles, using lower vapour pressures of the semi-volatile surrogate compounds consistent with estimated uncertainties in the boiling points on which they are based, yields a doubling of the predicted 24-h average secondary organic aerosol concentrations. The dependency of organic compound partitioning on the treatment of inorganic electrolytes in the air quality model, and the performance of this component of the model, are determined by analysing the results of a trajectory calculation using an extended version of the Aerosol Inorganics Model of Wexler and Clegg (2002). Simplifications are identified where substantial efficiency gains can be made, principally: the omission of dissociation of the organic acid surrogates; restriction of aerosol organic compounds to one of the two phases (aqueous or hydrophobic) where equilibrium calculations suggest partitioning strongly in either direction; a single calculation of activity coefficients of the organic compounds for simulations where they are determined by the presence of one component at high concentration in either phase (i.e., water in the aqueous phase, or a hydrocarbon surrogate compound P8 in the hydrophobic phase) and are therefore almost invariant. The implications of the results for the development of aerosol models are discussed.
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Clegg, S. L., M. J. Kleeman, R. J. Griffin, and J. H. Seinfeld. "Effects of uncertainties in the thermodynamic properties of aerosol components in an air quality model – Part I: Treatment of inorganic electrolytes and organic compounds in the condensed phase." Atmospheric Chemistry and Physics Discussions 7, no. 4 (July 26, 2007): 10971–1047. http://dx.doi.org/10.5194/acpd-7-10971-2007.
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Abstract. Air quality models that generate the concentrations of semi-volatile and other condensable organic compounds using an explicit reaction mechanism require estimates of the physical and thermodynamic properties of the compounds that affect gas/aerosol partitioning: vapour pressure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co-workers (e.g., Griffin et al., 1999; Kleeman et al., 1999) assumes that aerosol particles consist of an aqueous phase, containing inorganic electrolytes and soluble organic compounds, and a hydrophobic phase containing mainly primary hydrocarbon material. Thirty eight semi-volatile reaction products are grouped into ten surrogate species which partition between the gas phase and both phases in the aerosol. Activity coefficients of the organic compounds are calculated using UNIFAC. In a companion paper (Clegg et al., 2007) we examine the likely uncertainties in the vapour pressures of the semi-volatile compounds and their effects on partitioning over a range of atmospheric relative humidities. In this work a simulation for the South Coast Air Basin surrounding Los Angeles, using lower vapour pressures of the semi-volatile surrogate compounds consistent with estimated uncertainties in the boiling points on which they are based, yields a doubling of the predicted 24-h average secondary organic aerosol concentrations. The dependency of organic compound partitioning on the treatment of inorganic electrolytes in the air quality model, and the performance of this component of the model, are determined by analysing the results of a trajectory calculation using an extended version of the Aerosol Inorganics Model of Wexler and Clegg (2002). Simplifications are identified where substantial efficiency gains can be made, principally: the omission of dissociation of the organic acid surrogates; restriction of aerosol organic compounds to one of the two phases (aqueous or hydrophobic) where equilibrium calculations suggest partitioning strongly in either direction; a single calculation of activity coefficients of the organic compounds for simulations where they are determined by the presence of one component at high concentration in either phase (i.e., water in the aqueous phase, or a hydrocarbon surrogate compound P8 in the hydrophobic phase) and are therefore almost invariant. The implications of the results for the development of aerosol models are discussed.
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Saikov, Ivan, Stepan Seropyan, Andrey Malakhov, Gulnaz Saikova, Igor Denisov, and Evgenii Petrov. "Energetic Materials Based on W/PTFE/Al: Thermal and Shock-Wave Initiation of Exothermic Reactions." Metals 11, no. 9 (August 29, 2021): 1355. http://dx.doi.org/10.3390/met11091355.
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The parameters of combustion synthesis and shock-wave initiation of reactive W/PTFE/Al compacts are investigated. Preliminary thermodynamic calculations showed the possibility of combustion of the W/PTFE/Al system at high adiabatic temperatures (up to 2776 °C) and a large proportion of condensed combustion products. The effect of the Al content (5, 10, 20, and 30 wt%) in the W/PTFE/Al system on the ignition and development of exothermic reactions was determined. Ignition temperatures and combustion rates were measured in argon, air, and rarefied air. A correlation between the gas medium, rate, and temperature of combustion was found. The shock initiation in W/PTFE/Al compacts with different Al content was examined. The extent of reaction in all compacts was studied by X-ray diffraction. The compositions with 10 and 20 wt% Al showed the highest completeness of synthesis after combustion and shock-wave initiation.
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Bacri, J., and S. Raffanel. "Calculation of some thermodynamic properties of air plasmas: Internal partition functions, plasma composition, and thermodynamic functions." Plasma Chemistry and Plasma Processing 7, no. 1 (March 1987): 53–87. http://dx.doi.org/10.1007/bf01015999.
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Larionov, Alexey V., Ludmila Y. Udoeva, and Vladimir M. Chumarev. "Thermodynamic simulation of oxidation process of the Moss-Mo3Si hypoeutectic alloy, doped with yttrium." Butlerov Communications 57, no. 2 (February 28, 2019): 101–10. http://dx.doi.org/10.37952/roi-jbc-01/19-57-2-101.
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In order to study the effect of yttrium additives on the oxidation of molybdenum silicide alloys, thermodynamic modeling of the interaction in the Mo-Mo3Si-Y5Si3 system with dry and moist air was performed in the temperature range 25-2000 °C. To predict the composition of oxidation products and the sequence of the formation of phase components, the dependences on the temperature and consumption of oxidants – water vapor and oxygen of the air – are obtained. The calculations were performed using the HSC Chemistry 6.12 software, into the database of which the calculated missing thermochemical characteristics of Y2Si2O7, Y2SiO5 silicates and yttrium molybdates Y2Mo3O12, Y2MoO6 were entered. It is shown that, under equilibrium conditions, the oxidation process with dry and moist air proceeds almost equally, since the interaction of the components of the alloy with oxygen is thermodynamically preferable than with water vapor. According to the obtained thermodynamic models, the oxidation process of the Mo-5 wt. % Si alloy of the hypoeutectic composition doped with yttrium can be represented as a sequence of the following chemical transformations: firstly Mo and Y silicides oxidize forming Y2O3, SiO2 and metallic Mo, then molybdenum is oxidized to MoO2 and Y2O3 interacts with SiO2 with the formation of silicates Y2SiO5 and Y2Si2O7. As a result of the complete oxidation of the alloy, MoO3 and Y2Mo3O12 are added to the condensed product, and molybdenum oxide (MoO3)n vapor appears in the gas phase. Based on the results of a complete thermodynamic analysis, the possibility of the formation of silicates and yttrium molybdate during the oxidation of the hypoeutectic alloy Mo-5Si-3Y (wt. %) was established. This can increase its oxidation resistance due to the formation of a protective film limiting the diffusion of oxygen into the alloy, which, of course, requires experimental confirmation.
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Cucumo, Mario, Vittorio Ferraro, Dimitrios Kaliakatsos, and Valerio Marinelli. "A CALCULATION MODEL FOR A THERMODYNAMIC ANALYSIS OF SOLAR PLANTS WITH PARABOLIC COLLECTORS COOLED BY AIR EVOLVING IN AN OPEN JOULE-BRAYTON CYCLE." International Journal of Heat and Technology 31, no. 02 (December 31, 2013): 127–34. http://dx.doi.org/10.18280/ijht.310217.
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Cheli, Lapo, and Carlo Carcasci. "Modelling and analysis of a liquid-cooled system for thermal management application of an electronic equipment." E3S Web of Conferences 197 (2020): 10008. http://dx.doi.org/10.1051/e3sconf/202019710008.
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The removal of heat from electronic components, increasingly miniaturized with high power dissipation per unit volume, is a significant industrial problem to be resolved, to avoid failures due to excessive temperatures and besides to maintain performance and operating conditions. This article describes the development of a one-dimensional thermodynamic model to simulate the cooling of electronic chips belonging to inverters for stationary PV solar arrays; these are typically located in very different environments, including deserts or very hot areas, so the operating life of theirs inverter units are strongly affected by changes in external environmental conditions. Results have shown that the model allows, with very low calculation times, to quantify the effects of cooling performance and thermal load of electronics both in design and off-design conditions: the working temperature of the components was monitored as the effectiveness of the main heat exchanger vary with the exposure to the external environment over time, in terms of fouling and as the ambient air temperature changes; in this case a simple control system was simulated to limit the maximum temperature of the chips and the air flow rate of the fans. The thermal performances of two types of glycol-based refrigerant fluids have been compared.
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Lozza, G., P. Chiesa, and L. DeVita. "Combined-Cycle Power Stations Using “Clean-Coal Technologies”: Thermodynamic Analysis of Full Gasification Versus Fluidized Bed Combustion With Partial Gasification." Journal of Engineering for Gas Turbines and Power 118, no. 4 (October 1, 1996): 737–48. http://dx.doi.org/10.1115/1.2816989.
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A novel class of power plants for clean conversion of coal into power has been recently proposed, based on the concept of partial coal gasification and fluidized-bed combustion of unconverted char from gasification. This paper focuses on the thermodynamic aspects of these plants, in comparison with full gasification cycles, assessing their performance on the basis of a common advanced power plant technology level. Several plant configurations are considered, including pressurized or atmospheric fluidized-bed, air- or steam-cooled, with different carbon conversion in the gasifier. The calculation method, used for reproducing plant energy balances and for performance prediction, is described in the paper. A complete second-law analysis is carried out, pointing out the efficiency loss breakdown for both technologies. Results show that partial gasification plants can achieve efficiencies consistently higher than IGCC, depending on plant configuration and carbon conversion, making this solution a viable and attractive option for efficient coal utilization.
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You, Dali, Christian Bernhard, Peter Mayer, Josef Fasching, Gerald Kloesch, Roman Rössler, and Rainer Ammer. "Modeling of the BOF Tapping Process: The Reactions in the Ladle." Metallurgical and Materials Transactions B 52, no. 3 (April 8, 2021): 1854–65. http://dx.doi.org/10.1007/s11663-021-02153-2.
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AbstractA tapping process model of the steel from the basic oxygen furnace (BOF) addressing the reactions in the ladle is proposed. In the model, the effective equilibrium reaction zone (EERZ) method is applied to describe the steel/slag interfacial reaction. The equilibrium reactions in the bulk steel (steel/inclusion/lining wear) and slag (liquid slag/slag additions/lining wear) are considered. The thermodynamic library—ChemApp is used to perform thermodynamic calculation. The process model includes most of the actions during the tapping process, such as the additions of ferroalloys and slag formers, carryover slag entrapment and air pick-up. After the calibration by the industrial measurements of two plants, the model is applied to study the influence of the amount of carryover slag.
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Salik, Muhammad, Muhammad Hanif, Jiasheng Wang, and Xi-Qing Zhang. "Spectral studies of nanosecond laser interaction with magnesium sulfate target in air." Journal of Plasma Physics 80, no. 1 (December 13, 2013): 67–80. http://dx.doi.org/10.1017/s0022377813000986.
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AbstractThe optical emission characterization of the plasma-assisted pulsed laser ablation of the magnesium sulfate target is discussed in this study. The emission spectrum produced by the magnesium sulfate plasma in the wavelength range 200–700 nm has been carefully investigated for different experimental conditions. The spectra analysis was performed by assuming the local thermodynamic equilibrium (LTE) approximation and calculating the plasma temperature with the Boltzmann plot method using neutral Mg spectral lines. The plasma temperature was obtained for different positions along the expansion axis, which allowed obtaining the electron population distribution as a function of the distance from the target. The plasma temperature along the expansion axis allowed evaluating the evolution of the excited states population when the plume expands. Moreover, the Stark broadening method has been employed for electron number density measurements. In this study, the Stark width of the Mg (I) spectral line at 285.21 nm was used. Besides, we have studied the variation of electron temperature (Te) and electron number density (Ne) as a function of laser irradiance.
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CHOI, BONG-JAE, KYUNG-EUI HONG, and YOUNG-JIG KIM. "MECHANICAL PROPERTIES OF HIGH STRENGTH Al-Mg ALLOY SHEET." International Journal of Modern Physics B 23, no. 06n07 (March 20, 2009): 843–48. http://dx.doi.org/10.1142/s0217979209060129.
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The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al - Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al - Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al - Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF6) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al - Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions.
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Sudadiyo, Sri, and Jupiter Sitorus Pane. "DESAIN AWAL TURBIN UAP TIPE AKSIAL UNTUK KONSEP RGTT30 BERPENDINGIN HELIUM." JURNAL TEKNOLOGI REAKTOR NUKLIR TRI DASA MEGA 18, no. 2 (June 30, 2016): 65. http://dx.doi.org/10.17146/tdm.2016.18.2.2319.
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ABSTRAK DESAIN AWAL TURBIN UAP TIPE AKSIAL UNTUK KONSEP RGTT30 BERPENDINGIN HELIUM. Konsep reaktor daya nuklir yang dikembangkan merupakan jenis reaktor berpendingin gas dengan temperatur tinggi (RGTT). Gas yang digunakan untuk mendinginkan teras RGTT adalah helium. Konsep RGTT ini dapat menghasilkan daya termal 30 MWth sehingga dinamakan RGTT30. Temperatur helium mampu mencapai 700 °C ketika keluar dari teras RGTT30 dan digunakan untuk memanaskan air di dalam steam generator hingga mencapai temperatur 435 °C. Steam generator dihubungkan dengan turbin uap yang dikopel dengan generator listrik untuk membangkitkan daya 7,27 MWe. Uap yang keluar dari turbin dilewatkan kondensor untuk mencairkan uap menjadi air. Rangkaian komponen dari steam generator, turbin, dan kondensor dinamakan sistem turbin uap. Turbin terdiri dari sudu-sudu yang dimaksudkan untuk mengubah tenaga uap kedalam tenaga mekanis berupa putaran. Efisiensi turbin merupakan parameter yang harus diperhatikan dalam sistem turbin uap ini. Tujuan dari makalah ini adalah untuk mengusulkan sudu tipe aksial dan untuk menganalisa perbaikan efisiensi turbin. Metode yang digunakan yaitu aplikasi prinsip termodinamika yang berhubungan dengan konservasi energi dan massa. Perangkat lunak Cycle-Tempo dipakai untuk mendapatkan parameter termodinamika dan untuk mensimulasikan sistem turbin uap berbasis RGTT30. Pertama, dibuat skenario dalam simulasi sistem turbin uap untuk mengetahui efisiensi dan laju aliran massa uap yang diperoleh nilai optimal 87,52 % dan 8,759 kg/s pada putaran 3000 rpm. Kemudian, turbin uap diberi sudu tipe aksial dengan diameter tip 1580 mm dan panjang 150 mm. Hasil yang diperoleh adalah nilai efisiensi turbin uap naik menjadi 88,3 % pada putaran konstan (3000 rpm). Penambahan nilai efisiensi turbin sebesar 0,78 % menunjukkan peningkatan kinerja RGTT30 secara keseluruhan. Kata kunci: Tipe aksial, turbin uap, RGTT30 ABSTRACT PRELIMINARY DESIGN ON STEAM TURBINE OF AXIAL TYPE FOR HELIUM-COOLED RGTT30 CONCEPT. The concept of a nuclear power reactor, which evolves, is high temperature gas-cooled reactor type (HTGR). Gas that is used to cool the HTGR core, is helium. The HTGR concept used in this study can yield thermal power of 30 MWth so that named RGTT30. Helium temperature can reach 700 °C when come out from the RGTT30 core and it is used for heating the water within steam generator to achieve the temperature of 435 °C. The steam generator is connected to a steam turbine, which is coupled with an electricity generator, for generating electric power of 7.27 MWe. The steam that comes out from the turbine is flowed through condenser for changing the steam into water. The component train of steam generator, turbine, and condenser was given the name of steam turbine system. The turbine consists of blades that are intended to transform the steam power into mechanical power in the form of rotational speed. Turbine efficiency is a parameter that must be considered in this steam turbine system. The aims of this paper are to propose blade of axial type and to analyze the efficiency improvement of the turbine. The method used is the application of the thermodynamic principles associated with conservations of energy and mass. Cycle-Tempo software is used to obtain thermodynamic parameters and to simulate the steam turbine system based on RGTT30. Firstly, a scenario is created to model and simulate the steam turbine system for determining the efficiency and the mass flow rate of steam. The optimal values for the efficiency and the mass flow rates at the speed of 3000 rpm are 87.52 % and 8.759 kg/s, respectively. Then, the steam turbine was given the blade of axial type with a tip diameter of 1580 mm and a length of 150 mm. The results obtained are turbine efficiency increasing to 88.3% on constant speed (3000 rpm). Enhancement in the turbine efficiency value of 0.78% showed raising the overall performance of RGTT30. Keywords: Axial type, steam turbine, RGTT30
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Li, Cheng, Andrew P. Ingersoll, and Fabiano Oyafuso. "Moist Adiabats with Multiple Condensing Species: A New Theory with Application to Giant-Planet Atmospheres." Journal of the Atmospheric Sciences 75, no. 4 (March 29, 2018): 1063–72. http://dx.doi.org/10.1175/jas-d-17-0257.1.
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Abstract A new formula is derived for calculating the moist adiabatic temperature profile of an atmosphere consisting of ideal gases with multiple condensing species. This expression unifies various formulas published in the literature and can be generalized to account for chemical reactions. Unlike previous methods, it converges to machine precision independent of mesh size. It accounts for any ratio of condensable vapors to dry gas, from zero to infinity, and for variable heat capacities as a function of temperature. Because the derivation is generic, the new formula is not only applicable to planetary atmospheres in the solar system but also to hot Jupiters and brown dwarfs in which a variety of alkali metals, silicates, and exotic materials condense. It is demonstrated that even though the vapors are ideal gases, they interact in their effects on the moist adiabatic lapse rate. Finally, the authors apply the new thermodynamic model to study the effects of downdrafts on the distribution of minor constituents and the thermal profile in the Galileo probe hot spot. The authors find that the Galileo probe measurements can be interpreted as a strong downdraft that displaces an air parcel from the 1-bar to the 4-bar level (1 bar = 100 000 Pa).
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Rogalev, Andrey, Nikolay Rogalev, Vladimir Kindra, Ivan Komarov, and Olga Zlyvko. "Research and Development of the Oxy-Fuel Combustion Power Cycles with CO2 Recirculation." Energies 14, no. 10 (May 18, 2021): 2927. http://dx.doi.org/10.3390/en14102927.
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The transition to oxy-fuel combustion power cycles is a prospective way to decrease carbon dioxide emissions into the atmosphere from the energy sector. To identify which technology has the highest efficiency and the lowest emission level, a thermodynamic analysis of the semiclosed oxy-fuel combustion combined cycle (SCOC-CC), the E-MATIANT cycle, and the Allam cycle was carried out. The modeling methodology has been described in detail, including the approaches to defining the working fluid properties, the mathematical models of the air separation unit, and the cooled gas turbine cycles’ calculation algorithms. The gas turbine inlet parameters were optimized using the developed modeling methodology for the three oxy-fuel combustion power cycles with CO2 recirculation in the inlet temperature at a range of 1000 to 1700 °C. The effect of the coolant flow precooling was evaluated. It was found that a decrease in the coolant temperature could lead to an increase of the net efficiency up to 3.2% for the SCOC-CC cycle and up to 0.8% for the E-MATIANT cycle. The final comparison showed that the Allam cycle’s net efficiency is 5.6% higher compared to the SCOC-CC cycle, and 11.5% higher compared with the E-MATIANT cycle.
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Teulet, Philippe, Tommy Billoux, Yann Cressault, Mathieu Masquère, Alain Gleizes, Ivan Revel, Bruno Lepetit, and Gilles Peres. "Energy balance and assessment of the pressure build-up around a bolt fastener due to sparking during a lightning impact." European Physical Journal Applied Physics 77, no. 2 (February 2017): 20801. http://dx.doi.org/10.1051/epjap/2017160467.
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This work is devoted to the calculation of the energy balance associated with the formation of an electric arc between the bolt shank and an inner structural part of the fuselage during a lightning strike. Assessment of the pressure build-up in the confined volume around the bolt fastener has also been performed. This pressure rise comes from the temperature increase and from the mass density increase (melting and vaporisation of materials). Previous electrical measurements performed by Airbus Group during a lightning test campaign have been used to calculate the total available electrical energy. The energies necessary for melting and vaporisation of bolt and rib are derived from thermodynamic properties of aluminium and titanium. A numerical code has been developed to determine the chemical composition (under the local thermodynamic equilibrium [LTE] assumption) and the internal energy of the plasma for air-Al/Ti mixtures. Plasma and material radiation losses and heat conduction losses have also been evaluated. Finally, an analytical model has been implemented to determine the overpressure as a function of the deposited electrical energy, the energy involved in the arc formation, the energy necessary for melting and the plasma composition and mass density. With this approach, maximum pressure values are in the range 200–330 bars.
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Haller, B., A. Grimaud, J.-C. Labbe, and J.-P. Bonnet. "TiO-based coatings prepared by plasma spraying in air of Ti + C mixtures." Journal of Materials Research 21, no. 7 (July 1, 2006): 1770–74. http://dx.doi.org/10.1557/jmr.2006.0203.
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This work presents an original way for preparing TiO-based coatings by thermal spraying. As titanium monoxide is oxidized by the mere trace of oxygen contained in hydrogen, it is obvious that plasma spraying of TiO powder does not lead easily to the formation of a titanium monoxide coating. However, thermodynamical calculations show that the conditions necessary for the preparation of TiO can be reached, at the titanium melting temperature (Tm=1933 K), when oxygen reacts with liquid metal in the presence of excess carbon. These results have led to experiments in which TiO-based coatings have been prepared by spraying a stoichiometric mixture of graphite and titanium grains onto cast iron in air. In optimal conditions, a gas-tight hard coating (1000 ± 15 HV3) of a TiO-based phase (composition: TiO0.81±0.06C0.04±0.02) has been obtained.
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Bergin, Are, Claudia Voigt, Robert Fritzsch, Shahid Akhtar, Lars Arnberg, Christos G. Aneziris, and Ragnhild E. Aune. "Experimental Study on the Chemical Stability of Phosphate-Bonded Al2O3-Based Ceramic Foam Filters (CFFs)." Metallurgical and Materials Transactions B 52, no. 4 (April 22, 2021): 2008–25. http://dx.doi.org/10.1007/s11663-021-02144-3.
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AbstractProduction of high-quality aluminum products requires an extensive melt treatment process, even more so with the increasing focus on recycling and sustainability. Filtration is a commonly used process segment for removal of non-metallic inclusions in aluminum, and ceramic foam filters (CFFs) are often used as the filtration media. In the present study, the chemical stability of phosphate-bonded Al2O3-based CFFs has been investigated. Three filters with different chemical compositions have been submerged into pure aluminum (with traces of Mg) and in an aluminum-magnesium melt (~ 2 wt pct Mg) at 730 °C. In addition to filter characterization before and after exposure to molten metal, using various imaging and X-ray techniques, the melt itself was analyzed by spark optical emission spectroscopy. The generation of phosphine gas was also measured by the use of Dräger tubes, and thermodynamic calculations performed using FactSage™. The phosphate-bonded filters were observed to react with the magnesium present in the molten aluminum even at very low magnesium concentrations (0.00035 wt pct), and as the magnesium concentration increased the severity of the degradation became more and more evident. The exposure time proved to have detrimental effect on the filter structure, with pieces of the filter struts broken off causing melt contamination. Severe filter degradation also resulted in color changes with accompanying diffusion of magnesium and phosphorus to and from the filter, respectively. Moreover, phosphine gas was released in amounts exceeding recommended exposure limits when the filter came in contact with the humidity in the air after testing. Good agreement was established to exist between the results from the thermodynamic calculations performed and the experimental results.
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Miyake, Masao, Takashi Sugiura, and Tetsuji Hirato. "Preparation of Polycrystalline CdTe Films by Annealing of Amorphous Films Electrodeposited from Ammoniacal Alkaline Baths." High Temperature Materials and Processes 31, no. 4-5 (October 30, 2012): 553–57. http://dx.doi.org/10.1515/htmp-2012-0092.
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AbstractA new route to prepare polycrystalline CdTe films using electrodeposition of amorphous Cd-Te films and subsequent annealing was investigated. Amorphous Cd-Te films with Te-rich compositions could be electrodeposited from ammoniacal alkaline aqueous solutions. The deposition rate of the amorphous film was much higher than that of crystalline CdTe. Annealing of the Te-rich amorphous Cd-Te film at 400 °C in air yielded a crystallized CdTe film with a nearly stoichiometric composition. Thermodynamic calculations of the vapor pressures of Cd and Te species suggested that the decrease in the Te content of the annealed film was due to the vaporization of Te in the forms of oxides. Although an isothermal annealing generated a number of large holes in the film, an annealing with a slow temperature ramp resulted in a crystalline CdTe film without the large holes.
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Ha, Seong-Ho, Bong-Hwan Kim, Young-Ok Yoon, Hyun-Kyu Lim, and Shae K. Kim. "Combined Effect of Mg and Ca on Oxidation Behaviors of Zn–Mg Based Alloys Containing a Trace of Ca at High Temperature." Journal of Nanoscience and Nanotechnology 21, no. 3 (March 1, 2021): 2063–66. http://dx.doi.org/10.1166/jnn.2021.18937.
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In this study, the combined effect of Mg and Ca on the high temperature oxidation behaviors of Zn–Mg based alloys containing trace Ca was investigated. Phase diagrams for the oxygen partial pressure versus contents of constituent elements were conducted on the basis of thermodynamic calculations to predict oxide scale behavior. Observation of Zn-1/3/5 mass%Mg alloys showed the distribution of a Zn–Zn11Mg2 eutectic phase after primary formation. As-cast microstructures of the Ca-containing alloys included the formation of a Ca-based intermetallic phase. The change in oxidation resistance with variation of the Mg and Ca contents was experimentally examined via thermogravimetric analysis (TGA). The addition of trace Ca led to the formation of Zn13Ca and a CaO/MgO mixed oxide layer on the surface at 460 °C. After TGA at 460 °C under air atmosphere for 1 h, the Ca-free alloys showed rapid weight gain by oxidation, whereas the oxidation resistance of the Ca-added alloys was substantially increased.
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Jiang, Liang, Yiwang Bao, Yuhong Chen, Guiqun Liu, Xiaoli Zhang, Fenglan Han, and Qixing Yang. "Structural Characteristics and Hydration Kinetics of Oxidized Steel Slag in a CaO-FeO-SiO2-MgO System." High Temperature Materials and Processes 38, no. 2019 (February 25, 2019): 290–300. http://dx.doi.org/10.1515/htmp-2017-0163.
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AbstractAlthough steel slag exhibits cementitious properties, the addition of steel slag in cement is still limited due to both the presence of excess iron oxides and instability of free lime and periclase. This paper proposes a method for oxidizing molten slag in air, aiming at extraction of superfluous wustite and stabilization of free lime and periclase. Mineralogical characteristics of raw slag and modified products were examined using X-ray diffraction (XRD), scanning electron microscopy equipped with backscattered electron imaging (SEM-BEI), energy dispersive spectrometry (EDS) and thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC). Thermodynamic calculations were performed to aid to discuss the experimental results. The results indicate that non-magnetic wustite and periclase are transformed into magnetic spinel (magnetite/magnesioferrite) after oxidation. Temperature has a significant effect on the formation of spinel. The mass fraction of free lime decreases from 3.54 wt.% to 0.96 wt.% as a result of the conversion from free lime to calcium ferrite.
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Valencia-Chapi, Robert, Luis Coco-Enríquez, and Javier Muñoz-Antón. "Supercritical CO2 Mixtures for Advanced Brayton Power Cycles in Line-Focusing Solar Power Plants." Applied Sciences 10, no. 1 (December 19, 2019): 55. http://dx.doi.org/10.3390/app10010055.
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This work quantifies the impact of using sCO2-mixtures (s-CO2/He, s-CO2/Kr, s-CO2/H2S, s-CO2/CH4, s-CO2/C2H6, s-CO2/C3H8, s-CO2/C4H8, s-CO2/C4H10, s-CO2/C5H10, s-CO2/C5H12 and s-CO2/C6H6) as the working fluid in the supercritical CO2 recompression Brayton cycle coupled with line-focusing solar power plants (with parabolic trough collectors (PTC) or linear Fresnel (LF)). Design parameters assessed are the solar plant performance at the design point, heat exchange dimensions, solar field aperture area, and cost variations in relation with admixtures mole fraction. The adopted methodology for the plant performance calculation is setting a constant heat recuperator total conductance (UAtotal). The main conclusion of this work is that the power cycle thermodynamic efficiency improves by about 3–4%, on a scale comparable to increasing the turbine inlet temperature when the cycle utilizes the mentioned sCO2-mixtures as the working fluid. On one hand, the substances He, Kr, CH4, and C2H6 reduce the critical temperature to approximately 273.15 K; in this scenario, the thermal efficiency is improved from 49% to 53% with pure s-CO2. This solution is very suitable for concentrated solar power plants coupled to s-CO2 Brayton power cycles (CSP-sCO2) with night sky cooling. On the other hand, when adopting an air-cooled heat exchanger (dry-cooling) as the ultimate heat sink, the critical temperatures studied at compressor inlet are from 318.15 K to 333.15 K, for this scenario other substances (C3H8, C4H8, C4H10, C5H10, C5H12 and C6H6) were analyzed. Thermodynamic results confirmed that the Brayton cycle efficiency also increased by about 3–4%. Since the ambient temperature variation plays an important role in solar power plants with dry-cooling systems, a CIT sensitivity analysis was also conducted, which constitutes the first approach to defining the optimum working fluid mixture for a given operating condition.
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Lei, Huxu, Chaowen Tan, Gangqiang Fan, Dejun Huang, Xiaoming Ding, and Jie Dang. "The Crystallization Behavior of TiO2-CaO-SiO2-Al2O3-MgO Pentabasic Slag with a Basicity of 1.1–1.4." Crystals 11, no. 6 (May 22, 2021): 583. http://dx.doi.org/10.3390/cryst11060583.
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The utilization of titanium-containing blast furnace slag has been an unsolved problem for a long time. Failure to make effective use of the slag, which is caused by a high TiO2 content within it, not only results in a waste of resources, especially titanium, but also increases environmental risk. The key to address the problem is the enrichment and extraction of TiO2 from the slag first. Therefore, in order to study the enrichment of titanium, the crystallization behavior of TiO2-CaO-SiO2-Al2O3-MgO pentabasic slag, the main compositions of titanium-containing blast furnace slag, within the basicity range of 1.1–1.4 was investigated theoretically and experimentally. Thermodynamic calculation shows that perovskite is the main titanium-containing phase and titanium can be enriched in perovskite. By decreasing the temperature, perovskite precipitates at first. Additionally, with the increase of basicity, perovskite precipitation temperature increases continuously, and its amount of precipitation almost does not change, while the amounts of other phases change obviously. The experimental results demonstrate similar results except for the amount of perovskite (with the increase of basicity, perovskite precipitation amount increases slightly), caused by kinetic reason. In addition, the morphology of the slag at different scales was observed. The surface of the cooled slag is granular, vein-like, and irregular, multilaterally shaped from outside to inside. The crystal is dendritic with a spine-like trunk, and the edge is blade-like. In terms of the structure of the crystal, the inner part of it is perovskite, and the outer part is covered with a layer of other phases with spinel inlaying it. Finally, the precipitated mechanism is proposed as well.
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Bhaskaran Anangapal, Hari. "Energy and exergy analysis of fuels." International Journal of Energy Sector Management 8, no. 3 (August 26, 2014): 330–40. http://dx.doi.org/10.1108/ijesm-04-2013-0012.
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Purpose – The purpose of this study is to carry out energy and exergy analysis of fuels. Production of power and heat in industrialized countries is almost entirely based on combustion of fuels. Usually, combustion takes place in boilers or furnace; well-designed boilers have high thermal efficiencies of > 90 per cent. Even very high efficiencies, close to 100 per cent can be achieved depending on the applied fuel and boiler type. These high thermal efficiencies do suggest that combustion processes are highly optimized and do not need further improvements with regard to their thermodynamic performance. Second law (entropy or exergy) evaluations, however, shows that thermodynamic losses of boiler and furnaces are much larger than the thermal efficiencies do suggest. During combustion, air is predominantly used. When using air, the adiabatic combustion temperature depends only on the properties of fuel and air. The determining parameters for optimal fuel utilization are the fuel type, their composition and moisture content, the air temperature and air factor at combustion inlet. Design/methodology/approach – Following assumptions are made for the analysis: calculation on the basis of 100 kg of dry and ash free fuel entering the control volume; fuel entering the control volume at T0, P0 and reacting completely with air entering separately at T0, P0 to form CO2, SO2, N2 and H2O, which exit separately at T0, P0 (T0 = 298 K; P0 = 1 atm); all heat transfer occurs at temperature T0; and the chemical exergy of the ash has been ignored The availability change and the irreversibility for chemical reactions of hydrocarbon fuels were studied because fuel and dry air composed of O2 and N2 react to form products of combustion in the restricted dead state, and fuel and dry air composed of O2 and N2 react to form products of combustion which end up in the environmental (unrestricted) dead state. The difference between the above two statement, is the chemical availability of the product gases as they proceed from the restricted to the unrestricted dead state. These evaluations were made in terms of enthalpy and entropy values of the reacting species. T0 extend these concepts to the most general situation, it is considered a steady-state control volume where the fuels enters at the restricted dead state, the air (oxidant) is drawn from the environment, and the products are returned to the unrestricted dead state. Findings – It is evident from the analysis that an air factor of 1.10-1.20 is sufficient for liquid fuels, whereas solid fuels will require air factors of 1.15–1.3. When the temperatures of the products of combustion (Tp) are cooled down to that of T0, the maximum reversible work occurs. From the analysis, it is clear that the rather low combustion temperature and the need for cooling down the flue gases to extract the required heat are the main causes of the large exergy losses. The maximum second law efficiency also occurs when Tp is set equal to T0. The maximum second law efficiency per kilo mole of fuel is found to be 73 per cent, i.e. 73 per cent of the energy released by the cooling process could theoretically be converted into useful work. It is evident that reducing exergy losses of combustion is only useful if the heat transferred from the flue gas is used at high temperatures. Otherwise, a reduction of exergy loss of combustion will only increase the exergy loss of heat transfer to the power cycle or heat-absorbing process. The exergy loss of combustion can be reduced considerable by preheating combustion air. Higher preheat temperatures can be obtained by using the flue gas flow only for preheating air. The remainder of the flue gas flow can be used for heat transfer to a power cycle or heat-absorbing process. Even with very high air preheat temperatures, exergy losses of combustion are still > 20 per cent. The application of electrochemical conversion of fuel, as is realized in fuel cells, allows for much lower exergy loses for the reaction between fuel and air than thermal conversion. For industrial applications, electrochemical conversion is not yet available, but will be an interesting option for the future. Originality/value – The outcome of the study would certainly be an eye-opener for all the stakeholders in thermal power plants for considering the second law efficiency and to mitigate the irreversibilities.
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Wang, Hui, Yufeng Duan, Yuan Xue, Ya-ning Li, Liu Meng, and Wei Hongqi. "Effects of different coals on mercury distribution in a 6 kWth circulating fluidized bed under air and O2/CO2 atmosphere via experiment and thermodynamic equilibrium calculation." Journal of the Energy Institute 90, no. 2 (April 2017): 229–38. http://dx.doi.org/10.1016/j.joei.2016.02.001.
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Redjeb, Youcef, Khatima Kaabeche-Djerafi, Anna Stoppato, and Alberto Benato. "The IRC-PD Tool: A Code to Design Steam and Organic Waste Heat Recovery Units." Energies 14, no. 18 (September 7, 2021): 5611. http://dx.doi.org/10.3390/en14185611.
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The Algerian economy and electricity generation sector are strongly dependent on fossil fuels. Over 93% of Algerian exports are hydrocarbons, and approximately 90% of the generated electricity comes from natural gas power plants. However, Algeria is also a country with huge potential in terms of both renewable energy sources and industrial processes waste heat recovery. For these reasons, the government launched an ambitious program to foster renewable energy sources and industrial energy efficiency. In this context, steam and organic Rankine cycles could play a crucial role; however, there is a need for reliable and time-efficient optimization tools that take into account technical, economic, environmental, and safety aspects. For this purpose, the authors built a mathematical tool able to optimize both steam and organic Rankine units. The tool, called Improved Rankine Cycle Plant Designer, was developed in MATLAB environment, uses the Genetic Algorithm toolbox, acquires the fluids thermophysical properties from CoolProp and REFPROP databases, while the safety information is derived from the ASHRAE database. The tool, designed to support the development of both RES and industrial processes waste heat recovery, could perform single or multi-objective optimizations of the steam Rankine cycle layout and of a multiple set of organic Rankine cycle configurations, including the ones which adopt a water or an oil thermal loop. In the case of the ORC unit, the working fluid is selected among more than 120 pure fluids and their mixtures. The turbines’ design parameters and the adoption of a water- or an air-cooled condenser are also optimization results. To facilitate the plant layout and working fluid selection, the economic analysis is performed to better evaluate the plant economic feasibility after the thermodynamic optimization of the cycle. Considering the willingness of moving from a fossil to a RES-based economy, there is a need for adopting plants using low environmental impact working fluids. However, because ORC fluids are subjected to environmental and safety issues, as well as phase out, the code also computes the Total Equivalent Warming Impact, provides safety information using the ASHRAE database, and displays an alert if the organic substance is phased out or is going to be banned. To show the tool’s potentialities and improve the knowledge on waste heat recovery in bio-gas plants, the authors selected an in-operation facility in which the waste heat is released by a 1 MWel internal combustion engine as the test case. The optimization outcomes reveal that the technical, economic, environmental, and safety performance can be achieved adopting the organic Rankine cycle recuperative configuration. The unit, which adopts Benzene as working fluid, needs to be decoupled from the heat source by means of an oil thermal loop. This optimized solution guarantees to boost the electricity production of the bio-gas facility up to 15%.
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Olshevska, Olga V. "COMPUTER PROGRAM FOR CALCULATION MICROCHANNEL HEAT EXCHANGERS FOR AIR CONDITIONING SYSTEMS." Refrigeration Engineering and Technology 52, no. 3 (August 9, 2016). http://dx.doi.org/10.15673/ret.v52i3.123.
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Creating a computer program to calculate microchannel air condensers to reduce design time and carrying out variant calculations. Software packages for thermophysical properties of the working substance and the coolant, the correlation equation for calculating heat transfer, aerodynamics and hydrodynamics, the thermodynamic equations for the irreversible losses and their minimization in the heat exchanger were used in the process of creating. Borland Delphi 7 is used for creating software package.
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Beschliesser, M., F. Appel, H. Kestler, and H. Clemens. "Microstructural Changes of a γ-TiAl Based Alloy with a Fully Lamellar Microstructure Due to Annealing at Elevated Temperatures." MRS Proceedings 753 (2002). http://dx.doi.org/10.1557/proc-753-bb5.3.
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ABSTRACTThe changes of a fully lamellar microstructure caused by annealing at 700 and 800°C for up to 10,000 hours in air have been investigated for a Ti-46.5at.%Al-4at.%(Cr,Nb,Ta,B) sheet material. Changes in morphology as well as in chemical composition and volume fraction of constitutional phases were recorded by means of transmission electron microscopy. Thermodynamic equilibrium calculations performed with the software package ThermoCalc provide baseline information upon both the chemical composition and the amount of constitutional phases of the investigated multi-component alloy. It could be demonstrated that due to high cooling rates which are required to adjust a “defect-free” undisturbed fully lamellar microstructure, composition and amount of the α2 phase are far from the thermodynamic equilibrium. However, during high temperature exposure the composition as well as the amount of α2 phase move towards the values predicted by the calculation. Furthermore, former perfectly shaped γ/α2 lamellae interfaces are disturbed, α2 lamellae decompose and new phases appear instead. Dislocations emitted from dissolving α2 lamellae move into the γ lamellae. Mechanisms responsible for decomposition of lamellae and formation of new phases are explained by thermodynamic equilibrium calculations and diffusion considerations. Finally, results of tensile tests conducted at room temperature and 700°C on long-term annealed specimens are presented and discussed. This work is a basis for understanding microstructural changes and their impact on mechanical properties of γ-TiAl based alloys with a fully lamellar microstructure during service at elevated temperatures.
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Alomair, Muath, Yazeed Alomair, Shohel Mahmud, and Hussein A. Abdullah. "Theoretical and Experimental Investigations of Solar-Thermoelectric Air-Conditioning System for Remote Applications." Journal of Thermal Science and Engineering Applications 7, no. 2 (June 1, 2015). http://dx.doi.org/10.1115/1.4029678.
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In this paper, we have designed and constructed a low cost solar-thermoelectric (TE) air-conditioning system for people in remote areas where electricity is still in short supply. Such system can be potentially used to condition tents and living areas. The proposed solar-powered TE air-conditioning system is based on the principles of Peltier effect to create a finite temperature difference across the condenser and the evaporator of the TE air-conditioning system. The cold side (or the evaporator) of the TE module is used for air-conditioning application; provides cooling to the living space. The thermal energy from the hot side of the module is dumped to the surrounding environment. Using the existing heat transfer and thermodynamics knowledge, an analytical model is developed to predict the performance of the solar-TE air-conditioning system in terms of the hot and cold reservoir temperatures, heat removal rates from the conditioned space, power input, and coefficient of performance (COP). A second analytical model is proposed to predict the cooling down period of the conditioned space as a function of heat removed by air-conditioning system, heat gained through the wall of the conditioned space, and heat generated inside the conditioned space. A detailed system is constructed to predict the performance of solar-TE air-conditioning system experimentally. A conditioned space was constructed to carry out the experimental work. Multiple air-conditioning systems were installed in the conditioned space. The cooling performance of the designed solar-TE air-conditioning system was experimentally tested and verified with the analytical calculation.
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Kim, I., S. Niki, P. J. Fons, T. Kurafuji, M. Okutomi, and A. Yamada. "The Effects of Air Annealing on Cuinse2 Thin Films Grown by Molecular Beam Fpitaxy." MRS Proceedings 426 (1996). http://dx.doi.org/10.1557/proc-426-261.
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AbstractHigh quality epitaxial CuInSe2 (CIS) films with a range of Cu/In ratios (γ) = 0.80∼2.24 grown by molecular beam epitaxy (MBE) have been post-annealed at temperatures of TA=200∼400°C in both dry-air and Ar atmospheres. Changes in the structure and composition due to annealing have been investigated. The only oxide observed experimentally for both the In-rich, and the Cu-rich CIS films was In2O3. This is consistent with equilibrium thermodynamic calculations which indicate that In2O3 is the mnst stable solid oxide phase. During annealing some reac-tions arc probably kinetically limited making the annealing process a function of time and temperature. but the equilibrium thermodynamic results reported here simplify interpretation of phase space.
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Berche, Alexandre, Thierry Alpettaz, Sylvie Chatain, Stephane Gossé, Christine Guéneau, and Cyril Rado. "Chemical Compatibility at High Temperature between the Carbide Fuel UC or (U,Pu)C and SiC Cladding for the Gas cooled Fast Reactor." MRS Proceedings 1264 (2010). http://dx.doi.org/10.1557/proc-1264-z04-03.
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AbstractThe chemical compatibility at high temperature between the fuel kernel (U,Pu)C and SiC cladding, the reference materials for the GFR reactor, is studied. For that purpose, a thermodynamic database on the U-Pu-C-Si system was developed with the Calphad method to calculate the phase diagrams. Differential thermal analysis experiments were performed to measure phase transition temperatures in Si-U and C-Si-U systems. According to the calculated isopleth section between the hyperstoichiometric uranium carbide UC1.02 and SiC, the materials shall not react below 2056 K, the temperature at which a liquid phase shall form. These calculations are in good agreement with two chemical compatibility tests performed at 1873 K and 2073 K between the materials. Calculations were also performed to study the chemical interaction between the mixed carbide (U,Pu)C1.04 and SiC. The presence of plutonium in the fuel kernel lowers the liquid formation temperature of 167 K.
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Donchev, A., P. J. Masset, and M. Schütze. "Surface Treatment of TiAl with Fluorine for Improved Performance at Elevated Temperatures." MRS Proceedings 1128 (2008). http://dx.doi.org/10.1557/proc-1128-u04-09.
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AbstractAlloys based on aluminium and titanium are possible materials for several high temperature applications. The use of TiAl would increase the efficiency of e.g. aero turbines, automotive engines and others due to their properties, among others low specific weight and good high temperature strength. The oxidation resistance is low at temperatures above approximately 800°C so that no long term use of TiAl-components is possible without improvement of the oxidation behaviour. Small amounts of halogens in the surface zone of TiAl-samples lead to a dramatic improvement of the oxidation resistance at temperatures up to 1100°C for more than 8000 hours in air. In this paper results of the work on the halogen effect over the last years are presented. The results of thermogravimetric measurements, thermocyclic oxidation tests of small coupons and thermodynamic calculations for different atmospheres (e.g. air, H2O, SO2) are shown and the halogen effect mechanism is discussed. The postulated mechanism is in good agreement with the results of the oxidation tests. The limits of the halogen effect will also be mentioned. Predictions for the halogenation of TiAl-components can be given so that the processing can be planned in advance.