Elevated Temperature Heat Research Articles

Post-fire residual mechanical properties of Q460GJ steel under different pre-tensile stresses

Previous studies on the post-fire mechanical properties of steel were conducted with unstressed state, without considering the influence of pre-stress which subjected to structures in reality. In this article, the post-fire residual mechanical properties of Q460GJ steel under different pre-tensile stresses were studied. The stress-strain curve, elastic modulus, yield strength, ultimate strength and fracture elongation of Q460GJ steel after different elevated temperatures heating are analyzed in detail. The experimental results are compared with that of Q460 steel and S460 steel in the existing literatures. At last, the predictive equations of post-fire mechanical properties of Q460GJ steel under different pre-tensile stresses are established. Q460GJ steel still maintains good ductility after elevated temperature heating, which increases the possibility of reuse of Q460GJ steel element after fire. The Q460GJ steel has better post-fire ductility than that of Q460 and S460 steels. The predictive equations for the post-fire residual mechanical properties for Q460GJ steel under different pre-tensile stresses were proposed. The variation coefficients of yield strength for Q460GJ steel under different pre-tensile stresses after 20 min different elevated temperatures heating were within 0.065. The findings should have a great significance to providing theoretical support for design of reusing or restoring steel building after fire.

Residual load capacity of HVFA reinforced concrete after elevated temperature heating: Experimental and analytical study

High volume fly ash (HVFA) is used as structural concrete's main constituent in the current concrete construction practice. The residual load capacity of HVFA reinforced concrete after elevated temperature heating is needed for retrofitting compression members after fire exposure. In this experimental study, an effort has been made to estimate the axial load capacity of concrete containing HVFA after 28 and 90 days of curing after elevated temperature heating at 200 °C, 400 °C and 600 °C. The 35% and 50% amount of cement was partially replaced by fly ash. The weight loss and crack pattern in reinforced HVFA concrete were also studied. It has been observed that after heating at elevated temperature, the compression behavior of fly ash concrete is better than that of plain concrete. The analytical models are proposed to estimate the residual load capacity of HVFA concrete columns after exposure to elevated temperature. The model predictions are reasonably good. These models can be used to assess the load carrying capacity of columns in concrete buildings containing HVFA after elevated temperature exposure for deciding strengthening schemes.

Review of liquid desiccant air dehumidification systems coupled with heat pump: System configurations, component design, and performance

Vapor Compression Systems (VCS) are the most common air conditioning technology. VCS cool the air to its dew point temperature (overcooling) to remove water vapor in the air through condensation and then reheats the air back to the comfort temperature for direct use. The VCS process is inefficient due to overcooling and reheating. Liquid Desiccant Dehumidification (LDD) is a potentially energy-efficient air conditioning. LDD removes water vapor in the process air using liquid desiccant’s high-water affinity. It hybrids with sensible cooling to control temperature and humidity separately. The LD in the LDD becomes weak after dehumidification. The LDD needs additional heating to regenerate the weak Liquid Desiccant (LD) to a high concentration for dehumidification.Earlier versions of the LDD systems use highly concentrated liquid desiccant (large water removal capability) to dehumidify the air by only dealing with latent load. It leads to highly elevated temperatures above 60 °C of heat sources (combustion or electric resistance-based heating) for regeneration. The energy needed for the elevated temperature heat resource significantly reduces or demolishes the benefit of LDD systems. In the recent two decades, researchers have investigated a new configured LDD system that couples an LDD with a heat pump at both dehumidification and regeneration sides for better efficiency.The heat pump provides cooling (from the evaporator) for both dehumidification and sensible cooling and simultaneous heating from the condenser for regeneration. The highly integrated system (HP-LDD) with improved efficiency enables the LDD to operate at lower concentrations and temperatures in dehumidification and regeneration.This paper depicts the working principle behind HP-LDD and its heating and cooling requirements. It reviews the comparison between the HP-LDD systems and the conventional LDD systems regarding system configurations, component design, energy efficiency, and dehumidification performance characteristics. The main findings from the review include the preferred use of packed bed over membrane-based dehumidifiers, the use of internally cooled dehumidifiers enabled by the HP cooling capacity, the high dispersion of HP operation conditions, and the dependence of dehumidification performance on various dehumidifiers. An outlook for future research on HP-LDD strategies is presented based on the reviewed works and their limitations.

Modeling Urban Impact on Zhengzhou Storm on July 20, 2021

AbstractThe heavy storm event that occurred from 18 to 22 July 2021, in Henan province caused severe floods and casualties, especially in the provincial city, Zhengzhou. While the impacts of large‐scale synoptic systems and local‐scale orographic effects on the storm event have been studied, the role of urbanization remains unexplored. Using Weather Research and Forecasting model, the study designed two numerical experiments, differentiated by the presence of urban land cover, to investigate the urban impact on the storm event over Henan province, with a focus on Zhengzhou. Urbanization increases precipitation in the major urban area of Zhengzhou and its south, western Kaifeng, and western Xuchang, where the largest increases reach from 188.2 to 304.4 mm. Further investigation into Zhengzhou city reveals that urbanization leads to shifted precipitation center and stagnation in the major urban area, resulting in earlier peak rainfall time and more concentrated precipitation. Elevated surface temperature and sensible heat are identified before the peak rainfall arrives, which leads to increased planet boundary layer height, suggesting the contribution of the urban heat island effect. Thermal perturbation and increased surface roughness over urban areas promote vertical uplift and moisture convergence, increasing water vapor and forming storm system drags during the peak precipitation time, thus bringing earlier and higher amounts of precipitation to the major urban area and its south. The study calls for the consideration of the urban effect of extreme storm events and the precaution against waterlogging over urban areas in rapid‐developing cities.

Prognostic impact of neck responders on conception rate of Czech Fleckvieh Simmental cows

Article Details: Received: 2020-10-25 | Accepted: 2020-11-27 | Available online: 2021-01-31 https://doi.org/10.15414/afz.2021.24.mi-prap.58-61 The climate in the Czech Republic is mild, transient between oceanic and continental, with a typical alternation of 4-year periods. The continental climate is characterized by high temperatures in summer and low temperatures in winter. During the extreme fluctuation of microclimatic conditions in the stable, there is also a change in individual reproductive indicators due to disruption of hormonal secretion, which further affects individual physiological processes, thus worsening conception or milder manifestations of heat, which we currently try to detect by neck responders and other modern systems.The experiment analyzed the effect of the average monthly temperature and humidity in the stable on the percentage of pregnant cows, in 2017 without the use of neck responders and in 2019, when all cows already had a neck responder. Monitoring was performed in 2017 and 2019 on the private farm GenAgro Řicany, a.s. (GPS 49 ° 12'32.319 N, 16 ° 23'42.666 V). The values of average temperatures and relative humidity were calculated from 15-minute interval recordings of HOBO brand data loggers (Onset), which were placed in the stable, at the height at the withers of the cows without the possibility of influencing the measurements by the cows themselves. The object of monitoring was a herd of approximately 700 cows of Czech Fleckvieh Simmental various lactations. Data on the conception of cows were obtained both from the monthly reports of the breeding organization and from the data of the breeder.Thermal stress can have a long-lasting effect observable for weeks or months after the summer. This is also evidenced by the results of the work, which shows the worsening conception of cows, especially in late summer and autumn. At the same time, the results show a positive effect of the used neck responders, which help with the detection of heat and thus improve the reproduction of the whole herd. Keywords: Czech Fleckvieh Simmental, smart farming, neck responders, reproduction, heat stress References Badinga, L., et al. (1985). Effects of climatic and management factors on conception rate of dairy cattle in subtropical environment. J Dairy Sci , 68, 78–85. Bertipaglia, E. C. A., et al. (2005). Fertility and hair coat characteristics of Holstein cows in a tropical environment . Anim Reprod , 2(3), 187–194. Bridges, P. J. et al. (2005). Elevated temperature (heat stress) in vitro reduces androstenedione and estradiol and increases progesterone secretion by follicular cells from bovine dominant follicles. Domestic Animal Endocrinology , 29, 508–522, https://doi.org/10.1016/j.domaniend.2005.02.017 . Funnell, A. (2015). Robots and the future of agriculture . [cited 2020-10-15]. Available from: http://www.abc.net.au/radionational/programs/futuretense/a-swarmof-agbots/6968940 Jelinek, P., Koudela, K. et al. (2003). Fyziologie hospodařských zviřat . Brno: Mendelova zemědělska a lesnicka univerzita. Rensis, F. D., Scaramuzzi, R. . (2003). Heat stress and seasonal effects on reproduction in the dairy cow – a review. Theriogenology, 60,1139–1151, https://doi.org/10.1016/S0093-691X(03)00126-2 . Schmitt, E. J. et al. (1996). Differential response of the luteal phase and fertility in cattle following ovulation of the first-wave follicle with human chorionic gonadotropin or an agonist of the gonadotropin-releasing hormone. J Anim Sci , 74, 1074–1083, DOI: 10.2527/1996.7451074x Schwab, K. (2016). The fourth industrial revolution . New York: Crown Business. Ustundag, A., Cevikcan, E. (2017). Industry 4.0: managing the digital transformation . New York: Springer Berlin Heidelberg. Velechovska, J. (2016). Monitoring přežvykovani pro efektivnějsi chov . Chov [online]., 8. cislo 18–20 str. [cited 2020-10-15]. Available from: https://www.eurofarm.cz/sites/www.eurofarm.cz/files/u2018/08-2016-chov-priloha_str18-20-eurofarm.pdf Wolfenson, D., Roth, Z., Meidan, R. (2000). Impaired reproduction in heat stressed: basic and applied aspects. Anim Reprod Sci , 60, 535–547, https://doi.org/10.1016/S0378-4320(00)00102-0 .

Can prior exposure to stress enhance resilience to ocean warming in two oyster species?

Securing economically and ecologically significant molluscs, as our oceans warm due to climate change, is a global priority. South eastern Australia receives warm water in a strengthening East Australia Current and so resident species are vulnerable to elevated temperature and marine heat waves. This study tested whether prior exposure to elevated temperature can enhance resilience of oysters to ocean warming. Two Australian species, the flat oyster, Ostrea angasi, and the Sydney rock oyster, Saccostrea glomerata, were obtained as adults and “heat shocked” by exposure to a dose of warm water in the laboratory. Oysters were then transferred to elevated seawater temperature conditions where the thermal outfall from power generation was used as a proxy to investigate the impacts of ocean warming. Shell growth, condition index, lipid content and survival of flat oysters and condition of Sydney rock oysters were all significantly reduced by elevated seawater temperature in the field. Flat oysters grew faster than Sydney rock oysters at ambient temperature, but their growth and survival was more sensitive to elevated temperature. “Stress inoculation” by heat shock did little to ameliorate the negative effects of increased temperature, although the survival of heat-shocked flat oysters was greater than non-heat shocked oysters. Further investigations are required to determine if early exposure to heat stress can enhance resilience of oysters to ocean warming.

Progress and Challenges Related to Thermal Fatigue Research of Super-hard Cutting Tools

A large number of super-hard tools literature has been studied, most of which aimed at tool wear patterns and mechanisms. Researches on thermal lord affecting tools wear are carried out insufficiently and achievements about thermal cracks initiation, propagation are little reported. As existing of elevated temperature and intense heat during cutting processes, super-hard cutting tools thermal fatigue problems are obliged to be faced and some fundamental and unresolved issues need to be answered.

Effects of elevated ambient temperature and local testicular heating on the expressions of heat shock protein 70 and androgen receptor in boar testes

Heat stress damaged spermatogenesis and semen quality, however, the exact molecular mechanism is not clear. The objective of this study was to determine the effects of elevated ambient temperature and local testicular heating on the expressions of heat shock protein 70 and androgen receptor in boar testes. A growing body of evidence demonstrated that germ cell apoptosis can be aggravated by heat stress and androgen deprivation, and at normal temperature, withdrawal of androgen led to germ cell apoptosis. There were no reports that heat stress damaged spermatogenesis has relationship with androgen. In this study, adult boars (Landrace, n = 9) were used and randomly divided into: control group (CON), 20–27 °C; environmental hyperthermia group (EH), 37–40 °C, 3 h/d 42 d; and local testicular heating group (LTH), 42 °C 1 h. After heat treatments, all boars were castrated and the testes were harvested. qRT-PCR and Western Blot results showed that the mRNA and protein levels of heat shock protein 70 and androgen receptor were significantly increased after heat treatments. Immunohistochemistry results showed that heat stress caused a redistribution of heat shock protein 70 from the cytoplasm to the nucleus, and androgen receptor was mainly expressed in Sertoli cells. These results indicated that heat stress promoted the inhibition of heat shock protein 70 on the androgen receptor, suggesting that the possible mechanism of heat stress damaged spermatogenesis and semen quality was that heat stress reduced the sensitivity of testicular cells to androgen by up-regulating heat shock proteins.

Endogenous Ethylene Concentration Is Not a Major Determinant of Fruit Abscission in Heat-Stressed Cotton (Gossypium hirsutum L.).

We investigated the role of ethylene in the response of cotton to high temperature using cotton genotypes with genetically interrupted ethylene metabolism. In the first experiment, Sicot 71BRF and 5B (a lintless variant with compromised ethylene metabolism) were exposed to 45°C, either by instantaneous heat shock or by ramping temperatures by 3°C daily for 1 week. One day prior to the start of heat treatment, half the plants were sprayed with 0.8 mM of the ethylene synthesis inhibitor, aminoethoxyvinylglycine (AVG). In a subsequent experiment, Sicot 71BRF and a putatively heat-tolerant line, CIM 448, were exposed to 36 or 45°C for 1 week, and half the plants were sprayed with 20 μM of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid, (ACC). High temperature exposure of plants in both experiments was performed at the peak reproductive phase (65–68 days after sowing). Elevated temperature (heat shock or ramping to 45°C) significantly reduced production and retention of fruits in all cotton lines used in this study. At the termination of heat treatment, cotton plants exposed to 45°C had at least 50% fewer fruits than plants under optimum temperature in all three genotypes, while plants at 36°C remained unaffected. Heat-stressed plants continued producing new squares (fruiting buds) after termination of heat stress but these squares did not turn into cotton bolls due to pollen infertility. In vitro inhibition of pollen germination by high temperatures supported this observation. Leaf photosynthesis (Pn) of heat-stressed plants (45°C) measured at the end of heat treatments remained significantly inhibited, despite an increased leaf stomatal conductance (gs), suggesting that high temperature impairs Pn independently of stomatal behavior. Metabolic injury was supported by high relative cellular injury and low photosystem II yield of the heat-stressed plants, indicating that high temperature impaired photosynthetic electron transport. Both heat shock and ramping of heat significantly reduced ethylene release from cotton leaf tissues measured at the end of heat treatment but modulating ethylene production via AVG or ACC application had no significant effect on fruit production or retention in heat-stressed cotton plants. Instead, high temperature accelerated fruit abortion by impairing pollen development and/or restricting leaf photosynthesis.

Steel Fiber Reinforced Concrete to Improve the Characteristics of Fire-Resistant Concrete

The effect of strength, weight, and fibers on properties of concrete at different temperatures is highlighted at this research to analyze the compressive strength and modulus of elasticity of steel fiber reinforced concrete (SFRC) on 1% and 1.5% of volume fractions at three temperature levels 200°C, 400°C and 600°C. This study compare the compressive strength and modulus elasticity between normal concrete and SFRC in various volume fraction of steel fiber as reinforcement on elevated temperature heating up to 600°C. Materials were tested to find out the quality of the material before making the concrete specimen. The tests were performed compressive test and modulus of elasticity. The addition of 1% and 1.5% steel fiber in concrete mix is advantageous for concrete. Overall the compressive strength of concrete was increased as the percentage of steel fiber in concrete increases. At 1.5%, steel fiber reinforced concrete showed a better overall residual strength and better crack resistance than non-fiber concrete. The carbonation process for concrete with steel fiber is a little influenced by temperature compare to concrete without steel fiber. The concrete with 1.5 % steel fiber demonstrated the highest compressive and modulus of elasticity value, 23.5 and 17172MPa at 600°C respectively. It is expected that in future concrete having steel fiber will act as a fire protective considerably.

Development of tungsten fibre-reinforced tungsten composites towards their use in DEMO—potassium doped tungsten wire

For the next step fusion reactor the use of tungsten is inevitable to suppress erosion and allow operation at elevated temperature and high heat loads. Tungsten fibre-reinforced composites overcome the intrinsic brittleness of tungsten and its susceptibility to operation embrittlement and thus allow its use as a structural as well as an armour material. That this concept works in principle has been shown in recent years. In this contribution we present a development approach towards its use in a future fusion reactor. A multilayer approach is needed addressing all composite constituents and manufacturing steps. A huge potential lies in the optimization of the tungsten wire used as fibre. We discuss this aspect and present studies on potassium doped tungsten wire in detail. This wire, utilized in the illumination industry, could be a replacement for the so far used pure tungsten wire due to its superior high temperature properties. In tensile tests the wire showed high strength and ductility up to an annealing temperature of 2200 K. The results show that the use of doped tungsten wire could increase the allowed fabrication temperature and the overall working temperature of the composite itself.

Insight of the interface of electroless Ni–P/SiC composite coating on aluminium alloy, LM24

Abstract Electroless nickel composite coatings with silicon carbide, SiC, as reinforcing particles deposited with Ni–P onto aluminium alloy, LM24, having zincating as under layer were subjected to heat treatment using air furnace. The changes at the interface were investigated using scanning electron microscope (SEM) and energy dispersive X-ray (EDX) to probe the chemistry changes upon heat treatment. Microhardness tester with various loads using both Knoop and Vickers indenters was used to study the load effect clubbed with the influence of second phase particles on the coating at the vicinity of the interface. It was observed that zinc was absent at the interface after elevated temperature heat treatment at 400–500 °C. Precipitation of copper and nickel with a distinct demarcation (copper rich belt) along the coating interface was seen with irregular thickness of the order of 1 μm. Migration of copper from the bulk aluminium alloy could have been the factor. Brittleness of the coating was confirmed on heat treatment when indented with Vickers. However, in composite coating the propagation of the microcrack was stopped by the embedded particles but the microcracks continue in the matrix when not interrupted by second phase particles (SiC).

Structure evolutions in a Ti–6Al–4V matrix composite reinforced with TiB, characterised using high energy X-ray diffraction

A titanium matrix composite reinforced with TiB was produced using powder metallurgy. A Ti–6Al–4V alloy was chosen to be the matrix, and 12wt.% of TiB2 was used as the boron source for the solid state formation of TiB. The TiB2 to TiB conversion reaction was studied using an in situ high energy X-ray diffraction technique while heat treating the composite. The TiB2 (space group: P6/mmm) converts into TiB-B27 (Pnma), via TiB-Bf (Cmcm). The metastable character of Bf is confirmed here; it is the first phase formed during the conversion and it progressively converts into B27 during elevated temperature heat treatment. A modification of the phase transformation kinetics in the matrix and of the composite β transus temperature (Tβ=1275°C) was also observed, mainly due to gas contamination and intensive work hardening as a result of the mechanical alloying process used to manufacture the material and to a modification of the matrix equilibria.

Deciphering the inert atmosphere degradation patterns in hybrid silicones

Structurally similar silicone ceramers were synthesized by sol–gel processing of organic silanes. The chemical structures of the hardened ceramer materials were investigated by studying the gaseous products produced during elevated temperature heating. Fourier transformation infra-red (FTIR) spectroscopy and thermogravimetric analysis (TGA) were utilized to study the degradation phenomenon in the ceramers. The pyrolyzed residues were analyzed by Raman and 29Si solid-state nuclear magnetic resonance (SSNMR) and X-ray diffraction (XRD) techniques. The surfaces of the residues were analyzed with a scanning electron microscope (SEM). The results from the characterization techniques were utilized to investigate the degradation mechanisms of the ceramer materials.

Bacterial stress responses as determinants of antimicrobial resistance

Bacteria encounter a myriad of stresses in their natural environments, including, for pathogens, their hosts. These stresses elicit a variety of specific and highly regulated adaptive responses that not only protect bacteria from the offending stress, but also manifest changes in the cell that impact innate antimicrobial susceptibility. Thus exposure to nutrient starvation/limitation (nutrient stress), reactive oxygen and nitrogen species (oxidative/nitrosative stress), membrane damage (envelope stress), elevated temperature (heat stress) and ribosome disruption (ribosomal stress) all impact bacterial susceptibility to a variety of antimicrobials through their initiation of stress responses that positively impact recruitment of resistance determinants or promote physiological changes that compromise antimicrobial activity. As de facto determinants of antimicrobial, even multidrug, resistance, stress responses may be worthy of consideration as therapeutic targets.

Reactive gas atomization processing for Fe-based ODS alloys

Gas atomization reaction synthesis was employed as a simplified method for processing oxide dispersion forming precursor Fe-based powders (e.g., Fe–Cr–Y–Hf). During this process a reactive atomization gas (i.e., Ar–O2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t<50nm) metastable Cr-enriched oxide shell that was used as a vehicle to transport oxygen into the consolidated microstructure. Subsequent elevated temperature heat treatment promoted thermodynamically driven oxygen exchange reactions between trapped films of Cr-enriched oxide and internal (Y, Hf)-enriched intermetallic precipitates, resulting in highly stable nano-metric mixed oxide dispersoids (i.e., Y–Hf–O) that were identified with X-ray diffraction. Transmission electron microscopy and atom probe tomography results also revealed that the size and distribution of the dispersoids were found to depend strongly on the original rapidly solidified microstructure. To exploit this, several oxide dispersion strengthened microstructures were engineered from different powder particle size ranges, illustrating microstructural control as a function of particle solidification rate. Additionally, preliminary thermal–mechanical processing was used to develop a fine scale dislocation substructure for ultimate strengthening of the alloy.

Charge transfer through single molecule contacts: How reliable are rate descriptions?

Background: The trend for the fabrication of electrical circuits with nanoscale dimensions has led to impressive progress in the field of molecular electronics in the last decade. However, a theoretical description of molecular contacts as the building blocks of future devices is challenging, as it has to combine the properties of Fermi liquids in the leads with charge and phonon degrees of freedom on the molecule. Outside of ab initio schemes for specific set-ups, generic models reveal the characteristics of transport processes. Particularly appealing are descriptions based on transfer rates successfully used in other contexts such as mesoscopic physics and intramolecular electron transfer. However, a detailed analysis of this scheme in comparison with numerically exact solutions is still elusive.Results: We show that a formulation in terms of transfer rates provides a quantitatively accurate description even in domains of parameter space where strictly it is expected to fail, e.g., at lower temperatures. Typically, intramolecular phonons are distributed according to a voltage driven steady state that can only roughly be captured by a thermal distribution with an effective elevated temperature (heating). An extension of a master equation for the charge–phonon complex, to effectively include the impact of off-diagonal elements of the reduced density matrix, provides very accurate solutions even for stronger electron–phonon coupling.Conclusion: Rate descriptions and master equations offer a versatile model to describe and understand charge transfer processes through molecular junctions. Such methods are computationally orders of magnitude less expensive than elaborate numerical simulations that, however, provide exact solutions as benchmarks. Adjustable parameters obtained, e.g., from ab initio calculations allow for the treatment of various realizations. Even though not as rigorously formulated as, e.g., nonequilibrium Green’s function methods, they are conceptually simpler, more flexible for extensions, and from a practical point of view provide accurate results as long as strong quantum correlations do not modify the properties of the relevant subunits substantially.

Rapid room-temperature synthesis of nanocrystalline spinels as oxygen reduction and evolution electrocatalysts

Spinels can serve as alternative low-cost bifunctional electrocatalysts for oxygen reduction/evolution reactions (ORR/OER), which are the key barriers in various electrochemical devices such as metal-air batteries, fuel cells and electrolysers. However, conventional ceramic synthesis of crystalline spinels requires an elevated temperature, complicated procedures and prolonged heating time, and the resulting product exhibits limited electrocatalytic performance. It has been challenging to develop energy-saving, facile and rapid synthetic methodologies for highly active spinels. In this Article, we report the synthesis of nanocrystalline M(x)Mn(3-x)O(4) (M = divalent metals) spinels under ambient conditions and their electrocatalytic application. We show rapid and selective formation of tetragonal or cubic M(x)Mn(3-x)O(4) from the reduction of amorphous MnO(2) in aqueous M(2+) solution. The prepared Co(x)Mn(3-x)O(4) nanoparticles manifest considerable catalytic activity towards the ORR/OER as a result of their high surface areas and abundant defects. The newly discovered phase-dependent electrocatalytic ORR/OER characteristics of Co-Mn-O spinels are also interpreted by experiment and first-principle theoretical studies.

Possible optimal configurations for the ZECOMIX high efficiency zero emission hydrogen and power plant

Abstract Coal use for electricity generation will continue growing in importance. In the present work the optimization of a high efficiency and zero emissions coal-fired plant, which produces both hydrogen and electricity, has been developed. The majority of this paper concerns an integration of gasification unit, which is characterized by coal hydrogasification and carbon dioxide (CO2) separation, with a power island, where a high-hydrogen content syngas is burnt with pure oxygen stream. Another issue is the high temperature CO2 desorption. Because of the elevated temperature heat supply, the regeneration process affects the overall performance of ZECOMIX plant. An advanced steam cycle characterized by a medium pressure steam compressor and expander has been considered for power generation. A preliminary study of different components leads to analyze possible routes for optimization of the whole plant. The plant equipped with a CO2 capture unit could reach efficiency close to 50%. The simulations of a thermodynamic model were carried out using the software ChemCAD. This study is a part of a larger research project, named ZECOMIX, led by ENEA (Italian Research Agency for New technologies, Energy and Environment), other partners being ANSALDO and different Italian Universities. It is aimed at analyzing an integrated hydrogen and power production plant.

외력과 열하중을 동시에 받는 판구조의 열-기계적 특성

본 연구에서는 외력과 열을 동시에 받는 판구조에 대하여 구조적 강도를 평가하기 위하여 열응력 해석 및 열기계적 실험을 수행하였다. 초음속 비행체의 날개 유사 모델인 판구조에 대한 열 및 외력 환경구현을 위하여 석영램프를 이용한 복사가열기와 하중부가 시스템을 사용하였으며, 소성을 가미한 탄소성 유한요소 해석을 병행하여 열기계적 거동을 파악하였다. 시험은 외력 유지 상태에서 일정 온도 유지환경과 10 ℃/sec의 가열률 환경하에서 이루어졌다. 해석 및 실험에 의한 결과들을 이용하여 가열환경에 따른 구조물의 거동 특성을 파악하였으며, 상온에서의 구조강도 결과와 비교 고찰하였다. 본 연구를 통하여 초음속 비행체와 같이 외력과 열 환경을 경험하는 구조물에 대한 실험 및 해석적 방법을 제시하였고, 획득된 자료들은 비행체 내열 구조 설계시 열적 강도 판단의 참고자료로 활용될 수 있을 것이다. The thermo-mechanical analysis and test were performed for plate structure under mechanical and thermal loading conditions. Infrared heating system and hydraulic loading system were used to simulate mechanical and thermal environment for the plate structure which is similar to the fin of the airframe. Also, FEM analysis using plastic option was added to evaluate thermo-mechanical behavior. Thermo-mechanical tests were conducted at elevated temperature and rapid heating(10℃/sec) condition with external loading together. To investigate the effect of heating environment, the strength at room temperature was compared with that of elevated temperature and rapid heating condition. A methodology for test and analysis for supersonic vehicle subjected to aerodynamic loading and heating was generated through the study. These experimental and analysis results can be used for designing thermal resistance structures of the supersonic vehicle.