Upper-limit Temperature Research Articles

Thermal properties enforcement of carbonate ternary via lithium fluoride: A heat transfer fluid for concentrating solar power systems

A novel eutectic of Li2CO3-Na2CO3-K2CO3 improved by LiF, when employed as a heat transfer fluid in concentrating solar power systems, is prepared to eliminate the disadvantage of limited operating temperature range and low specific heat as well as thermal conductivity. Using the static melting method, Li2CO3-Na2CO3-K2CO3 with 15.0 wt.% LiF which is simply physical mixture determined by X-ray diffraction, is chosen as the optimized candidate. Results indicate that, at 10 °C/min of heating rate, LiF-Li2CO3-Na2CO3-K2CO3 reached melting point of 368 °C and upper temperature limit of 753 °C, allowing it to be effectively employed in thermal storage and heat transfer in high temperature CSP systems. During temperature range from 400 to 600 °C, the liquid quaternary exhibited notably mean specific heat of 1.917 J/(g·°C), which is larger than that of the original ternary eutectic. Thermal conductivity of solid LiF-Li2CO3-Na2CO3-K2CO3 reached the stable level of 1.021 W/(m·°C) at 320 °C. Density of improved eutectic tested by the archimedean principle is approximately 1.95 g/cm3. In conclusion, LiF-Li2CO3-Na2CO3-K2CO3 can be employed as the admirable heat transfer fluid for thermal storage and heat transfer in high-temperature CSP plants. This investigation will provide useful information for further improvement of molten salt based heat transfer fluids.

High temperature limit of semiconductor nanowire lasers

Nanoscale light sources for intense laser emission based on CdS nanowires provide both an extremely localized emission and an ultrafast response even on sub-ps timescales. These fundamental mechanisms were investigated in the past, and practical device applications, such as on-chip laser driven applications working in different temperature ranges up to values far beyond room temperature, are becoming the focus of research. Here, we present a detailed study of the power dependent performance of CdS nanowire lasers which exhibit four distinct working regimes divided by certain threshold values. These regimes are spontaneous emission, amplified spontaneous emission, lasing, and a regime of vanishing laser oscillations due to active material degradation. The three threshold values bridging these four regimes are evaluated as a function of operating temperature, enabling the determination of an upper temperature limit for stable CdS nanowire lasing, at which the degradation threshold drops below the lasing threshold. Furthermore, the degradation mechanism of the CdS nanolasers will be proposed.

On the effect of temperature on the threshold stress intensity factor of delayed hydride cracking in light water reactor fuel cladding

Abstract Delayed hydride cracking (DHC) was first observed in pressure tubes in Canadian CANDU reactors. In light water reactors, DHC was not observed until the late 1990s in high-burnup boiling water reactor (BWR) fuel cladding. In recent years, the focus on DHC has resurfaced in light of the increased interest in the cladding integrity during interim conditions. In principle, all spent fuel in the wet pools has sufficient hydrogen content for DHC to operate below 300°C. It is therefore of importance to establish the critical parameters for DHC to operate. This work studies the threshold stress intensity factor (KIH) to initiate DHC as a function of temperature in Zry-4 for temperatures between 227°C and 315°C. The experimental technique used in this study was the pin-loading testing technique. To determine the KIH, an unloading method was used where the load was successively reduced in a stepwise manner until no cracking was observed during 24 hours. The results showed that there was moderate temperature behavior at lower temperatures. Around 300°C, there was a sharp increase in KIH indicating the upper temperature limit for DHC. The value for KIH at 227°C was determined to be 2.6 ± 0.3 MPa √m.

Thermal properties and thermal stability of the ternary eutectic salt NaCl-CaCl2-MgCl2 used in high-temperature thermal energy storage process

The ternary eutectic chloride salt (NaCl-CaCl2-MgCl2) was designed and prepared for thermal energy storage over 500°C in a concentrated solar power system. The thermal properties of the eutectic salt were measured experimentally using the Differential Scanning Calorimeter (DSC) technique, and the thermal stability including the long-term and short-term thermal stability of the ternary system was investigated by the Thermo-gravimetric Analyzer (TGA) technique and the DSC technique. The results indicated that the melting temperature and fusion enthalpy were 420.83°C and 201.50J/g, respectively, and the specific heat capacity was 1.49J/(g·°C). In the long-term isothermal stability study, the total weight loss of the eutectic salt was less than 5% below 650°C, and the melting temperature and fusion enthalpy changed slightly as the temperature increased. The ternary eutectic system demonstrated excellent thermal stability below 650°C, which was defined as the upper temperature limit of the ternary system. During the short-term thermal cycling test, the stability and recyclability of the ternary salt were verified in future during the working temperature, generally 50°C lower than the upper temperature limit. The eutectic composition before and after thermal treatment was characterized by the X-ray Diffraction (XRD) technique to analyze the mechanism of thermal instability. The mechanism of thermal instability turned out to be the thermal decomposition of the generated magnesium chloride hexahydrate at high temperature. It was proved that the ternary eutectic chloride salt was a potential candidate for high-temperature thermal energy storage applications up to 650°C.

Upper lethal temperatures for the mussel Mytilus galloprovincialis (Lamarck, 1819), in central coast of Chile

The presence of Mytilus galloprovincialis, widely known as the Mediterranean mussel, have been genetically certified from Coliumo Bay to the Magellan Strait, in central and southern Chile, respectively. To correlate the geographic distribution of this species along the Chilean coast with its physiological tolerance to upper temperatures, experiments were carried out with adults and larval stages. Trochophore, umbonate veliger, and pre-metamorphic larvae were submitted to experimental temperatures from 17-33°C, during 24 h to determine the upper temperature limit. Meanwhile, adult experiments were carried with specimens having different previous physiological background: spring-summer acclimation (November-January), and fall-winter acclimation (August-October) and exposed to temperature range of 17-33°C for period of 24, 48, 72 and 96 h, to verify mortality and byssus formation. Results showed that at larvae stages, the 50% of mortality occurred at 27°C, with 100% mortality at 30°C. Adult stages reached the 55% mortality exposed for 48 h at 30°C and 100% mortality in 72 h at the same temperature. The byssus secretion become failing at 27°C and ceased at 30°C.

A Prospective analysis on Minimization of Mechanical Friction of Fuel Engine using Chemical Reagents

Chemical reagents such as Lithium base grease, Calcium base grease, Aluminum base grease which are reduced the mechanical friction and increase the performance of machines with adding various additives molybdenum disulphide (MoS2), Graphite, Boron Nitrite. Dropping point is an indicator of heat resistance of the grease. The dropping point indicates the upper temperature limit at which grease retains its structure. If, failure the grease against high temperature then occurs friction and increase load. When load is increase then the fuel engine does not give the satisfy output. The paper estimated the dropping point of those grease. A.S.T.M standard D-566 used for estimated dropping of the greases. The dropping point of Lithium base grease, Calcium base grease, Aluminum base grease are estimated 195°C, 95°C, and 110°C respectively. The dropping point of mixed base grease i.e., Calcium 50% + Lithium 50%, Lithium 50% + Aluminum 50% and Calcium 50% +Aluminum 50% are 140°C, 158°C and 152°C respectively. The dropping of mixed base grease is higher than the individuals of the greases. The use of the calcium base grease also act is a water and repellant and corrosion protective. This paper represents that Aluminum 50% + Calcium 50% mixed base grease is showing the best performance against high temperature with protects the corrosion.

The Analysis of Outdoor Thermal Comfort in Guangzhou during Summer

1582 valid questionnaires are collected though testing method of field environment parameters and subjective questionnaire survey to investigate and analysis the outdoor thermal environment in Guangzhou area. As questionnaires shown, the neutral temperature of PET is 24.41℃, the upper temperature limit that 90% respondents accept is 30.97℃, which is much higher than the existing standards, while the desired temperature is 23.65℃ via establishing Logistic regression model. As the result of comparing the differences of gender in thermal comfort, women are more sensitive than man in a sense of slightly stronger radiation, the effect value of 15%. Analysis of the correlation between the elements shows the different degrees of impact from environmental parameters to actual thermal sensation and thermal expectations, While establishing the model of thermal sensation and environment parameters by stepwise regression, it emphasizes enormous potential of the initiatives in improving the thermal environment in summer outdoor, such as increasing air flow and improving shade conditions.

Simulation of temperature effect on the structure control of polystyrene obtained by atom-transfer radical polymerization

This paper uses a new kinetic modeling and simulations to analyse the effect of temperature on the polystyrene properties obtained by atom-transfer radical polymerization (ATRP). Differently from what has been traditionaly published in ATRP modeling works, it was considered “break” reactions in the mechanism aiming to reproduce the process at high temperatures. Results suggest that there is an upper limit temperature (130 °C), above which the polymer architecture loses the control. In addition, for the system considered in this work, the optimum operating temperature was 100 °C, because at this temperature polymer with very low polydispersity index is obtained, at considerable fast polymerization rate. Therefore, this present paper provides not only a tool to study ATRP processes by simulations, but also a tool for analysis and optimization, being a basis for future works dealing with this monomer and process.

ANALYSIS OF THERMAL AND AERODYNAMICS PERFORMANCE OF BATAK TOBA TRADITIONAL HOUSE BY IMPLEMENTING DIGITAL SIMULATION AND FIELD MEASUREMENT

Traditional house is believed to have a better thermal performance compared to the modern house. Utilization of passive design in buildings can refer to the passive system used in a traditional house through natural ventilation and local materials application. Digital simulation was used to evaluate the thermal performance of the Batak Toba Traditional House by comparing field measurement data; and as a validation tool. This study aims to determine the thermal and aerodynamic performance of Batak Toba Traditional House by using digital simulation and field measurements. The used method was by comparing the results of digital simulation analysis with indoor and outdoor direct temperature measurements of the Batak Toba Traditional House. The softwares used for simulation were Meteonorm, Ecotect and CFD-ACE+. The measurements were conducted for 24 hours in May 4th-5th and April 26th-27th 2013 within one hour time interval. The results of the analysis of digital simulation show the same phenomenon compared with the result of field measurement that is 80% in range thermal comfort within one year. Field measurement results showed that the thermal conditions resulted from all day field measurement was under the upper limit temperature reference of thermal comfort with natural ventilation, that is 29 °C.

Active-passive combined and closed-loop control for the thermal management of high-power LED based on a dual synthetic jet actuator

In order to better solve the thermal management of high-power LED and facilitate its miniaturization, an active-passive combined heat dissipation method based on a dual synthetic jet actuator (DSJA) is proposed. Comparative analyses on heat dissipation characteristics and installation-space reductions of nine thermal management schemes are carried out. The results indicate that the temperature rapidly decreases and stabilizes once the actuator is activated. The heat dissipation effect based on DSJA is better than that based on synthetic jet actuator (SJA). The combination method with the vertical layout of DSJA makes the stable temperature of the LED and the installation space decrease 16°C and 72.3% with respect to the commercial heat sink. Furthermore, a closed-loop system based on the combination method is developed to realize the autonomous control of the LED temperature within a setting temperature range. It is concluded that the operation duty cycle (ODC) reduces with the increase of the upper limit temperature, and there is an optimal impingement distance where the ODC is lowest of 29.1%. The closed-loop control will be greatly useful for the adaptive thermal management of electronic devices.

Defining boundaries for the distribution of microbial communities beneath the sediment-buried, hydrothermally active seafloor.

Subseafloor microbes beneath active hydrothermal vents are thought to live near the upper temperature limit for life on Earth. We drilled and cored the Iheya North hydrothermal field in the Mid-Okinawa Trough, and examined the phylogenetic compositions and the products of metabolic functions of sub-vent microbial communities. We detected microbial cells, metabolic activities and molecular signatures only in the shallow sediments down to 15.8 m below the seafloor at a moderately distant drilling site from the active hydrothermal vents (450 m). At the drilling site, the profiles of methane and sulfate concentrations and the δ13C and δD isotopic compositions of methane suggested the laterally flowing hydrothermal fluids and the in situ microbial anaerobic methane oxidation. In situ measurements during the drilling constrain the current bottom temperature of the microbially habitable zone to ~45 °C. However, in the past, higher temperatures of 106-198 °C were possible at the depth, as estimated from geochemical thermometry on hydrothermally altered clay minerals. The 16S rRNA gene phylotypes found in the deepest habitable zone are related to those of thermophiles, although sequences typical of known hyperthermophilic microbes were absent from the entire core. Overall our results shed new light on the distribution and composition of the boundary microbial community close to the high-temperature limit for habitability in the subseafloor environment of a hydrothermal field.

Corrosion Rate of the X2CrNiMoN22-5-3 Duplex Stainless Steel Annealed at 500 cc

The X2CrNiMoN22-5-3 duplex stainless steel has an austenitic-ferritic microstructure with an average fraction of each phase of approximately 50%. At the duplex stainless steel the nitrogen serves to significantly improve the corrosion resistance of the alloy also in the welded condition. These steels present the excellent corrosion resistance of austenite steel, and the high mechanical behaviour of ferrite steel. However, the performance presented by duplex stainless steels can be drastically reduced by undesirable phases, such as sigma phase, chi phase, secondary austenite and a lot of chromium-rich and carbides precipitates. In this case an upper temperature limit of 300 C has been placed in the use of X2CrNiMoN22-5-3 steel in the industry mainly due to 475 C embrittlement. The purpose of this work was to ascertain how 60 min isothermal heat treatments at 500 C and corrosion time influence on the relative mass loss, profile roughness parameters and endothermal process by dynamic scanning calorimetry curves of heating measurement from 400 to 600 C of X2CrNiMoN22-5-3 duplex stainless steel. The influence of boiling nitric acid on the steel corrosion resistance was investigated using weight loss and profile roughness parameters. DOI: 10.12693/APhysPolA.130.993 PACS/topics: 81.40.‐z

Responses of the arcto-boreal krill species Thysanoessa inermis to variations in water temperature: coupling Hsp70 isoform expressions with metabolism.

Recent studies have indicated a metabolic temperature sensitivity in both the arcto-boreal krill species Thysanoessa inermis and Thysanoessa raschii that may determine these species' abundance and population persistence at lower latitudes (up to 40° N). T. inermis currently dominates the krill community in the Barents Sea and in the high Arctic Kongsfjord. We aimed to increase the knowledge on the upper thermal limit found in the latter species by estimating the CT50 value (19.7°C) (critical temperature at which 50% of animals are reactive) and by linking metabolic rate measurements with molecular approaches. Optical oxygen sensors were used to measure respiration rates in steps of 2°C (from 0 to 16°C). To follow the temperature-mediated mechanisms of passive response, i.e., as a proxy for molecular stress, molecular chaperone heat shock protein 70 (Hsp70) sequences were extracted from a transcriptome assembly, and the gene expression kinetics were monitored during an acute temperature exposure to 6 or 10°C with subsequent recovery at 4°C. Our results showed upregulation of hsp70 genes, especially the structurally constitutive and mitochondrial isoforms. These findings confirmed the temperature sensitivity of T. inermis and showed that the thermal stress took place before reaching the upper temperature limit estimated by respirometry at 12°C. This study provides a baseline for further investigations into the thermal tolerances of arcto-boreal Thysanoessa spp. and comparisons with other krill species under different climatic regimes, especially Antarctica.

ECO2N V2.0: A TOUGH2 fluid property module for modeling CO2‐H2O‐NACL systems to elevated temperatures of up to 300°C

AbstractWe have improved ECO2N, the TOUGH2 fluid property module of the CO2‐H2O‐NaCl system. The major enhancements include: (i) the upper temperature limit is increased from 110 to about 300°C; (ii) the thermophysical properties of the CO2‐rich phase are more accurately calculated as a non‐ideal mixture of CO2 and H2O; (iii) the approach to calculate the specific enthalpy of dissolved CO2 has been improved to make the code more robust in modeling phase transitions under non‐isothermal conditions; and (iv) more sophisticated models for effective heat conductivity of formations saturated with supercritical CO2 have been provided. The new module includes a comprehensive description of the thermodynamic and thermophysical properties of H2ONaClCO2 mixtures, that reproduces fluid properties largely within experimental error for the temperature, pressure and salinity conditions 10°C < T < 300°C, P < 600 bar, and salinity up to halite saturation. This includes density, viscosity, and specific enthalpy of fluid phases as functions of temperature, pressure, and composition, as well as partitioning of mass components H2O, NaCl and CO2 among the different phases. ECO2N with the TOUGH2 reservoir simulator can be applied to a wide range of problems in geologic sequestration of CO2 in saline aquifers, and in enhanced geothermal reservoirs. ECO2N can describe both sub‐ and supercritical states of CO2, but applications that involve subcritical conditions are limited to systems in which there is no change of phase between liquid and gaseous CO2, and in which no mixtures of liquid and gaseous CO2 occur. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.

A locus in Pristionchus pacificus that is responsible for the ability to give rise to fertile offspring at higher temperatures.

ABSTRACTTemperature is a stress factor that varies temporally and spatially, and can affect the fitness of cold-blooded organisms, leading to a loss of reproductive output; however, little is understood about the genetics behind the long-term response of organisms to temperature. Here, we approach this problem in the model nematode Pristionchus pacificus by utilising a large collection of natural isolates with diverse phenotypes. From this collection we identify two strains, one from California that can give rise to fertile offspring up to 28°C and one from Japan that is fertile up to 30°C. We show that the optimum temperature and the upper temperature limit for fertility is shifted higher in the Japanese strain suggesting that there is a mechanism that controls the temperature response of fertility across a range of temperatures. By crossing the two strains, and using genetic mapping, we identify a region on chromosome V that is responsible for maintaining fertility at higher temperatures. Thus, we conclude that fitness of P. pacificus at high temperature is under genetic control, suggesting that it could be subject to natural selection.

Li-Ion Batteries Operating from Room Temperature to 150 °C

Commercially available Li-ion batteries have limited thermal stabilities, with safe operation range limited to about 80 oC. Nevertheless, several industries, as aerospace, oil & gas, military and biomedical, require operations to be performed at extreme environments, with peak temperatures reaching 120-150 oC and above. The market for specialty batteries is currently dominated by primary cells, raising safety concerns, requiring extensive maintenance and limiting the power output of the energy storage units. The development of a Li-ion battery that fulfills the safety and cycle life requirements for these applications is a challenging scientific problem and a great market opportunity. The ubiquity of organic solvents in the vast majority of Li-ion cells greatly limits the temperature range, due to the volatility of the electrolyte. The use of ionic liquids has been proposed as an alternative to extend the thermal stability of batteries, but there are no thin film separators capable of offering the required mechanical stability at high temperatures. Similar problems are faced by polymer electrolytes, where volume change and thermal aging decrease cycle life of devices upon long exposure to high temperatures. While solid state ceramic electrolytes possess the desired stability at elevated temperatures, their poor interfacial and wetting properties tend to limit their use to thin film configurations. None of the electrolyte systems currently used meets the requirements for proper operation of large scale devices up to very high temperatures. To tackle this issue we developed a gel-like composite electrolyte containing hexagonal boron nitride (BN) and a solution of LiTFSI in the ionic liquid 1-methyl-1-propylpiperidinium bis(trifluormethane)sulfonimide (PP13). The BN acts as a binder, providing mechanical sustentation even at elevated temperatures, while the ionic liquid offer a medium for ion transport. The ionic conductivities ranged from 0.2 mS/cm at room temperature to 4 mS/cm at 150 oC, with an average Li-ion transference number of 0.10. The electrolyte held remarkable electrochemical stability even at 120 oC, presenting an anodic stability of 5.5 V and a reversible lithium plating/stripping behavior. Tests on a half-cell configuration using Lithium Titanate (LTO) showed negligible capacity fade for testing periods over a month at 120 oC, with high coulombic efficiencies attained. The accelerated lithiation kinetics at high temperatures allowed operation even at a high 3C rate, with great capacity retention even for 600 cycles. The half-cells were able to provide stable performance even at 150 oC, showing the superb electrochemical and thermal stability of the electrolyte system. The cells were still functional at room temperature, providing 60% of the full capacity, showing that our electrolyte system presents a record upper temperature limit for a Li-ion cell that can also operate at 25 oC. Preliminary tests on a full-cell configuration at 120 oC using LTO and Li1+xMn2O4 yielded good cyclic stability, with a capacity of 70 mAh/g and a voltage output of 2.2 V. The BN-PP13-based composite showed exciting and so far unmatched performance even at highly extreme conditions. Nevertheless, the development of a proper electrolyte system to allow high temperature operation of Li-ion batteries is just the first step of many. The level of performance required for commercial applications will only be achieved with optimization of all device components, including electrode binders and cell packaging.

Griffiths like phase in nanocrystalline manganite La0.50Ca0.50MnO3 studied by magnetic susceptibility and electron spin resonance

The Griffiths like phase embedded into paramagnetic matrix of mixed valence orthorhombic nanocrystalline manganite La0.50Ca0.50MnO3 is experimentally studied by means of sensitive magnetic susceptibility and electron spin resonance. A comparative study of the nano- and polycrystalline manganites indicates the temperature interval of the Griffiths like phase located above the Curie temperature of nanocrystalline one. The upper temperature limit for an existence of Griffiths like phase, revealed by the sensitive electron spin resonance, is 10 K higher than that of the magnetic susceptibility. This proves that the high frequency field is able to excite the relatively smaller magnetic clusters.

Comparative thermal study between conventional and bioclimatic office buildings

The presented research focuses on the comparison of energy performance of a conventional versus a bioclimatic building, both continuously monitored. Attached buildings of offices located in Madrid, with main orientation N-S, have been built considering different constructive criteria. Principal Components Analysis has been used to check the representativeness criteria of the analysed offices. The Box and Whisker method concluded that the bioclimatic building has registered lower inter-quartile ranges for indoor temperatures than the convectional building. Thermal oscillations have been calculated for both buildings during winter and summer campaigns. The behaviour of the bioclimatic building is close to the summer thermal comfort band however during winter period values are slightly above because upper temperature limit has been exceeded. Thermal assessment of monitored offices has been done for representative days of summer and winter periods. The temperature variation of bioclimatic offices is more stable compared to conventional ones. Global primary energy consumption has been reduced from 124.58 kWh/m2 year in conventional building up to 80.84 kWh/m2 year in bioclimatic building.

BÖHLER T504

Abstract Böhler (or Boehler) T504 (UNS S42200) is a creep resisting steel, hardened and tempered. Usual upper temperature limit for continuous operating is 580 C (1076 F). This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on high temperature performance as well as heat treating, machining, and joining. Filing Code: SA-751. Producer or source: Böhler Edelstahl GmbH & Company KG.

Super Stable Ferroelectrics with High Curie Point.

Ferroelectric materials are of great importance in the sensing technology due to the piezoelectric properties. Thermal depoling behavior of ferroelectrics determines the upper temperature limit of their application. So far, there is no piezoelectric material working above 800 °C available. Here, we show Nd2Ti2O7 with a perovskite-like layered structure has good resistance to thermal depoling up to 1400 °C. Its stable behavior is because the material has only 180° ferroelectric domains, complex structure change at Curie point (Tc) and their sintering temperature is below their Tc, which avoided the internal stresses produced by the unit cell volume change at Tc. The phase transition at Tc shows a first order behavior which involving the tilting and rotation of the octahedron. The Curie – Weiss temperature is calculated, which might explain why the thermal depoling starts at about 1400 °C.