Temperature Reduction Factor Research Articles

A general unified method for calculating fire resistance of CFST columns considering various types of steel and concrete

Due to the advantages of CFST structures, various types of steel (e.g., ordinary/high strength/stainless steel, etc.) and concrete (e.g., ordinary/high strength/ultra-high performance/recycled concrete, etc.) are used in them, and fire safety design is an indispensable part in the structural design of CFST. However, there is still a lack of a simple unified fire design method that can consider different materials and their combinations at the same time. Based on the unified calculation method of fire resistance of CFST based on average temperature proposed by the authors, this paper focuses on enhancing the generality and accuracy of the unified method, with specific attention paying to the prediction of material properties degradation effect and cross-sectional average temperature under fire. For the prediction of material properties degradation effect with considering various types of steel and concrete, two methods, namely the global equivalent method and the segmented equivalent method, are proposed to convert arbitrary temperature reduction factor models defined at material level to the corresponding equivalent models defined at CFST section level. After validating with various types of steel and concrete material properties reduction factor models given in the previous literature, it turns out that the equivalent models generated by the two methods can well approximate the temperature-induced degradation effect at CFST section level. As for the prediction of average temperature with considering various types of steel and concrete, an incremental calculation method to calculate the average temperature of steel tube and concrete core is proposed, which is compatible with various thermal property models for different types of steel and concrete without any intermediate conversion techniques. In the meantime, this incremental calculation method can be adopted for CFST members with or without protection and is also consistent with the temperature calculation formulas for steel structures given in Code. In conclusion, the improvements made in this paper can expand the application scope of the previously proposed unified method to various types of concrete materials and thus enhance the generality of the method.

Thermal and Optical Properties of the Sunspace Casing as Factors Influencing Temperature Rise in Greenhouse Systems.

In sunspaces, there is an observable temperature rise above the external air temperature, caused by solar gains and the buffering effect of their enclosure. In addition, their external partitions form a barrier preventing the direct influence of the external environment and delaying the natural deterioration of elevation surface. In the paper, the temperature rise in a glazed balcony attached to a typical flat in a multifamily building, together with the energy demand in the living zone, were assessed with the use of dynamic computer simulations. Ten variants of the sunspace casing were analysed, with different thermal and solar energy transmittance of the glazing (which is a novel subject in the research area). This enabled us to evaluate average values of the temperature reduction factor during the year and to choose the most efficient variant of the sunspace external partitions. It turned out to be an insulated, double-glazed casing with a spectrally selective coating (type O 21), combining high insulative properties with high solar transmittance. These features allowed the temperature in the sunspace to rise by almost 10°C (compared with the external air) and lower total energy demand in the flat by 33% (compared with a flat with an open balcony).

Glazed balconies and their influence on the temperature reduction factor during the heating season

Glazed buffer spaces have an important influence on the energy performance of buildings, especially in the case of dwellings located in multi-family buildings. The ability to utilize solar radiation during the heating season can be assessed with the use of the temperature reduction factor, expressing the relative temperature rise in the solar space above the outside air temperature. The paper is based on the results of the internal temperature monitoring in dwellings with glazed balconies of different envelope construction and airtightness. The dwellings were located in buildings in Lublin and Zamość, cities in the eastern part of Poland. The measurements took place from July 2017 until September 2018, and the temperature was recorded with the use of iButton sensors. The measurement results were supplemented with the weather data coming from the database of the Polish Institute of Meteorology and Water Management. Thanks to the collected data it was possible to calculate the temperature reduction factor during the subsequent months of the heating season, and to check its relationship with the factors such as the balconies’ orientation, envelope construction and airtightness or the glazing type. The analyses also included the calculation of heat losses reduction achieved thanks to the solar spaces.

Temperature reduction factor for compressive strength parallel to the grain

The aim of this work is to evaluate the effect of the temperature on the compressive strength parallel to grain of Schizolobium amazonicum, Eucalyptus saligna and Pinus taeda from cultivated forests. The Schizolobium amazonicum sample was formed by 105 clear specimens assembled in 15 groups, the Eucalyptus saligna and Pinus taeda were formed by 150 clear specimens assembled in 15 groups each. Each group of samples was formed by 7, 10 and 10 specimens, respectively. The specimens were tested in a temperature range from 20 to 230°C. The Schizolobium amazonicum, Eucalyptus saligna and Pinus taeda samples present a decrease in the compressive strength, reaching 70%, 79% and 62% of the compressive strength at room temperature, respectively. The compressive strength decrease of the samples can be associated to the thermal degradation of wood polymers and the moisture content.

Stripping of ethanol with CO2 in bubble columns: Effects of operating conditions and modeling

Despite being well established, a major limitation remains in ethanol fermentation processes: the presence of ethanol inhibits yeast activity, affecting the cell growth rate and, consequently, the ethanol production rate. For this reason, low ethanol concentrations of around 8–9% v/v are reached at the end of the fermentation, hence requiring the consumption of a significant amount of energy for recovery of the fermentation product, while generating large amounts of vinasse. This situation requires the use of large fermentation tanks in order to achieve satisfactory ethanol production. Additionally, due to the large amount of heat generated by the fermentation processes, the temperature control of industrial fermentation tanks is a great challenge in tropical regions such as Brazil. The goal of the present study was to analyze the influence of operating variables on the performance of ethanol stripping at bench and pilot scales, using carbon dioxide as the carrier gas, and to propose a model describing the changes in ethanol mass and solution temperature during the stripping process. Bench scale experiments were conducted using a 5-L bubble column filled with 10% v/v hydroalcoholic solution, and the pilot scale experiments were performed using a 95-L column filled with industrial fermented wine without yeast. A factorial design was applied to identify the most important operating variables for the following stripping performance parameters: entrainment factor, concentration factor, and temperature reduction factor. The results showed that both temperature and entrainment factor were positively influenced by initial solution temperature and specific CO2 flow rate, and negatively affected by height-to-diameter ratio. The temperature of the carbon dioxide did not affect either of these performance parameters. The simulation results revealed that the stripping model accurately described the decreases in ethanol mass and solution temperature during the stripping operation, with good agreement between the experimental and simulated data, and errors less than 5% in most cases.

A Model to Extract Wind Influence From Outdoor IR Thermal Inspections

A model proposal to determine the influence of wind over temperature measurements when conducting outdoor infrared (IR) themographic inspections is addressed in this paper. A wind velocity-dependent temperature reduction factor is developed and applied in order to estimate the target temperature in the absence of wind, which is considered as the worst case. The model makes use of only two unknown coefficients that are determined for each application. The proposed model is applied and compared to data available in the technical literature.

High-Temperature Properties of CO<sub>2</sub> Mixed with N<sub>2</sub>

Concerning CO2 and its mixture with N2 at a concentration of 0.2, an enthalpy h, a specific heat CP, an electrical conductivity σ and a thermal conductivity κ at temperatures of 300-20,000K were obtained to find out effect of N2 addition on these high-temperature properties. For comparison, similar determination was also performed for CO2-O2 mixture. Admixing N2 and O2 with CO2 proved to result in significant variation in CP and κ in a temperature range from 5,000 to 10,000K. The temperature reduction factor was furthermore derived to find out the property as the arc-quenching gas. This evaluation led to the suggestion that adding N2 to CO2 achieves rapid decay in an interrupting arc temperature in a range from 7,000 to 11,000K, while admixing O2 with CO2 produces rapid diminishing effect on the interrupting arc temperature in a range from 5,000 to 9,000K. An attribution analysis successfully gave the fact that these effects on rapid decay in the temperature arise from variation in CP due to N2 and O2 additions, furthermore from the reactions 2N⇔N2 and C+O⇔ CO.

항공기 엔진 지지구조물의 피로수명 해석에 관한 연구

항공기 구조는 신뢰성 보장을 위해 피로하중에 대한 수명예측이 중요한 분야로 고려되고 있다. 본 논문에서는 항공기 비행안전과 가장 밀접한 엔진 지지구조물을 대상으로 S-N 곡선과 등가응력을 이용하여 선형누적손상 이론을 적용한 피로수명 해석을 수행하였다. 내추락 하중 조건에서 정적강도 해석의 최대응력은 가위형 링크부위에 1,080㎫를 나타내었으며, 이는 온도감소계수를 적용한 허용응력보다 약 5%의 여유를 가지고 있다. 피로하중 조건에서 최대응력은 가위형 링크 부위에 876㎫로 가장 높았으며, 이 때 응력방정식 계수도 0.019㎫/N으로 최대를 나타내었다. 피로수명 해석에 의한 안전수명은 가위형 링크 상단부에 있는 프레팅 영역이 416,667H이고, 다른 부위는 무한수명이 산출되어, 항공기 엔진 지지구조물(가위형 링크, 직선형 링크)은 피로수명 요구도를 충족하는 것으로 확인되었다.

Mechanical properties of PTFE coated fabrics

This article presents the mechanical properties of PTFE coated fabrics used in Central axis roof of Shanghai Expo. First, groups of off-axial and biaxial tensile tests are carried out, and the failure mechanism and strength criterion are studied. Then, on-axial samples are tested under different strain rates, and the relationship between strain rates, tensile strength, and strain at break are determined. Finally, the effects of temperature on mechanical properties are studied. Results show that PTFE coated fabrics are typically orthotropic and its strength can be predicted by the Tsai—Hill strength criterion. The tensile strength and strain at break show linear with the strain rate’s logarithm. The temperature has little effect on the mechanical properties and the temperature reduction factor is proposed for the design and analysis.

Thermodynamic Properties at High Temperatures and Particles Present After Arc Extinction in CO2-CF3I Mixture

Fundamental investigations were carried out to find out the admixing influence of CF3I to CO2. Firstly, thermodynamic properties at 0.1MPa were derived in a temperature range of 300-30,000K for various CF3I-concentrations XCF3I. Secondly, from the thermodynamic properties, a temperature-reduction factor was determined as a function of the temperature for different XCF3I. This determination led to the suggestion that admixture of CF3I to CO2 at XCF3I above 0.9 can produce a rapid effect on decay in the temperature of an extinguishing arc. Finally, the principal particles present after an arc extinction were obtained in consideration of the phase transformation of iodine molecules at 0.1MPa. For instance, the principal particles proved to be CO2, CF4 and CO in the gaseous phase and I2 in the solid phase for XCF3I of 0.01-0.94.

Solution of facility layout problems with pickup/drop-off locations using random search techniques

Due to non-polynomial hardness, the facility layout problem (FLP) becomes more critical when pickup/drop-off (P/D) locations are considered in the design of an open field layout under a manufacturing environment. This paper proposes an indigenous model of the facility layout problem based on random search techniques and its solution methodology using a genetic algorithm (GA), simulated annealing (SA) and a hybrid algorithm (HA). The paper illustrates the performance of different random search operating parameters in solving the facility layout problem considering P/D locations along the periphery of rectangular machine blocks. The preliminary experiments were carried out on three facility layout test problems having six, eight and ten machines in order to fix the different operating parameters such as crossover operator, crossover rate, initial temperature, temperature reduction factor, number of generations, population size, etc. The results of extensive preliminary experimentation were utilized to solve facility layout problems having 12 and 18 machines and, finally, were compared with the existing procedures in the literature. The experimental tables and related analysis performed via the solution methods by applying GA, SA and HA revealed that random-search-based modeling of FLP considering P/D and its solution as suggested in this paper is worth pursuing.

Estimation of the cyclotron mass from the de Haas–van Alphen oscillation in the two-dimensional and quasi-two-dimensional multiband systems

It is known that a cyclotron mass is obtained by fitting a temperature dependence of the Fourier harmonics of the de Haas--van Alphen oscillation to the temperature reduction factor in the Lifshitz-Kosevich (LK) formula in which the oscillation of the chemical potential is neglected. The LK formula, however, should be applied carefully in two-dimensional (2D) and quasi-two-dimensional (Q2D) systems at low temperatures, where the magnetic-field dependence of the chemical potential cannot be neglected. We compare the effective cyclotron mass, which is estimated by using the temperature reduction factor for the fixed chemical potential, with the cyclotron mass of the system. The cyclotron mass is fairly well obtained in 2D single-band systems when the density of states of the reservoir is negligible or much larger than the density of states of the 2D band. On the other hand, if the reservoir has the same order of the density of states as the 2D band, the effective cyclotron mass is shown to be estimated about 7% larger at low temperature and high field. In the 2D multiband systems the effective cyclotron mass for the heavier mass is underestimated about 9%, while the lighter effective cyclotron mass is obtained with very small errors.

Iterative calculation of relaxation spectrum from free vibration data

AbstractThe complex elastic modulus G*(ω) = iG′(ω) + iG′(ω) is shown to be a function not only of the frequency (ω) but also of the damping factor a if the strain is of the form x = x0 exp {− at} sin ωt. The general equations for G*(ω,a) = G′(ω,a) + iG″ (ω,a) = are derived in terms of the relaxation spectrum. The use of a spring to aid the specimen and reduce the ratio a/ω is discussed, and its desirability demonstrated. If data are thus available in terms of either G″(ω) or G″(ω,a) the iterated second approximation of Ninomiya and Ferry provides a rapid and powerful method of finding the relaxation spectrum. To the accuracy to which the time–temperature reduction factor aT is known or can be predicted by means such, for example, as the WLF equation, the function G″(ω,a) over a temperature range at nearly constant frequency can be translated into terms of G″(ω,a) at constant temperature and varying frequency. In such cases, the relatively simple torsional pendulum, or some analogue of it, can economically provide a characterization of the viscoelastic behavior of the material over an extended time or frequency range.