Evaluation Of Thermal Effects Research Articles

Extraction of silver losses at cryogenic temperatures through the optical characterization of silver-coated plasmonic nanolasers.

We report on the extraction of silver losses in the range 10 K-180 K by performing temperature-dependent micro-photoluminescence measurements in conjunction with numerical simulations on silver-coated nanolasers around near-infrared telecommunication wavelengths. By mapping changes in the quality factor of nanolasers into silver-loss variations, the imaginary part of silver permittivity is extracted at cryogenic temperatures. The latter is estimated to reach values an order of magnitude lower than room-temperature values. Temperature-dependent values for the thermo-optic coefficient of III-V semiconductors occupying the cavity are estimated as well. This data is missing from the literature and is crucial for precise device modeling. Our results can be useful for device designing, the theoretical validation of experimental observations as well as the evaluation of thermal effects in silver-coated nanophotonic structures.

Mechanism analysis and evaluation of thermal effects on the operating point drift of servo valves

Mechanism analysis and evaluation of thermal effects on the operating point drift of servo valves

Polysaccharides Used in Biosorbents Preparation for Organic Dyes Retaining from Aqueous Media.

Natural polymers can themselves be efficient as materials with biosorptive properties but can also be used to transform microbial biomass into an easy-to-handle form, respectively, into biosorbents, through immobilization. The article aims to study biosorbents based on residual microbial biomass (Saccharomyces pastorianus yeast, separated after the brewing process by centrifugation and dried at 80 °C) immobilized in sodium alginate. The biosorptive properties of this type of biosorbent (spherical particles 2 and 4 mm in diameter) were studied for removal of reactive dye Brilliant Red HE-3B (with concentration in range of 16.88–174.08 mg/L) from aqueous media. The paper aims at three aspects: (i) the physico-chemical characterization of the biosorbent (Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) and Fourier Transform Infrared (FTIR) spectra); (ii) the modeling of biosorption data in order to calculate the quantitative characteristic parameters using three equilibrium isotherms (Langmuir, Freundlich, and Dubinin–Radushkevich—DR); and (iii) the evaluation of thermal effect and the possible mechanism of action. The results of the study showed that biosorption capacity evaluated by Langmuir (I) model is 222.22 mg/g (ϕ = 2 mm) and 151.51 mg/g (ϕ = 4 mm) at 30 °C, and the free energy of biosorption (E) is in the range of 8.45–13.608 KJ/mol (from the DR equation). The values of thermodynamic parameters suggested an exothermic process due the negative value of free Gibbs energy (ΔG0 = −9.031 kJ/mol till −3.776 kJ/mol) and enthalpy (about ΔH0 = −87.795 KJ/mol). The obtained results underline our finding that the immobilization in sodium alginate of the residual microbial biomass of Saccharomyces pastorianus led to an efficient biosorbent useful in static operating system in the case of effluents with moderate concentrations of organic dyes.

Evaluation of thermal effects on carbon dioxide breakthrough curve for biogas upgrading using pressure swing adsorption

Selective carbon dioxide capture using pressure swing adsorption can transform raw biogas into high energy content biomethane and subsequently sequestration of CO2. In this work, the PSA technology for biogas upgrading is modelled and evaluated using one-dimensional binary mixture adsorption, heat and mass transfer model using Aspen Adsorption™ version 10. This model is validated using experimental data reported previously on zeolite NaUSY, since the CO2 breakthrough curve depicts reasonable agreement. This work considers two heat transfer conditions (gas and gas/solid conductions) to compare their effects on CO2 breakthrough and temperature responses at different positions along the adsorption bed. Three different biogas mixtures are charged over zeolite NaUSY bed to evaluate CO2 concentration on breakthrough curve and bed temperature profile. The influence of axial mass dispersion coefficient on breakthrough characteristics and temperature distribution along adsorption bed is examined. In addition, the effects of cooling outside column wall on CO2 breakthrough curve and bed temperature distribution is also explored. The findings indicate that the heat generated during adsorption possesses influences the adsorption performance rather significantly. Reducing this heat restrains the thermal effects on the breakthrough curves, thereby improving the methane purity and recovery.

Evaluation of Thermal Effects on the Bioactivity of Curcumin Microencapsulated with Porous Starch-Based Wall Material Using Spray Drying

Curcumin was microencapsulated by porous starch using a spray dryer with a particle size between 1.5 and 2.0 µm and subjected to water bath (40–100 °C) and oven heating (150–200 °C) in comparison to non-encapsulated samples. The minimum possible encapsulation rate ranged from 26.75 to 52.23%. A reasonable thermal stability was observed after water bath heating with regard to 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging activity. On the other hand, the increase in oven heating temperature caused significant alterations compared with the control samples (p < 0.05). The encapsulated particles subjected to oven heating at 170 °C demonstrated serious collapse. The DPPH scavenging activity of non-encapsulated curcumin was significantly reduced (p < 0.05) from 48.94% ± 3.72% (control, 0 °C) to 40.42% ± 2.23% (oven heating, 160 °C); however, remained stable for the encapsulated samples (51.18% ± 4.86%–50.02% ± 1.79%) without significant difference (p < 0.05). The ABTS scavenging activity was promoted as a function of the oven heating temperature. Both DPPH and ABTS free radical scavenging activities remained stable after water bath. Nevertheless, the color of microencapsulated curcumin was better preserved in comparison to the controls.

Temperature Sensing and Evaluation of Thermal Effects on Battery Packs for Automotive Applications

In this paper, we introduce the need for real-time temperature monitoring in battery packs used in automotive applications so to have an accurate estimation of battery life and performances. Advanced energy storage management systems should sense operating and ambient temperature of battery packs in order to implement proper strategies to improve the efficiency of charge and discharge processes and to extend battery life. The proposed evaluation technique is based on an innovative and dynamic circuital model, which allows to accurately represent the functioning of a battery pack (in charge and discharge) in the various operating conditions. Each circuital parameter of the model has a well-defined function which highlights its dependence on temperature, state of charge, state of health and number of cells. The model characterization has been made through tests on different battery sets. A climatic chamber has been used to simulate different operating conditions of ambient temperature. The analysis of the parameters evolution in time has led to the identification of an ideal ambient temperature range for the type of batteries under examination in order to improve their performances over time in terms of energy efficiency and extension of useful life.

Evaluation of thermal effects on temperature-sensitive operating force of flow servo valve for fuel metering unit

The temperature-induced variation in operating force of flow control valves may result in performance degradation or even jam faults of fuel metering unit (FMU), which significantly affects the safety of aircrafts. In this work, an analytical modeling approach of temperature-sensitive operating-force of servo valve is proposed to investigate the temperature characteristics in varying temperature conditions. Considering the temperature effects, a new extended model of flow force is built and an analytical model of valve friction is also derived theoretically based on the dynamic clearance induced by thermal effects. The extremum condition of friction is obtained to analyze the characteristic-temperature points where jam faults occur easily. The numerical results show that flow force increases firstly and then decreases as temperature increases under a constant valve opening. The maximum friction of flow servo valve can be uniquely determined when the structural parameters and ambient temperature are given. The worst situation just happens at the characteristic-temperature points, which are linearly related to the axial temperature gradients of valve spool. Such evaluations may give an explanation for the temperature-induced jam faults of vulnerable valves and provide a reference for designers to determine a suitable working-temperature range of valves in practice.

An evaluation of thermal effects on behavior of a concrete arch dam

An evaluation of thermal effects on behavior of a concrete arch dam

Evaluation of Thermal Effects on Cable Forces of a Long-Span Prestressed Concrete Cable–Stayed Bridge

AbstractThe structural temperatures and thermal effects on the cable forces of a long-span cable-stayed bridge with prestressed concrete girders were monitored. The temperatures were distributed as...

Evaluation of thermal effects on the beam quality of disk laser with unstable resonator

In this paper thermal effects of the disk active medium and associated effects on the beam quality of laser are investigated. Using Collins integral and iterative method, transverse mode of an unstable resonator including a Yb:YAG active medium in disk geometry is calculated. After that the beam quality of the laser is calculated based on the generalized beam characterization method. Thermal lensing of the disk is calculated based on the OPD (Optical Path Difference) concept. Five factors influencing the OPD including temperature gradient, disk thermal expansion, photo-elastic effect, electronic lens and disk deformation are considered in our calculations. The calculations show that the effect of disk deformation factor on the quality of laser beam in the resonator is strong. However the total effect of all the thermal factors on the internal beam quality is fewer. Also it is shown that thermal effects degrade the output power, beam profile and beam quality of the output laser beam severely. As well the magnitude of each of affecting factors is evaluated distinctly.

Evaluation of Thermal Effect, Setting Temperature of Plaster and Its Effect on the Softening of Wax on Various Gypsum Products after Adding Additives

Two types of plaster (Al-Ahliyah Plaster and Plaster of Paris) were used as an experimental group and two types of stones (Elite and Silky Rock) represented the control group. In addition, five chemical materials as additives were chosen in this study (gum Arabian, rosin, potassium sulfate, borax and ferric oxide) at 0.25% concentration. One or two of each above additives were added to dental plasters to prepare 1394 samples. This study included the evaluation of the following characteristics: W/P ratio, setting temperatures, setting time. The results of the above measurements were subjected to descriptive analysis (mean and standard deviation). One-way analysis of variance (ANOVA) showed that there is a significant difference among the experimental groups, Duncan’s Multiple Range Test was also used to show the level of significance presented in each group. It is concluded that both types of dental plasters produced setting temperatures are however lower than that of the dental stones (control group) and their setting temperatures are more suitable for wax pattern than that of stone, but with additives, the setting temperature will be increased. This belongs mainly to the changes in the chemical structure of the gypsum. Also the results showed that, the mechanical properties of Al-Ahliyah plaster (local plaster) could be improved by the addition of some additives such as resin and gum Arabian.

Influence of coatings geocement activation energy of thermal oxidative degradation wood

The influence geocement coating on the activation energy thermal-oxidative degradation of wood. These thermogravimetric parameters give ability to determine the rate of thermal decomposition of materials at a predetermined temperature and oxygen concentration in the environment and therefore show a qualitative evaluation of thermal effects and determine the activation energy of thermal degradation. The results of studies of thermal timber and cover, set temperature schedule that wood is 230 oC and the mass loss of samples on which the calculated activation energy, which for heotsementnoho coverage increased 3 times. A study to determine the flammability of wood modified group coverage and set efficiency - lowering the temperature of the flue gases by 1.5 times and mass loss during the test about 8 times.

Evaluation of thermal effects and strain-rate sensitivity in frozen soil

Temperature variation is one important factor that affects the dynamic mechanical properties of frozen soil under impact loading. Thermal damage is a collective phenomenon that can be caused by temperature variation. This paper investigates the effects of thermal damage on strain course. A split Hopkinson pressure bar was employed to investigate the dynamic mechanical characteristics of frozen soil at different temperatures and different strain rates. The stress-strain curves were obtained under impact loading. The compressive strength of frozen soil showed a negative temperature sensitivity and positive strain-rate trend. Specifically, the strength of frozen soil increased with decreasing temperatures and increasing strain rates.

Evaluation of Thermal Effect of PCM Wallboards by Coupling Simplified Phase Change Model with Design Tool

A simplified PCM wallboard model is coupled to an existing design-oriented model of multi-zone buildings. Using a reference model and a basic simulation configuration, the accuracy of the resulting PCM wallboard-building thermal design tool is evaluated. A new performance indicator, called PCM utilization factor, is then proposed in order to estimate the thermal efficiency of using PCM wallboards in buildings. Using this PCM Utilization factor and a degrees-hours indicator, the ability of the PCM wallboard-building thermal design tool to evaluate the effect of PCM wallboards on heating loads and summer thermal comfort in the early design phase of a project is examined in two real case studies: a family house project and an existing office building. The user-friendliness of this design tool, and the short calculation times it leads to when performing a year-long simulation using a standard office computer, make it a well-adapted tool for sensibility studies or multi-criterion optimization for buildings that contain PCM wallboards.

Evaluation of thermal effects due to back-streaming electrons in the IAE RF gun

Back-streaming electrons in thermionic RF guns give a serious thermal effect to a cathode. In this study, the back-streaming beam power onto a thermionic cathode of the IAE RF gun was evaluated quantitatively by using an infrared radiation thermometer. Time evolutions of cathode surface temperature during RF macro-pulse were also calculated by using a simple 1-dimensional heat conduction model and results of a 2-dimensional particle simulation for several methods expected to reduce back-bombardment effect.

Evaluation of Thermal Effects on the Dissolution of a Nonaqueous Phase Liquid in Porous Media

Porous media contaminated with nonaqueous phase liquids (NAPLs) may serve as a long-term source of groundwater contamination. To remove NAPLs and thereby mitigate the potential impact to the environment and human health, it has been suggested that contaminated media be flushed with cosolvents, surfactants, hot water, or steam. In this study, hot water flooding was used to remediate a porous medium contaminated with tetrachlorethylene (PCE) at residual saturation in an otherwise water-saturated medium. The effect of temperature on the physical and chemical properties of the system was well characterized, and a quantitative assessment was made of the effect of temperature on PCE dissolution. A comparison of the results from the dissolution experiments with existing dimensionless correlations for NAPL dissolution in porous media elucidated the role of the aqueous-phase viscosity and the NAPL species aqueous-phase diffusivity. Nonaqueous−aqueous phase mass transfer rate coefficients measured for this system w...

Experimental evaluation of thermal effects on the tensile mechanical properties of pultruded GFRP rods

This work represents a preliminary study of a more articulate research project whose aim is to show the possible applications of pultruded products in civil engineering and, in particular, the substitution of FRP rods in classic concrete structures. We present an experimental procedure to first degrade FRP rods with aligned continuous glass fibres through exposure to elevated temperature and then evaluate the changes in their tensile mechanical parameters. The procedure to expose the rods to heat is defined starting from the specifications contained in ASTM D794-68, while the evaluation of the tensile mechanical parameters was set up in a previous work for analogous undamaged FRP rods. From the observation of the experimental data obtained in this work, it is possible to show the strong effects of heat on the ultimate strength and on the Young's modulus of the material that constitutes the rods. In particular, the ultimate strength shows a constant degradation when the temperature increases. By contrast, the Young's modulus is subject to different changes at different temperature exposures.

Nonstationary heat transfer associated with borehole washing

A solution is obtained to the nonstationary axisymmetric problem of the temperature changes in a liquid which is injected into the borehole through a central (drill or delivery) pipe lowered to the bottom of the bore and expelled to the surface through the annular clearance about the pipe [1, 2]. The borehole, of constant depth L, is drilled in a soil with a natural steady temperature distribution and, prior to injection, is filled with a liquid whose temperature varies in proportion to the geothermal gradient. The liquid is pumped into the central tube at a constant rate Q at a known time-variable temperature. Two example cases are examined. In the first, the liquid enters the pipe at a constant temperature. In the second case, the temperature of the liquid injected through the central pipe is variable and equal to that of the liquid expelled through the annular clearance (closed-cycle circulation). Both problems are of interest in drilling technology and inthe evaluation of thermal effects on the oil bed.