Multi-temperature Method Research Articles

Design of operational temperature for immobilized glucose isomerise using an accelerated inactivation method

Abstract Thermal inactivation of immobilized glucose isomerase in a concentrated glucose solution was investigated in the batch mode and temperature range of 83–95 °C, which is substantially higher than the temperature used in the industrial production of high-fructose corn syrup. Simultaneous evaluation of all inactivation data showed that first-order kinetics with the Arrhenius temperature dependence of the rate constant provided a good approximation of the biocatalyst stability under the investigated conditions. The model parameters were then used to predict the operational temperature for this biocatalyst in the production of high-fructose corn syrup based on the set operational life-time of the biocatalyst. The simulation predicted a window of operational temperature of 60–65 °C, which corresponds very well with the industrial applications of this biocatalyst. This observation demonstrates that the multi-temperature method of enzyme inactivation can provide a good estimate of biocatalyst process stability and is thus a useful tool in the development of biocatalytic processes.

Estimation of fracture toughness of 16MnDR steel using Master Curve method and Charpy V-notch impact energy

16MnDR steel is widely used as a low temperature pressure vessel steel in China. However, the fracture toughness of this steel significantly decreases with the decrease of temperature in the ductile to brittle transition region. To prevent the occurrence of brittle fracture, the methods which can precisely estimate the fracture toughness of 16MnDR steel are of great practical significance. In this paper, the Master Curve method, and empirical formulas between Charpy V-notch impact energy and fracture toughness are applied to estimate the fracture toughness of 16MnDR steel in the transition region. The reference temperature T0 values are determined using both single-temperature and multi-temperature method from fracture toughness test data and Charpy impact test data. The T0 values determined from different combinations of test temperatures are compared. It is found that the fracture toughness of 16MnDR steel can be well estimated using the Master Curve method in the transition region and lower shelf region. The predicted fracture toughness values obtained by empirical formulas cannot be directly used in structural integrity assessment of 16MnDR steel. The effective methods to accurately estimate fracture toughness in the transition region under the differenttestconditions are proposed for 16MnDR steel.

An improved algorithm for spectral emissivity measurements at low temperatures based on the multi-temperature calibration method

An experimental apparatus for normal spectral emissivity measurements at low temperatures was constructed by using the Fourier transform infrared (FTIR) spectrometer. The FTIR spectrometer was calibrated against a high quality reference blackbody based on the multi-temperature method. The spectral response function R (λ) was computed by the least-square method. To improve the precision of emissivity measurement, an improved algorithm to eliminate disturbances by background radiation was presented. Emissivity uncertainty caused by the spectral response function R (λ) was analyzed. A comparison between the results obtained by the multi-temperature calibration method and the two-temperature method was presented. The linearity of the FTIR spectrometer response in the studied spectral range is better than 1% except spectral bands due to atmospheric absorptions. A high-purity (99wt%) alumina sample was used to validate emissivity results obtained by the improved algorithm. The excellent agreement with the literature data around Christiansen wavelength demonstrates that our experimental apparatus and the improved algorithm can provide reliable measurements. The calculated relative combined uncertainty of the spectral emissivity for the alumina sample is estimated to be less than 5.1% for the spectral range considered.

Study of Constraint Effect on Reference Temperature (T0) of Reactor Pressure Vessel Material (20MnMoNi55 Steel) in the Ductile to Brittle Transition Region

The master curve methodology proposed by Kim Wallin (ASTM E1921-02) has been used to evaluate master curve and reference temperature (T0) from TPB specimen for the material 20MnMoNi55 steel using single temperature and multi-temperature method. The effect of test temperature on reference temperature (T0) has been studied for both TPB and CT specimens. A study is performed on the censor parameter M for both TPB and CT specimen and a correction value is suggested for TPB specimen for the material 20MnMoNi55 steel. To study the effect of constraint (a/w and thickness) on reference temperature (T0), the value of (T0) is calculated for different a/w ratio and thickness of TPB specimen. The results are compared with the results obtained from CT specimen for the same material to study the effect of geometry on reference temperature (T0).

Fracture Behaviour of 20MnMoNi55 Steel in DBT Region under Corrosive Environment

Different mechanical properties like strength, fracture toughness and fatigue life of structural components reduce due to corrosion of the material. In this paper the effect of corrosion on fracture toughness in ductile to brittle transition (DBT) region of 20MnMoNi55 steel is investigated. The corrosion properties of the material are measured by electrochemical impedance spectroscopy (EIS) test. The loss of ductility and fracture toughness due corrosion is measured by measuring master curve reference temperature in DBT region. Both single and multi–temperature method is used to measure the master curve reference temperature for both base material and corroded specimen. A comparative study is made to measure embrittlement that occurs due to corrosion in DBT region. From the EIS study it has been observed that the corrosion resistance properties decrease with time when the material corroded. Also the embrittlement occurring due to corrosion is reflected in the shift in master curve.

Application and comparative study of the master curve methodology for fracture toughness characterization of 20MnMoNi55 steel

The master curve methodology proposed by Kim Wallin (ASTM E1921-02) has been used to evaluate master curve reference temperature (T0) from full compact tension (CT) and 1/2T-CT specimens for the material 20MnMoNi55 steel using single temperature and multi-temperature method. The effect of temperature range, number of test temperatures and initial crack length on the value of T0 are also studied. The correction proposed for thickness adjustment has been verified. Master curves are drawn using full and 1/2T-CT specimen separately and compared with best fit characteristic curve and found to be within 95% bound.

Estimation of fracture toughness of 20MnMoNi55 steel in the ductile to brittle transition region using master curve method

Fracture toughness is an important material property to assess the critical load for structural integrity of reactor pressure vessel steel. In this paper, master curve method proposed by Kim Wallin is used to estimate the fracture toughness of 20MnMoNi55 steel in the ductile to brittle transition regime. Reference temperature ( T 0 ) is evaluated using both single temperature and multi-temperature method for one inch thick compact tension (1T-CT) specimens. Reference temperature ( T 0 ) is also determined from Charpy V-notch test data and compared. Effect of selection of temperature range and number of test temperatures on the value of T 0 is also studied. It is observed that Charpy test results yield lower values of unirradiated T 0 compared to 1T-CT specimen tests. It is also observed that most of the fracture toughness values fall between 5% and 95% boundary of fracture toughness curves for all the evaluations.

COMPARATIVE STUDY BETWEEN KINETIC AND THERMODYNAMIC CALCULATION OF COMPOSITION IN SF6 PLASMAS

In this paper we compare the compositions calculated in chemical equilibrium for an SF6 plasma at atmospheric pressure, in the multi-temperature model and using kinetics (33 reactions involving 18 species). The ratio of the electron temperature Te to that of heavy species Th was calculated as a function of electron density and an intermediate temperature T* between Te and Th was introduced to cope with the relationship kf (T*)/kr(T*) = KX(T*) where kf and kr are the reaction rate coefficients (forward and reverse) and KX the equilibrium constant. The main difference between equilibrium and kinetic calculations lies in the densities of S+, S2+, SF+, F− and S− species between 2,000 and 6,000 K. The multi-temperature method gives results very different from those of the kinetic calculations even when the charge loss reactions are neglected. This is in contrast to what happens with H2 or N2.

Measurement of surface temperature and emissivity by a multitemperature method for Fourier-transform infrared spectrometers

Surface temperatures are estimated with high precision based on a multitemperature method for Fourier-transform spectrometers. The method is based on Planck's radiation law and a nonlinear least-squares fitting algorithm applied to two or more spectra at different sample temperatures and a single measurement at a known sample temperature, for example, at ambient temperature. The temperature of the sample surface can be measured rather easily at ambient temperature. The spectrum at ambient temperature is used to eliminate background effects from spectra as measured at other surface temperatures. The temperatures of the sample are found in a single calculation from the measured spectra independently of the response function of the instrument and the emissivity of the sample. The spectral emissivity of a sample can be measured if the instrument is calibrated against a blackbody source. Temperatures of blackbody sources are estimated with an uncertainty of 0.2-2 K. The method is demonstrated for measuring the spectral emissivity of a brass specimen and an oxidized nickel specimen.