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C.h. Tong - One of the best experts on this subject based on the ideXlab platform.
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The Use of Fractional Conversion Technique to Investigate the Effects of Testing Parameters on Texture Degradation Kinetics
Journal of Food Science, 2000Co-Authors: T.r. Stoneham, D.b. Lund, C.h. TongAbstract:To study the effects of testing parameters on texture degradation, texture loss of potatoes heated at 80 degrees C was measured using an Instron universal testing machine as well as a texture analyzer under 2 instrument cross-head speeds, 2 sample sizes, and either compression or shear modes of mechanical deformation. Using the Fractional Conversion as a texture index, the kinetics of texture degradation of potatoes fitted a single 1st order reaction model, and the rate constant (or D value) was shown to be independent of the test used to determine the texture index. The average D value was 30+/-1.2 min at 80 degrees C.
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Fractional Conversion for determining texture degradation kinetics of vegetables
Journal of Food Science, 1997Co-Authors: A.f. Rizvi, C.h. TongAbstract:Fractional Conversion (f) takes into account the nonzero texture property upon prolonged heating. This was applied as an alternate technique for reanalyzing texture degradation kinetics based on published data which indicated that the softening of vegetables followed a dual mechanism first order kinetic model. The plot of the logarithm of 1-f vs heating time was linear through log cycles indicating the reaction was first order with a single rate constant and the substrate b was better characterized by the equilibrium (or maximum retainable) texture property. A possible explanation was developed for negative activation energies which had been reported for the second mechanism with some vegetables.
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Formation Kinetics of 2,5-Dimethylpyrazine and 2-Methylpyrazine in a Solid Model System Consisting of Amioca Starch, Lysine, and Glucose
Journal of Agricultural and Food Chemistry, 1997Co-Authors: M. G. Jusino, C.h. TongAbstract:A new analysis using the Fractional Conversion technique was applied to determine the formation kinetics of 2,5-dimethylpyrazine and 2-methylpyrazine in a solid model system containing 4.5% (w/w) lysine, 5.5% glucose, and amioca starch with 10% moisture (dry basis) from 80 to 120 °C. The reaction order and kinetic parameters (rate constants and activation energy) were determined through a parameter estimation technique based on least-squares fit. The formation rate of both pyrazines followed a first-order reaction model. No significant differences were observed for the activation energies and rate constants for 2,5-dimethylpyrazine and 2-methylpyrazine, suggesting the production of these pyrazines was controlled by the same rate-limiting step. The activation energy was 13.5 kcal/mol. Keywords: Kinetics; 2,5-dimethylpyrazine and 2-methylpyrazine; solid state; Fractional Conversion
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Degradation Kinetics of Green Color and Chlorophylls in Peas by Colorimetry and HPLC
Journal of Food Science, 1996Co-Authors: J.a. Steet, C.h. TongAbstract:The kinetics of chlorophyll degradation and visual green color loss in pureed green peas with 80% moisture (w/w) were determined at 70, 80 and 90 C. The –a value from a tristimulus colorimeter was chosen as the physical property and a technique based on Fractional Conversion was developed in the determination of kinetic parameters of visual green color loss. The degradation of chlorophyll a, chlorophyll b and greenness followed a first order reaction and the temperature dependence of these reactions indicated an Arrhenius relationship. The activation energies were 19.5, 17.1 and 18.2 kcal/mol, respectively.
Asghar Molaei Dehkordi - One of the best experts on this subject based on the ideXlab platform.
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Two-dimensional CFD simulation of chemical reactions in tapered-in and tapered-out fluidized bed reactors
Advanced Powder Technology, 2019Co-Authors: Hossein Askaripour, Asghar Molaei DehkordiAbstract:Abstract This article presents a simulation study of tapered-in and tapered-out fluidized bed reactors to investigate the influences of apex angle on the Fractional Conversion and the pressure drop of the fluidized beds in the presence of two types of chemical reaction with gas volume increase and reduction. The 2D behavior of tapered-in and -out fluidized beds was also compared with a columnar one from Fractional Conversion and bed pressure drop point of views. To validate the simulation results, the numerical predictions for the expansion ratio and the pressure drop of a tapered fluidized bed were compared with experimental data and good agreement was observed. The obtained simulation results clearly indicate that an apt apex angle exists in tapered-in reactors in which the Fractional Conversion reaches a maximum value; while the variations of the apex angle slightly affect the Fractional Conversion in tapered-out fluidized beds. Increasing the residence time of the gas phase in the upper section of tapered-in beds has positive influences on the Fractional Conversion, while a further decrease in the gas phase velocity in the tapered-in reactors has a negative effect on the Fractional Conversion. Moreover, higher bed pressure drop was observed in tapered-in reactors than that in the columnar and tapered-out ones.
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Effects of initial static bed height on Fractional Conversion and bed pressure drop in tapered-in and tapered-out fluidized bed reactors
International Journal of Multiphase Flow, 2016Co-Authors: Hossein Askaripour, Asghar Molaei DehkordiAbstract:Abstract In this article, a standard 2D Two-Fluid Model (TFM) closed by the kinetic theory of granular flow (KTGF) has been applied to simulate the behavior of tapered-in and tapered-out fluidized bed reactors. In this regard, two types of chemical reactions with gas volume reduction and increase were considered to investigate the effects of initial static bed height on the Fractional Conversion and bed pressure drop. To validate the CFD model predictions, the results of hydrodynamic simulations concerning bed pressure drop and bed expansion ratio were compared against experimental data reported in the literature and excellent agreement was observed. The obtained simulation results clearly indicate that there is an appropriate static bed height in a tapered-in reactor in which the Fractional Conversion becomes maximum at this height; whereas variations of static bed height in a tapered-out reactor have insignificant influences on the Fractional Conversion. Moreover, it was found that the residence time, temperature, and intensity of turbulence of the gas phase are three important factors affecting the Fractional Conversion in tapered fluidized bed reactors. In addition, it was observed that increasing the static bed height increases the bed pressure drop for both the tapered-in and tapered-out fluidized bed reactors.
Rongyi Zhao - One of the best experts on this subject based on the ideXlab platform.
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An improved model for analyzing the performance of photocatalytic oxidation reactors in removing volatile organic compounds and its application.
Journal of the Air & Waste Management Association (1995), 2004Co-Authors: Rui Yang, Yinping Zhang, Rongyi ZhaoAbstract:Abstract An improved photocatalytic oxidation (PCO) reactor model was developed to analyze the removal of volatile organic compounds (VOCs) in indoor air. One new parameter, the average total removing factor K t, together with the other two parameters, the number of mass transfer units NTUm and the Fractional Conversion e, are found to be the main parameters influencing the photooxidation performance of PCO reactors. Three new parameters, the ideal reaction number of mass transfer units, NTUm,ir; the ideal reaction Fractional Conversion, eir; and the reaction effectiveness, η, also are defined. These concepts are helpful to the structural design and optimization for PCO reactors. The application of the model in designing a plate-type PCO reactor is demonstrated. This study shows that the present model is an effective tool for designing PCO reactors and for evaluating VOC removal performance of available PCO reactors.
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A model for analyzing the performance of photocatalytic air cleaner in removing volatile organic compounds
Atmospheric Environment, 2003Co-Authors: Yinping Zhang, Rui Yang, Rongyi ZhaoAbstract:Abstract A photocatalytic oxidation (PCO) reactor model was developed to analyze the removal of volatile organic compounds (VOCs) in indoor air. Two parameters, the Fractional Conversion, e , and the number of mass transfer units (NTU m ), were found to be the main parameters influencing the photooxidation performance of PCO reactors. The factors of affecting the effect of removing VOCs of PCO reactor are discussed. The predicted photocatalytic reaction rate coefficient, Fractional Conversion, e , and NTU m for a typical PCO reactor agreed well with experimental data. The study shows that the effectiveness—NTU method used for heat exchangers is also an effective tool for designing PCO reactors and for evaluating their VOC removal effect.
Timur Dogu - One of the best experts on this subject based on the ideXlab platform.
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Simultaneous Production of tert-Amyl Ethyl Ether and tert-Amyl Alcohol from Isoamylene−Ethanol−Water Mixtures in a Batch−Reactive Distillation Column
Industrial & Engineering Chemistry Research, 2005Co-Authors: Dilek Varisli, Timur DoguAbstract:tert-Amyl ethyl ether (TAEE) and tert-amyl alcohol (TAA), which are the attractive alternatives to methyl tert-butyl ether as octane-enhancing gasoline-blending components, are produced by the simultaneous etherification and hydration of 2-methyl-2-butene (2M2B) in a batch−reactive distillation column. It was shown that, by changing the reboiler temperature in the range of 90−124 °C, significant increases of the overall Fractional Conversion of 2M2B, reaching values of 0.99, were achieved in this system. In the presence of water, the formation of TAA was also found to take place by the reactions of 2M2B and TAEE with water. Higher selectivities were observed for TAA than for TAEE, in the presence of water. This is due to the higher adsorption equilibrium constant of water than of ethanol on an Amberlyst-15 resin catalyst. A significant increase in the Fractional Conversion of 2M2B to TAEE was observed in the absence of water.
Richard A. Venditti - One of the best experts on this subject based on the ideXlab platform.
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A relationship between the glass transition temperature (Tg) and Fractional Conversion for thermosetting systems
Journal of Applied Polymer Science, 1997Co-Authors: Richard A. Venditti, John K. GillhamAbstract:An equation, based on thermodynamic considerations to relate the glass transition temperature, T g , to compositional variation of a polymer system, is adapted in this article for modeling the T g vs. Fractional Conversion (x) relationship of reactive thermosetting systems. Agreement between the adapted equation and experimental Tg vs. x data is found for several thermosetting crosslinking systems (i.e., epoxies and cyanate ester/polycyanurate) as well as for reactive thermosetting linear polymer systems (i.e., polyamic acid and esters to polyimides). The equation models the experimentally obtained T g vs. x behavior of thermosetting systems which include competing reactions. Agreement for widely varying molecular structures demonstrates the generality of the equation. The entire T g vs. x relationship can be predicted for a thermosetting material by using the T g vs. x equation and the values of the initial glass transition temperature, T g0 , the fully reacted system glass transition temperature, T gx , and the ratio of the change in specific heat from the liquid or rubbery state to the glassy state (Δc p ) at T g0 and T gx , Δc px /Δc P0 . The values of T go, T gx , and ΔC px /Δc p0 can be measured generally from two differential scanning calorimetric experiments.
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Glass transition temperature (Tg) versus Fractional Conversion for a linear thermosetting polyamic acid ester–polyimide system
Journal of Applied Polymer Science, 1994Co-Authors: Richard A. Venditti, John K. Gillham, E. Chin, F. M. HoulihanAbstract:The relationship of the glass transition temperature, Tg, to Fractional Conversion, x, for the Conversion of the cyclohexylmethyl ester of the benzophenone tetracarboxylic dianhydride–oxydianiline polyamic acid to polyimide has been investigated using dynamic mechanical analysis (torsion pendulum, TBA). The glass transition temperature and Conversion measurements were obtained on a single solvent-free polyamic acid ester specimen during cooling after heating to successively higher cure temperatures. Conversion was determined from the intensity of a sub-Tg mechanical relaxation peak that has been assigned to a relaxation of the cyclohexyl group. The resulting Tg versus x relationship is nonlinear. The Tg versus x relationship is adequately modeled using an expression derived by Couchman. © 1994 John Wiley & Sons, Inc.
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glass transition temperature tg versus Fractional Conversion for a linear thermosetting polyamic acid ester polyimide system
Journal of Applied Polymer Science, 1994Co-Authors: Richard A. Venditti, John K. Gillham, E. Chin, F. M. HoulihanAbstract:The relationship of the glass transition temperature, Tg, to Fractional Conversion, x, for the Conversion of the cyclohexylmethyl ester of the benzophenone tetracarboxylic dianhydride–oxydianiline polyamic acid to polyimide has been investigated using dynamic mechanical analysis (torsion pendulum, TBA). The glass transition temperature and Conversion measurements were obtained on a single solvent-free polyamic acid ester specimen during cooling after heating to successively higher cure temperatures. Conversion was determined from the intensity of a sub-Tg mechanical relaxation peak that has been assigned to a relaxation of the cyclohexyl group. The resulting Tg versus x relationship is nonlinear. The Tg versus x relationship is adequately modeled using an expression derived by Couchman. © 1994 John Wiley & Sons, Inc.
