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Heating Conditions (heating + condition)
Selected AbstractsMethod of calculation of heat transfer coefficient of the heater in a circulating fluidized bed furnaceHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2002J.F. Lu Abstract Knowledge of heat transfer coefficients is important in the design and operation of CFB boilers. It is the key to determining the area and the layout of the heat transfer surfaces in a CFB furnace. Local bulk density has a close relationship to the local heat transfer coefficient. Using a heat flux probe and bulk density sampling probe, the local bed to wall heat transfer coefficient in the furnace of a 75 t/h CFB boiler was measured. According to the experimental results and theoretical analysis of the facts that influence the heat transfer, the heat transfer coefficient calculation method for the CFB furnace was developed. The heat transfer surface configuration, heating condition, and the material density are considered in this method. The calculation method has been used in the design of CFB boilers with a capacity from 130 t/h to 420 t/h. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(7): 540,550, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10056 [source] Moisture Migration in Solid Food MatricesJOURNAL OF FOOD SCIENCE, Issue 8 2003Y.-C. Fu ABSTRACT: The goals of this study were to measure moisture migration in a porous solid matrix simulating a real food (flour dough) and to accomplish heating of the solid matrix. An off-line technique and a microwave temperature controller system were developed for measuring moisture concentration under isothermal heating condition. A temperature profile of a cylindrical dough sample was achieved by accurate control of microwave energy input and preheated carrier gas temperature. Results showed a simplified 1st order kinetic model adequately predicted moisture loss in dough samples. Effect of temperature on the rate constant was adequately modeled by the Arrhenius relationship. The rate constant was found to be affected by porosity of the dough sample. [source] Stabilization of phytosterols in rapeseed oil by natural antioxidants during heatingEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 11 2009Dominik Kmiecik Abstract Antioxidants are substances that can reduce negative changes in fat. Many antioxidants are very effective during storage, but during heating they lose their properties. It is very important to find antioxidants that will be stable at high temperatures and protect fat throughout the entire frying process. The aim of this study was to estimate the effect of natural and synthetic antioxidants on changes in phytosterols of rapeseed oil during heating. Oil with antioxidants was heated at 180,°C for 4,h in a Rancimat® and in an Oxidograph®. Ethanol extract of rosemary, ethanol extract of green tea, and BHT were used in the study. The contents of phytosterols (sitosterol, campesterol, avenasterol, brassicasterol, stigmasterol) and oxyphytosterols (7,- and 7,-hydroxysterol, 5,,6,- and 5,,6,-epoxysterol, 7-ketosterol and triols) were estimated by gas chromatography. In all samples with antioxidants, a lower decrease of phytosterols and a lower increase of total oxyphytosterols were observed in comparison with the control sample (without antioxidant). The antioxidant effect depends on the type of the antioxidant and the heating conditions. The best results were observed in samples with natural antioxidants. BHT was a substance that protected phytosterols as well, but not as effectively as the other antioxidants. [source] Straightforward Synthesis of ,-Substituted Prolines by Cross-MetathesisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2008Marco Lumini Abstract The synthesis of several ,-substituted N -Boc-protected prolines has been achieved by cross metathesis (CM) of N -Boc-allylproline 5 with terminal long chain alkenes and alkenes bearing hydroxy, silyloxy, ester, and O -acetylglucosamido groups. The CM occurred with good selectivity and short reaction time under microwave heating conditions, affording yields in the range of 40,92,%. Addition of Ti(OiPr)4 as a Lewis acid allowed a slight increase of the yield in the case of alkenes with Lewis basic substituents. The CM was also successfully applied to allylproline protected with trichloroacetaldehyde 4, but the intermediate products were less practical for further deprotection and elaboration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Palladium(II) Chloride and a (Dipyridin-2-ylmethyl)amine-Derived Palladium(II) Chloride Complex as Highly Efficient Catalysts for the Synthesis of Alkynes in Water or in NMP and of Diynes in the Absence of ReoxidantEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2005Juan Gil-Moltó Abstract The (dipyridin-2-ylmethyl)amine-derived palladium chloride complex 1 and PdCl2 are efficient catalysts for cross-coupling reactions between terminal alkynes and aryl iodides or bromides under modified Sonogashira,Cassar,Heck conditions. The alkynylation can be performed under copper-free conditions in water at reflux or at room temperature under air with pyrrolidine as base and tetra- n -butylammonium bromide (TBAB) as additive, with TONs of up to 7,×,104 and TOFs(h,1) of up to 6666. Terminal alkynes can be arylated in NMP as well under copper- and amine-free conditions at 110 °C or room temperature, with tetra- n -butylammonium acetate (TBAA) acting as base with TONs up to 2,×,105 and TOFs (h,1) up to 66,666. In general, complex 1 displays a slightly higher efficiency than PdCl2 as catalyst and maintains the same activity after five consecutive runs. Alternatively, these alkynylation processes can be carried out under microwave heating conditions. The homocoupling of terminal alkynes to the corresponding 1,3-diynes proceeds under phosphane-free conditions with the (dipyridin-2-ylmethyl)amine-derived palladium chloride complex 1 or with PdCl2 as catalysts and with CuI as cocatalyst in NMP with use of either TBAA or pyrrolidine as bases. This Glaser-type reaction can be performed at 110 °C or at room temp. in the presence of air without the use of a reoxidant. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] The Effect of Electric Field on Important Food-processing Enzymes: Comparison of Inactivation Kinetics under Conventional and Ohmic HeatingJOURNAL OF FOOD SCIENCE, Issue 9 2004I. Castro ABSTRACT: This work deals with the determination of the inactivation kinetics of several enzymes, most of them used as time-temperature integrators in the food industry. The tested enzymes were polyphenoloxidase, lipoxygenase, pectinase, alkaline phosphatase, and p-galactosidase, and the inactivation assays were performed under conventional and ohmic heating conditions. The thermal history of the samples (conventional and ohmically processed) was made equal to determine if there was an additional inactivation caused by the presence of an electric field, thus eliminating temperature as a variable. All the enzymes followed 1st-order inactivation kinetics for both conventional and ohmic heating treatments. The presence of an electric field does not cause an enhanced inactivation to alkaline phosphatase, pectinase, and ,- galactosidase. However, lipoxygenase and polyphenoloxidase kinetics were significantly affected by the electric field, reducing the time needed for inactivation. The results of the present work can be used industrially to determine processing effectiveness when ohmic heating technology is applied. [source] Rapid and efficient microwave assisted method for the regioselective synthesis of 8,8,-methylene-bis-4-oxo-1H and 2H -chromeno[4,3- C]pyrazolesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2007Adki Nagaraj The ethyl ester of 5,5,-methylene-bis-salicyclic acid 3 was prepared by the esterification of 5,5,-methylene-bis-salicylic acid 2. The compound 3 on reacting with ethylacetoacetate yields 6,6,-methylenebis-(3-acetyl-4-hydroxycoumarin) 4. The compound 4 was regioselectively converted into either 8,8,-methylene-bis-(4-oxo-1H -chromeno[4,3- c]pyrazoles) 6 or 8,8,-methylene-bis(-4-oxo-2H -chromeno[4,3- c]-pyrazoles) 7 under microwave irradiation. High yields are achieved even on a gram scale, while reaction times are considerably shortened compared to conventional heating conditions. [source] Drying Stages during the Heating of High-Alumina, Ultra-Low-Cement Refractory CastablesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2003Murilo D. M. Innocentini The purpose of this work was to investigate the drying kinetics of high-alumina, ultra-low-cement refractory castables under continuous heating conditions. Three main drying stages were identified during the castable heat-up and were related to the phase change of free water and to the decomposition of hydrated products present in the body. A clear correlation was found between the actual heating profile inside the castable and the dewatering stages under various heating schedules. Thermal analysis was used to assess the drying temperature that represents the highest risk of steam pressure buildup and, thus, of explosive spalling. [source] Influence of heating conditions and starch on the storage modulus of Russet Burbank and Yukon Gold potatoesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2001Renan Bu-Contreras Abstract The storage modulus of Russet Burbank (RB) and Yukon Gold (YG) potato discs (13.3,mm,× 4.5,mm) was measured continuously during heating in water at temperatures ranging from 40 to 80,°C for 120,min using a dynamic mechanical analyser with a heating stage. The starch content of YG potatoes was higher than that of RB potatoes, but the raw starch granule size distribution of both varieties was similar. RB samples had the highest storage modulus values (25% higher than raw tissue) when heated in 60,°C water for 35,min. Image analysis revealed that the perimeters of starch granules in the potato samples increased by about 50% during heating for 30,min at 60,°C. Heating temperature and time and starch content influenced the storage modulus. © 2001 Society of Chemical Industry [source] The influence of chain-ends on the thermal and rheological properties of some 40/60 PES/PEES copolymersPOLYMER ENGINEERING & SCIENCE, Issue 8 2009Lorenzo Abate Four random, differently ended (Cl, NH2, OH, and COO,), polyethersulfone/polyetherethersulfone (PES/PEES) copolymers were studied to investigate the influence of chain ends on thermal and rheological behaviors. The number average molar mass (Mn , 9500 g·mol,1) and the PES/PEES ratio (40/60) of all copolymers investigated were checked by 1H NMR spectra. Thermal degradations were carried out in the scanning mode and initial decomposition temperatures (Ti) and activation energy values of degradation (Ea) were obtained. Glass transition temperature (Tg) was determined by differential scanning calorimetry and complex viscosity (,*) by rheological measurements in isothermal heating conditions (T = 270°C). All parameters determined were largely affected by copolymer chain ends and decreased according to the same order, OH > NH2 > Cl > COO,. The results were discussed and interpreted. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] The Effect of Cook-Off on the Bulk Permeability of a Plastic Bonded ExplosivePROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 5 2006Guillermo Terrones Abstract Plastic bonded explosives when exposed to prolonged heating environments undergo a variety of changes that affect their bulk chemical, thermophysical, and mechanical properties. During slow heating conditions, referred to as cook-off, the thermal behavior of the polymeric binder plays an important role in the transformations of these composite energetic materials. The recently introduced Darcian flow hypothesis for PBX-9501 implies that, during preignition, temperature gradients will lead to pressure gradients which in turn will drive convection of decomposition gases throughout the explosive, thus affecting ignition time and location. Here, we focus on the cook-off behavior of PBX-9501 and investigate its effects on bulk permeability to gases produced as a result of thermal decomposition. The concept of Darcian convection through porous media is defined and illustrated in detail by the derivation of the governing equations for a permeameter. Based on a systematic analysis involving: 1) our current understanding about binder behavior as a function of temperature, 2) the physics of the gas permeameter apparatus, 3) the concept of liquid drainage by gas, and 4) the experimental record of four permeameter experiments with cooked PBX-9501, we conclude that samples heated up to 186,°C were not permeable in the Darcy-flow sense. [source] | ||||||||||||||||||||||