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Heating Methods (heating + methods)
Selected AbstractsResponse of soil surface CO2 flux in a boreal forest to ecosystem warmingGLOBAL CHANGE BIOLOGY, Issue 4 2008DUSTIN R. BRONSON Abstract Soil surface carbon dioxide (CO2) flux (RS) was measured for 2 years at the Boreal Soil and Air Warming Experiment site near Thompson, MB, Canada. The experimental design was a complete random block design that consisted of four replicate blocks, with each block containing a 15 m × 15 m control and heated plot. Black spruce [Picea mariana (Mill.) BSP] was the overstory species and Epilobium angustifolium was the dominant understory. Soil temperature was maintained (,5 °C) above the control soil temperature using electric cables inside water filled polyethylene tubing for each heated plot. Air inside a 7.3-m-diameter chamber, centered in the soil warming plot, contained approximately nine black spruce trees was heated ,5 °C above control ambient air temperature allowing for the testing of soil-only warming and soil+air warming. Soil surface CO2 flux (RS) was positively correlated (P < 0.0001) to soil temperature at 10 cm depth. Soil surface CO2 flux (RS) was 24% greater in the soil-only warming than the control in 2004, but was only 11% greater in 2005, while RS in the soil+air warming treatments was 31% less than the control in 2004 and 23% less in 2005. Live fine root mass (< 2 mm diameter) was less in the heated than control treatments in 2004 and statistically less (P < 0.01) in 2005. Similar root mass between the two heated treatments suggests that different heating methods (soil-only vs. soil+air warming) can affect the rate of decomposition. [source] EFFECTS OF THERMAL AND ELECTROTHERMAL PRETREATMENTS ON HOT AIR DRYING RATE OF VEGETABLE TISSUEJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2000WEI-CHI WANG ABSTRACT Cylindrical samples of carrot, potato and yam were dried in a hot-air dehydrator after preheating to 50C or 80C by three different heating methods (conventional, microwave and ohmic). The results showed that enhancement of drying rate increased with pretreatment temperature. Ohmic pretreatment increased the drying rate more than conventional and microwave heating. Desorption isotherms showed that in the low aw range, desorption data of preheated and raw materials were similar. However, the isotherms of preheated samples shifted when aw was high, which indicated that thermal pretreatments altered the structure, and apparently, the water distribution within these materials. For all samples, ohmic pretreatment showed stronger influences on isotherms than microwave heating, while the pretreatment effect of conventional heating was only observed for potato tissue. [source] Thermal Kinetic Parameters of Thiamin in Wheat Flour at Temperatures Higher than 100°CJOURNAL OF FOOD SCIENCE, Issue 3 2005Maria Suparno ABSTRACT: Kinetic parameters for thiamin degradation were obtained using 2 high-temperature heating methods: (1) atmospheric pressure (AP) with moisture correction and (2) controlled pressure (CP). At AP conditions, 33.3% dry basis (db) moisture wheat flour with 0.35% (db) thiamin was heated in thin steel cells isothermally at 145,160, and 172°C. To obtain the moisture correction factor, a constant-moisture study was conducted at 80°C using 6 moisture contents (6.1% to 36.9%). At CP conditions, flour at 19%, 28.2%, and 33.3% (db) moisture in double-seamed cans was heated in a CP steam retort at 129°C. For the AP method, the corrected activation energy for 33.3% moisture content was 129.5 kJ/g-mol and reaction rate at 80°C was 3.48×10,4 min,1. Using the CP method, the activation energy and reaction rate were 121.0 kJ/g-mol and 9.69×10,5 min,1, respectively. Results obtained from 2 methods were not statistically different. These results illustrated that the correction method could be used as an alternative for researchers without access to controlled pressure equipment and transient heat transfer software. [source] Microwave regeneration of zeolites in a 1 meter columnAICHE JOURNAL, Issue 7 2009Matthias Meier Abstract Although sorption is a common method of removing volatile organic compounds (VOC's) from processes, the adsorbent must be regenerated to repeat the process. The use of microwaves to regenerate the bed of adsorbent can be more efficient than conventional heating methods. Desorption of methanol from a silicalite zeolite was studied by the use of microwaves in cylindrical column. Temperature probes at five axial and three radial positions monitored the temperature profile in time. A significant amount of microwave energy passed through the dry zeolite bed, whereas a strong attenuation occurs if methanol is adsorbed. The radial temperature distribution conforms to theoretical predictions; however, microwave reflections cause a distortion of the predictions in the axial direction. Irregularities during the saturation of the bed indicated a chemical reaction during the irradiation with microwaves. A fraction of the methanol reacted under microwave irradiation to form dimethylether and water, and to methoxylate the zeolite surface. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Synthesis of Mixed Conducting Ceramic Oxides SrFeCo0.5Oy Powder by Hybrid Microwave HeatingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2002Di Huo Mixed conducting ceramic oxide SrFeCo0.5Oy powders were prepared by a conventional solid-state reaction method and two types of hybrid microwave heating methods. XRD, SEM/EDS (energy-dispersive spectroscopy), and TEM/EDX (energy-dispersive X-ray microanalysis) were used to characterize the products. The conventional heated sample is a three-phase mixture composed of a predominant orthorhombic Sr4(Fe1,xCox)6O13±, phase, a cubic perovskite SrFe1,xCoxO3,, phase, and a CoO phase. Phase components of the direct hybrid heated samples are similar to those of the conventional heated sample, except that its predominant phase is a cubic perovskite SrFe1,xCoxO3,, phase other than the orthorhombic Sr4(Fe1,xCox)6O13±, phase. The indirect hybrid heated sample is mainly composed of a cubic perovskite Sr(Fe,Co)1.5Oy phase, with a trace amount of orthorhombic phase and spinel (Fe,Co) oxides. The cobalt content of the Sr(Fe,Co)1.5Oy phase is much higher than that of the SrFe1,xCoxO3,, phase. Particle size distribution of the conventional heated sample is very wide. The indirect hybrid heated sample has a relatively narrow particle size distribution, with an average particle size of 3,4 ,m, but the particles stick to form agglomerates. The morphology of the direct hybrid heated sample is similar to that of the conventional heated sample, except that submicrometer grade particles were rarely observed. [source] Catalytic and Heating Behavior of Nanoscaled Perovskites under Microwave RadiationCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2008T. Krech Abstract Perovskite powders of the types La0.5Ca0.5AlyM1,yO3,, (y = 0,0.8), M = Fe, Cr, Mn, Co and LaxSr1,xMnyCo1,y (x = 0.5,1, y = 0,1) were prepared via a sol-gel route according to the modified Pechini method. Incineration of the resins was performed before final sintering at 1000,°C for 6,h. The phase composition of the samples was established by X-ray powder diffraction analysis, and the lattice parameters were calculated using Rietveld analysis. The shape and size of the particles were determined via scanning electron microscopy and the specific surface area of the powder perovskites was established by the BET method. The principal particles were ca. 100,nm in size and formed agglomerates larger than 1.0,,m. The composition of the perovskites was established by EDX analysis. Following this, the catalytic behavior was tested by means of total oxidation of propane. The catalytic performance was measured at atmospheric pressure with 3,g of catalyst in a fixed-bed quartz reactor (i.d. = 18,mm) under thermal-assisted and microwave-assisted conditions. Initial results show a strong dependence of the catalytic and heating behavior on the nature of the M-atom and its number of unpaired d-electrons as well as on the particle size and its specific surface area. No significant difference in the results could be detected from comparison of the two heating methods. [source] | ||||||||||