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Drying Experiments (drying + experiment)
Selected AbstractsExergetic performance assessment of a pilot-scale heat pump belt conveyor dryerINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2010Zafer Erbay Abstract In this study, olive leaves were dried in a pilot-scale heat pump (HP) belt conveyor dryer as a thin layer. Drying experiments were carried out at the drying air temperature range of 45,55°C with the drying air velocity range of 0.5,1.5,m,s,1. The performance of the system and the process was evaluated using exergy analysis method. The exergy loss and flow diagram (the so-called Grassmann diagram) of the dryer system was presented to give quantitative information regarding the proportion of the exergy input that is dissipated in the various system components. Effects of the drying air temperature and the velocity on the performance of the drying process were discussed. The actual coefficient of performance values were obtained to be 2.37 for the HP unit and 2.31 for the overall system, respectively. The most important component of the system for improving the efficiency was determined to be the compressor. Exergetic efficiencies of the drying of olive leaves were in the range of 67.45,81.95%. It was obtained that they increased as the drying air temperature decreased and the drying air velocity increased. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of Drying Characteristics and Effective Diffusivity for Sugar CubesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2004C. Akosman Abstract In this study, the drying characteristics of sugar cubes have been investigated. Drying experiments with sugar cubes were conducted in a laboratory-type tray dryer at temperatures ranging from 45 to 95,°C and different air velocities (0.43, 0.56, and 0.7,m/s). Drying rates increased with the increase in temperature and air velocity. At high temperatures, the moisture content of the solid reached equilibrium moisture value in short time periods. Experimental data were analyzed by using the analytical solution of the unsteady-state diffusion equation to determine the effective diffusivity in sugar cubes. [source] Ein Trocknungskoeffizient für BaustoffeBAUPHYSIK, Issue 3 2009Gregor A. Scheffler Dr.-Ing. Berechnungsverfahren; Feuchte Wärme; Versuche Abstract Ein wesentliches Element der hygrothermischen Charakterisierung von Baustoffen ist der Trocknungsversuch. Im Gegensatz zu anderen Feuchtetransportexperimenten wie dem Diffusionsversuch oder dem Wasseraufnahmeexperiment ist es bislang nicht möglich, aus der Trocknung einen einfachen Kennwert abzuleiten. In vielen Fällen, beispielsweise in der Interaktion von Forschung und Industrie, aber auch beim praktischen Vergleich bzw. der Auswahl geeigneter Baustoffe wäre ein solcher Kennwert jedoch wünschenswert. Im vorliegenden Artikel wird zunächst die Bedeutung des Trocknungsversuches für die hygrische Charakterisierung von Baustoffen herausgestellt, aus der sich das Bestreben ableitet, das Trocknungsverhalten zu standardisieren und einen Einzahlen-Materialkennwert zu definieren. Nach einer die verschiedenen Einflussfaktoren der Trocknung differenzierenden Einleitung werden bestehende Ansätze für die Standardisierung des Trocknungsverlaufes bzw. die Ableitung eines Trocknungskoeffizienten vorgestellt. Die einhergehenden Probleme werden diskutiert und weitere Möglichkeiten evaluiert. Ein einfacher Trocknungskoeffizient, der sich aus dem Trocknungsverlauf ableiten lässt, wird definiert. Die Korrelation dieses Koeffizienten mit dem Wasseraufnahmekoeffizienten und dem Dampfdiffusionswiderstand wird analysiert. Sein zusätzlicher Informationsgehalt wird in diesem Zusammenhang kritisch hinterfragt. Im Ergebnis steht die Definition des Trocknungskoeffizienten als ein neuer, unabhängiger Materialkennwert, der die Feuchtetransporteigenschaften im Übergang zwischen hygroskopischem und gesättigtem Transport beschreibt. Mit diesem Kennwert ist es möglich, Baustoffe einfach und schnell hinsichtlich ihres Trocknungsverhaltens zu unterscheiden und zu beurteilen, was insbesondere bei feuchtesensitiven Materialien von Bedeutung ist. A drying coefficient for building materials. The drying experiment is an important element of the hygrothermal characterisation of building materials. Contrary to other moisture transport experiments as the vapour diffusion and the water absorption test, it is until now not possible to derive a simple coefficient for the drying. However, in many cases such a coefficient would be highly appreciated, e.g. in interaction of industry and research or for the distinction and selection of suitable building materials throughout design and practise. This article first highlights the importance of drying experiments for hygrothermal characterisation of building materials on which the attempt is based to standardize the drying experiment as well as to derive a single number material coefficient. The drying itself is briefly reviewed and existing approaches are discussed. On this basis, possible definitions are evaluated. Finally, a drying coefficient is defined which can be determined based on measured drying data. The correlation of this coefficient with the water absorption and the vapour diffusion coefficient is analyzed and its additional information content is critically challenged. As result, a drying coefficient has been derived and defined as a new and independent material parameter. It contains information about the moisture transport properties throughout the wide range of moisture contents from hygroscopic up to saturation. With this new and valuable coefficient, it is now possible to distinguish and select building materials quickly and easily by means of their drying behaviour. This is particularly important for moisture sensitive materials. [source] Single-layer drying characteristics and colour kinetics of red chilliINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 11 2007Mohammed Ayub Hossain Summary Single-layer drying experiments were conducted under controlled conditions of temperature, relative humidity (RH) and air velocity to find out the effects of drying conditions and blanching on the drying rate and colour of Thai red chilli. Drying rate increased with an increase of drying air temperature and a decrease of RH. Air temperatures above 65 °C affected the colour of red chilli. Red chilli should be dried at an air velocity equal to or just above 0.50 m s,1. Above this value, the drying rate becomes independent of air velocity. RH and air velocity have no effect on the colour of red chilli. Faster drying rate and higher colour value was found for the blanched sample rather than the unblanched sample. The Newton and the Page equations were fitted to the experimental data. The Newton equation was found to describe the single-layer drying of red chilli better than the Page equation. [source] SUPERHEATED STEAM-DRYING OF MATE LEAVES AND EFFECT OF DRYING CONDITIONS ON THE PHENOL CONTENTJOURNAL OF FOOD PROCESS ENGINEERING, Issue 3 2006EVERTON FERNANDO ZANOELO ABSTRACT Four drying experiments of mate leaves (Ilex paraguariensis St. Hilaire) were carried out in a packed bed superheated steam dryer by varying outlet steam temperature from 120 to 140C and equivalent particle diameter from 4.7 × 10,3 to 6.95 × 10,3 m. The influence of these variables on the drying coefficient calculated by assuming a simplified drying kinetic model was investigated. A classical statistical approach revealed the significant effect of both factors on this parameter. Two additional drying runs were performed at identical conditions with conventional hot air and low pressure superheated steam, respectively. The influence of drying atmosphere on the total content of phenols was evaluated. A conventional process of extraction by using an aqueous methanol solution was adopted. Analyses for total phenols were performed by spectrophotometry at 715 nm by applying Folin-Denis assay. The leaves dried with superheated steam had approximately 47% higher retention of these compounds. [source] CHARACTERISTIC DRYING CURVE and MATHEMATICAL MODELING of THIN-LAYER SOLAR DRYING of PRICKLY PEAR CLADODE (OPUNTIA FICUS INDICA)JOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2004S. LAHSASNI ABSTRACT Thin-layer solar drying experiments were conducted for the prickly pear cladode grown in Marrakech, Morocco. the experimental drying curves obtained show only a falling rate period. the results verified, with good reproducibility, that the drying air temperature is the main factor in controlling the drying rate. the expression of the drying rate equation was determined empirically from the characteristic drying curve. Eight different drying models were compared according to their correlation coefficient (r2) to estimate solar drying curves. the Page model could satisfactorily describe the solar drying curves of cladode with an r2 of 0.9995. the coefficient of this model could be explained by the effect of drying air temperature with an r2 of 1.0000. [source] Comparative Study of Quality Changes Occurring on Dehydration and Rehydration of Cooked Chickpeas (Cicer Arietinum L.) Subjected to Combined Microwave,Convective and Convective Hot Air DehydrationJOURNAL OF FOOD SCIENCE, Issue 6 2006A.A. Gowen ABSTRACT:, Convective hot air dehydration (100 °C) of cooked chickpeas was compared with the combination of microwave,convective hot air dehydration, in terms of microstructure, density, color, texture, dehydration, and rehydration. In the combined drying experiments, 2 levels of microwave power (100 W and 200 W) were investigated, combined continuously with convective air drying at 100 °C. Compared with convective hot air drying, combination drying led to a considerable reduction in dehydration time. Combination drying also improved the porosity of the finished dehydrated product, leading to faster rehydration kinetics. Cryogenic scanning electron microscopy micrographs showed that chickpeas subjected to combined drying experienced less shrinkage than those dried by convective hot air. Combination drying at the higher (200 W) level produced a darker (P < 0.05) rehydrated product with significantly lower relative rehydrated moisture content (P < 0.05) when compared with the lower (100 W) level of combination drying. [source] | |||||||||||||