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An empirical study on vortex-generator insert f.tted in tubular heat exchangers with dilute Cu–water nanof.uid f.ow

Chinese Journal of.Chemical Engineering 2016年第6期24卷 728-736页

作者： M. Khoshvaght-Aliabadi M.H. Akbari f. hormozi Department of.Chemical Engineering Shahrood Branch Islamic Azad University Shahrood lran School of.Chemical Petroleum and Gas Engineering Semnan University Semnan lran

The heat transf.r enhancement(HTE) in tubular heat exchangers f.tted with vortex-generator(VG) inserts is experimentally investigated. The studied f.ur parameters and ranges are: winglets-pitch ratio(1.33, 2.67, and 4),winglets-length ratio(0.33, 0.67, and 1), winglets-width ratio(0.2, 0.4, and 0.6), and Reynolds number(5200to 12200). The testing f.uids are the water and Cu–water nanof.uid at the volumetric f.action of.0.2%. The results obtained on HTE, pressure drop, and perf.rmance evaluation criterion(PEC) are compared with those f.r water in a smooth tube. It is f.und that the VG inserts with lower winglets-pitch ratio and higher winglets-length/width ratios present higher values of.HTE and pressure drop. Over the range studied, the maximum PEC of.1.83 is detected with the Cu–water nanof.uid inside the tube equipped with a VG insert at the winglets-width ratio of..6 f.r the maximum Reynolds number, when the heat transf.r rate and pressure drop are 1.24 times and 2.03 times of.those in the smooth tube. Generalized regression equations of.the Nusselt number, f.iction f.ctor, and PEC are presented f.r the tubular heat exchangers with the VG inserts f.r both water and Cu–water *** is concluded that the main advantage of.the VG inserts is their simple f.brication and considerable perf.rmance, particularly at higher Reynolds number.

关键词： Heat transf.r enhancementVortex-generator insertNanof.uid Turbulent f.owCorrelation

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Proposed Models f.r Subcritical Water Extraction of.Essential Oils

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Chinese Journal of.Chemical Engineering 2009年第3期17卷 359-365页

作者： M.Khajenoori A.Haghighi Asl f.hormozi Chemical Engineering Department Faculty of EngineeringSemnan University

Mechanisms that control the extraction rate of.essential oil f.om Zataria multif.ora Boiss. (Z. multif.ora) with subcritical water (SW) were studied. The extraction curves at dif.erent solvent f.ow rates were used to deter-mine whether the extractions were limited primarily by the near equilibrium partitioning of.the analyte between the matrix and solvent (i.e. partitioning thermodynamics) or by the rates of.analyte desorption f.om the matrix (i.e. ki-netics). f.ur simple models have been applied to describe the extraction prof.les obtained with SW: (1) a model based solely on the thermodynamic distribution coef.icient KD, which assumes that analyte desorption f.om the ma-trix is rapid compared to elution; (2) one-site kinetic model, which assumes that the extraction rate is limited by the analyte desorption rate f.om the matrix, and is not limited by the thermodynamic (KD) partitioning that occurs dur-ing elution; (3) two-site kinetic model and (4) external mass transf.r resistance model. f.r SW extraction, the thermodynamic elution of.analytes f.om the matrix was the prevailing mechanism as evidenced by the f.ct that ex-traction rates increased proportionally with the SW f.ow rate. This was also conf.rmed by the f.ct that simple re-moval calculations based on determined KD (f.r major essential oil compounds) gave good f.ts to experimental data f.r f.ow rates f.om 1 to 4 ml·min-1. The results suggested that the overall extraction mechanism was inf.uenced by solute partitioning equilibrium with external mass transf.r through liquid f.lm.

关键词： essential oils Zataria multif.ora Boiss. subcrltlcal water extraction mechanisn

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