Prijenos topline u mjehurastim stupcima

Bubble columns are gas-liquid contactors often used in industry. Although they are used primarily for mass transfer purpose, since gas and liquid phases are fed to the column at different temperatures, direct contact heat transfer becomes important as well. This research is about the heat transfer characteristics of bubble columns. Experiments were carried out using a plexiglass column with dimensions 160x160x1180 mm. Water was first put into the column to the height of 1 m and heated to the desired temperature, and then experiments were performed by introducing ambient air to the column and recording the variation in temperature of water and inlet and outlet air temperatures and humidities. Models developed for the convective heat transfer from the liquid interface to the gas in the bubble were used together with the experimental data to determine the heat and mass transfer coefficients. The volumetric heat transfer coefficient (hGa) was found to vary over the range 0,3-16 kW/(m3·K) with gas flow rate and the volumetric mass transfer coefficient (kGa) in the range 0,35-7,49 kmol/ m3·s·atm.Mjehurasti stupci su dodiri između plina i kapljevine koji se često koriste u industriji.. Iako ih se primarno koristi s ciljem prijenosa mase, budući da se plinska i kapljevita faza razdvajaju u stupce pri različitim temperaturama. tada njihov izravni dodir postaje važan za prijenos topline.. Ovo se istraživanje bavi karakteristikama prijenosa topline mjehurastih stupaca. Eksperimenti su napravljeni koriste cilindar od plexiglasa dimenzija 160x160x1180 mm. U cilindar je prvo ulivena voda do visine od 1 m i koja je zagrijavana do željene temperature, nakon čega se u tu vodu uvodio zrak okolišnje temperature, pri čemu se mjerila promjena temperature vode, kai i ulazna i izlazna vlažnost zraka. Modeli razvijeni za konvektivni prijenos topline sa slobodne površine kapljevine na mjehur su korišteni zajedno sa eksperimentalnim podacima za određivanje koeficijenata prijenosa topline i mase.. Iznađeno je da je volumetrički koeficijent prijenosa topline varirao u području 0.3-16 kW/(m3·K) s protokom zraka i volumetričkim koeficijentom prijenosa mase u području 0.35 – 7,39 kmol/(m3·s·atm

Hydrodynamic and particulate recovery studies in mobile-bed contacting

Note:Hydrodynamic and particulate recovery characteristics of mobile-bed contacting (MBC) were studied in a 0.29 m diameter column over the range of gas and liquid flow rates 0.5 < G < 5.5 and 4.7 < L 2 < 33 kg/m -s. Packing of density 157 kg/m3, of diameter 38, 25 and 19 mm, was used to obtain static bed heights of 0.29, 0.44 and 0.58 m. Correlations were developed for bed expansion, minimum fluidization velocity, pressure drop and liquid holdup. Inertial impaction was found to be the dominant aerodynamic mechanism for particle collection in MBC. A general theory for particle collection in any scrubber was developed. Analogous to mass transfer, a particle transfer coefficient, kp, was defined. A general correlation for kp was obtained for MBC, incorporating experimentally determined effects of liquid and gas flow rate, packing size, static bed height, particle size, and hydrophobicity of particles. The correlation was validated for particles in the size range 0.35 - 5.5 um. [...]On a étudié les caractéristiques hydrodynamiques et les caractéristiques de la récupération des particules pour le processus de "mobile-bed contacting (MBC)" à l'aide d'une colonne de diamètre 0.29 m pour des débits du gaz de 0.5 à 5.5 kg/m--set du liquide de 4.7 à 33 kg/m2-s. On a obtenu des hauteurs de lit statique de 0.29, 0.44 et 0.58 m à l'aide de garnissages de 157 kg/m3 de densité, et de 38, 25 et 19 mm de diamètre. Des corrélations ont pu être établies quant à la dilatation du lit, la vitesse minimum de fluidisation, la perte de charge et la quantité de liquide retenue au lit. On a montré que les collisions dues à l'inertie constituent le mécanisme aérodynamique principal de récupération des particules dans leMBC. [...

Effect of Different Parameters on Hydrogen Production by Electrochemical Reforming of Glycerol

With the increasing need for new and clean energy, it is highly important to lean towards technologies based on renewable resources for hydrogen production as they are less harmful to environment and sustainable systems. Within the scope of this study, the aim was to convert glycerol, a by-product of biodiesel production, to hydrogen using electrochemical reforming and thus paving the way to convert glycerol to value-added chemicals and alternative fuels. Producing hydrogen from glycerol contributes also to the overall economy of biodiesel technology. By utilizing the functionality of 3 -OH groups present in the molecular structure of glycerol, hydrogen can be produced from glycerol. By this way, hydrogen production was achieved with an innovative method at high purity, without the need for further purification operation. Within the context of the study, a parametric study was carried out. The experimental system was run under different operating conditions in order to determine the optimal conditions. Glycerol concentration, electrode material, distance between the electrodes, electrolyte, temperature, mixing effect and the effect of additives to electrolyte were investigated and their contributions to hydrogen production were investigated. When H2SO4 was used as the electrolyte, 0,4 M glycerol solution was determined as optimum solution. The highest current density value was achieved by using Zn/Zn electrode pair. The values were 8.5, 17.7 and 25.1 mA/cm2 for 0.5, 1 and 1.5 V, respectively

Yapılı dolgulu kolonda sıvı ve gaz fazı kütle transfer katsayıları ve ara yüzey alanı

Studies on CO2 removal and structured packed columns have been prominent in recent years. This study, as the first stage on this subject, involves characterization studies including hydrodynamics and mass transfer coefficients of a new genuine structured packed column designed and manufactured by our own facilities, which can be used for this purpose. Firstly, the maximum and minimum limits of the gas and liquid velocities that can be employed in the column were determined by specifying the loading and flooding points through pressure drop measurements. Accordingly, the superficial velocity ranges for liquid and gas were identified as 0.002-0.0047 {[}m/s] and 0.07-0.68 {[}m/s], respectively. The individual volumetric physical mass transfer coefficients of the liquid side (k(L)(0)a) and gas side (k(c)(0)a) were obtained experimentally in these ranges. Overall volumetric physical mass transfer coefficients (K(c)(0)a) were calculated for CO2-water system according to the two-resistance theory. The experiments were also performed with CO2-NaOH system, and overall volumetric chemical mass transfer coefficients (K(c)a), Hatta number (Ha) and enhancement factor (E) were determined. The experimental findings indicated that the fast pseudo-first order reaction regime was acceptable for this chemical absorption. Finally, the effective interfacial area (a(eff)) values were also determined at different gas and liquid velocities

Investigation of Various Parameters in Hydrogen Production by Electrolysis Method from Çan Lignite

Coal, which is one of the sources where hydrogen can be obtained by electrolysis with high purity, is an attractive option due to its low cost and large supply. In this study, various parameters (coal particle size, temperature, mixing speed, electrode material and addition of Fe+2 ion) affecting hydrogen production by electrolysis of Çanakkale/Çan lignite-water slurries were investigated. Experiments were carried out in two electrode (anode/cathode) electrolysis cell, in acidic medium using 1 M H2SO4 as electrolyte at atmospheric pressure. In the experiments copper-copper and zinc-zinc electrodes were used as electrodes. In order to determine the effect of temperature on the current density, measurements were carried out at regular intervals from room temperature to 80°C. It was determined that current density increased with temperature. In the experiments carried out with three different particle sizes (1.0-0.5 mm, 0.50-0.25 mm and <0.25 mm), the highest current density values were obtained with the smallest particle size. The effect of Fe+2 ion was achieved by adding 0.1 M FeSO4 to the coal-water slurry and it was observed that the addition of Fe+2 ions increased the current density by approximately 33% at 80°C and 0.73 V. Doubling the mixing speed increased the current density by 38% at 80°C and 0.3 V

Apparent molar volumes, Vф, of calcium acetate (Ca(Ch3COO)2(aq)) at 273.15 to 353.15 K and pressures up to 100 MPa

Pressure, density and temperature (p, ρ, T) data and apparent molar volumes, Vфo, of aqueous calcium acetate solutions Ca(CH3COO)2(aq) over a wide range of temperatures from 273.15 to 353.15 K, pressures up to p = 100 MPa and molalities m, of 0.04918, 0.09367, 0.23797, 0.36365, 0.85923, 1.06930, 1.35223 and 1.81668 mol⋅kg-1 of Ca(CH3COO)2 are reported. The combined expanded uncertainty of the density (ρ) measurements at the 95 % confidence level with a coverage factor of k = 2 was estimated to be Uc(ρ) = ±0.3 kg∙m‐3. The measurements were realized with an Anton Paar DMA HPM vibration tube density meter. The system was calibrated using double-distilled water, aqueous NaCl solutions, methanol, toluene and acetone. An equation of state for fitting of the (p, ρ, T) data of aqueous calcium acetate was developed as a function of pressure, temperature and molality. After a thorough analysis of literature values and validity of the constructed equation of state, various thermophysical properties, such as isothermal compressibility, isobaric thermal expansibility, differences in isobaric and isochoric heat capacities, thermal pressure coefficient and internal pressure at the investigated state parameter intervals were calculated