Temperature-Variations In Drying of Sulfuric-Acid-Solutions In Sand Beds .2. Temperature-Variations In the Bed During the Drying of Water-Sulfuric Acid Mixtures

WOS: A1995RL02600014Temperature distributions were used to explain the drying behavior of sulfuric acid solutions in packed sand beds in this part of the investigation. Temperature of the acid solutions in free evaporation are expected to increase during drying due to the decrease in heal capacity with increase in concentration. Deviations of concentration from those expected from the solution temperatures were attributed to the effects of the convective motion induced by the increase of density and surface tension of the acid solutions. These effects were found to be superimposed on the temperature variations in porous beds determined in the first part of this paper[1]

Temperature-Variations In Drying of Sulfuric-Acid-Solutions In Sand Beds .1. Temperature-Variations In the Bed During the Drying of Water

WOS: A1995RL02600013Local temperature variations were determined in sand beds during drying. Two different particle sizes of 200 mu m and 550 mu m's were used in the experiments. Drying was conducted at 80 degrees C and 150 degrees C. Highest temperature were observed at the bottom of the bed due to capillary lift during drying at 80 degrees C. Rapid evaporation at 150 degrees C ambient temperature caused heat to be transferred from both the surface and bottom of the bed, so the coolest section was at the center. Isothermal conditions were approached as the capillary size increased as in 550 mu m particle beds

Effect of pH on the surface and interfacial behavior of rhamnolipids R1 and R2

WOS: 000220552600018Surface and interfacial tensions of pure R1 and R2 solutions at the pH values of 6.8 and 5 were comparatively studied in this work, with decane and hexadecane as the oil phase. Conductivities were measured as a function of concentration to supplement the surface tension results. Photographs of these solutions under cross-polarized light were taken to show the existence of liquid crystals. Foaming ability and stability of pure rhamnolipid solutions were determined using a modified Bikerman device. Results of the measurements showed that R1 and R2 molecules form compact phases at the surface beginning from very low concentrations. R1 molecules are more surface active at concentrations below CMC independent of the bulk phase pH. Nevertheless, neither the value of CMC nor the minimum surface tension at CMC is affected by the type of rhamnolipid significantly. These depend only on the pH of the solution, since greater interactive forces exist between the undissociated rhamnolipid molecules at pH = 5.0 resulting in a greater compaction at the surface monolayer. The interfacial behavior of R1 and R2 molecules at concentrations below CMC differ considerably with the structure of the molecules with which they interact at the interface: R1 molecules are more capable of reducing the interfacial tension than R2 when using decane as the oil phase instead of hexadecane. Strong intermolecular interactions between rhamnolipid molecules allow foam formation to occur only in a narrow range of air flow rates. Stability of the foam depends on the rhamnolipid type with R1 forming more stable foams. Maximum foam volume depends on the pH of the solution and not on the type of rhamnolipid. (C) 2003 Published by Elsevier B.V

Drying Behavior of Mushroom Slices

WOS: A1990CZ3430000

Effect of electrolytes on the surface behavior of rhamnolipids R1 and R2

WOS: 000222172100011PubMed ID: 15261035The surface behavior of solutions of the rhamnolipids, R1 and R2, were investigated in the absence and presence of an electrolyte (NaCl) through surface tension measurements and optical microscopy at pH 6.8. The NaCl concentrations studied are 0.05, 0.5 and 1 M. Electrolytes directly affect the carboxylate groups of the rharmolipids. The solution/air interface has a net negative charge due to the dissociated carboxylate ions at pH 6.8 with strong repulsive electrostatic forces between the rhamnolipid molecules. This negative charge is shielded by the Na+ ions in the electrical double layer in the presence of NaCl, causing the formation of a close-packed monolayer, and a decrease in CMC, and surface tension values. The maximum compaction is observed at 0.5 M NaCl concentrations for R1 and R2 monolayers, with the R1 monolayer more compact than R2. The larger spaces left below the hydrophobic tails of R1 with respect to that of R2, due to the missing second rhamnosyl groups are thought to be responsible for the higher compaction. The rigidity of both R1 and R2 monolayers increases with the electrolyte concentration. The rigidity of the R1 monolayer is greater than that of R2 at all NaCl concentrations due to the lower hydrophilic character of R1. The variation of CMC values as a function of NaCl concentration obtained from the surface tension measurements and critical packing parameter (CPP) calculations show that spherical micelles, bilayer and rod like micelles are formed in the rhamnolipid solutions as a function of the NaCl concentration. The results of optical microscopy supported these aggregation states indicating lamellar nematic liquid crystal, Cubic lamellar and hexagonal liquid crystal phases in R1 and R2 solutions depending on the NaCl concentration. (C) 2004 Elsevier B.V. All rights reserved

The dynamic surface tension of atmospheric aerosol surfactants reveals new aspects of cloud activation

The activation of aerosol particles into cloud droplets in the Earth's atmosphere is both a key process for the climate budget and a main source of uncertainty. Its investigation is facing major experimental challenges, as no technique can measure the main driving parameters, the Raoult's term and surface tension, σ, for sub-micron atmospheric particles. In addition, the surfactant fraction of atmospheric aerosols could not be isolated until recently. Here we present the first dynamic investigation of the total surfactant fraction of atmospheric aerosols, evidencing adsorption barriers that limit their gradient (partitioning) in particles and should enhance their cloud-forming efficiency compared with current models. The results also show that the equilibration time of surfactants in sub-micron atmospheric particles should be beyond the detection of most on-line instruments. Such instrumental and theoretical shortcomings would be consistent with atmospheric and laboratory observations and could have limited the understanding of cloud activation until now

Assessment of Shoreline Changes using Historical Satellite Images and Geospatial Analysis along the Lake Salda in Turkey

WOS: 000527535700001This study was performed along the shorelines of Lake Salda in Turkey during the elapsed period from 1975 to 2019 in order to detect shoreline changes. Within this framework, geographic information system, digital shoreline analysis system, Modified Normalized Difference Water Index, and multi-temporal satellite images were utilized. The measurement of shoreline displacement was mainly divided into six analysis regions. In digital shoreline analysis system, several statistical parameters such as end point rate, linear regression rate, shoreline change envelope, and net shoreline movement were computed to measure the rates of shoreline displacement in terms of erosion and accretion. The maximum shoreline change between 1975 and 2019 was determined as 556.45 m by shoreline change envelope parameter. The maximum shoreline change was 16.35 m/year by end point rate parameter and 12.91 m/year by linear regression rate parameter. While erosion has been observed in 3rd, 4th and 6th segments, accretion has been observed in other segments. When all the transects were taken into consideration, an accretion observed. The results indicate that there is a decrease in area of the lake. Experiment results show that integrated use of multi-temporal satellite images and statistical parameters are very effective and useful for shoreline change analysis. It is thought that the structures such as irrigation pond and dam that are built on the streams that recharge the lake and average rainfall and average temperature conditions are the main reasons of the fluctuations and changes in the shorelines