The drying kinetics of seeded grape in solar dryer with PCM-based solar integrated collector

This paper presents a novel type of dryer for experimentally evaluating the drying kinetics of seeded grapes. In the developed drying system, it has been particularly included an expanded-surface solar air collector, a solar air collector with phase-change material (PCM) and drying room with swirl element. An expanded-surface solar air collector has been used to achieve high heat transfer and turbulence effect whiles a solar air collector with PCM has been used to perform the drying process even after the sunset. On the other hand, the swirl elements have been located to give the swirl effect to air flow in drying room. These advantages make the proposed novel system a promising dryer in that lower moisture value and less drying time. The drying experiments have been carried out simultaneously both under natural conditions and by the dryer with swirl flow and without swirl flow at three different air velocities. The obtained moisture ratio values have been applied to six different moisture ratio models in the literature. The model having the highest correlation coefficient (R) and the lowest Chi-square (χ²) value has been determined as the most relevant one for each seeded grape drying status.     

AIRFLOW RESISTANCE OF OAT SEEDS: EFFECT OF AIRFLOW DIRECTION,MOISTURE CONTENT AND FOREIGN MATERIAL

ABSTRACT

Pressure drops through oat (Oat Sp.) beds were evaluated in the range of airflow rate from 0·0097 to 0·459 m³/s-m² using two airflow directions to determine the effect of grain moisture and foreign material on the resistance to airflow. Horizontal airflow resistance was lesser than vertical airflow resistance (e.g., for oat with 9·0% moisture content the pressure drop in horizontal direction was 4–17% of corresponding in vertical direction). The resistance decreased with the increase of moisture content and increased when the fraction of foreign material. An increase in the moisture content from 9·0 to 24·9% produced a decrease on the bulk density from 583 to 513 kg/m³. Mattel's model (1969) fitted adequately the experimental data. The Haque et al.'s equation (1982) have an adequate representation of the data for both airflow directions. The Paterson et al. (1971) and Bern-Charity (1975)equations resulted applicable only for vertical airflow direction. A simplification planed of this model in function of the bulk density conduced to a good relation DP-Q.     

The Effect of Flocculants and Surfactants on the Filtration Dewatering of Iron Ore Fines

Abstract

The filtration and separation characteristics of iron ore fines have been investigated. The experimental work included: characterization, evaluation of suitable flocculants to enhance settling and dewatering rate, determination of optimum dosages of flocculants, and influence of surfactants on nitration dewatering of both flocculated and unflocculated iron ore fines by vacuum filtration. The results showed that 1) the settling rate can be enhanced many-fold (from 2.52 to 90 m/h) by a suitable flocculant, 2) the residual filter cake moisture content can be reduced from 18.2% without reagents to 12.6% with suitable surfactant dewatering aids while the filtration rate can be enhanced from 4.8 to 97.2 L/h with suitable dewatering filter aids, and 3) the specific cake resistance to filtration can be brought down from 8.6 × 10⁹ to 1.0 × 10⁹ m/kg by using a surfactant sodium petroleum sulfonate at a concentration of 1.47 × 10^?3 kg/t. The economics of using flocculant filter aids and surfactant dewatering aids before thermal drying is described and discussed.     

Effective Diffusivity Determination Considering Shrinkage by Means of Explicit Finite Difference Method

Drying data of salted shark (Carcharhinus limbatus) muscle pieces samples, dried in a convective dryer, by using three different air conditions and two different air velocities, were treated by Fick's second law. The shrinkage during drying process was considered as a linear function of sample moisture. The Fick's second law equation was numerically solved by the explicit finite difference method to obtain effective diffusivity, considering shrinkage and with and without simplification of moisture content profile. The experimental data fitted very well independently of the simplification introduced on the moisture content profile. The best fit was obtained by considering volumetric average of sample moisture content. The effective diffusivity values calculated considering the shrinkage varied from 0.72 to 2.20 × 10^?10 m²/s with the mean relative deviation modulus from 1.02 to 6.51%. The activation energy expressed in function of air temperature varied from 3.42 to 19.23 kJ/mol.     

Reactivity of Hydroxamate Ions in Cationic Vesicular Media for the Cleavage of Carboxylate Esters

The hydrolysis of carboxylate esters viz. p‐nitrophenyl acetate (PNPA), p‐nitrophenyl butyrate (PNPB) and p‐nitrophenyl octanoate (PNPO) in the presence of cationic vesicles of the surfactant dioctadecyldimethylammonium bromide (DODAC) by different hydroxamate ions i.e. acetohydroxamate (AHA^?), benzohydroxamate (BHA^?) and salicylhydroxamate (SHA^?) were studied. The kinetic data was supported by spectrophotometric measurements. The effects of vesicular size on the reaction have been discussed. The differential reactivity under endo‐ and exovesicular conditions has also been evaluated. Critical vesicle concentrations (CVC) of cationic vesicular surfactants were determined from conductometric and fluorimetric measurements at 300 K. Fluorescence probe pyrene and pyrene‐1‐carboxaldehyde have been used for determination of CVC. Further, thermodynamic parameters viz. Standard Gibb's energy (?G°), enthalpy (?H°), and entropy (?S°) of vesicles has also been evaluated within a temperature range of 303.15–328.15 K.     

Settling length for turbulent flow of air in an annulus

The settling length, or distance downstream from the entrance required for the development of the velocity profile, has been determined for four square entrance sectioned annuli, with diameter ratios of 0.2, 0.3, 0.5 and 0.7. Using air, a Reynolds number range of 5,000 to 50,000 was covered, and correlations have been obtained relating the settling length, equivalent diameter, Reynolds number and diameter ratio. The expression L/De = 0.795 R_e³⁷⁴(D₁/D₂)^?0.60 correlated the data for Reynolds numbers lower than 22,000 and for Reynolds numbers greater than this the relation was L/D_e = 15.96 R_e^.077(D₁/D₂)^?624.     

Ultrasonic properties of polystyrene-based composites

In this study, first the pure polystyrenes (PS) with different molecular weights (350 × 10³ and 500 × 10³) have been modified by the chemical modification with succinic anhydride (SA), maleic anhydride (MA), and phthalic anhydride (PhA) and then the polystyrene based composites (CPS) prepared by addition of modified polystyrenes (MPS) into pure PS (with the molecular weight of 230 × 10³) in weight % ratios of 90 : 10, 80 : 20, and 70 : 30. Ultrasonic measurements were performed on PS/MPS blends of different weight percent of MPSs by use of pulse echo method with 5-MHz frequency at room temperature. Elastic properties namely; longitudinal modulus (L), Young's modulus (E), bulk modulus (K) and shear modulus (G), Poisson's ratio (μ), and acoustic impedance (Z) were calculated from the ultrasonic velocities values measured and densities values obtained experimentally. Atomic force microscopy (AFM) has been used for determining the microstructure of composites. The variations of these parameters with increasing MPSs weight percentage content in PS/MPS from 10 to 30 have been discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Development and evaluation of a novel pH indicator biodegradable film based on cassava starch

A pH indicator film based on cassava starch plasticized with sucrose and inverted sugar and incorporated with grape and spinach extracts as pH indicator sources (anthocyanin and chlorophyll) has been developed, and its packaging properties have been assessed. A second‐order central composite design (2²) with three central points and four star points was used to evaluate the mechanical properties (tensile strength, tensile strength at break, and elongation at break percentage), moisture barrier, and microstructure of the films, and its potential as a pH indicator packaging. The films were prepared by the casting technique and conditioned under controlled conditions (75% relative humidity and 23°C), at least 4 days before the analyses. The materials were exposed to different pH solutions (0, 2, 7, 10, and 14) and their color parameters (L*, a*, b*, and haze) were measured by transmittance. Grape and spinach extracts have affected the material characterization. Film properties (mechanical properties and moisture barrier) were strongly influenced by extract concentration presenting lower results than for the control. Films containing a higher concentration of grape extract presented a greater color change at different pH's suggesting that anthocyanins are more effective as pH indicators than chlorophyll or the mixture of both extracts. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on molecular transport of n‐alkanes through poly(tetrafluoroethylene‐co‐propylene) elastomeric membrane

Molecular transport of a series of n‐alkanes through commercial TFE elastomer (FA 150L) has been studied in the temperature range 30–50 °C using sorption‐gravimetric method. The Fickian diffusion equation was used to calculate the diffusion coefficients, which were dependent on the size of the alkanes and temperature. The diffusion coefficients at 30°C varied from 4.53 × 10^?8 cm²/s (n‐heptane) to 0.18 × 10^?8 cm²/s (n‐hexadecane). The liquid concentration profiles have also been computed using analytical solution of Fick's equation with the appropriate initial and boundary conditions and these were presented as a function of penetration depth of molecular migration and time of immersion. These results have been discussed in terms of molecular size of alkanes as well as temperature. In all the liquid penetrants, the transport phenomenon was found to follow the anomalous behavior. From the temperature dependence of diffusion and permeation coefficients, the Arrhenius activation parameters have been estimated. These parameters do not exhibit any systematic variation with the size of the penetrants. The resulting low diffusion coefficients, contribute to the superior barrier performance of the membrane, is due, in part, to the high glass transition temperature of Aflas? TFE elastomer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2228–2235, 2006     

Drying Kinetics of Apple Tissue Treated by Pulsed Electric Field

The aim of this work was to study the influence of pulsed electric field (PEF) on the drying kinetics of apple tissue. Therefore, mathematical models that are commonly used in the literature were applied to describe the process. PEF treatment of the samples was carried out at an intensity of E = 5–10 kV/cm and 10–50 pulse numbers. Subsequently, the apples were convectively dried at 70°C and air velocity of 2 m/s. Based on electrical conductivity measurement, the cell disintegration index Z _p was computed. Midilli et al.'s(Drying Technology, Vol. 20, pp. 1503–1513, 2001) model was evaluated as the most adequate to describe the moisture transfer in PEF-treated and intact samples. PEF pretreatment induced a reduction in drying time of up to 12% when 10 kV/cm and 50 pulses were applied. For instance, after 60 min of drying, the dimensionless moisture ratio for PEF-treated (10 kV/cm, 50 pulses) samples was 0.18 compared to 0.26 for the untreated apples. The effective moisture diffusivity, calculated on the basis of the Fick's second law, was 1.04 × 10^?9 m/s for intact samples and from 1.09 × 10^?9 to 1.25 × 10^?9 m²/s for PEF-treated samples at 10 pulses at 5 kV/cm and 50 pulses at 10 kV/cm, respectively.     

On the use of residence time distributions for the design of clarifiers

Use of residence time distributions (RTD's) for the design of clarifiers proposed by the senior author in 1969 and by others has been found to be based on flow pattern assumptions which are false. Since the residence time distribution depends upon the density of the feed to the clarifier, flow rate and other near-intangibles, it is not possible to obtain RTD's which pertain to an operating settler from which reliable performance may be predicted. Finally, laboratory studies demonstrate that the combination of RTD's and quiescent settling data do not reliably predict clarifier performance.     

Bi-layer gelatin active films with “Pitanga” leaf hydroethanolic extract and/or natamycin in the second layer

Research on biopolymers-based active films produced with natural antioxidants and/or antimicrobials has gained attention over the last few years; however, anti-mold activity has been less studied than those of anti-bacteria. The aim of this work was the development and characterization of bi-layer films based on gelatin with natamycin and/or “Pitanga” leaf hydroethanolic extract in the second thin layer in order to determine the effects of these bioactive compounds on bi-layered film properties. The films were characterized regarding their moisture content and solubility in water, optical properties, microstructure, mechanical and thermal properties, water contact angle, water vapor permeability, UV/visible light transmission, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and antioxidant and anti-mold activities. Active films presented activity against Penicillium spp and Aspergillus niger and demonstrated antioxidant activity, as measured by ABTS ^•+ and DPPH ^• methods. Neither additive used in the films' second layer significantly affected the films' moisture content, thermal properties or the molecular interactions of the polymer matrix, assessed by FTIR, although some mechanical properties were affected, and the water contact angle. In conclusion, bi-layer films have reduced the quantity of additives required to maintain the antioxidant and anti-mold activities, as compared to similar monolayer films of the same thickness.     

Osmotic Dehydration of Apple Cylinders: II. Continuous Medium Flow Heating Conditions

Mass transfer of apple cylinders during osmotic dehydration was quantitatively investigated under continuous medium flow conditions. The influences of the main process variables (solution concentration, operation temperature, contact time, and solution flow rate) were determined. A second-order polynomial regression model was used to relate weight reduction (WR), moisture loss (ML), solids gain (SG), and mass diffusivity (D _m and D _s ) to process variables. The conventional diffusion model using a solution of Fick's unsteady state law involving a finite cylinder was applied for moisture diffusivity and solute diffusivity determination. Diffusion coefficients were in the range of 10^?9–10^?10 m²/s, and moisture diffusivity increased with temperature and flow rate, increased with solution concentration (> 50°Brix), and decreased with increasing solution concentration (< 50°Brix), but solids diffusivity increased with temperature and concentration and decreased with increasing flow rate. A continuous-flow osmotic dehydration (CFOD) contactor was developed to be a more efficient process in terms of osmotic dehydration efficiency: time to reach certain weight reduction (T _w ) and moisture loss (T _m ) were shorter than that of conventional osmotic (COD) dehydration processes. Effectiveness evaluation functions used in this study could be widely applied to osmotic dehydration system evaluation.     

Moisture absorption phenomenon in permeable fiber polymer composites

Studies were conducted on the moisture absorption characteristics of jute fiber composites based on polyester and epoxy resin systems, under constant humidity (ø) and ambient temperature (T) conditions. The initial slope of the moisture absorption curve (a direct measure of the composite diffusivity) increased with increased superficial fiber volume fraction (V_f), where as the time (t_m'), needed to reach the equilibrium moisture absorption value showed a reversed trend. This behavior is just a reverse to that observed¹ in case of composites with practically impermeable fibers (e.g., glass and graphite) in the same resin matrices. The theoretical expressions governing moisture diffusion phenomenon in impermeable fiber composites were modified and analyzed for the case of composites containing a permeable fiber. The experimental data obtained on the latter were then discussed in relation to the modified theory. The meaning of a correct fiber volume fraction (V_f,) as applicable to permeable fiber composites was defined.     

The effect of silane hydrolysis on aluminum oxide dispersion stability in ceramics processing

The controlled hydrolysis of organosilanes has been shown to greatly influence both the surface adsorption of silanes on alumina powder, and the resultant dispersion stability of alumina in organic solvent slurries. Plateau adsorption concentrations from settling experiments show that complete surface coverage for hydrolyzed forms of both n-octyltrimethoxysilane (NOS) and N-2-aminoethyl-3-aminopropyltrimethoxysilane (AAPS) is typically achieved at concentrations of approximately 6 μmol/m². Moreover, the settling densities of dispersions prepared with hydrolyzed silanes are consistently higher than densities achieved with monomeric silanes alone (as seen in case studies involving NOS in toluene, and AAPS in isopropyl alcohol). Similarly, ceramic slips prepared with polystyrene and alumina, or with poly(isobutyl methacrylate) and alumina also lead to ceramic green bodies with increased densities when the slips are prepared with hydrolyzed silanes. In addition, solid state NMR and dynamic mechanical analyses of resultant green bodies reveal that the molecular motional behavior of these polymers is strongly influenced by the presence of hydrolyzed silanes. These results collectively add to a growing body of evidence which supports the idea that not only is hydrolysis required for silanes to produce controllable and predictable effects in many industrial processes, but hydrolysis must be made to occur at the 'right time' within any sequence of steps that define an industrial process. In the case of ceramic slurries, the 'right time' is the period just prior to the mixing of the ceramic slip ingredients.     

A Comparison of Some Mathematical Models Used for the Prediction of Mass Transfer Kinetics in Osmotic Dehydration of Fruits

Mass transfer in osmotic dehydration of fruits at atmospheric pressure has been modeled either by a phenomenological approach using Crank's model (which is a Fick's law solution) or empirically, using models developed from polynomial equations, mass balances, or relations between process variables (i.e., Magee's, Azuara's, and Page's models). For all of these models, experimental data are required to determine the values of their adjustable parameters for specific processing conditions. From a wide variety of published data, the parameters for moisture loss (ML) and solid gain (SG) were calculated for the above-mentioned models, and a comparison of their correlation capability was made. Azuara's and Page's models yield better correlations (with mean absolute errors less than 1.26% for ML and 0.46% for SG) than Magee's and Crank's models (with mean absolute errors of up to 2.98 and 1.68% for ML and SG, respectively).     

Influence of water content of the pulp on the extraction and the physicochemical properties of Canarium schweinfurthii oil

With the aim of contributing to the valorization of the Canarium schweinfurthii Engl. fruit pulp, through the extraction of its oil, we have studied the influence of the Canarium pulp's water content after drying at 45 °C on the yield of extraction using hexane. Furthermore we studied the physicochemical properties of the oil. It was observed that the oil's extraction yield is significantly influenced (p <0.01) by water content of the pulp. Maximum extraction yield (30.6 g fat/100 g) is obtained at a moisture content of 6.3%. The acid, saponification and peroxide values of the oils obtained were significantly influenced (p <0.05) by the humidity. The maximum acid values of 8.88 corresponded to a moisture content of 17.5%. Likewise, the saponification value showed a maximum of 154.1 for humidity content of 43.3% at the beginning of the drying step. The pulp oil's peroxide value initially at 3.7 meqO₂/kg increased progressively until attaining 51.0 O₂/kg at the end of drying. The iodine value was not influenced by humidity. A moisture content of 7.7% has been determined as the optimal value for optimizing both oil extraction yield and physicochemical property of the oil obtained.     

The Rheology of Peat/Solvent Slurries

Slurries of finely milled Irish peat in Shell White Spirit (100F) were prepared and their rheological behaviour was evaluated in terms of shear rate, solids concentration, moisture content and particle size distribution of the solids. The moisture content of the peat was found to be of crucial significance in determining both the effective solids concentration and the stability of the suspensions. The viscosity of slurries composed of 7% moisture peat solids were almost independent of solids concentration and displayed Newtonian rheological behaviour, with a viscosity of approximately 0·012 N s m⁻². The viscosity of the suspending medium was 1·006×10⁻³ N s m⁻² at 20±1°C. The viscosity of the slurries composed of 55% moisture peat solids was observed to rise sharply, up to about 0·10 N s m⁻² with solids concentration. The shear rate dependence of these suspensions was more complex and their flow characteristics were evaluated in terms of empirical non-Newtonian models. It proved difficult to confidently distinguish between the Bingham Plastic and Casson models as each gave best fit regression curves which were almost identical. Particle size distribution analysis of the suspensions indicates the formation of peat aggregates in the 55% moisture samples which exhibited more rapid settling of the solid. © 1997 SCI     

Theoretical and experimental investigations of molecular migration and diffusion kinetics of organic esters into tetrafluoroethylene/propylene copolymer membranes

A theoretical analysis of the experimental results on the migration and diffusion kinetics of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate and iso-amylacetate into tetrafluoroethylene/propylene copolymer membranes has been made. Diffusion and permeability coefficients have been calculated from Fick's equation. The concentration profiles of the liquids have been calculated from a solution of Fick's equation as well as using an empirical relation for the esters into the varying penetration depths of the membranes at different time intervals. The diffusion coefficients show a systematic decrease with increasing size of esters and the results are discussed in terms of the membrane-solvent interactions.