Water Absorption Process Research Articles

Analytical investigation of two different absorption modes: falling film and bubble types

The objectives of this paper are to analyze a combined heat and mass transfer for an ammonia–water absorption process, and to carry out the parametric analysis to evaluate the effects of important variables such as heat and mass transfer areas on the absorption rate for two different absorption modes — falling film and bubble modes. A plate heat exchanger with an offset strip fin (OSF) in the coolant side was used to design the falling film and the bubble absorber. It was found that the local absorption rate of the bubble mode was always higher than that of the falling film model leading to about 48.7% smaller size of the heat exchanger than the falling film mode. For the falling film absorption mode, mass transfer resistance was dominant in the liquid flow while both heat and mass transfer resistances were considerable in the vapor flow. For the bubble absorption mode, mass transfer resistance was dominant in the liquid flow while heat transfer resistance was dominant in the vapor region. Heat transfer coefficients had a more significant effect on the heat exchanger size (absorption rate) in the falling film mode than in the bubble mode, while mass transfer coefficients had a more significant effect in the bubble mode than in the falling film mode.

A method of calculation of consistency, technology, and properties of wood composite materials

There is a known method of definition of quantitative parameters of wood elements allowing the determination of the part of specific outer surfaces with cut fibers, Kc.f, and the following specific surfaces: outer (S0), capillary (Sc), and interfibrillary (Sf). On the basis of researches of Niemz et al., the consistencies of kind of wood in wood elements were qualified. Formulas were created for the calculation of theoretical thickness, δ, of bonding substances on surfaces of wood elements. It was shown that δ depends from the following sizes: S0, Sc, and the degrees of covering, θ0 and θc, these surfaces by bonding substances; consistencies of wood and/or agricultural elements, Ce, bonding substances, Cb; and, from a part of bonding substances, Cf, which partly covers Sf and depends from Ce, degree covering, θf, of surface Sf, diameter of fibrillas, df, and densities, ρb, of bonding substances. An exponential dependence between δ and reological characteristics of wood composite materials (WCM) was ascertained. In the process of fabrication of products from WCM, bonding substances penetrate into wood elements according to an equation which is based on the law of Puasel. The effects of Ce, Cb, θ0 and θc on the modulus of elasticity (MOE), Cb, Kt (coefficient of thickness), Kb (coefficient of breadth) on the modulus of rupture (MOR) of molded products from WCM were studied. It was determined that the water absorption of molded products from WCM obey the law of Fick. It was also shown that time τ of the process of water absorption and swelling consists from 3 periods: “incubatory”, proportional √τ to point τp (limit of proportionality), and saturated. It was discovered that after point τp the mechanical properties of molded products from WPC harshly decrease. On the basis of this research more than 142 million of machine/device parts from wood composite materials have been calculated, fabricated, and used.

Modified acrylic bone cement with high amounts of ethoxytriethyleneglycol methacrylate

One cause of arthroplasty failure is the brittle mechanical behavior of bone cements. However, the improvement of cement formulations must also be accompanied by the maintenance of a wide variety of characteristics. New bone cements were obtained by the substitution of high percentages, up to 60% (v/v), of methyl methacrylate (MMA) by a higher molecular weight and more hydrophilic monomer, ethoxytriethyleneglycol methacrylate (TEG). The essential advantages of these materials were the decrease of maximum temperature together with a decrease in the residual monomer content with respect to conventional cement formulations. The water absorption process obeyed diffusion laws and the equilibrium water content increased by the introduction of higher percentages of the hydrophilic component. This characteristic had an appreciable effect on the viscoelastic behavior analyzed by DMTA. These modified bone cements had reduced polymerization shrinkage and similar levels of porosity. Tensile test revealed that the introduction of TEGMA gave rise to an important modification of the mechanical behavior, with a noticeable increase in the fracture strain. This fact was also confirmed by means of the analysis of the fracture surfaces by SEM.

Interpretation of the force deformation curves of soaked red kidney beans (Phaseolus vulgaris L.)

In this study, the textural patterns of red kidney beans soaked in water at 20, 30, 40 and 60 °C are reported. Texture (hardness) was measured instrumentally by cutting with a wedge‐type blade mounted on an Instron Universal Testing Machine at a speed of 200 mm min−1. The general trend of the force deformation curves was similar for all of the soaking temperatures studied throughout the soaking process. At initial stages of hydration, textural changes were a function of the soaking time. However, once the hydration process attained equilibrium, changes in texture became minimal and were within the range of 34 ± 2 N, regardless of the soaking temperature and hydration time. The force deformation curves were influenced by the presence of a large cavity between the two cotyledons of red kidney beans. Interpreting textural patterns of soaked beans would provide a better control of the water absorption process, which subsequently influences changes in texture.

Influence of water absorption by silicate glass on the strains in passivated Al conductor lines

X-ray diffraction strain measurements and elastic recoil detection analysis of aluminum conductor lines, passivated with silicon oxide, showed that the absorption of water molecules in the passivation layer directly influences the strain state in the lines. Volume changes of the passivation due to water absorption lead to unusual strain states, where the line is strained in compression in the width direction and in tension in the height and length direction, with the largest component in the height direction. The process of water absorption, as well as the rearrangement of the strain components in the lines, was found to be reversible.

Capillary penetration in fibrous matrices studied by dynamic spiral magnetic resonance imaging

The dynamic spiral nuclear magnetic resonance (NMR) imaging technique was used to investigate the water imbibition into cellulose fiber matrices. The advancing water boundary, water concentration distribution, and swelling degree within the fiber matrix samples were monitored as a function of time over the entire absorption process. A combined image that shows the time evolution of the absorbed water concentration distribution within the fiber matrix was synthesized from the dynamically acquired NMR image data set. The NMR imaging data clearly demonstrated that water imbibition into a fiber matrix consists of two different processes: water penetration into capillaries between fibers and water diffusion into the cellulose fibers. The advancing liquid front is primarily determined by the water capillary flow and can be quantitatively described by Washburn equation. The slower water diffusion process in fibers is mainly responsible for the fiber swelling. The time evolution of the absorbed water concentration distribution can be qualitatively interpreted in terms of steady capillary flow and concentration-gradient-driven diffusion into fibers with a constant permeability. The effects of pore morphology, tortuosity, and surface heterogeneity to the water absorption process are also discussed.

Long‐term water absorption and swelling of glass‐bead filled plastics

AbstractThe results of experimental and theoretical investigation of epoxy EDT‐ 10/glass‐bead plastics at long‐term (10 years) exposure in water are presented. The curves of water absorption and swelling are determined. It was expected that the addition of hollow glass spheres (beads) must substantially reduce the sorptional capacity of a material, because of reduction of the volume content of the matrix, and therefore, because of reduction of the volume where the molecules of water can diffuse. However, the water absorption process in glass‐bead filled plastics was found to continue during the total term of the experiments without a tendency to stop. After ten years the equilibrium state was not achieved and the concentration of water in the composite specimens became more than the equilibrium concentration of water in unfilled EDT‐10 epoxy. The swelling coefficient was found to be a non‐linear function of water content. It was found that the initial parts of experimental curves of water absorption and swelling (during the first year of exposure) show an agreement with calculated data, good enough for engineering applications. Subsequently the discrepancy between the experimental results and calculated data increased. The possible reasons for such a discrepancy are discussed.

Methane flux from Indonesian wetland rice: The effects of water management and rice variety

Rising levels of atmospheric CO2 affect transpiration and water absorption processes that influence total leaf water potential (ΨW) of wheat (Triticum aestivum L.). The objective of this case study was to determine the effect of a rise in atmospheric CO2 concentration on predawn, midday, and sunset ΨW as soil matric potential (ΨM) ranged from −0.03 to −1.50 MPa. ‘Yecora Rojo’ was sown on 15 December 1992 (130 plants m−2) and 7–8 December 1993 (180 plants m−2) in an open field at Maricopa, AZ (33.1°N, 112.0°W), in air enriched for 24 h per day to a atmospheric CO2 concentration of ∼200 μmol mol−1 (550 μmol mol−1) above ambient (370 μmol mol−1) using a free-air CO2 enrichment (FACE) apparatus (main-plot) in four replicates. A sub-surface drip-tape irrigation system provided two soil–water content treatments: 50% (dry) and 100% (wet) replacement of potential evapotranspiration (split-plot). Treatments were control-dry (CD), FACE-dry (FD), control-wet (CW) and FACE-wet (FW). A pressure chamber was used to measure ΨW on 3–5 upper-canopy fully-expanded sunlit leaves at predawn, midday, and sunset between tillering and hard dough during 1993 and 1994. The ΨW for the dry plots was regressed on ΨM from field capacity (−0.03 MPa) to the permanent wilting point (−1.50 MPa). Slopes (standard error) were derived for CD (ΨW[CD] (MPa) ΨM[CD] (MPa)−1) compared with FD (ΨW[FD] (MPa) ΨM[FD] (MPa)−1) at predawn (5.1 (1.2) compared with 1.1 (0.2)), midday (4.3 (1.8) compared with 0.7 (0.3)), and sunset (5.9 (1.5) compared with 1.0 (0.9)). Regardless of time of day, more negative ΨW for a given ΨM occurred in control compared with FACE (P<0.01). As ΨM ranged from −0.03 to −1.50 MPa, a ∼200 μmol mol−1 rise in atmospheric CO2 concentration resulted in a curvilinearly increase in drought stress alleviation from 0 to 77% at predawn, 0 to 67% at midday, and 0 to 79% at sunset. Hence, as the CO2 concentration of the atmosphere rises, both drought avoidance and tolerance mechanisms will be enhanced resulting in improved water relations in wheat.

Water absorption and swelling of glass/epoxy syntactic foams

The results of experimental and theoretical investigation of glass/epoxy syntactic foams at a long-term (10 years) exposure in water are presented. Specimens for experimental investigation were made from EDT-10 epoxy filled with MSO-779 hollow glass spheres. Seven types of specimens with filler volume fraction varying from 0 to 0.6 were tested. The curves of long-term water absorption and swelling were determined. It was expected that the addition of hollow glass spheres must substantially reduce the sorptional capacity of material because of the reduction of the volume content of the matrix and, therefore, because of reduction of the part of the volume where the molecules of water can diffuse. However, the water absorption process in syntactic foams was found to continue during the total term of the experiments without a tendency to stop. After ten years the limiting equilibrium state was not achieved and the concentration of water in composite specimens became higher than the equilibrium concentration of water in unfilled EDT-10 epoxy. In long-term tests the swelling strain was found to be a nonlinear function of water content. The degree of nonlinearity increased when the volume content of the filler was increased. The calculational prediction of absorption and swelling curves of syntactic foams with different volume contents of the filler was done using the experimentally determined characteristics of absorption of the matrix. The water transport process in the matrix was considered to obey Fick's law. It was found that the initial parts of the experimental curves (during the first year of exposure) show a good enough agreement with calculated data for engineering applications. Subsequently, the discrepancy between the experimental results and calculated data increased and reached such large values that the predicted results became unacceptable. The possible reasons of such discrepancy (breaking of adhesion bonds between the matrix and the filler with subsequent sorption of water at the glass sphere surface, and diffusional filling by water of the inner parts of the damaged glass spheres, etc.) are discussed.

The effects of a water environment on anomalous absorption behavior in graphite/epoxy composites

The effects of a water environment on moisture (H 2O) absorption characteristics of a unidirectional T300/934 graphite/epoxy composite material have been investigated by the measurement and analysis of weight change, hygrothermal induced expansion, surface crack formation, and surface mass loss. Specimens were immersed in distilled water at 45, 60, 75, and 90 °C for more than 8000 h. Weight-change profiles for the composite exhibited divergence from the theoretical Fickian diffusion law. Scanning electron microscopy (SEM) and dimension measurements revealed clear evidence of surface peeling and dissolution of the specimen. A crack/mass-loss model has been used in order to explain the behavior of the composite material during the water absorption process. The general characteristics of water-induced weight gain in graphite/epoxy composites are discussed with respect to the moisture diffusion phenomenon and deviations in the weight-change profiles.

Imbibition Response of Winter Wheat to Water‐Filled Pore Space

AbstractReduced temperature and increased bulk density associated with conservation tillage systems cause lower seed germination, seedling emergence, and early growth rates resulting in reduced plant stands. Prediction of the influence of soil condition on seed imbibition through simple soil measurements would help make agronomic decisions such as planting date and/or density. Our objectives were to evaluate the influence of soil water‐filled pore space on winter wheat (Triticum aestivum L.) seed imbibition and to assess the possibility of describing the relationship through simple mathematical models. We measured the rate of water uptake by heat‐killed wheat seeds at three levels of water‐filled pore space (WFPS: 0.35, 0.60, and 0.85) and temperature (T: 278, 283, and 288 K) and two levels of bulk density (ρb: 1.25 and 1.40 Mg m−3) in a Sharpsburg silty clay loam topsoil. The model proposed in 1972 by Blacklow to estimate seed water content (θs) after imbibing water for time t, θs(t) = (m + ot) − (m − θs(0)) e−qt, was fitted to seed water content as a function of time and initial seed water content, θs(0). This equation adequately described the process of water absorption (for 18 treatment combinations, R2 &gt; 0.963). The model parameter o was related (R2 = 0.88) to WFPS and ρb, and q was related (R2 = 0.78) to T and WFPS. The third parameter, m, was significantly but weakly related (P &lt; 0.01, r2 = 0.26) to initial seed weight. We showed that easily measured soil properties and simple mathematical models can be used to predict wheat seed imbibition under a variety of soil conditions.

ＳＭＣ材の疲労特性に及ぼす水吸収の影響とその劣化機構

FRP (Fiber Reinforced Plastics) are most popular and widely used materials among various kinds of composites. In many kinds of FRP composites, SMC materials are frequently used as materials for various equipments. Most SMC materials are also used in various environmental conditions, such as water, ultraviolet rays, oxgen and so on. Among these conditions, water environment is a usually surrounding one around these materials and it strongly influences SMC materials' properties. Therefore, in this paper, the effects of water absorption on the fatigue properties and inner structural changes of SMC materials were investigated. In this study, SMC material composed of bis phenol A unsaturated polyester resin and E-glass chopped strand mat was used. Voids which were generated during molding process were recognized to exist in the central layer of SMC material. SMC specimens absorbed 3.0% water after 10800 hours immersion into deionized water at 30°C, and the water absorption process is shown to follow Fick's law. Fatigue life in water environment of SMC material becomes extremely short comparing to that obtained in air. As the results of SEM observation and EPMA (Electron Probe Micro Analyzer) analysis on the fracture surface, it was made clear that the absorbed water in SMC material reacted with calcium carbonate which was distributed in the matrix resin as filler. Then, the absorbed water penetrating through the dissolution regions. into inner sites caused the degradation of interfacical bonding between fiber and matrix in SMC material.

Modelling the process of absorption and desorption of water by coatings made of epoxy resin

The behaviour of coatings made of epoxy resin when in contact with water at 80° is studied. The process of water absorption is controlled by transient diffusion with a constant diffusivity, and 4% of water is absorbed at equilibrium. The drying process of the pre-saturated resin is controlled by transient diffusion through the resin and evaporation from the surface. At the end of the drying at 80°, c 16% of the initial water remains in the resin. If after drying the resin is immersed a second time in water, at 80° a higher rate of absorption with a higher diffusivity is observed. Mathematical models, with analytical expressions as well as mathematical models, are successfully tested for the processes of absorption and desorption.

Effect of galactose on auxin-induced cell elongation in oat coleoptile segments in mannitol solutions

Oat coleoptile segments were treated with or without 10 mM galactose in the presence or absence of 10 μM IAA and various concentrations of mannitol (pre-incubation). Auxin-induced growth was inhibited by galactose. Segments were then transferred to buffer solutions containing or not containing 10 mM galactose (post-incubation). Expansion growth due to rapid water absorption was observed. The expansion growth during the post-incubation was inhibited by galactose when galactose was applied during the post-incubation period or all through the pre- and post-incubation but was not affected by galactose when it was applied only during the pre-incubation. This result indicates that the galactose effect on the expansion growth is due to its inhibitory action during the post-incubation period. Galactose has been reported to be a specific inhibitor for cell wall synthesis. Thus, it is suggested that the expansion growth during post-incubation requires cell wall synthesis and is not just the process of passive water absorption. The primary action of auxin does not seem to require new synthesis of polysaccharides.

Infrared studies of water induced conformational changes in bacteriorhodopsin

Fourier transform infrared difference spectroscopy has been used to study the effect of water on the conformation of bacteriorhodopsin. The infrared spectra as a function of water content show a conformational change at about 0.06 g H2O/g bacteriorhodopsin. By an interference method the thickness of the sample was measured and shows similar behavior as a function of water content. This study gives insight into the process of water absorption by purple membrane. The observations are in good agreement with those found for other proteins.

β-Aluminas and water

TG, DSC and X-ray measurements were made to characterize the water absorption process by Li (50%) — Na (50%)β-alumina.The equilibrium water content, dehydration enthalpies and lattice parameter values have been determined and compared with those previously obtained for pure Li and Naβ-aluminas.The mixedβ-alumina is shown to be very similar to Liβ-alumina as concerns the dehydration enthalpy and the temperature range in which the dehydration occurs, while it seems to be very similar to Naβ-alumina with respect to the equilibrium water content andc-axis values.

A Thermogravimetric and NMR Study of β-Aluminas

Abstract The Na+ tracer diffusion coefficient and the 27Al NMR spin lattice relaxation time in Na β-alumina display an anomalous temperature dependence near 470 K. These phenomena are related to absorption of water which takes place when the temperature is decreased below 470 K. Water absorption processes in pure and partially substituted β-aluminas are studied by thermogravimetric analysis. Their effects upon conductivity are qualitatively discussed.

Mechanism of inhibition of the proximal tubular isotonic fluid absorption by polylysine and other cationic polyamino acids

The present study was initiated with the hope of clarifying the role of negative charges in the luminal brush border membrane in the overall process of trans-epithelial isotonic sodium and water absorption. Using micropuncture techniques, cationic polyamino acids such as polylysine (mol wt 100,000, 17,000 and 1,500-5,000, 1 mg/ml), tetralysine, polyornithine (mol wt 100,000, 1mg/ml), polyethyleneimine (2 mg/ml), polymyxin B (2 mg/ml), protamine sulfate (25 mg/ml) and histone (0.5 mg/ml) were perfused through the segments of rat kidney proximal tubule for 30 sec to 2 min. The rate of isotonic fluid absorption was measured before and after each perfusion with the Gertz's split drop method using Ringer's solution as a shrinking drop. Polylysine 100,000 and 17,000 and polyornithine were the most potent, inhibiting isotonic reabsorption by 93%. The sequence of inhibitory effect was: polylysine 100,000 congruent to polyornithine 100,000 congruent to polylysine 17,000 greater than polyethyleneimine greater than polylysine 1,500-5,000 congruent to polymyxin B greater than protamine sulfate congruent to histone. In contrast, tetralysine (2 mg/ml) showed no inhibitory effect. Electrical potential difference (p.d.) of the proximal tubular cells was destroyed within 10 sec of luminal perfusion with polylysine 100,000 (1 mg/ml). Simultaneously with the drop in p.d., electrical resistance of the luminal brush border membrane was nearly totally eliminated, whereas transepithelial input resistance remained unaltered. Furthermore, trypan blue dye was taken up by polylysine 100,000-perfused tubular cells but not by normal cells. Expanding drop analysis (mannitol solution as a split drop) was performed as a screening test to examine if the permeability for water and sodium in the lateral paracellular pathway is altered by polylysine 100,000. No significant difference was observed in the velocity of split drop expansion between untreated and polylysine-perfused tubules. A lower concentration of polylysine 100,000 (0.1 mg/ml) showed a much less inhibitory effect on fluid absorption and on cell p.d. These observations indicate that the strong inhibition on proximal tubular fluid absorption exerted by polylysine and perhaps also by other cationic polyamino acids is due not to modification of membrane negative charges but to the lysis of tubular cells by these polycations.

Influence of Hydraulic Properties of Soil on Pre‐Germination Water Absorption by Rapeseed (Brassica napus)1

AbstractStudies were conducted to determine the influence of soil water potential and hydraulic conductivity on pregermination water absorption by rapeseed under different seed densities and geometries. In all seed densities and geometries, water absorption rate was reduced with each decrease in water potential. Hydraulic conductivity had an important influence on the water absorption process. Soil water potential at which soil hydraulic conductivity became important was dependent upon seed density and geometry and was associated with hydraulic conductivitywater content relation of the seed.

The absorption of water by acrylic resins and other materials

The absorption and desorption of water by acrylic resin obeys the mathematical laws of diffusion. This means that there are two physical parameters necessary to define the water absorption or desorption process, namely the diffusion coefficient and the equilibrium concentration. The former parameter only governs the time necessary to saturate or “dry-out” an appliance, so is clearly a physical property of great importance. Temperature has a marked effect on the diffusion coefficient (it increased by a factor of two to three in the temperature range 22.5 °C. to 37.4 °C.), but has no effect on the equilibrium water content. It follows, therefore, that the time required to saturate or dry-out an appliance will depend markedly on temperature. As the water absorption and desorption processes obey the mathematical laws of diffusion, the time required to saturate or dry-out appliances (and hence the time for accompanying dimensional changes to occur) can be predicted. Such times appear to be much larger than those allowed for in practice; for example, the usual forty-eight hours immersion of a crown before insertion is inadequate, especially if cold water is used. Also, the critical dependence of these times on appliance thickness does not appear to be generally realized.