Equilibrium Humidity Research Articles

Hygroscopic behavior of noni leaf powder (Morinda citrifolia L.) obtained by drying in foam layer

Studies on the ethnicbotanical aspect and properties of noni (Morinda citrifolia L.) reveal that noni leaves contain chemical compounds that are related to antibacterial, antioxidant, antiviral, antifungal, antitumor, anthelmintic, analgesic, inflammatory, hypotensive and immunostimulating, among these compounds are, for example, flavanoid glycosides. The drying process is, in turn, used as a way of preserving perishable products, such as plants, due to the removal of water available for microbial deterioration, keeping the properties of the material preserved. For proper storage and increasing the shelf life of the powder obtained after the drying process, it is important to know the adsorption isotherms. This study aims to survey the adsorption isotherms of powders obtained from noni leaves. The powders to be analyzed were obtained through the foam layer drying process in the maximum, minimum and central factorials of the complete experimental planning of previously carried out studies. For the mathematical adjustment of the obtained isotherms, three different mathematical models from the literature were tested, based on experimental moisture adsorption data, for non-linear regression analysis, using the Gauss-Newton and Levenberg-Marquardt methods. The isosteric heat of the powders was also calculated to understand the behavior of the adsorbed phase with temperature variation, in addition to the affinity between adsorbate and adsorbent. The noni leaf powder showed high hygroscopicity, ranging from 0.098 to 0.969 and the Oswin model was the one that best represented empirical adjustments describing the process. The isotherms were classified as Brunauer Type III. It was also possible to infer that the energy required to remove water present in the noni leaf powder decreases with increasing equilibrium humidity.

Thermodynamics of interaction of inulin complex with water

Currently, the key trends in the global food market include the rapidly developing functional nutrition industry, which is of great interest to consumers. Inulin is a natural polysaccharide of plant origin, consisting of residues of E-fructofuranose (fructose). The object of the research is inulin extract from Jerusalem artichoke at different humidity levels. It has been established that to intensify the drying process of inulin extract, it is advisable to increase the mass transfer surface, which can be achieved by spraying the initial product, and using volumetric energy supply methods, in particular, radiation energy supply. The important and most energy-intensive stages of drying are carried out in the hygroscopic area of equilibrium humidity of the object of the research, which determines the intensity and mechanism of the dehumidification operation in order to increase the degree of perfection, select rational operating parameters, adapt to the object of the analysis and solve a mathematical model of removal moisture from it. Based on the sorption isotherms and hygroscopic parameters of the inulin extract obtained in preliminary studies, obtained by dehydrating the inulin extract from Jerusalem artichoke (variety «Skorospelka», grown by JSC «Chaganskoe», the bAstrakhan region), a thermodynamic analysis of the process of sorption and desorption was carried out in different ranges of humidity variation. The total binding energy of moisture with the dry residue of inulin and its thermodynamic components were found. The data obtained do not contradict known literature sources and can be recommended when designing processes for removing moisture from inulin extract and designing drying devices.

Mechanical properties of wall soils for predicting damage to the substrate of Hiten wall paintings in the Horyu‐ji Temple main hall caused by humidity fluctuation: Measurements with mock‐up materials

AbstractSafe and efficient conservation of cultural artifacts requires preventing artifacts deterioration and energy‐saving environmental control. To achieve this, predicting deterioration caused by environmental conditions is necessary. Predicting the mechanical damage caused by humidity fluctuations necessitates knowledge of the mechanical properties of cultural artifacts materials. Although the mechanical properties of several artifacts have been extensively studied, no investigations have focused on the soils underlying wall paintings. This study aims to clarify some mechanical properties of the upper‐ and middle‐coat soils serving as the substrates for Hiten wall paintings at Horyu‐ji Temple. Mock‐up materials were prepared, and splitting tensile and uniaxial compressive tests were performed. Simultaneously, specimens with various equilibrium humidities were tested to clarify their humidity dependency. The tensile and compressive strengths, Young's modulus, proportional limit, and Poisson's ratio of the upper‐coat soil were 0.103–0.239 MPa, 1.16–2.55 MPa, 0.115–0.209 GPa, and 1.10–2.49 MPa, and 0.152, respectively. Moreover, the humidity‐induced strains for the upper‐ and middle‐coat soils were measured, and the moisture expansion coefficients were approximately 1240 and 2337 μST/−, respectively. The results of this study provide vital data for the conservation of the wall paintings and contribute to a deeper understanding of wall soil properties.

Mechanical properties of white clay used as wall painting substrate material: measurement of strength and modulus of elasticity of simulated substrate material of wall paintings Hiten at Kondo, the main hall at Horyu-ji Temple

Preserving cultural artifacts while minimizing the energy consumption and costs associated with environmental control is crucial. This often requires predicting artifacts degradation caused by temperature and humidity. Here, mechanical damage can be predicted by comparing stress and damage criteria. Although the constitutive coefficients and damage criteria of various materials have been extensively studied, the mechanical properties of white clay remain unknown. This material is a crucial component of various artifacts including some important cultural artifacts and national treasures of Japan. Thus, this study aims to identify the strength and elastic properties of simulated white clay mimicking the substrate of the wall paintings Hiten at Kondo, the main hall at Horyu-ji Temple. Following existing literature, we created the simulated white clay by combining clay, paper fiber, and rice glue. We fabricated 36 distinct specimen patterns by varying the equilibrium humidity and material mixing ratios. We measured the tensile strength using splitting tensile tests and, compressive strength, Young's modulus, and Poisson’s ratio using compressive tests. The tensile strength, compressive strength, Young’s modulus, and Poisson’s ratio ranged from 0.0785–1.17(MPa), 0.358–3.67(MPa), 0.0394–0.274 (GPa), and 0.10–0.44(-), respectively, with variations depending on the equilibrium humidity and ratio of material mixing. We also formulated the results as functions that depend on the equilibrium humidity and material mixing ratios. These findings can be used to predict stress and damage to targeted wall paintings and to inform the preservation and restoration of cultural artifacts containing white clay.Graphical

STUDY OF THE PROPERTIES OF RAPESEED AS A DRYING OBJECT

The study of the properties of rapeseed as an object of drying involves knowledge of physico-mechanical, hygroscopic, chemical and thermophysical, characteristics. The physico-mechanical properties of seeds include: size and shape, aerodynamic properties, surface condition, specific gravity, porosity and flowability of the grain mass, packing density of the grain mass, bulk and absolute weight, color, hydraulic resistance. The chemical and mineral composition of rapeseed was analyzed, it is rich in oil content (40-45%), proteins (25-26%), and also rich in potassium (979 mg) and phosphorus (840 mg).Hygroscopic characteristics include studies of the equilibrium humidity of rapeseed under the influence of relative humidity and air temperature. The need to dry rape to 8% reduces biochemical processes in the middle of the material, which improves the quality and does not spoil the seeds. Thermophysical characteristics increase with an increase in the temperature of the coolant and the moisture content of rapeseed. Formulas for calculating the specific heat capacity and thermal conductivity coefficient of rapeseed from the humidity of the material and the temperature of the heat carrier are given. To determine the qualitative characteristics of rapeseed, a method of determining biochemical parameters is presented. Determining biochemical indicators such as germination and germination energy of rapeseed before and after drying allows finding rational regimes. Determined factors of intensification during drying of rapeseed are as follows: increase in driving force, increase in kinetic coefficients, increase in the contact surface of the grain with the coolant. An increase in driving force due to an increase in the difference in moisture content and temperature of the coolant and grain. An increase in the kinetic coefficients is achieved due to an increase in the coefficients of heat transfer, thermal conductivity and drying. An increase in the contact surface of the grain with the coolant is possible due to the activation of the surface and the creation of a loose, pseudo-liquefied or suspended grain layer.

An experimental and theoretical analysis of the dynamic response of solar drying in natural convection under rainy month of Maroua (Cameroon) of three tropical wood species

ABSTRACT This work aims to study and characterize the drying kinetics, the heat mass transfer coefficients, the densities, the thermal effusivities, the thermal diffusivities and Young’s modulus of three tropical kinds of wood: ayous (triplochiton scleroxylon), sapelli (Entandrophragma cylindricum) and iroko (Milicia excelsa). A comparison has been doing between drying using a low expensive solar dryer in natural convection and drying using open-air conditions. The novelty of this work is to use an experimental study during the rainiest period in the city of Maroua, one city in Cameroon with a hard climate. Densities are influenced by the origin of the samples in the plank and increase linearly with the moisture content. At 30&per; of humidity (d.b), average densities of sapelli, iroko, and ayous were equal to 1000, 760 and 600 kg/m3 respectively. Thermal effusivities and thermal diffusivities increase linearly with the moisture content. Thermal diffusivities of the three kinds of wood are very near (2 × 10−7 m2/s at 30&per; of humidity (d.b)) and thermal effusivities increase with the wood densities with values located from 560 to 620 J/(K.m2.s0.5) at 30&per; of humidity (d.b). The heat mass transfer coefficients are influenced by the night and day and vary from 1.5 × 10−8–1.8 × 10−7 m/s for the global mass transfer coefficients, and from 1.8–6.5 W/(m2K) for the heat transfer coefficients. According to the variations of the values of young’s modulus and the drying kinetics, drying in open-air conditions is more rapid and not recommended than one in the solar dryer. The equilibrium humidity of all samples is near 10&per; (d.b).

Water sorption isotherms on lyophilized jabuticaba (Myrciaria cauliflora) peel: potential byproduct for the production of dehydrated foods.

In this work, water sorption profiles on lyophilized jabuticaba peel were evaluated using the BET, GAB, Halsey, Henderson, Oswin and Smith isotherm models. All water sorption studies were conducted using the static gravimetric method and saturated CH3COOK, K2CO3, NaBr, SnCl2, KCl and BaCl2 solutions at 20, 30 and 35°C. The best water sorption isotherm fits were determined with the GAB model at 20°C, Oswin model at 30°C and Halsey model at 35°C. The curve profiles of the isotherm models employed were classified as type III. The results revealed that lyophilized jabuticaba peel can be safely stored at 20, 30 or 35°C with the monitoring and control of relative humidity, equilibrium humidity and water activity. However, microbial action and undesirable enzymatic reactions may occur at 35°C when the relative humidity is above 22%. The present results are useful for defining suitable storage and production conditions of a novel jabuticaba peel-based process for the production of dehydrated foods.

Comprehensive operational parameter analysis of cross-flow hollow fiber membrane humidifier for humidification dehumidification desalination

Experimental results show that the cross-flow hollow fiber membrane contactor is the controlling component of the humidification dehumidification desalination system performance. Three sets of main operating conditions sensitivity analyses are performed numerically, including solution conditions (temperature, salinity, flow rate), air conditions (temperature, relative humidity, flow rate) and dimensionless parameters (number of heat transfer units, flow rate ratio of solution to air). Increasing flow rate ratio can effectively promote freshwater production rate before flow rate ratio reaches a critical value of 6.0. It is useful to improve moisture effectiveness by increasing number of heat transfer units. Solution inlet temperature has an exponential promoting effect on membrane flux, which is consistent with the exponential upward trend of the solution phase equilibrium humidity. Membrane flux increases dramatically at first and then slowly after solution flow rate exceeds 228 kg/h and air flow rate exceeds 57 kg/h. Ambient air with high temperature and relative humidity as well as the high salinity of the solution will slightly degrade the membrane flux.

A novel analysis of LiCl solution regeneration experiments

For the desiccant dehumidification, the regeneration process is a critical part. The paper experimentally investigated LiCl solution regeneration performance by analyzing the mass transfer characteristics. The regeneration rate, the regeneration potential and the concentration driving force were analyzed by considering the influence of independent variables such as the desiccant temperature, flowrate, and concentration. The regeneration potential, representing the underutilized mass transfer capacity stored in the outlet air, is determined by the smaller of the equilibrium value and the saturation humidity. The experimental results show the increase in solution temperature causes an increase in regeneration rate, accordingly also causes the regeneration potential and the residual driving forces to increase. It means that more regeneration potential is underutilized or ineffective capability exists. The increase in solution flowrate has no effect on the equilibrium curve. If the equilibrium humidity is less than the saturated humidity, the regeneration potential decreases with the increasing flowrate. Otherwise, it is necessary to consider special data to determine the variation trend. The increase in solution concentration causes a consistent decrease in regeneration rate, the regeneration potential and the residual driving forces.

Moisture sorption isotherms and thermodynamic properties of cowpea (Vigna unguiculate L. Walp) stored in a chamber under controlled humidity and temperature

AbstractThe sorption process of cowpea stored in a chamber the relative humidity of which is controlled by an atomizing humidifier was studied in 25, 35, and 45°C over 0.1%–0.9% water activities. A type III (J‐shapes) behavior was observed for the sorption isotherms of cowpea. The temperature increase caused a decrease in the equilibrium moisture content (EMC). Hysteresis effect existed over the entire water activity range. The experimental sorption data were fitted to many well‐known isotherm equations (GAB, BET, Henderson, Oswin, Peleg, Smith, Caurie, Halsey, Ferro‐Fontan, Kuhn, Chung‐Pfost, White‐Eiring). Among models evaluated, the Peleg equation was selected as the model giving the best fit quality for predicting the sorption behavior of cowpea. The sorption isotherms data were used to estimate the thermodynamic functions (sorption isoteric heat and entropy, Gibbs free energy, net integral enthalpy and entropy) providing an understanding energy requirement. The sorption isosteric heat calculated using the Clausius‐Clapeyron equation and the net integral enthalpy decreased swiftly with increasing moisture content while an increase was observed in the net integral entropy. Thermodynamic approach showed that the sorption process for cowpea was the enthalpy‐controlled and nonspontaneous.Practical ApplicationsSince the determination of the physicochemical relationship between water and food is very important for the continuity of food quality stability, many researches are carried out on this subject. The quality stability of foods is expressed in moisture sorption isotherms, which are the relationship between EMC and water activity at any temperature. Generally, data on equilibrium humidity were obtained using saturated salt solutions. No study was found on the moisture sorption isotherm data of cowpea stored in a chamber whose relative humidity is controlled by an atomized humidification system. It is thought that the data obtained with this system will achieve more successful results in equipment and process design since it is closer to the actual storage conditions.

Discussions on the Properties of Emulsion Prepared by Using an Amphoteric Chitosan as an Emulsifier

A typical emulsion contains oil and water phases, and these two phases can be combined by an emulsifier with both lipophilic and hydrophilic groups to form a mixture. If the component of water is more than oil, the mixture is termed as o/w emulsion. The water is called the continuous phase and the oil is called the dispersed phase. Oppositely, if the component of oil is more than water, the mixture is termed as w/o emulsion. The oil is called the continuous phase and the water is called the dispersed phase. Chitosan, which is biocompatible and non-toxic, was modified as an amphoteric emulsifier to replace sodium acrylates copolymer in the preparation of emulsions. Both sodium acrylates copolymer and the modified chitosan were used as emulsifiers, respectively, and the properties of moisturizing, transmittance, the number of bacteria, and emulsion stability were measured. The experimental results showed that the amount of amphoteric chitosan is less than that of sodium acrylate copolymer by 20% under a similar degree of emulsification. The measurement of spatial moisture showed the difference in equilibrium humidity was in the range of 2.05 to 2.20 gH2O/kg dry air, indicating that the moisture retention of the modified chitosan is better. In addition, the calculation of bacterial growth confirmed that the number of bacteria in the amphoteric chitosan emulsion and the sodium acrylate copolymer emulsion were 80 and 560, respectively. The emulsion stability was tested by the separation of oil and water phases in the diluted emulsion and by centrifugal accelerated sedimentation. The results showed that, for both emulsifiers, no separation of the oil and water phases occurred within one hour, and the stability of the modified chitosan emulsion was better. Therefore, the modified chitosan successfully substitutes sodium acrylates copolymer as an emulsifier in the preparation of emulsion.

Water content in Annona squamosa seeds under different temperature and relative humidity conditions of storage environment

The conditions of the storage environment, mainly related to temperature and relative humidity, influence the interaction of seeds with the environment and, consequently, the water content of the product. The study aimed to analyze the influence of ambient temperature and relative humidity on the water content of Annona squamosa seeds. The experiment was carried out in a completely randomized design with a 5x7 factorial scheme, with five temperatures (15, 20 and 25, 35, 40ºC) and seven conditions of relative humidity with nine replications. The equilibrium moisture content of the seeds was analyzed by mass difference. Data were subjected to analysis of variance by the F test and regression analysis. For significant interaction between the sources of variation, multivariate analysis was performed. Through regression analysis, linear models were obtained for the analyzed temperatures. Through multivariate analysis, a mathematical model was obtained to predict the equilibrium humidity of the pinecone considering temperature and relative humidity. The moisture in A. squamosa seeds is influenced by the temperature and relative humidity of the environment. Obtaining a mathematical model by multivariate analysis allows an adequate prediction of equilibrium moisture.

Thermal Properties of Lightweight Steel Concrete Wall Panels under Different Humidity Conditions.

The paper presents the thermal properties of lightweight steel concrete wall panels under different humidity conditions: under normal operation conditions and high moisture of the structure. The total thermal resistance (considering thermal inhomogeneity) of the enclosing lightweight steel concrete structure with a thickness of 310 mm using monolithic low-density foam concrete (density grade of D200), at an equilibrium humidity of 5% and 8%, was experimentally established. It was equal to 4.602 m2.0C/W and 4.1 m2.0C/W, respectively. In the dry state, the total thermal resistance of this structure was 5.59 m2.0 C/W, which corresponds to a thermal conductivity coefficient of 0.057 m °C/W. The influence of both horizontal and vertical joints of lightweight steel concrete wall panels and the absence of thermoprofiles on thermal properties was insignificant when using heat-insulating gaskets. The actual total thermal resistance of the structure was 2.5–2.8 times higher than that obtained by calculation under high-humidity conditions (29–32%). At the same time, the decrease in the value compared to the same value at an equilibrium humidity of 5% was only 4–6%. This indicates the good workability even of a structure with high-humidity foam concrete if the reduced total thermal resistance is complied with by the standardized one.

Uso de la liofilización y la convección como métodos de secado del subproducto del xoconostle y el efecto sobre sus propiedades antioxidantes

In this study, the influence of the drying method (lyophilization and convection) on the techno-functional and antioxidant properties of the by-product of xoconostle cv. Cuaresmeño (Opuntia matudae) was evaluated. During convection drying, the effect of the temperature (60, 70 and 80 °C) was evaluated, resulting in drying times of 195, 165 and 120 minutes, respectively. The influence of the temperature on the equilibrium humidity was determined through the drying kinetics, which were affected by increasing the temperature from 60 to 80°C. The drying time for the by-product decreased, and equilibrium humidities of 0.04, 0.03 and 0.02 g water/g dry sample were reached for 60, 70 and 80 °C, respectively. Fick's second law was used along the experiments to determine the effective diffusivity, which ranged from 4.788 E-10–8.109 E-10 m2/s for the evaluated temperatures. Convective drying at 60°C proved to be a suitable alternative for the conservation of antioxidant capacity (88.07 ± 0.38% 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition) compared to drying at 70 and 80°C. These were 8% higher compared to the results for freeze drying. However, convective drying at 60°C is more convenient for the xoconostle by-products due to the cost-benefit ratio.

Mathematical modeling of heat and mass transfer in the process of drying seeds of agricultural crops in vacuum conditions

Purpose. To analyze the effect of vacuum on the process of drying seeds of agricultural crops using mathematical modeling. Methods. Methods of differential calculus were used, in particular first-order differential equations, as well as differential geometry. The analysis of the mathematical model was carried out using graphs that were built by computer programs for solving differential equations. Results. On the basis of balance equations of heat and humidity flows of the seed drying process in the drying chamber, a system of differential equations was compiled and solved. Analytical dependencies describing the kinetics of drying and heating crop seeds when using vacuum in the drying chamber are obtained. On the example of soybean seeds, graphic dependencies of the kinetics of drying and heating at different pressures and the initial absolute humidity of the air in the drying chamber are constructed. These graphic dependences show that an increase in the vacuum in the drying chamber leads to an increase in the rate of seed drying, and a decrease in the initial absolute air humidity also increases the drying rate and decreases the equilibrium humidity. Analysis of the graphical dependencies of seed heating kinetics shows that drying in a vacuum reduces some of the thermal energy used directly to heat the seeds and reduces their heating temperature. Conclusions. To describe the process of heat and mass transfer in the process of drying seeds of agricultural crops under vacuum conditions, a mathematical model has been developed using a system of differential equations. The solution of which, on the example of soybean seeds, shows that when using a vacuum in the process of drying seeds, the exposure time and the proportion of thermal energy used directly to heat the seeds are reduced. Reducing the initial absolute humidity of the air inside the drying chamber also reduces the exposure time and equilibrium humidity. Therefore, drying in a vacuum reduces the negative impact of the heater on the seeds. Keywords: seeds, seed moisture, seed temperature, vacuum, absolute humidity, drying kinetics, drying chamber, equilibrium humidity.

Equilibrium Humidity as One of Important Energy-Efficiency Indexes in Drying of Food Powder Materials of Biological Nature

Considering general trend of energy consumption, according to which the amount of consumed energy increases, its cost and scarcity continuously increase. The 10–12 % of all energy is spent on drying processes in the world. At the current stage of the development of dehydration processes in Ukraine and the world, an urgent problem has arisen in the creation and development of highly efficient thermal technologies that would ensure minimal energy consumption for the process and high quality of the material. When drying powdered food materials of a biological nature, equilibrium humidity is important, which allows you to determine the final moisture content. Energy costs for the dehydration process, term, storage conditions and quality characteristics of the product depend on this indicator. The tensometric (static) method of Van Bamelen was used to determine the equilibrium humidity of the studied samples depending on the relative humidity of the air. The article presents the results of research – the kinetic curves of water vapour adsorption of antioxidant functional powders and instant cooking products (dry borscht) based on them were obtained and the comparative characteristics of the studied samples were carried out.

Ways of disposal of objective fuel sediments for fuel

Accumulated sludge from sewage treatment plants in large cities is obsolete, due to which they have lost the vast majority of nutrients, become too mineralized and practically unsuitable for direct use as fertilizer.The research is devoted to the development of a unified approach to the efficient processing of sludge as a fuel with the addition of flammable fillers such as milling peat, buckwheat husk, wood waste (sawdust).Identified factors influencing the energy efficiency of the processes of preparation of raw materials, drying and granulation of composite mixtures based on peat, obsolete sludge and biomass, which allowed to obtain quality pellets and briquettes.The problem of processing obsolete sludge is the low content of organic matter, excessive ash content and high humidity, so they are not suitable for incineration in its pure form and for agriculture. To reduce ash content, it is advisable to add biomass and peat to sludge and dry to reduce moisture.The article presents studies of drying kinetics of composite granules based on peat, obsolete sludge and biomass on an experimental convective drying stand. The convective drying stand allows to carry out heat treatment of composite granules at a temperature of drying agent of 30–150°C and speed of movement of 0,5–5 m/s. A comparison of the drying time of the sludge-peat composition and its components is performed, which shows that during the drying of the composite granules the intensification of the drying process is observed.The presented comparison of drying kinetics of two- and three-component granules shows the same nature of the drying curves and the drying time is in the range of 17–18 minutes. The optimal ratio of components for quality granulation is selected. Effective drying regimes of composite granules based on sludge, peat and biomass are determined. Equilibrium humidity of composite granules not exceeding standard fuel humidity is determined.

ADSORPTION OF OBSOLETE SLUDGE, PEAT, BUCKWHEAT HUSKS AND COMPOSITIONS FROM THEM

The problem of accumulation of obsolete silt deposits at aeration stations is relevant for the whole territory of Ukraine. This can lead to environmental hazards. Therefore, the task of processing silt deposits with the creation of granules based on them with the addition of peat and buckwheat husks.
 Van Bamelen's tensometric (static) method was used to determine the equilibrium humidity of the experimental samples depending on the relative humidity .
 As a result of researches kinetic curves of adsorption over obsolete silt deposits, peat, buckwheat husk and the three-component composition created on their basis are received. Kinetic adsorption curves indicate a slow process. The adsorption curves of the three-component composition have the character of curves of obsolete sludge, which have a non-uniform character. The obtained equilibrium humidity does not exceed the standard humidity for fuel pellets. The adsorption isotrams of the three-component composition and its components are determined, from which the equations of experimental and linearized isotrams are obtained. The analysis of experimental isotherms allows to relate them relatively to the isotherms of adsorption IV, which are observed in inorganic oxides and in other porous bodies.
 For the first time, the adsorption properties of three-component compositions based on peat, sludge and buckwheat husk were studied. The obtained equilibrium humidity of the compositions does not exceed the standard humidity for fuel pellets (is 20%) and is 6 - 7%. Therefore, they can be used for combustion in biomass boilers. The resulting ash can be used for the production of bricks, cement and other building materials. During storage of composite granules in order to prevent loss of their technological properties, it is recommended to maintain humidity at the level of 60 - 70%.

Moisture adsorption isotherms of baru almond flours

The whole meal (WBF) and partially defatted Baru almond (PDBF) flour have commercial and nutritional attractions. The study of the adsorption behavior is essential for correct storage. Thus, the objective was to determine the moisture adsorption isotherms for WBF and PDBF, at temperatures of 20, 30, and 35 °C, in the range of water activity from 0.070 to 0.975. The static gravimetric method was used. Fourteen models were adjusted to the experimental hygroscopic equilibrium humidity data. The GAB model better represented the moisture adsorption isotherms for WBF, while the BET model represented the PDBF. The curves of the two flours were classified as type III. Safe storage for WBF occurs at equilibrium humidity of 6.41, 7.12, and 7.49% d.b., and for PDBF at 9.04, 9.26, and 9.41% d.b., at the respective temperatures of 25, 30, and 35 °C.

Evaluating the influence of humidity on asphalt mixture performance by the flow number test

Moisture damage greatly influences the performance of asphalt pavements. However, existing studies evaluating the moisture sensitivity of asphalt mixtures either ignore the influence of water vapor or use inappropriate testing methods. This study examined the moisture sensitivity of asphalt mixtures by using the flow number (FN) test. Four levels of the humidity condition (2%, 50%, 80% and 100% RH) were first designed to condition specimens, after which the FN test was employed to assess the moisture susceptibility of mixtures. The results show that it took 50 days for specimens to reach humidity equilibrium at Humidity Level 1, while approximately 4300 h (180 days) were required for specimens to achieve the respective Humidity Levels 2, 3, and 4. The evaluation indicators—in other words, FN, the onset of the secondary stage N4, their corresponding permanent strains (PS2 and PS3), and the slope of secondary stage S2—were then determined by applying a two-step secant method. It was observed that N4 and FN exhibit a gradually decreasing tendency, while PS2 and PS3 tend to increase with the rise in humidity level, but this phenomenon seems indiscernible in some groups. A newly modified exponential function model was proposed to characterize the interaction between humidity levels and S2. It was also demonstrated that the slope of the secondary stage is positively correlated with humidity conditions, which indicates that more deformation will occur with a faster deformation rate during higher humidity levels. The combined use of FN and S2 is a recommended way to assess the trend of permanent deformation of asphalt mixtures under different humidity conditions.