Equilibrium Moisture Levels Research Articles

Diagnostics and Multi-criteria Analysis of Methods for Drying Buildings After Flooding. Case Study

This article presents guidelines for moisture and mycological diagnosis procedures for buildings after flooding. This paper proposes a division of the diagnostic procedure according to the medium of action and collects and presents methods for drying building elements. 54 companies dealing with drying were analyzed. The task of dehumidification is to use various methods to reduce the moisture level of building partitions to the equilibrium moisture level. An analysis of dehumidification methods in terms of ease of application, duration of the dehumidification process and level of structural interference is presented. In Poland, there are no guidelines formulated in legal acts or instructions regarding the procedure for moisture diagnostics and nor drying. It was noted that in situ studies cannot always lead to determining the actual values of mass moisture and thus to creating a real model of partition drying.

Evaluation of an improved indirect solar dryer for Curcuma Amada without and with stone chips as thermal energy storage: An investigation on kinetics, energy, exergy, quality and economic aspects

The drying kinetics, energy, exergy, quality, and economic studies of a solar dryer with and without energy storage have been conducted. The original configuration of a solar air collector (SAC) has been modified by adding waste stone chips beneath the absorber plate. Data related to mass loss, solar radiation, and temperatures were gathered during the experiments in both the configurations. Curcuma Amada samples had initial moisture of 87.4 % and achieved an equilibrium moisture level of 4.4 % within 8 h in the dryer equipped with waste beverage canned absorber plate and storage (SDCWS) and for dryer without storage (SDCWOS) it took 26 h. Out of the eleven drying models tested, the Midilli and Kucuk model exhibited the most favorable fit for Curcuma Amada in both the experiments. The average efficiencies for the collector and dryer were 67.26 % and 21.88 %, respectively, in SDCWOS. In contrast, the efficiencies for the collector and dryer were 87.95 % and 29.63 %, respectively, in the SDCWS. Exergy parameters such as in, out, loss, efficiency, improvement potential, waste exergy ratio, and sustainability index were estimated for both the configurations. Quality analysis was further carried out for both SDCWOS and SDCWS in terms of total polyphenol content, total flavonoid content and color. The estimated energy payback periods were 1.7 years for SDCWOS and 0.47 year for SDCWS, considering a 20-year lifespan. In all assessed aspects, the SDCWS configuration showed more favorable outcomes. The results of this study have the potential to positively impact the sustainable advancement of agricultural drying techniques within rural areas.

Influence of hot water blanching and saline immersion period on the thermal effusivity and the drying kinetics of hybrid solar drying of sweet potato chips

The purpose of this study was to investigate the effect of adding pre-treatment to solar dried sweet potato chips. The tested pre-treatments were blanching using hot water and saline immersion. Indeed, the potato chips were dried using a convective indirect solar dryer, equipped with a wind generator and glycerine as thermal storage. The system was built locally at the University of Agriculture in Umuahia, Abia State, Nigeria. The obtained experimental drying curves and kinetics were directly affected by the weather conditions, as the drying rate increased with the increase of the radiation and the ambient temperature and decreased with their decrease. Drying of the various pre-treated potato slices took 8–14 h to attain equilibrium moisture level under the variable external drying conditions. The drying curves were fitted to semi-empirical models. The results showed that the two-term exponential model was the best model that fitted the experimental data. Shrinkage was a vital phenomenon observed during the drying process, as the volume of the chips was reduced by 50%. The volume of samples treated by saline immersion was higher by 6% than non-treated samples. Shrinkage phenomenon was then introduced to determine the thermos-physical properties of sweet potato chips, with particular attention to the particle density, the bulk density, shape analysis, specific heat capacity, thermal diffusivity, and thermal effusivity. The particle and bulk density peaked at 1.41–1.44 g/cm3, and 1.52–1.53 g/cm3 respectively for all treatments. The thermal effusivity ranged from 17.6 to 7.93 W.S1/2.m−2.K−1 while the specific heat capacity ranged from 1028 to 2288 J/kg °C. All the thermo-physical properties were presented as a function of the volume or moisture content variation with a high degree of association. The results demonstrated the importance of shrinkage and its direct effect on the determination of the thermos-physical properties of the studied product for both pre-treated and untreated samples.

Considerations on the Drying of the Raw Material and Consequences on the Quality of the Injected Products

The first part of the paper presents the specific issues from the injection molding associated with the water content of the hygroscopic plastics (water adsorption, equilibrium moisture level, chemical affinity, hydrolysis) and recommendations regarding the drying of plastics for injection, the drying methods and defects specific to products injected due to the moisture content. The experimental results on the injection of a polyamide (AKULON) and of a thermoplastic polyurethane (DESMOPAN) presented in the second part of the paper are focused on the surface appearance fault splay associated with the different values of moisture content for these two materials, verify the value for the admitted moisture content for two hygroscopic materials, polyamide and thermoplastic polyurethane, and ends with conclusions on the residual humidity allowed and opinions on choosing the drying technology and parameters.

Design and Optimization of Domestic Solar Dryer

This paper presents the design, simulation and optimization of a mixed-mode solar dryer based on the climatic data of location Kigali and mangoes were used as a reference product. The model was simulated using TRNSYS software for thermal analysis and the results was shown on a graph which presents the useful temperature gain for drying. The results were used for solar drying simulation to evaluate its performance in terms of drying rate, here MATLAB was utilized for this. It is clear on the graph how the moisture content of mangoes decreases with time up to 10%, which is their equilibrium moisture level for safe storage. The optimization of the model was further done with the modification of the solar dryer by making the front wall of the drying chamber with a glass which adds a greenhouse effect, hence a further increase in drying temperature. The solar drying simulation was again carried out and a clear difference in drying time was observed in the drying rate graph where the time of moisture content removal was reduced from 24 hours to 10 hours.

Impact of particle size of solid desiccant mould on moisture absorption and regeneration time

This work presents the impact of particle size of desiccant material on moisture absorption and regeneration time. To study the absorption and regeneration time, a solid desiccant mould which consists of 60% of bentonite, 10% of calcium chloride, 20% of vermiculite, and 10% of cement with varying vermiculite particle size is selected. Four different types of mould are prepared by varying the vermiculite particle size and tested experimentally in the desiccant drying chamber under uniform conditions. The result shows that the moisture absorption capacity of the mould is increased by 33% for the vermiculite particle size of 5 mm and above than the vermiculite particle size without varying. Uniform air flow in the drying chamber is also verified by using Computational Fluid Dynamics analysis. The mould attains equilibrium moisture level after 6 h and it has to be regenerated for effective moisture absorption.

THE EFFECTS OF GLUCOSE SYRUP AND GLYCEROL ON SOME PHYSICAL PROPERTIES OF DRIED FIGS

The effects of glucose syrup and glycerol (40%, w/w) on moisture sorption isotherms, textural hardness, sugar crystallization and color of dried figs equilibrated at different water activities at 25C were studied. The additives caused significant increases in the equilibrium moisture level in fig samples. The Guggenheim-Anderson-deBoen equation was able to fit the experimental data and gave the lowest monolayer moisture level for the control without additives while this value for fig–glycerol mixture was greater than fig–glucose syrup. In the presence of glucose syrup or glycerol, the texture of fig was softer than the corresponding control and glycerol was more effective than glucose syrup. Sugar crystallization in figs decreased in the presence of glucose syrup/glycerol and its maximum level occurred at low water activities while this value for control sample was observed at intermediate water activity region. The color of fig–glycerol sample was darker than the control and fig–glucose syrup sample. PRACTICAL APPLICATIONS Plasticizers that bind water in food systems and lower the water activity of food materials have good potential in acting as texture modifiers in fruits with hard texture like dried figs. They can also reduce sugar crystallization, which is one of the most important factors determining consumer acceptability of dried and semidried fruits with high amount of sugars. This work evaluates the effects of glucose syrup and glycerol (at 40%, w/w) on moisture sorption isotherms, textural hardness, sugar crystallization and color of dried figs equilibrated at different water humidities. With these results, glucose syrup/glycerol may be introduced as new additives having good potential to be used as hygroscopic ingredients in figs to have more water with greater microbial stability.

Moisture Distribution Profiles in RT-Cured Glass/Epoxy Laminates of Different Thicknesses

Investigations were carried out on the moisture absorption behavior of RT-cured glass/epoxy composite specimens subjected to 333 K/Immersion in distilled water. Different laminate thicknesses (i.e., 0.25-2.25 mm) were studied for comparative evaluation of their moisture diffusion and distribution profiles across the thickness of the composite as a function of the exposure period. Moisture absorption data showed that the equilibrium moisture levels (Mm) remained practically the same for different laminates of the same fiber weight fraction (i.e., 0.62). Further, the times of saturation (tm) increased with the laminate thickness, while the absorption rates (slopes of the absorption curves) showed a reverse trend. It was also found that the Diffusion Coefficient (Dc) values of different thicknesses specimens ranged between 0.28 and 7.81(10 7)mm2/sec, indicating a negligible thickness effect on this diffusion parameter. The small variations of Dc (all of the order 10 7 mm2/sec) are attributed mainly to the variations in the edge areas for different thickness laminates.

Characterization of hydrothermally dried low-rank coals

Over a period of eight years (1989 through 1997) the Mineral Industry Research Laboratory (MIRL) at the University of Alaska, Fairbanks, AK, has investigated the effects of temperature, residence time and particle size on the degree of low-rank coal (LRC) upgrading for a nonevaporative, hydrothermal drying process, also known as hot water drying (HWD). The following three Alaskan LRC s were used in this study: Usibelli coal (Seam No. 4) from the Nenana Coal Field, Little Tonzona coal from near McGrath, and Beluga coal from the Beluga-Yentna field on the west side of Cook Inlet. Replicated factorial tests were conducted. Experimental results indicate that most of the low-rank coal upgrading via HWD occurs rapidly within the first 10 to 20 min of residence time. Thereafter, the upgrading process slows down, and more than 100 min of additional residence time is required to produce percentage increases equivalent to what was achieved in the first 10 to 20 min. The properties of the hot water dried products were very sensitive to process temperature. Calorific value, carbon and oxygen contents, equilibrium moisture levels and Hardgrove gindabilities all appear to change linearly with temperature within the 275 °C to 325°C (525°F to 615°F) range.

Fluid electrification measurements of transformer pressboard/oil insulation in a Couette charger

A Couette charger (CC) facility has been built to simulate flow electrification processes in transformers where transformer oil fills the annulus between coaxial cylindrical electrodes. Transient measurements with a step change in temperature have shown the charge density to change from an initial value to a new steady-state value, including cases of polarity reversal, both values dependent on the equilibrium moisture levels in oil and pressboard. Through a model that accounts for diffusion of charge from the paper-oil interface into the bulk of the oil, these measurements are used to deduce the equilibrium wall charge density. To help understand the effects of energization and to scale laboratory measurements at low voltages and low frequencies to operating transformers, a charge injection model was refined to examine the migration of double layer and injected charge in the imposed sinusoidally time-varying electric field. Good fits between this model and measurements are achieved. >

Moisture absorption in graphite/epoxy laminates

This work investigates the uptake of moisture by XAS-914C and AS4/3501-6 graphite/epoxy composite laminates under a range of temperature and humidity conditions. From the experiments, the diffusion coefficients of moisture in a number of laminates have been determined, together with the equilibrium moisture levels in the matrix. The effects of thermal spiking (thermal transients simulating supersonic heating of military aircraft) on moisture uptake were determined experimentally using a number of combinations of spiking and moisturising conditions. Thermal spiking was found to be damaging when moisture was present in the laminate, and spiking during moisturising was found to be more severe than thermal spiking of material conditioned to equilibrium moisture levels. The pronounced effects of repeated thermal spiking on moisture uptake suggest a progressive form of spiking damage, and a simple model is proposed of a damage zone progressing through the laminate during successive moisturising then spiking cycles.

Fire in the Venezuelan Amazon 2: Environmental Conditions Necessary for Forest Fires in the Evergreen Rainforest of Venezuela

We studied the potential for forest fires in seven vegetation types near San Carlos de Rio Negro, Venezuela, one of the wetter regions of Amazonia. Three of the communities were tall, closed-canopy forests; two communities had closed canopies but were short in stature; and two communities had open canopies. Fine fuels reached dynamic equilibrium moisture levels (i.e., no further net drying given prevailing microclimate) after only three to four rainless days in the two open-canopy and two short-stature communities and after eight to ten days in the three tall, closed-canopy forest types. Fine-fuel moisture content at 'equilibrium' was generally twice as high in the tall, closed-canopy forest as in the other four vegetation types (20% vs 10%). We successfully started surface fires in the two open-canopy and two short-stature communities after four to six days without rain. An average of 19-27% of the available fuels were consumed by these fires. We were unable to burn the three tall, closed-canopy forest communities, even after artificially excluding rain for 41 days. The elevated relative humidities characteristic of tall, closed-canopy forests do not permit fuels to dry to the combustion point. Under current climatic conditions, fire is only possible if the relative humidity drops to 65% or below. In some open-canopy and short-stature communities, relative humidity falls below this threshold about one day each week, on average, but in tall, closed-canopy forest such levels may occur less than one day each year.

Moisture content/relative humidity equilibrium of high-oil and confectionery type sunflower seed

Adsorption and desorption moisture equilibrium (m.c./e.r.h.) was determined for high-oil and confectionery type sunflower seeds. The seeds were exposed to various relative humidities which were controlled with environmental chambers. The equilibration data for both seed types were determined at 10 and 20°C. The two seed types yielded almost identical adsorption and desorption moisture curves at 10°C which indicated that seed physical and chemical properties had little effect on m.c./e.r.h. at this temperature. The “hysteresis effect” was evident at 10°C, desorption equilibrium moisture levels being higher than adsorption for both seed types. There was no apparent “hysteresis effect” in seed equilibrated at 20°C. At the higher temperature, the confectionery seed equilibrated to higher moisture levels than did the high-oil type, thus hull to kernel weight ratio, hull thickness, and oil content could affect m.c./e.r.h. at 20°C

Factors Affecting Moisture Absorption in Polymer Composites Part I: Influence of Internal Factors

The influence of internal factors like the fibre volume fraction and its orientation to the diffusion path on the moisture absorption trends of both the permeable (Jute-Epoxy) and the impermeable types (glass-epoxy) of composites were studied. The equilibrium moisture level (Mm) and the diffusion coefficient (DJ of the glass-epoxy composite decreased as expected, with an increase of the glass fibre fraction (V f) and its orientation («), while those of the Jute-epoxy composite (ie Mm and D/) were found to increase with an increase in the resin impregnated jute fibre fraction (V/) and remain practically uninfluenced by the variations in the fibre orientation angle. These observed trends were explained in terms of typical fibre permeabilities and the diffusion paths preferred by the moisture in these composites. A term called "dif- fusivity index (DI)" was introduced to quantify the relative permeabilities of polymer composites to moisture.

Moisture Detection in Composites Using Nuclear Reaction Analysis

An experimental method for evaluation of the localized moisture con tent in graphite epoxy composites or other organic solids is described. The method involves specimen conditioning in D2 O, followed by measurement of the localized deuterium concentration by means of the D ( 3 He, p)4 He nuclear reaction. Equilibrium moisture levels in two epoxy resins and two graphite epoxy composites measured by the nuclear technique are con sistent with those obtained from bulk gravimetric methods. Moisture pro files measured in a unidirectional graphite epoxy composite are compared to predictions from diffusion theory.

Equilibrium Moisture of Peanuts

Desorbing water to equilibrium moisture level of peanuts (Virginia type) of Chiba Prefecture was determined during storage at various relative humidity and temperature. When stored under the same relative humidity, the level of equilibrium moisture of green (small) kernels was higher than that of ripened (large) ones, and the moisture leves of kernels and shells reached to the equilibrium state of comparative low level at higher temperature.