Effects Of Moisture Migration Research Articles

Effects of Moisture Migration and Changes in Gluten Network Structure during Hot Air Drying on Quality Characteristics of Instant Dough Sheets.

The impact of hot air drying temperature on instant dough sheets' qualities was investigated based on water migration and gluten network structure changes. The results revealed that the drying process redistributed the hydrogen proton, with deeply bound water accounting for more than 90%. The T2 value decreased as the drying temperature increased, effectively restricting moisture mobility. Meanwhile, microstructural analysis indicated that instant dough sheets presented porous structures, which significantly reduced the rehydration time of instant dough sheets (p < 0.05). In addition, elevated drying temperatures contributed to the cross-linking of proteins, as evidenced by increased GMP and disulfide bond content (reaching a maximum at 80 °C), which improved the texture and cooking properties. Hence, the water mobility was effectively reduced by controlling the drying temperature. The temperature had a facilitating impact on promoting the aggregation of the gluten network structure, which improved the quality of the instant dough sheets.

Macro-micro damage model of the effect of freeze–thaw on jointed rocks considering compaction deformation

Jointed rock mass contains microscopic cracks, joints and other defects. Moisture migration during freeze–thaw cycles affects crack initiation and propagation of defects of different scales. The change of defects in turn affects the mechanical and deformation properties of jointed rock mass, especially in the compaction deformation stage. Considering the effects of freeze–thaw cycles on compaction deformation, plastic deformation, macroscopic damage and microscopic damage, a macro–micro damage constitutive model of jointed rock mass under freeze–thaw actions was proposed under the framework of thermodynamics. Based on the internal state variables (ISV) theory, the Helmholtz free energy of jointed rock mass under freeze–thaw actions was obtained by taking compaction deformation, macroscopic damage and microscopic damage as internal state variables. The compaction, elasticity, plasticity, and damage stages were analyzed respectively, and the macro–micro damage model of jointed rock considering compaction deformation were deduced by regarding the total strain as three parts (compaction deformation, elastic deformation and plastic deformation). The validity of the proposed model was verified by compression tests on rock samples with different induced crack inclination angles that have undergone different amounts of freeze–thaw cycles. The model considers the moisture migration mechanism of freeze–thaw damage and the friction and slip mechanism of microcrack surfaces. The effect of moisture migration on the compaction deformation during freeze–thaw cycles is significant, and the proposed model can accurately simulate the full stress–strain curves (compaction-elasticity-plasticity-damage) of jointed rock mass under freeze–thaw actions, which provides quantitative guidance for reducing freezing damage by attenuating moisture migration.

Effect of moisture migration on surface discharge on oil-pressboard of power transformers under cooling

In this paper, the PD properties of an ester oil/PB and a mineral oil/PB system undergoing a moisture transient are investigated using a needle-plane electrode under natural cooling. The temperature, moisture concentration and water activity of the oil are continuously monitored. Moreover, an improved moisture diffusion model is developed by using COMSOL Multiphysics to verify the experimental results. The measurement results show that there is a sharp reduction of partial discharge inception voltage (PDIV) or a sudden increase of PD intensity in the process of natural cooling for both ester oil and mineral oil system. However, the PDs extinguish gradually after the occurrence of the minimum of PDIV. For the cooling mode selected in this study, the minimum of PDIV for the ester oil system appears in the third hour after cooling begins, while it is about in the second hour for the mineral oil system. In addition, the simulation results are consistent with the experimental data.

Effect of moisture migration and water vapor pressure build-up with the heating rate on concrete spalling type

In this study, the effect of moisture migration and water vapor pressure build-up within high-strength concrete (HSC) on its spalling property is empirically investigated at various heating rates and compressive strengths with different water-binder ratios (W/B). An experiment is conducted on concrete specimens with various W/Bs by applying two different heating rates: fast and slow heating. It is confirmed that the moisture migration and water vapor pressure within the concrete differ, depending upon the W/B and heating rate. For HSC with W/B less than 0.33, surface spalling occurs due to the formation of moisture clogs on the surfaces of the concrete specimens, under the fast heating condition. For HSC with dense microstructures, although moisture clogs are not formed at specific positions within the concrete specimens, explosive spalling occurs due to boiling liquid expanding vapor explosion (BLEVE) in the concrete pores, under the slow heating condition.

Effect of moisture migration and phase change on effective thermal conductivity of porous building materials

In this paper, a new method for precise evaluation of the effective thermal conductivity (ETC) caused by moisture transfer inside porous building materials was proposed. Moreover, the mathematical models for coupled heat and moisture transfer without and with moisture phase change were established. Based on the interactions among the moisture phase change, temperature field, and moisture field inside the porous materials, a loop iteration calculation method was proposed to solve for the heat flux caused by moisture migration and phase change. By combining the heat flux with the classical evaporation and condensation theory, the additional thermal conductivities (ATCs) caused by the moisture migration and phase change were obtained. In order to obtain the quantitative relationships between the main factors and ATC caused by moisture transfer, different temperature and humidity boundary conditions were used to analyze the ATC. The results show that the ATC caused by moisture migration increases when the temperature difference decreases and the water vapor pressure difference between the indoor and outdoor air increases. The ATC is greatly influenced by outdoor air temperature fluctuations, while the influence of water vapor pressure fluctuations is relatively small. The value for the ATC caused by moisture phase change is mainly determined by the temperature gradient.

The Effect of Drying around Power Cables on the Vadose Zone Temperature

Core Ideas We show the impact of soil hydraulic properties on its critical temperature. Ambient conditions have a larger impact in some fields than local soil parameters. We introduce a parameter for optimizing cable backfill based on hydraulic properties. The effects of moisture migration away from power cables depend strongly in most soils on whether the soil has reached the so‐called critical conditions (e.g., critical temperature) for a dry‐out. However, research on how to estimate this critical temperature has been limited. We solved numerically a differential equation for the planar case of steady‐state coupled heat and mass transfer in porous media, using the van Genuchten–Mualem model for the hydraulic properties of the medium. The critical isotherm is assessed by the temperature at which the steepest change occurs in the moisture content with temperature. We considered the impact of the properties of the surrounding medium and of the ambient temperature and moisture content on the dry‐out temperature. We found that seasonal variations in ambient conditions in a field in Italy have a greater impact on the critical temperature than the variations in soil properties in that field (under the assumption of a nearly uniform moisture content with depth). However, our analysis shows that, under certain conditions, a change in the van Genuchten parameter n and in a specific combination of parameters that we call a dynamic parameter can have as large an effect on the critical temperature. This suggests a direction in the optimization of backfill materials.

Water Signatures and Their Thermal Stability in Bedded Salt for Nuclear Waste Storage: An Incoherent Inelastic Neutron Spectroscopy Study

The forms of water and their thermal stability in bedded salt are crucial in determining the material's suitability for heat-generating nuclear waste storage. Here we show first-of-its-kind incoherent inelastic neutron scattering (IINS) results of bedded salts to distinguish three water environments: intergranular water molecules confined to grain boundaries, water trapped as brine in fluid inclusions, and structural water in intracrystalline hydrous minerals. Sixteen spectral lines can be distinguished unambiguously in the 0-1100 cm(-1) multiphonon and librational domain, yielding an unprecedented high resolution for a natural material. The spectral response to temperature illustrates the bimodality of the technique enabling the intergranular water component to be distinguished from that of brine, shedding light on a nearly 30-year-old problem in characterizing different forms of water in rock salt. This pioneering study shows that IINS provides insight into the cause and effect of moisture migration and its coupling to thermomechanical properties in salt formations. Our results are pertinent to subsurface energy exploration and storage, including nuclear waste storage, in salts. (Less)

Effect of moisture migration on sandwich texture

The effect of moisture migration on the texture of tuna sandwiches was studied using panel and instrumental methods.Moisture migration from the spread to the bread was dependent on the percentage of water in the filling (r = 0.97).Moisture content affected the firmness and cohesiveness of the sandwiches, as measured by panel and instrumental methods. A correlation was found with firmness (r = 0.75) but not with cohesiveness.

Effects of Moisture Migration in Insulations under Hot and Humid Conditions

The effects of moisture gain by fibre glass insulation slabs were investigated experimentally by exposing one face of the slabs to a hot and humid ambient while maintaining the other face at a constant cold temperature. The temperature ranges considered for the hot and cold sides of the slabs were 36°C to 41°C and 8.5°C to 20.8°C, respectively. The slab thicknesses ranged from 62 to 76 mm. The variation of the heat flux at the cold surface, the temperature distribution, the total moisture gain and the liquid content distribution were measured over a period of up to 600 hours. One-dimensional transport models with liquid content dependent physical properties were used to interpret the experimental data. The heat flux at the cold face increased gradually with time while the temperature distribution across the slabs showed a maximum fluctuation of about 2°C. The rate of total moisture gain was nearly constant initially, but decreased gradually with time. The measured liquid content distribution across the slabs was highly nonuniform. The computational model predicted the heat flux and the temperature distribution well but overestimated the total moisture gain at longer times. The model predicted a more uniform liquid distribution than that measured experimentally.

Effect of moisture migration on temperature rise in underground cables

An empirical formula suitable for engineering applications is presented to clarify the expected final effective thermal resistivity of the soil due to the migration of the soil moisture around loaded underground cables. The formula depends on the type of heating, cable dimensions, and characteristics of the soil.

The ignition of wet and dry wood by radiation

The effect of varying the moisture content on both the pilot and spontaneous ignition times of specimens of different woods 7·6 and 15 cm square has been measured over a wide range of intensities of radiation. Moisture increases the energy required for ignition; it also increases the minimum intensity for ignition, though with pilot ignition its effect is only marked for moisture contents above 40 percent. Results have been correlated on the assumption that the material is inert and ignites at a fixed temperature. Simple heat transfer theory has been used to calculate this temperature, taking values for the thermal properties appropriate to the given moisture content and allowing within the term for thermal capacity the heat required to remove the water; the effects of moisture migration have been neglected, following the results of Williams (see ref. 1). For pilot ignition the correlating temperature was found to be 380°C, corresponding to a critical intensity of 0.31 cal cm−2s−1, except for fibre insulating board which appeared to ignite at the somewhat lower temperature of 330°C. Earlier experiments, with smaller specimens, gave a similar ressult 360°C, with the results for fibre insulating board included. The present correlation, however, extends to much longer times (up to 59 min). The results show that the choice of 0·3 cal cm−2s−1, as the maximum acceptable level of radiation for building regulation purposes, gives a larger margin of safety than was originally thought. For spontaneous ignition the correlating temperature was found to be 545°C, the same as found previously for smaller areas, corresponding to a critical intensity of 0·74 cal cm−2s−1. The present correlation extends to much longer times (up to 16 min) and the results suggest that the empirical correction necessary for the effect of area on ignition time is linked with density.