Water Concentration Gradient Research Articles

Hydrate Formation and Decomposition Regularities in Offshore Gas Reservoir Production Pipelines

In recent years, the exploitation and utilization of offshore oil and gas resources have attracted more attention. In offshore gas reservoir production, wellbore temperature and pressure change continuously when water-bearing natural gas flows upward. The wellbore temperature is also affected by the low-temperature sea water. The combination of temperatures and pressures controlled by the upward flow, and cooling from the surrounding seawater frequently leads to the conditions of temperature and pressure for hydrate formation. This can lead to pipeline blockage and other safety accidents. In this study, we utilize mathematical models of hydrate phase equilibrium, wellbore temperature, wellbore pressure to study hydrate formation and decomposition in offshore gas reservoir production. Numerical solution algorithms are developed and numerical solutions are validated. The sensitivity influence of different parameters on the regions and regularities of hydrate formation and decomposition in wellbores are obtained through numerical simulations. It is found that increased daily gas production, water content, or geothermal gradient in offshore gas reservoir production pipelines results in less hydrate formation in the wellbores. Accordingly, the risk of wellbore blockage decreases and production safety is maintained. Decreased tubing head pressure or seawater depth results in similar effects. The result of this study establishes a set of prediction methods for hydrate formation and decomposition that can be used in the development of guidelines for safe construction design.

Effect of soaking time on water absorption behavior of dehulled soybean dhal

The effect of soaking time on water absorption behavior of dehulled soybean dhal (variety-JS-335) was studied at the Department of Agricultural Process Engineering, CAET, Parbhani to see the variation of water content (gm), moisture content (%, d.b.) and water absorption(%). Samples of soybean dhal (20gm) were soaked in water in the ratio of 1:3(w/v) at 15 oC, 25 oC and 35 oC water temperatures up to saturation point. During this experiment the amount of absorbed water increased as soaking time and temperature increased. During soybean hydration, the water is absorbed to a maximum of 140.78% in 4 hours, 3 hours and 2 hours at 15 oC, 25 oC and 35 oC, respectively. Initial water uptake was high due to high water concentration gradient between the soaking medium and dry cotyledons of the seeds. However, the rate of water absorption steadily decreased as the soaking process continued.

Visualized tracing of capillary absorption process in cementitious material based on X ray computed tomography

Moisture is one of the major deterioration factors of concrete. In this study, the capillary absorption process, which is one of the major transportation mechanism in cement paste, is non-destructively investigated by using X-ray computed tomography (XCT). A novel image processing procedure is proposed to correct the XCT image artifacts and calibrate the results of different measurements. The proposed image processing procedure allows for 3D visualization of the absorption process and additional information can be obtained, including the height of the water absorption front and the water content gradient.

Environmental factors determining distribution and activity of anammox bacteria in minerotrophic fen soils.

In contrast to the pervasive occurrence of denitrification in soils, anammox (anaerobic ammonium oxidation) is a spatially restricted process that depends on specific ecological conditions. To identify the factors that constrain the distribution and activity of anammox bacteria in terrestrial environments, we investigated four different soil types along a catena with opposing ecological gradients of nitrogen and water content, from an amended pasture to an ombrotrophic bog. Anammox was detected by polymerase chain reaction (PCR) and quantitative PCR (qPCR) only in the nitrophilic wet meadow and the minerotrophic fen, in soil sections remaining water-saturated for most of the year and whose interstitial water contained inorganic nitrogen. Contrastingly, aerobic ammonia oxidizing microorganisms were present in all examined samples and outnumbered anammox bacteria usually by at least one order of magnitude. 16S rRNA gene sequencing revealed a relatively high diversity of anammox bacteria with one Ca. Brocadia cluster. Three additional clusters could not be affiliated to known anammox genera, but have been previously detected in other soil systems. Soil incubations using 15N-labeled substrates revealed that anammox processes contributed about <2% to total N2 formation, leaving nitrification and denitrification as the dominant N-removal mechanism in these soils that represent important buffer zones between agricultural land and ombrotrophic peat bogs.

Investigation of Ce3+ Mobility in NR211 Under RH Gradients

A proton exchange membrane fuel cell (PEMFC) is an attractive candidate for use in transportation and stationary applications as a clean energy source. A key component of a PEMFC is the polymeric ionomer membrane that serves as a proton conductor and prevents reactant gas crossover and electrical shorting. A widely used class of polymeric ionomers are perfluorinated sulfonic acid (PFSA) type ionomers because of their overall superior chemical and mechanical properties. The primary product of an operating fuel cell is water, but there are also small quantities of hydroxyl radical (•OH) and hydrogen peroxide (H2O2) produced from chemical and electrochemical reactions. These species react with non-fluorocarbon atoms or the sulfonic acid moiety to degrade the polymeric ionomer. To mitigate the chemical degradation of the polymeric ionomer, redox active cations such as Ce3+ and Mn2+ can be incorporated in membrane electrode assemblies (MEAs). These cations react at kinetically sufficient rates with •OH to form water. The resulting oxidized cation is subsequently reduced by H2O2 to complete the redox cycle. Within the polymeric ionomer, these cations associate (ion pair) with negatively charged sulfonate (SO3 -) groups. At the same time, cation complexation of the SO3 - groups modulates the local water content (l = nH2O/SO3 -) in the membrane. During fuel cell operation over a period of ten to 100 hours, cations are observed to diffuse on a centimeter length scale. The redistribution of cations can impact the fuel cell performance and mitigation of chemical degradation reactions. The movement of cations within an MEA is dictated by water content (l), water content gradients (Dl), and potential gradients. Therefore, the optimization of fuel cell performance and durability requires understanding how these factors impact cation movement. In this presentation, we will report isotropic diffusion coefficients of Ce3+ and Co2+ within a NR211 membrane over an array of uniform temperature and relative humidity values. The cation concentrations were monitored using FTIR, x-ray fluorescence, and UV-vis spectroscopies. The derived diffusion coefficients from these data show a strong dependence on relative humidity and temperature. These mobility rates are also consistent with redistribution of cations in operating fuel cells. In addition, cation movement under RH gradients will be presented. In this work, a dual-RH chamber apparatus was employed to study cation mobility rates over a range of RH chamber values and temperatures. For example, uniformly Ce3+-doped NR211 membranes clearly exhibit cation migration from the high to the low RH chamber (Figure 1a) and the mobility of cations in the low RH chamber is greatly reduced. Much additional experimentation with Ce3+ patch-doped NR211 strips (Figure 1b) has been conducted to elucidate the influence of water gradients on the rate and extent of cation mobility. Finally, a 1-D in-plane Ce3+ transport model that was developed from these data will be discussed. Figure 1

How important is carbonate dissolution in buried sandstones: evidences from petrography, porosity, experiments, and geochemical calculations

Burial dissolution of feldspar and carbonate minerals has been proposed to generate large volumes of secondary pores in subsurface reservoirs. Secondary porosity due to feldspar dissolution is ubiquitous in buried sandstones; however, extensive burial dissolution of carbonate minerals in subsurface sandstones is still debatable. In this paper, we first present four types of typical selective dissolution assemblages of feldspars and carbonate minerals developed in different sandstones. Under the constraints of porosity data, water–rock experiments, geochemical calculations of aggressive fluids, diagenetic mass transfer, and a review of publications on mineral dissolution in sandstone reservoirs, we argue that the hypothesis for the creation of significant volumes of secondary porosity by mesodiagenetic carbonate dissolution in subsurface sandstones is in conflict with the limited volume of aggressive fluids in rocks. In addition, no transfer mechanism supports removal of the dissolution products due to the small water volume in the subsurface reservoirs and the low mass concentration gradients in the pore water. Convincing petrographic evidence supports the view that the extensive dissolution of carbonate cements in sandstone rocks is usually associated with a high flux of deep hot fluids provided via fault systems or with meteoric freshwater during the eodiagenesis and telodiagenesis stages. The presumption of extensive mesogenetic dissolution of carbonate cements producing a significant net increase in secondary porosity should be used with careful consideration of the geological background in prediction of sandstone quality.

Effects of Cell Temperature and Reactant Humidification on Anion Exchange Membrane Fuel Cells.

The performance of an anion exchange membrane fuel cell (AEMFC) under various operating conditions, including cell temperature and humidification of inlet gases, was systematically investigated in this study. The experimental results indicate that the power density of an AEMFC is susceptible to the cell temperature and inlet gas humidification. A high performance AEMFC can be achieved by elevating the cell operating temperature along with the optimization of the gas feed dew points at the anode and cathode. As excess inlet gas humidification at the anode is supplied, the flooding is less severe at a higher cell temperature because the water transport in the gas diffusion substrate by evaporation is more effective upon operation at a higher cell temperature. The cell performance is slightly affected when the humidification at the anode is inadequate, owing to dehydration of the membrane, especially at a higher cell temperature. Furthermore, the cell performance in conditions of under-humidification or over-humidification at the cathode is greatly reduced at the different cell temperatures tested due to the dehydration of the anion exchange membrane and the water shortage or oxygen mass transport limitations, respectively, for the oxygen reduction reaction. In addition, back diffusion could partly support the water demand at the cathode once a water concentration gradient between the anode and cathode is formed. These results, in which sophisticated water management was achieved, can provide useful information regarding the development of high-performance AEMFC systems.

Auxin like en humus líquido

Objetivo: Evaluar el efecto de muestras de humus líquido (HL) en el porcentaje, índice y velocidad de germinación de Lepidium sativum, Medicago sativa y Raphanus sativus.&#x0D; Diseño/metodología/aproximación: Se evaluó el efecto de muestras de humus líquido (HL), que se obtuvo a partir del extracto acuoso de una vermicomposta comercial. Se realizó un diseño completamente al azar empleando diferentes gradientes de concentración HL:agua (1 a 10-4 mg mL-1) y se comparó con el efecto de un gradiente de concentración de 10-10 a 10-2 mol L-1 de ácido indolacético (AIA). Se realizó un análisis de espectroscopia de infrarrojo a las muestras de HL y AIA, para la identificación de compuestoy/o estructuras moleculares similares entre ambas muestras.&#x0D; Resultados: Las semillas menos sensibles a los compuestos bioactivos presentes en la muestra de HL son M. sativa al presentar menor inhibición en todos los tratamientos, siendo más sensibles las semillas de L. sativum y R. sativus. Los tratamientos TC, TD y TE correspondientes a los extractos de HL mostraron tener ctividad biológica similar a los tratamientos T06, T07 y T08 del AIA, siendo el índice de germinación el principal bioensayo en donde se observa esta respuesta. El análisis de FT-IR del extracto de HL mostró semejanza al ser comparado con el espectro de AIA, encontrándose similitudes en las bandas correspondientes al grupo indol, que es el grupo funcional base del AIA.&#x0D; Limitaciones del estudio/implicaciones: Se recomienda realizar en una segunda etapa de investigación que incluya la extracción de compuestos indólicos a muestras de HL y su posterior purificación eidentificación, mediante técnicas espectroscópicas&#x0D; Hallazgos/conclusiones: Los efectos estimulantes e inhibitorios de la germinación se deben a la presencia de compuestos bioactivos con actividad biológica similar a los reguladores del crecimiento vegetal, por ello se analizaron las muestras de HL, empleando un equipo de espectroscopia de infrarrojo, encontrándose señales de compuestos con grupos funcionales similares al AIA. Esto nos permite dejar abierta la posibilidad a la presencia de AIA y buscar la caracterización del extracto de HL empleando técnicas de purificación e identificación como la espectrometría de masas.

Effects of pH2O, pH2 and fO2 on the diffusion of H-bearing species in lunar basaltic liquid and an iron-free basaltic analog at 1 atm

Abstract We have experimentally determined the diffusivity of water in a representative lunar basaltic liquid composition (LG) and in an iron-free analog of a basaltic liquid (AD) at the low water concentrations and low oxygen fugacities (fO2) relevant to the eruption of lunar basalts. Experiments were conducted at 1 atm and 1350 °C over a range of pH2/pH2O from near zero to ∼10 and a range in fO2 spanning ∼9 orders of magnitude (from 2.2 log units below the iron-wustite buffer, IW−2.2, to IW+6.7). The water concentrations measured in our quenched experimental glasses by secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy (FTIR) vary from a few ppm to ∼430 ppm. Water concentration gradients in the majority of our AD experiments are well described by models in which the diffusivity of water ( D w a t e r ∗ ) has a constant value of ∼2 × 10−10 m2/s, while our LG results indicate that D w a t e r ∗ in LG melt has a constant value of ∼6 × 10−10 m2/s under the conditions of our experiments. Water concentration gradients in hydration and dehydration experiments that were run simultaneously in H2/CO2 gas mixtures are well described by the same D w a t e r ∗ , and water concentrations measured near the melt-vapor interfaces of these experiment pairs are approximately the same. These observations strongly support an equilibrium boundary condition for our experiments containing >70 ppm H2O. However, dehydration experiments into nominally anhydrous CO2, N2, and CO/CO2 gas mixtures leave some scope for the importance of kinetics during dehydration of melts containing less than a few 10′s of ppm H2O. Comparison of our results with the modified speciation model (Ni et al., 2013) in which both molecular water and hydroxyl are allowed to diffuse suggests that we have resolved the diffusivity of hydroxyl ( D O H ) in AD and LG melts. Our results support a positive correlation between D O H and melt depolymerization. Best-fit values of D w a t e r ∗ for our LG experiments vary within a factor of ∼2 over a range of pH2/pH2O from 0.007 to 9.7 and a range of logfO2 from IW−2.2 to IW+4.9. The relative insensitivity of our best-fit values of D w a t e r ∗ to variations in pH2 suggests that H2 diffusion did not control the rate of degassing of H-bearing species from the lunar glasses of Saal et al. (2008); however, we cannot rule out a role for molecular H2 diffusion under lower-temperature and/or higher-pressure conditions than explored in our experiments. The value of D w a t e r ∗ chosen by Saal et al. (2008) for modeling the diffusive degassing of the lunar volcanic glasses is within a factor of ∼2 of our measured value in LG melt at 1350 °C. By coupling our LG results at 1350 °C with an activation energy of 220 kJ/mol (Zhang et al., 2017), we obtain the following Arrhenius relationship, which can be used to model syneruptive diffusive water loss from lunar melt beads: D w a t e r ∗ ( m 2 / s ) = 7.2 × 1 0 - 3 e x p - 2.6 × 1 0 4 T ( K ) .

Characteristics of the liquid and vapor migration of coarse-grained soil in an open-system under constant-temperature freezing

Liquid and vapor migration is the key factor in evaluating the frost heaving properties of coarse-grained soil (CGS) in the high-speed railway (HSR) subgrade in cold regions. A fluorescein tracer was applied to investigate the liquid and vapor migration characteristics of CGS during constant-temperature freezing tests. In addition, the effects of the initial water content on the liquid and vapor migration properties were studied in this paper. The results show that the vapor migration is the dominant factor that causes the water redistribution of CGS in the freezing process. The vapor migration exists both in the supply of the external water sources and internally in the CGS. Water mainly migrates upward in the form of vapor under the effect of a water content gradient and a temperature gradient. The amount of liquid and vapor coupling migration in CGS decreases with the increase in initial water content, followed by a lower amount of external water migration, particularly vapor migration, and a lower height of the upward migration of the liquid. Although the vapor migrates across the freezing front and continually moves upward, the degree of vapor migration will gradually decline with a certain impact time domain and zone.

A Moving Boundary Model for Isothermal Drying and Shrinkage of Chayote Discoid Samples: Comparison between the Fully Analytical and the Shortcut Numerical Approaches

A moving boundary model for food isothermal drying and shrinkage is applied to predict the time decay of water content and sample volume, as well as water diffusivity for chayote discoid slices in the temperature range 40–70°C. The core of the model is the shrinkage velocity v, assumed equal to the water concentration gradient times a shrinkage function α representing the constitutive equation of the food material under investigation. The aim is to provide a case study to analyze and quantify differences and accuracies of two different approaches for determining the shrinkage function α from typical experimental data of moisture content X/X0 vs. rescaled volume V/V0: a fully analytical approach and a shortcut numerical one.

Measurement of Air-Sea Methane Fluxes in the Baltic Sea Using the Eddy Covariance Method

Methane (CH4) is the second-most important greenhouse gas in the atmosphere having a significant effect on global climate. The ocean—particularly the coastal regions—have been recognized to be a net source of CH4, however, the constraints on temporal and spatial resolution of CH4 measurements have been the limiting factor to estimate the total oceanic contributions. In this study, the viability of micrometeorological methods for the analysis of CH4 fluxes in the marine environment was evaluated. We present one year of semi-continuous eddy covariance measurements of CH4 atmospheric dry mole fractions and air–sea CH4 flux densities at the Ostergarnsholm station at the east coast of the Gotland Island in the central Baltic Sea. The mean annual CH4 flux density was positive, indicating that the region off Gotland are a net source of CH4 to the atmosphere with monthly mean flux densities ranging between -0.1 and 36 nmol m−2s−1. Both the air–water concentration gradient and the wind speed were found to be crucial parameters controlling the flux. The results were in good agreement with other measurements in the Baltic Sea reported in the MEMENTO database. Our results suggest that the eddy covariance technique is a useful tool for studying CH4 fluxes and improving the understanding of air-sea gas exchange processes with high-temporal resolution. Potentially, the high resolution of micrometeorological data can increase the understanding of the temporal variability and forcing processes of CH4 flux.

Distribution of water in ceramic green bodies during drying

In order to investigate drying mechanisms at different stages, the distribution of water within the ceramic green bodies at different scales has been examined. The experimental measurements, using a simple weighing technique and Magnetic Resonance Imaging (MRI), show that during the first stage of drying involving shrinkage the material is constituted of uniquely solid and water with no gradient in water content within the sample. Then, during the second stage of drying, significant differences of water content as a function of position appear. As a complement, at the grain scale, observations using environmental scanning electron microscopy were made giving useful information on the solid–liquid–gas interfaces in the near surface part of the green body. Finally, the gradients in the water distribution were exploited to make a simple estimate of the diffusion coefficient of water with its dependence on the moisture content.

Internal fluctuations in green roof substrate moisture content during storm events: Monitored data and model simulations

Understanding how the moisture content in a green roof substrate varies during a storm event is essential for accurately modelling runoff detention. In this paper, a green roof test bed installed with moisture probes at three depths was used to understand how moisture content varies during storms. Detailed studies were conducted on five selected storm events. Physical characterisation tests and field-data based calibrations were performed to acquire the model parameters. Two alternative detention models, based on Reservoir Routing and Richard’s Equation, were validated against the measured green roof runoff and temporary moisture storage data. Once the moisture content exceeds local field capacity, its response at different depths occurs simultaneously during storms, although the recorded data indicate a vertical gradient in the absolute values of local field capacity. Both Reservoir Routing and Richard’s Equation can provide reasonable estimations of the runoff and the vertical moisture content profiles, although Richard’s Equation exhibited stronger vertical water content gradients than were observed in practise. The vertical water content profile is not sensitive to the soil water release curve, although the hydraulic conductivity function influences both the vertical water content profile and runoff rate. The modelled results are highly sensitive to the bottom boundary condition, with a constant suction head boundary condition providing a more suitable option than a free drainage boundary condition or a seepage boundary condition.

Water Diffusion in the Semi-Liquid State during Industrial Candy Preparation

In the domain of production of flavor delivery systems based on carbohydrate matrices, Hot Melt Extrusion (HME) is one of the processes used which implies a relatively slow water evaporation step compared to Spray Drying or other common processes. The HME process of generating liquid syrup is stable only at industrial scales. The drying kinetic associated to the syrup formation is followed by collecting the vapored water. This experiment is exploited to estimate the diffusion coefficient of liquid water in a continuously concentrating carbohydrate melt ranging from 30.4 to 10.2%w/w water content and at temperatures ranging from 100 to 116 °C. A combination of Fick, Arnold and Vogel-Tammann-Fulcher models was used to derive the viscosity of the solution, the gradient thickness at the surface of the stirred solution and the diffusion coefficient of water in the liquid under boiling conditions. It is here demonstrated that under continuous boiling conditions, the water concentration gradient depth from the surface of the solution has a dimension that is comparable to the size of the hydrated carbohydrate molecules and the diffusion coefficient of water in boiling carbohydrate solutions ranges from 5.10−9 cm.s−2 for low temperature and high water content to 10−11 cm.s−2 for high temperature and low water content.

Micro-Scale Numerical Simulation of Water Migration in Plant-Based Materials During Isothermal Drying

The isothermal drying of plant-based material, such as fruits and vegetables, is the most widely used drying technique to stabilize materiel and to increase their shelf life. However, drying is a high energy-consuming industry process, in which water removal obviously affects the quality of dried products. Therefore, it is crucial to understand the water migration mechanisms during drying for improving energy efficiency and ensuring better quality. Plant-based material generally has highly porous characteristics, and the major part of the water (about 80-90%) is present in the intracellular space, but not in the intercellular (pore) space. There are three pathways for water moving out from the cell: cell-to-cell, wall-to-wall, and intercellular transport. To better understand the water migration, a micro-scale numerical simulation method is proposed in this paper. In the presented method, the mathematical models of the three pathway are developed separately, then coupled through the mass flux, such as the flux of cell membrane. Based on COMSOL software, the water migration of cellular tissues of potatoes is simulated under isothermal drying conditions. It can be seen from the numerical results: (1) The permeability of the cell membrane has a large influence on the macroscopic water conductivity of a tissue, and the gradients of water content is maximum at the face between cell membrane and cell wall. (2) In the early stage of drying, the water content of plant materials is relatively high, and the water potential distribution of each cellular environments can be regarded as a balanced distribution; while in the late stage of drying, the water content of plant materials decreases and the equilibrium state no longer exists.

Time evolution of steep diffusion fronts in highly viscous aerosol particles measured with Mie resonance spectroscopy.

Field and laboratory measurements indicate that atmospheric organic aerosol particles can be present in a highly viscous state. In contrast to liquid state particles, the gas phase equilibration to ambient relative humidity (RH) can be kinetically limited and governed by condensed phase diffusion. In water diffusion experiments on highly viscous single aerosol particles levitated in an electrodynamic balance, we observed a characteristic shift behavior of the Mie scattering resonances indicative of the changing radial structure of the particle, thus providing an experimental method to track the diffusion process inside the particle. Due to the plasticizing effect of water, theory predicts extremely steep, front-like water concentration gradients inside highly viscous particles exposed to a rapid increase in RH. The resulting quasi step-like concentration profile motivates the use of a simple core-shell model describing the morphology of the non-equilibrium particle during humidification. The particle growth and reduction of the shell refractive index can be observed experimentally as redshift and blueshift behavior of the Mie resonances, respectively. We can deduce the particle radius as well as a core-shell radius ratio from the measured shift pattern and Mie scattering calculations. Using both the growth information obtained from the Mie resonance redshift and thermodynamic equilibrium data, we can infer a comprehensive picture of the time evolution of the diffusion fronts in the framework of our core-shell model. The observed shift behavior of the Mie resonances provides direct evidence of very steep diffusion fronts caused by the plasticizing effect of water and a method to validate previous diffusivity measurements.

Relationship between the shrinkage crack characteristics and the water content gradient of compacted clay liner in a landfill final cover

Shrinkage cracking is the primary reason for the anti-seepage failure of compacted clay liner (CCL) in a landfill final cover. With a focus on the surface crack characteristics and the water content distribution of three CCLs with different liquid limits and their mineral compositions, experiments were conducted to investigate the cracking mechanism of a CCL during the drying process. The results showed that the total crack ratio (TCR), the sum of the surface shrinkage crack ratio (SCR) and the surface boundary shrinkage ratio (BSR), is a function of the surface water content of a CCL. The change in the TCR with surface water content is consistent with the soil shrinkage characteristic curve (SSCC). The surface SCR is a function of the surface water content gradient of a CCL. The variations in the SCR with the water content gradient can be divided into the following three stages: the crack open stage, the crack linear expansion stage and the crack linear close stage. The effect of sample size, surface boundary shrinkage and shrinkage cracking are the main deformations of CCL specimens with low and high liquid limits, respectively, during the drying process. An increase in the amount of clay minerals in CCLs enhances the soil shrinkage capacity, leading to an increase in the SCR under the same water content gradient. A unified linear relationship exists between SCR/Kj (where Kj is the slope of the SSCC) and the water content gradient in the crack linear expansion stage and the crack linear close stage for different CCL types.

Calculation of the process duration of thermo-moisture treatment of semi-finished products based on animal and vegetable raw materials

Calculation of the parameters of studied systems heat treatment (the process duration, temperature distribution inside the product and in its mass change) is complicated both by external and internal moisture transfer. In this regard, a strict mathematical description of moisture and heat transfer between the surface of the semi-finished product, which must be considered as a capillary-porous body, and the surrounding medium should be based on a joint solution of hydrodynamics equations and convective heat- and mass transfer, taking into account the normal component of the mass flow on the body surface, which complicates the task. Consideration of such a task with regard to moisture transfer under the action of water content gradients, temperature and pressure is possible if the driving forces of transfer processes do not consider these potential gradients on the surface of a capillary-porous body, but the differences between potentials averaged over the surface and volume of the body. This theory successful application for widespread use in practical problems solving is complicated by the absence of a systematized database on the hygro- and hydro-mechanical equilibrium of treated semi-finished products with technological media. On the other hand, even in the presence of experimental data on hydro- and hygroscopic equilibrium, in this case there are not fields of transfer potentials, but only their average volume and mean surface values, which in principle does not allow calculating of heat treatment duration as the time to reach the required temperature in the middle of the product. Meat and fish products are treated at not too high temperatures and as a result gradients of transfer potentials inside capillary-porous bodies are not too great, therefore it can be considered that the internal moisture transfer does not change the temperature field inside meat and fish products significantly. Resource-saving modes of thermo-moisture treatment of combined products were justified: frying at t = 200 ° C, without humidification, duration - 5 min; baking at 180 ° C, water consumption for humidification (4.0-4.3)10-6 m3 / s with 10-15 minutes duration, providing a reduction in process losses of the finished product weight from 18% to 5-7%

Technical note: A simple and cost-efficient automated floating chamber for continuous measurements of carbon dioxide gas flux on lakes

Abstract. Freshwaters emit significant amounts of CO2 on a global scale. However, emissions remain poorly constrained from the diverse range of aquatic systems. The drivers and regulators of CO2 gas flux from standing waters require further investigation to improve knowledge on both global-scale estimates and system-scale carbon balances. Often, lake–atmosphere gas fluxes are estimated from empirical models of gas transfer velocity and air–water concentration gradient. Direct quantification of the gas flux circumvents the uncertainty associated with the use of empirical models from contrasting systems. Existing methods to measure CO2 gas flux are often expensive (e.g. eddy covariance) or require a high workload in order to overcome the limitations of single point measurements using floating chambers. We added a small air pump, a timer and an exterior tube to ventilate the floating chamber headspace and passively regulate excess air pressure. By automating evacuation of the chamber headspace, continuous measurements of lake CO2 gas flux can be obtained with minimal effort. We present the chamber modifications and an example of operation from a small forest lake. The modified floating chamber performed well in the field and enabled continuous measurements of CO2 gas flux with 40 min intervals. Combining the direct measurements of gas flux with measurements of air and waterside CO2 partial pressure also enabled calculation of gas exchange velocity. Building and using the floating chamber is straightforward. However, because an air pump is used to restart measurements by thinning the chamber headspace with atmospheric air, the duration of the air pump pause–pulse cycle is critical and should be adjusted depending on system characteristics. This may result in shorter deployment duration, but this restriction can be circumvented by providing a stronger power source. The simple design makes modifications of the chamber dimensions and technical additions for particular applications and systems easy. This should make this approach to measuring gas flux flexible and appropriate in a wide range of different systems.