Instrument for monitoring the moisture content of wheat grain in the production process of drying

A method and instrument are considered for monitoring the moisture content of grain directly in a drying chamber. The method is based on the dependence of temperature and moisture content of drying agent and its gradient at the outlet from the drying chamber on grain moisture content. The instrument makes it possible to monitor grain moisture content in the range 13–20%. The main absolute measurement error for grain moisture content does not exceed 0.8%. The instrument is made on a practicable and inexpensive fundamental basis, and is reliable and simple in operation.     

“Salt in a porous matrix” sorbent and sawdust as air driers for ventilation systems

The processes of moisture desorption by a sorbent-drier of the type of “salt in a porous matrix” and sawdust in convective flow, as well as under the acoustoconvective action, have been investigated. It has been shown that at a flow velocity of 31 m ⁄ sec the sorbent has a rather prolonged drying stage with a constant rate, and at a flow velocity of 13 m ⁄ sec this drying stage ends faster. It has been established that the velocity of the convective flow strongly influences the drying process of the sorbent, and the action of the acoustic field therewith produced no marked effect on the drying process. Moisture desorption from sawdust proceeds with a variable rate, and its intensity markedly increases under the action of the acoustic field. The influence of acoustic vibrations on the rate of moisture removal has a nonmonotonic character. The kinetics of the process of humidification of the sorbent-drier has been investigated. On the basis of the investigations made, a basic circuit for ventilating closed rooms by dried air with the use of sawdust or an IK-011-1 sorbent-drier has been proposed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 252–257, March–April, 2009.     

Design and development of energy efficient solar tunnel dryer for industrial drying

A natural convection poly house walk-in type solar tunnel dryer was designed and used for drying surgical cotton on industrial scale. This article deals with the basic design criterion used for development of solar tunnel dryer and result of drying of surgical cotton in actual use. A batch of surgical cotton of 600 kg by mass, having an initial moisture content of 40% wet basis from which 210 kg of water is required to be removed to get a desired moisture content of about 5% wet basis, is used as the drying load in designing the dryer. A drying time of 7–8 h is assumed for the anticipated test location (Udaipur, 27° 42′ N, 75° 33′ E) with an expected average solar irradiance of 5.5 kW m⁻². Average cost of drying one batch of surgical cotton in a solar tunnel dryer has been worked out to be approximately 4.63 USD as compared to 30.00 USD in the existing diesel fired dryer.     

Simulation of nonisothermal moisture transfer and stresses in wood in drying

We obtain a numerical solution for a two-dimensional problem of nonisothermal moisture transfer in the anisotropic structure of wood (lumber) in convective drying. On the basis of elasticity theory we determine internal thermal and moisture stresses. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 3, pp. 404–411, May–June, 1998.     

Modeling of nonisothermal heat and moisture transfer in capillary-porous media in periodic microwave heating

The interrelated system of heat-and moisture-transfer and electrodynamic equations for modeling superhigh-frequency drying of capillary-porous materials has been formulated. An example of solving the problem of heat and moisture transfer in microwave heating of a wood sample with allowance for the influence of surface forces on the process of migration of moisture has been given. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, pp. 3–11, January–February, 2007.     

Experimental investigation of the acoustic-convective drying of unhusked Korean rice

Experiments on determination of the kinetic curves of drying of unhusked Korean rice have been conducted on two (small-and large-scale) acoustic-convective dryers of capillary-porous materials of the Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences. Different regimes of drying were used. The characteristic time of drying to a prescribed final humidity has been determined; the absence of the influence of the scale factor on the kinetics of drying of rice has been shown. The coefficient of moisture conductivity of rice has been evaluated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 652–655, July–August, 2008.     

Determination of the kinetic curves of drying of blocks of adsorbents-dessicants with different cross sections of channels and of a granulated adsorbent on a change in the flow velocity

The kinetics of convective drying (regeneration) of different types of adsorbents-dessicants with different geometric parameters has been studied. It is shown that adsorbents of a “channel” (cellular) type have a long constant-rate stage of drying, whereas a granulated polydisperse adsorbent is mainly dried at a variable rate. Adsorbents having a maximum water yielding capacity have been revealed. It has been established that the velocity of a drying gas flow substantially influences the process of moisture extraction from all types of adsorbents. In order to describe the kinetic curves of the given phenomenon, a model of a relaxation kinetic equation that quite satisfactorily describes the kinetics of drying of the adsorbents studied was used. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 1, pp. 65–68, January–February, 2009.     

Modeling of the process of drying of a dispersed material by a superheated steam in a pneumatic-transport system

Mathematical modeling of the cyclic drying of a dispersed material moving in the ascending and descending flows of a superheated steam has been performed. The dependence of the moisture content of particles on the operating parameters of a pneumatic-transport system has been established. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 147–155, July–August, 2007.     

Kinetics of microwave drying of a free-flowing organic material

The kinetics of drying of a dense buckwheat layer in a microwave electromagnetic field of frequency 2.45 GHz has been investigated for different amounts of the material charged into a working chamber. Analysis of the kinetics curves has shown that the drying of the material studied is divided into the periods of heating, drying with a constant rate, and drying with a decreasing rate. The influence of the power supplied as well as the mass and dimensions of a sample on the rate of its drying has been investigated and a formula for calculating this rate has been obtained. It has been established that, in the process of drying of a disperse material, the amount of microwave energy converted into heat energy depends not only on the mass of a sample, but also on the thickness and area of its surface layer. Generalized equations for calculating the moisture content in a layer of a free-flowing material and its temperature have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 123–127, May–June, 2006.     

Development of Certain Aspects of the A. V. Luikov Heat- and Mass-Transfer Theory

It has been proposed that A. V. Luikov's system of heat- and mass-transfer equations be supplemented with balance differential equations of change in the temperature and degree of saturation of a medium with its motion in the material for an a priori unknown character of their change. The approach to determination of the relative coefficient of thermal diffusion, the criterion of phase transition, and the value of the Fo number for the beginning of the stage of a regular regime of a one- and two-dimensional plate and to evaluation of the notion of the “soft” and “hard” processes of drying has been refined. The method of allowance for the multidimensionality of a body has been developed. The practical absence of the influence of moisture exchange on heat exchange in drying has been proved. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 102–107, July–August, 2005.     

Efficiency of utilization of heat in the processes of convective drying and an equilibrium analysis

A method for evaluating the efficiency of convective dryers from the viewpoint of heat consumption has been proposed; the method is based on a comparison of the characteristics of the dryers to a standard: the process with an efficiency maximum possible under given conditions. The so-called equilibrium analysis assuming the absence of the internal heat and moisture gradients in the dried product is used. It has been shown that gradient-free processes limiting for all modes of phase contact with decrease in the drying intensity to zero possess the highest intensity. The basic rules of organization of economical drying have been formulated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 5, pp. 963–970, September–October, 2008.     

Drying of saturated lightweight concrete: an experimental investigation

The changes of moisture content during drying are experimentally investigated in the present work. Particular emphasis is placed on the initial stage of drying of saturated concrete, when moisture contents are high, since the resistance of the material to several deterioration processes is reduced at high moisture content levels, and experimental data for this stage of drying is lacking. The experimental investigation is performed for concrete cylinders of different lengths with one end exposed to drying. In this way, moisture flow is forced to be unidirectional. The gravimetric method is employed to obtain moisture content distribution in the material at different times of drying. The cylinders are made of lightweight concrete with varying water-to-cement ratios and moist curing times, and the influence of these variables upon the drying process is assessed. Higher initial water content and more rapid changes of water content occur in lightweight concrete with a higher w/c ratio. An increased moist-curing period results in a decrease of drying rates throughout the drying process.     

The effect of the horizontal vibrations on natural heat transfer from an isothermal array of cylinders

A numerical investigation is carried out to study an unsteady laminar natural convection heat transfer caused by an array of isothermal oscillating circular cylinders. Under oscillating conditions, flow and thermal fields are categorized into a class of moving boundary problems. In this study, the moving interfaces between the fluid and cylinders have been considered. The numerical model used in the present paper, is based on a 2D Navier–Stokes momentum and energy equations for an incompressible flow solver on an unstructured grid. Discretization of the governing equations including continuity, momentum and energy equations is achieved through a finite element scheme based on characteristic based split algorithm using the arbitrary Lagrangian–Eulerian approach to satisfy boundary movement. Besides a dual time stepping method is employed to capture unsteady flow and thermal characteristics. The working fluid is designated a Prandtl number of 0.71(air) and assumed to be incompressible with constant physical properties. The radiation, viscous dissipation and pressure work are also assumed to be negligible throughout this investigation. Fluid flow and heat transfer characteristics are examined in the domain of the Rayleigh number, cylinders spacing, amplitude, and frequency of oscillations such that: 10³ ≤ Ra ≤ 10⁵, 2 ≤ s/d ≤ 4, 0.5 ≤ l ≤ 2, and 0.1 ≤ f ≤ 0.4. The obtained results reveal that increment of Rayleigh number and cylinders’ spacing augment the average Nusselt of each cylinder as well as higher oscillation amplitude and frequency. Moreover, it was found that horizontal vibration makes vortices appear in the left and right area of the cylinders. These vortices reduce heat transfer from two upper cylinders.     

Simulation of thermal and moisture-content conditions on the upper layer of peat soils

The problem of two-dimensional interrelated heat- and moisture-transfer in the upper layer of soil is formulated taking into account exchange by heat and moisture with the ground-level air layer. On its basis a difference scheme was constructed and algorithms and a program were developed to calculate the processes of heat and moisture transfer. We evaluated the effect of various meteorological and hydrological factors and the composition of organogenic rocks on the change in the temperature and moisture-content conditions of peat deposits and soils. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 5, pp. 999–1005, September–October, 2000.     

Explosive fracture of closed cylinders

We present the results of numerical simulation of the process of fracture of thick-walled elastoplastic cylinders with bottoms caused by the explosion of a blasting charge placed inside the cylinders. We show that the influence of the scheme of explosive loading on spalling effects in the walls of the cylinders is significant. Scientific Research Institute of Applied Mathematics and Mechanics, Tomsk, Russia. Translated from Problemy Prochnosti, No. 4, pp. 44–51, July–August, 1997.     

Numerical analysis of the influence of rotary rear cylinders on a nonstationary wake behind an elongated body

The influence of rotary rear cylinders on a nonstationary wake behind a rounded-off plate is analyzed numerically based on the solution of nonstationary Navier-Stokes equations on multiblock computational grids by the finite-volume method. It is shown that the von Kármán vortex trail, which develops behind the body to the point of formation of a virtually steady jet flow, substantially weakens as the rotational velocity of the cylinders increases. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 3, pp. 606–613, May–June, 2000.     

Monitoring of Corrosion Under Insulations by Acoustic Emission and Humidity Measurement

We simultaneously monitored humidity and AE from active corrosion under insulation (CUI). For humidity monitoring, we developed an optical fiber sensor based on the moisture dependency of absorption of laser light by connecting coating of polyvinyl alcohol and CoCl₂ coating and pullulan coating in series on the fiber as a cladding layer. The sensor could be used to measure humidity of 65–95% RH at 80°C. The temperature dependence of the sensor was as small as 2.5% RH/10°C. We monitored active CUI by the acoustic emission technique and humidity sensing under wetting and drying cycles. Most AE signals were produced during the drying process in each wetting and drying cycle, and the AE rate increased with the time of wetness (period of humidification).     

Propagation of strain waves and compaction of a viscoelastic material by a cylinder rolling over it

This paper considers problems on the rolling of rigid driven and driving cylinders slipping on a compactible viscoelastic base. As a result of the investigation of the process of propagation of viscoelastic decaying strain waves in a deformable medium caused by a cylinder rolling over it and the action of the sliding friction forces, formulas and calculation algorithms have been obtained for determining the indices of the stressed-strained state and compactness of the base, the rolling resistance of the driven and diving cylinders, and the driving force of the driving cylinder. Calculations of these indices have been performed for the cases of cylinders rolling over a soil whose viscoelastic properties have been investigated experimentally. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 122–132, September–October, 2007.     

Evaluation of surface sealers for concrete hydraulic structures exposed to low temperatures

Many hydraulic structures exhibit downstream cracks and surface degradation due to porous and non air-entrained concrete cast only a few decades ago, wetting–drying and freezing–thawing cycles. These degradations could be prevented by minimizing surface saturation and water infiltration by sealing the concrete surface. Many different types of sealers, such as silanes, siloxanes, boiled linseed oil, epoxies, urethanes and cement-based products, are presently available on the market. However, despite their ready availability, very few or no laboratory or field evaluations have ever been undertaken to evaluate their effectiveness, specifically for hydraulic structures exposed to extremely low temperatures. Consequently, 60 different surface sealers were selected for laboratory evaluation, aimed at minimizing water or moisture infiltration, and to extend the service life of hydraulic structures, besides reducing the harmful effects associated with concrete surface deterioration. The tests carried out on these sealers comprised reduction of absorption and evaporation capacity, durability under freezing–thawing and wetting–drying cycles, acid rain, UV radiation, effect of various parameters, such as concrete water:cement ratio (W/C), sealers application temperature, pH variation, presence of hydrostatic pressure, etc. Preliminary data showed that silanes and siloxanes exhibited satisfactory results, however, products from the same family yielded variable results. This paper summarizes a part of a large study on concrete sealers for hydraulic structures in cold climates.     

Power-series solution for the two-dimensional inviscid flow with a vortex and multiple cylinders

The problem of a point vortex and N fixed cylinders in a two-dimensional inviscid fluid is studied and an analytical-numerical solution in the form of an infinite power series for the velocity field is obtained using complex analysis. The velocity distribution for the case of two cylinders is compared with the existing results of the problem of a vortex in an annular region which is conformally mapped onto the exterior of two cylinders. Limiting cases of N cylinders and the vortex, being far away from each other are studied. In these cases, “the dipole approximation” or “the point-island approximation” is derived, and its region of validity is established by numerical tests. The velocity distribution for a geometry of four cylinders placed at the vertices of a square and a vortex is presented. The problem of vortex motion with N cylinders addressed in the paper attracted attention recently owing to its importance in many applications. However, existing solutions using Abelian function theory are sophisticated and the theory is not one of the standard techniques used by applied mathematicians and engineers. Moreover, in the N ≥ 3 cylinder problem, the infinite product involved in the presentation of the Schottky–Klein prime function must also be truncated. So, the approach used in the paper is simple and an alternative to existing methods. This is the main motivation for this study.