Mass Transfer Apparatus Research Articles

Экспериментальное исследование гидравлических характеристик сферических насадок для массообменных аппаратов

A critical analysis of the trends in the development of nozzles for mass transfer devices is given, some designs are described in which the transfer of heat and mass is organized from the standpoint of today technically the most perfect. It is shown that the specific surface, the free specific volume of the nozzle and the hydraulic resistance of the layer are determined as the main characteristics of irregular type packing bodies. The scheme and description of an experimental setup for determining the hydrodynamic characteristics of nozzles in laboratory conditions are given. The results of studies of the hydrodynamic parameters of a layer consisting of a spherical hollow irregular nozzle for a dry and irrigated column are presented. The singular velocities of the gas flow corresponding to the transition points (points of deceleration, suspension, inversion or choking) to different hydrodynamic modes of operation of the filling mass transfer columns (film, intermediate, turbulent) and corresponding pressure drops have been experimentally determined. The dependences of the hydraulic resistance of the nozzle layer on the gas velocity in the column for dry and irrigated nozzles with a 1 m high layer are determined. The main reasons for the decrease in gas pressure in the layer of the irrigated nozzle are indicated. The singular gas flow velocities and their corresponding pressure drops are calculated using known empirical dependencies for dry and irrigated nozzles. The results of experimental studies and engineering calculations were compared, thereby proving the possibility of using computational equations with satisfactory accuracy (up to 15%). The study of the hydrodynamics of the layer and its hydraulic characteristics has shown that the spherical, hollow nozzle design with evenly spaced holes on the surface provides an effective redistribution of working phases in the mass transfer apparatus.

Artificial gravity in heat and mass exchange apparatus for the life support system of manned space missions

Different water recovery systems for deep space flight are analyzed; the existing systems and their shortcomings are briefly shown. The construction of a centrifugal mass transfer apparatus is presented, it could work in weightlessness conditions. The experimental data for the centrifugal apparatus in the mode of separation of the gas and liquid mixture are presented. The pressure was about 8 meters of water column for proposed construction. The formula for calculating the pressure for a scoop pump is given, which takes into account the rotation frequency, volume flow rate, the geometric dimensions and location of the scoop. Principle schemes for using a new centrifugal mass exchange device for water recovery systems and for capturing atmospheric moisture condensate are proposed. The features of the proposed schemes are analyzed and their potential advantages are determined. The main tasks for future experimental studies of the heat and mass transfer centrifugal apparatus are defined.

ГИДРОДИНАМИКА РОТОРНОГО ДИСКОВОГО АБСОРБЕРА

The hydrodynamics of a new rotary mass transfer apparatus is considered. It is shown that the most important hydrodynamic characteristics of the apparatus operation are: the average drop diameter, the initial drop velocity, the drop rise time, the drop rise height

РАЗРАБОТКА МЕТОДИКИ ГИДРОДИНАМИЧЕСКИХ ЭКСПЕРИМЕНТОВ С ДИСКОВЫМ РАСПЫЛИТЕЛЕМ

. A technique for hydrodynamic experiments has been developed to study a disk atomizer in a rotary mass transfer apparatus. In the course of experiments, the indicator method determines the average residence time of the liquid on the disk contact device, the volume of liquid retained on the disk contact device, the average diameter of the droplets formed, and the height of the gas-liquid layer

РАЗРАБОТКА РОТОРНОГО ТАРЕЛЬЧАТОГО АБСОРБЕРА

A new design of a rotary mass transfer apparatus is proposed. The technical result of the invention is to increase the intensity of mass transfer processes and reduce the cost of metal for the manufacture of the apparatus

Calculation method for heat and mass transfer apparatuses with porous plastic contact devices

The development of effective contact devices for heat and mass transfer apparatuses, which allow increasing the intensity of heat and mass transfer processes, reducing the size and cost of technological equipment, is an important practical task of the modern food industry. In this regard, the high efficiency of foam contact devices is noted, due to the developed specific surface and low hydraulic resistance. In the course of the study, a general classification of these devices has been proposed; schematic diagrams of the constructions of foam packings and trays have been given, a brief comparative analysis of their application area has been carried out. The main stages of calculation of highly efficient heat and mass transfer apparatuses with cellular plastic contact devices, including the determination of the basic geometrical characteristics of cellular materials, packing height (plate thickness), number of packing sections (number of plates), hydraulic resistance of packed and plate apparatus, have been described in detail. An example of an engineering calculation of a distillation heat and mass transfer apparatus with packed and plate-shaped foam contact devices for the separation of a binary mixture "ethyl alcohol - water" has been considered. The results of the calculation are presented in tabular and graphical form and allow us to conclude that it is most expedient to use packed foam contact devices with smaller dimensions and hydraulic resistance.

THE INFLUENCE OF DIFFERENT FACTORS ON THE MAISOTSENKO CYCLE EFFECTIVENESS

An important problem in the heat industry is the significant cost of energy resources for air conditioning. Therefore, energy-efficient refrigeration systems based on renewable energy sources and evaporative air cooling, as well as air-conditioning systems according to the Maisotsenko cycle using psychrometric energy of the environment are of great importance. This paper presents the results of experimental and numerical research of the influence of various factors on the efficiency of indirect evaporative heat and mass transfer apparatus on the M-cycle on the basis of a new unit cell.
 An experimental stand of a heat and mass transfer apparatus with vertically arranged plate channels was developed for experimental research. Experimental studies of heat and mass transfer in the new unit cell were conducted in a wide range of Reynolds numbers 200…1200, temperature 16… 30 °С, relative humidity 30… 50 %. The calculated study was performed using a modified ε-NTU method. Studies have shown that the thermodynamic efficiency of a wet bulb thermometer at a Reynolds number below 500 exceeded one. According to the results of computational studies, the influence of cell length and surface intensification of dry channels on thermodynamic efficiency was determined. Shown the effect of changes in thermodynamic efficiency in the range of 86…94 % increase in efficiency by 1 % leads to an increase in cell length by 7 %. The value of the enhancement factor increases with increasing air flow regime, so when the heat and mass transfer surface area increases by 50 % and the Reynolds number 200, the thermodynamic efficiency increases by 14 %, and with the Reynolds number 800 – by 28 %. The dependence of the thermodynamic efficiency of the cells at the dew point on the relative humidity of the inlet air have a maximum, which with increasing Reynolds number shifts toward larger values of relative humidity.
 Unlike traditional air conditioning devices, the M-cycle heat and mass exchanger does not use a steam compression cycle, so energy costs are spent only on the operation of the fan to pump air, which is a more environmentally friendly and energy efficient way of air conditioning.

Demonstration of the model of physicochemical processes in heavy liquid metal cooled reactors in an example of the THEADES experiment simulation

Activities have been currently underway across the world to build heavy liquid metal-cooled reactors. Thus, for example, the ALFRED and BREST-OD-300 reactor designs use lead coolant, while the MYRRHA and CLEAR-I reactors use lead–bismuth coolant. The high corrosive and erosive activity of the coolant requires regulations oxygen concentration (1 ÷ 4E-6 wt.%) and flow velocity (0.5 ÷ 2.5 m/s). Due to the complex geometry of the reactor circulation circuit flow paths, numerical simulation methods are used extensively to justify scheduled modes of operation for liquid metal coolants. Correct justification of the complex oxygen transport processes in liquid metals requires the respective physicochemical computation model, which takes into account the main reactions of oxygen with the coolant and the structural materials.This paper presents a physicochemical model, which includes the following processes: erosion, growth, and dissolution of the two-layer oxide film, coagulation and dissolution of metal oxides in the circuit with subsequent deposition on filtering elements, and inflow from mass transfer apparatuses. StarCCM+, a commercial CFD code, was used as the tool in this study. The physicochemical model was implemented using models of passive impurities, which are used to simulate oxygen transport in the circulation circuit.Capabilities of the presented model were demonstrated based on the results of investigating thermohydraulic and physicochemical processes obtained at the THEADES experimental facility. The duration of the simulation was 1000 h.The distributions of impurity concentrations, increased erosive activity areas, as well as the total amount of oxides deposited on filter and the amount of oxygen entering the circuit have been obtained as a result of the calculations. The surface distribution of the oxide film thickness on the test facility surfaces contacting the coolant has also been calculated. These data can be extrapolated to reactor elements that operate under conditions that are similar to the considered experiment. For example, fuel assemblies.Simulation of thermocouples, as well as taking into account manufacturing technology made it possible to improve the accuracy of calculating the flow’s thermohydraulic characteristics as compared to earlier studies.

Increasing Efficiency of Contact Devices of Column Mass-Transfer Apparatuses When Using Thermal Fractionation Processes

Increasing Efficiency of Contact Devices of Column Mass-Transfer Apparatuses When Using Thermal Fractionation Processes

Theoretical studies of H2S, SO2 and O2 absorption in mass exchanged apparatus with a continuous bubbling layer and mechanical dispersion of an absorbent

The paper reports the results of theoretical studies on kinetic and technological characteristics of oxygen, hydrogen sulfide and sulfur(IV) oxide absorption by water in mass-transfer apparatus of two various types: absorber with a continuous bubbling layer (AСBL) and horizontal absorber with bucket-shaped dispersers (HABD). The main purpose of these studies was the theoretical reasoning for the choice of mass-transfer equipment used in the purification of exhaust gases from sulfur compounds. It was shown that the resistance of the gas phase in ACBL is less than the resistance of the liquid phase by (2.75…3.78)106, (3.43…4.78)104, and (2.18…3.05)103 times for oxygen, hydrogen sulfide, and sulfur oxide, respectively; and it can be neglected when calculating the mass transfer coefficient. It was found that an increase in the diameter of the bubble from 1.510–3 m to 3.010–3 m leads to a decrease in the mass transfer coefficient by 1.63 times. It was calculated that the values of mass transfer coefficients in ACBL for H2S and SO2 are much higher than for O2, so the purification process will be controlled by the rate of oxygen absorption. It was found that the gas phase resistance during the absorption of oxygen and hydrogen sulfide for HABD has virtually no effect on the mass transfer coefficients and can be neglected. For the absorption of gases that are low-concentrated with respect to sulfur(IV) oxide, the mass transfer coefficient in HABD is determined by the resistance of the gas phase, and the optimal droplet diameter is within 2.00.5 mm. It was calculated that the technologically expedient initial speed of dispersed drops is 12 m/s, and their diameter is 1.5…3.0 mm for the industrial HABD. It was shown that the values of kinetic and technological indicators of mass transfer in HABD are several orders of magnitude higher than those in ACBL and have a significant potential for intensification.

ADSORPTION OF ACTIVE CHLORINE AND TECHNOLOGY OF AN AQUEOUS SOLUTION DECHLORINATION BY MODIFIED ACTIVATED CARBON

The influence of the modified activated carbon activation type on the degree of adsorption of active chlorine from the aqueous solution was studied. The influence of water flow rate and purification process duration on the adsorption of active chlorine by modified activated carbon was researched and the optimal parameters of the dechlorination regime were determined. The proposed method of extraction of active chlorine by modified activated coal obtained from peach shells can be used in natural and sewage treatment processes for the removal of the active chlorine and chlorine compounds. The design of the mass transfer apparatus with a fixed layer of adsorbent has been developed. The technology of dechlorination aqueous solution by modified activated carbon allows to increase the efficiency of purification up to 99%.

Разработка усовершенствованной конструкции массообменного аппарата для реакторных установок с жидкометаллическим теплоносителем

This work was intended to develop an improved mass transfer apparatus for reactors with liquid-metal coolant. The prototypes were existing designs of mass transfer apparatuses developed by the Institute of Physics and Power Engineering (IPPE) JSC. The study yielded an improved design for mass transfer apparatus with adjustable coolant flow. The findings of this work made it possible to resolve the challenge of coolant flow control in the main duct of primary reactor circuits with Pb-Bi coolant.

Review on the Performance Evaluation of Thermal Exchangers using Different Baffle Designs

The thermal performance of a heat exchanger depends upon various parameters like inlet temperature of hot fluid, type of hot fluid, type of cold fluid, the shape of baffles, the material of baffles, baffles angle, and property of ribs. Basically fluid flow and heat transfer characteristics largely depend upon the Reynolds number (Re). Reynolds number is basically the ratio of inertia force to viscous force. Re is only the factor by which we can decide whether the fluid is laminar or turbulent in shell and tube type of heat exchanger. The heat exchanger is an adiabatic device in which heat is transferred from one fluid to another fluid across a plate surface. In this paper, we have introduced some special types of triangular baffles with rectangular channels. The purpose of this apparatus is to enhance the performance of the heat exchanger. Heat exchangers, nowadays, are one of the most important heat & mass transfer apparatuses in industries like oil refining; heat treatment plants, electric power generation, etc. are long service life.

Study of the Relative Spray Loss in a Mass Transfer Apparatus with a Zigzag Regular-Structured Packing

Study of the Relative Spray Loss in a Mass Transfer Apparatus with a Zigzag Regular-Structured Packing

Evaluation of the Efficiency of Transfer Processes in a Rotary Apparatus

This paper considers the possibility of using vortex devices for interphase interaction while carrying out various physical and chemical processes in the chemical, food, gas production, construction and other industries. In the processes of mass transfer, one or several distributed components perform the transition from one phase to another through the active surface of their interface. To perform the implementation of these processes in absorbers, rectifiers, adsorbers, extractors effectively, the developed surface of the interacting phases acquire s a particular significance. Most of the chemical reactions in reaction devices and heterogeneous media occur when the initial distributed substances are supplied to the reaction zone and when the resulting products are removed from the chemical interaction zone through the phase interface. The processes under consideration are also used in solving environmental problems, viz. for sanitary cleaning of ventilation gases, wet cleaning of emissions. During evaporation, absorption, rectification, wet cleaning of gases and other processes, the problem of preventing the entrainment of liquid droplets with the gas flow is of great importance. One of the designs of a rotary multistage mass transfer apparatus is considered which makes it possible to achieve a finely dispersed liquid spray, uniform in height, with an ascending cross-flow of gas. The diagrams of installations for carrying out the experiment are given. On the basis of experimental studies, the dependence of the average diameter of dispersed liquid droplets on the geometric and hydrodynamic parameters has been obtained. The dispersed composition is described and dependences are given for determining the main characteristics used in physicochemical processes. The theoretical calculation of the movement of particles of the dispersed phase in the working volume of the apparatus at different flow rates of liquid and gas has been carried out. Theoretical and experimental methods were used to estimate the carryover of the liquid phase, an analysis of the process was carried out, and practical recommendations were given.

Effect of Temperature on 2-Ethylhexanol Nitration Process in a Unit with a Centrifugal Mass Transfer Apparatus

The effect of nitrating mixture and 2-ethylhexanol temperatures on the yield and purity of 2-ethylhexyl nitrate produced in a continuously operating unit having a centrifugal mass transfer apparatus (nitrator) is studied. It is demonstrated that elevation of temperature of the reagents from 12 to 20°C enhances the yield and purity of the desired product. The degree of completeness of the chemical reaction in the nitrator and the coil heat exchanger was determined using materials balance equations.

Intensification of mass transfer processes through the impact of the velocity gradient on hydrodynamics and stability of liquid droplets in a gas flow

The article investigates the dependencies between the intensity gradient of the gas flow velocity and the circulation intensity in a liquid droplet. The droplet’s hydrodynamics in a gas flow in the counterflow mass transfer apparatus was considered. A mathematical model considering the effect of the circulation flow inside the droplet on mass transfer intensification was developed. It was confirmed that the intensity of radial flow in a droplet depends on the velocity gradient. It was shown how this gradient affects the circulation flow of a liquid inside the droplet and its movement in a vortex gas flow. A system of nonlinear differential equations describing the translational motion of a liquid droplet in a gas flow was developed. The stability region for droplet’s movement was found. Kinematic characteristics of a droplet in a gas flow were obtained. The results allowed increasing the efficiency of mass transfer equipment.

Calculation of Hydrodynamic Characteristics of Apparatus with Regular Tubular Packing

Among the apparatuses with a regular arrangement of packing elements creating an in-phase mode of vortex interaction, which ensures high efficiency of the processes, it is interesting to use a standard tubular packing. Such packing allows additional advantages associated with heat supply or extraction directly in the contact zone of the interacting phases, which is very important for conducting some chemisorption processes. The research covers such hydrodynamic regularities as hydraulic resistance during a heat carrier movement in pipes and during external flow around a tubular beam, retained liquid amount and gas content of layer in the external flow around the tubular beam with liquid and gas flows. The research was carried out using an experimental setup with a heat and mass transfer apparatus with regular tubular packing. The medium used during experiments is water-air. The research methodology included standard methods for determining hydraulic resistance and retained liquid amount and visual observation and photographing of gas-liquid flows. The novelty of the research was equations – one for calculating the hydraulic resistance in pipes, taking into account local resistances and pipe roughness. The other ones for determining the pressure losses during the external flow around the tubular beam, the retained liquid amount, and the gas content of the layer, taking into account the vortex interaction of gas and liquid flows. Graphical and calculated dependences of the investigated hydrodynamic characteristics were obtained as a result of the conducted research of the hydraulic resistance during the heat carrier movement in the pipes, as well as the hydraulic resistance and the retained liquid amount during the external flow around the tubular beam with a change in the gas velocity and irrigation density. When the heat carrier flows in the pipes, the numerical values of the hydraulic resistance in the transient mode do not exceed 1.5 kPa, in the developed turbulence mode in the range of the Reynolds number from 1·104 to 6·104 DР varies from 1.5 to 53 kPa. With the external flow around the tubular beam, in the developed turbulence mode wg = 4 m/s and L = 25 m3/m2h, the hydraulic resistance is 85 Pa, the retained liquid amount is 4.5·10-3 m. The change in the irrigation density in this mode (developed turbulence) in the L range from 10 to 100 m3/m2h leads to an increase in the hydraulic resistance from 65 to 160 Pa, the retained liquid amount from 2.16·10-3 to 13.6·10-3 m. The calculated dependencies are the basis of the method for calculating the hydrodynamic characteristics of the apparatus with the regular tubular packing, which can be used to calculate industrial devices.

Control of operating modes of an electroadsorption apparatus with a fixed layer of adsorbent

This paper provides a new scheme and algorithm of automated control of modes of operation of electroadsorption mass transfer apparatuses are presented on the example of a continuously operating electroadsorber with a fixed adsorbent layer. The required values of technological parameters and ranges of their regulation were obtained during the calibration of technological parameters at the stage of commissioning of the electric adsorption mass transfer equipment, also in an automated mode. A detailed description and algorithm of the stages of calibration of technological parameters of electroadsorption apparatuses with a fixed adsorbent layer are given in the second part of this work (Calibration of technological parameters of an electroadsorption apparatus with a fixed layer of adsorbent). The principle of automated control consists in self-adaptation of the mass exchange system to optimal productiveness, due to the imposition of adjustable electric fields of a given intensity on the adsorption processes and recognition of the most effective hydromechanical modes flow about of the surfaces of the adsorbent granules with a continuous gas phase flow using the turbulization index, that is, assessing the contribution of the inertial component of the structure filtration flow of a continuous gas phase flow through the adsorbent layer. A self-adaptive automated control system for electroadsorption processes will allow achieving the highest levels of gas emissions purification, with optimal energy costs for mass transfer processes, and will provide an opportunity to smooth out technological, large-scale and other factors inherent in specific mass transfer processes and apparatus designs. The most important feature of the developed self-adaptive control system is multi-functionality and a wide range of variation of operating modes from energy-saving optimal modes to emergency capture modes in cases of emergency emissions and unexpected bursts of concentrations of harmful captured substances from the continuous gas phase flow.

Comparative evaluation of effectiveness indexes of column packings in benzol absorbers

Coke-oven gas is produced during coking of charge coal in a coking chamber and it constitutes a mix of different substances. A composition of different components in the gas depends on a composition of the coal charge and conditions of the coking. At a recovery plant, aromatic hydrocarbons are retrieved from the coking gas by absorption oil in packed absorbers. Mass-transfer apparatus demand the equability of the phase distribution. Hydrodynamic conditions, appearing inside contacting apparatus, determinate the effectiveness of the mass-transfer, which means that unbiased evaluation of any given mass-transfer apparatus can be made while simultaneous considering its hydrodynamic and mass-transfer indicators. The different types of column packing have been investigated in this study. The calculations of benzol absorbers have been performed basing on the initial data using the standard methodologies for the recovery plant of JSC EVRAZ NTMK coke and by-product enterprise. For comparison of the results obtained, the complex indexes of effectiveness, that simultaneously take into account the mass-transfer rate, the device capacity, the features of packings and energy cost, have been used.