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EN
The purpose of this study is to investigate the influence of an external magnetic field on heat and mass distribution across a moving isothermal sectional surface. The temperature is elevated to ( ) of the plate. The proximity intensity is increased to the concentration of the plate ( ). The study addresses a range of physical factors, including time, velocity profile, temperature, and intensity, as well as thermal Grashof number (Tg), mass Grashof number (Tm), Schmidt number (Sc), and Prandtl number (Pr). The dimensionless equations are addressed using both the Laplace-transform technique and the finite difference method, which is used to analyze the energy, momentum, and concentration equations. The results are illustrated through graphical representations, and the tabular manner to showcase various flow parameters. The results indicate that the velocity increases proportionally with changes in (Tg) and (Tm). As the angle (α) rises, the velocity shows a clear incremental pattern when the magnetic field strength decreases. Local skin friction correlates positively with the angle (α), Sc, and Pr, and negatively with Gr, Gc, and time. The study includes a Nusselt number table for various parameters corresponding to an increase in the Prandtl number, as well as the Sherwood number for different components as the Schmidt number escalates. This work helps us learn more about the complicated interactions between magnetic fields and fluid movement, which is useful for many engineering and science projects.
EN
We look at the viscous free-convective transitional magnetohydrodynamic thermal and mass flow over a plate that is always perforated and standing upright through permeable media while thermal radiation, a thermal source, and a chemical reaction are all going on. There is additional consideration for the Soret effect. The plate receives a normal application of a transversely consistent magnetic field. The magnetic Reynolds number is considerably lower considering the axial applied magnetic field instead of the induced magnetic field. The models that control mass, heat, and fluid flow are turned into two-dimensional shapes, and the answers are found by running numerical simulations using the MATLAB algorithm bvp4c. In realistic circumstances, the outcomes have been illustrated graphically. Several fluid properties have been found to have an impact on velocity, temperature, and concentration profiles. There is noticeable increase in velocity along with the growth of the permeability parameter and Soret number. Other dimensionless parameters have a significant impact on the fluid velocity. Likewise, the temperature profile diminishes as the radiation parameter has increased. The concentration distribution falls as the heat source parameter expands. Also, the analysis is encompassed in tabular form for the shearing stress, Nusselt number, and Sherwood number. The combined knowledge of heat and mass moving through viscous flows can be used to make a wide range of mechanisms and processes. These include biological reactors, therapeutic delivery systems, methods of splitting, aerodynamic aircraft design, and modeling for sustainability. It also optimizes automotive radiators and engine efficiency, and it improves cooling systems.
EN
Results of numerical simulation of heat, mass and momentum transfer in cold storage chambers for vegetables along with experimental validation are presented in the paper. The case of an experimental napa cabbage cold store was analysed. Coupling of processes occurring in the bulk of vegetables and in the air cooler accomplished by means of the user-defined functions in Ansys Fluent are presented. The model combines the cooling capacity with the processes occurring in the bed of cabbage, namely transpiration and respiration, and other heat gains/losses that occur in the chamber. The model of porous media was applied in terms of the bed of vegetables and air cooler. A thermal non-equilibrium model was assumed. The output of simulations were the heat and mass transfer coefficients. The numerical results were compared with the measurements. A good agreement between numerical results and experimental data in terms of temperatures in the bulk of vegetables and relative humidity was achieved. The moisture loss in stored products resulting in total loss of weight was analysed. Good agreement with experimental results and regions of the highest shrinkage of the stored vegetables were indicated.
EN
The reduction in CO2 emissions is now a very popular topic. According to the International Energy Agency, CO2 emitted in 2021 was 6% more than that emitted in 2020. Carbon capture and storage (CCS) is gaining popularity as a possible solution to climate change. Experts estimate that industry and power plants will be responsible for 19% of total CO2 emissions by 2050. This paper presents the design of a semi-industrial-scale system for CO2 capture based on the moving bed temperature swing adsorption technology. According to the results of laboratory tests conducted by the SINTEF industry, this technology demonstrates high capture efficiency (>85%). The CO2 capture medium involved in adsorption is activated carbon passing through individual sections (cooling, heating, adsorption), where CO2 is bonded and then released. The heat and mass transfer processes are realised on the developed stand. The heat exchangers use steam and water as the heating/cooling medium. The paper reviews the existing solutions and describes the developed in-house design of heat exchangers that will ensure heat transfer conditions being a trade-off between economic and efficiency-related issues of the CO2 capture process. The designed test stand will be installed in a Polish power plant and is expected to meet the method energy intensity target, set at ≤ 2.7 MJ/kg CO2, with a capture efficiency exceeding 85%. The aim of the work was to develop and solve technical problems that would lead to the construction of a CO2 capture station with parameters mentioned above. This stand uses an innovative method where CO2 is captured by contacting the fluid (gases) with solid particles. The heat exchange associated with the heating and cooling of the adsorbent had to be solved. For this purpose, heat exchangers were designed with high thermal efficiency and to prevent the formation of mounds.
EN
The article presents a simple prototype system based on the concept of indirect regenerative evaporative cooling (IREC) thermodynamic cycle for electronics applications. The key problem of selecting porous capillary material is discussed and preliminary experimental results are presented using IR thermography. The presented research is an initial step towards the development of a laboratory-validated, fully operational IREC system for high-power electronics.
PL
W artykule przedstawiono prototypowy układ chłodzenia oparty na koncepcji cyklu termodynamicznego pośredniego regeneracyjnego chłodzenia wyparnego (IREC) do zastosowań w elektronice. Omówiono kluczowy problem doboru porowatego materiału kapilarnego i przedstawiono wstępne wyniki eksperymentów z wykorzystaniem termografii w podczerwieni. Przedstawione badania stanowią wstępny krok w kierunku opracowania zweryfikowanego laboratoryjnie, w pełni funkcjonalnego systemu IREC do odprowadzania ciepła w systemach elektronicznych dużej mocy.
PL
Pośrednie chłodzenie wyparne staje się coraz bardziej popularne ze względu na wykorzystanie przyjaznych dla środowiska czynników chłodniczych: powietrza (R-729) i wody (R-718). Istotą procesu jest wymiana ciepła i masy, która zachodzi w wymienniku. Opracowania zagraniczne szeroko opisują nowoczesne technologie wspomagające ten proces, podczas gdy polskojęzyczna literatura nie porusza zagadnienia niemalże w ogóle. W artykule skupiono się na dwóch głównych innowacjach wynikających z przeglądu literatury (od 2010 roku): wprowadzeniu nanopłynów opartych na wodzie oraz zastosowaniu materiałów porowatych na powierzchni kanału mokrego. Przeanalizowano kluczowe parametry stosowane do opisu urządzeń do chłodzenia wyparnego takie jak sprawności: termometru mokrego, punktu rosy oraz egzergetyczną, wydajność chłodniczą, EER oraz COP. Przedstawiono wyniki badań nanopłynów jedno-, dwu- i trzyskładnikowych. Analiza wykazała poprawę parametrów charakteryzujących pośrednie urządzenia wyparne wynoszące od kilku do kilkudziesięciu procent przy zastosowaniu nanopłynów w zależności od temperatury powietrza na wlocie. Dokonano przeglądu stosowanych materiałów porowatych stanowiących powierzchnie kanału mokrego. Wydzielono cztery główne typy stosowanych materiałów: porowate ceramiczne oraz włókna naturalne, polimerowe i tekstylne. Zestawiono wady oraz zalety stosowania tych materiałów w wymiennikach pośrednich w celu ułatwienia wyboru rodzaju materiału. Określono, że spośród dwóch omawianych modyfikacji w pierwszej kolejności należy skupić się na aplikacji materiałów porowatych, jako że są one związane bezpośrednio z konstrukcją wymiennika. Natomiast nanopłyny można zastosować w urządzeniach istniejących. W podsumowaniu stwierdzono, że rozwój technologii pośredniego chłodzenia wyparnego może stanowić istotne oraz ekologiczne uzupełnienie obecnie stosowanych sprężarkowych systemów chłodzenia.
EN
Indirect evaporative cooling is becoming increasingly popular due to the use of environmentally friendly refrigerants: air (R-729) and water (R-718). The main idea of the process is the heat and mass transfer that takes place in the exchanger. Foreign studies extensively describe modern technologies supporting this process, while the Polish-language literature does not cover the issue almost at all. The article focuses on two main innovations resulting from the literature review (as of 2010): the introduction of water-based nanofluids and the use of porous materials on the surface of the wet channel. Main parameters used to describe evaporative cooling devices include wet thermometer, dew point, and exergetic efficiencies, cooling capacity, EER, and COP. Results for single-, two-, and three-component nanofluids are presented. The analysis showed performance improvements for indirect evaporative units of several to tens of percent with nanofluids, depending on the inlet air temperature. The applied porous materials used on the surface of the wet channel were reviewed. Four main types of materials used have been distinguished: porous ceramic and natural fibers, polymer fibers, and fabric fibers. The advantages and disadvantages of using these materials in indirect heat exchangers were summarized to facilitate the choice of material type. It was determined that of the two modifications discussed, the application of porous materials should be focused on first, since they are directly related to the construction of the heat exchanger. In contrast, nanofluids can be applied to existing devices. Eventually, it was pointed out that the development of indirect evaporative cooling technology can be an important and ecological complement to the currently used compressor systems.
EN
This paper proposes a mathematical model that allows expanding the scope of research into the mechanism of heat transfer during explosive boiling, cavitation and boiling of multicomponent liquids, identifying the most influential factors and optimizing technological processes. The proposed model takes into account the processes of heat accumulation in the high-boiling part of liquid mixtures (for example, emulsions) and the use of this energy in the process of boiling their thermolabile part, as well as for superheating the resulting steam in steam bubbles. This effect can also be used to evaluate the effects of liquid boiling in thermodynamically unstable regions of liquid media.
8
Content available Agitation efficiency of different physical systems
EN
Efficiency of agitation was considered for different physical systems on the basis of our own experimental studies on homogenisation, heat and mass transfer as well as gas hold-up. Measurements were performed for different physical systems: Newtonian liquids of low and higher viscosity, pseudoplastic liquid, gas–liquid and gas–solid–liquid systems agitated in vessels of the working volume from 0.02 m3 to 0.2 m3. Agitated vessels of different design were equipped with a high-speed impeller (10 impellers were tested). Comparative analysis of the experimental results proved that energy inputs (power consumption) should be taken into account as a very important factor when agitation efficiency is evaluated in order to select a proper type of equipment. When this factor is neglected in the analysis, intensification of the process can be estimated only.
EN
In this paper, an unsteady 2-D incompressible fluid flow with heat and mass transfer in a four-sided lid driven square cavity is investigated numerically. The top, bottom, left, and right walls of the square cavity move to the right, left, downward and upward respectively. All four sides of the cavity move with a uniform velocity. The flow variables are simulated below the critical Reynolds numbers with isothermal and mass-transfer conditions in the square cavity. We have used a streamfunction-vorticity (ψ - ξ) formulation to investigate the fluid flow in terms of flow variables ψ, ξ, T and C at low Reynolds numbers (Re). The Prandtl number (Pr) and Schmidt number (Sc) have been chosen as 6:62 and 10, 50, 100, 150 respectively, in order to calculate the numerical solutions of T and C. The matrix method has been used to evaluate the stability and convergence of the numerical scheme. The conditions obtained from the matrix method have been used to arrive at the numerical solutions with desired accuracy.
EN
This work investigates the effects of radiation and Eckert number on an MHD flow with heat transfer rate near a stagnation-point region over a nonlinear vertical stretching sheet. Using a similarity transformation, the governing equations are transformed into a system of ordinary differential equations which are solved numerically using the sixth order Runge-Kutta method with shooting technique. Tabular and graphical results are provided to examine the physical nature of the problem. Heat transfer rate at the surface decreases with radiation, Eckert number and as radiation increases, the flow temperature also increases for velocity ratio parameters […].
EN
This work investigates a three-dimensional Magnetohydrodynamic (MHD) nanofluid flow with heat and mass transfer over a porous stretching sheet. Firstly, partial differential equations are transformed into coupled non-linear ordinary differential equations through a similarity variables transformation and solved by Galerkin Finite Element Methods (FEM). The effects of thermal radiation, viscous dissipation and chemical reaction on the fluid flow are considered. The behaviour and properties of pertinent flow parameters on the velocity, temperature and concentration profiles are presented and discussed graphically. The effects of the friction coefficient parameter, Nusselt and Sherhood numbers are also shown and considered using tables. The work is in good agreement in comparison with the recent work in literature.
EN
The characteristic of nano sized particles mass flux conditions are engaged in this investigation. Here we assume that the nano sized particle flux is zero and the nano sized particle fraction arranged itself on the boundary layer. With this convincing and revised relation, the features of Buongiorno relation on three-dimensional flow of Carreau fluid can be applied in a more efficient way. The governing partial differential equations of continuity, momentum, energy and concentration equations which are transmitted into set of pair of nonlinear ordinary differential equations utilizing similar transformations. The numeric solutions are acquired by engaging the bvp4c scheme, which is a finite-difference code for solving boundary value problems. A parametric study is accomplished to demonstrate the impact of Prandtl number, Weissenberg numbers, radiation parameter, chemical reaction parameter, thermophoresis parameter, Brownian motion parameter and Lewis number on the fluid velocity, temperature and concentration profiles as well skin friction coefficient, Nusselt number and Sherwood number within the boundary layer. From this we find the way in which magnetic parameter contributes to the increase in local skin fraction, and the decrease in the Nusselt and Sherwood numbers in these cases. The effects of the velocity temperature and concentration profile are obtained and presented graphically.
EN
The drying and humidifying processes of capillary-porous (colloid) bodies occur during the production of various materials for the consumer goods industry, building materials, storage of museum pieces, etc. It is known that the main linkage forms of the moisture and colloid capillary-porous bodies (CCPBs), namely adsorption, capillary condensation and capillary linkage of the free moisture in the cavities of the above bodies, depend on the temperature and relative humidity of drying/humidifying agent. It means that the CCPBs behave in a peculiar way depending on the temperature and humidity fields. The problems of CCPBs drying (or humidifying) process include the issue of the heat and humidity transfer both in the middle of the body and in the boundary layer on the interface of phases “body (object of drying/humidifying process) – environment”. The drying/humidifying intensity is at its maximum when the possibilities of the heat and mass transfer in the boundary layer correspond to the possibilities of moisture and heat moving inside the object of drying/humidifying process. The properties of the CCPB as material possessing specific elastic-viscous properties are described within the framework of O.Y. Ishlinskiy - O.R. Rzhanitsin generalized elastic-viscous body theory. A comparative analysis of the above mentioned CCPB’s properties from the point of view of Zener thermodiffusion theory is conducted. The mechanism of moisture transferring from the CCPBs’ central layers (as object of drying/humidifying process) up to their surfaces is developed. The theoretical researches examined the drying/humidifying phenomena for both the entire volume of the CCPB and three structural directions. It is noted that drying/humidifying of CCPBs is a complicated heat and mass transfer process accompanied by mechanisms of molecular nature determining the kinetics of their running. It is shown that the appropriate equations’ solution of molecular-molar heat and moisture transfer under the appropriate boundary (limit) conditions allows to describe the fields, i.e. the distribution of transfer potentials (the temperature and moisture content in the CCPB as object of drying/humidifying) at any time of the appropriate process. The drying/humidifying curves (“drying/humidifying rate versus CCPB humidity”) and the temperature curves (“CCPB temperatures versus CCPB humidity”) reflect the nature of the drying/humidifying processes. In the framework of the proposed generalized rheological model of CCPB, the residual deformations of bodies for various load types (the time-varying stress applied to the CCPB) is estimated.
EN
The article presents the results of research of thermophysical peculiarities obtaining volumetric amorphous structures in metals and alloys. This technology differs mainly the realization internal heat removal by means of local heat sink (inoculator). A mathematical model of melting inoculator in melts for optimizing the process of obtaining massive amorphous structures, which allows to reduce time of experimental research and material resources to create massive amorphous structures. Mathematical modeling of processes heat and mass transfer inoculator in melts allows you to identify peculiarities of the technological process, and establish influence inoculator on the degree of amorphization melt. The results provide an effective assessment of the intensity of heat transfer during the casting process, which makes it possible to estimate and predict the ability of alloys to the amorphization of the structure.
EN
An analytical solution of an MHD free convective thermal diffusive flow of a viscous, incompressible, electrically conducting and heat-absorbing fluid past a infinite vertical permeable porous plate in the presence of radiation and chemical reaction is presented. The flow is considered under the influence of a magnetic field applied normal to the flow. The plate is assumed to move with a constant velocity in the direction of fluid flow in slip flow regime, while free stream velocity is assumed to follow the exponentially increasing small perturbation law. The velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number distributions are derived and have shown through graphs and tables by using the simple perturbation technique.
EN
This paper investigates a chemically reactive Magnetohydrodynamics fluid flow with heat and mass transfer over a permeable surface taking into consideration the buoyancy force, injection/suction, heat source/sink and thermal radiation. The governing momentum, energy and concentration balance equations are transformed into a set of ordinary differential equations by method of similarity transformation and solved numerically by Runge- Kutta method based on Shooting technique. The influence of various pertinent parameters on the velocity, temperature, concentration fields are discussed graphically. Comparison of this work with previously published works on special cases of the problem was carried out and the results are in excellent agreement. Results also show that the thermo physical parameters in the momentum boundary layer equations increase the skin friction coefficient but decrease the momentum boundary layer. Fluid suction/injection and Prandtl number increase the rate of heat transfer. The order of chemical reaction is quite significant and there is a faster rate of mass transfer when the reaction rate and Schmidt number are increased.
17
EN
The article presents the results of research of thermophysical peculiarities obtaining volumetric amorphous structures in metals and alloys. This technology differs mainly the realization internal heat removal by means of local heat sink (inoculator). A mathematical model of melting inoculator in melts for optimizing the process of obtaining massive amorphous structures, which allows to reduce time of experimental research and material resources to create massive amorphous structures. Mathematical modeling of processes heat and mass transfer inoculator in melts allows you to identify peculiarities of the technological process, and establish influence inoculator on the degree of amorphization melt. The results provide an effective assessment of the intensity of heat transfer during the casting process, which makes it possible to estimate and predict the ability of alloys to the amorphization of the structure.
EN
This paper proposes a method to numerically study viscous incompressible two-dimensional steady flow in a driven square cavity with heat and concentration sources placed on its side wall. The method proposed here is based on streamfunction-vorticity (Ψ-ξ) formulation. We have modified this formulation in such a way that it suits to solve the continuity, x and y-momentum, energy and mass transfer equations which are the governing equations of the problem under investigation in this study. No-slip and slip wall boundary conditions for velocity, temperature and concentration are defined on walls of a driven square cavity. In order to numerically compute the streamfunction Ψ, vorticityfunction ξ , temperature θ, concentration C and pressure P at different low, moderate and high Reynolds numbers, a general algorithm was proposed. The sequence of steps involved in this general algorithm are executed in a computer code, developed and run in a C compiler. We propose that, with the help of this code, one can easily compute the numerical solutions of the flow variables such as velocity, pressure, temperature, concentration, streamfunction, vorticityfunction and thereby depict and analyze streamlines, vortex lines, isotherms and isobars, in the driven square cavity for low, moderate and high Reynolds numbers. We have chosen suitable Prandtl and Schmidt numbers that enables us to define the average Nusselt and Sherwood numbers to study the heat ad mass transfer rates from the left wall of the cavity. The stability criterion of the numerical method used for solving the Poisson, vorticity transportation, energy and mass transfer has been given. Based on this criterion, we ought to choose appropriate time and space steps in numerical computations and thereby, we may obtain the desired accurate numerical solutions. The nature of the steady state solutions of the flow variables along the horizontal and vertical lines through the geometric center of the square cavity has been discussed and analyzed. To check the validity of the computer code used and corresponding numerical solutions of the flow variables obtained from this study, we have to compare these with established steady state solutions existing in the literature and they have to be found in good agreement.
EN
This work is focused on the development and validation of experimental method for testing EC-aerosols under simulated conditions of human respiratory tract with variable aerosol residence time in the physiologically humid environment associated with the inhalation pattern. Initial results obtained using the laser diffractometry indicate the usefulness and applicability of developed method for EC-aerosol testing for a deeper understanding of simultaneous heat and mass transfer processes during EC-aerosol formation, inhalation and movement in the human respiratory tract.
PL
Praca koncentruje się na opracowaniu i walidacji metodyki badań doświadczalnych aerozoli uwalnianych z e-papierosów do środowiska odzwierciedlającego pod względem panującej wilgotności, temperatury oraz czasu przebywania aerozolu drogi oddechowe człowieka. Wstępne wyniki uzyskane przy użyciu dyfraktometru laserowego wskazują na przydatność zaproponowanej metody badania aerozoli do głębszego zrozumienia roli procesów wymiany ciepła oraz masy w trybie ich powstawania, inhalacji oraz transportu w drogach oddechowych.
EN
An analysis is presented to describe the hydromagnetic mixed convection flow of an electrically conducting micropolar fluid past a vertical plate through a porous medium with radiation and slip flow regime. A uniform magnetic field has been considered in the study which absorbs the micropolar fluid with a varying suction velocity and acts perpendicular to the porous surface of the above plate. The governing non-linear partial differential equations have been transformed into linear partial differential equations, which are solved numerically by applying the explicit finite difference method. The numerical results are presented graphically in the form of velocity, micro-rotation, concentration and temperature profiles, the skin-friction coefficient, the couple stress coefficient, the rate of heat and mass transfers at the wall for different material parameters.
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