Wyniki wyszukiwania - BazTech

1

Variable thermal conductivity in micropolar thermoelastic medium without energy dissipation possessing cubic symmetry

Ailawalia Praveen, Priyanka

International Journal of Applied Mechanics and Engineering

|

2023

|

Vol. 28, no. 1

1--10

EN

This investigation deals with the effect of variable thermal conductivity in a micropolar thermoelastic medium without energy dissipation with cubic symmetry. The normal mode technique is employed for obtaining components of physical quantities such as displacement, stress, temperature distribution and microrotation.

2

Impacts of chemical reactions on inclined isothermal vertical plate

Sundar Raj M., Nagarajan G., Murugan V. P., Muthucumaraswamy R.

International Journal of Applied Mechanics and Engineering

|

2023

|

Vol. 28, no. 2

64--76

EN

An accurate parameterization of an irregular surge across a continuously propelled circulation through an endless isothermal inclined plate has been investigated in the presence of a first-degree uniform chemical reaction. Both the plate’s temperature and the proximal intensity are increased systematically. To evaluate non-dimensional equations, the Laplace transform is utilized. The effect of velocity components on a range of physical parameters is investigated which include Sc, Pr, Gr, Gc, α, K and t. A proportionate increase of velocity with Gr and Gc was prominent. τ and Sh were mathematically determined.

3

An unsteady electro-magnetohydrodynamic two-liquid plasma flow along a channel of insulating porous plates with Hall currents

Rao V. Gowri Sankara, Raju T. Linga

International Journal of Applied Mechanics and Engineering

|

2023

|

Vol. 28, no. 2

90--112

EN

It is proposed to use the Hall currents to model the transient magneto-hydrodynamic two liquid flows and heat transfer of ionized gases propelled by a common pressure gradient via a horizontal channel consisting of parallel porous plates. For the distributions of velocity and temperature, the principal partial differential equations that explain heat transfer flow under the chosen constraints are resolved. Graphical representations are given for the distributions of velocity, temperature, and heat transfer rates. This research will be carried out using non-conducting porous plate’s channel.

4

Unsteady electro-magneto hydrodynamic flow and heat transfer of two ionized fluids in a rotating system with Hall currents

Raju T. Linga, Rao B. Venkat

International Journal of Applied Mechanics and Engineering

|

2022

|

Vol. 27, no. 1

125--145

EN

An unsteady flow and heat transmission of ionized gases via a horizontal channel enclosed by non-conducting plates in a rotating framework with Hall currents is examined using electro-magnetohydrodynamic (EMHD) two-fluid heat flow. The Hall current impact is taken into account by assuming that the gases are totally ionized, the applied transverse magnetic field is very strong. For temperature and velocity distributions in two-fluid flow regions, the governing equations are solved analytically. For numerous physical parameters such as the Hartmann number, Hall parameter, rotation parameter, viscosity ratio, and so on, numerical solutions are visually displayed. It was discovered that an increase in temperature in the two regions is caused by the thermal conductivity ratio. It was also realized that an increase in rate of heat transfer coefficient at the plates is caused by either the Hartman number or the Hall parameter.

5

Influence of slip parameter, viscous dissipation and Joule heating effect on boundary layer flow and heat transfer over a power-law stretching wedge-shaped surface with the correlation coefficient and multiple regressions

Ali Mohammad, Alim Md. Abdul

International Journal of Applied Mechanics and Engineering

|

2022

|

Vol. 27, no. 2

1--21

EN

The influence of slip parameter, viscous dissipation, and Joule heating parameter on MHD boundary layer nanofluid flow over a permeable wedge-shaped surface was analysed. The PDEs and the associated boundary conditions were transformed to a set of non-similar ODEs and the obtained system of equations was solved numerically with the help of the spectral quasi-linearization method (SQLM) by applying suitable software. This method helps to identify the accuracy and convergence of the present problem. The current numerical results were compared with previously published work and are found to be similar. The fluid velocity, fluid temperature, and nanoparticle concentration within the boundary layer region for various values of the parameters such as the slip effect, magnetic strength, Prandtl number, Lewis number, stretching ratio, viscous dissipation, suction, Brownian motion, Joule heating, heat generation, and thermophoresis are studied. It is observed that the Brownian motion, Joule heating, viscous dissipation, and thermophoresis lead to decreases in the heat and mass transfer rate. The skin friction coefficient enhances with slip, magnetic, permeability, and suction parameters, but reduces with the Brownian motion, wedge angle, and stretching ratio parameters whereas there is no effect of mixed convection, thermophoresis, heat generation parameters, the Prandtl and Eckert number.

6

Heat transfer effects on carbon nanotubes along a moving flat plate subjected to uniform heat flux

Ferdows M., Shamshuddin Md., Reza Motahar, Ara Quadir Raushan

International Journal of Applied Mechanics and Engineering

|

2022

|

Vol. 27, no. 4

66--81

EN

In the present paper, a theoretical analysis is made to investigate fluid flow and heat energy transformation features of single and multi-walled water functionalized carbon nanotubes (CNTs) with uniform heat inconstancy boundary conditions onward a flat plate. The liquid motion and momentum transfer of carbon nanotubes (CNTs) have been analyzed using a homogeneous flow model. Both single-wall CNTs (SWCNTs) and multi-wall CNTs (MWCNTs) used base fluids, namely, water. The thermophysical characteristics of CNTs regarding the solid volume fraction of CNTs are studied by applying empirical correlations. Similarity transformations have been used to the governing partial differential equations turning them into ordinary differential equations. The outcome of similarity transformations which are nonlinear ordinary differential equations subjected to reconstructed boundary conditions, are subsequently solved numerically using bvp4c. The effects of the governing parameters on the dimensionless velocity, temperature, and skin friction are investigated numerically and graphically. An increase in the volume fraction and the velocity ratio parameter increase the flow, the velocity, and the temperature profile. Regardless of any physical parameter, SWCNTs give better heat transfer than MWCNTs.

7

Odzysk i transfer ciepła z Data Center

Żuk Maciej

Chłodnictwo i Klimatyzacja

|

2022

|

nr 6

48--50

PL

Jakie rozwiązania dotyczące chłodzenia serwerowni są w ostatnim czasie coraz częściej rozważane przez inwestorów i dlaczego? Co mówią prognozy na przyszłość? Jako projektant postaram się w tym artykule odpowiedzieć na te i kilka innych pytań związanych z projektowaniem systemów chłodzenia pomieszczeń Data Center oraz wskazać zalecenia, które warto wziąć pod uwagę przy w procesie planowania.

8

The four-sided lid driven square cavity using stream function-vorticity formulation

Bagai Shobha, Kumar Manoj, Patel Arvind

Journal of Applied Mathematics and Computational Mechanics

|

2020

|

Vol. 19, nr 2

17--30

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.

9

Effects of radiation and Eckert number on MHD flow with heat transfer rate near a stagnation point over a non-linear vertical stretching sheet

Fenuga O. J., Hassan A. R., Olanrewaju P. O.

International Journal of Applied Mechanics and Engineering

|

2020

|

Vol. 25, no. 1

27--36

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 […].

10

The improvement of the rheological model for controlling the stress-strain state and humidity in the materials of museum pieces: zener thermodiffusion model for capillary-porous bodies

Dovhaliuk V. B., Chovnyuk Y. V., Ivanov E. A., Shyshyna M. O.

Zeszyty Naukowe. Quality. Production. Improvement

|

2019

|

No. 2 (11)

51--71

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.

11

Analysis of a chemically reactive MHD flow with heat and mass transfer over a permeable surface

Fenuga O. J., Aroloye S. J., Popoola A. O.

International Journal of Applied Mechanics and Engineering

|

2019

|

Vol. 24, no. 1

53--66

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.

12

A numerical method for viscous flow in a driven cavity with heat and concentration sources placed on its side wall

Ambethkar V., Basumatary L. R.

Journal of Applied Mathematics and Computational Mechanics

|

2018

|

Vol. 17, nr 3

17--30

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.

13

The Caputo vs. Caputo-Fabrizio operators in modeling of heat transfer process

Oprzędkiewicz K., Mitkowski W., Gawin E., Dziedzic K.

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2018

|

Vol. 66, nr 4

501--507

EN

In the paper two non-integer order, state space models of heat transfer process are compared. The first uses a known Caputo operator and the second – a new operator proposed by Caputo and Fabrizio in 2015. Both discussed models are modifications of a known, integer order, state space, semigroup model of heat transfer process. Parameters of both models were identified by means of optimization of MSE cost function with the use of simplex method, available in MATLAB. Both proposed models have been compared in the aspect of accuracy and convergence. Analytical and numerical results show that the Caputo-Fabrizio model is faster convergent and easier to implement than the Caputo model. However, its accuracy in the sense of MSE cost function is worse.

14

CAD supportive in design of multichannel pipe for automotive application

Kuczek Ł., Mroczkowski M., Richert M.

Journal of Machine Construction and Maintenance - Problemy Eksploatacji

|

2017

|

no. 4

71--80

EN

It is necessary to carry out investigations on device behaviour before it will work in real conditions. Helpful tools are CAD systems and numerical simulations on virtual geometric models. They allow relatively cheap and fast analysis of devices without using expensive real models. This paper presents a method of multichannel pipe design with the help of a CAD system in terms of its strength and working conditions as an internal heat exchanger with carbon dioxide as a refrigerant. Two aluminium alloys were chosen: AA 3103-H112 and AA 6060-T6, and several shapes of channels. Results show that the selection of proper materials is one of the most important stages. It affects the strength of the pipe. A second significant parameter is the shape of external channels. It has been shown that it is important to choose proper value of radius R1 (corner between upper area of external channel and lateral surface of external channel). For the analysed type of multichannel pipe, the most appropriate value of radius R1 was 1 mm. As for heat exchange between fluids in internal and external channels, an important parameter was the thickness of the wall between the mentioned channels. It has been demonstrated that heat exchange efficiency depends on wall thickness and on the way of achieving this.

PL

Często konieczne jest przeprowadzenie badania zachowania się urządzenia zanim będzie pracowało w warunkach rzeczywistych. Jednym z przydatnych narzędzi to umożliwiających są systemy CAD oraz symulacje numeryczne przeprowadzane na wirtualnych modelach geometrycznych. Pozwalają one na dokonanie stosunkowo taniej i szybkiej analizy urządzenia bez konieczności użycia kosztownych modeli rzeczywistych. W artykule przedstawiono metodę projektowania rury wielokanałowej przy pomocy systemów CAD pod kątem ich wytrzymałości i warunków pracy jako wewnętrznego wymiennika ciepła z dwutlenkiem węgla, pełniącym rolę czynnika chłodniczego. Do analizy wybrano dwa stopy aluminium: 3103-H112 i 6060-T6 oraz kilka różnych kształtów kanałów. Wyniki pokazały, że dobór odpowiednich materiałów jest jednym z najważ- niejszych etapów projektowania rur. Ma to wpływ na wytrzymałość rury. Drugim istotnym parametrem jest kształt kanałów zewnętrznych. Wykazano, że dobór odpowiedniej wartości promienia R1 (narożnik pomiędzy górną i boczną powierzchnią kanału zewnętrznego) jest istotny. Dla analizowanego typu rury wielokanałowej wartość promienia R1 równa 1 mm była najbardziej właściwa. W przypadku wymiany ciepła pomiędzy płynami w kanałach zewnętrznych i wewnętrznym ważnym parametrem była grubość ścianki pomiędzy wymienionymi kanałami. Wykazano, że efektywność wymiany ciepła zależy od grubości ścianki oraz od sposobu osiągnięcia jej zmiany.

15

Analytical solution of the dual phase lag equation describing the laser heating of thin metal film

Ciesielski M.

Journal of Applied Mathematics and Computational Mechanics

|

2017

|

Vol. 16, nr 1

33--40

EN

Heat transfer processes occurring in the micro-domains can be described using the dual-phase lag equation (DPLE). This equation can be applied as a model of heating of the thin metal film subjected to the femtosecond laser pulse. In the paper, the 1D dual phase lag equation containing the additional internal heat source resulting from the laser pulse irradiation and supplemented by the appropriate boundary and initial conditions is considered. Appearing in this equation two lag times τq the phase lag of the heat flux) and τT (the phase lag of the temperature gradient) are taken into account. An analytical solution of this equation under the assumption that τT > τq is presented. The separation of the variables technique and the Green’s function method are used in order to find this solution. In the final part of the paper, the example of computations is presented.

16

Unsteady MHD heat transfer in Couette flow of water at 4°c in a rotating system with ramped temperature via finite element method

Reddy G. J., Raju R. S., Rao J. A., Gorla R. S. R.

International Journal of Applied Mechanics and Engineering

|

2017

|

Vol. 22, no. 1

145--161

EN

An unsteady magnetohydromagnetic natural convection on the Couette flow of electrically conducting water at 4°C (Pr = 11.40) in a rotating system has been considered. A Finite Element Method (FEM) was employed to find the numerical solutions of the dimensionless governing coupled boundary layer partial differential equations. The primary velocity, secondary velocity and temperature of water at 4°C as well as shear stresses and rate of heat transfer have been obtained for both ramped temperature and isothermal plates. The results are independent of the mesh (grid) size and the present numerical solutions through the Finite Element Method (FEM) are in good agreement with the existing analytical solutions by the Laplace Transform Technique (LTT). These are shown in tabular and graphical forms.

17

3D Numerical Simulation of Laminar Flow and Conjugate Heat Transfer through Fabric

Zhu G., Kremenakova D., Wang Y., Militky J., Mishra R., Wiener J.

Autex Research Journal

|

2017

|

Vol. 17, no. 1

53--60

EN

The air flow and conjugate heat transfer through the fabric was investigated numerically. The objective of this paper is to study the thermal insulation of fabrics under heat convection or the heat loss of human body under different conditions (fabric structure and contact conditions between the human skin and the fabric). The numerical simulations were performed in laminar flow regime at constant skin temperature (310 K) and constant air flow temperature (273 K) at a speed of 5 m/s. Some important parameters such as heat flux through the fabrics, heat transfer coefficient, and Nusselt number were evaluated. The results showed that the heat loss from human body (the heat transfer coefficient) was smallest or the thermal insulation of fabric was highest when the fabric had no pores and no contact with the human skin, the heat loss from human body (the heat transfer coefficient) was highest when the fabric had pores and the air flow penetrated through the fabric.

18

Hot Layer Formation during the Crude Oil Fires

Jarosz W., Stawczyk J.

Zeszyty Naukowe SGSP / Szkoła Główna Służby Pożarniczej

|

2016

|

Nr 58 (tom 1) (2)

5--16

EN

The paper presents the research results on hot layer formation during the crude oil fires, the conditions for creating a hot layer, mechanisms of the boilover and its accompanying dangerous phenomena. The research was carried out in The Main School of Fire Service in Warsaw. In the experiments, crude oil was burned in tanks with the diameter of 1.4 m and two different heights – 0.7 and 1.4 m.

PL

W artykule przedstawiono wyniki badań nad formowaniem się warstwy gorącej, warunków tworzenia się warstwy gorącej, mechanizmu wyrzutu i zjawisk towarzyszących podczas pożarów ropy naftowej, które zostały przeprowadzone w Szkole Głównej Służby Pożarniczej w Warszawie. W eksperymentach spalano ropę naftową w zbiornikach o średnicy 1,4 m i dwóch różnych wysokościach – 0,7 i 1,4 m.

19

An analysis of the boundary conditions model influence on the ground temperature profile determination

Jaszczur M.

Computer Assisted Methods in Engineering and Science

|

2015

|

Vol. 22, no. 3

243--253

EN

In this work, the influence of boundary conditions model (environmental model) on the ground temperature profile is analyzed. A numerical model for transport phenomena in the area above the top ground surface and below in the ground is presented. The results of simulation – ground temperature profile and mean seasonal temperature which estimate the energy potential of the ground are presented. In addition, the results of implementation of five different environmental models for the area above the top ground surface are presented. It is found that none of the models is able to reproduce the temperature variation similar to the reference (most complex) model accuracy. On the other hand, it is found that with a slight error a similar result for low ground depth can be obtained using the simplest Model 1.

20

Wall temperature prediction in annular geometry during post-dryout heat transfer

Anghel I. G., Anglart H.

Journal of Power Technologies

|

2014

|

Vol. 94, nr 5

1--7

EN

In this paper a new approach to predict wall temperature during post-dryout heat transfer in annuli with flow obstacles is presented. The proposed approach takes into account the obstacle specifics and location in the channel to determine the onset of post-dryout patch. The wall temperature in the dry patch area is predicted from a correlation that takes into account the developing post-dryout heat transfer regime. The method is applied to post-dryout conditions in an annulus with pin spacers and achieves a significant improvement in prediction accuracy compared to other reference methods.