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  1. 31 International Journal of Applied Mechanics and Engineering
  2. 5 Annual Set The Environment Protection
  3. 5 Mechanics and Mechanical Engineering
  4. 5 Rocznik Ochrona Środowiska
  5. 5 Studia Geotechnica et Mechanica
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  1. 3 Pop I.
  2. 2 Bhadauria B. S.
  3. 2 Chand S.
  4. 2 El-Kabeir S. M.
  5. 2 El-Kholy S. A.
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  1. 1 2023
  2. 3 2022
  3. 4 2021
  4. 7 2020
  5. 3 2019
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1
Content available PV panel cooling using stack effect
Rao Kudithi Nageswara, Ganesamoorthy Rajkumar
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
|
2023
|
T. 13, nr 3
83--85
EN
Unsatisfactory feat of the photo-voltaic cell is solitary in every of the foremost issues among the promotion of PV technology. A vital strand changing cell performance is operative temperature of the cell. The voltage of the cell, declines near directly with a rise in the operative temperature of the photo-voltaic cell. The temperature condition on the in-operative surface of a photo-voltaic panel remains usually 22–30°C beyond the normal temperature conditions. Upon the premise concerning those issues, the potency of the photo-voltaic cell will be refined by sustaining their operative temperatures as low as possible. This paper portrays a technique of PV/solar panel cooling using convection generated by the chimney effect. This paper considers the diminution of warmth from the Photo-voltaic panel for both active and inactive conditions.
PL
Niezadowalająca wydajność ogniwa fotowoltaicznego jest jednym z najważniejszych problemów związanych z promocją technologii PV. Istotnym czynnikiem wpływającym na wydajność ogniwa jest jego temperatura robocza. Napięcie ogniwa spada niemal bezpośrednio wraz ze wzrostem temperatury roboczej ogniwa fotowoltaicznego. Temperatura na powierzchni działającego panelu fotowoltaicznego pozostaje zwykle o 22–30°C wyższa od normalnych warunków temperaturowych. Zgodnie z założeniami dotyczącymi tych kwestii, moc ogniwa fotowoltaicznego zostanie poprawiona poprzez utrzymanie ich temperatury roboczej na jak najniższym poziomie. Niniejszy artykuł przedstawia technikę chłodzenia paneli fotowoltaicznych/solarnych z wykorzystaniem konwekcji generowanej przez efekt kominowy. W artykule uwzględniono zmniejszenie ciepła z panelu fotowoltaicznego zarówno w warunkach aktywnych, jak i nieaktywnych.
2
Content available Strouhal number effects on dynamic boundary layer evolution over a wedge surface from initial flow to steady flow: analytical approach
Bachiri Mohamed, Bouabdallah Ahcen
International Journal of Applied Mechanics and Engineering
|
2022
|
Vol. 27, no. 4
26--39
EN
The present work studies the effects of the physical parameter characterizing the laminar flow regime, namely the Strouhal number, on the evolution of the unsteady dynamic boundary-layer developed along a wedge surface. Similarity method is used to transform unsteady momentum equation to dimensionless form. Using superposition method between diffusion and convective flows solutions, an ad hoc velocity profile formula is proposed. The obtained results confirm perfectly the numerical data given by Blasius, Falkner-Skan and Williams-Rhyne for all Strouhal numbers. A new accurate analytical function of the local skin friction is established for all time values and for different wedge surface directions. In order to give further clarification on the flows evolutions from diffusion flow to convective flow, in the whole space domain, new skin friction coefficient curves are plotted for all Strouhal numbers and for different wedge surface directions.
3
Content available Combined effects of helical force and rotation on stationary convection of a binary ferrofluid in a porous medium
Kpossa M., Monwanou A. V.
International Journal of Applied Mechanics and Engineering
|
2022
|
Vol. 27, no. 2
158--176
EN
This work studies the simultaneous effects of helical force, rotation and porosity on the appearance of stationary convection in a binary mixture of a ferrofluid and on the size of convection cells. We have determined the analytical expression of the Rayleigh number of the system as a function of the dimensionless parameters. The effect of each parameter on the system is studied. The consideration of the simultaneous effect of the basic characteristics made it possible to determine the evolution of the convection threshold in the ferrofluid and then the size of convection cells. The analyzes of the various results obtained allowed us to deduce whether the convection sets in quickly or with a delay when the various effects taken into account in the study are considered simultaneously.
4
Content available remote Numerical Investigation of Heat Transfer in Garment Air Gap
Zhang Yijie, Jia Juhong
Autex Research Journal
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2022
|
Vol. 22, no. 1
89--95
EN
This article aimed to study the characteristics and mechanisms of 3D heat transfer through clothing involving the air gap. A three-dimensional finite volume method is used to obtain the coupled conductive, convective, and radiative heat transfer in a body-air-cloth microclimate system. The flow contours and characteristics of temperature, heat flux, and velocity have been obtained. The reason for the high flux and temperature regions was analyzed. Computational results show that the coupled effect of the air gap and the airflow between the skin and garment strongly influences the temperature and heat flux distribution. There are several high-temperature regions on the clothing and high heat flux regions on the body skin because the conductive heat flux can cross through the narrow air gap and reach the cloth surface easily. The high-speed cooling airflow brings about high forced convective heat flux, which will result in the temperature increase on the upper cloth surface. The radiative heat flux has a strong correlation with the temperature gradient between the body and clothing. But its proportion in the total heat flux is relatively small.
5
Content available Positive solutions for nonlinear Robin problems with conviction
Gasiński Leszek, Papageorgiou Nikolaos S.
Science, Technology and Innovation
|
2021
|
Vol. 12, no. 1
23--36
EN
We consider a Robin problem driven by the p-Laplacian and with a reaction which is gradient dependent (convection). Using truncations and perturbations, we show that the problem has at least one positive smooth solution.
6
Content available Investigation of the influence of liquid phase motion on the solidification process in the three-dimensional region
Węgrzyn-Skrzypczak Ewa
Journal of Applied Mathematics and Computational Mechanics
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2021
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Vol. 20, nr 1
103--111
EN
In this paper, the numerical model of solidification process with the motion of the liquid phase is presented. The mathematical description of the considered problem is based on the heat conduction equation with convective term and the Navier-Stokes equations with continuity equation. The numerical model uses the Finite Element Method (FEM). The simulations of the solidification process with or without the fluid motion effect are presented and discussed.
7
Content available Effects of rotation on Jeffrey nanofluid flow saturated by a porous medium
Rana Gian C.
Journal of Applied Mathematics and Computational Mechanics
|
2021
|
Vol. 20, nr 3
17--29
EN
In this paper, the effects of rotation on a Jeffery nanofluid flow in a porous medium which is heated from below is studied. Darcy model is employed for porous medium and the Jeffrey fluid model is used as a base fluid. The Navier-Stokes equations of motion of fluid are modified under the influence of the Jeffrey parameter, naoparticles and rotation. The basic perturbation technique based on normal modes is applied to derive the dispersion relation for a Rayleigh number. The effects of the Taylor number, Jeffrey parameter, Lewis number, modified diffusivity ratio, nanoparticles Rayleigh number and medium porosity on the stationary convection of the physical system have been analyzed analytically and graphically. It is observed that the rotation parameter has a stabilising influence for both bottom/top-heavy configurations.
8
Content available The effect of thermal modulation on double diffusive convection in the presence of applied magnetic field and internal heat source
Manjula S. H., Suresh P., Rao M. G.
International Journal of Applied Mechanics and Engineering
|
2021
|
Vol. 26, no. 1
135--155
EN
The investigation of thermal modulation on double-diffusive stationary convection in the presence of an applied magnetic field and internal heating is carried out. A weakly nonlinear stability analysis has been performed using the finite-amplitude Ginzburg-Landau model. This finite amplitude of convection is obtained at the third order of the system. The study considers three different forms of temperature modulations. OPM-out of phase modulation, LBMO-lower boundary modulation, IPM-in phase modulation. The finite-amplitude is a function of amplitude ,Tδ frequency ω and the phase differenceθ . The effects of Tδ and ω on heat/mass transports have been analyzed and depicted graphically. The study shows that heat/mass transports can be controlled effectively by thermal modulation. Further, it is found that the internal Rayleigh number iR enhances heat transfer and reduces the mass transfer in the system.
9
Content available The Investigation of Thermophysical Characteristics of Porous Insulation Materials Based on Burshtyn TPP Ash
Koshlak Hanna, Kaczan Anna
Rocznik Ochrona Środowiska
|
2020
|
Tom 22, cz. 1
537--548
EN
Thermophysical characteristics of porous thermal insulation materials (PTM) are generally determined by the structure, size, type and shape of pores, as well as by their mutual arrangement in the material. Thermal conductivity is one of the most important among these characteristics, is caused by different physical processes and can be reduced to three types: conduction, convection and radiation. Literature sources imply that thermal conductivity dependence is represented as an exponential function. These dependencies fail to have a sufficiently clear and pronounced nature and do not allow developing an analytical expression to describe this function, especially at high values of material density. In our experiments, the thermal conductivity coefficient was determined in the dry and sorption humidity states, not exceeding 20%. The thermal conductivity of porous thermal insulation materials was studied using an IT-λ-400 device. Cylindrical test specimens, 5 mm thick and 15 mm in diameter, were placed in the device and heated to 800°C. Within this temperature range, the material thermal conductivity was determined according to the standard procedure described in the device operating instructions. The observed data were processed using the designed experiment approach. Thermal conductivity is considered as the target function (Y, W/(m K)). The experiment was conducted according to the program of the central composite rotatable second-order design by Box-Hunter. The factors, studied in the previous series of experiments, are considered as controllable ones. Variable factors shall meet these criteria during experiment design process. 16 experiments were conducted at basic levels and supplemented by another 10 experiments at star points.
PL
Właściwości termofizyczne porowatych materiałów termoizolacyjnych (PTM) są ogólnie określone przez strukturę, wielkość, rodzaj i kształt porów, a także przez ich wzajemne rozmieszczenie w materiale. Przewodność cieplna jest jedną z najważniejszych spośród tych cech, jest spowodowana różnymi procesami fizycznymi i może być zredukowana do trzech rodzajów: przewodzenia, konwekcji i promieniowania. Źródła literatury sugerują, że zależność przewodności cieplnej jest reprezentowana jako funkcja wykładnicza. Zależności te nie mają wystarczająco wyraźnego charakteru i nie pozwalają na opracowanie analitycznego wyrażenia opisującego tę funkcję, szczególnie przy wysokich wartościach gęstości materiału. W naszych eksperymentach współczynnik przewodności cieplnej został określony w stanie suchym i wilgotności sorpcji, nie przekraczając 20%. Przewodność cieplną porowatych materiałów termoizolacyjnych badano za pomocą urządzenia IT-λ-400. Próbki cylindryczne o grubości 5 mm i średnicy 15 mm umieszczono w urządzeniu i ogrzano do 800°C. W tym zakresie temperatur przewodność cieplna materiału została określona zgodnie ze standardową procedurą opisaną w instrukcji obsługi urządzenia. Obserwowane dane zostały przetworzone przy użyciu zaprojektowanego podejścia eksperymentalnego. Przewodność cieplna jest uwzględniana jako funkcja celu (Y, W/(m K)). Eksperyment przeprowadzono zgodnie z programem centralnego obrotowego kompozytowego projektu drugiego rzędu firmy Box-Hunter. Zmienne czynniki muszą spełniać te kryteria podczas procesu projektowania eksperymentu. Przeprowadzono 16 eksperymentów na poziomach podstawowych i uzupełniono o kolejne 10 eksperymentów w punktach gwiazdowych.
10
Content available Experimental Research of Temperature Distribution on the Surface of the Front Plate, of a Flat Plate Heat Exchanger
Orłowska Magdalena
Rocznik Ochrona Środowiska
|
2020
|
Tom 22, cz. 1
256--264
EN
The purpose of the work was to perform experimental tests on a plate heat exchanger. For this purpose, a laboratory test stand located in the hall of the Koszalin University of Technology was used. The experiment concerned checking the isothermal face of a flat panel radiator. Temperature distributions were checked at three board heights and in twelve finite elements. Temperature distribution fields were obtained depending on the flow rates tested.
PL
Celem pracy było wykonanie badań eksperymentalnych na płytowym wymienniku ciepła. W tym celu wykorzystano laboratoryjne stanowisko badawcze zlokalizowane w sali Politechniki Koszalińskiej. Eksperyment dotyczył sprawdzenia izotermicznej powierzchni płaskiego grzejnika płytowego. Rozkłady temperatury sprawdzono na trzech wysokościach płyty i w dwunastu elementach skończonych. W zależności od badanych natężeń przepływu uzyskano pola rozkładu temperatury.
11
Content available Unsteady MHD natural convective boundary layer flow and heat transfer over a truncated cone in the presence of pressure work
Ajay C. K., Srinivasa A. H.
Journal of Applied Mathematics and Computational Mechanics
|
2020
|
Vol. 19, nr 1
5--16
EN
The aim of the present paper is to analyse the effect of MHD on unsteady natural convection boundary layer flow and heat transfer over a truncated cone in the presence of pressure work. Suitable transformation is utilized to form a system of coupled non-linear partial differential equations for governing both the flow and heat transfer. These equations have been solved numerically by utilizing an implicit finite difference scheme along with quasilinearization method. Here, the computed numerical results are displayed graphically in terms of the local Nusselt number, skin friction, temperature distribution, and velocity distribution for various values of the magnetic and pressure work parameters along with the fixed Prandtl number
12
Content available The effect of magnetic field dependent viscosity on ferromagnetic convection in a rotating sparsely distributed porous medium - revisited
Prakash J., Kumar P., Manan S., Sharma K. R.
International Journal of Applied Mechanics and Engineering
|
2020
|
Vol. 25, no. 1
142--158
EN
The effect of magnetic field dependent (MFD) viscosity on the thermal convection in a ferrofluid layer saturating a sparsely distributed porous medium has been investigated by using the Darcy-Brinkman model in the simultaneous presence of a uniform vertical magnetic field and a uniform vertical rotation. A correction is applied to the study of Vaidyanathan et al. [11] which is very important in order to predict the correct behavior of MFD viscosity. A linear stability analysis has been carried out for stationary modes and oscillatory modes separately. The critical wave number and critical Rayleigh number for the onset of instability, for the case of free boundaries, are determined numerically for sufficiently large values of the magnetic parameterM1 . Numerical results are obtained and are illustrated graphically. It is shown that magnetic field dependent viscosity has a destabilizing effect on the system for the case of stationary mode and a stabilizing effect for the case of oscillatory mode, whereas magnetization has a destabilizing effect.
13
Content available The complex Ginzburg Landau model for an oscillatory convection in a rotating fluid layer
Manjula S. H., Kiran P., Reddy P. Raj, Bhadauria B. S.
International Journal of Applied Mechanics and Engineering
|
2020
|
Vol. 25, no. 1
75--91
EN
A weakly nonlinear thermal instability is investigated under rotation speed modulation. Using the perturbation analysis, a nonlinear physical model is simplified to determine the convective amplitude for oscillatory mode. A non-autonomous complex Ginzburg-Landau equation for the finite amplitude of convection is derived based on a small perturbed parameter. The effect of rotation is found either to stabilize or destabilize the system. The Nusselt number is obtained numerically to present the results of heat transfer. It is found that modulation has a significant effect on heat transport for lower values of ωf while no effect for higher values. It is also found that modulation can be used alternately to control the heat transfer in the system. Further, oscillatory mode enhances heat transfer rather than stationary mode.
14
Content available Effect of convective heat and mass conditions in magnetohydrodynamic boundary layer flow with joule heating and thermal radiation
Sharma R. P., Tinker Seema, Gireesha B. J., Nagaraja B.
International Journal of Applied Mechanics and Engineering
|
2020
|
Vol. 25, no. 3
103--116
EN
A free convection viscous MHD flow over a semi-infinite vertical sheet with convective heat and mass conditions has been considered. The effects of thermal radiation, chemical reaction and Joule heating on flow are also accounted. The governing nonlinear partial differential equations have been transformed into a set of highly non-linear coupled ordinary differential equations (ODEs) using appropriate similarity transformations. Numerical solutions of transformed equations are obtained by employing the 5th order Runge-Kutta Fehlberg technique followed by the shooting technique. The influences of different flow parameters on the momentum, energy and mass field are discussed and shown graphically. Results reveal that temperature and concentration profiles enhance due to increasing heat and mass Biot number parameters.
15
Content available remote Impact of convection and stability parameters on lightning activity over Andhra Pradesh, India
Umakanth N., Satyanarayana G. Ch., Simon B., Kumar Prashant, Rao M. C.
Acta Geophysica
|
2020
|
Vol. 68, no. 6
1845--1866
EN
This paper brings out the interconnection of fash rate density (FRD) with convection and stability parameters over Andhra Pradesh (AP), India. The convection parameters include rainfall, relative humidity, specifc humidity, surface air temperature (SAT) and air temperature (at 850 mb). The stability parameters include convective available potential energy (CAPE), lifted index, K-index, total totals index (TTI), humidity index and total precipitable water. Both convective and stability parameters indicate good correlation with lightning activity. SAT and AT 850 mb have shown good correlations with lightning, which is a clear indication of interaction between warm air and dry air. CAPE and TTI have shown strong positive correlation with lightning activity. The correlation coefcient between FRD and CAPE is 0.81. We have also studied the infuence of convective and stability parameters during lightning and no lightning activity. Later, we also attempted the estimation of lightning activity by using artifcial neural network model. By using convection and stability parameters, six learning algorithms were used for training the artifcial neural network. Scaled conjugate gradient backpropagation training algorithm has given the better estimation, whereas resilient backpropagation training algorithm has shown the poor estimation of FRD.
16
Content available Numerical Analysis of the Influence of the Angle of Inclination of the Screen on the Intensity of Heat Exchange from a Flat Heat Exchanger in a Partially Limited Space
Orłowska Magdalena, Szkarowski Aleksander, Mamedov Shirali
Rocznik Ochrona Środowiska
|
2019
|
Tom 21, cz. 1
728--737
EN
The purpose of the work was to perform a numerical analysis enabling to learn the influence of the angle of inclination of a flat partition placed at the plate heat exchanger on the thermal efficiency of the device. It turns out that the inclination of the partition affects this efficiency. Selected systems allowed to capture these changes in the studied range and to visualize them graphically.
PL
Celem pracy było wykonanie analizy numerycznej umożliwiającej poznanie wpływu kąta pochylenia przegrody płaskiej umieszczonej przy płytowym wymienniku ciepła na wydajność cieplną urządzenia. Okazuje się, że pochylenie przegrody ma wpływ na tą wydajność. Wybrane układy pozwoliły uchwycić te zmiany w badanym zakresie i zobrazować graficznie.
17
Content available Electro-hydrodynamic convection in a rotating dielectric micropolar fluid layer
Kaur H., Verma G. N.
International Journal of Applied Mechanics and Engineering
|
2019
|
Vol. 24, no. 4
106--124
EN
Thermal convection of a rotating dielectric micropolar fluid layer under the action of an electric field and temperature gradient has been investigated. The dispersion relation has been derived using normal mode analysis. The effects of the electric Rayleigh number, micropolar viscosity, Taylor number and Prandtl number on stability and over stability criteria are discussed. It is found that rotation postpones the instability in the fluid layer, while the Prandtl number and rotation both have a stabilizing effect. It is also observed that the micropolar fluid additives have a stabilizing effect, whereas the electric field has a destabilizing effect on the onset of convection stability.
18
Content available Chaotic convection of viscoelastic fluid in porous medium under G-jitter
Bhadauria B. S., Singh A., Singh M. K.
International Journal of Applied Mechanics and Engineering
|
2019
|
Vol. 24, no. 1
37--51
EN
The present article aims at investigating the effect of gravity modulation on chaotic convection of a viscoelastic fluid in porous media. For this, the problem is reduced into Lorenz system (non-autonomous) by employing the truncated Galerkin expansion method. The system shows transitions from periodic to chaotic behavior on increasing the scaled Rayleigh number R. The amplitude of modulation advances the chaotic nature in the system while the frequency of modulation has a tendency to delay the chaotic behavior which is in good agreement with the results due to [1]. The behavior of the scaled relaxation and retardation parameter on the system is also studied. The phase portrait and time domain diagrams of the Lorenz system for suitable parameter values have been used to analyze the system.
19
Content available Badanie wpływu właściwości termicznych okna na pracę grzejnika w pomieszczeniu – badania numeryczne
Orłowska M.
Rocznik Ochrona Środowiska
|
2018
|
Tom 20, cz. 2
1699--1709
PL
Celem pracy było wykonanie badań numerycznych konwekcyjnej wymiany ciepła. Analizy numeryczne przeprowadzono w układzie dwuwymiarowym. Zrealizowano je przy użyciu nowoczesnego programu komputerowego Ansys Mechanical CFD-Flo. Wymiana ciepła dotyczyła pokojowego grzejnika płytowego, płaskiego umieszczonego na ścianie z oknem. Utworzono kilka wariantów obliczeń. Zadano pięć, różnych wartości współczynnika przejmowania ciepła α na oknie. Na podstawie przeprowadzonych badań można stwierdzić jakie są różnice wartości temperatury oraz prędkości powietrza przy różnych, zadanych wartościach strumienia ciepła na oknie oraz jak kształtuje się współczynnik przejmowania ciepła α, decydujący o intensywności wymiany ciepła.
EN
The purpose of the work was to perform numerical tests of convective heat exchange. Numerical analyzes were carried out in a two-dimensional system. They were realized using the modern Ansys Mechanical CFD-Flo computer program. The heat exchange concerned a room-mounted flat plate heater mounted on a wall with a window. Several calculation options have been created. Five different values of the heat transfer factor α on the window were given. On this basis of the conducted tests it is possible to determine the differences in temperature and air velocity at different values of the heat flux on the window and how the heat transfer coefficient α is determined which determines the intensity of heat exchange.
20
Content available Boundary layer analysis in nanofluid flow past a permeable moving wedge in presence of magnetic field by using Falkner – skan model
Ali M., Alim M. A.
International Journal of Applied Mechanics and Engineering
|
2018
|
Vol. 23, no. 4
1005--1013
EN
In the present work, the effect of various dimensionless parameters on the momentum, thermal and concentration boundary layer are analyzed. In this respect we have considered the MHD boundary layer flow of heat and transfer over a porous wedge surface in a nanofluid. The governing partial differential equations are converted into ordinary differential equations by using the similarity transformation. These ordinary differential equations are numerically solved using fourth order Runge–Kutta method along with shooting technique. The present results have been shown in a graphical and also in tabular form. The results indicate that the momentum boundary layer thickness reduces with increasing values of the pressure gradient parameter β for different situations and also for the magnetic parameter M but increases for the velocity ratio parameter λ and permeability parameter K*. The heat transfer rate increases for the pressure gradient parameter β, velocity ratio parameter λ, Brownian motion parameter Nb and Prandtl number Pr but opposite result is found for the increasing values of the thermoporesis parameter Nt. The nanoparticle concentration rate increases with an increase in the pressure gradient parameter β, velocity ratio parameter λ, Brownian motion parameter Nb and Lewis number Le, but decreases for the thermoporesis parameter Nt. Finally, the numerical results has compared with previously published studies and found to be in good agreement. So the validity of our results is ensured.
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