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1

The kinematic and thermodynamic environment during cloud-to-ground lightning occurrence in Poland

Sulik Sławomir, Taszarek Mateusz

Meteorology Hydrology and Water Management. Research and Operational Applications

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2024

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Vol. 12, Iss. 1

83--103

EN

This study identifies convective and kinematic parameters that positively influence elevated values of cloud-to-ground lightning flashes (CGs) in Poland. The analysis used data from the PERUN lightning detection and location system from IMGW-PIB and reanalyses of the ERA5 model from ECMWF for the period 2002-2020. In addition, a spatial-temporal distribution analysis was carried out for the period 1940-2022, covering the key parameters necessary for the appearance of convection. Results showed that thunderstorms most often occur in the summer, but also that there are increasingly favorable conditions for the appearance of organized multicellular systems in the spring. CG flashes most often form in a most-unstable convective available potential energy (MU CAPE) environment of about 1300 J/kg along with vertical wind shear (0-6 km AGL bulk wind shear) of 13-14 m/s. Using the WMAXSHEAR parameter, it was possible to conclude that overlapping CAPE and DLS values of about 500 m2/s2 imply increased electrical activity. At the same time, a high correlation with the Hail Size Index (HSI) parameter implies a positive relationship between the occurrence of hailstorms and an increased number of CGs generated in the case of supercells. The research also found a gradual increase in air temperature, MU CAPE, MU Mixing Ratio and the MU WMAXSHEAR parameter for the area under study.

2

Effect of outlet at the bottom of the drying chamber on the performance of natural convection solar dryers

Jamal Jamal, Djalal Muhammad Ruswandi

Przegląd Elektrotechniczny

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2023

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R. 99, nr 11

151--156

EN

In a closed room, the air gets more humid when the drying process takes place. The increase in air humidity causes the drying rate to decrease. The humidity in the drying chamber needs to be lowered. This study aims to increase the drying rate by keeping the air moist in the drying chamber. The research was conducted by making four outlets at the bottom of the drying chamber. The function of the outlet is to remove the moist air in the drying chamber. Removing moist air occurs by natural convection due to differences in density. This research was carried out in 3 variations. Namely, the outlet is fully closed, half-closed, and fully open. The research was carried out in Makassar, South Sulawesi, Indonesia. The dried material is bananas. The drying process is carried out from 09.00 to 17.00 WIB. The result of this research is that the solar dryer's performance increases when the hole at the bottom of the drying chamber is fully open. On the other hand, the solar dryer's performance decreases when the hole at the bottom of the drying chamber is fully closed.

PL

W zamkniętym pomieszczeniu powietrze staje się bardziej wilgotne podczas procesu suszenia. Wzrost wilgotności powietrza powoduje zmniejszenie szybkości suszenia. Należy obniżyć wilgotność w komorze suszenia. Badanie to ma na celu zwiększenie szybkości suszenia poprzez utrzymywanie wilgotności powietrza w komorze suszenia. Badania przeprowadzono wykonując cztery wyloty w dnie komory suszenia. Zadaniem wylotu jest usuwanie wilgotnego powietrza z komory suszenia. Usuwanie wilgotnego powietrza odbywa się na drodze naturalnej konwekcji z powodu różnic w gęstości. Badanie to przeprowadzono w 3 wariantach. Mianowicie, wylot jest całkowicie zamknięty, półprzymknięty i całkowicie otwarty. Badania przeprowadzono w Makassar w południowym Sulawesi w Indonezji. Suszony materiał to banany. Proces suszenia odbywa się w godzinach od 09.00 do 17.00 WIB. Wynikiem tych badań jest to, że wydajność suszarki słonecznej wzrasta, gdy otwór w dnie komory suszenia jest całkowicie otwarty. Z drugiej strony wydajność suszarki słonecznej spada, gdy otwór w dnie komory suszenia jest całkowicie zamknięty.

3

PV panel cooling using stack effect

Rao Kudithi Nageswara, Ganesamoorthy Rajkumar

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2023

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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.

4

Numerical Analysis of Convective Heat Transfer for Selected Geometric System

Orłowska Magdalena

Rocznik Ochrona Środowiska

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2022

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Tom 24

163--171

EN

The contemporary problems and issues of environmental protection refer to a large extent to problems related – generally speaking – to energy. Currently, the production processes mainly concern the combustion of energy fuels, transport – over long distances, and their use for utility purposes, e.g. engine drive or heating. These processes significantly negatively impact the environment and are magnified by their enormous intensity and size. While energy production and transport processes have been studied for many years, and their results are widely published, the issues related to the application and operation of heating devices are little known and require much observation and research. The operating indicators of heating devices are generally characterized by low values (natural convection), and their artificial increase (intensity) cannot be used due to the acoustic effects and additional (significant) investment costs. The article presents some research results on the intensification of heat flow – i.e. the thermal efficiency of flat heaters placed in a room with a specific temperature. Physical phenomena were investigated numerically by shaping the heat exchange space. The tested systems concerned a room with a free-standing heater, a heater with a vertical panel mounted in parallel, and a system with a curved bottom plate forming the so-called de Laval nozzle. Interesting results of air velocity and temperature fields and values of the heat transfer coefficient along the height of the heater were obtained. Based on the presented research, it can be concluded that the creation of convection surfaces around the heater is advisable because it affects the intensity of heat exchange, which can be increased without energy-intensive energy expenditure, i.e. in a non-mechanical way. Undoubtedly contributes positively to investment and operating costs, which is essential in environmental protection issues.

5

On the onset of thermal instability of a porous medium layer saturating a Jeffrey nanofluid

Rana Gian C., Gautam Poonam Kumari

Engineering Transactions

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2022

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Vol. 70, iss. 2

123--139

EN

The onset of stationary convection in thermal instability of porous layer saturating a Jeffrey nanofluid is studied. The behaviour of nanofluid is described by a Jeffrey fluid model and the porous layer is assumed to follow Darcy’s law. Due to the presence of the Jeffrey parameter and nanoparticles, the momentum-balance equation of fluid is modified. The linear stability analysis and normal modes analysis method are utilised to derive the dispersion relation for the Rayleigh number in terms of various parameters for free-free boundaries. The effects of the Jeffrey parameter, Lewis number, modified diffusivity ratio, nanoparticles’ Rayleigh number and medium porosity on the physical system are discussed analytically and graphically.

6

Numerical Investigation of Heat Transfer in Garment Air Gap

Zhang Yijie, Jia Juhong

Autex Research Journal

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2022

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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.

7

Positive solutions for nonlinear Robin problems with conviction

Gasiński Leszek, Papageorgiou Nikolaos S.

Science, Technology and Innovation

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2021

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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.

8

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.

9

Effects of rotation on Jeffrey nanofluid flow saturated by a porous medium

Rana Gian C.

Journal of Applied Mathematics and Computational Mechanics

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2021

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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.

10

The Investigation of Thermophysical Characteristics of Porous Insulation Materials Based on Burshtyn TPP Ash

Koshlak Hanna, Kaczan Anna

Rocznik Ochrona Środowiska

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2020

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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.

11

Experimental Research of Temperature Distribution on the Surface of the Front Plate, of a Flat Plate Heat Exchanger

Orłowska Magdalena

Rocznik Ochrona Środowiska

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2020

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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.

12

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

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2020

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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

13

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

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2020

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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.

14

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

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2020

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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.

15

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

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2020

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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.

16

Influence of microwave treatment on quality parameters of snacks food. Impact issues

Goszkiewicz Anna, Kochańska Ewa, Korczak Katarzyna, Potapov Volodymyr О., Prasol Svitlana

Acta Innovations

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2020

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no. 36

64--80

EN

The following publication presents results of the research on a new, innovative, mild technology of food processing with microwaves technology in order to develop novel food in the form of “on the go” healthy snacks. Different aspects of microwave treatment technologies within the context of physical model of electromagnetic field interaction with a food product, marketing and energy aspects were considered. Furthermore, comparison of sensory quality of conventionally and microwave treated nuts was shown, which is a key feature of nuts, seeds and dried fruits for most consumers. A comparative LCA analysis of convectional and microwave roasting was performed as well.

17

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

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2020

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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.

18

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

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2019

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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.

19

Electro-hydrodynamic convection in a rotating dielectric micropolar fluid layer

Kaur H., Verma G. N.

International Journal of Applied Mechanics and Engineering

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2019

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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.

20

Badanie wpływu właściwości termicznych okna na pracę grzejnika w pomieszczeniu – badania numeryczne

Orłowska M.

Rocznik Ochrona Środowiska

|

2018

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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.