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EN
In this study numerical solutions for magnetohydrodynamic transfer, thermal and mass instability, free convection flow through the plate before Casson fluid, heat dissipation, thermal radiation, heat sink, chemical reaction, tilt angle, and saturated porous medium were described. The effectiveness of this study is to analyze the effect of heat diffusion, Casson fluid, the angle of interest on the flow phenomenon of Cu-nanoparticles in the presence of thermal radiation, heat source/heat sink, destructive reaction, heat transfer and mass transfer in a simple way. The finite difference method was used to solve the governing equations which are the added partial differential equations. The effects of different material parameters on velocity, temperature and concentration profiles are explained using graphs and tables. The results are compared with previously published papers and a very good agreement is found. In the boundary layer region, fluid velocity decreases with the increasing values of magnetic field parameter, heat source/sink, Casson fluid, angle of inclination and thermal radiation parameter for Cu-nanoparticles. Also it is noticed that the solutal boundary layer thickness decreases with an increase in the chemical reaction parameter. It is because chemical molecular diffusivity reduces for higher values of Kr.
EN
In this work we have discussed the impact of thermal radiation on heat transfer to nanofluid flow over an unsteady permeable stretching sheet using various types of arbitrary shape nanoparticles of Copper (Cu), Silver (Ag), Alumina [...], and Titania Oxide [...] in the base fluid. Suitable transformations have been employed to build ODEs from the partial differential equations. Numerical results are therefore obtained particularly for cylindrical shape and spherical shape nanoparticles. Our analysis substantiates that the velocity and temperature profiles increases with enhanced thermal radiation parameter. Further, Nusselt number is more advanced for the nanofluid that contains cylindrical shape nanoparticles as compared to spherical shape nanoparticles.
EN
In this paper, a theoretical analysis has been made to study the effect of mixed convection MHD oscillatory Couette flow in a vertical parallel channel walls embedded in a porous medium in the presence of thermal radiation, chemical reaction and viscous dissipation. The channel walls are subjected to a constant suction velocity and free stream velocity is oscillating with time. The channel walls are embedded vertically in a porous medium. A magnetic field of uniform strength is applied normal to the vertical channel walls. The nonlinear and coupled partial differential equations are solved using multi parameter perturbation techniques. The effects of physical parameters, viz., the radiation absorption parameter, Prandtl number, Eckert number, dynamic viscosity, kinematic viscosity, permeability of porous medium, suction velocity, Schmidt number and chemical reaction parameter on flow variables viz., temperature, concentration and velocity profile have been studied. MATLAB code is used to analyze theoretical facts. The important results show that an increment in the radiation absorption parameter and permeability of porous medium results in an increment of the temperature profile. Moreover, an increment in the Prandtl number, Eckert number and dynamic viscosity results in a decrement of the temperature profile. An increment in suction velocity results in a decrement of the velocity profile. An increment in the Schmidt number, chemical reaction parameter and kinematic viscosity results in a decrement of the concentration profile.
EN
The impact of heat and mass transfer effects on an MHD flow past an inclined porous plate in the presence of a chemical reaction is investigated in this study. An effort has been made to explain the Soret effect and the influence of an angle of inclination on the flow field, in the presence of the heat source, chemical reaction and thermal radiation. The momentum, energy and concentration equations are derived as coupled second order partial differential equations. The model is non-dimensionalized and shown to be controlled by a number of dimensionless parameters. The resulting dimensionless partial differential equations can be solved by using a closed analytical method. Numerical results for pertaining parameters, such as the Soret number (Sr), Grashof number (Gr) for heat and mass transfer, the Schmidt number (Sc), Prandtl number (Pr), chemical reaction parameter (Kr), permeability parameter (K), magnetic parameter (M), skin friction (τ), Nusselt number (Nu) and Sherwood number (Sh) on the velocity, temperature and concentration profiles are presented graphically and discussed qualitatively.
EN
This paper focuses on the theoretical analysis of blood flow in the presence of thermal radiation and chemical reaction under the influence of time dependent magnetic field intensity. Unsteady non linear partial differential equations of blood flow consider time dependent stretching velocity, the energy equation also accounts time dependent temperature of vessel wall and the concentration equation includes the time dependent blood concentration. The governing non linear partial differential equations of motion, energy and concentration are converted into ordinary differential equations using similarity transformations solved numerically by applying ode45. The effect of physical parameters, viz., the permeability parameter, unsteadiness parameter, Prandtl number, Hartmann number, thermal radiation parameter, chemical reaction parameter and Schmidt number on flow variables, viz., velocity of blood flow in vessel, temperature and concentration of blood, has been analyzed and discussed graphically. From the simulation study the following important results are obtained: velocity of blood flow increases with the increment of both permeability and unsteadiness parameter. The temperature of blood increases at the vessel wall as the Prandtl number and Hartmann number increase. Concentration of blood decreases as time dependent chemical reaction parameter and Schmidt number increases.
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.
EN
A computational model is presented to explore the properties of heat source, chemically reacting radiative, viscous dissipative MHD flow of an incompressible viscous fluid past an upright cone under inhomogeneous mass flux. A numerical study has been carried out to explore the mass flux features with the help of Crank-Nicolson finite difference scheme. This investigation reveals the influence of distinct significant parameters and the obtained outputs for the transient momentum, temperature and concentration distribution near the boundary layer is discussed and portrayed graphically for the active parameters such as the Schmidt number Sc, thermal radiation Rd, viscous dissipation parameter […], chemical reaction parameter […], MHD parameter M and heat generation parameter ]…]. The significant effect of parameters on shear stress, heat and mass transfer rates are also illustrated.
9
Content available remote Application of Silica Aerogel in Composites Protecting Against Thermal Radiation
EN
Aerogels are characterized by excellent insulation properties and a good resistance to high and low temperatures. The objective of this study was to investigate the effects of silica aerogel on thermal properties of textile–polymer composites. Aerogel was applied in protective clothing fabric to improve its heat resistance. The composites were produced by coating a fabric made of meta-aramid (polyamide–imide) yarns with a dispersion of polychloroprene latex and synthetic resins or an acrylic–styrene dispersion with aerogel (100–700 μm particle size). The composites were subjected to thermal radiation (20 kW/m2) and their thermal properties were determined by thermogravimetry/derivative thermogravimetry (TG/DTG). Scanning electron microscopy/X-ray energy dispersive spectroscopy (SEM/EDS) was used to characterize the microstructure and study the elemental composition of materials. The thermal conductivity and resistance of composites were measured with an Alambeta apparatus. The tests indicated an increase in resistance to thermal radiation by approximately 15–25%. In TG/DTG analysis, the initial temperature for an unmodified fabric was 423.3°C. After modification, it decreased to 361.8° and 365.3°C for composites with 7 and 14% of aerogel, respectively. SEM images revealed a reduction in aerogel particle size.
EN
An analysis is presented to study the effects of thermal radiation, chemical reaction, viscous and Joule dissipation on MHD free convection flow between a pair of infinite vertical Couette channel walls embedded in a porous medium. The fluid flows by a strong transverse magnetic field imposed perpendicularly to the channel wall on the assumption of a small magnetic Reynolds number. The governing non linear partial differentia equations are transformed in to ordinary differential equations and are solved analytically. The effect of various parameters viz., Eckert number, electric conductivity, dynamic viscosity and strength of magnetic field on temperature profile has been discussed and presented graphically.
EN
An analysis was carried out for an unsteady magnetohydrodynamic (MHD) flow of a generalized third grade fluid between two parallel plates. The fluid flow is a result of the plate oscillating, moving and pressure gradient. Three flow problems were investigated, namely: Couette, Poiseuille and Couette-Poiseuille flows and a number of nonlinear partial differential equations were obtained which were solved using the He-Laplace method. Expressions for the velocity field, temperature and concentration fields were given for each case and finally, effects of physical parameters on the fluid motion, temperature and concentration were plotted and discussed. It is found that an increase in the thermal radiation parameter increases the temperature of the fluid and hence reduces the viscosity of the fluid while the concentration of the fluid reduces as the chemical reaction parameter increases.
EN
An investigation has been carried out for the MHD 3-dimensional flow of nanofluid over a shrinking sweet saturating a porous media in the presence of thermal radiation and heat generation. Convective boundary conditions for the flow phenomena are used in the present analysis. The governing equations are reduced to ODEs employing suitable similarity transformations. The solutions of formulated differential equations have been attained mathematically by fourth order R-K technique along with the shooting method. The impact of the governing constraints on momentum, heat, and local Nusselt number, are explored. It is noticed that the momentum and heat decrease with raise in the porosity variable, temperature reduces with an enhance in the thermal radiation variable, and temperature enhances with an enhance in the heat source/sink parameter.
EN
MHD slip flow past an extending surface with third type (convective) boundary condition and thermal radiation is analysed. The governing momentum and energy equations are converted into set of nonlinear ordinary differential equations using appropriate similarity transformations. The Fourth-Order Runge-Kutta shooting method is applied for obtaining the numerical solution of the resulting nonlinear ordinary differentia equations. The numerical results for velocity and temperature distribution are found for different values of the vital parameters, namely: the magnetic interaction factor, slip factor, convective factor, Prandtl number and radiation factor and are presented graphically, and discussed.
PL
W artykule omówiono warunki wykonywania pomiarów za pomocą kamery termowizyjnej. Zwrócona została uwaga na stosowane przetworniki pomiarowe i dobór układów optycznych w zależności od odległości od badanego obiektu. Na przykładach pokazane zostały wybrane wady (defekty) instalacji elektrycznej, które mogą być wykryte przy zastosowaniu kamery termowizyjnej.
EN
The article discusses the conditions for measurement using a thermal imaging camera. Attention will be paid to the used and their parameters. It will discuss about the measuring transducers and the selection of optical systems depending on the distance from the test object.
EN
This paper presents the results of preliminary assessment of radiative heat flux received by selected windows from tar paper coated flat roof of the adjacent building. This study was conducted on an actual object: building “P” at the University of Technology in Rzeszow. Windows located on south-western elevation of “P” building are subjected to thermal and diffused solar radiation, coming from a flat roof of a nearby gym. It was suspected, that this extra heat flux may have significant influence on compartment overheating, that is observed by occupants of “P” building. For the purpose of this study, various atmospheric data, such as temperatures, solar irradiance and wind speed were collected on site. In order to gain more detailed insight into investigated problem, Finite Elements model of occurring phenomenon was developed. FE modelling along with calculations of necessary view factors were performed in Matlab 2019a. Our study demonstrated, that analysed windows receive twice the heat gains from the flat roof, that they would have received from grass covered ground surface in absence of the gym. It has been concluded, that the proximity of the flat roof with bituminous cover considerably influences radiative heat gains of the windows, especially these located at lower floors and the phenomenon seriously contributes to overheating of the compartments in studied building.
EN
This study examined the heat storage and release characteristics of ZrC-imbedded woven fabrics by light emission and thermal manikin experiments. The surface temperature of the ZrC-imbedded fabric was higher than that of the regular PET fabric. Furthermore, the Clo values of both the total and torso of the ZrC-imbedded fabric by the thermal manikin experiment were higher than those of the regular PET fabric, which suggests that the heat release is caused by far infrared rays emitted from the ZrC particles imbedded in the yarns as they receive light. This was confirmed by the higher emissivity and emissive power of the ZrC-imbedded fabric. However, the tactile hand of the ZrC-imbedded fabric needs to be improved by adjusting the structural parameters of the fabric and finishing process factors.
EN
The presence of more than one solute diffused in fluid mixtures is very often requested for discussing the natural phenomena such as transportation of contaminants, underground water, acid rain and so on. In the paper, the effect of nonlinear thermal radiation on triple diffusive convective boundary layer flow of Casson nanofluid along a horizontal plate is theoretically investigated. Similarity transformations are utilized to reduce the governing partial differential equations into a set of nonlinear ordinary differential equations. The reduced equations are numerically solved using Runge-Kutta-Fehlberg fourth-fifth order method along with shooting technique. The impact of several existing physical parameters on velocity, temperature, solutal and nanofluid concentration profiles are analyzed through graphs and tables in detail. It is found that, modified Dufour parameter and Dufour solutal Lewis number enhances the temperature and solutal concentration profiles respectively.
PL
W artykule przedstawiono ogólną charakterystykę aerożeli, ze zwróceniem uwagi na ich bardzo dobre właściwości izolacyjne w porównaniu z innymi materiałami. Wskazano zarówno zalety, jak i wady aerożeli. Przybliżono główne czynniki gorące występujące na stanowiskach pracy jak płomień, promieniowanie cieplne, rozpryski płynnego metalu, kontakt z gorącym przedmiotem i łuk elektryczny. Czynniki gorące sklasyfikowano jako czynniki szkodliwe wpływające na powstawanie mikroklimatu gorącego, na który narażeni są pracownicy instalacji przemysłowych, zajmujący się przerobem metali i stali, pracownicy odlewni szkła i ceramiki, pracownicy przemysłu spożywczego (piekarnie) oraz strażacy i spawacze. Omówiono przykłady zastosowania aerożeli w materiałach włókienniczych wykorzystywanych do ochrony przed czynnikami gorącymi. Dokonano analizy literatury pod kątem możliwości aplikacji aerożeli do włóknin i tkanin. Zamieszczono wybrane metody otrzymywania materiałów kompozytowych, najczęściej z udziałem aerożelu krzemionkowego o hydrofobowej powierzchni. Zwrócono uwagę na trwałość właściwości aerożelu po działaniu czynnika gorącego.
EN
The paper discusses the general characteristics of aerogels, with paying attention to very good insulation properties compared to other materials. Both the advantages and the disadvantages of aerogels were highlighted. The main heat factors occuring at workstations, such as a flame, thermal radiation, liquid metal splashes, contact with hot object and arcs, were approximated. Heat factors were classified as hazardous agents that affect the formation of hot microclimates, to which industrial workers, metal and steel workers, glass and ceramics workers, food service workers (bakeries) as well as firefighters and welders were exposed. Examples of aerogels used in textile materials for the protection against heat agents were discussed. Literature was analyzed for potential applications of aerogels to nonwovens and fabrics. Selected methods of obtaining composite materials, most commonly with silica aerogels with the hydrophobic surface. Attention was paid to the durability of aerogels properties after heat treatment with.
PL
Stopy z pamięcią kształtu (SMA) stanowią grupę materiałów inteligentnych, które pod wpływem bodźca temperaturowego są zdolne do samoistnej i odwracalnej zmiany swojego kształtu. W niniejszej publikacji przedstawiono podstawowe założenia materiałowe i konstrukcyjne dla aktywnej odzieży ochronnej z elementami SMA, przeznaczonej do ochrony przed czynnikami gorącymi i płomieniem. Implementacja odpowiednio przygotowanych stopów z pamięcią kształtu do odzieży pozwoli na aktywne dostosowanie jej poziomu ochrony do istniejącego zagrożenia, bez konieczności stosowania grubych, ciężkich układów materiałów. Odzież ta może stanowić zatem alternatywę dla obecnie stosowanej odzieży ochronnej, która przeważnie jest ciężka, wykonana na całej powierzchni z układów materiałów zapewniających jednakowy, wysoki poziom ochrony.
EN
Shape memory alloys (SMA) are a group of intelligent materials that are capable to self-contained and reversible change of shape under the influence of temperature impulse. This publication presents the basic material and constructional assumptions for the active protective clothing with SMA elements, destined to protect against heat and flame.The implementation of suitably prepared shape memory alloys for clothing will allow for an active adaptation of its protection level to the existing threat, without the need of using the thick, heavy material sets. Therefore, this clothing can be an alternative to the currently used protective clothing, which is usually a heavy, overall made of material sets that provides a uniform, high level of protection.
20
Content available remote Promieniowanie w zamknięciach przeciwpożarowych
PL
W artykule omówiono problematykę bram przeciwpożarowych charakteryzujących się klasą odporności ogniowej EW. Przedstawiono podstawowe różnice w poziomie promieniowania oraz ich wpływ na człowieka. Zasugerowano potrzebę przeprowadzenia zmian w przepisach prawnych.
EN
The paper discusses the issue of gates characterized by EW fire resistance class. Basic differences in the level of radiation and their impact on humans are presented. The need for changes in legal regulations was suggested.
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