Journal articles on the topic 'Effective heat-conducting'
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Peng, Yang, Yun Mou, Tao Wang, Hao Wang, Renli Liang, Xinzhong Wang, Mingxiang Chen, and Xiaobing Luo. "Effective Heat Dissipation of QD-Based WLEDs by Stacking QD Film on Heat-Conducting Phosphor-Sapphire Composite." IEEE Transactions on Electron Devices 66, no. 6 (June 2019): 2637–42. http://dx.doi.org/10.1109/ted.2019.2907700.
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Chumak, Kostyantyn. "The thermoelastic contact problem for wavy surfaces with a heat-conducting medium in interface gaps." Mathematics and Mechanics of Solids 23, no. 10 (August 25, 2017): 1389–406. http://dx.doi.org/10.1177/1081286517726369.
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This paper presents a study on the thermoelastic contact between a wavy surface and a flat surface in the presence of a heat-conducting interstitial medium in interface gaps. The influence of applied mechanical and thermal loads on the deformation of the gaps is taken into account. The contact problem is reduced to a system of singular integro-differential equations for a temperature jump across the gaps and the height of the gaps. Solutions are obtained for the cases of thermoinsulated and heat-conducting gaps. It is shown that, in contrast to the thermoinsulated gap model, the use of the heat-conducting gap model makes it possible to construct a physically correct solution of the contact problem. It is revealed that the wavy interface with heat-conducting gaps exhibits thermal rectification. The effects of the medium’s thermal conductivity, the pressure and heat flow magnitudes and the waviness amplitude on the effective thermal contact resistance and the level of thermal rectification are analysed.
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Shchipacheva, E. V., and M. K. Turdalieva. "ACCOUNTING FOR SPECIFIC HEAT LOSSES THROUGH HEAT-CONDUCTING INCLUSIONS AS AN EFFECTIVE WAY TO DETERMINE THE HEAT-PROTECTIVE PROPERTIES OF BUILDING ENCLOSING STRUCTURES." Theoretical & Applied Science 106, no. 02 (February 28, 2022): 545–52. http://dx.doi.org/10.15863/tas.2022.02.106.54.
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Vėjelienė, Jolanta. "PROCESSED STRAW AS EFFECTIVE THERMAL INSULATION FOR BUILDING ENVELOPE CONSTRUCTIONS." Engineering Structures and Technologies 4, no. 3 (October 4, 2012): 96–103. http://dx.doi.org/10.3846/2029882x.2012.730286.
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The efficiency of thermal insulation materials obtained from renewable resources depends on the possibilities of reducing thermal transfer via solid and gaseous conduction, thermal radiation and, in some cases, convection. The heat transfer mechanism for thermal insulation materials mostly depends on the structure and density of the material used. Efficient thermal insulation materials consist of a gaseous phase and a solid skeleton. Gas content in such materials can take more than 99% of material by volume. In this case, thermal transfer via solid conductivity is negligible. The current work analyses the possibilities of reducing heat transfer in the straw of a varying structure. For conducting experiments, barley straw was used. To evaluate the impact of straw stalk orientation in a specimen on thermal conductivity, strongly horizontally and vertically oriented specimens of straw stalks were prepared. To reduce heat transfer via gaseous conduction and convection in large cavities in straw stalks and between stalks, barley straw were chopped and defibered. In order to decrease heat transfer via radiation after thermal conductivity measurements, mechanically processed straw were coated with infrared absorbers. Due to thermal conductivity measurements of chopped and defibered straw, an optimal amount of infrared absorbers were determined.
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Manners, W. "Heat conduction through irregularly spaced plane strip contacts." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 214, no. 8 (August 1, 2000): 1049–57. http://dx.doi.org/10.1243/0954406001523515.
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Solutions are developed for the conductive heat flow in the xy plane where there is a uniform flow at infinite values of y, and where y = 0 represents the interface between two materials. This interface consists of an arbitrary pattern of perfectly conducting strips and non-conducting gaps. It is assumed that thermoelastic effects are negligible. The solution takes the form of an equation with one unknown parameter per gap, and these unknowns can be found by a simple solution process involving numerical integration. The effective resistance of the interface can then be determined by a simple numerical integration.
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Sydorets, Volodymyr, Andrey Dubko, and Volodymyr Korzhyk. "Study on the Resistive Heat Source in a Two-Phase Medium at High-Frequency Electrosurgical Intervention." Applied Mechanics and Materials 873 (November 2017): 140–44. http://dx.doi.org/10.4028/www.scientific.net/amm.873.140.
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Numerical analysis of distribution of resistive heat source in two-phase conducting medium (copper electrode – biological tissue) was carried out. Axisymmetric two-dimensional elliptic problem, with boundary conditions of the first and second kind was solved in the environment of MATLAB mathematical package, using the method of finite differences. Analysis results show that heat source concentration and other parameters are determined by skin effect. This fact should be taken into account in development of new effective methods of surgical treatment and respective instruments. This mathematical model can be applied in a wide frequency range for conducting materials with different conductivities.
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Romenski, E., I. Peshkov, M. Dumbser, and F. Fambri. "A new continuum model for general relativistic viscous heat-conducting media." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2170 (March 30, 2020): 20190175. http://dx.doi.org/10.1098/rsta.2019.0175.
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The lack of formulation of macroscopic equations for irreversible dynamics of viscous heat-conducting media compatible with the causality principle of Einstein’s special relativity and the Euler–Lagrange structure of general relativity is a long-lasting problem. In this paper, we propose a possible solution to this problem in the framework of SHTC equations. The approach does not rely on postulates of equilibrium irreversible thermodynamics but treats irreversible processes from the non-equilibrium point of view. Thus, each transfer process is characterized by a characteristic velocity of perturbation propagation in the non-equilibrium state, as well as by an intrinsic time/length scale of the dissipative dynamics. The resulting system of governing equations is formulated as a first-order system of hyperbolic equations with relaxation-type irreversible terms. Via a formal asymptotic analysis, we demonstrate that classical transport coefficients such as viscosity, heat conductivity, etc., are recovered in leading terms of our theory as effective transport coefficients. Some numerical examples are presented in order to demonstrate the viability of the approach. This article is part of the theme issue ‘Fundamental aspects of nonequilibrium thermodynamics’.
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Nasrin, Rehena. "Influence of centered conducting obstacle on MHD combined convection in a wavy chamber." Journal of Naval Architecture and Marine Engineering 8, no. 2 (November 22, 2011): 93–104. http://dx.doi.org/10.3329/jname.v8i2.7392.
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The development of centered heat conducting obstacle effect on combined magnetoconvective flow in a lid driven chamber has been numerically studied. The enclosure considered has rectangular horizontal lower surfaces and vertical side surfaces. The lower and upper surfaces are insulated. The left wall is mechanically lid driven having uniform temperature Ti and velocity v0 while other vertical side is wavy and maintains higher temperature Th than the lid. The governing two-dimensional flow equations have been solved by using Galerkin weighted residual finite element technique. The investigations are conducted for different values of Richardson number (Ri) and physical parameter i.e. diameter (D) of square solid body. Various characteristics such as streamlines, isotherms and heat transfer rate in terms of the mean Nusselt number (Nu), the average temperature (?av) of the fluid and temperature of obstacle center (?c) are presented. The results indicate that the mentioned parameters strongly affect the flow phenomenon and temperature field inside the chamber. Conducting largest obstacle is preferable for effective heat transfer mechanism in presence of magnetic field.Keywords: Combined convection, MHD, wavy chamber, heat conducting obstacle, finite element simulation.doi: http://dx.doi.org/10.3329/jname.v8i2.7392 Journal of Naval Architecture and Marine Engineering 8(2011) 93-104
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Bauwens, Luc. "Oscillating flow of a heat-conducting fluid in a narrow tube." Journal of Fluid Mechanics 324 (October 10, 1996): 135–61. http://dx.doi.org/10.1017/s0022112096007860.
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Thermoacoustic refrigeration occurs in periodic flow in a duct with heat transfer within the fluid and to the tube. This study considers the periodic limit cycle with large pressure oscillations that is obtained in a tube when prescribed, phase-shifted, periodic velocities at the tube ends, at frequencies lower than acoustic eigenmodes, sweep a length comparable to the tube length. The temperature differences between the two ends are of arbitrary magnitude, heat transfer in the transverse direction within the fluid is assumed to be very effective and the thermal mass of the wall is large. The geometry is two-dimensional, axisymmetric, and conduction is accounted for, not only in the fluid, but also with and within the tube wall. A perturbation solution valid in a local near-isothermal limit determines the equilibrium longitudinal temperature profile that is reached at the periodic regime, the pressure field including longitudinal gradients, and the longitudinal enthalpy flux. Results are presented for tubes open at both ends and also with one end closed. In the latter case, a singularity occurs in the temperature at the closed end, with behaviour identical to Rott's result for acoustic flow with small pressure amplitude. Other new results obtained for tubes open at both ends show that when velocities at both ends are in opposite phase, internal singularities in the temperature profiles may occur.
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Zhong, Zhong, Yuan Sun, Xiu-Qun Yang, Weidong Guo, and Haishan Chen. "A Sensitivity Study of an Effective Aerodynamic Parameter Scheme in Simulating Land–Atmosphere Interaction for a Sea–Land Breeze Case Around the Bohai Gulf of China." Journal of Hydrometeorology 18, no. 8 (July 18, 2017): 2101–15. http://dx.doi.org/10.1175/jhm-d-16-0184.1.
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Abstract Numerical simulations of the atmospheric boundary layer require careful representation of the surface heterogeneity, which involves the upscaling parameterization scheme for the heterogeneous surface parameters. In this study, the sensitivity comparisons of an effective aerodynamic parameter scheme against the area-weighted average scheme in simulating the land–atmosphere interaction over heterogeneous terrain were carried out by conducting multinested simulations with the Weather Research and Forecasting (WRF) Model at coarse and fine resolutions, for a typical sea–land breeze case in the Bohai Gulf of China. The results show that the limited-area model is sensitive to the aerodynamic parameter scheme and the effective aerodynamic parameter scheme exhibits a better performance in simulating the variables and parameters in the land–atmosphere interaction process, such as surface wind speed, sensible heat flux, latent heat flux, friction velocity, and surface air temperature, among others, for short-term simulations. Particularly, the underestimation of sensible heat flux and overestimation of latent heat flux over heterogeneous terrain with area-weighted average scheme for aerodynamic parameters can be improved with the effective parameter scheme in the coastal regions, where the mean simulation error with the effective parameter scheme is about one-half of that with the average scheme for sensible heat flux and one-third for latent heat flux.
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Morimoto, Hideyuki, Kazuhiko Takeno, Tsuyoshi Takahashi, Kensaku Hayashi, and Shinichi Tobishima. "High-Rate Charge-Discharge Performance of Composite Electrodes of FeOOH-Based Amorphous Particles and Carbon Powder." Key Engineering Materials 388 (September 2008): 33–36. http://dx.doi.org/10.4028/www.scientific.net/kem.388.33.
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Composite electrode materials of amorphous FeOOH-based particles and carbon powder were prepared by heat treatment of composite powder obtained by hydrolyzing of mixed aqueous solutions of FeCl3 and Ti(SO4)2 into which electron conducting carbon powder was dispersed. They exhibited high capacities over 150 mAh g-1 and good cycle performance at large charge-discharge current density of 5 mA cm-2 (ca. 1 A g-1). In this case, the heat treatment was effective process to improve the cycle performance.
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Makinde, Oluwole Daniel, Naramgari Sandeep, Isaac Lare Animasaun, and M. S. Tshehla. "Numerical Exploration of Cattaneo-Christov Heat Flux and Mass Transfer in Magnetohydrodynamic Flow over Various Geometries." Defect and Diffusion Forum 374 (April 2017): 67–82. http://dx.doi.org/10.4028/www.scientific.net/ddf.374.67.
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The flow geometry plays a major role in heat and mass transfer processes of many engineering and industrial applications.In the present paper, we examined the combined effects of Cattaneo-Christov heat flux, external magnetic field, chemical reaction, heat source and buoyancy forces on the flow of an incompressible electrically conducting fluid with heat and mass transfer over three different geometries (cone, wedge and a plate). The nonlinear governing equations are obtained and tackled numerically using shooting technique with Runge-Kutta-Felhberg integration scheme. Numerical results are presented graphically and discussed quantitatively. It is found that the thermal boundary layer is highly effective on the flow over a wedge when compared with the other two geometries (plate and a cone).
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Ding, Yuzhang, Minxiang Wei, and Rui Liu. "Parameters of liquid cooling thermal management system effect on the Li-ion battery temperature distribution." Thermal Science, no. 00 (2021): 223. http://dx.doi.org/10.2298/tsci201019223d.
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In order to investigated the influence on the liquid cooling system cooling effect by changing the structural parameters, single Li-ion battery heat generation model is conducted, and used in following simulation. Subsequently, sixteen models are designed by orthogonal array, and the results are obtained by extremum difference analysis, which can quantify the influence degree, identify major and minor factors, and find the relatively optimum combination. Finally, different channel entrance layout is adopted to investigated. With a series of work, the effective of single battery heat generation model is proved by the discharge experiment. The coolant velocity has most evident influence on the Li-ion battery temperature rise, rectangular channel aspect ratio is second one, and the heat conducting plate thickness has the smallest influence. Similarly, for Li-ion battery temperature difference, the effect of heat conducting plate thickness and rectangular channel aspect ratio as the same, both are secondary factor, and coolant velocity is main factor. With different channel entrance layout, both the maximum temperatures denote a same upward trend, and better balance temperature distribution is obtained by adopt Case C system which with alternating arrange channel entrance layout.
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Belous, A. N., M. V. Overchenko, and O. E. Belous. "PORTABLE HEAT METERING SYSTEM DESIGN." Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 22, no. 1 (February 27, 2020): 140–51. http://dx.doi.org/10.31675/1607-1859-2020-22-1-140-151.
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In modern construction practice, more than half of buildings in operation require modernization of thermal insulation. However, in order to select an effective insulation system, it is necessary to know the actual thermal and technical characteristics of structures and parameters of the building internal environment. The paper analyzes methods and equipment for evaluation of the thermal performance of outdoor enclosures. The advantages and disadvantages of the main devices recommended by the regulatory documents for field research are shown. According to the data obtained, a heat engineering complex is developed for conducting field studies of heat and humidity of wall structures and microclimate of building premises. Software improvement together with Arduino reader device allow monitoring both at stationary and non-stationary thermal conditions of external enclosures and indoor climate parameters in field conditions.
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Fialko, N., R. Dinzhos, V. Prokopov, Ju Sherenkovsky, and N. Meranova. "Creation of low-thermal-conductivity polymer nanocomposites for internal gas vents of boiler chimneys." Energy and automation, no. 5(51) (October 28, 2020): 57–68. http://dx.doi.org/10.31548/energiya2020.05.057.
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Methods and results of experimental studies of thermophysical, structural and mechanical properties of low-heat-conducting polymer nanocomposites, oriented to use for gas ducts and chimneys of boiler installations, as well as various other gas and water communications are presented. In this work, on the basis of the performed set of methodological studies regarding the analysis of the legitimacy of using different models of heat conductivity for predicting the heat-conducting properties of these composites, the possibility of using for this prediction a number of models of the theory of the effective medium and the theory of percolation is considered. The analysis of thermophysical properties, structural characteristics and Young's modulus of low-heat-conductivity polymer nanocomposites based on polyethylene and polypropylene is carried out. Using these nanocomposites as an example, the achievement of a significant increase in their Young's modulus in comparison with unfilled polymers with a relatively small increase in heat conductivity is demonstrated. To obtain nanocomposites, we used a method based on mixing the components in a polymer melt using an extruder and then shaping the composite into the required shape by hot pressing. The method of differential scanning calorimetry was used to determine Young's modulus. On the basis of the studies carried out, the possibility of obtaining low-heat-conducting polymer nanocomposites with improved mechanical characteristics has been shown. In particular, it was shown that for nanocomposites based on polyethylene or polypropylene filled with CNTs (carbon nanotubes) or nanodispersed aerosil particles, with a mass fraction of the latter up to 2%, the following takes place a relatively insignificant increase in heat conductivity coefficients and a significant increase in the modulus of elasticity in tension. The research data also made it possible to obtain for the developed nanocomposites the temperature dependences of their specific mass heat capacity and, on this basis, to analyze the regularities of changes in the structural characteristics of these materials.
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Nadimuthu, Lalith, Divya Selvaraj, and Kirubakaran Victor. "Simulation and experimental study on performance analysis of solar photovoltaic integrated thermoelectric cooler using MATLAB Simulink." Thermal Science 26, no. 2 Part A (2022): 999–1007. http://dx.doi.org/10.2298/tsci201211301n.
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The present study investigates the performance of solar photovoltaic integrated thermoelectric cooler using MATLAB Simulink. The enhancement of efficiency has been achieved using an effective heat removal mechanism from the hot side heat sink. Since the hot side temperature is a crucial parameter. The intrinsic material properties like Seebeck coefficient, ?, thermal conductance, K, and electrical resistance, R, of the thermoelectric module are carefully estimated using analytical method and reported. The MATLAB Simulink Peltier module is developed based on the estimated intrinsic properties. The effect of system voltage (V) and current (A) on the thermal parameters like cooling capacity, QC, and coefficient of performance has been investigated. The simulation study is validated by conducting a series of experimental analysis. The experimental model is equipped with a 100 Wp polycrystalline solar photovoltaic module to integrate and power the 12V/5A of the 60 W thermoelectric cooler. Moreover, the results reveal that there is a significant effect of ambient and hot side temperature on the thermoelectric cooler performance. The fin-type conductive mode of heat transfer mechanism is adopted along with the convective forced air-cooling system to achieve effective heat removal from the hot side. The infrared thermographic investigation is carried out for ascertaining effective heat removal.
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Chetverushkin, B. N., A. V. Saveliev, and V. I. Saveliev. "Kinetic algorithms for the modeling of conductive fluids flow on high performance computational systems." Доклады Академии наук 489, no. 6 (December 23, 2019): 552–57. http://dx.doi.org/10.31857/s0869-56524896552-557.
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This letter presents the results of the mathematical modeling of processes of electrically conducting fluid flow dynamics for complex heat transfer systems. The study was carried out based on detailed calculations on parallel high performance computational systems on the basis of the kinetically consistent magnetogasdynamic approach, adjusted for this class of problems. The kinetically consistent algorithm adapts well to the architecture of high performance computational systems with massive parallelism and makes it possible to conduct effective research of complex heat transfer systems with high resolution. The article presents the approach, method and algorithms as well as the results of the mathematical modeling.
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Krymov, Nikita E. "Estimating the Discrete Approximation Error in Solving the Stationary Radiant-and-Conduction Heat Transfer Problem in a System of Absolutely Black Square Rods." Vestnik MEI, no. 5 (2021): 128–34. http://dx.doi.org/10.24160/1993-6982-2021-5-128-134.
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Studying heat transfer processes in periodic media containing vacuum interlayers or cavities, heat through which is transferred by radiation, is of significant interest for applications. Direct numerical solution of such problems involves considerable computational efforts and becomes almost impossible for systems containing a large number of heat conducting elements, especially for 2D and 3D structures. Therefore, it is of issue to develop effective approximate solution methods for such problems. This publication continues a series of studies on developing and substantiating special discrete and asymptotic approximations of radiant-and-conduction heat transfer problems in periodic systems of heat conducting elements separated by vacuum. In this study, the stationary radiant-and-conduction heat transfer problem in a system of absolutely black square rods is considered. The sought quantity is the absolute temperature, which is found from the solution of the boundary-value problem for the stationary heat conduction equation with nonlinear nonlocal boundary conditions describing radiant heat transfer between the rods through vacuum interlayers. A special discrete approximation of this problem leading to the system of linear algebraic equations with respect to the fourth power of the temperature is presented. The solution of this system as approximation of the mean temperature over the rod cross-section is described. The discrete approximation error estimate as a function of the square rod side length (the small parameter of the problem) and the thermal conductivity coefficient has been obtained. The obtained error estimate proves applicability of the discrete approximation for materials with a high thermal conductivity coefficient.
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Brazhanova, Dana, Vyacheslav Stoyak, Madina Ibragimova, and Angel Terziev. "Methodology for determination of heat losses from infiltration and ventilation and heat gains from people in overall energy balance of the building." E3S Web of Conferences 207 (2020): 01007. http://dx.doi.org/10.1051/e3sconf/202020701007.
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This paper proposes a new methodology of determining the building heat losses associated with natural and (or) forced air ventilation, based on continuous measurements of the temperature, humidity and carbon dioxide concentration in the air. Determining the flow rate of infiltrating air is performed by the active and passive experimental methods. The proposed method allows determining the exact amount of heat losses associated with ventilation or infiltration of the building under environmental conditions. In addition, the paper proposes an algorithm of calculating the actual number of people present in the room and the associated heat gains based on the air composition analysis. The proposed methods can be used as tools for conducting energy inspections of buildings and structures, as well as be part of effective building energy supply management systems.
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Bulíček, Miroslav, Ansgar Jüngel, Milan Pokorný, and Nicola Zamponi. "Existence analysis of a stationary compressible fluid model for heat-conducting and chemically reacting mixtures." Journal of Mathematical Physics 63, no. 5 (May 1, 2022): 051501. http://dx.doi.org/10.1063/5.0041053.
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The existence of large-data weak solutions to a steady compressible Navier–Stokes–Fourier system for chemically reacting fluid mixtures is proved. General free energies are considered satisfying some structural assumptions, with a pressure containing a γ-power law. The model is thermodynamically consistent and contains the Maxwell–Stefan cross-diffusion equations in the Fick–Onsager form as a special case. Compared to previous works, a very general model class is analyzed, including cross-diffusion effects, temperature gradients, compressible fluids, and different molar masses. A priori estimates are derived from the entropy balance and the total energy balance. The compactness for the total mass density follows from an estimate for the pressure in L p with p > 1, the effective viscous flux identity, and uniform bounds related to Feireisl’s oscillation defect measure. These bounds rely heavily on the convexity of the free energy and the strong convergence of the relative chemical potentials.
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Sheremet, Mikhail, Hakan Oztop, Dmitriy Gvozdyakov, and Mohamed Ali. "Impacts of Heat-Conducting Solid Wall and Heat-Generating Element on Free Convection of Al2O3/H2O Nanofluid in a Cavity with Open Border." Energies 11, no. 12 (December 7, 2018): 3434. http://dx.doi.org/10.3390/en11123434.
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Development of modern electronic devices demands a creation of effective cooling systems in the form of active or passive nature. More optimal technique for an origination of such cooling arrangement is a mathematical simulation taking into account the major physical processes which define the considered phenomena. Thermogravitational convection in a partially open alumina-water nanoliquid region under the impacts of constant heat generation element and heat-conducting solid wall is analyzed numerically. A solid heat-conducting wall is a left vertical wall cooled from outside, while a local solid element is placed on the base and kept at constant volumetric heat generation. The right border is supposed to be partially open in order to cool the local heater. The considered domain of interest is an electronic cabinet, while the heat-generating element is an electronic chip. Partial differential equations of mathematical physics formulated in non-primitive variables are worked out by the second order finite difference method. Influences of the Rayleigh number, heat-transfer capacity ratio, location of the local heater and nanoparticles volume fraction on liquid circulation and thermal transmission are investigated. It was ascertained that an inclusion of nanosized alumina particles to the base liquid can lead to the average heater temperature decreasing, that depends on the heater location and internal volumetric heat generation. Therefore, an inclusion of nanoparticles inside the host liquid can essentially intensify the heat removal from the heater that is the major challenge in different engineering applications. Moreover, an effect of nanosized alumina particles is more essential in the case of low intensive convective flow and when the heater is placed near the cooling wall.
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Ueda, Y., K. Nakacho, and T. Shimizu. "Improvement of Residual Stresses of Circumferential Joint of Pipe by Heat-Sink Welding." Journal of Pressure Vessel Technology 108, no. 1 (February 1, 1986): 14–23. http://dx.doi.org/10.1115/1.3264746.
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Intergranular stress corrosion cracking may occur in some specific conditions on the inner surface of the welded joints of stainless steel pipes which are furnished in nuclear plants. One of the remedies for this cracking is to convert welding residual stress on this surface into compression. In this research, in order to improve welding residual stress, the authors investigated the effectiveness of the heat-sink welding (water cooling) by conducting theoretical analyses and experiments on SUS 304 pipes of different sizes in comparison with the conventional welding. The mechanisms of production of residual stresses by both methods are clarified and conditions for effective application of the heat-sink welding such as limitation of heat input, procedure of welding are indicated.
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Sołoducho, Jadwiga, Dorota Zając, Kamila Spychalska, Sylwia Baluta, and Joanna Cabaj. "Conducting Silicone-Based Polymers and Their Application." Molecules 26, no. 7 (April 1, 2021): 2012. http://dx.doi.org/10.3390/molecules26072012.
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Over the past two decades, both fundamental and applied research in conducting polymers have grown rapidly. Conducting polymers (CPs) are unique due to their ease of synthesis, environmental stability, and simple doping/dedoping chemistry. Electrically conductive silicone polymers are the current state-of-the-art for, e.g., optoelectronic materials. The combination of inorganic elements and organic polymers leads to a highly electrically conductive composite with improved thermal stability. Silicone-based materials have a set of extremely interesting properties, i.e., very low surface energy, excellent gas and moisture permeability, good heat stability, low-temperature flexibility, and biocompatibility. The most effective parameters constructing the physical properties of CPs are conjugation length, degree of crystallinity, and intra- and inter-chain interactions. Conducting polymers, owing to their ease of synthesis, remarkable environmental stability, and high conductivity in the doped form, have remained thoroughly studied due to their varied applications in fields like biological activity, drug release systems, rechargeable batteries, and sensors. For this reason, this review provides an overview of organosilicon polymers that have been reported over the past two decades.
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Cepīte, D., and A. Jakovičs. "Analysis of Heat Transfer in the Structures with Regularly Arranged Gas Cavities." Latvian Journal of Physics and Technical Sciences 45, no. 4 (January 1, 2008): 14–24. http://dx.doi.org/10.2478/v10047-008-0016-4.
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Analysis of Heat Transfer in the Structures with Regularly Arranged Gas CavitiesIn the work, the effective thermal conductivity (ETC) of anisotropic composite material (well-conducting media with regular cavities of the air) is studied by numerical modelling. The authors examine the influence of orientation and size of the cavities on the ETC of material structure and the role of thermal conduction, convection and radiation in the heat transfer processes. For modelling,Keratermtype material was chosen. It has been proved numerically that the ETC of similar structures is lower in the case when the cavities are oriented perpendicularly to the heat flux direction as compared with parallel orientation. According to the analysis performed, the radiation heat exchange in such cavities dominates over the convective heat transfer in the observed temperature range. In the calculations of ETC in structures of the kind, convection inside the cavities can be omitted. The proposed approach allows optimisation of the arrangement and size of the cavities in similar building materials.
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Lee, Duck Weon, Joon-Hyung Jin, Eunae Kim, and Junghan Lee. "Experimental investigation for reverse heat transfer in structural fire-protective clothing." Textile Research Journal 88, no. 5 (December 22, 2016): 577–85. http://dx.doi.org/10.1177/0040517516685277.
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Structural fire-protective clothing must be effective at minimizing the thermal effects of fire. However, water remaining on the outer shell might play an important role in conducting heat transfer, which causes skin burns in a firefighter when he douses a fire with water through a hose. Therefore, this research demonstrated the difference in the heat transfer and humidity created by the remaining water or lack of water on the outer shell under a condition in which the temperature (45 ± 1℃) of the external environment was higher than that of the skin. Two types of multilayered systems, which simulated real fire-protective clothing (outer shell, moisture barrier, thermal liner) were tested by using a human–clothing–environment (HCE) simulator. The experimental results verified that water on the outer shell increased the microclimate temperature in the structural fire-protective clothing. In particular, we assume that air permeability in the outer shell can be an important factor to control heat and mass transfer within the microclimate.
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Astanina, Marina, Mikhail Sheremet, U. S. Mahabaleshwar, and Jitender Singh. "Effect of Porous Medium and Copper Heat Sink on Cooling of Heat-Generating Element." Energies 13, no. 10 (May 17, 2020): 2538. http://dx.doi.org/10.3390/en13102538.
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Cooling of heat-generating elements is a challenging problem in engineering. In this article, the transient free convection of a temperature-dependent viscosity liquid inside the porous cavity with copper radiator and the heat-generating element is studied using mathematical modeling techniques. The vertical and top walls of the chamber are kept at low constant temperature, while the bottom wall is kept adiabatic. The working fluid is a heat-conducting liquid with temperature-dependent viscosity. A mathematical model is developed based on dimensionless stream function, vorticity, and temperature variables. The governing properties are the variable viscosity, geometric parameters of the radiator, and size of thermally insulated strip on vertical surfaces of the cavity. The effect of these parameters on the energy transport and circulation patterns are analyzed numerically. Based on the numerical results obtained, recommendations are given on the optimal values of the governing parameters for the effective operation of the cooling system. It is shown that the optimal number of radiator fins for the cooling system configuration under consideration is 3. In addition, the thermal insulation of the vertical walls and the increased thickness of the radiator fins have a negative effect on the operation of the cooling system.
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Chumak, K. А., and R. М. Martynyak. "Effective Thermal Contact Resistance of Regularly Textured Bodies in the Presence of Intercontact Heat-Conducting Media and the Phenomenon of Thermal Rectification." Journal of Mathematical Sciences 236, no. 2 (November 5, 2018): 160–71. http://dx.doi.org/10.1007/s10958-018-4103-7.
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Işcan, Yılmaz Vahit Vahit, and Hatice Güngör Seyhan. "The Effect of the 5E Learning Model Supported with Material Ensuring Conceptual Change on Science Achievement: The Example of “Heat and Temperature”." Mimbar Sekolah Dasar 8, no. 3 (December 11, 2021): 250–80. http://dx.doi.org/10.53400/mimbar-sd.v8i3.33044.
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This study seeks to examine the effect of the 5E learning model, as one of the constructivist learning approach models, supported by conceptual change texts and enriched with relevant guidance materials on eliminating the fifth-grade students' (n=42) misconceptions about "Heat and Temperature". A quantitative research approach was employed by conducting the pre-test and post-test quasi-experimental design of the non-equivalent groups, namely the experimental and control groups. Before the implications, the Heat and Temperature Achievement Test (HTAT) was used to determine the academic achievement levels of the students in the experimental and control groups in the topic of heat and temperature. The pre-test results between both group students did not find a significant difference. There was a significant difference in favor of the experimental group between the HTAT post-test results. From the results obtained within the scope of the study, it was concluded that this learning model was effective in eliminating the fifth-grade students' misconceptions about the topic of heat and temperature.
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Ahn, Joon, Jeong Chul Song, and Joon Sik Lee. "Fully Coupled Large Eddy Simulation of Conjugate Heat Transfer in a Ribbed Channel with a 0.1 Blockage Ratio." Energies 14, no. 8 (April 9, 2021): 2096. http://dx.doi.org/10.3390/en14082096.
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Large eddy simulations are performed to analyze the conjugate heat transfer of turbulent flow in a ribbed channel with a heat-conducting solid wall. An immersed boundary method (IBM) is used to determine the effect of heat transfer in the solid region on that in the fluid region in a unitary computational domain. To satisfy the continuity of the heat flux at the solid–fluid interface, effective conductivity is introduced. By applying the IBM, it is possible to fully couple the convection on the fluid side and the conduction inside the solid and use a dynamic subgrid scale model in a Cartesian grid. The blockage ratio (e/H) is set at 0.1, which is typical for gas turbine blades. Through conjugate heat transfer analysis, it is confirmed that the heat transfer peak in front of the rib occurs because of the impinging of the reattached flow and not the influence of the thermal boundary condition. When the rib turbulator acts as a fin, its efficiency and effectiveness are predicted to be 98.9% and 8.32, respectively. When considering conjugate heat transfer, the total heat transfer rate is reduced by 3% compared with that of the isothermal wall. The typical Biot number at the internal cooling passage of a gas turbine is <0.1, and the use of the rib height as the characteristic length better represents the heat transfer of the rib.
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Orlova, E. "THE SYNERGETIC OF FUEL ELEMENT." PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. SERIES: NUCLEAR AND REACTOR CONSTANTS 2019, no. 3 (September 26, 2019): 261–72. http://dx.doi.org/10.55176/2414-1038-2019-3-261-272.
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The fuel element is the complex system consisting of fuel, a sublayer, a cladding, protective coatings on a surface of a cladding and contacting to the cooler and material of a contour in general. The synergetic (self-coherence) of interaction of elements of this system has to be provided both concerning high heat conductivity of fuel element, and concerning corrosion compatibility. Use of a liquid metal sublayer (LMS) instead of gas, allows significantly (by hundreds of degrees) to reduce temperature in the center of fuel that increases safety at UTOP accidents (uncontrollable increase in power) at ULOF (loss of an expense of the cooler). Gap thickness when using LMS (unlike helium) can be significantly increased that will practically not affect thermal characteristics of fuel element, but will allow to distance considerably time of approach of direct contact of fuel with a cladding, having increased thereby depth of burning out of heavy atoms and having increased cost efficiency and competitiveness of fast reactors extension of the fuel elements resource. These principles when using heat-conducting nuclear fuel are especially effective (metal, nitride, carbide) and the lead heat carrier. Synergetic reasonable corrosion compatibility of a cladding of fuel element with LMS is confirmed with numerous settlement pilot studies by means of formation and self-curing of accidental damages of a protective coating of nitride of zirconium on the internal surface of steel in LMS of eutectic structure on the basis of lead with magnesium and zirconium. When using nitride fuel heat-conducting LMS with anticorrosive properties the resource of fuel element is limited not by swelling of fuel any more, and the dose damaging a cladding.
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Felius, Laurina C., Mohamed Hamdy, Fredrik Dessen, and Bozena Dorota Hrynyszyn. "Upgrading the Smartness of Retrofitting Packages towards Energy-Efficient Residential Buildings in Cold Climate Countries: Two Case Studies." Buildings 10, no. 11 (November 3, 2020): 200. http://dx.doi.org/10.3390/buildings10110200.
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Improving the energy efficiency of existing buildings by implementing building automation control strategies (BACS) besides building envelope and energy system retrofitting has been recommended by the Energy Performance of Buildings Directive (EPBD) 2018. This paper investigated this recommendation by conducting a simulation-based optimization to explore cost-effective retrofitting combinations of building envelope, energy systems and BACS measures in-line with automation standard EN 15232. Two cases (i.e., a typical single-family house and apartment block) were modeled and simulated using IDA Indoor Climate and Energy (IDA-ICE). The built-in optimization tool, GenOpt, was used to minimize energy consumption as the single objective function. The associated difference in life cycle cost, compared to the reference design, was calculated for each optimization iteration. Thermal comfort of the optimized solutions was assessed to verify the thermal comfort acceptability. Installing an air source heat pump had a greater energy-saving potential than reducing heat losses through the building envelope. Implementing BACS achieved cost-effective energy savings up to 24%. Energy savings up to 57% were estimated when BACS was combined with the other retrofitting measures. Particularly for compact buildings, where the potential of reducing heat losses through the envelope is limited, the impact of BACS increased. BACS also improved the thermal comfort.
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Hitchen, Joseph, and Andrew J. Wells. "The impact of imperfect heat transfer on the convective instability of a thermal boundary layer in a porous media." Journal of Fluid Mechanics 794 (March 30, 2016): 154–74. http://dx.doi.org/10.1017/jfm.2016.149.
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We consider convective instability in a deep porous medium cooled from above with a linearised thermal exchange at the upper surface, thus determining the impact of using a Robin boundary condition, in contrast to previous studies using a Dirichlet boundary condition. With the linearised surface exchange, the thermal flux out of the porous layer depends linearly on the temperature difference between the effective temperature of a heat sink at the upper boundary and the temperature at the surface of the porous layer. The rate of this exchange is characterised by a dimensionless Biot number, $\mathit{Bi}$, determined by the effective thermal conductivity of exchange with the heat sink relative to the physical thermal conductivity of the porous layer. For a given temperature difference between the heat sink at the upper boundary and deep in the porous medium, we find that imperfectly cooled layers with finite Biot numbers are more stable to convective instabilities than perfectly cooled layers which have large, effectively infinite Biot numbers. Two regimes of behaviour were determined with contrasting stability behaviour and characteristic scales. When the Biot number is large the near-perfect heat transfer produces small corrections of order $1/\mathit{Bi}$ to the perfectly conducting behaviour found when the Biot number is infinite. In the insulating limit as the Biot number approaches zero, a different behaviour was found with significantly larger scales for the critical wavelength and depth of convection both scaling proportional to $1/\sqrt{\mathit{Bi}}$.
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Gonzales, G. V., E. D. Dos Santos, L. R. Emmendorfer, L. A. Isoldi, E. S. D. Estrada, and L. A. O. Rocha. "CONSTRUCTAL DESIGN AND SIMULATED ANNEALING EMPLOYED FOR GEOMETRIC OPTIMIZATION OF A Y-SHAPED CAVITY INTRUDED INTO CONDUCTIVE WALL." Revista de Engenharia Térmica 14, no. 1 (June 30, 2015): 79. http://dx.doi.org/10.5380/reterm.v14i1.62118.
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he problem study here is concerned with the geometrical evaluation of an isothermal Y-shaped cavity intruded into conducting solid wall with internal heat generation. The cavity acts as a sink of the heat generated into the solid. The main purpose here is to minimize the maximal excess of temperature (θmax) in the solid. Constructal Design, which is based on the objective and constraints principle, is employed to evaluate the geometries of Y-shaped cavity. Meanwhile, Simulated Annealing (SA) algorithm is employed as optimization method to seek for the best shapes. To validate the SA methodology, the results obtained with SA are compared with those achieved with Genetic Algorithm (GA) and Exaustive Search (ES) in recent studies of literature. The comparison between the optimization methods (SA, GA and ES) showed that Simulated Annealing is highly effective in the search for the optimal shapes of the studied case.
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Huang, Yi-Hsiang, and Suresh K. Aggarwal. "Effect of Wall Conduction on Natural Convection in an Enclosure With a Centered Heat Source." Journal of Electronic Packaging 117, no. 4 (December 1, 1995): 301–6. http://dx.doi.org/10.1115/1.2792109.
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This study presents a numerical investigation of the effects of wall conduction on laminar natural convection heat transfer in a two-dimensional rectangular enclosure. The heat transfer is driven by a constant-temperature heat source in the center of the enclosure. The time dependent governing equations in the primitive form are solved numerically by the use of a finite-volume method. The numerical algorithm is first validated by comparing our predictions with those of Kim and Viskanta for a square cavity surrounded by four conducting walls. A parametric study is then conducted to examine the effects of wall conduction on the natural convection heat transfer. The parameters include the Rayleigh number, wall thickness, wall thermal conductivity ratio and diffusivity ratio. In addition, the effects of varying thermal boundary conditions on the outside walls are reported. Results indicate that the qualitative features of natural convection heat transfer in the laminar range are not significantly altered by the inclusion of wall conduction. However, the quantitative results may be significantly modified by the wall conductance. In general, the wall conduction reduces the rate of heat dissipation from the enclosure. The average Nusselt number decreases as the wall thickness ratio is increased and/or the wall thermal conductivity is reduced. Results also indicate that it may be possible to define an effective Rayleigh number that includes the effects of wall thickness and conductivity.
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Chen, Zhang, Ting Yang, Lin Cheng, and Jianxin Mu. "Excellent Thermally Conducting Ni Plating Graphite Nanoplatelets/Poly(phenylene sulfone) Composites for High-Performance Electromagnetic Interference Shielding Effectiveness." Polymers 13, no. 20 (October 12, 2021): 3493. http://dx.doi.org/10.3390/polym13203493.
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First, nickel particles were deposited on the surface of graphite nanoplatelets to fabricate highly conductive GnPs@Ni core-shell structure hybrid fillers via electroplating. The modified GnPs were blended with polyphenylene sulfone via the solution blending method, followed by the hot-pressing method to achieve high thermally conducting GnPs@Ni/PPSU composites for high performance electromagnetic interference effectiveness. The results showed that in-plane and through-plane thermal conductivity of the composite at the 40 wt% filler loading could reach 2.6 Wm−1K−1 and 3.7 Wm−1K−1, respectively, which were 9.4 and 20 times higher than that of pure PPSU resin. The orientation degree of fillers was discussed by XRD and SEM. Then, heat conduction data were fitted and analyzed by the Agari model, and the heat conduction mechanism was further explored. The testing results also demonstrated that the material exhibited good conductivity, electromagnetic shielding effectiveness and superior thermal stability. Overall, the GnPs@Ni/PPSU composites had high thermal conductivity and were effective electromagnetic shielding materials at high temperatures.
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Wang, Yu, Bian, Wu, Xiao, and Dai. "Thermally Conductive and Electrical Insulation BNNS/CNF Aerogel Nano-Paper." Polymers 11, no. 4 (April 10, 2019): 660. http://dx.doi.org/10.3390/polym11040660.
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Adding heat conducting particles to a polymer matrix to prepare thermally conductive and electrical insulation materials is an effective approach to address the safety issues arising from the accumulation of heat in the working process of electronic devices. In this work, thermally conductive and electrical insulation nano-paper, consisting of Boron Nitride nano-sheet (BNNS) and cellulose nanofiber (CNF), was prepared using an aerogel 3D skeleton template method. For comparison, BNNS/CNF nano-paper was also produced using a simple blending method. At a BNNS loading of 50 wt%, the thermal conductivity of BNNS/CNF aerogel nano-paper and blended nano-paper at 70 °C are 2.4 W/mK and 1.2 W/mK respectively, revealing an increase of 94.4%. Under similar conditions, the volume resistivity of BNNS/CNF aerogel nano-paper and blended nano-paper are 4.0 × 1014 and 4.2 × 1014 Ω·cm respectively. In view of its excellent thermal conductivity and electrical insulation performance, therefore, BNNS/CNF aerogel nano-paper holds great potential for electronic-related applications.
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Hachul, Helmut, Daniela Ridder, Yesim Tekinbas, Federico Giovannetti, Finn Weiland, and Maik Kirchner. "Solar thermal component activation." Journal of Physics: Conference Series 2042, no. 1 (November 1, 2021): 012100. http://dx.doi.org/10.1088/1742-6596/2042/1/012100.
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Abstract Wall and roof components made of steel sandwich elements are firmly established in industrial and commercial construction. They are cost-effective and characterized by excellent physical properties. Here, hybrid approaches from heating- and cooling ceiling construction were examined for the solar thermal activation of sandwich elements. Besides the implementation of the solar components, the connection to and the optimization of the system technology was focused. In addition, alternative piping materials were investigated numerically and experimentally. The performance as well as the static and thermo-hydraulic behavior of the new active components were simulatively and experimentally examined, and the economic viability of the variants was also checked. With the newly developed solar sandwich elements, an overall energy concept was developed with connection variants to the building services system, control and storage technology. Steel sandwich elements with mineral fiber core are well suited for the hidden integration of component parts such as pipe registers and heat conducting plates. The functionality of the component has been proven, the implementation of heat exchanger leads to considerable heat gains. In combination with a brine-to-water heat pump system, the solar panel can provide for a more sustainable operation and a significant size reduction of the geothermal source.
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Drgoňa, Peter, Rastislav Štefún, and Ľ. Štefke. "Design of a Dispensing CNC Device." TRANSACTIONS ON ELECTRICAL ENGINEERING 7, no. 2 (March 30, 2020): 37–41. http://dx.doi.org/10.14311/tee.2018.2.037.
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<span style="font-family: 'Times New Roman',serif; font-size: 10pt; -ms-layout-grid-mode: line; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-GB; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-GB">This article deals with the design and practical realization of a CNC device designed for the application of viscous materials, such as a thermal conducting paste. Paste is used for effective heat transfer what is essential in switched mode power supplies. However, its application on surface can be an issue. Designed CNC device serves for easier and more accurate application in production process using standard tubes.</span>
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Abdulmumuni, Bashiru, Adedeji Mathew Ayoade, Ologunye Opeyemi Buhari, Azeez Rasheed Olatunde, and Fanifosi Johnson Olaniyi. "Design, Fabrication and Performance Evaluation of a Shell and Tube Heat Exchanger for Practical Application." European Journal of Engineering Research and Science 5, no. 8 (August 13, 2020): 835–45. http://dx.doi.org/10.24018/ejers.2020.5.8.1997.
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A heat exchanger is a device used to transfer thermal energy between two or more fluids, at different temperatures in thermal contact. This paper focuses on a shell-and-tubes heat exchanger that involves two fluids (hot water and cold water) in contact with each other while the cold water flows through the tubes and hot water through the shell. Heat exchangers have special and practical applications in the feed water cooler in the process industries, power plants, chemical plants, refineries, process applications as well as refrigeration and air conditioning industry. The design calculations were carried out to determine the specifications of essential parameters for the development of the heat exchanger, data generated from the theoretical formulae were used to fabricate the heat exchanger using some locally available and durable materials, and the performance of the system was evaluated. Some of the parameters evaluated include heat duty, capacity ratio, effectiveness, overall heat transfer coefficient, and fouling factor. The heat exchanger was tested under various flow conditions and the results obtained were as follows; cold water inlet temperatures of (26, 26, 26, 27and 27) ºC increased to (59, 44, 39, 47 and 35) ºC after (10, 7½, 6½ 8, and 6) minutes and the hot water temperatures decreased from (100, 80, 75, 87 and 73) ºC to (73, 59, 55, 62 and 50) ºC, respectively. The design data and test data were compared in terms of the heat duty, capacity ratio, effectiveness, overall heat transfer coefficient, and fouling factor, the deviation is found to be 22.87%, 13.99%, 8.98%, 43.30%, and 43.30% respectively. The results obtained proved that the heat exchanger was effective, reliable and provides a good technical approach to evaluate the thermal performance of the heat exchanger and useful in conducting heat and mass transfer practical in thermodynamics laboratory.
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Abdulmumuni, Bashiru, Adedeji Mathew Ayoade, Ologunye Opeyemi Buhari, Azeez Rasheed Olatunde, and Fanifosi Johnson Olaniyi. "Design, Fabrication and Performance Evaluation of a Shell and Tube Heat Exchanger for Practical Application." European Journal of Engineering and Technology Research 5, no. 8 (August 13, 2020): 835–45. http://dx.doi.org/10.24018/ejeng.2020.5.8.1997.
Full textAbstract:
A heat exchanger is a device used to transfer thermal energy between two or more fluids, at different temperatures in thermal contact. This paper focuses on a shell-and-tubes heat exchanger that involves two fluids (hot water and cold water) in contact with each other while the cold water flows through the tubes and hot water through the shell. Heat exchangers have special and practical applications in the feed water cooler in the process industries, power plants, chemical plants, refineries, process applications as well as refrigeration and air conditioning industry. The design calculations were carried out to determine the specifications of essential parameters for the development of the heat exchanger, data generated from the theoretical formulae were used to fabricate the heat exchanger using some locally available and durable materials, and the performance of the system was evaluated. Some of the parameters evaluated include heat duty, capacity ratio, effectiveness, overall heat transfer coefficient, and fouling factor. The heat exchanger was tested under various flow conditions and the results obtained were as follows; cold water inlet temperatures of (26, 26, 26, 27and 27) ºC increased to (59, 44, 39, 47 and 35) ºC after (10, 7½, 6½ 8, and 6) minutes and the hot water temperatures decreased from (100, 80, 75, 87 and 73) ºC to (73, 59, 55, 62 and 50) ºC, respectively. The design data and test data were compared in terms of the heat duty, capacity ratio, effectiveness, overall heat transfer coefficient, and fouling factor, the deviation is found to be 22.87%, 13.99%, 8.98%, 43.30%, and 43.30% respectively. The results obtained proved that the heat exchanger was effective, reliable and provides a good technical approach to evaluate the thermal performance of the heat exchanger and useful in conducting heat and mass transfer practical in thermodynamics laboratory.
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Gorskiy, V. V., and A. G. Loktionova. "Simulating Heat Exchange and Friction in a Thin Laminar Boundary Layer of Air over the Lateral Surface of a Blunted Cone Featuring a Low Aspect Ratio." Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, no. 6 (135) (December 2020): 4–20. http://dx.doi.org/10.18698/0236-3941-2020-6-4-20.
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It is not possible to obtain a high-quality solution to a convective heat transfer problem without numerically integrating the differential equations describing the boundary layer, which involves a whole range of computational issues. Developing relatively simple yet adequately accurate computation methods becomes crucial. Using the effective length method may be considered to be the first step towards solving this problem. This method boasts an accuracy of convective heat transfer calculation that is acceptable in practice, due to which it became prevalent in aircraft design. However, this method is also relatively labour-intensive, although significantly less so than numerical integration of the boundary layer differential equations. The most efficient approach to solving heat transfer and friction problems in engineering practice would be using simple algebraic equations based on fitting the results of rigorous numerical computations or experimental investigations. Regrettably, there is no information published regarding how accurate these equations are for various operation conditions. The paper presents a solution to this problem based on deriving systematic numerical solutions to the boundary layer equations in the most rigorous analytical statement, along with conducting a thorough analysis of the equation accuracy for both the equations derived and previously published
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Ashwinkumar, G. P., C. Sulochana, and S. P. Samrat. "Effect of the aligned magnetic field on the boundary layer analysis of magnetic-nanofluid over a semi-infinite vertical plate with ferrous nanoparticles." Multidiscipline Modeling in Materials and Structures 14, no. 3 (September 3, 2018): 497–515. http://dx.doi.org/10.1108/mmms-10-2017-0128.
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Purpose The purpose of this paper is to investigate the momentum, heat and mass transfer characteristics of magnetic-nanofluid flow past a vertical plate embedded in a porous medium filled with ferrous nanoparticles. The analysis is carried out in the presence of pertinent physical parameters such as aligned magnetic field, thermal radiation, chemical reaction, radiation absorption, heat source/sink. Design/methodology/approach The flow governing PDEs are transformed into ODEs using appropriate conversions. Further, the set of ODEs is solved analytically using the perturbation technique. The flow quantities such as velocity, thermal and concentration fields are discussed under the influence of above-mentioned pertinent physical parameters with the assistance of graphical depictions. Moreover, the friction factor, local Nusselt and Sherwood number are discussed in tabular form. Findings The results indicate that flow and thermal transport phenomenon is more effective in the case of the aligned magnetic field as compared with the transverse magnetic field. Also, the nanoparticle volume fraction plays a vital role in controlling the wall friction and heat transfer performance. The validation of the obtained results is done by comparing them with the results of various numerical techniques, and hence found them in excellent agreement. Originality/value In present days, the external magnetic fields are very effective to set the thermal and physical properties of magnetic-nanofluids and regulate the flow and heat transfer characteristics. The strength of the applied magnetic field affects the thermal conductivity of magnetic-nanofluids and makes it aeolotropic. With this incentive, the authors investigated the flow and heat transfer characteristics of electrically conducting magnetic-nanofluids over a vertical surface embedded in a porous medium. The authors discussed the dual nature of ferrous-water nanofluid in the presence of aligned magnetic field and transverse magnetic field cases. The influence of several physical parameters on velocity, thermal and concentration field converses with the succour of graphs.
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Cao, Mengbing, Chao Zong, Yanrong Zhuang, Guanghui Teng, Shengnan Zhou, and Ting Yang. "Modeling of Heat Stress in Sows Part 2: Comparison of Various Thermal Comfort Indices." Animals 11, no. 6 (May 21, 2021): 1498. http://dx.doi.org/10.3390/ani11061498.
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Heat stress has an adverse effect on the production performance of sows, and causes a large economic loss every year. The thermal environment index is an important indicator for evaluating the level of heat stress in animals. Many thermal indices have been used to analyze the environment of the pig house, including temperature and humidity index (THI), effective temperature (ET), equivalent temperature index of sows (ETIS), and enthalpy (H), among others. Different heat indices have different characteristics, and it is necessary to analyze and compare the characteristics of heat indices to select a relatively suitable heat index for specific application. This article reviews the thermal environment indices used in the process of sow breeding, and compares various heat indices in four ways: (1) Holding the value of the thermal index constant and analyzing the equivalent temperature changes caused by the relative humidity. (2) Analyzing the variations of ET and ETIS caused by changes in air velocity. (3) Conducting a comparative analysis of a variety of isothermal lines fitted to the psychrometric chart. (4) Analyzing the distributions of various heat index values inside the sow barn and the correlation between various heat indices and sow heat dissipation with the use of computational fluid dynamics (CFD) technology. The results show that the ETIS performs better than other thermal indices in the analysis of sows’ thermal environment, followed by THI2, THI4, and THI7. Different pigs have different heat transfer characteristics and different adaptability to the environment. Therefore, based on the above results, the following suggestions have been given: The thermal index thresholds need to be divided based on the adaptability of pigs to the environment at different growth stages and the different climates in different regions. An appropriate threshold for a thermal index can provide a theoretical basis for the environmental control of the pig house.
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Volcheck, V. S., and V. R. Stempitsky. "Gallium nitride heterostructure field-effect transistor with a heat-removal system based on a trench in the passivation layer filled by a high thermal conductivity material." Doklady BGUIR 19, no. 6 (October 1, 2021): 74–82. http://dx.doi.org/10.35596/1729-7648-2021-19-6-74-82.
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The self-heating effect poses a main problem for high-power electronic and optoelectronic devices based on gallium nitride. A non-uniform distribution of the dissipated power and a rise of the average temperature inside the gallium nitride heterostructure field-effect transistor lead to the formation of a hot spot near the conducting channel and result in the degradation of the drain current, output power and device reliability. The purpose of this work is to develop the design of a gallium nitride heterostructure field-effect transistor with an effective heat-removal system and to study using numerical simulation the thermal phenomena specific to this device. The objects of the research are the device structures formed on sapphire, each of whom features both a graphene heat-eliminating element on its top surface and a trench in the passivation layer filled by a high thermal conductivity material. The subject of the research is the electrical and thermal characteristics of these device structures. The simulation results verify the effectiveness of the integration of the heat-removal system into the gallium nitride heterostructure field-effect transistor that can mitigate the self-heating effect and improve the device performance. The advantage of our concept is that the graphene heat-eliminating element is structurally connected with a heat sink and is designed for removing the heat immediately from the maximum temperature area through the trench in which a high thermal conductivity material is deposited. The results can be used by the electronics industry of the Republic of Belarus for developing the hardware components of gallium nitride power electronics.
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Kameya, Yuki, Ryota Osonoe, and Yuto Anjo. "Hydrophilic Coating of Copper Particle Monolayer Wicks for Enhanced Passive Water Transport." Energies 13, no. 12 (June 26, 2020): 3294. http://dx.doi.org/10.3390/en13123294.
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Passive water transport through thin-surface wicks made of heat conducting material is important for developing thermal management devices such as heat pipes and spreaders. In this study, we demonstrated the hydrophilic coating of a Cu particle monolayer wick for enhanced water transport. We fabricated a Cu particle monolayer using Cu powder with a nominal particle diameter of 100 μm and determined the particle size distribution using scanning electron microscopy (SEM). We observed a remarkable change in the water contact angle on the application of a hydrophilic coating, which demonstrated the enhanced passive water transport. The elemental mapping of Cu, O, and Si obtained by electron probe microanalysis confirmed the deposition of the SiO2-based coating material on each Cu particle. Although the Cu particles were only partially covered by SiO2, a remarkable enhancement in wettability was achieved. Finally, we conducted a rate-of-rise experiment to quantitatively characterize the water transport performance of the coated Cu particle monolayer. Thus, we propose hydrophilic coating as a simple and effective method to enhance passive water transport through Cu particle monolayer wicks.
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Wang, Hongjie, Xiaolu Gao, Zening Xu, Yuan Li, Xinyue Zhang, and Mark W. Rosenberg. "Exploring the Climate Temperature Effects on Settlement Intentions of Older Migrants: Evidence from China." International Journal of Environmental Research and Public Health 19, no. 8 (April 18, 2022): 4896. http://dx.doi.org/10.3390/ijerph19084896.
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Permanent migration across provinces in China has become an important strategy for Chinese older people to respond to a temperature-unfriendly place of residence in late life. However, the relation between temperature effects and permanent settlements of older migrants remains unclear. Based on the data obtained from China Migrants Dynamic Survey, this paper examined how four temperature effects (i.e., cold effect, heat effect, temperature gap effect, and temperature zone effect) play a role in shaping older migrants’ intentions to settle permanently in a destination place by conducting logistic regression analysis. Our findings show that: (1) extreme cold (rather than extreme heat or mild temperature) was found to have significant effects on settlement intentions of older people; (2) relative winter temperature between origin and destination places rather than absolute winter temperature in the destination place has a significant positive effect on the settlement intentions; (3) spatially, older migrants tend to migrate to geographically adjacent temperature zones. Our findings will inform a more effective planning and allocation of services for supporting older people by better understanding trends and intentions of older migrants.
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Suleymanov, K., I. Pogorelova, and I. Ryabchevskiy. "INCREASING THE THERMAL UNIFORMITY OF WALLS MADE OF CELLULAR CONCRETE BLOCKS." Bulletin of Belgorod State Technological University named after. V. G. Shukhov 7, no. 5 (May 11, 2022): 17–24. http://dx.doi.org/10.34031/2071-7318-2022-7-5-17-24.
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The development of effective protecting structures is currently one of the most popular areas in the construction industry. Masonry made of aerated concrete blocks is used in conditions of ensuring energy efficiency and environmental safety in the construction of civil buildings as enclosing structures. It has high thermal protection properties. The issue of filling through seams of aerated concrete masonry is acute, since adhesive and cement-sand mortars in masonry have low thermal conductivity and are temperature bridges. The authors have developed a two-row energy-efficient wall masonry made of aerated concrete blocks using polyurethane glue as a filler for through and dressing joints. The article discusses the effect of horizontal through joints made of cement-sand mortar and blocking of blocks on the resistance to heat transfer of masonry from aerated concrete blocks. In addition, it presents a study of the reduced resistance to heat transfer of the enclosing structure, taking into account heat-conducting inclusions, presented in the form of a traditional two-row aerated concrete masonry through a row, made on a thin-layer adhesive solution, as well as the masonry developed by the authors. It is concluded that the energy efficiency of the developed wall fencing is ensured due to the increased thermal homogeneity of the masonry.
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Mahanthesh, B., B. J. Gireesha, and R. S. R. Gorla. "Mixed convection squeezing three-dimensional flow in a rotating channel filled with nanofluid." International Journal of Numerical Methods for Heat & Fluid Flow 26, no. 5 (June 6, 2016): 1460–85. http://dx.doi.org/10.1108/hff-03-2015-0087.
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Purpose – The purpose of this paper is to numerically solve the problem of an unsteady squeezing three-dimensional flow and heat transfer of a nanofluid in rotating vertical channel of stretching left plane. The fluid is assumed to be Newtonian, incompressible and electrically conducting embedded with nanoparticles. Effect of internal heat generation/ absorption is also considered in energy equation. Four different types of nanoparticles are considered, namely, copper (Cu), alumina (Al2O3), silver (Ag) and titanium oxide (TiO2) with the base fluid as water. Maxwell-Garnetts and Brinkman models are, respectively, employed to calculate the effective thermal conductivity and viscosity of the nanofluid. Design/methodology/approach – Using suitable similarity transformations, the governing partial differential equations are transformed into set of ordinary differential equations. Resultant equations have been solved numerically using Runge-Kutta-Fehlberg fourth fifth order method for different values of the governing parameters. Effects of pertinent parameters on normal, axial and tangential components of velocity and temperature distributions are presented through graphs and discussed in detail. Further, effects of nanoparticle volume fraction, squeezing parameter, suction/injection parameter and heat source/sink parameter on skin friction and local Nusselt number profiles for different nanoparticles are presented in tables and analyzed. Findings – Squeezing effect enhances the temperature field and consequently reduces the heat transfer rate. Large values of mixed convection parameter showed a significant effect on velocity components. Also, in many heat transfer applications, nanofluids are potentially useful because of their novel properties. They exhibit high-thermal conductivity compared to the base fluids. Further, squeezing and rotation effects are desirable in control the heat transfer. Originality/value – Three-dimensional mixed convection flows over in rotating vertical channel filled with nanofluid are very rare in the literature. Mixed convection squeezing three-dimensional flow in a rotating channel filled with nanofluid is first time investigated.
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Sharma, Shubham, P. Sudhakara, Abdoulhdi A. Borhana Omran, Jujhar Singh, and R. A. Ilyas. "Recent Trends and Developments in Conducting Polymer Nanocomposites for Multifunctional Applications." Polymers 13, no. 17 (August 28, 2021): 2898. http://dx.doi.org/10.3390/polym13172898.
Full textAbstract:
Electrically-conducting polymers (CPs) were first developed as a revolutionary class of organic compounds that possess optical and electrical properties comparable to that of metals as well as inorganic semiconductors and display the commendable properties correlated with traditional polymers, like the ease of manufacture along with resilience in processing. Polymer nanocomposites are designed and manufactured to ensure excellent promising properties for anti-static (electrically conducting), anti-corrosion, actuators, sensors, shape memory alloys, biomedical, flexible electronics, solar cells, fuel cells, supercapacitors, LEDs, and adhesive applications with desired-appealing and cost-effective, functional surface coatings. The distinctive properties of nanocomposite materials involve significantly improved mechanical characteristics, barrier-properties, weight-reduction, and increased, long-lasting performance in terms of heat, wear, and scratch-resistant. Constraint in availability of power due to continuous depletion in the reservoirs of fossil fuels has affected the performance and functioning of electronic and energy storage appliances. For such reasons, efforts to modify the performance of such appliances are under way through blending design engineering with organic electronics. Unlike conventional inorganic semiconductors, organic electronic materials are developed from conducting polymers (CPs), dyes and charge transfer complexes. However, the conductive polymers are perhaps more bio-compatible rather than conventional metals or semi-conductive materials. Such characteristics make it more fascinating for bio-engineering investigators to conduct research on polymers possessing antistatic properties for various applications. An extensive overview of different techniques of synthesis and the applications of polymer bio-nanocomposites in various fields of sensors, actuators, shape memory polymers, flexible electronics, optical limiting, electrical properties (batteries, solar cells, fuel cells, supercapacitors, LEDs), corrosion-protection and biomedical application are well-summarized from the findings all across the world in more than 150 references, exclusively from the past four years. This paper also presents recent advancements in composites of rare-earth oxides based on conducting polymer composites. Across a variety of biological and medical applications, the fact that numerous tissues were receptive to electric fields and stimuli made CPs more enticing.
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Крашаница, Юрий Александрович, and Кристина Владимировна Гуторова. "МЕТОД ГАЗОДИНАМИЧЕСКОЙ ОБРАБОТКИ ДЕТАЛЕЙ ОБЪЕКТОВ АВИАКОСМИЧЕСОЙ ТЕХНИКИ." Aerospace technic and technology, no. 1 (March 7, 2019): 72–78. http://dx.doi.org/10.32620/aktt.2019.1.09.
Full textAbstract:
The current level of technological development is characterized by the constant complexity of the products. For its production requires processing a large number of parts of complex shape. Mathematical modeling is an effective and economical way to solve many technical problems. There are various ways to ensure the necessary cleanliness of machine parts or reduce the negative effects of technological pollution. Existing methods of finishing and cleaning parts on the physical-chemical effects on the material during processing are divided into several groups. The most widespread are both mechanical methods in which the removal of defects is carried out by mechanical action on machined parts of tools and chemical and mechanical methods in which there is a simultaneous mechanical effect of the tool and the chemical action of the external. The gas-dynamic method of removing defects that occur after the preliminary metalworking of parts of aircraft objects seems to be very effective. The mathematical model of this process is the system of laws for the conservation of the dynamics of a viscous heat-conducting gas, the physicochemical characteristics of which are established in an experimental way. The construction of a gas-dynamic model of the physical process of finishing parts as an arbitrary spatial form and the material of manufacture is presented. On the basis of the general laws of conservation of the dynamics of a viscous heat-conducting gas, analytical forms of solutions for the kinematic and dynamic characteristics of a high-temperature flow are obtained using the example of a flat channel simulating the surface of a part being cleaned. It is shown that in the flat case the conservation laws have a linear form, which provided exact solutions for the kinematic characteristics, such as the velocity and vorticity of a viscous gas flow, which play a major role in calculating the dynamic and thermal characteristics of the flow. The use of a generalized apparatus of vector-tensor analysis is fundamentally important in order to obtain integral representations of the solutions of differential forms of the laws of conservation of momentum and energy in the control region. Control of gas dynamic and thermodynamic parameters of the flow is able to provide a high-quality surface.