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The intention of this article is to explore the radiation effects of MHD free convective heat transmission past an oscillating hot perpendicular surface in porous medium. The fluid is understood to be viscous, incompressible and the flow is considered as time dependent. Since the paper has aim to study MHD flow problem, the fluid should be electrically conducting. The problem has been modelled mathematically by system of PDEs. The systems of PDEs are worked out by adopting Laplace transform method. In this paper, a closed form of solution have been obtained. The results for the velocity, temperature, Nusselt number and skin-friction have been determined. The given graphs and tables deal with the flow characteristics with reference to the effects of magnetic parameter, Prandtl number, Grashof number, permeability, heat source/sink parameter and radiation parameter. The results show that the proposed method can effectively predict these values with accuracy and may be valuable in many engineering applications. [ABSTRACT FROM AUTHOR]

Smartflower (sunflower) is a compact energy generating system, it consists of a base structure, that houses a foldable array of solar cells that are deployed upon use and is able to track the movement of the sun along the hemisphere. The smart sunflower system's panels differ significantly from the traditional PV panels. In this paper, the thermal behavior analysis of the smart sunflower solar PV panels system is proposed using ANSYS-2020 R2 steady-state thermal analysis. This analysis was applied for the computation of the PV panel temperature distribution which was subjected to various atmospheric conditions. Existing formulations in the available literature are taken into account and, are based on NOCT conditions for several wind speeds and solar irradiance. The performance of the PV sunflower panel is compared with the usual solar panels at the same rated power. The proposed analysis is also used to consider the effect of panel shape and the role of thermal inertia in the performance of the PV panels. Results showed that the sunflower thermal performance is improved in comparison with the usual panels for the same rated power and ambient conditions due to improvement in the thermal characteristics of the sunflower panel such as heat convection coefficient. This study of the sunflower performance stimulates to direct the design to the manufacturing processes and experimentally test the sunflower performance. [ABSTRACT FROM AUTHOR]

The experimental process carried out in this paper is to determine the convection heat transfer coefficient, overall heat transfer coefficient, and nanofluid heat transfer rate based on DWCNT (double-wall carbon nanotube) nanotubes applied to a shell and tube heat exchanger. The advantage of using DWCNT nanoparticles is the high thermal conductivity value. The volume fractions of nanoparticles were 0.1%, 0.3%, and 0.5% with the addition of PVP surfactant. Experimental tests were conducted to determine the heat transfer performance applied to a shell and tube type heat exchanger with upright baffles. This study aims to improve the heat transfer performance by utilizing nanofluids based on DWCNTs nanoparticles. As a result, using DWCNT nanofluids instead of base fluids increases the convective heat transfer coefficient values and overall heat transfer. The increase in the volume fraction of DWCNTs nanoparticles is also accompanied by an increase in the heat generated. The highest thermal conductivity was obtained by adding 0.5% volume of DWCNTs nanoparticles, which was 0.640 W/m.K. The highest heat transfer rate was produced by adding 0.5% volume fraction and 0.02% PVP with a result value of 70.191 W. [ABSTRACT FROM AUTHOR]

The present paper studies the scientific investigation of heat convection and mass transmission of flow past through exponentially expedite parabolic motion effects over a upright plate through cross diffusion and taking an account of the soret and dufourimpacts. The fluid past a dramatically quickened boundless isothermal plate is vertical in the presence of time, flexible heat and mass are elevated linearly has been considered. Utilizing explicit finite difference technique, the undimensioned principal equations are explained graphically through the profiles of velocity,temperature and concentration for pertinent measures of skin-friction, Sherwood number and Nusselt number. [ABSTRACT FROM AUTHOR]

Analytical solutions for heat transfer in a Newtonian viscous electrically conducting and heat-generating/absorbing fluid in a laminar flow over an inclined permeable surface are presented in this paper. They are solved analytically to the maximum extent possible for dimensionless governing equations. The impact of various involved factors is visually represented and described in depth. A reduction in skin friction can be noted when porosity rises. For a fixed pore size in the fluid bed, the skin friction is always constant and does not change with Grashoff number. The skin friction is shown to be independent of the Schmidt number. As the pore size of the boundary surface grows, the skin appears to become less supple. Furthermore, a rise in the Grashoff number adds to a decrease in skin friction. A consolidated study of all above illustrations suggest that the Schmidt number does not have any influence on the skin friction. [ABSTRACT FROM AUTHOR]

The experimental process is carried out in this paper to determine the value of the convection heat transfer coefficient, overall heat transfer coefficient, and the rate of heat transfer for nanofluids based on DWCNTs (double-wall carbon nanotubes) nanoparticles which ar e applied to shell and tube heat exchangers. The advantage of using DWCNTs nanoparticles is the high thermal conductivity value. The volume fractions of nanoparticles were 0.1%, 0.3%, and 0.5%. Tests were carried out to determine the heat transfer performance applied to the shell and tube type of baffle and no-baffle heat exchanger tools. The purpose of this research is to improve the heat transfer performance by utilizing nanofluids based on DWCNT nanoparticles. The results show an increase in the value of the convection heat transfer coefficient and the overall heat transfer coefficient when using DWCNTs nanofluids rather than using base fluids. [ABSTRACT FROM AUTHOR]

Investigation of unsteady flow characteristics through a curved duct is widely used in many engineering applications such as in fluid transportation, rotating machinery and metallic industry. Fluid behavior depends not only on the rotation of the duct but also on physical properties such as fluid pressure, curvature and aspect ratio of the duct. The present paper focuses on the time-dependent flow behavior through a rotating curved square duct. The bottom wall of the duct is heated while cooling from the ceiling, the inner and outer sidewalls being thermally insulated. Numerical calculations are carried out by using a spectral technique, where function expansion and collocation methods are applied for constant Dean number, Dn = 1000, the Grashof number, Gr = 100 and curvature, δ = 0.01 over a wide range of the Taylor number, −1500≤Tr≤1500. In this paper, we investigated flow characteristics for both positive and negative rotation of the duct. Due to combined action of the centrifugal, Coriolis and buoyancy forces various types of physically realizable transient solutions such as steady-state, periodic, multi-periodic and chaotic solutions have been obtained. Flow transitions are well determined by obtaining the power spectrum of the solutions. Typical contours of axial flow, secondary flow and temperature profiles have also been obtained and it is found that time-dependent solutions are comprised of two-to six-vortex solutions. The present study shows that convective heat transfer is significantly enhanced by the secondary flow and there is a strong interaction between the heating-induced buoyancy force and the centrifugal-Coriolis instability in the rotating curved duct that stimulates fluid mixing and consequently enhances heat transfer in the fluid. Finally, our numerical results have been compared with the experimental investigations and it is found that there is a good agreement between the numerical and experimental investigations. [ABSTRACT FROM AUTHOR]

Solar air heaters (SAHs) are used in a wide variety of household and industrial applications. Smooth absorber plate in traditional solar duct has a low value of convective heat transfer coefficient. Enhancing the thermal efficiency of SAHs can be achieved by using artificial roughness ribs placed on the absorber plate. However, this use of roughness results in increasing the pressure loss due to the friction between the airflow and roughened plate surface. This paper presents a summarized review of the recent studies that deal with the application of computational fluid dynamics (CFD) to enhance the thermohydraulic performance of SAHs by utilizing different designs of artificial roughness ribs. This includes the selection of a high-performance turbulence model based on Reynolds Averaged Navier Stokes (RANS) approach. The enhancement in the thermal performance parameter of a solar air heater, by utilizing different shaped roughness geometries with different configurations, based on recent studies is presented at a specific value of Reynolds number. [ABSTRACT FROM AUTHOR]

The paper presents a comparative analysis on the laminar convective heat transfer characteristics of a 2-D flow over three different grooved profiles. The profiles selected for this study are trapezoidal, triangular and sinusoidal. The numerical simulation is performed using ANSYS-FLUENT SOLVER to elucidate the effect of changing fluidic properties over these channels in the Reynolds number range of 400-1400. The analysis is performed using two different fluids namely water and SYLTHERM 800 to present the changing thermal and fluidic behavior among the channels having fixed length and ribs. The influences of these profiles on pressure drop, streamline contours, temperature variations and entropy variations are discussed in details over these fluids, more over the results are presented in a comparative manner. The Governing equations are discretized using Finite Volume Method (FVM) and SIMPLE Algorithm along with Second Order Upwind Difference Scheme. When SYLTHERM 800 is passed through these channels in the given Reynolds number range it is observed that the trapezoidal channel has minimum decrement in entropy followed by sinusoidal and triangular channels for this flow conditions. Also, when we compared the results obtained using SYLTHERM 800 with traditional fluid i.e., water, then it is observed that there is more pressure drop, heat dissipation and entropy generation in case of SYLTHERM 800. The outcomes obtained in this work will further contemplate researchers to design various devices and systems with better thermal efficiency for various engineering and household applications. [ABSTRACT FROM AUTHOR]

When punching openings in existing external enclosing structures, the need for which arises during the replanning and renovation of buildings, it is necessary to strengthen faces of the opening with metal ties. Angle bars and batten plates are usually used for this purpose. Metal ties, having high thermal conductivity, form thermal bypasses, which reduce resistance to heat convection in the section of the enclosing structure, where they have been installed. Metal ties also have high resistance to moisture vapor transmission. They prevent the movement of vapor humidity in winter from the inner surface of the enclosing structure to the outer one. This leads to moisture accumulation in the places of application of metal ties. A particularly difficult area, in terms of moisture accumulation, is the area between the slope surface on the internal face of the enclosing structure and the metallic batten plate. This is due to the lower resistance to heat convection in this area and high resistance to moisture vapor transmission of the metal bar. Deterioration in moisture resistance of the structure is also affected by the close location of this area to the outer slope of the window or door opening, which leads to temperature reduction in this area. The Paper reveals how the moisture resistance of the wall adjacent to the slopes of windows or doors is influenced by the size of metal angle bars, reinforcing the openings in the walls, thickness of the angle legs, and thickness of the battens connecting the angle bars and their metal pitch. The studies were performed for the walls of 0.25 m and 0.51 m in thickness. Methods for improving the moisture resistance of this part of the wall were also offered in the Article. [ABSTRACT FROM AUTHOR]

The paper proposes a solution for the modernization of boiler houses. With the help of equipment for pre-mixing air and natural gas, it is possible to ensure a more complete combustion of the fuel. A description of the basic scheme of mixing natural gas with atmospheric air is given. The influence of this decision on the economic and environmental parameters of the boiler house is shown. The results of experimental studies of the proposed solution, which were obtained at a district boiler house with installed boilers of the DKVr-10-13GM brand, are presented. The results obtained show that the use of the technology of feeding a pre-prepared gas-air mixture into the burners allows reducing the underburning of fuel and the concentration of carbon monoxide (CO) in the combustion products. At the same time, there was a decrease in the specific consumption of natural gas for heat generation from 133.3 m3/Gcal to 130.3 m3/Gcal with significant savings in cash. Other advantages of this solution are also observed: an increase in the radiation and a decrease in the convective component of the heat transfer process from the flare and exhaust gases; reducing the temperature of the exhaust gases; reducing the emission of harmful components into the atmosphere; increasing the efficiency of the boiler. [ABSTRACT FROM AUTHOR]

In this paper numerical investigation by ABAQUS software of heat conduction processes in the fins of two-stage "water to air" heat exchange (HEx) apparatus. Temperature values of the processes in ducts, have been used as boundary conditions for accomplishment of the simulations in the heat exchanger's fins. The coefficients of heat convection for the processes between the fins and the airflow calculated by temperature field in the fins. Processes have been studied in "cooling" and "heating" regimes. The values of the coefficients obtained on the basis of simulations and by criterion equations, are compared. [ABSTRACT FROM AUTHOR]

Due to ample engineering applications, flow in a curved duct has become one of the most challenging research fields of fluid mechanics. In this paper, a computational numerical study of flow and heat transfer through a curved rectangular duct of various aspect ratios has been analyzed by using a spectral method and covering a wide range of the pressure gradient parameter, the Dean number 0 < Dn ≤ 1000 for the Grashof number Gr=1000. Unsteady solutions are obtained by time evolution calculations for the aspect ratios ranging from 1 to 3 with constant curvature 0.5. The outer wall of the duct is heated while the inner wall is in normal temperature, the top and bottom walls being thermally insulated. The main concern of this paper is to investigate the effects of aspect ratios on time-dependent solutions such as steady-state, periodic, multi-periodic or chaotic solution, if Dn is increased. For square duct flow, it is observed that there appears steady-state solution whether Dn is small or large. For rectangular duct of aspect ratio 2, however, the steady-state solution turns into chaotic solution, if Dn is increased. For aspect ratio 3, on the other hand, the steady-state solution turns into chaotic solution via periodic or multi-periodic flows. To justify the flow transition from one state to another, phase portrait of the time evolution results are obtained. Secondary flow patterns and temperature profiles on the flow characteristics are also obtained. Nusselt numbers are calculated as an index of convective heat transfer, and it is found that convective heat transfer is significantly enhanced by the secondary flow and as the flow becomes chaotic heat transfer occurs substantially. Finally, our numerical results are validated with experimental investigations and it is found that there is a good agreement between the numerical and experimental data. [ABSTRACT FROM AUTHOR]

In the paper, one parabolic-type boundary value problem is solved for determining the temperature field of the raw cotton and air components in drum dryers. In the proposed model, convective heat transfer is used according to Newton's law and the evaporation of moisture from the components of raw cotton (seeds, fiber) and the influence of air velocity are taken intoaccount. The resulting system of Galerkin's differential equations is solved by the finite-difference method in time. It is shown that the approximate solution is estimated according to Galerkin method in Sobolev space. The numerical results of the considered problem are obtained by the Bubnov–Galerkin method. A comparative analysis is carried out with experimental data. It is shown that the proposed mathematical model and its numerical algorithm adequately describe the drying process of raw cotton. [ABSTRACT FROM AUTHOR]

This paper reports a numerical study on mixed convection of thermo-dependent shear-thickening fluids combined with thermal radiation effect in a lid-driven square cavity. The cavity is uniformly heated / (cooled) from the left / (right) while the horizontal walls are thermally insulated. The finite difference method is used to solve the full governing equations for which the Boussinesq approximation is adopted. Effects of the governing parameters, namely, Richardson number and the Pearson number on the flow and heat transfer are analyzed. It has been found that the augmentation of Richardson number decreases the heat transfer and enhances the convective flow. [ABSTRACT FROM AUTHOR]

As with the development of heat exchangers, especially in the fields of energy and microelectronics, where the mini-channel used in heat exchanger operations is used, as increasing the efficiency of heat exchangers depends on transferring the largest amount of heat to and from the used band. To increase this transfer, obstacles must be used to improve heat transfer, as these barriers disturb the used fluid and increase heat transfer by convection. In this research paper, a mini-channel containing obstacles of variable thickness was used to study the extent of their effect on heat transfer and its strength to withstand the flow pressures in the mini-channel and prevent its deformation. The results proved that with the increase in the thickness of the obstacle, it increases its strength to withstand stresses but at the same time reduces its strength in convective heat transfer. The reason for this is that the increase in the thickness of the obstacle increases the area for heat transfer and thus increases the resistance and heat and prevents heat transfer significantly. [ABSTRACT FROM AUTHOR]

In this paper, the onset of magnetohydrodynamic convective instabilities in binary nanofluids is theoretically studied under the influence of thermodiffusions and nanoparticles. In order to investigate the convective instabilities, a physical system of Water-Lithium bromide based binary nanofluid layer with a vertical magnetic field is modeled by highly nonlinear partial differential equations and the expression of thermal Rayleigh number is analytically derived using linear stability analysis. The enhancement of convective heat transfer in the system is examined by calculating the heat transfer coefficient. Water-Lithium bromide based silver, copper and alumina, the three binary nanofluids are taken and the effect of nanoparticles on stability of the system and heat transfer coefficient is analyzed by introducing addition factor analysis. The impact of nondimensional parameters involved in the expression of Rayleigh number on the onset of convective instabilities is represented graphically. The dependence of size of convection cells on nondimensional parameters is also discussed. It is found that increase of the magnetic Chandrasekhar number is to decrease the size of convection cells. The size of convection cells is independent on volume fraction of nanoparticles, Lewis number, thermodiffusions of nanoparticles and solute. Moreover, the magnetic Chandrasekhar number and Lewis number have stabilizing effect on the system. The volume fraction of nanoparticles has destabilizing effect. Thermodiffusion of nanoparticles and solute have dual performance on the stability. They have stabilizing effect if δ4 < −1 and have destabilizing effect if δ4 > −1. Their performance is immaterial if δ4 = −1. [ABSTRACT FROM AUTHOR]

The paper presents the numerical simulation of natural convection heat transfer of air inside an enclosed cavity which can be helpful to find out the critical width of insulation in air insulated walls seen in residential buildings and industrial furnaces. Natural convection between two walls having different temperatures have been simulated using ANSYS FLUENT 12.0 in both steady and transient conditions. To simulate different heat transfer and fluid flow conditions, Rayleigh number ranging from 10³ to 105 has been maintained (i.e. Laminar flow.) In case of steady state analysis, the CFD predictions were in very good agreement with the reviewed literature. Transient simulation process has been performed by using User Defined Functions, where the temperature of the hot wall varies with time linearly. To obtain and compare the heat transfer properties, Nusselt number has been calculated at the hot wall at different conditions. The buoyancy driven flow characteristics have been investigated by observing the flow pattern in a graphical manner. The characteristics of the system at different temperature differences between the wall has been observed and documented. [ABSTRACT FROM AUTHOR]

Mainly consider the heat conduction between the layers of fabric, the thermal convection between the fabric and the air to establish the model of this paper. Firstly, the heat conduction equation between multilayer fabrics is constructed by the law of conservation of energy and Fourier's law; then, the heat convection equation between the fabric and the air is expressed by Newton's cooling formula; Finally, the thermal conductivity, temperature boundary conditions and temperature load between the fabrics of each layer were determined, and a heat transfer model conforming to the external environment—fabric (I~III)—air layer—human skin system was established. Considering the wide application of finite element in heat transfer, we use ANSYS heat transfer module to calculate the temperature distribution of each layer of the system by using transient thermal analysis method. The simulation results are well fitted to the actual experimental results, and the temperature of each layer is generated. Distribution. [ABSTRACT FROM AUTHOR]

Nanofluid is a novel industrial fluid that has the potential to improve heat exchanger performance. This paper presents an experimental study on the forced convective heat transfer of a graphene oxide nanofluid composed of water/Ethylene glycol and various volume percentages of GO nanofluid (0.5–2) percent passing in a cylindrical shell and tube heat exchanger with various baffle angles. Counter flow is investigated in turbulent flow conditions. The influence of heat transfer rate, entropy development, and overall heat transfer coefficient in heat exchangers with various baffle angles. The above-stated factors of the heat exchanger were governed by conventional correlations using nanofluids. Among the different reformed baffle angles, cylindrical shape nanoparticles performed best in factors of heat transfer rate and overall heat transfer coefficient. The overall heat transfer coefficient of cylindrical shape particles with 120 baffle angle is found to be 15%, 24%, and 30% higher than 240, 360baffle angles, in consistent to 1.5 vol. percent of GO nanofluid. Heat transfer is also found to be greater for cylindrical shapes at 120baffle angle than for other baffle angles. Entropy development, on the other hand, decreases with increasing volume percentage for all baffle angles. [ABSTRACT FROM AUTHOR]

This study investigates heat transmission and thermal performance factor characteristics in a tube with coil wire and twisted tape inserts using air as the working fluid. This study investigates heat transmission and thermal performance factor characteristics in a tube with coil wire and twisted tape inserts using air as the working fluid. The goal of this research is to improve forced convection heat transfer in tubes with and without swirl inserts and coil wire inserts for air Reynolds numbers ranging from 10.328×103 to 11.769×103. The impacts of different parameters of heat transfer are considered in this work with heat flux are constant conditions of 600 W/m2 and 800 W/m2 with using the coil wire and twisted tapes with three ratios (y/w = 3, 4 and 5). The test section is a horizontal annular passage with outer diameter 10 cm. The results showed that using coil wire inserts to improve heat transfer coefficient factors in tubes resulted in local heat transfer coefficient percentages of (5.1%) to (7.8%) with heat flux are constant conditions of 600 W/m2 and 800 W/m2, respectively. While tube with swirl inserts provide local heat transfer coefficient percentages of (3.6% to 6.1%) for heat fluxes (600) W/m2 and (800) W/m2, respectively. The obtained results demonstrate that as the twisted ratio (y/w) decreases, the mean Nusselt number and heat transfer coefficient in the tube with twisted tape and coil wire rise. Experimental results is shown, heat transfer coefficient for the coil wire when compared with that of swirl inserts tube were ranged between (10.6%) to (16.5%) and (11.5%) to (17.3%) for the heat flux (600) W/m2. [ABSTRACT FROM AUTHOR]

External combustion is a phenomenon where the flame flares out of the window and burns outside. Because of the particularity of the ship's cabin structure, there is a great danger in the external combustion. In this paper, the numerical calculation and analysis of three kinds of low ceiling ship cabin fire are analyzed based on the large eddy numerical simulation technique. Through the analysis of temperature, flue gas velocity, heat flux density and so on, the external combustion phenomenon of fire development is calculated. The results show that when external combustion occurs, the amount of fuel escaping decreases with the roof height. The temperature above the window increases with the height of the ceiling. The heat flux density in the external combustion flame is mainly provided by radiation, and convection is only a small part; In the plume area there is a time period, in this time period, the convective heat flux density is greater than the radiation heat flux, this time with the ceiling height increases. No matter which ceiling height, the external combustion will seriously damage the structure of the ship after a certain period of time. The velocity distribution of the three roof is similar, but with the height of the ceiling, the area size is also increasing. [ABSTRACT FROM AUTHOR]

Diurnal variations of external air temperature and solar radiation produce nonstationary thermal fields in a building enveope that cause thermal stresses in it. A study was conducted of the composite building envelope of the type used in constructing buildings on permafrost. In this paper we describe the results of mathematical modeling of thermal stresses of the envelopment. [ABSTRACT FROM AUTHOR]

This paper displays the execution of a numerical investigation of conjugate pure mixed convection heat transfer inside a square cavity with a circular rotating cylinder placed at the center of the cavity. Both top and bottom walls of the cavity are considered to be insulated, whereas the vertical walls are kept isothermally cooled. Besides, the rotating cylinder plays the simultaneous role of both heat conducting element and heat generating source. The numerical simulation is performed to solve the governing Navier-Stokes and energy equations using Galerkin finite element method. Both counterclockwise and clockwise rotations of the cylinder are taken into account along with the simultaneous variation of Reynolds and Grashof numbers, and the change of diameter of the cylinder. The analysis has been accomplished in terms of streamline and isotherm plots, the distribution of average Nusselt number of the heated cylinder surface and average temperature of the cavity. The findings of the present study reveal that variations of governing parameters and the size of the cylinder significantly contribute towards the thermal performance through drastically change of flow pattern and thermal field. However, the direction of rotation of the cylinder has insignificant effect on the characteristics of pure mixed convection heat transfer inside the cavity. [ABSTRACT FROM AUTHOR]

Methodic of a heat losses amount determination to surroundings from washing machines and dryers is described in this paper. A working substance in these machines is heated above ambient temperature of for their working process. An operational temperature inside these machines achieve till 90°C during working cycle. A measuring method of necessary parameters for the heat losses is described, i.e. measuring technique of outside surface temperature, gas and steam exhaust amount and temperature from working space and surroundings temperature. There is also described a calculation technique of convection and radiation heat outlet from outside surface and gas flow heat losses to the surroundings. This is performed by utilisation of measured values of described parameters. The result is the amount heat losses determination to the surroundings. [ABSTRACT FROM AUTHOR]

The paper dealt with an experimental investigation for mini vertical tube through study the transfer of CO2 heat convection at supercritical pressures. The dimensions of tube were 4mm and 10mm for diameter and length respectively. Many parameters have been measured to investigate the heat transfer convection which are; coefficients of heat transfer, temperatures of fluid bulk, temperatures of wall, rate of mass flow, temperature of inlet and flux of heat. The collected results showed that the heat transfer by convection has been affected by CO2 heat buoyancy and thermos-physical characteristic. On the other hand, the proportional relationship between heat transfer by convection and mass flow rate not fixed sometimes when the mini tube being empty. Moreover, the main influences on the heat transfer by convection were due to temperature of the inlet, flux of the heat and rate of the mass flow. [ABSTRACT FROM AUTHOR]

The paper dealt with an experimental investigation for mini vertical tube through study the transfer of CO2 heat convection at supercritical pressures. The dimensions of tube were 4mm and 10mm for diameter and length respectively. Many parameters have been measured to investigate the heat transfer convection which are; coefficients of heat transfer, temperatures of fluid bulk, temperatures of wall, rate of mass flow, temperature of inlet and flux of heat. The collected results showed that the heat transfer by convection has been affected by CO2 heat buoyancy and thermos-physical characteristic. On the other hand, the proportional relationship between heat transfer by convection and mass flow rate not fixed sometimes when the mini tube being empty. Moreover, the main influences on the heat transfer by convection were due to temperature of the inlet, flux of the heat and rate of the mass flow. [ABSTRACT FROM AUTHOR]

Heat dissipation from electronic devices is a crucial demand to keep their rated performance. Finned heat sinks are one of the efficient routes to dissipate the generated heat. This paper studies the performance of forced convective heat transfer from different shapes and arrangements of micro heat sinks. Ten designs of the micro heat sinks, included novel designs of micro fins, have been experimentally and numerically investigated in a rectangular air flow channel with Reynolds number ranging from 2000 to 11000. Laser etching technique has had been used in manufacturing the micro heat sinks while the CFD analysis have been conducted finite element method implemented in COMSOL Multiphysics. Results show that the proposed designs can significantly improve the fluid dynamic through the micro heat sink surface and thus the heat transfer performance. The enhancement in thermal transmittance because fluid-wall interaction has been proven to be effective in many designs in this study without relying on the contribution of the increase in the surface area. Therefore, this study provides significant rules to the design of micro-structured heat sinks for enhancing the heat transfer performance. [ABSTRACT FROM AUTHOR]

Radiators are heat exchangers which are used for cooling and heating by means of transferring the thermal energy from one medium to another. The most radiators are developed to function in the automobiles, buildings, and electronics. Despite the name, most radiators transfer their huge bulk of heat via convection method. Automobile radiator has a main function of cooling the engine by passing the coolant through the cylinder water jackets. The main objective of the project is to design a radiator fin and assign aluminum alloy1060 and copper brass alloy 260, Titanium alloy grade 9 materials to find out the better design configuration for radiator fin and better material for heat transfer. Analysis is carried out to find the heat transfer through the radiator. Improvement of the heat transfer rate is very important phenomenon for getting better efficiency. Designing of radiator fins is developed in solid works 2016 and analysis is carried out in ANSYS R14.5. [ABSTRACT FROM AUTHOR]

In the Fire Safety Engineering subject, one of the basic phenomena is fire spread on around an object that close to heat source because of the heat transfer process. At high temperature, radiation thermal have a significant effect on an exposed object. There are 3 kinds of characteristic of radiation, which are reflection, absorption, and transmission. Their characteristics are more convenient to learn if there are experiment tools or learning facilities that used radiation to be the main process. Therefore, this research has the objective of designing and built experimental tools used that process and it refers to radiometer. The radiometer is used to study the radiative heat transfer phenomenon in which heat flux emitted from a heat source is measured by using a heat flux sensor as the measurement instruments. Compared to existing radiometer apparatus, the design of this radiometer has some advantages like multiaxis features, user-friendly, portable, and low-cost manufacture. There are some additional features in radiometer likes variation of measurement range in x, y, and z-axis, measurement of view factor, measurement of tilt plane to acknowledge convection effect to heat transfer process, and using flat radiant heater. In this paper, the outcome is the design of a radiometer that can measure heat flux of thermal radiation and suits the study literature. [ABSTRACT FROM AUTHOR]

In this article, attention was paid to the mathematical modeling of the plasma temperature field under boundary conditions of the third kind. The simulation of the thermal process is based on the numerical integration of the thermal conductivity equation. This takes into account the change in the thermal conductivity of the plasma and convective heat transfer. Based on the obtained result, the behavior of the temperature field is analyzed. [ABSTRACT FROM AUTHOR]

In this paper the CO2 emission and thermal stability in a long cylindrical pipe of combustible reactive material with variable thermal conductivity are investigated. It is assumed that the cylindrical pipe loses heat by both convection and radiation at the surface. The nonlinear differential equations governing the problem are tackled numerically using Runge-Kutta-Fehlberg method coupled with shooting technique method. The effects of various thermophysical parameters on the temperature and carbon dioxide fields, together with critical conditions for thermal ignition are illustrated and discussed quantitatively. [ABSTRACT FROM AUTHOR]

The aim of this paper is to analyze the influence of flue gas flow on the heat exchange in experimental devices. The authors focused on the analysis of combustion gases produced by combustion of natural gas at various enrichment of the oxidizing agent by means of oxygen. By analyzing the flue gas flow, it is possible to detect changes in velocity fields at a given concentration of oxygen in the oxidizing agent. In the flow analysis, a mathematical model of an experimental device was developed in the ANSYS program, which served to visualize the change of velocity fields for the whirling burner mouth. [ABSTRACT FROM AUTHOR]

KPH field is one of the geothermal working areas located in Indonesia. Several geoscientific studies have been performed to assess the prospect of the field's resources. This paper aims to determine the potential and characteristics of the KPH geothermal field system using chemical methods and natural isotopes. The analysis was performed on the manifestations spread over in eight different places. Based on the analysis, this field has two geothermal systems. Both systems were classified as having a high temperature from the calculation of CO2−Ar-H2 gas geothermometer. All water manifestation originated from meteoric water, which underwent interaction between fluid and rock before it appears to the surface. The calculation of geothermal potential using convection heat loss method showed a result of 12.55 MWth. KPH field is very prospective to be developed with the prospect area based on the soil survey located around KBA crater, SMP, and BBG manifestations. However, further studies are required on the existence of two geothermal systems. [ABSTRACT FROM AUTHOR]

This paper presents the computational results from simulations performed on a small-scale cabinet-type forced convective dryer for food product drying. The forced convective dryer is designed in the form of a drying cabinet, with four trays positioned diagonally to each other within the drying chamber. The trays are designed and simulated as meshed trays to allow better observation of the air-flow and moisture content transport path within the dryer during operation. Air-flow is provided by eight heated-air inlets with four on each of two sides, with two inlets providing heat for each tray. Inlet temperature is kept within the range of food product drying temperature. Boundary conditions of the dryer are also set to simulate the actual dryer such as wall-material and initial conditions. Computational simulations performed on the forced-convective dryer show the air-flow path within the drying chamber in contour plots. Iso-plots of the air-flow magnitude are also shown to illustrate the heated air-flow from the inlets through to the outlet. These plots illustrate the path for moisture content removal from the food product to the outlet. The contour plots also show areas where possible improvement can be implemented. The improvement can also involve alternative boundary conditions, trays positioning and heated-air inlets placement. With the implementation of these improvements a more optimized dryer can be achieved. [ABSTRACT FROM AUTHOR]

During material forming process (metal, glass, polymer), one stage is the solidification of the material, from a bulk melt part. Occurrence of solid particles in the melt material may alter the properties of the final product, as aggregation of particles potentially induces a local weakness (bad shape, mechanical or thermal properties, for example). Considering one particle, a wide range of thermal and dynamic phenomena can be observed: a particle settling is mainly due to Archimedes forces. Free convection due to gravity effects can increase the fluid flow (which is defined as an assisting flow) or may limit it (defined as an opposing flow). A high fluid-particle relative velocity also implies forced convection. The competition between the two thermal phenomena (so-called mixed convection) widely influences the particle transport. Many works have studied the fluid velocity field induced by a cylinder or a spherical particle in a isothermal medium, and have highlighted transitions of flow regime (a laminar flow at low velocity, a deviation in the particle transport at a moderate velocity and various flow structures at a high velocity). Some studies have taken into account heat transfer between the particle and the fluid, and focused on the thermal effects upon the particle fluid velocity. Experiments are difficult (or impossible) to lead, since some materials (like metals for example) do not allow visualizing the particle in the melt fluid. We propose in the present study to carry out the numerical 3D-simulation of a cold particle submitted to a fluid flow, in order to link the fluid-particle thermal transfer and the fluid flow properties. A volume of fluid method is used, on a fixed Cartesian grid to determine the particle transport, the fluid flow and heat transfers in both the fluid and the particle. The domain must be large enough to avoid wall effects. The mixed convection is quantified by the Richardson number (Ri). The aim of this paper will consist in studying the influence of Ri (by modifying the particle temperature) and to link this parameter to the flow regime and heat transfer. [ABSTRACT FROM AUTHOR]

MHD mixed convection has been one of the center points of attraction to the heat transfer engineers for many years. In this paper, unsteady mixed convection in a T-shaped ventilated cavity filled with single phase Ferrofluid (Fe3O4-water) is analyzed thoroughly under externally applied magnetic field. The top wall of the cavity is maintained at constant cold temperature while the bottom wall of the cavity is sinusoidally heated along with adiabatic vertical walls. For pure mixed convection (Ri = 1), two different inlet velocity profiles namely uniform and Poiseuille are considered in this analysis and numerical solution is obtained for each type of inlet velocity profile, considering constant solid volume fraction of nanofluid (ф = 0.05) and Hartman number (Ha=25). Qualitative analyses are presented in terms of streamline and isotherm contours and quantitative analyses are presented through Nusselt number (Nu) and average temperature (θ av) inside the cavity. It has been observed that, Nu decreases over a certain range of time and then increases very slowly. Also, Nu is a little higher in case of uniform inlet flow profile compared to Poiseuille flow profile. Interestingly, convective heat transfer rate decreases and conduction heat transfer becomes dominating, due to the externally applied magnetic field. [ABSTRACT FROM AUTHOR]

In this research microwave heating is applied to analogous experiments modeling Earth's mantle dynamics. This paper presents the experimental setup for laboratory convection experiments and the optimization procedure towards the desired result (i.e. uniform heating of the probe and long-term power stability). The schematic diagram of the microwaves power generator is detailed and presented together with the methods allowing to control the microwaves power stability. The biological protection of the users related to the microwaves leakage is also considered in the experimental setup design. [ABSTRACT FROM AUTHOR]

In this paper, we discussed the peristaltic MHD flow of an incompressible and electrically conducting Williamson fluid in a symmetric planar channel with heat and mass transfer under the effect of inclined magnetic field. Viscous dissipation and Joule heating are also taken into consideration. Mathematical model is presented by using the long wavelength and low Reynolds number approximations. The differential equations governing the flow are highly nonlinear and thus perturbation solution for small Weissenberg number (We < 1) is presented. Effects of the heat and mass transfer on the longitudinal velocity, temperature and concentration are studied in detail. Main observations are presented in the concluding section. The streamlines pattern is also given due attention. [ABSTRACT FROM AUTHOR]

There are two major classifications of augmenting heat transfer: passive and active. In the active technique, external energy is supplied to the fluid by mechanical rotation of the surface, the mixture of fluid with mechanical accessories, etc. On the other hand, the passive technique does not use any power. The technique includes twisted tapes, coiled wire, rough surfaces, extended surfaces, surfaces coated devices to generate turbulence. Many inserts induce secondary flow favoring thermal heat exchange. This review article will focus on enhancing the heat transfer and associated pressure drop with the flow boiling using coiled wire as a turbulent promoter. The insert breaks the boundary layer of the fluid at the solid-liquid interface near the inner wall of the pipe. Insert also creates turbulence and rotary motion within the test section, this makes turbulent flow leading to better heat transfer by convection. Helical wire produces a helical flow to the periphery superimposed on the main axial flow. The augmented heat transfer with two-phase flow boiling using coiled wire studied experimentally in recent years by many investigators. Scanty literature is available on analytical work and numerical simulation. However, the reliability and error band does not quantify such work for system design. Most of system design and selection is based upon experimental data and proposed correlations for heat transfer and pressure drop. In this paper, a comprehensively relative study of such work is critically reviewed and presented. [ABSTRACT FROM AUTHOR]

The paper presents a mathematical modeling of nonstationary laminar Bénard-Marangoni convection of a viscous incompressible fluid moving in an infinite band. The main attention is paid to the study of the position and displacement of the stagnation point of the solution with time, the appearance and disappearance of counterflows. It is shown that the overdetermined initial boundary value problem within the here presented class of exact solutions of the Oberbeck-Boussinesq equations is reducible to the Sturm-Liouville problem. The hydrodynamic fields indicating the presence of counterflows in the fluid and their change during fluid acceleration are analyzed with the use of a computational experiment. [ABSTRACT FROM AUTHOR]

We have presented the numerical results of calculations obtained with the help of a model of the ZnS combustion synthesis in a wet inert gas environment. The model was a modification of the model of the ZnS combustion synthesis on argon developed earlier. The results let us numerically and with the high accuracy estimate separately the heat transfers by both convection, conduction and thermal radiation during the combustion under the conditions stated in the heading. As a result, we are not only able to compare the heat transfers by the convection, conduction and thermal radiation, but also investigate in details the reason of much smaller heat transfer by radiation with respect to convection in the combustion system considered. On one hand, our results agree with data on relative values of heat transfer by convection, conduction and radiation, and on the other hand, they allow us to specify accurately the reason of a smallness of heat transfer by radiation more precisely and reasonably. We have concluded that this is a hot thin cloud of water vapors that is formed in a close vicinity of the igniter, absorbs radiation and prevents the other part of green mixture both from ignition by radiation and the subsequent propagation of the combustion on the basis of radiation heat transfer. In the presented paper a modification of the previous research results was carried out which allows taking into account the influence of water vapor on the radiation heat transfer process during the synthesis of zinc sulfide. At sufficiently high concentration of vapors the model explains the abnormally low values of effective gas permeability coefficients calculated without taking into account the indicated effect. [ABSTRACT FROM AUTHOR]

In this paper, the effect of g-jitter on double diffusion by mixed convection past an inclined stretching sheet is studied. The velocity, concentration and temperature of the sheet are assumed to vary linearly with x, where x is the distance along the sheet. The resulting non-similar boundary layer equations are solved numerically using an implicit finite-difference scheme. Numerical results on the flow and heat and mass transfer characteristics are presented graphically for different values of amplitude, buoyancy ratio parameter and inclination angle. Results show that rate of heat and mass transfers increase but reduced skin friction decreases as the angle of inclination increases. It is noted that as buoyancy ratio parameter increases, rate of heat and mass transfer as well as reduced skin friction are decreases. [ABSTRACT FROM AUTHOR]

Appropriate modeling of heat transfer from the polymer material to the injection mold is essential to achieve accurate simulation results. The heat transfer is commonly modeled using convective heat transfer and applying heat transfer coefficients (HTC) to the polymer-mold-interface. The set HTC has an influence on the results for filling pressure, cooling performance and shrinkage, among others. The current paper, presents a new strategy to measure HTC in injection molding experiments using Newtons law of cooling. The heat flux is calculated out of demolding heat (measured by means of calorimetry), injection heat (measured by means of an IR-sensor), cooling time and part mass. Cavity surface area, average mold surface temperature and average part surface temperature lead to the HTC. [ABSTRACT FROM AUTHOR]

In this paper we present scaling of large-scale quantities like Peclét and Nusselt numbers, and the dissipation rates of kinetic energy and entropy. Our arguments are based on the scaling of bulk quantities and earlier experimental and simulation results. We also present the inertial-range properties of spectra and fluxes of kinetic energy and entropy. [ABSTRACT FROM AUTHOR]

In this paper the impurity distribution is computed in a 2-D domain, which represents the meniscus and a part of the capillary channel. The model takes into account the pulling rate, thermal convection, Marangoni convection, molecular diffusion and thermo diffusion. Numerical illustration is given for Al doped thin Si sheet and the contribution of each effect is evaluated. The novelties consist in the fact that the 2-D domain is obtained by computation using the Young-Laplace capillary surface equation and the heat transport equation and in the inclusion of the thermo diffusion effect in the impurity distribution equation, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the effects of suction and injection parameters on magnetohydrodynamic (MHD) mixed convection stagnation point flow are studied numerically. Using appropriate similarity transformations, the governing system of partial differential equations is transformed into a system of ordinary differential equations which are then solved using the shooting method. Numerical results are obtained for the velocity, temperature and concentration profiles. The results show that the suction and injection parameters affect the skin friction coefficient as well as the local Nusselt number for both assisting and opposing flows. The suction parameter increases the skin friction coefficient and the local Nusselt number while the opposite behavior is observed for the injection parameter. [ABSTRACT FROM AUTHOR]

In this paper, the steady mixed convection boundary layer flow over a solid sphere with a constant surface temperature embedded in a porous medium saturated by a nanofluid containing both nanoparticles and gyrotactic microorganisms in a stream flowing vertically upwards for both cases of a heated and cooled sphere, is numerically studied. The resulting system of nonlinear partial differential equations is solved numerically using an implicit finite-difference scheme. By considering the governing parameters, namely the mixed convection parameter λ, the bioconvection Lewis number Lb, the traditional Lewis number Le, the bioconvection Péclet number Pb, the buoyancy ratio Nr, the bioconvection Rayleigh number Rb, the Brownian motion Nb and the thermophoresis Nt, the numerical results are obtained and discussed for the local density number of the motile microorganisms as well as the velocity, temperature, nanoparticle volume fraction and density motile microorganisms profiles. [ABSTRACT FROM AUTHOR]

Generalized hydrodynamic equations (GHE) proposed by Alexeev (1994), have been explored for simulations of viscous flows for a wide range of problems and flow parameters, including high Reynolds numbers flows with thin boundary layers. These GHE is not a turbulence model, and no additional equations are introduced. Spacial fluctuations (small flow scales) can be successfully captured with GHE, and the derived small scale of turbulent flow compares well with observed one in the experiments by Koseff and Street (1984). In this paper, we review numerical solutions using GHE for several viscous flow problems and compare numerical results with experimental data for the cases we considered in the range of Reynolds number from Re = 10-6, to 3200, and to 1,000,000. The method is reviewed and numerical solutions are compared with the experimental data for a 3D driven cavity flow at Re = 3200 and 10,000, 2D backward facing step flow at Re = 44,000, 2D channel flow at Re number up to 106; and a 3D thermal convection in a cylinder at Ra = 1000 to 150,000. Comparison with the analytical asymptotic solution is provided for a thermal convection, in the electrically conducting fluid suppressed by a strong magnetic field at Hartman numbers Ha up to 20,000 (Re = 10-5). In all the cases considered, GHE results compare favorably with experimental data. 2D and 3D Naver-Stokes solutions and k - [variant_greek_epsilon] model solutions are also provided, and they are outperformed by GHE results. [ABSTRACT FROM AUTHOR]

Rapidly emerging micro-electro-mechanical devices create new potential microfluidic applications. A simulation of an internal and external gas flows is important for their design. For small Knudsen number Kn < 0.1 (Kn = l0/L, where l0 is the mean free path of the gas molecules and L is the characteristic length), a continuum approach based on modified Navier-Stokes-Fourier or extended hydrodynamic continuum models with corresponding velocity-slip and temperature-jump boundary conditions is still applicable and, respectively, preferable. We restrict ourself to the use of Navier-Stokes-Fourier continuum model. A development of the algorithm to solve a specific class of problems is closely related to numerical schemes used for approximation of equations terms. Higher-order approximation schemes can reduce the number of mesh nodes and respectively computational time, but it is possible to obtain physical unrealistic results. In this paper we study influence of some approximation schemes for convective terms over the spatial steps. It is compared upwind, central difference and total variation diminishing (TVD) schemes Min-Mod, QUICK and SUPERBEE. A test case is gas flow past a square in a microchannel at subsonic speed (Mach number M = 0.1) and supersonic speed (M = 2.43), available in a literature. [ABSTRACT FROM AUTHOR]