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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]

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]

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]

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]

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]

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]

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]

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]