EFFECT OF CAVITY RATIO ON HEAT TRANSFER BY FREE LOAD FROM HEATED PLATES UPWARD WITH CONSTANT HEAT FLUX

Many engineering and industrial applications always seek to find ways to dissipate heat from heated surfaces used in these industries. As it is involved in the cooling of electronic parts and electrical transformers, as well as the design of solar collectors, in addition to being a process of heat exchange between hot surfaces and the fluids in contact with them. Since most electronic devices or their parts are cooled by removing the heat generated inside them by using air as a heat transfer medium and in a free convection way, and the fact that heat transfer by free convection occurs in many fields, so there were many studies that dealt with this topic. The free load is generated by the buoyant force (Bouncy force) As a result of the difference in the density of the fluid adjacent to the heated surface due to the difference in temperatures between the fluid and the surface. The laminar flow along surfaces has been extensively studied analytically [1,2,3,4] In the horizontal, inclined and vertical case, whether by constant heat flux or constant surface temperature, there are also many experimental studies of heat transfer by free convection from horizontal, inclined and vertical surfaces with constant heat flux or constant surface temperature [5,6,7,8]. Some experimental studies have also been conducted on heat transfer by convection from heated surfaces in the form of a disk (ring)The outcome of these studies was to extract an exponential mathematical relationship between the average of Nusselt number and the Kirchhoff number or Rayleigh number and the following formula: (Nu=C(Ra) n It is one of the most suitable formulas for heat transfer by free convection from heated surfaces in all its forms and over a wide range of Rayleigh number . It is noted that not all of these studies dealt with the study of the effect of the cavity ratio on heat transfer by free convection from square-shaped surfaces, which is the form that is more applied in electronic devices. Therefore, the current research means studying the rate of change in the average of Nusselt number, which represents a function of the rate of change in the rate of heat transfer by convection, as well as studying the thermal gradient above the surface, and this was done through using three hollow surfaces in proportions (0.25,0.5,0.75) of the total area.

Non-Darcian-Bènard Double Diffusive Magneto-Marangoni Convection in a Two Layer System with Constant Heat Source/Sink

The problem of non-Darcian-Bènard double diffusive magneto-Marangoni convection is considered in a horizontal infinite two layer system. The system consists of a two-component fluid layer placed above a porous layer, saturated with the same fluid with a constant heat sources/sink in both the layers, in the presence of a vertical magnetic field. The lower porous layer is bounded by rigid boundary, while the upper boundary of the fluid region is free with the presence of Marangoni effects. The system of ordinary differential equations obtained after normal mode analysis is solved in a closed form for the eigenvalue and the Thermal Marangoni Number (TMN) for two cases of Thermal Boundary Combinations (TBC); these are type (i) Adiabatic-Adiabatic and type (ii) Adiabatic-Isothermal. The corresponding two TMNs are obtained and the impacts of the porous parameter, solute Marangoni number, modified internal Rayleigh numbers, viscosity ratio, and the diffusivity ratios on the non-Darcian-Bènard double diffusive magneto - Marangoni convection are studied in detail.

Обеспечение независимого регулирования температур агентов нагрева и охлаждения бездроссельной теплонасосной установкой при дифференцированном подводе тепла в процессе сушки семян зерновых

To ensure the food security of the country, it is necessary to harvest grain seeds annually by agricultural producers. Drying is the most important, energy-intensive and time-consuming post-harvest stage in seed preparation. At present, convective drying with a constant heat supply is the most widespread on the territory of the Russian Federation. To intensify the convective drying process, it is preferable to use the differentiation of heat supply. In order to implement these measures, the possibility of using a heat pump installation of an original design, developed by scientists of the Federal State Budgetary Educational Institution of Higher Education of the State Agrarian University of the Northern Trans-Urals, is presented. Keywords: SEED DRYING, DIFFERENTIATION OF HEAT SUPPLY, CONVECTIVE DRYING, HEAT PUMP INSTALLATION, INTENSIFICATION

Analysis and Research on Cold Proof Design of Polar Marine Machinery

Polar marine machinery is an important equipment for China to participate in Arctic energy exploitation. The Arctic region is rich in natural resources and has a very important strategic position. As an important equipment for passage and exploitation of energy, its key technology is particularly important. As a special ship sailing in polar regions, polar ships generally adopt electric heat tracing measures due to the adverse environment in polar regions. The deck machinery and facilities shall be protected against cold. This paper mainly studies the convection of flat plate members under constant heat flow electric heating. The research results can be popularized and applied to the cold protection of most upper facilities of polar ships.

Simulation-based Study of Graphene-water Nanofluid flow through Microchannel Heatsink

This study presents a CFD analysis of the laminar flow of graphene-water nanofluid through a Silicon microchannel heatsink using commercial software ANSYS FLUENT. The microchannel has a rectangular cross-section of given dimensions, and the base of the heatsink is subjected to a constant heat flux. Simulations of the coolant flow are performed at different fluid inlet velocities for nanoparticle concentrations of 0%, 3% and 6% in the base fluid-Water. Results for temperature and pressure distributions in the microchannel heatsink are presented. The cooling performance of the MCHS improves significantly by increasing the flow velocity and enhancing the nanoparticle concentration in the coolant.