A numerical study has been carried out to investigate the combined forced and natural convection heat transfer in a differentially heated 3D obstructed cavity with a thermally insulated rotating circular cylinder. The cavity has a hot stationary bottom wall and a cold top lid-driven wall, and all the other walls completing the domain are motionless and adiabatic. The simulations are performed for different Reynolds numbers, Re = 5000, 10000, 15000 and 30000, and for dimensionless rotational speeds of the cylinder, 0 ≤ Ω ≤ 10. The performance of two turbulence methods, Large Eddy Simulation (LES) and Unsteady Reynolds-Averaged Navier-Stokes (URANS), has been evaluated in this research. The flow and thermal fields are studied through flow vectors, isotherm contours and iso-surfaces temperature, as well as through the average Nusselt number (Nuav) and velocity components. The results demonstrate clearly that the flow patterns and the thermal fields are influenced strongly by increasing either the rotating cylinder speed or the Reynolds number. Furthermore, both LES and URANS solutions can capture the essential feature of the primary eddies in the cavity. But this study has shown convincing evidence that only the LES method can predict the structure details of the secondary eddies that have profound effects on the heat transfer behaviour within the enclosure.
7In an office room, many factors affect the pattern of airflow, thermal comfort, indoor air quality and 8 energy saving. In this study, the effects of the location of exhaust diffusers where the warm and 9 contaminant air is extracted and their relation to room heat sources on thermal comfort and energy 10 saving were investigated numerically for an office served by a displacement ventilation system. The 11 indoor air quality in the breathing level and the inhaled zone were also evaluated. The contaminants 12 were released from window and door frames in order to simulate the contaminants coming from 13 outside. The amount of energy consumption and the indoor thermal environment for various exhaust 14 locations were investigated numerically using the computational fluid dynamics techniques. The 15 results showed that the thermal indoor environment, thermal comfort, quality of indoor air and energy 16 saving were greatly improved by combining the exhaust outlets with some of the room's heat sources 17 such as ceiling lamps and external walls. In particular, a 25.0 % of energy saving was achieved by 18 combining the exhaust diffuser with room's ceiling lamps. In addition, locating the exhaust diffuser 19 near the heat sources also reduced the cooling coil load by 13.8 %. The risk of a large difference in 20 temperature between the head and foot levels, increased particle concentration in the occupied zone, 21 as well as increased energy consumption was also clearly demonstrated when the exhaust and 22 recirculated air outlet (return opening) were combined in one unit in the occupied boundary area that 23 2 is located at 2m away from the occupants. Thus, for the optimum energy saving and better indoor 1 environment, the combination of the indoor heat sources with the exhaust outlet is necessary. 2
Mixed convection heat transfer in a two-dimensional trapezoidal lid-driven enclosure filled with nanofluids heated from below is numerically studied. The governing equations for both fluid flow and heat transfer are solved by using the finite volume method (FVM). The bottom wall of the enclosure is heated while the upper wall is cooled at lower temperature and the other two sidewalls are adiabatic. Four types of nanofluids (Al2O3, CuO, SiO2, and TiO2 with pure water) with nanoparticles volume fraction (ϕ) in the range of 1-4% and nanoparticles diameter in the range 25-70 nm were used. This investigation covers Richardson number and Reynolds number in the ranges of 0.1-10 and 100-1200, respectively. The trapezoidal lid-driven enclosure was studied for different rotational angles (Φ) in the range of 30˚-60˚, different inclination sidewalls angles (γ) in the range of 30˚-60˚ and various aspect ratios (A) ranged from 0.5-2. This investigation is also examined the opposing and aiding flow conditions. The results show that all types of nanofluids have higher Nusselt number compared with pure water. It is found that SiO2-water has the highest Nusselt number followed by Al2O3-water, TiO2-water, and CuO-water. The Nusselt number increases as the volume fraction increases but it decreases as the diameter of the nanoparticles of nanofluids increases. The Nusselt number increases with the decrease of rotational angle and inclination angle from 30˚-60˚ and with the increase of aspect ratio. The results of flow direction show that the aiding flow gives higher Nusselt number than the opposing flow.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.