Papers by Keyword: Enclosure

Abstract: Abstract. The topic of free convection thermal transmission through different geometrical shapes of enclosures is an engaging subject. It has caught the attention of the researchers during the last decades according to its significance in lots of engineering applications. Nuclear reactors, solar collectors, cooling electronic equipment, Oil wells, cooling electric components (as in the copper electric wires that are surrounded by the housing), and many industrial systems. Many parameters are discussed and analyzed to see their effect on the process of transferring heat such as: the effect of the geometrical shape, Nusslet number, and Rayliegh number. The studies were divided into seven categories based on the geometrical shape of the enclosure ( square , triangular, circular, trapezoidal, polygonal, elliptical, and wavy). The governing equations of the free convective thermal transmission were stated. The objective of this study is to collect the data from a large number of previous studies and compare them to reach a conclusion about the best results.

Abstract: Two-dimensional numerical studies were performed for investigation of the effect of thermophysical properties of solid walls on turbulent convective – radiative heat transfer in an air filled square cavity. The main attention was paid to the influence of thermal conductivity ratio1 ≤ κ_{1, 2} ≤ 1000 and an emissivity of internal surfaces of the solid walls 0 £ < 1 on velocity and temperature fields. Numerical results were obtained by means of the finite difference method. The effect of the governing parameters on the average Nusselt number has been defined. The obtained results provide better technical support for development and research of energy-efficient building materials

Abstract: Results from numerical investigation of laminar natural convection inside a differentially heated square enclosure with a thin baffle attached to the cold wall are reported. The effect of the baffles on the flow and temperature fields were analyzed for baffle lengths equal to 20, 35 and 50 percent of the width of the enclosure, attached at three locations for Ra = 10⁴, 10⁵, 10⁶ and Pr = 0.707. The presence of a baffle on the cold right wall affects the strength of the clockwise rotating primary vortex. Reduced flow and heat transfer are observed. Longer the baffle more pronounced the effect on the flow field. Secondary convection cells are seen between the baffle and the bottom wall for certain cases. Reduction in average Nusselt Number is observed on the cold wall with the baffle than the hot wall.

Abstract: A two-phase mixture model is used to study natural convection in a square cavity filled with CuO+H₂O nanofluids, in the hypothesis of temperature-dependent physical properties, assuming that Brownian diffusion and thermophoresis are the primary slip mechanisms between solid and liquid phases. The cavity is heated at one side and cooled at the opposite side, whereas the horizontal walls are assumed either both adiabatic, or the bottom heated and the top cooled. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. It is found that, owing to the effects of the slip motion occurring between solid and liquid phases, the rate of heat transferred across the cavity by the nanofluid in the heating-from-below configuration is remarkably higher than that transferred by the pure base liquid. Moreover, in this particular configuration the addition of nanoparticles to the base liquid generates periodicity in heat transfer. Additionally, the heat transfer enhancement is discovered to increase as the imposed temperature difference is increased, showing a smooth maximum at an optimal particle loading.

Abstract: Multi-Agent system (MAS) is used to control the radiation noise in a rectangular enclosure, which is surrounded by two flexible plates and four rigid plates. The noise is generateded by the vibration of the exciting flexible plane. A MAS is established to coordinate the active noise control method, and these agents are controlled by a coordination object which includes compete and cooperative rules. These agents are competitiveness, so the MAS can provide fault-tolerant capabilities for the control mechanism. Meanwhile, these agents are independent and modular, and can be used in “Plug-and-Play” control field. The formula is derivate to calculate the sound pressure in the enclosure when there some point forces applied on the flexible plates, and the simulation shows using MAS to control the noise in the cavity is effective.

Abstract: This paper analytically demonstrates the use of some point forces actuators applied on different flexible plates to reduce the radiated sound in the cavity. A rectangular enclosure involving two opposite flexible plates is considered. We want to get the dominant factors that impact the coupling effects and the noise reduction in the cavity with the ASAC method, so we make some point forces located on different plates and to compare their different control effect. The formula was derivate to calculate the sound pressure in the enclosure when there some point forces applied on the flexible plates, and then analyzed and get the simulation of the sound pressure level (SPL) response in the local cavity sound field. The paper indicated that applying distributed cooperative control method can get the better reduction of noise.

Abstract: Laminar natural convection heat transfer inside water-filled, tilted square and shallow cavities heated at one side and cooled at the opposite side, is studied numerically. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. Simulations are performed using the Rayleigh number based on the length of the heated and cooled sides, the height-to-width aspect ratio of the enclosure, and the positive tilting angle with respect to the gravity vector (which corresponds to configurations with the heated wall facing upwards), as independent variables. It is found that the heat transfer performance has a peak at an optimal tilting angle which increases as the Rayleigh number is decreased and the aspect ratio is increased. On the basis of the results obtained, a set of dimensionless correlations is developed.

Abstract: This study focuses on the analysis of algae growth when nitrogen is enough and phosphorus is different though the method of enclosure experiments. and to determine the influence of phosphorus for algae population structure. The results showed that the optimum value for algae grew is ρ_p=0.14mg·L^-1 in the different phosphorus concentrations, and algae grew better at phosphorus concentration more than 0.14mg·L^-1 than less than it. Community structure of phytoplankton has a little change between the experiments.The dominance of diatom is much larger than that of other phylum.The phosphorus can influence algae growth but has little effect on phytoplankton succession.A further research about the reason of phytoplankton succession in Xiangxi bay is needed.

Abstract: This paper presents an investigation into the active control of structural-acoustic coupled system of a rectangular enclosure involving two simply supported flexible plates. One of the two plates is driven by a point force. The locations of actuators are determined by considering contour plot of the optimal potential energy. The control mechanisms for this enclosure are analyzed when one, two and three actuators are applied on one of the plates. Results obtained demonstrate that the control mechanisms for Panel a are always modal restructuring; those for Panel b are dominantly modal suppression when a different number of actuators is applied to reduce the noise level.

Abstract: For enclosure noise reduction, limited discrete distributed control is an ideal choice when it is difficult to understand sound-structure coupling characteristics accurately. An enclosure medel of two flexible plates is established in this paper. Two secondary control channels are constructed by applying distributed force on flexible plate. In the basis of control problem decomposition a multi-agent system (MAS) structure is established and the coordination relationship between agents is regulated. The simulaition resultes show the Active Structure Acoustic Control based on MAS is effective. The MAS control method improves the extension of noise control system and can be used in “plug-and–play” control field to realize noise reduction. MAS is a better effective tool to realize the divide-and-conquer approach in enclosure noise control field.