Papers by Keyword: Area Ratio

Abstract: This study investigates the implications of the area ratio (AR) and Grashof number (Gr) on fluid flow properties and heat transfer due to mixed convection around heated trapezoidal blocks located concentrically inside a larger trapezium driven by a lid. The outer trapezium's upper and lower horizontal walls are moving in opposite directions. The model developed was solved using the finite element technique. The inner walls of the trapezium are retained at an isothermal temperature, while the slanted outer walls of the trapezium are perfectly insulated. The upper and lower walls of the enclosure are subjected to normalized sinusoidal temperatures. Grashof number in the range of 10³£Gr£10⁵ and area ratios ( ) of , and were investigated. The simulation outcomes are displayed as stream function, isothermal contours, and local Nusselt number. Considering the interval of for the inner block, the Nusselt number increase with diminishing area ratio for the upper wall, while the response of the lower wall to Gr variation is a function of the AR considered. At the bottom wall of the outer trapezium, results showed that the rate of heat transfer was not significantly affected by changes in area ratio. Furthermore, as the AR reduces, the heat transmission along the top wall of the outer trapezium improves with the Grashof number, with the least and peak heat transfer enhancements occurring at 50 % and 100 % percent of the wall length, respectively.

Abstract: Wind energy is the quickest growing sustainable energy resource in present energy crisis scenario. It has been considered as one of the most viable sources of environmental friendly energy. Starting investment cost of the wind turbine plant is exorbitant. Moreover, production cost of the wind turbine blade is about 20% of the wind turbine plant cost. It is fundamental to decrease the life-cycle cost of wind turbine plant by efficient utilization available wind speed. Optimized diffuser (Convergent divergent type and Convergent type) has been developed with highest possible pressure difference between inlet and exit of shroud, Area Ratio of inlet to exit section, wall length, incident angle and various flow qualities to enhance the available wind velocity considerably. The suitable tiny riblets on external layer of turbine blade have been introduced to lessen the skin friction drag force. Moreover, dual rotor blade with various rotor sizes for primary and secondary rotor, direction of rotor rotation, separation distance between them has been studied to augment wind turbine power generation and improvement in cut-in-speed. Moreover, comparative study will be conducted with standard (bare) wind turbine. Based on the above features, available wind speed increased significantly. In addition, various experiments and CFD analysis work still to be done to assess Diffuser based Wind Turbine model which is much closer to realistic product with available interaction. Due to the above additional features of the turbine system, the utilization of wind speed gets augmented with greater power production.

Abstract: A study on the flow and separation performance of supersonic gas separator is carried out through numerical simulation and experimentation. The effect of area ratio on the separation performance under low pressure ratio has been researched. The simulation results indicate that with an increase of the area ratio AR, the intensity of the shockwave increases and the location approaches the throat; Shockwaves are absent in the diverging section of the nozzle when area ratio is 1.063 and the pressure ratio is within 1.25-1.75, which reaches the highest separation performance. The calculated and experimental results also show that the separation performance is the highest and can reach 40.82% when pressure ratio is 1.75. The calculated values are in agreement with the experimental results.

Abstract: In this paper, a speeding-up inlet was developed to increase the free stream velocity in the marine current in order to increase the input energy of turbine. This study was conducted in the Hydrodynamics Laboratory at Zhejiang University of Technology. By using high-speed camera, acoustic Doppler velocimetry (ADV), the influence of area ratio and length-diameter ratio on rotational speed of the turbine was experimentally investigated. Experimental results showed that both area ratio and length-diameter ratio have significant influences on the rotational speed of marine current turbine.

Abstract: The spreading resistance is a very important parameter in the applications of heat sink. The design of electronic devices will fail without considering the influence of the spreading resistance. In this paper, a simple thermal model was simulated by Computational Fluid Dynamics software. Some factors, which have great influence on the spreading resistance, have been analyzed. The spreading resistance decreases significantly with the increasing of the area ratio between the heat source and the base-plate. While the ratio being 1, the spreading resistance reaches the mix value. The greater the thermal conductivity of heat sink, the lower the spreading resistance. With the increasing of the thickness of base-plate, the spreading resistance reduces. However, if the thickness exceeds the critical value, the spreading resistance will increase. And the spreading resistance reaches the mix value while the centers of heat source and the base-plate are overlapped.

Abstract: Hydraulic jet pump is one of the mixing-reaction equipments using high-speed jet for work force to deliver energy and mass of fluid. Many factors affect the efficiency of this pump, and the mechanism is very complex. The present work aims to study the influence of different hydraulic structures on the efficiency. Based on computational fluid dynamics, two-dimensional oil flow in hydraulic jet pump with different structural parameters (area ratio, throat length and spray distance) was simulated. Calculation results show that: area ratio determines the suction capacity, throat length determines the mixing efficiency, and spray distance determines the outlet pressure. Since numerical simulation method can reduce experimental expenses and design cycle, our approach may provide some references for safe design and engineering practice of hydraulic jet pump.

Abstract: Plastic deformation process resulting in ultra fine grained materials which are rapidly grasping applications due to their superior mechanical properties remain an area of continued research interest. Generally, the influence of die land length and web to flange ratio in grain refinement subsequent to plastic deformation process have not being adequately exploited especially in complex die opening geometries. In the present study, the effect of these parameters on extrusion pressure and morphological change in I-shaped die opening geometry is investigated and reported. A forward extrusion rig is designed and manufactured for the purpose of experimental investigation. The upper bound analysis shows that increasing die land length leads to increasing relative extrusion pressure. Optimum web to flange ratio of 0.45 is numerically simulated and recommended to extrude I-shaped lead alloy with minimum load requirement. The experimental results reveal that increasing area ratio leads to quasi-sinusoidal pattern in surface hardness of I-shaped section irrespective of strain rate value. Increasing web to flange ratio, therefore, leads to increasing anisotropy of the I-shaped lead alloy. The extruded sections were examined with optical metallurgical microscope, and it is observed that increasing strain rate results in profound refinement of grain and inclusions in lead alloy even at room temperature.