In comparison with previous researches of swirling flow, spiral flow generated in the spiral nozzle has some different flow characteristics. It does not need a forced tangential momentum to generate its velocity and has some different merits from the swirling flow such as long potential core and low tangential velocity. In this study, the effect of nozzle geometry on the flow characteristics in spiral nozzle was investigated by experiment and computation. As a result, the flow characteristics obtained by experiment has a satisfactory agreement with computational results, quantitatively and qualitatively.
This paper reports the thermal performance of smart heat sinks (SHSs) consisting of hybrid pin fins (HPFs) containing internal channels and integrated with plate fins. The SHSs are mainly aimed at cooling high power LED modules under natural convection condition or forced convection condition with a moderate air velocity. The computational fluid dynamics (CFD) models of SHSs are generated utilizing a commercial CFD software package. The CFD analysis evaluates the cooling performance as well as the basic thermal behavior of the SHSs under various parametric conditions such as heat dissipations ranging from 5 to 20W, air velocities ranging from 0 to 3m/s, and fin spaces of 12, 15, and 20mm. The cooling performance of the SHSs is compared with those of conventional pin fin heat sinks (PHSs). Parametric study has found that thermal resistances of the SHSs are typically smaller than those of the PHSs; for example, they are 15% smaller than the PHS under natural convection. Parametric results show that 15mm is the best fin space for SHSs. This study also explores the effect of the declination angles between the symmetry axis of the fin and the axis of the gravity on the performance of HPFs under natural convection. The results show the thermal resistance value of the HPF decreases with the increase of the declination angle.
A study on sloshing characteristics in a rectangular tank, which is horizontally excited with a specific range of the Reynolds number, is approached numerically. The nonlinearity of sloshing flow is confirmed by comparing it with the linear solution based on the potential theory, and the time series results of the sloshing pressure are analyzed by Fast Fourier Transform (FFT) algorithm. Then, the pressure fluctuation phenomena are mainly observed and the magnitude of the amplitude spectrum is compared. The results show that, when the impact pressure is generated, large pressure fluctuation in a pressure cycle is observed, and the effects of the frequencies of integral multiples when the fundamental frequency appears dominantly in the sloshing flow.
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