In order to study the variation of vortices and heat transfer enhancement characteristics of piezoelectric vibrating cantilever in liquid-cooled channels, the effects of fluid density and viscosity, mainstream velocity, and excitation voltage on vortices were analyzed. The theoretical and numerical simulation of piezoelectric vortices was carried out by using fluid-solid coupling method. On the basis of hydrodynamic function considering the additional effect of liquid viscosity and density on piezoelectric vibrator, the vortex structure of piezoelectric vibrator was analyzed by panel method free-wake model. It is found that the larger the density of the liquid, the smaller the vortex shedding strength and the radius of the core. The larger the viscosity of the liquid, the easier to fully develop the vortex generated by the excitation. The increase of the mainstream flow velocity is beneficial to the development of the vortex structure and the increase of the vorticity intensity. Compared with the increase of the mainstream flow velocity, the excitation voltage is more conducive to the enhancement of the vorticity structure, then make it easier to mix hot and cold fluids, thus enhancing heat transfer.

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Enhanced heat transfer research in liquid-cooled channel based on piezoelectric vibrating cantilever

The longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty. Vortex generators (VGs) which can generate longitudinal vortices are widely used in fin-and-tube heat exchangers for heat transfer enhancement. But for a long time, researches are carried out focusing on the effect of the shape and parameters of VGs on heat transfer and the relationship between the longitudinal vortices intensity and heat transfer intensity is analyzed qualitatively. The quantitative relationship between the longitudinal vortices intensity and heat transfer intensity is seldom reported. Longitudinal vortex is a typical secondary flow, and thus the longitudinal vortex intensity can be defined using the secondary flow intensity parameter. In this paper, the numerical models of flat tube bank fin heat exchanger with VGs mounted on the fin surfaces are studied for different fin and VGs parameters. The longitudinal vortices intensity is quantitatively defined using the nondimensional secondary flow intensity parameter Se. The relationship between the longitudinal vortices intensity and the heat transfer intensity and that between the increment values of Se and Nu caused by the longitudinal vortices are quantitatively studied. The results show that there is no corresponding relationships neither between Nu and Re, nor between Se and Re. Similarly, no linear relationship exists between the friction factor f and the values of Re and Se. But the corresponding relationship exists not only between Se and Nu but also ∆Se

Relationship between longitudinal vortex intensity and heat transfer intensity of flat tube heat exchanger

The empirical evaluation of the success of a participant is critical for a thorough assessment of sporting events. Evaluating students' efficiency or scripting in sports is limited, even if skilled experts do it. In this paper, support vector machine-assisted sports training (SVMST) has been proposed to evaluate student sports efficiency. Sports training prototypes are based on different criteria that participate in the matches, traditional game statistics, person quality measures, and opposing data. The success of students is divided into two grades: moderate and large. The primarily supervised learning-based classification method is used to create a template for identifying student sports training efficiency. SVM implements learning methods, data collection methods, effective model assessment methods, and particular difficulties in predicting sports performance. The experimental results show SVMST to high student performance of 98.7%, a low error rate of 9.8%, enhanced assessment ratio of 97.6%, training outcome of 95.6%, and an efficiency ratio of 96.8%.

Song Kewei

Papers

Relationship between longitudinal vortex intensity and heat transfer intensity of flat tube heat exchanger

Evaluating the Efficiency of Student Sports Training Based on Supervised Learning