Comparison of heat transfer in natural and forced circulation under rolling motion

A comparative analysis of heat transfer characteristic in pulsating flow induced by rolling motion under natural circulation and forced circulation condition was performed. Variation of local and average heat transfer characteristics with rolling motion were also investigated. The results show that the natural circulation time-averaged heat transfer characteristic is enhanced by rolling motion. However, the variation of time-averaged heat transfer characteristic of forced circulation is not significant. In addition, the relationship between the relative pulsation amplitude of Reynolds number and Nusselt number does not present predominant difference in natural and forced circulation conditions.

Experimental and CFD Investigation on Flow Behaviors of a NPP Pump under Natural Circulation Condition

Passive safety system is the core feature of advanced nuclear power plant (NPP). It is a research hotspot to fulfill the function of passive safety system by improving the NPP natural circulation capacity. Considering that the flow behaviors of stopped pump pose a significant effect on natural circulation, both experimental and computational fluid dynamics (CFD) methods were performed to investigate the flow behaviors of a NPP centrifugal pump under natural circulation condition with a low flow rate. Since the pump structure may lead to different flows depending on the flow direction, an experimental loop was set up to measure the pressure drop and loss coefficient of the stopped pump for different flow directions. The experimental results show that the pressure drop of reverse direction is significantly greater than that of forward direction in same Reynolds number. In addition, the loss coefficient changes slightly while the Reynolds number is greater than 8 × 104; however, the coefficients show rapid increase with the decrease in Reynolds number under lower Reynolds number condition. According to the experimental data, an empirical correlation of the pump loss coefficient is obtained. A CFD analysis was also performed to simulate the experiment. The simulation provides a good accuracy with the experimental results. Furthermore, the internal flow field distributions are obtained. It is observed that the interface regions of main components in pump contribute to the most pressure losses. Significant differences are also observed in the flow field between forward and reverse condition. It is noted that the local flows vary with different Reynolds numbers. The study shows that the experimental and CFD methods are beneficial to enhance the understanding of pump internal flow behaviors.

THE ROLE OF GROWTH DIFFERENTIATION FACTOR 11 (GDF11) IN REGULATION OF LIPID METAbOLISM AND CARDIOHEMODYNAMIC FUNCTIONS IN ESSENTIAL HYPERTENSION PATIENTS IN MODERATE EFFORT ExERCISES

Aim. To reveal the role of a “youth protein” GDF11 in regulation of lipid metabolism and cardiovascular system work in essential hypertension (EH) in women taking antihypertension medications and regularly involved in moderate physical exercises (kinesitherapy).Material and methods. In all participants, the level of GDF11 was measured by immune enzyme assay, and levels of lipids; registration was done of blood pressure, echocardiography and circulation condition with a novel sensor of dynamic light scattering (mDLS).Results. In women with AH taking antihypertension medications, the level of GDF11 was lower more than 3 times. In EH patients the deviations found, in a shear flow velocity with significant increase of rapid velocity processes. Correlations found for GDF11 level with the age, blood pressure, condition of the heart work, hemodynamical and oscillatory indexes. In the EH group patients regularly doing exercises (kinesitherapy), the level of GDF11, blood pressure, lipid profile and all parameters of heart work and hemodynamics are close to normal.Conclusion. The “youth protein” CDF11 is a factor of prevention of AH. Kinesitherapy in EH patients normalizes GDF11, lipid profile, and significantly increases the work of cardiovascular system.