Error Estimation of Values Obtained from Practical CFD Analysis

In recent years, it has become common to analyze the detailed, three-dimensional flow features in reactor pressure vessels of boiling water reactors (BWRs) by computational fluid dynamics (CFD) analysis. However, there are few reports on practical examples of estimation or on estimation methodologies of the uncertainties in multi-dimensional CFD analysis. In this paper, to estimate the errors of values obtained from practical CFD analysis of a complex flow field, we propose a quantitative methodology that adopts the numerical analysis errors of “elementary phenomena” as error factors for sensitivity analyses, as well as, for instance, dimensional tolerances or errors of input values. Using this methodology with CSAU methodology, we showed a practical simplified example of error estimation regarding calculated water surface drop along the radial direction obtained from CFD analysis of the hydraulic gradient formed in the reactor pressure vessel of a BWR. We show the validity of the methodology by comparing this “estimated error” with a “reference error” evaluated by comparing numerical and experimental results.     

区域安全稳定控制系统在青海西部电网中的应用

青海西部电网区域安全稳定控制系统由安装在7个厂站的稳定控制装置组成.该电网与青海主网联络线或主力机组发生故障时,采取精确切机、精确切负荷和根据各厂站电压情况综合判断投切电容器和电抗器等措施,防止大面积停电,保证其安全稳定运行.文中介绍了青海西部电网区域安全稳定控制系统的配置、特点以及有效的控制策略.     

宜兴抽水蓄能电站上水库工程的排水系统

宜兴抽水蓄能电站上水库全库盆采用钢筋混凝土面板防渗,防渗总面积为18.06万m2。库岸稳定是上水库的主要工程地质问题之一,而影响库岸稳定的主要因素是地下水。工程共设置了5.1 km排水洞及排水廊道,6.5万m排水孔,确保坝体、库岸稳定和降低面板所受的反向水压力。     

Heat transfer performance of thermoelectric cooling integrated with wavy channel heat sink with different magnetic distances

Thermoelectric cooling (TEC) reverses the electrical energy to temperature caused by the Peltier effect, where a temperature difference occurs between two conductors, that is, hot and cold junctions. This article presents the enhanced heat transfer of a TEC module using a TEC1-12710 model integrated with a wavy channel heat sink using ferrofluid as a coolant under continuous and pulsating flows, where the differences in the distance of the magnetic field are considered. Square permanent magnets measuring 30 mm × 20 mm × 4 mm (width × length × height) are used to transmit a magnetic field to the heat sink and then tested under a magnetic distance of 10–30 mm. The test is performed at a water flow rate from 0.0083 to 0.028 kg/s and supplied with a constant TEC voltage of 12 V. By applying a magnetic field to the TEC module with a magnetic distance of 20 mm and a ferrofluid concentration ratio of 0.015%, the cooling efficiency increases by approximately 18.64%. Hence, using pulsating flow may improve thermal efficiency by approximately 23%. The results show an exponential increase in the cooling efficiency when both passive and active cooling techniques are used.     

Effect of porous slab thickness and Darcy number on thermohydraulic transport characteristics of Ag–TiO2/water hybrid nanofluid flow-through partially porous wavy channels

The present article investigates the effect of varying porous slab thicknesses (S = 0–0.4) and Darcy number (Da = 10⁻⁶–10⁻²) on the thermohydraulic performance of three different corrugated channels (triangular, sinusoidal, and trapezoidal) embedded with partially filled porous media. Ag–TiO₂/water hybrid nanofluid ($\varphi$ = 0–0.04) is taken as coolant flowing at Re = 400. Results revealed that the thermal performance (average Nusselt number, Nu_avg and enhancement ratio, ER) augments with the increase in porous slab thickness and decrease in Darcy number. However, the hydraulic performance reduces (i.e., an increase in pressure drop). To check the viability of the cooling system performance factor (PF) is evaluated which demonstrates variation in thermal performance considering pressure drop penalty also. It is demonstrated that among all configurations, the trapezoidal channel with porous slab thickness (S = 0.4) and Darcy number (Da = 10⁻⁴) gives maximum enhancement thermal performance (110%) considering water as a coolant ($\varphi$ = 0). Furthermore, enhancement in thermal performance by 210% is noticed as volume concentration $\varphi$ of hybrid nanofluid varies from 0% to 4%. It is also evident that the value of PF for all corrugated channels is lower than 1 indicating the nonviable system. However, for the case of the partially porous plane channel the maximum PF = 1.07.