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

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Weitong Li ◽  
Lei Yu ◽  
Jianli Hao ◽  
Mingrui Li
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Flow Field ◽  
Natural Circulation ◽  
Internal Flow ◽  
Loss Coefficient ◽  
Experimental Results ◽  
Passive Safety ◽  
Passive Safety System ◽  
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.

scholarly journals Numerical simulation of the non-uniform flow in a full-annulus multi-stage axial compressor with the harmonic balance method

2020 ◽  
Vol 12 (3) ◽  
pp. 168781401989721 ◽  
Author(s):  
Haiou Sun ◽  
Meng Wang ◽  
Zhongyi Wang ◽  
Song Wang ◽  
Franco Magagnato
Keyword(s):  
Flow Field ◽  
Harmonic Balance ◽  
Axial Compressor ◽  
Harmonic Balance Method ◽  
Internal Flow ◽  
Uniform Flow ◽  
Experimental Results ◽  
Balance Method ◽  
Operating Characteristics ◽  
Multi Stage

To improve the understanding of unsteady flow in modern advanced axial compressor, unsteady simulations on full-annulus multi-stage axial compressor are carried out with the harmonic balance method. Since the internal flow in turbomachinery is naturally periodic, the harmonic balance method can be used to reduce the computational cost. In order to verify the accuracy of the harmonic balance method, the numerical results are first compared with the experimental results. The results show that the internal flow field and the operating characteristics of the multi-stage axial compressor obtained by the harmonic balance method coincide with the experimental results with the relative error in the range of 3%. Through the analysis of the internal flow field of the axial compressor, it can be found that the airflow in the clearance of adjacent blade rows gradually changes from axisymmetric to non-axisymmetric and then returns to almost completely axisymmetric distribution before the downstream blade inlet, with only a slight non-axisymmetric distribution, which can be ignored. Moreover, the slight non-axisymmetric distribution will continue to accumulate with the development of the flow and, finally, form a distinct circumferential non-uniform flow field in latter stages, which may be the reason why the traditional single-passage numerical method will cause certain errors in multi-stage axial compressor simulations.

scholarly journals Numerical investigations on effect of wear-ring clearance on performance of a submersible well pump

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770415 ◽  
Author(s):  
Weidong Shi ◽  
Xiongfa Gao ◽  
Qihua Zhang ◽  
Desheng Zhang ◽  
Daoxing Ye
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Reverse Flow ◽  
Internal Flow ◽  
Experimental Results ◽  
Ring Size ◽  
Numerical Investigations ◽  
Calculation Results

A typical submersible well pump was investigated in this article. The whole flow field of submersible well pump was numerically simulated by computational fluid dynamics software. The influence of clearance of wear-rings on the external characteristic and internal flow field was analyzed through comparing the calculation results with experimental results. The result of the numerical simulation shows that changing clearance of front wear-ring has a greater impact on pump performances than changing clearance of back wear-ring, and the head and efficiency of pump decrease with the increase in the size of clearance. Especially when the size of clearance is larger than 0.5 mm, decreasing becomes more obvious. When the front and back wear-ring size of the clearance comes to 1.0 mm, the efficiency decreases from the highest point of 75.31% to 65.44% at rated flow, and the head of pump decreases about 3.5 m. When the size of clearance is 0.2 mm, reverse-flow will appear in the front shroud cavity of the impeller, and leakage from back wear-ring through the balance hole into the impeller, which has a little influence on the flow field of the impeller inlet.

Flow Characterization and Heat Transfer of Core-Catcher in Passive Safety System

2012 ◽  
Author(s):  
Tomohisa Kurita ◽  
Toshimi Tobimatsu ◽  
Mika Tahara ◽  
Masato Yamada ◽  
Yoshihiro Kojima
Keyword(s):  
Natural Circulation ◽  
Cooling Water ◽  
Heat Removal ◽  
Severe Accident ◽  
Passive Safety ◽  
Cooling Channels ◽  
The Core ◽  
Flow Characterization ◽  
Passive Safety System ◽  
Core Catcher

A mitigation system which can keep core melt stable after a severe accident is necessary to a next generation BWR design. Toshiba has been developing a compact core catcher to be placed at the lower drywell in the containment vessel. The cooling water for the core catcher is supplied from the passive flooder and PCCS drain line. After the core catcher is flooded, the molten core would be cooled by both overflooding water and inclined cooling channels, in which water is boiling and natural circulation is established. So the core catcher can operate in passive manner and has no active component inside the containment. This paper summarizes flow dynamics and heat removal capability in an inclined cooling channel of core catcher when cooling water flows by the natural circulation.

Approximate Calculation of Pressure Drop in Laminar Flow of Generalized Newtonian Fluid Through Channels with Insert

1995 ◽  
Vol 60 (9) ◽  
pp. 1476-1491
Author(s):  
Václav Dolejš ◽  
Petr Doleček ◽  
Ivan Machač ◽  
Bedřich Šiška
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Numerical Solution ◽  
Newtonian Fluid ◽  
Calculation Method ◽  
Approximate Calculation ◽  
Creeping Flow ◽  
Experimental Results ◽  
Generalized Newtonian Fluid

An equation of Rabinowitsch-Mooney type has been suggested for approximate calculation of pressure drop in flow of generalized Newtonian fluid through channels with insert both in the region of creeping flow and at higher values of the Reynolds number, and this calculation method has been verified for four types of insert using own numerical solution and experimental results as well as literature data.

Heat Transfer Characteristics in Flue Gas Fired Regenerators of Water/Lithium Bromide Absorption Chillers

2006 ◽  
Author(s):  
Christoph Kren ◽  
Christian Schweigler ◽  
Felix Ziegler
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flue Gas ◽  
Gas Turbines ◽  
Gas Flow ◽  
Natural Circulation ◽  
Lithium Bromide ◽  
Experimental Results ◽  
Major Step ◽  
Absorption Chillers

It has already been shown that efficiency of direct-fired absorption chillers or tri-generation systems (CCHP) can be increased if the hot flue gas - from internal gas burner or from motor engines or gas turbines - is successively utilized in the absorption cycle at several temperature levels. For successful realization of such concepts, however, efficient heat exchanger designs are required. An increase in complexity on the flue gas side of the chiller must not introduce a proportional increase in size, cost, and pressure drop. Thus, the development of a compact and efficient flue gas fired regenerator design with low flue gas pressure drop is a major step towards COP increase in direct-fired and exhaust-fired absorption chillers. The potential of different regenerator concepts including common smoke tube design and alternative boiling tube designs with natural circulation of the lithium bromide solution and flue gas flow across bundles of plain or finned tubes is discussed. Promising designs are identified on basis of numerical calculations. A semi-industrial sized prototype of a direct-fired regenerator with consecutive sections of plain and finned vertical boiling tubes has been tested in laboratory over a range of thermal inputs up to 256 kW (net. CV). Experimental results of heat transfer and combustion side pressure drop investigations at the novel regenerator are presented. Accordance of experimental results with theoretical predictions is shown.

Numerical Simulation of an Oscillating Cylinder at High Reynolds Number

2013 ◽  
Author(s):  
Simone Mandelli ◽  
Sara Muggiasca ◽  
Stefano Malavasi
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Flow Field ◽  
High Reynolds Number ◽  
Fluid Dynamic ◽  
Numerical Results ◽  
Experimental Results ◽  
Dynamic Conditions ◽  
High Reynolds ◽  
Lock In

In this work a numerical investigation of the main flow field characteristics around a free oscillating rigid circular cylinder immersed in a turbulent flow is proposed (Re ≈ 5 · 104). The cylinder is characterized by high value of mass ratio and mass damping (m* = 145; ξ = 0.6 ÷ 1.14 · 10−3; m*ξ = 0.1 ÷ 0.25). The numerical results are compared with experimental data obtained in the wind tunnel under very similar fluid dynamic conditions. There are few works in literature that consider both numerical and experimental results under these conditions. This is probably due to the experimental facilities limitations and the computational difficulties correlated to modeling the flow at high Reynolds number. A numerical URANS model was developed through a CFD commercial code using a k–ω SST turbulence model in a 3D domain with the aim of matching the experimental results in the last years in the Politecnico di Milano Wind Tunnel on a suspended oscillating cylinder. The numerical setup is characterized by the use of the DFBI-Morphing (Dynamic Fluid Body Interaction) model that allows reproducing the body motion in response to fluid forces treating the cylinder as a mass-damping-spring system by introducing spring and damping forces acting on it. A preliminary check of this numerical setup was provided by a benchmark case involving a simple case of fixed cylinder at the same Reynolds number, where the movements of the cylinder were disabled. The numerical results of this case have been compared with experimental and numerical results reported in literature in terms of Drag and Lift coefficients and Strouhal number at high Reynolds numbers (Re ≈ 5 · 104). After that benchmark, the full setup has been checked by considering specific fluid dynamic conditions out of the lock in region in which the oscillations of the cylinder are negligible. Finally two points of the cylinder steady state response curve in the lock in region were investigated. The numerical model gave good results in terms of amplitude response of the cylinder and aerodynamic forces in agreement with experimental results. The analysis of the numerical reconstruction of the flow field evolution are therefore considered to have more information on the vortex shedding mode especially in the transition region between 2S and 2P mode.

Research and Development on No-Moving-Part Valves Using Enhancement

2009 ◽  
Author(s):  
Kai-Shing Yang ◽  
Young-Chang Liu ◽  
Chi-Chuan Wang ◽  
Jin-Cherng Shyu
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Research And Development ◽  
Experimental Results ◽  
Efficiency Ratio ◽  
Circular Area ◽  
Interface Friction ◽  
Pressure Drops ◽  
Micro Nozzle ◽  
Maximum Improvement

This study characterizes and analyzes the performances of micro diffusers/nozzles with six types of enhancement structures. The pressure drops across the designed micro nozzles/diffusers are found to be increased considerably when the obstacle and fin structure are added. Further, the micro nozzle/diffuser having added circular area reveals the lowest pressure drop, owing to the hydraulic diameter is increased by circular area and lower interface friction. The maximum improvement of the loss coefficient ratio is about 16% for an added 3-fin structure operated at a Reynolds number around 70. Upon this situation, the static rectification efficiency improves 4.43 times than the conventional nozzle/diffuser. Experimental results indicate the performance peaks at a Reynolds number around 70, and an appreciable decline is encountered when the Reynolds number is reduced. It is due to the efficiency ratio of conventional micro nozzle/diffuser significant increases with the Reynolds number.

Thermal Performance in Circular Tube with Co/Counter-Twisted Tapes

2014 ◽  
Vol 931-932 ◽  
pp. 1198-1202 ◽  
Author(s):  
Suriya Chokphoemphun ◽  
Chayodom Hinthao ◽  
Smith Eiamsa-ard ◽  
Pongjet Promvonge ◽  
Chinaruk Thianpong
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Circular Tube ◽  
Experimental Results ◽  
Enhanced Heat Transfer ◽  
Twisted Tapes ◽  
Twist Ratio

Thiswork presents an experimental study on enhanced heat transfer and pressure loss characteristics in a tube having a uniform heat-fluxed wall by using small double and triple co-and counter-twisted tapes at two twist ratios, y/w=4 and 4.5. The investigation has been conducted for Reynolds number from 5300-20,000. The experimental results of the heat transfer and pressure drop are proposed in terms of Nusselt number and friction factor, respectively.The experimental results reveal thatthe maximum TEF for the triple counter-twisted tapesat smaller twist ratio isabout 1.26.

scholarly journals Experimental results on air permeability of agricultural nets

2016 ◽  
Vol 47 (3) ◽  
pp. 134 ◽  
Author(s):  
Sergio Castellano ◽  
Giuseppe Starace ◽  
Lorenzo De Pascalis ◽  
Marco Lippolis ◽  
Giacomo Scarascia-Mugnozza
Keyword(s):  
Pressure Drop ◽  
Wind Tunnel ◽  
Air Flow ◽  
Loss Coefficient ◽  
Experimental Results ◽  
Equivalent Diameter ◽  
Air Velocity ◽  
Low Wind Speed ◽  
Technical Textiles ◽  
Set Up

In order to evaluate the influence of the texture characteristics of agricultural nets on the air flow passing through them, a micro wind tunnel was designed and built in the testing and engineering laboratory of Sachim s.r.l., an Italian high-density polyethylene (HDPE) technical textiles manufacturer. The micro wind tunnel (0.1345 m diameter) allowed the simultaneous measurement of the air flowrate and the pressure drop through a net sample. The equipment was designed to set up the inclination of the net samples with respect of the airflow at fixed angles (90°, 60°, 45°, 30°). The variation of the pressure drop with the air velocity on four different flat woven round monofilament HDPE nets perpendicular to the air flow are here reported. In all cases the air velocity measured into the micro wind tunnel was above 4 m s–1 hence reported results do not consider low wind speed. Preliminarily, the loss coefficient was assumed as a function of porosity and Reynolds number, calculated with reference to the equivalent diameter of the pores, FS(Rel,ε) and showed percent deviations form experimental results in the range 14.6%÷25.3%. Hence a simplified expression of the loss coefficient, depending only on the porosity was proposed, FS(ε) which highlighted differences with experimental results in the range 3.5%÷20.3%. Finally, results were compared with those based on the Bernoulli’s principle found in the literature.

Sign in / Sign up

Export Citation Format

Share Document