scholarly journals Simulating the Effects of Structural Parameters on the Hydraulic Performances of Venturi Tube

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Yanqi Sun ◽  
Wenquan Niu
Keyword(s):  
Pressure Difference ◽  
Critical Pressure ◽  
Structural Parameters ◽  
Pressure Coefficient ◽  
Head Loss ◽  
Hydraulic Performance ◽  
Outlet Section ◽  
Minimum Pressure ◽  
Absorption Ratio ◽  
Contraction Ratio

The effects of Venturi structural parameters on its hydraulic performance were studied, which provided theoretical basis for the design of Venturi injector. With an inlet diameter of 50 mm, based on the method of computational fluid dynamics (CFD), the effects of the structural parameters (such as throat taper, throat contraction ratio, and throat length) on their hydraulic performance (such as outlet faceted average velocity, minimum pressure, and critical pressure) were studied under different inlet pressures and pressure differences between inlet and outlet. A power function relationship existed between the mean velocity in outlet section and pressure difference, with an approximate flow stance index of 0.53. Minimum pressure occurred in the throat inlet wall and there was a linear relationship between the minimum pressure and the pressure difference at the inlet and outlet. The throat contraction ratio was the main factor on the effect of Venturi injector performance, which was positively correlated with outlet velocity, negatively to critical pressure, the minimal in-tube pressure, coefficient of local head loss, and fertilizer absorption ratio. For designing Venturi injector, contraction ratio should be reasonably selected according to the coefficient of local head loss and fertilizer absorption ratio.

An Effect of Air Content on the Occurrence of Cavitation

1960 ◽  
Vol 82 (4) ◽  
pp. 941-945 ◽  
Author(s):  
J. W. Holl
Keyword(s):  
Pressure Coefficient ◽  
Cavitation Number ◽  
Experimental Results ◽  
Simultaneous Occurrence ◽  
Minimum Pressure ◽  
Air Content ◽  
The Difference ◽  
Dissolved Air

The simultaneous occurrence of vaporous and gaseous cavitation on hydrofoils is considered. The experimental results show that gaseous cavitation occurs at much higher ambient pressures than that for the vaporous cavitation resulting in desinent-cavitation numbers twice the minimum-pressure coefficient of the hydrofoil. The analysis indicates that the difference between the desinent-cavitation number for the gaseous cavitation and that for the vaporous cavitation is proportional to the dissolved air content and inversely proportional to the square of the velocity.

Characteristics of Miniature Short-Tube Orifice Flows

1989 ◽  
Vol 203 (5) ◽  
pp. 351-358 ◽  
Author(s):  
T A Fox ◽  
J Stark
Keyword(s):  
Experimental Investigation ◽  
Critical Pressure ◽  
Fuel Injection ◽  
Flow Characteristics ◽  
Head Loss ◽  
Differential Pressure ◽  
Pressure Differential ◽  
Contraction Parameter ◽  
Volumetric Discharge ◽  
Short Tube

This paper presents the results of an experimental investigation into the flow characteristics of miniature short-tube orifices of a type commonly used for fuel injection. From measurements of differential pressure and volumetric discharge it is shown that these devices are susceptible to a cavitation-induced instability phenomenon known as hydraulic flip. It was found that this instability is limited to orifices of length less than fourteen diameters and occurs at a critical pressure differential which varies as a function of the orifice l/d ratio and contraction parameter β. In addition, the performance of the device is examined in terms of the head loss characteristics and it is shown that the mechanisms associated with hydraulic flip have a significant effect on the efficiency of discharge.

scholarly journals Effect of the Area Contraction Ratio on the Hydraulic Characteristics of the Toothed Internal Energy Dissipaters

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1406
Author(s):  
Ting Zhang ◽  
Rui-xia Hao ◽  
Xiu-qing Zheng ◽  
Ze Zhang
Keyword(s):  
Energy Dissipation ◽  
Internal Energy ◽  
Dissipation Rate ◽  
Pressure Coefficient ◽  
Energy Dissipation Rate ◽  
Flow Coefficient ◽  
Physical Model Test ◽  
Hydraulic Characteristics ◽  
Body Type ◽  
Contraction Ratio

Toothed internal energy dissipaters (TIED) are a new type of internal energy dissipaters, which combines the internal energy dissipaters of sudden reduction and sudden enlargement forms with the open-flow energy dissipation together. In order to provide a design basis for an optimized body type of the TIED, the effect of the area contraction ratio (ε) on the hydraulic characteristics, including over-current capability, energy dissipation rate, time-averaged pressure, pulsating pressure, time-averaged velocity, and pulsating velocity, were studied using the methods of a physical model test and theoretical analysis. The main results are as follows. The over-current capability mainly depends on ε, and the larger ε is, the larger the flow coefficient is. The energy dissipation rate is proportional to the quadratic of Re and inversely proportional to ε. The changes of the time-averaged pressure coefficients under each flow are similar along the test pipe, and the differences of the time-averaged pressure coefficient between the inlet of the TIED and the outlet of the TIED decrease with the increase of ε. The peaks of the pulsating pressure coefficient appear at 1.3 D after the TIED and are inversely proportional to ε. When the flow is 18 l/s and ε increases from 0.375 to 0.625, the maximum of time-averaged velocity coefficient on the line of Z/D = 0.42 reduces from 2.53 to 1.17, and that on the line of Z/D = 0 decreases from 2.99 to 1.74. The maximum values of pulsating velocity on the line of Z/D = 0.42 appear at 1.57D and those of Z/D = 0 appear at 2.72D, when the flow is 18 l/s. The maximum values of pulsating velocity decrease with the increase of ε. Finally, two empirical expressions, related to the flow coefficient and energy loss coefficient, are separately presented.

Thermal–Hydraulic Performance Analysis of a Convergent Double Pipe Heat Exchanger

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Ahmed T. Al-Sammarraie ◽  
Kambiz Vafai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Contraction Ratio ◽  
Wide Range ◽  
Prandtl Numbers ◽  
Double Pipe ◽  
The Impact ◽  
Pipe Heat

The present investigation proposes an innovative convergent double pipe heat exchanger (C-DPHE). A two-dimensional (2D) axisymmetric heat transfer model with counterflow is employed to analyze the thermal and hydraulic performance of this configuration numerically. The impact of convergence in the flow direction, using a wide range of contraction ratio (Cr), is explored. The effect of Reynolds and Prandtl numbers on the flow and heat transfer is addressed, as well. The model results were validated with available data from the literature, and an excellent agreement has been confirmed. In general, the findings of the present study indicate that increasing the contraction ratio increases heat transfer and pressure drop in the C-DPHE. Moreover, this configuration has a prominent and sustainable performance, compared to a conventional double pipe heat exchanger (DPHE), with an enhancement in heat transfer rate up to 32% and performance factor (PF) higher than one. Another appealing merit for the C-DPHE is that it is quite effective and functional at low Reynolds and high Prandtl numbers, respectively, since no high-operating pumping power is required. Further, the optimal operating conditions can be established utilizing the comprehensive information provided in this work.

Hydraulic Performance Optimization on Inlet-Outlet of Pumped Storage Plant

2013 ◽  
Vol 405-408 ◽  
pp. 491-494
Author(s):  
Ya Nan Gao ◽  
Jun Nan Yi ◽  
Rui Cun Zhao ◽  
Li Fen Chen ◽  
Xu Min Wu
Keyword(s):  
Numerical Simulation ◽  
Performance Optimization ◽  
Flow Distribution ◽  
Head Loss ◽  
Hydraulic Performance ◽  
Flow Coefficient ◽  
Head Loss Coefficient ◽  
Uniform Flow Distribution ◽  
Orifice Flow ◽  
Pumped Storage

This paper, using 3-D numerical simulation and the hydraulic model tests, presents an analysis on hydraulic performance of pumped storage plant inlet/outlet. It discusses the uneven flow coefficient, coefficient of orifice flow distribution and head loss coefficient of inlet/outlet in different sizes. The optimized size has a uniform flow distribution, with less to produce unwanted eddies.

scholarly journals Impact of Viscosity Variation, and Flow Rate on Coefficient of Discharge in Venturimeter Utilizing Taguchi Methodology

2020 ◽  
Vol 9 (4) ◽  
pp. 1838-1840
Keyword(s):  
Pressure Difference ◽  
Flow Measurement ◽  
Head Loss ◽  
Measuring Apparatus ◽  
Cross Sectional ◽  
Measuring Devices ◽  
Specific Geometry ◽  
Viscosity Variation ◽  
Coefficient Of Discharge ◽  
The Impact

Most of the industries are concerned with flow measurement and accurate measurement of fluid is important to obtain specific proportion as per process requirement. Generally Venturimeter (VM) is utilized in enterprises due to notable highlights offered by it. VM works on the principle of pressure difference i.e. Bernoulli’s principle. By varying cross sectional area of flow, it creates pressure difference along its length which is used to calculate theoretical discharge. Head loss in VM is less as compared to other flow measuring apparatus. Because of its specific geometry eddies formation is avoided causing less head loss. The coefficient of discharge (Cd ) is an important parameter always referred in case of flow measuring devices. For VM it varies from 0.95 to 0.99. Tests have been performed in accordance to Taguchi L9 O-A on cast iron pipe to examine the impact of variations of viscosity, and rates of flow on the Cd .

Aperiodic Instability of a Once-Through Steam Generator with a Feedwater Line

2006 ◽  
Author(s):  
Jae-Kwang Seo ◽  
Han-Ok Kang ◽  
Juhyeon Yoon ◽  
Keung-Koo Kim
Keyword(s):  
Experimental Data ◽  
Steam Generator ◽  
Pressure Difference ◽  
Flow Instability ◽  
Reverse Flow ◽  
Flow Direction ◽  
Minimum Pressure ◽  
Multiple Flows ◽  
Static Flow ◽  
Aperiodic Instability

Aperiodic (static) flow instability is an instability related to the change of a flow direction in individual steam generating U-shaped channels operating at given pressure difference. The nature of an aperiodic instability is close to a Ledinegg instability [1] related to the presence of multiple flows at the full hydraulic curve of a U-shaped channel. In this paper, the conditions for a reverse flow for a once-through steam generator (OTSG) with U-shaped modular feedwater line (MFL) are studied. From the results of the studies, it is revealed that the change of a flow direction in the MFL is due to the boiling of the feedwater in the downcomer branch of the U-shaped MFL and that multiple flows start in an area of the extremes corresponding to the minimum pressure difference of the hydraulic curves. Calculation models for predicting a threshold of an aperiodic instability for the OTSG of interest is proposed and the analysis results are compared with the experimental data.

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