Head loss coefficient through sharp-edged orifices

The Swiss confederation aims to phase out nuclear power production with its Energy Strategy 2050 program by increasing the renewable energy contribution to its overall energy generation. Hydroelectricity, which is the most important form of renewable energy in Switzerland, supplying almost 60% of the electricity in 2015, should increase its production capacity to achieve this goal. The case study presented in this paper focuses on the replacement of the third turbine in the Gondo high-head power plant with a turbine with a higher discharge capacity. The results of one-dimensional (1D) numerical simulations shown that throttling the surge tank is an efficient measure to adapt the existing hydraulic system for the increased discharge. Physical-scale modeling was performed to validate the design of the grid throttle placed at the bottom of the lower chamber of the existing surge tank. The grid throttle geometry and its head losses are compared with two existing similar throttles in Switzerland. Finally, prototype tests of the temporal evolution of water levels in the surge tank using the throttle coefficients obtained experimentally showed good agreement. Hybrid modeling using a combination of 1D numerical models, threedimensional (3D) physical models, and prototype tests are highly recommended for checking the transient performance of the waterway after a refurbishment of turbines with increased design discharge. Furthermore, placing a throttle at the bottom of an existing surge tank is often an effective and economical solution in the case of small increases in installed capacity.

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“…9 and Table 5. The second type is rack geometry as defined by Adam et al (2016c). These grids consist only of horizontal beams.…”

Section: Model Test Resultsmentioning

confidence: 99%

Design of a Throttled Surge Tank for Refurbishment by Increase of Installed Capacity at a High-Head Power Plant

Adam

Cesare

Nicolet³

et al. 2018

J. Hydraul. Eng.

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“…Nevertheless, examples of successful application can also be found in a wide range of cases: from wind forces on photovoltaic panels (Edgar et al, 2015) to anti-icing systems for wings (Hannat et al, 2014) or hydro power intakes (Bermúdez et al, 2017;Gabl et al, 2018). This commercial code is well validated for free surface (Andersson et al, 2013;De Cesare et al, 2001) and pressurized flow conditions (Adam et al, 2016b;Adane et al, 2008;Gabl et al, 2014bGabl et al, , 2018Seibl, 2016;.…”

Section: Generalmentioning

confidence: 99%

Design criteria for a type of asymmetric orifice in a surge tank using CFD

Gabl

Righetti

2018

Engineering Applications of Computational Fluid Mechanics

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An asymmetric orifice can be added to a surge tank of a hydro power plant to dampen the mass oscillation. This allows a reduction of the required volume and a more stable behavior of the overall hydraulic system. In this paper, the advantage of a typical asymmetric orifice is shown in comparison with a sharp-edged geometry with two different pipe diameters. The software ANSYS-CFX is used to investigate the influence of the individual geometry parameters (radius, length, angle at the forefront) on the local head loss coefficients and the ratio of the two flow directions. Furthermore, a coefficient is analyzed based on an equation from the literature for the sharp-edged structure, which can be used comparably for the asymmetric orifice. This allows us to reach preliminary assumptions of the losses at an early state of the design process. The following adaptation can be supported by the presented guidance for the optimization process, so that a suitable geometry for the specific boundary conditions can be found. ARTICLE HISTORY KEYWORDSControl structures; flows in pipes and nozzles; hydraulics of renewable energy systems; hydraulic structure design and management; RANS model

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“…The optimum improvement in orifice meter pressure loss and energy consumption is found at a ring diameter ratio βr = 0.5 and a normal distance Lr/D = 0.38, according to optimization results. Adam et al (2016) investigated the effect of the edge angle of a typical orifice on head losses in both directions. This angle causes unequal behavior and affects head losses.…”

Section: Introductionmentioning

confidence: 99%

Effect of orifice-meter shape on discharge coefficient and head loss through it

Assran

shenouda

Mohamed

2022

Preprint

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Flow measurements through pipes and open channels are very important for the management of water resources effectively. Orifice meter is a very common and widely used flow measuring device in pipes as it is very cheap and simple compared with other devices, however, there are many parameters that affect its performance. Also, orifice is used as energy dissipation method in water hammer protection devices and hydroelectric power tunnels. So, experimental research is carried out in the Hydraulic Laboratory of Assuit University to study the effect of orifice geometry on the energy loss through it. Due to head losses occurring at the orifice, a coefficient of discharge (Cd) is used to calculate actual discharge from theoretical discharge. The experimental tests are carried out using four different types of orifice plates: circular, square, triangular, and hexagonal. For each one, the cross-sectional area is changed four times. The orifice is installed on a 10 cm diameter transparent pipe. The flow rate is changed ten times for each orifice. A general correlation equation is developed for the coefficient of discharge based on dimensional analysis. The research concludes that the triangular shape achieves high performance with a lower head loss and a higher coefficient of discharge when compared to the other orifice shapes.

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Head loss coefficient through sharp-edged orifices

Cited by 5 publications

References 2 publications

Design of a Throttled Surge Tank for Refurbishment by Increase of Installed Capacity at a High-Head Power Plant

Design of a Throttled Surge Tank for Refurbishment by Increase of Installed Capacity at a High-Head Power Plant

Design criteria for a type of asymmetric orifice in a surge tank using CFD

Effect of orifice-meter shape on discharge coefficient and head loss through it

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