Loss Of Orifices Research Articles

Development of an accelerator-based neutron source to prototype Mo-99 production, Part II: A liquid LBE loop under a high vacuum

To provide US domestic supply of Mo-99 without using high-enriched uranium (HEU), a subcritical uranium target assembly (UTA) is irradiated by an accelerator-based neutron source to create Mo-99 through fission. Part I of this work discusses the design of a liquid lead–bismuth eutectic (LBE) windowless target for an accelerator-based neutron source development. Part II discusses how to couple this windowless target to an accelerator operating at an ultra-high vacuum and the subcritical UTA cooled by water at room temperature.Due to the windowless design of the target, the liquid LBE flow shares an ultra-high vacuum (<1.3 × 10−7 Pa or 10−9 Torr) space with the accelerator. As a result of this shared vacuum space, the LBE system must operate at a high vacuum (10−3 ∼ 10−6 Pa or 10−5 ∼ 10−8 Torr). A magnetic rotary motion feedthrough unit utilizes magnetic fluid to allow rotation of the pump while maintaining a high vacuum environment. Prior to testing the LBE system under vacuum, a pump curve measurement is performed to estimate flowrate in the system. This measurement also generates data on orifice loss coefficients, which are compared to correlations in literature. The second experiment investigates vacuum level in the LBE system during operation. High vacuum is maintained (10−3 ∼ 10−5 Pa or 10−5 ∼ 10−7 Torr) during system operation, and a residual gas analyzer (RGA) scan shows that partial pressures of residual gases in the LBE system lower over the duration of LBE system operations. The third experiment investigates the gravity driven liquid LBE flowing out of the target chamber in the return line, which is partially full. If the liquid LBE is not drained quickly enough, flooding in the target chamber could occur. The coefficient n in the Manning equation is found to be around 0.008 s/m1/3. The last experiment performed is a demonstration that a vacuum jacket could provide sufficient thermal insulation to allow coupling between 300 °C LBE loop and a water tank at room temperature. The results from these experiments have influenced the development of the neutron source for the future commercial scale Mo-99 production system.

A theoretical and 1-D numerical investigation on a valve/valveless air-breathing pulse detonation engine

The important operating characteristics of pulsed Pressure Gain Combustion (PGC) propulsion are the pressure gain of the combustor component and the propulsive performance gain of the engine. A ramjet-type valve/valveless air-breathing pulsed detonation engine with a supersonic internal compression inlet is investigated. Based on an ideal thermal cycle, the ideal equivalent pressure ratios (πcb) of the Pulsed Detonation Combustor (PDC) are obtained theoretically which are directly related with the propulsive performance of the engine. By introducing an orifice loss model into the cycles, the critical pressure drop ratios through the orifice for the PDC achieving pressure gain and the engine achieving thrust gain are studied. More influencing factors are investigated by the use of a one-dimensional (1-D) numerical simulation model. The operating characteristics of the pulse detonation engine are investigated with changes of the valve type, the inlet/outlet area ratio of the PDC, the nozzle area ratio, and flight conditions. All these factors can affect πcb of the PDC, and πcb can be optimized by changing the geometry of the engine. The most important influence parameter is the valve type. When using an orifice-type aerodynamic valve, simulation results show that the PDC cannot achieve the pressure gain characteristics. When a supersonic internal compression inlet is introduced to the engine, whether the Pulse Detonation Engine (PDE) can achieve thrust gain comparable with that of an ideal Brayton cycle engine not only is related to the pressure gain of the combustor, but also needs to optimize the engine structure to reduce the total pressure loss.

An approximate model on three-dimensional groundwater infiltration in sewer systems.

Groundwater infiltration through cracked sewer pipes has caused significant economic losses. This paper presents a three-dimensional analytical expression for calculating the steady-state groundwater infiltration rate into sewer systems. As an extension of the previously developed two-dimensional model by the author, this new model can be used to simulate the infiltration through an orifice defect. The derived analytical expression has been validated with experimental results. The new model incorporates all the related resistances during the infiltration process, including the soil head loss and the orifice loss. The soil head loss is assessed with Ergun equation, which involves an inertial loss term in addition to the viscous loss. This has significantly extended the application range of the new expression. A new OS number (the ratio of orifice loss to soil loss) expression is also presented. The order analysis of the OS number expression has demonstrated that in most real cases, the head loss through the soil layer dominates the whole infiltration process.

Detailed evaluation of two phase natural circulation flow in the cooling channel of the ex-vessel core catcher for EU-APR1400

The ex-vessel core catcher of the PECS (Passive Ex-vessel corium retaining and Cooling System) is installed to retain and cool down the corium in the reactor cavity of the EU (European Union)-APR (Advanced Power Reactor) 1400. A verification experiment on the cooling capability of the PECS has been conducted in the CE (Cooling Experiment)-PECS. Simulations of a two-phase natural circulation flow using the RELAP5/MOD3 computer code in the CE-PECS and PECS have been conducted to predict the two-phase flow characteristics, to determine the natural circulation mass flow rate in the cooling channel, and to evaluate the scaling in the experimental design of the CE-PECS. Particularly from a comparative study of the prototype PECS and the scaled test facility of the CE-PECS, the orifice loss coefficient in the CE-PECS was found to be 6 to maintain the coolant circulation mass flux, which is approximately 273.1kg/m2s. The RELAP5 results on the coolant circulation mass flow rate are very similar to the CE-PECS experimental results. An increase in the coolant injection temperature and the heat flux lead to an increase in the coolant circulation mass flow rate. In the base case simulation, a lot of vapor was injected into the downcomer, which leads to an instability of the two-phase natural circulation flow. A super-step design at a downcomer inlet is suitable to prevent vapor injection into the downcomer piping.

J0540305 風力利用を想定した油圧式発熱システムの開発([J054-03]再生可能エネルギー(3))

The purposes of this study are to clarify the validity of the conversion of wind power into thermal energy by using the hydraulic heating system and to consider the optimal method of this system. An oil pump was driven by a DC-motor instead of wind turbine, and the oil increased in temperature by the pressure loss of orifices mounted in a heating element connected to the hydraulic circuit. The power consumed by pressure loss, the effective heating rate, and the oil temperature increase process were measured under several different conditions, for example the number of orifice plates and the space between its plates. As the results of these investigations, it was found that this oil hydraulic heating system using the pressure loss of orifices worked well for the wind power heater.

Numerical Analysis on Transient Internal Pressure Character of Sudden Opening Building Suffer Simple Harmonic Excitation

The theoretical solution of the transient response of the wind-induced internal pressure based on assuming the external pressure is simple harmonic excitation by the linear equation governing the dynamics of internal pressure was presented. The effect of orifice loss coefficient, opening angle, the opening ratio and background porosity factor (Pf) on the transient internal pressure character was analyzed. The result shows: the peak value of the transient internal pressure and the overshooting ratio decreases with the increase of the orifice loss coefficient; the opening angle decides the overshooting effect. The overshooting ratio increases with the opening ratio and presents a decreasing trend while Pf increases; the effect of these factors on steady internal pressure is relatively small.

Trichoscopy: a new frontier for the diagnosis of hair diseases

Trichoscopy is hair and scalp dermoscopy using a handheld dermoscope or polarized light video microscope. This article shows the revised trichoscopic algorithm for common hair loss diseases. For the algorithm for cicatricial alopecia, loss of orifices, micropustules and/or hair tufting with six or more hairs should be carefully observed. When loss of hair orifices cannot be seen in the hair loss area, diagnosis as noncicatricial alopecia is established. Among noncicatricial alopecia, alopecia areata is most commonly encountered and should be mainly considered for differential diagnosis. Therefore, the first check point is yellow dots, black dots or broken hairs. The hallmark of androgenetic alopecia and tinea capitis is hair diameter diversity (≥20%) and comma hairs, respectively. Hair shaft abnormalities can be diagnosed from the characteristics of trichoscopy reported until now.

Trichoscopy for common hair loss diseases: Algorithmic method for diagnosis

In recent years, the usefulness of trichoscopy (scalp dermoscopy) has been reported for hair loss diseases. Here, characteristic trichoscopic features of common hair loss diseases are described using a DermLite II pro or Epilight eight. Characteristic trichoscopic features of alopecia areata are black dots, tapering hairs (exclamation mark hairs), broken hairs, yellow dots and short vellus hairs. In androgenetic alopecia (AGA), hair diameter diversity (HDD), perifollicular pigmentation/peripilar sign and yellow dots are trichoscopically observed. In all cases of AGA and female AGA, HDD more than 20%, which corresponds to vellus transformation, can be seen. In cicatricial alopecia (CA), the loss of orifices, a hallmark of CA, and the associated changes including perifollicular erythema or scale and hair tufting were observed. Finally, an algorithmic method for trichoscopic diagnosing is proposed.

Comparison of Discharge Coefficient Measurements and Correlations for Orifices With Cross-Flow and Rotation

Abstract Gas turbines and jet engines consist of a network of connected cavities beside the main gas path called the secondary air system. These cavities, which are often surrounded by stationary and high angular speed rotating walls are exposed to varying pressure and temperature levels of air or oil contaminated air and are connected to each other by orifices or restrictors. It is vital to control the secondary flow to enable a reliable and efficient engine design, which meets component durability with a minimum of parasitic air consumption. It is essential to understand the flow physics as well as network interdependency in order to minimize the flow consumption and yet meeting engine operating requirements, as well as practical parts component design or manufacturing needs. In this connection, computer network codes containing model conceptions, which can accurately predict orifice flows, are essential. In an effort to provide usable further insight into flows across restrictors, such as orifices, this publication compares test results and orifice loss calculation models from the open literature with the aid of transformation laws and contour plots. The influence of different geometric features is incorporated into a model for the calculation of discharge coefficients. This publication is an extract of the underlying widespread and more detailed ASME paper (Huening, 2008, “Comparison of Discharge Coefficient Measurements and Correlations for Several Orifice Designs With Cross-Flow and Rotation Around Several Axes,” ASME Paper No. GT2008-50976). Minor errors, noticed during adapting, are corrected.

Dermoscopic findings in frontal fibrosing alopecia: report of four cases

Frontal fibrosing alopecia (FFA) is characterized by frontotemporal hair recession and eyebrow loss and by a histopathology identical to lichen planopilaris. Differential diagnosis from other types of alopecia, including alopecia areata (AA), is necessary in some cases. To describe dermoscopic findings of FFA and to investigate the possibility of utilizing dermoscopy as a diagnostic tool for FFA. Four cases of FFA diagnosed by clinical and/or histological findings were examined by dermoscopy. The loss of orifices, perifollicular erythema or scale was seen in all the four cases (4/4), in three cases (3/4) or in two cases (2/4), respectively. None of the cases showed yellow dots characteristic of AA. Immunohistochemistry showed T lymphocyte infiltration into the infundibulum and isthmus. Dermoscopy is a helpful diagnostic tool for FFA especially to distinguish it from AA.

A method for determining orifice loss coefficients in strongly transient compressible liquid flows

The aim of the current work was to devise a method of establishing orifice loss coefficients in highly transient liquid flows. This was motivated by the fact that (i) many physical systems involve liquid transfer through narrow channels between cavities under unsteady conditions, and (ii) such data does not exist in the literature. A test facility was constructed, consisting of a drop-weight tester which operates in conjunction with a test cell comprising a vertically mounted thick-walled cylinder blanked off at the bottom, and containing upper and lower water-filled cavities separated by a plate with a small, sharp-edged orifice (thickness to diameter ratio of four). The upper cavity is enclosed at its top surface by a piston which protrudes beyond the upper section of the cylinder. When a weight is dropped onto the piston, a variation of pressure (p1) occurs in the upper cavity, approximating the shape of a half sinusoid with time, and with a typical half cycle (T) in the range 1.34–2.73 ms. Mass transfer takes place from the upper to the lower cavity, with a commensurate increase of pressure (p2) in the latter. At a certain time p1 and p2 become equal, at which the latter is at its maximum and the former is close to the end of its sinusoidal half cycle. Thereafter, p1 rapidly diminishes to ambient pressure and p2 approaches ambient pressure over a period of about 5T. During this latter phase, p2 exceeds p1, which is consistent with flow reversal. A comprehensive analysis of the system, in conjunction with pressure measurement, enabled experimental loss coefficients to be determined during that time when mass transfer was taking place between the upper and lower cavities (with p1&amp;gt;p2). Values of cd obtained were in the range 0.85–1.2, increasing for the smaller values of T. These data are viewed in the context of the expected steady flow value of 0.79 for this configuration of orifice, and confirm the hypothesis that flow unsteadiness of a sufficiently small time scale has a significant effect on loss coefficients.