Flow In Reverse Direction Research Articles

AYURVEDIC PERSPECTIVE OF PRIMARY DYSMENORRHOEA - REVIEW ARTICLE

The medical term for painful period is "dysmenorrhoea". Dysmenorrhoea among adolescents is of primary in nature that is without any pelvic pathology. Among Vimshati yonirogas described in Ayurveda classics Udavarta is men- tioned as a condition with painful and difficult menstruation, so it can be correlated to primary dysmenorrhoea. In this condition the Rajas flow in reverse direction hence the term Udavartini. Women feel immediate relief following discharge of menstrual blood. Normal menstrual flow is the function of Apana vata therefore Apana vata dushti can be considered as the responsible factor for Udavarta. Because of the high prevalence of dysmenorrhoea in adoles- cents and extent of its potential daily interference it should be seriously taken into consideration. Ayurvedic classic textbook along with available modern literatures were referred to make a clear view regarding the concept of Uda- varta and its possible correlation with primary dysmenorrhoea. Keywords: Primary dysmenorrhoea, Udavarta, dysmenorrhea

Probabilistic methodology for estimating the optimal photovoltaic capacity in distribution systems to avoid power flow reversals

The large-scale integration of photovoltaic generation (PVG) on distribution systems (DSs) preserving their technical constraints related to voltage fluctuations and active power (AP) flow is a challenging problem. Solar resources are accompanied by uncertainty regarding their estimation and intrinsically variable nature. This study presents a new probabilistic methodology based on quasi-static time-series analysis combined with the golden section search algorithm to integrate low and high levels of PVG into DSs to prevent AP flow in reverse direction. Based on the analysis of two illustrative case studies, it was concluded that the successful integration of PVG is not only related to the photovoltaic-cell manufacturing prices and conversion efficiency but also with the manufacturing prices of power electronic devices required for reactive power control.

Reducing the impact of DG on distribution networks protection with reverse power relay

The assimilation of distributed sources in to existing distribution networks (DN’s) will bring up the several technical, economical and regulatory questions. Conventional distribution system is radial in nature, characterized by a single source feeding a network of downstream feeders. Therefore the voltages decrease towards the end of the feeder from the source, The incidence of distributed generators (DG) in the distribution networks alter the radial nature of distribution, causes the power flow in reverse direction in the event of DG is added in a system, or any fault in the feeding source/end, the DG exceed the local load, that is, towards the high voltage grid, it causes the existing protection system fails to protect the distribution networks against these changes.To solve this problem reverse power relay (RPR) is proposed to protect the system voltage fluctuations, power reversals condition. The proposed Reverse power relay is a directional power relay it monitor the power flow from a generator (centralized) running in parallel with another generator (DG) or the utility. The reverse power relay prevents a reverse power in the network by disconnect the DG from the distribution network under faulted condition. It also estimates the reverse power and proposes corresponding adjustment value to provide solution to protect distribution network as per the relay settings and distribution system changing scenario. The simulations have been performed using mat lab/simulink.

A prototype micro-thermoelectric power generator for micro-electromechanical systems

A prototype micro-thermoelectric power generator (micro-TEG) system based on micro-combustion concept has been developed and presented here. The system consists of Bismuth-Telluride based thermoelectric modules mounted on a 0.5 cm3 volume microcombustor. The hot combustion gases from the microcombustor are allowed to flow in reverse direction through a heating cup to maximize the heat transfer from hot combustion products to thermoelectric modules. The system delivers a maximum power of 2.35 W with a fuel (propane) flow rate of 3.98 g/h. Maximum power is achieved at a voltage of 4.34 V, current 0.54 A with a maximum conversion efficiency of 4.58%. The system generates electric power with an improvement of over 83% in energy conversion efficiency over existing micro-TEG systems.

Electro-Marangoni Effect in Thin Liquid Films

The present paper reports a new drainage model accounting for the electro-Marangoni effect in thin liquid films stabilized by ionic surfactants. It was shown that the liquid outflow during the film drainage drifts charges from the diffuse part of the electrical double layer toward the film rim and thus generates a streaming potential along the film plane. This creates reverse fluxes near the film surfaces due to the requirement for zero electric current in the film. In a previous paper on this model (Tsekov et al. Langmuir, 2010, 26, 4703), the immobile surfaces were assumed. Here, the film surfaces were considered mobile, and surface velocity is controlled by an electro-Marangoni number. It was also shown that the motion of the charges makes the film surfaces more mobile, and they flow in reverse direction to the overall liquid outflow. The theory was validated by experimental data on drainage of planar foam films stabilized by cationic (tetrapentyl ammonium bromide) and anionic (sodium dodecyl sulfate) surfactants. A good agreement between the theoretical prediction and experimental data was found.

A study on the shell wall thinning causes identified through experiment, numerical analysis and ultrasonic test of high-pressure feedwater heater

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which accelerates as the operation progresses. Several nuclear power plants in Korea have undergone this damage around the impingement baffle – installed downstream of the high-pressure turbine extraction steam line – inside numbers 5A and 5B feedwater heaters. At that point, the extracted steam from the high-pressure turbine consists in the form of two-phase fluid at high temperature, high pressure and high velocity. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of number 5 high-pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical analysis results using the FLUENT code and the downscaled experimental data in an effort to determine root causes of the shell wall thinning of the high-pressure feedwater heaters. The numerical analysis and experimental data were also confirmed by the actual wall thickness measured by ultrasonic tests. From the comparison of the results for the local velocity profiles and the wall thinning measurements, the local velocity component only in the y-direction flowing vertically to the shell wall, and not in the x- and z-directions, was analogous to the wall thinning data.

급수가열기 추기노즐 충격판 주변의 동체감육 현상규명을 위한 실험 및 수치해석 연구

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damage, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle - installed downstream of the high pressure turbine extraction steam line - inside number 5A and 5B feedwater heaters. At that point, the extracted steam from the high pressure turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows in reverse direction after impinging the impingement baffle, the shell wall of the number 5 high pressure feedwater heater may be affected by flow-accelerated corrosion. This paper describes the comparisons between the numerical analysis results using the FLUENT code and the down scale experimental data in an effort to determine root causes of the shell wall thinning of the high pressure feedwater heaters. The numerical analysis and experimental data were also confirmed by actual wall thickness measured by an ultrasonic test.

Computation of turbulent flow inside an enclosure with central partition

Knowledge of the distribution of air is essential for proper design of enclosed spaces like clean room, passenger cabins, etc. The flow inside these is characterised by three-dimensionality and turbulence. It depends on factors like geometrical configuration, supply and exhaust locations and internal partitions. The effects of these parameters can be studied by considering the flow through a rectangular enclosure with partition. Computations in such cases are carried out by numerically solving Reynolds Averaged Navier–Stokes (RANS) equations, the results of which depend on the model of turbulence used. To arrive at a suitable model, three advanced turbulence models namely, RNG k–ε, Reynolds stress model and shear stress transport (SST) k–ω are examined by comparing computed results with experimental data. Fluent 6.0 code with implicit option is used as the computing platform. It is found that the SST k–ω model is able to capture complex flow features like the movement of vortices downstream of the partition, flow in reverse direction in the top portion of the enclosure, and exit of flow with swirl.

Subclavian steal syndrome with an unusual presentation

Steal syndrome has been known since 1960 in the medical literature. It is the pathological process in which blood flows in reverse direction and if vessels supplying the intracranial structures are involved, a variety of neurological symptoms may develop. In this paper, we report a case with left subclavian steal syndrome that presented solely by paroxysmal numbness on the right side of the lip and tongue and discuss the clinical importance from the neurological point of view.