Search results for "Flow Rate"
showing 10 items of 166 documents
Some observations on the sensitivity of flow-injection techniques for atomic absorption spectrophotometry
1989
Abstract Different strategies for coupling flow-injection manifolds to atomic absorption spectrometers in order to obtain better sensitivity are compared. Using a T-connector interface, different carriers and flow compensation solvents have been assayed in an attempt to improve the sensitivity of flow-injection analysis. Manganese and copper determinations in sewage sludge have been used as a test system and the analytical parameters of both batch and flow-injection methods are compared.
Atomic fluorescence spectrometric determination of trace amounts of arsenic and antimony in drinking water by continuous hydride generation
1999
A highly sensitive and simple method has been developed for the determination of As(III), total As, Sb(III) and total Sb in drinking water samples by continuous hydride generation and atomic fluorescence spectrometry (HGAFS). For As determination, water samples aspirated in a carrier of 2 mol l(-1) HCl were merged with a reducing NaBH(4) 3%(m/v) solution, with sample and NaBH(4) flow rates of 12.5 and 1.5 ml min(-1) respectively. The hydride generated in a 170 cm reaction coil was transported to the detector with an Ar flow of 400 ml min(-1), and a limit of detection between 5 and 20 ng l(-1) was obtained. For Sb determination, 2.5 mol l(-1) HCl and 2%(m/v) NaBH(4) were employed, with respe…
Spectrophotometric determination of carbaryl by on-line elution after its preconcentration onto polyurethane foam.
2000
Abstract An analytical methodology has been developed for the UV-spectrophotometric determination of carbaryl in waters after its preconcentration onto a polyether type polyurethane foam followed by on-line elution. The aforementioned strategy offers an easy way for in-field sampling and to improve the analytical sensitivity. Several chemical and flow variables (mass of sorbent, sample flow rate, sample volume and carrier flow rate) were studied to ensure the best performance of the system. Recovery studies, carried out on natural water samples spiked with known amounts of carbaryl at concentration levels between 250 and 500 μg l−1, provided recovery percentages between 94 and 105%. A detec…
Numerical analysis of a new cross-flow type hydraulic turbine for high head and low flow rate
2021
Cross-flow turbines have recently been proposed for energy recovery in aqueducts when the outlet pressure is greater than zero, owing to their constructive simplicity and good efficiency within a large range of flow rates and head drops. In the case of high head drop (higher than 150 m) and relatively small discharge (lower than 0.2 m3/s), the traditional design of these turbines leads to very small widths of the nozzle and the runner; as a consequence, friction losses grow dramatically and efficiency drops down to very low values. Standard Pelton turbines require zero outlet pressure and cannot be used as alternatives. A new counter-pressure hydraulic turbine for high head and low flow rat…
A novel pressure regulation system based on Banki hydro turbine for energy recovery under in-range and out-range discharge conditions
2021
Abstract Efficiency improvement of water distribution networks needs to be in place to guarantee a long life period under suitable operating conditions. Excessive pressure is among the well-known issues encountered in water distribution networks which can cause strength damages to the piping system. In order to overcome this drawback and to reach a suitable water pressure delivery, the present work suggests a novel pressure regulation system. This regulation system is consisting of a Banki turbine equipped with a mobile flap as a control device. The suggested pressure regulation system was experimentally and numerically investigated under in-range i.e. like actual water distribution network…
Simulation of stability and dynamics of multistage flash desalination
2011
gPROMS software was used to study the dynamics of a multistage flash desalination brine circulation system (MSF-BR) as a function of major operating parameters. Most of the previous studies focused on MSF-BR dynamic model development however; it gave very little information on dynamic response of the system to the most significant process independent parameters. The present model was first validated against available industrial data of different plants. System dynamics were obtained upon increasing/decreasing several of the operating parameters over a range of ± 15%. Results show that increase/decrease of the cooling seawater flow rate have limited effect on the system dynamics. Increasing/…
A simulation tool for analysis and design of reverse electrodialysis using concentrated brines
2015
Abstract Reverse electrodialysis (SGP-RE or RED) represents a viable technology for the conversion of the salinity gradient power into electric power. A comprehensive model is proposed for the RED process using sea or brackish water and concentrated brine as feed solutions. The goals were (i) reliably describing the physical phenomena involved in the process and (ii) providing information for optimal equipment design. For such purposes, the model has been developed at two different scales of description: a lower scale for the repeating unit of the system (cell pair), and a higher scale for the entire equipment (stack). The model was implemented in a process simulator, validated against orig…
Development of a Membrane Distillation module for solar energy seawater desalination
2012
Abstract Membrane Distillation (MD) processes are gaining growing interest among novel desalination technologies, in particular for small scale applications also coupled with non-conventional energy sources. In the present work an original laboratory scale planar geometry Membrane Distillation unit was designed, built and tested for future coupling with solar energy. Though conceptually simple, the original geometry was developed in order to allow for multi-stage arrangement, compactness, internal heat recovery and possible integration with a polymeric heat exchanger for final brine heating by means of solar energy or waste heat. The laboratory scale unit was tested in order to investigate …
Speed Stochastic Processes and Freeway Reliability Estimation: Evidence from the A22 Freeway, Italy
2013
In this paper, a criterion for predicting the reliability of freeway traffic flow is presented. The idea is based on an analysis of spot speed time series divided into sequences of events of random and homogeneous traffic processes. For each process, the flow rate and density were calculated; then the relationships between parameters of spot speed processes and vehicular density were obtained. Using these relationships and a simulation procedure for the spot speed process, a formulation for predicting the reliability of traffic flow moving along the offside lane on the freeway roadway was derived. Through this formulation and the measurements of flow rate and speed, the probability of insta…
Once t hrough m ultistage fl ash d esalination: gPROMS d ynamic and s teady s tate m odeling
2010
This study focuses on modeling the steady state and dynamic behavior of the multistage flash desalination process (MSF) using gPROMS. This modeling tool allows for simultaneous coding of the system dynamics and steady state performance. In addition, it allows the use of the most efficient solvers for a set of non-linear differential and algebraic equations describing the MSF process. The system model and analysis are based on actual plant data that includes 21 flashing stages and a capacity of 378 kg/s (32,000 m3/d). The simulated unit is part of a massive MSF installation in Doha, Kuwait. System's dynamic behavior is simulated by a step change in the input values of the main operating para…