scholarly journals Impacts of operational conditions on oxygen transfer rate, mixing characteristics and residence time distribution in a pilot scale high rate algal pond

2018 ◽  
Vol 78 (8) ◽  
pp. 1782-1791 ◽  
Author(s):  
L. A. Pham ◽  
J. Laurent ◽  
P. Bois ◽  
A. Wanko
Keyword(s):  
Water Level ◽  
Flow Rate ◽  
Rotational Speed ◽  
Time Distribution ◽  
Transfer Rate ◽  
Pilot Scale ◽  
High Rate ◽  
Operational Conditions ◽  
Inlet Flow Rate ◽  
The Impact

Abstract Different combinations of operational parameters including water level, paddle rotational speed and influent flow rate were applied to investigate their impacts on mixing characteristics, residence time distribution and gas transfer rate in a pilot-scale high rate algal pond. In closed condition, the paddle rotational speed had a positive correlation with the Bodenstein number (Bo), water velocity and oxygen volumetric mass transfer coefficient (kLaO2) while increasing water level generated a negative impact on these parameters, although the impact of water level on water linear velocity was small. The amplification effect of water level and paddle rotational speed on the sensitivity of Bo and kLaO2 should be noticed. Moreover, paddle rotational speed had more impact on kLaO2 than on Bo. The study in open condition indicated that effective volume fraction had a positive correlation with inlet flow rate and negative correlation with paddle rotation, while the opposite was observed in the case of Peclet number. The impact of water level variation on these parameters was unclear. Both water level and paddle rotational speed had negative impacts on the short-circuiting index, while no correlation was observed when varying inlet flow rate. In this study, the optimal operational conditions included low water level (0.1 m) and medium paddle rotational speed (11.6 rpm).

scholarly journals Computational Analysis on Numerical Simulation of Internal Flow Physics for Pump as Turbine in Renewable Small Hydro Energy Generation

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Du Jianguo ◽  
Daniel Adu ◽  
Emmanuel Acheaw ◽  
Shakir Hafeez ◽  
Eric Ofosu Antw
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Human Life ◽  
Three Dimensional ◽  
Internal Flow ◽  
Hydroelectric Power ◽  
Small Hydropower ◽  
Speed Increase ◽  
Blade Thickness ◽  
The Impact

Energy contributes significantly in almost all aspects of human life as well as economic activities and plays a crucial role in the infrastructural development of a county to alleviate poverty. Generating energy from a renewable source such as small hydropower through the application of pump operating as a turbine mode called Pump as Turbine is one of the best alternatives to provide clean and inexpensive energy. Using Pump as Turbine helps in generating reasonably priced hydroelectric power for communities in underdeveloped counties. This study investigates the effects of internal flow behaviour and performance of Pump as Turbine under different rotational speed and flow rate. The rotational speed is an essential physical parameter as it affects the Pump as Turbine operation. A model-specific speed centrifugal pump model with head 32 (m), flow rate of 12.5 (m3/h) and the rotational speed of 2900 rpm, has been selected for the study. Numerical simulations have been conducted using the k-ω turbulence model to solve three-dimensional (3D) equations. The pump mode experimental data were used to confirm the results for better analysis. The results predicted that vortex and turbulent kinetic energy increase per rotational speed increase. Also, at the higher rotational speed, very high recirculation of flow is detected at the blade suction chamber, although the pressure side has a smooth flow. This study provides beneficial information which will serve as a reference to help improve PAT performance along with selecting PAT for a small hydropower site. Future works will consider the impact of blade thickness and cavitation in Pump as Turbine.

Comparative investigation on the impact of polymeric substances on membrane fouling during sub-critical and critical flux operation of a municipal membrane bioreactor

2008 ◽  
Vol 58 (9) ◽  
pp. 1849-1855 ◽  
Author(s):  
S. Lyko ◽  
T. Wintgens ◽  
T. Melin
Keyword(s):  
Membrane Fouling ◽  
Pilot Scale ◽  
Comparative Investigation ◽  
Hollow Fibre ◽  
Size Exclusion ◽  
Dominant Factor ◽  
Permeate Flux ◽  
Critical Flux ◽  
Operational Conditions ◽  
The Impact

Soluble organic macromolecules are ubiquitous in activated sludge supernatant. For the operation of membrane bioreactors (MBR) this group of substances is considered as the dominant factor causing severe membrane fouling due to the concentration polarisation phenomenon. The well established critical flux concept for the characterisation of membrane bioreactor's operation limits is based on filtration data only. As there is an cause-and-effect relation between the partial retention of organic compounds and the limited flux according the critical flux concept the aim of this study was to draw a comparison between different permeate fluxes on the retention of organic macromolecules. Thus, a municipal pilot-scale MBR with three capillary hollow fibre membrane modules was operated in sub critical, critical and supercritical flux mode, respectively and the retention of macromolecules was quantified by size exclusion chromatography. Three permeate extraction pumps allow a simultaneous operation with different operational conditions for each membrane module and proved the crucial impact of permeate flux on the fouling rate. The interchange of these conditions gave evidence of an optimised start-up procedure for MBRs characterised by higher permeate fluxes. An increased flux causes both a higher retention of soluble macromolecules and subsequent a higher fouling rate.

Evaluation of Flocs Size inside the Blanket Clarifier

2012 ◽  
Vol 518-523 ◽  
pp. 3687-3690
Author(s):  
Li Qing Zhang ◽  
Gang Zhang
Keyword(s):  
Flow Rate ◽  
Water Concentration ◽  
Average Diameter ◽  
Pilot Scale ◽  
Raw Water ◽  
Operational Conditions ◽  
Water Plant ◽  
Theoretical Predictions ◽  
Experimental Works ◽  
Average Size

Flocs size is an important parameter in the blanket clarifier process, hence, it is necessary to investigate flocs average diameter in different blanket height to achieve optimum operation parameters of the process. To investigate the flocs size under different operational conditions，flocs were sampled from different locations of the blanket in various operating stages to analyze its size. Experimental works with water plant wastes flocculated with polyacrylamide (PAM) suspended in a pilot-scale blanket confirmed the theoretical predictions. Change in operational conditions such as raw water concentration and up-flow rate would affect the blanket flocs size, there exists a linear relationship between up-flow rate and flocs average size, and flocs size were improved along with the increase of raw sludge concentration. The experimental results identified an inverse proportion between flocs average size and the blanket depth, the average flocs diameter increased along with the depth of the blanket.

Adapting UASB technology for sewage treatment in Palestine and Jordan

2008 ◽  
Vol 57 (3) ◽  
pp. 361-366 ◽  
Author(s):  
Nidal Mahmoud ◽  
Grietje Zeeman ◽  
JulesB. van Lier
Keyword(s):  
Sewage Treatment ◽  
Cost Effective ◽  
Pilot Scale ◽  
High Rate ◽  
Uasb Reactor ◽  
Temperate Climate ◽  
Model Calculations ◽  
Methanogenic Activity ◽  
Operational Conditions ◽  
Sludge Stabilization

High rate anaerobic technologies offer cost-effective solutions for “sewage” treatment in the temperate climate of Palestine and Jordan. However, local sewage characteristics demand amendments to the conventional UASB reactor design. A solution is found in a parallel operating digester unit that stabilises incoming solids and enriches the UASB sludge bed with methanogenic activity. The digester operational conditions were assessed by operating eight CSTRs fed with primary sludge. The results showed a high degree of sludge stabilization in the parallel digesters at SRTs≥10 and 15 days at process temperatures of 35 and 25°C, respectively. The technical feasibility of the UASB-digester combination was demonstrated by continuous flow pilot-scale experiments. A pilot UASB reactor was operated for 81 days at 6 hours HRT and 15°C and was fed with raw domestic sewage. This period was subsequently followed by an 83 day operation period incorporating a parallel digester unit, which was operated at 35°C. The UASB-digester combination achieved removal efficiencies of total, suspended, colloidal and dissolved CODs of respectively 66, 87, 44 and 30%. Preliminary model calculations indicated that a total reactor volume of the UASB-digester system corresponding to 8.6 hours HRT might suffice for sewage treatment in Palestine.

scholarly journals The Research of the Suitability of Hydrostatic Water Level Sensor to Measure Storm Water Runoff Flow Rate with the Focus on the Influence of Sediments

2017 ◽  
pp. 336-344
Author(s):  
Vilmantė Karlavičienė ◽  
Raimondas Zaborovskis ◽  
Vaidas Vinciūnas ◽  
Mindaugas Rimeika
Keyword(s):  
Water Level ◽  
Flow Rate ◽  
Urban Areas ◽  
Experimental Studies ◽  
Storm Water ◽  
Water Runoff ◽  
Storm Water Runoff ◽  
Accuracy Of Measurements ◽  
Level Sensor ◽  
The Impact

Since most of the contaminants in surface waters fall with storm water runoff, it is very important to correctly describe the content of pollutants discharging with them (kilograms or tons) for a given unit of time (hour, shift, day, month or year). Measurements are complicated by the fact that the flow rate and pollutant concentration is very variable over time. The aim of the research was to determine the grain size of sweepings accumulated on the surfaces of the researched territory and to investigate the impact of storm water runoff sediments on the accuracy of measurements of water level height using the hydrostatic water level sensor. For the experiment four typical Vilnius city streets, two storm water runoff treatment plants and also the streets sweeping machine was chosen. Storm water runoff in urban areas has an abundance of sediment, therefore, studying the hydrostatic water level sensor DI 240 Diver suitability to determine storm water runoff flow rate, for the experimental studies the impact of sludge and sand for measuring accuracy was chosen. Particles with diameters ranging from 0.315 to 0.630 mm consisting the maximum weight (the average value of 24 g per 100 g of the sample) of street sweepings. Storm water runoff treatment plants sediments are approximately 60% of the smallest particles with a size of less than 0.05 mm. Particles of less than 0.25 mm consisting about 80% of sediment. During laboratory and full scale tests it was determined, that there is no significant affect of sediments on the accuracy of the hydrostatic water level sensor measurements. The average square error (standard deviation) was 0.567 cm when the measurement uncertainty was 0.0021 cm.

scholarly journals Efficiency of Twin-Screw Extrusion of Biodegradable Poly (Butylene Succinate)-Wheat Bran Blend

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 424
Author(s):  
Emil Sasimowski ◽  
Łukasz Majewski ◽  
Marta Grochowicz
Keyword(s):  
Polymer Blend ◽  
Flow Rate ◽  
Wheat Bran ◽  
Rotational Speed ◽  
Twin Screw Extrusion ◽  
Butylene Succinate ◽  
Extrusion Processing ◽  
Screw Extrusion ◽  
Twin Screw ◽  
The Impact

Unmodified poly (butylene succinate) (PBS) is characterized by very good processability; however, after the incorporation of various fillers of plant origin, its processing becomes much more complicated and its properties are significantly affected. Detailed studies of the processing aspects of PBS/wheat bran (WB) biocomposition are lacking, despite the addition of WB having a significant impact on both the production efficiency and the properties of end products. This research paper presents test results of the co-rotating twin-screw extrusion processing of a biodegradable polymer blend, the matrix of which was PBS, with WB as the filler. In undertaking this task, we examined the impact of extruder screw rotational speed and WB content on the characteristics of extrusion processing, as well as on certain thermal, physical, structural and processing properties of the obtained blend. The WB introduced to the blend was in the form of a selected fraction with particles smaller than 0.2 mm. The measurements were conducted using the Design of Experiment (DOE) methods, which enabled establishing the studied relationships in the form of polynomials and response surfaces. The determined extrusion process characteristics covered the impact of screw rotational speed and WB content on the mass flow rate of the processed blend and its pressure, the screw drive torque and specific energy consumption. The studies of the obtained polymer blend included determining the impact of the aforementioned variable factors on the melt flow rate (MFR) index, chemical structure (FTIR), thermal properties (differential scanning calorimetry (DSC), thermogravimetry (TG), derivative thermogravimetry (DTG)), p-v-T relationships, microstructure, density and moisture absorbance. Analysis of variance (ANOVA) was used to assess the effect of individual variable factors. The results of this work are presented, inter alia, using Pareto charts of standardized effects, which illustrate the influence of individual terms of the determined regression equations on the studied quantity.

Transient Characteristics of a Closed-Loop Pipe System During Pump Stopping Periods

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Dazhuan Wu ◽  
Peng Wu ◽  
Shuai Yang ◽  
Leqin Wang
Keyword(s):  
Kinetic Energy ◽  
Flow Rate ◽  
Rotational Speed ◽  
Closed Loop ◽  
Transient Flow ◽  
Operating Conditions ◽  
Rotational Inertia ◽  
Transient Characteristics ◽  
Pipe System ◽  
The Impact

In order to study the transient characteristics of a closed-loop pipe system with room temperature water, experiments were carried out based on different pump stopping periods from rate rotational speed to zero. Various stopping periods were realized by changing the rotational inertia of the rotors, controlling the frequency of the motor and braking the shaft. Experimental results of different operating schemes were compared, and transient flow rate of the pipe system and transient characteristics of the pump were analyzed. The influences of the kinetic energy of the loop fluid and pump rotors to the stopping periods were summarized. Results show that rapid change of the pump operating conditions occurs during the stopping period and transient flow rate of the pipe system and characteristics of the pump depend largely on the way of stopping. The kinetic energy stored in the pump can drive the impeller keeping rotating for more time after the motor is shutdown. Due to the kinetic energy stored in the loop pipe, the flow rate does not reach zero immediately after the rotational speed reaches zero. The inertia of pump rotor and fluid inertia affect the impact of fluid flow and the duration of the loop during pump stopping period.

The Impact of the Multiple Reference Frame Interface on Modelling the Interaction Between IGVs and the Impeller in Turbocharger Compressors

2017 ◽  
Author(s):  
Xiangjun Li ◽  
Stephen Spence
Keyword(s):  
Flow Field ◽  
Mass Flow Rate ◽  
Reference Frame ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Axial Position ◽  
High Rotational Speed ◽  
The Impact ◽  
Multiple Reference

In this paper numerical investigations are presented of how the axial position of the multiple reference frame (MRF) stator-rotor interface between the inlet guide vanes (IGVs) and the impeller would influence the predicted flow field for a turbocharger centrifugal compressor when simulated by the steady RANS method. In the first step, a total of three different axial positions of the MRF IGV-impeller interface were considered and compared with the results of an unsteady simulation to evaluate their accuracy. The results showed that the choice of the MRF interface location significantly influenced the predicted overall performance. At the lower rotational speed, the peak efficiency varied by 1.3% and the corresponding total pressure ratio varied by 0.022. At the high rotational speed, the different axial locations of the MRF interface varied the predicted choke point by 0.012 normalized mass flow rate. The mass flow rate of the near surge (NS) point was over estimated at both the high and low rotational speed by at least 0.038 normalized mass flow rate. Consideration of the flow field suggested that the MRF interface between the IGV and the impeller should be placed towards the upstream side of the available region to avoid being unphysically influenced by its interaction with the non-uniform pressure in the downstream subsonic flow field and to enable a more accurate prediction of the extent of the inducer shock in transonic operating situations. Based on this understanding, a further improvement was made for the setting of the MRF interface by employing a polyline interface. This achieved a more accurate numerical result for the NS operating point at low rotational speeds. The position of the MRF interface for modelling IGVs in a turbocharger compressor should be suitably chosen according to the objectives of the numerical study.

scholarly journals Spatial Positioning and Operating Parameters of a Rotary Bell Sprayer: 3D Mapping of Droplet Size Distributions

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 165 ◽  
Author(s):  
Adnan Darwish Ahmad ◽  
Binit B. Singh ◽  
Mark Doerre ◽  
Ahmad M. Abubaker ◽  
Masoud Arabghahestani ◽  
...  
Keyword(s):  
Droplet Size ◽  
Flow Rate ◽  
Rotational Speed ◽  
Operating Parameters ◽  
Size Distributions ◽  
Theoretical Formulation ◽  
Wide Range ◽  
Droplet Sizes ◽  
Spatial Positioning ◽  
The Impact

In this study, we evaluated the fundamental physical behavior during droplet formation and flow from a rotary bell spray in the absence of an electrostatic field. The impact of a wide range of operating parameters of the rotary bell sprayer, such as flow rates, rotational speeds, and spatial positioning, on droplet sizes and size distributions using a three-dimensional (3-D) mapping was studied. The results showed that increasing the rotational speed caused the Sauter mean diameter of the droplets to decrease while increasing flow rate increased the droplet sizes. The rotational speed effect, however, was dominant compared to the effect of flow rate. An increase in droplet size radially away from the cup was noted in the vicinity of the cup, nevertheless, as the lateral distances from the cup and rotational speed were increased, the droplet sizes within the flow field became more uniform. This result is of importance for painting industries, which are looking for optimal target distances for uniform painting appearance. Furthermore, the theoretical formulation was validated with experimental data, which provides a wider range of applicability in terms of environment and parameters that could be tested. This work also provides an abundance of measurements, which can serve as a database for the validation of future droplet disintegration simulations.

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