scholarly journals Point-of-use upflow sand filter for rural water treatment using natural local sand: Understanding and predicting pressure drop

2021 ◽  
Vol 1192 (1) ◽  
pp. 012008
Author(s):  
F Abd Lahin ◽  
R Sarbatly ◽  
C Chel-Ken
Keyword(s):  
Pressure Drop ◽  
Particle Density ◽  
Unit Length ◽  
Theoretical Models ◽  
Small Scale ◽  
Sand Filter ◽  
Theoretical Comparison ◽  
Point Of Use ◽  
Rural Water ◽  
Filter Bed

Abstract A simple, small scale upflow sand filter was fabricated using a locally obtained sands at three different rivers in Sabah, Malaysia: Liwagu River (SL), Tamparuli River (ST), and Kaingaran River (SK). The grain size, porosity, bulk density, particle density and sphericity of the sands were characterized to associate with the corresponding pressure drop across the sand bed. The highest pressure drop per unit length for SK, PT, and SL are 15.85 kPa m-1 at 0.747 m s-1 vs, 10.18 kPa m-1 at 0.352 m s-1 vs, and 9.24 kPa m-1 at 0.747 m s-1 vs, respectively. The pressure drop per unit length at different filter bed depth were plotted, and compared against three theoretical models of Ergun, Kozeny-Carman, and Fair and Hatch. By analyzing the experimental-theoretical comparison using RMSE and Chi-Test, prediction of pressure drop in an upflow sand filter is able to be predicted using the Kozeny-Carman equation preceding filter bed fluidization and subsequently Fair and Hatch’s equation after bed is fluidized.

scholarly journals Small-Scale Spectrum of a Scalar Field in Water: The Batchelor and Kraichnan Models

2011 ◽  
Vol 41 (11) ◽  
pp. 2155-2167 ◽  
Author(s):  
Xavier Sanchez ◽  
Elena Roget ◽  
Jesus Planella ◽  
Francesc Forcat
Keyword(s):  
Scalar Field ◽  
Thermal Gradient ◽  
Theoretical Models ◽  
Measured Data ◽  
Small Scale ◽  
Temperature Profiles ◽  
One Dimensional ◽  
Kraichnan Model ◽  
The One ◽  
Rate Of Dissipation

Abstract The theoretical models of Batchelor and Kraichnan, which account for the smallest scales of a scalar field passively advected by a turbulent fluid (Prandtl > 1), have been validated using shear and temperature profiles measured with a microstructure profiler in a lake. The value of the rate of dissipation of turbulent kinetic energy ɛ has been computed by fitting the shear spectra to the Panchev and Kesich theoretical model and the one-dimensional spectra of the temperature gradient, once ɛ is known, to the Batchelor and Kraichnan models and from it determining the value of the turbulent parameter q. The goodness of the fit between the spectra corresponding to these models and the measured data shows a very clear dependence on the degree of isotropy, which is estimated by the Cox number. The Kraichnan model adjusts better to the measured data than the Batchelor model, and the values of the turbulent parameter that better fit the experimental data are qB = 4.4 ± 0.8 and qK = 7.9 ± 2.5 for Batchelor and Kraichnan, respectively, when Cox ≥ 50. Once the turbulent parameter is fixed, a comparison of the value of ɛ determined from fitting the thermal gradient spectra to the value obtained after fitting the shear spectra shows that the Kraichnan model gives a very good estimate of the dissipation, which the Batchelor model underestimates.

scholarly journals Topological Network Properties of Fractal-Like Metallic Nanoparticle Patterns and Their Effects on Optical Resonances

2018 ◽  
Vol 8 (8) ◽  
pp. 1310
Author(s):  
Naoya Kihara ◽  
Osamu Sakai
Keyword(s):  
Unit Length ◽  
Theoretical Models ◽  
Topological Properties ◽  
Metallic Nanoparticle ◽  
Diffusion Limited Aggregation ◽  
Complex Network Theory ◽  
Geometrical Properties ◽  
Optical Resonances ◽  
Resonance Frequencies ◽  
Network Topologies

Fractal-like nanoparticle two-dimensional patterns forming in diffusion-limited aggregation show variant spatial patterns. However, they have invariant statistical properties in their network topologies, even though their formation is completely in self-assembled processes. One of the outputs from these topological properties is optical resonances at invariant frequencies, which is a required feature of a metamaterial alternative. Fractal-like metallic patterns studied here in both experiments and theoretical models exhibit similar resonance frequencies in the infrared-ray range, and they depend on the unit length of nanoparticles composing arbitrary fractal-like structures. The scheme of analysis applied here using complex network theory does not only reveal the topological properties of the nanoparticle network, but points out their optical and possibly other physical potentials arising from their geometrical properties.

scholarly journals GAMMA RAYS FROM SMALL SCALE STRUCTURES ON LONG COSMIC STRINGS

1993 ◽  
Vol 02 (02) ◽  
pp. 183-195 ◽  
Author(s):  
M. MOHAZZAB ◽  
R. BRANDENBERGER
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Cosmic Strings ◽  
Unit Length ◽  
Formation Rate ◽  
Long Strings ◽  
Small Scale ◽  
Scale Structures ◽  
Cusp Formation ◽  
Small Scale Structures

The formation of cusps on long cosmic strings is discussed and the probability of cusp formation is estimated. The energy distribution of the gamma-ray background due to cusp annihilation on long strings is calculated and compared to observations. Under optimistic assumptions about the cusp formation rate, we find that strings with a mass per unit length μ less than Gμ=10−14 will have an observable effect. However, it is shown that the gamma-ray bursters cannot be attributed to long ordinary strings (or loops).

scholarly journals A23 Seasonal abundance of chironomid larvae in slow sand filter bed

2002 ◽  
Vol 53 (Supplement) ◽  
pp. 41
Author(s):  
K. Hirabayashi ◽  
N. Nakamoto ◽  
S. Tanizaki
Keyword(s):  
Seasonal Abundance ◽  
Sand Filter ◽  
Chironomid Larvae ◽  
Slow Sand Filter ◽  
Filter Bed

Optimizing the pressure drop per unit length of district heating piping networks from an environmental perspective

Energy ◽  
2020 ◽  
Vol 202 ◽  
pp. 117681
Author(s):  
Pengfei Jie ◽  
Wanyue Zhao ◽  
Fating Li ◽  
Fengjun Wei ◽  
Jing Li
Keyword(s):  
Pressure Drop ◽  
Unit Length ◽  
District Heating ◽  
Piping Networks

The Hydrodynamics Studies on Loop Seal in CFBC Boiler Using CFD Analysis

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
M. Vivekanandan ◽  
N. Anantharaman ◽  
M. Premalatha
Keyword(s):  
Pressure Drop ◽  
Circulating Fluidized Bed ◽  
Unit Length ◽  
Mechanical Valve ◽  
Sand Particle ◽  
Cfd Analysis ◽  
Solid Mass ◽  
Mass Fluxes ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Abstract In a circulating fluidized bed (CFB), the loop seal is an important component which recirculates the solids captured by the cyclone to the bottom of the riser and avoids the direct flow of gas from high-pressure riser to the low-pressure cyclone. Most of the CFBC systems employ a Non-Mechanical valve, and its function has been investigated by many researchers. In this work, the flow of solid particle within the loop seal has been studied elaborately, and various design and operating parameters of the loop seal were analyzed in detail using Computational Fluid Dynamics (CFD). The CFD study has handled a loop-seal of dimension 110 mm × 430 mm × 400 mm high. This analysis has been done with a 200 µm sand particle and it is checked for its flow ability through various sizes and by altering the L/H ratio for three solid mass fluxes and for three L/H ratios of loop seal. The rate of solid mass flux depends on the length of the horizontal passage connecting the recycle cycle compartment of the loop seal with the supply chamber and hence the solid flow rate and the pressure difference per unit length are directly proportional to the length of the chamber or passage. Hence, L/H ratio is taken as a driving variable for the optimum performance of loop seal. The CFD analysis results reveal that the aeration of the solid to be used within the loop-seal should be higher than the Minimum Fluidization velocity. Also, keeping the length of the horizontal passage constant and varying the height of the passage will reduce the pressure drop. The pressure drop across the horizontal passage decreases up to a certain L/H ratio after which it increases. By comparing the three L/H ratios, L/H ratio of 2.62 is having a lesser pressure drop for the three mass fluxes. L/H ratio of 2.62 is having a good fluidization phenomenon and also the flow from the recycle chamber is more in comparison to the other L/H ratios. Experimental data from the literature is in good agreement with the CFD results.

Experimental study of the initial stages of wind waves' spatial evolution

2011 ◽  
Vol 681 ◽  
pp. 462-498 ◽  
Author(s):  
DAN LIBERZON ◽  
LEV SHEMER
Keyword(s):  
Energy Transfer ◽  
Growth Rates ◽  
Water Surface ◽  
Wind Waves ◽  
Pressure Fluctuations ◽  
Theoretical Models ◽  
Small Scale ◽  
Wave Flume ◽  
Spatial Growth ◽  
The Mean

Despite a significant progress and numerous publications over the last few decades a comprehensive understanding of the process of waves' excitation by wind still has not been achieved. The main goal of the present work was to provide as comprehensive as possible set of experimental data that can be quantitatively compared with theoretical models. Measurements at various air flow rates and at numerous fetches were carried out in a small scale, closed-loop, 5 m long wind wave flume. Mean airflow velocity and fluctuations of the static pressure were measured at 38 vertical locations above the mean water surface simultaneously with determination of instantaneous water surface elevations by wave gauges. Instantaneous fluctuations of two velocity components were recorded for all vertical locations at a single fetch. The water surface drift velocity was determined by the particle tracking velocimetry (PTV) method. Evaluation of spatial growth rates of waves at various frequencies was performed using wave gauge records at various fetches. Phase relations between various signals were established by cross-spectral analysis. Waves' celerities and pressure fluctuation phase lags relative to the surface elevation were determined. Pressure values at the water surface were determined by extrapolating the measured vertical profile of pressure fluctuations to the mean water level and used to calculate the form drag and consequently the energy transfer rates from wind to waves. Directly obtained spatial growth rates were compared with those obtained from energy transfer calculations, as well as with previously available data.

STUDY ON RELATIONSHIP BETWEEN CONDENSED PARTICLES AND STRUCTURE OF CONDENSATION JET USING 2D IMAGE AND DISCRETE WAVELETS MULTIRESOLUTION

2006 ◽  
Vol 04 (02) ◽  
pp. 227-238
Author(s):  
MOTOAKI KIMURA ◽  
MASAHIRO TAKEI ◽  
YOSHIFURU SAITO ◽  
KIYOSHI HORII
Keyword(s):  
Wavelet Transforms ◽  
Large Scale ◽  
Particle Density ◽  
Small Scale ◽  
Discrete Wavelet ◽  
Discrete Wavelet Transforms ◽  
Two Dimensional ◽  
Condensation Zone ◽  
Two Dimensional Image ◽  
Discrete Wavelets

This paper describes the application of discrete wavelet transforms to the analysis of condensation jets in order to clarify the associated fluid and heat transfer phenomena. An experimentally-obtained, two-dimensional image of the condensation particle density around the jet was decomposed into 7 levels of resolution with their respective wavelengths. Based on the known physical characteristics of turbulent flow around the jet, levels 0 and 1 were shown to represent the large-scale components of the condensation particle density and the higher levels represent the small-scale components. From the wavelet-analyzed images, the width of the condensation zone was obtained and this compared well with the width inferred from temperature measurements. Thus, the method was verified and also provided data not available experimentally.

scholarly journals Enhancing the quality of arsenic-contaminated groundwater using a bio-sand filter with iron-mixed clay pellets

2018 ◽  
Vol 13 (2) ◽  
pp. 285-294
Author(s):  
Borano Te ◽  
Boonchai Wichitsathian ◽  
Chatpet Yossapol ◽  
Watcharapol Wonglertarak
Keyword(s):  
Arsenic Removal ◽  
Arsenic Concentration ◽  
Plug Flow ◽  
Sand Filter ◽  
Influent Water ◽  
Filter Bed ◽  
Clay Pellets ◽  
Flow Head ◽  
Who Guideline

Abstract Many people in Cambodia consume groundwater with arsenic concentrations above the WHO guideline. In this study, an iron-mixed porous pellet adsorbent was put into a lightweight bio-sand filter to treat arsenic. The filter was intermittently charged daily with 30 L influent water until the effluent arsenic concentration exceeded 10 μg/L. The results indicated that the Morrill Dispersion Index was less than 2.0, implying that the filter had preferential plug flow. Head loss accumulation led to flow rate reduction over a period of 30 days. Arsenic removal efficiency was between 97 and 99% for the influent concentration, being in the range 355 to 587 μg/L. No significant leaching of iron or organic carbon was observed. The high dissolved oxygen concentration is likely to have contributed to the aerobic conditions in the filter bed. The filter removed arsenic more efficiently than was achieved in some previous studies and might be suitable to provide household-scale, arsenic-safe drinking water.

Removal of particulates, natural organic matters, and microorganisms in a surface amended slow sand filter

2002 ◽  
Vol 2 (5-6) ◽  
pp. 387-394
Author(s):  
H.-B. Jun ◽  
Y.-J. Lee ◽  
S.-S. Shin
Keyword(s):  
Surface Treatment ◽  
Raw Water ◽  
Sand Filters ◽  
Water Turbidity ◽  
Turbidity Removal ◽  
Sand Filter ◽  
Organic Matters ◽  
Slow Sand Filter ◽  
Natural Organic Matters ◽  
Filter Bed

Removal characteristics of particulates, natural organic matters, and microorganisms with six slow sand filter units were measured with a diameter of 50 mm and packed with sand to a depth of 50, 150, 300, 600, and two 700 mm, respectively. One of the 700 mm depth filters was amended by covering the surface of the filter bed with a prefilter. The raw water turbidity and pH was in the range of 1.5-2.0 NTU, and 7.0-7.7, respectively. Turbidity in each filter effluent was decreased as the depth of filter medium increased. However, a greater part of influent turbidity was removed within the top layer of the slow sand filters. Turbidity removal in the 700 mm depth filter with prefilter was similar to that without the prefilter, however, the removal of particles smaller than 2 mm was improved with the prefilter. The particles greater than 10 mm could be removed within the upper 50 mm depth in the slow sand filter. A greater fraction of the particles smaller than 2 mm was removed within the upper 50 mm, however, they were also removed in the deeper sand bed. The removal efficiency of DBP precursors represented by DOC and UV-254 absorbance was 9.2-31% and 2-31%, respectively. pH drop in the 50 mm depth filter was 0.12, while that in the 700 mm depth filter was 0.19. The effects of surface treatment with prefilter on UVA and DOC were not apparent.

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