Hydraulic Characteristics of Small-Scale Constructed Wetland Based on Residence Time Distribution

2021 ◽  
pp. 1-19
Author(s):  
Rongzhen Wang ◽  
Lirong Xu ◽  
Xiangxi Xu ◽  
Zhenghe Xu ◽  
Xinwen Zhang ◽  
...  
2021 ◽  
Vol 617 ◽  
pp. 118625 ◽  
Author(s):  
Minyoung Kim ◽  
Negin Nejatishahidein ◽  
Ehsan Espah Borujeni ◽  
David J. Roush ◽  
Andrew L. Zydney ◽  
...  

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1896
Author(s):  
Bolin Hu ◽  
Xiaoqiang Zhang ◽  
Zhaofeng Wang ◽  
Zixian Wang ◽  
Yuanfan Ji

This paper uses computational fluid dynamics (CFD) to simulate flow field distribution inside an electrochemical descaling reactor in three dimensions. First, the reactor flow field was obtained by steady-state simulation, and the grid independence was verified. Then, the steady state of the flow field was judged to ensure the accuracy of the simulation results. Transient simulations were performed on the basis of steady-state simulations, and residence time distribution (RTD) curves were obtained by a pulse-tracing method. The effects of plate height and plate spacing on reactor hydraulic characteristics (flow state and backmixing) were investigated using RTD curves, and the results showed that increasing the plate height and decreasing the plate spacing could make the flow more similar to the plug flow and reduce the degree of backmixing in the reactor. The flow field details provided by CFD were used to analyze the reactor flow field and were further verified to obtain the distribution patterns of dead and short circuit zones. Meanwhile, information regarding pressure drops was extracted for different working conditions (490, 560, and 630 mm for pole plate height and 172.6, 129.45, and 103.56 mm for pole plate spacing), and the results showed that increasing the pole plate height and decreasing the pole plate spacing led to an increased drop in pressure. In this case, a larger pressure drop means higher energy consumption. However, increasing the pole plate height had a smaller effect on energy consumption than decreasing the pole plate spacing.


1998 ◽  
Vol 37 (12) ◽  
pp. 43-47 ◽  
Author(s):  
Bob Newell ◽  
Jeff Bailey ◽  
Ashraful Islam ◽  
Lisa Hopkins ◽  
Paul Lant

This paper presents a technique for configuring wastewater process simulations so that the hydraulic characteristics are similar to the real plant. Residence time distribution (RTD) tests are performed on two biological nutrient removal pilot plants. The RTD tests proved valuable for evaluating mixing effectiveness, volume utilisation and for determining an appropriate hydraulic topology for the dynamic models of the pilot plants. As a result of this work, simulation execution times became much faster due to a significant reduction in the number of effective stirred tanks required in the model. The work also identified short circuiting and dead zones in the pilot plants.


2013 ◽  
Vol 859 ◽  
pp. 15-18
Author(s):  
Pei Tao ◽  
Tie Hong Song ◽  
Fang Zhang

By using Chlorides (Cl-) as the tracer, the residence time distribution (RTD) method was applied to study the hydraulic characteristic influences of hydraulic retention time (HRT) on the opposite folded plate reactor and the plate baffle reactor under the condition of steady operation of both clear and sludge water. Under the condition of the same HRT, dead zone of opposite folded plate reactor was less than the one of flat plate reactor.


2017 ◽  
Vol 19 ◽  
pp. 111
Author(s):  
HW Yussof ◽  
SS Bahri ◽  
AN Phan ◽  
AP Harvey

<p>A recent development in oscillatory baffled reactor technology is down-scaling the reactor, so that it can be used for the applications such as small-scale continuous production of bioethanol. A mesoscale oscillatory baffled reactor (MOBR) with central baffle system was developed and fabricated at mesoscales (typically 5 mm diameter). This present work aims to analyse the mixing conditions inside the MOBR by evaluating the residence time distribution (RTD) against the dynamic parameters of net flow Reynolds number (<em>Re</em><em><sub>n</sub></em>) at 4.2, 8.4 and 12.6 corresponding to flow rates of 1.0, 2.0 and 3.0 ml/min respectively, oscillatory Reynolds number (<em>Re</em><em><sub>o</sub></em>) between 62 to 622, and Strouhal number (<em>Str</em>) between 0.1 to 1.59. The effect of oscillation frequency and amplitude on RTD performance were studied at frequency, amplitude, and velocity ratio ranging from 4 to 8 Hz, 1 to 4 mm and 1 to 118, respectively. Effect of oscillation frequency has resulted in the variance of the RTD increased as the oscillation frequency increased from 5 Hz to 8 Hz and peak at 6 Hz of 0.264. A further increase in the frequency above 5 Hz caused the RTD to slightly broaden and positively skewed. At frequency of 5 Hz, the RTD profiles were close to Gaussian form for all tested amplitude values from 1 mm to 4 mm. At low amplitudes, i.e. xo = 1 mm, the variance exhibited its minimum around 0.842 at <em>Re</em><em><sub>o</sub></em><em> </em>=156. An increase in <em>Re</em><em><sub>o</sub></em><em> </em>above 300 resulted in increased in the variance rapidly to 1.28, and later eliminated the plug flow behaviour and the reactor behaved similar to a single continuous stirred tank reactor.</p><p>Chemical Engineering Research Bulletin 19(2017) 111-117</p>


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