Showing papers on "Laminar flow reactor published in 2022"
TL;DR: In this article , an experimental study of the unforced laminar-to-turbulent transition in pipe flow is performed using pressure measurements and visual observations, and the entropy change and force balance are examined, and peak powers are measured through fast Fourier transform analysis at various Reynolds numbers.
Abstract: This paper describes an experimental study of the unforced laminar-to-turbulent transition in pipe flow. Two pipes with different length-to-diameter ratios are investigated, and the transition phenomenon is studied using pressure measurements and visual observations. The entropy change and force balance are examined, and the peak powers are measured through fast Fourier transform analysis at various Reynolds numbers. Visual observations show that the flow structure changes at the Reynolds numbers corresponding to the peak powers. There is no clear dependency of the transition on the ratio of pipe length to diameter. The flow conditions are classified as laminar flow, transitions I, II, and III, and turbulent flow, separated by Reynolds numbers of approximately 1200, 2300, 7000, and 12 000, respectively. The transition at a Reynolds number of 1200 is caused by the force balance between the laminar and turbulent flows. The other transitions are related to the flow condition in the development region upstream of the pipe flow region. That is, the laminar-to-turbulent transition in the development region affects the transition condition in the downstream pipe flow. The laminar and turbulent development length ratios derived from the entropy changes are in reasonable agreement with the formulas for both laminar and turbulent flows. At large Reynolds numbers, the laminar flow condition will be established through the creation of a laminar-flow velocity profile at the entrance to the pipe.
9 citations
TL;DR: In this paper , special elements are inserted into an annular thin-film UVC reactor to guide the laminar flow to achieve sufficient inactivation of E. coli and Saccharomyces cerevisiae.
Abstract: In this paper special elements are inserted into an annular thin film UVC reactor to guide the laminar flow. These “Fluid Guiding Elements” (FGE) divide the flow into three separated laminar currents that are alternatingly directed through a small gap of 0.6 mm facing the UV source by turns. Computational fluid dynamic simulations have been used to visualize the flow dynamics inside the reactor. The residence time distribution and the Bodenstein number show an increase of back mixing in the reactor with the elements. An Iodide/iodate actinometry comparison has shown a better dose distribution throughout the treated volume based on the FGE. The inactivation of E. coli DH5α as an exemplary organism could be improved by more than 4 log levels after 5 passes through the reactor using the FGE independent of the flow rate. The absorbance of a model solution was varied by different dye concentrations and the use of FGE improve the inactivation of Saccharomyces cerevisiae. The stabilization of liquid foods before bottling is a crucial aspect. The consumers often do not accept a chemical additive like sulphites in wine or dimethyl carbonate in juices. A physical alternative is the UV-C Treatment. In contrast to a turbulent flow a laminar flow has a far lower pressure drop. Therefore, a lower amount of energy is needed to pump the liquid. This study shows that with fluid guiding elements a sufficient inactivation can be achieved with laminar flow. • Improving a thin-film reactor by additive manufactured fluid guiding elements (FGE). • Efficient dose distribution of UV-C by FGE in laminar liquid flow. • Inactivation of E. coli and Saccharomyces cerevisiae by ≥5 log in opaque liquids in laminar flow.
4 citations
TL;DR: In this article , the effect of the coloration liquid Reynolds number and its velocity distribution on the uptake behavior of acid dye molecules on silk fabric under laminar flow status was explored for the first time by using a self-built special fluid dynamics coloration machine.
2 citations
TL;DR: In this paper , the authors investigated the steady and transient behavior of annular flows in a partially filled axially rotating pipe and found flow mode boundaries between the non-annular flow and the annular flow.
Abstract: In rotary tube reactors, rotary evaporators, or rotary atomizers, liquid is transported through a partially filled axially rotating pipe. The flow is annular when the pipe rotation is fast enough, as in most engineering applications; in this research, we investigated the steady and transient behavior of annular flows in a partially filled axially rotating pipe. First, the governing equations of a laminar annular flow were derived, solved, and verified. Then, the theory was used to study the transient flow behavior. The responses of the outlet flowrate to inlet flowrate variations and pressure fluctuations were investigated. To clarify the system parameters in which the theory holds, we also conducted experiments to find flow mode boundaries between the non-annular flow and the annular flow. Steady state solutions of the theory were then used to find system parameters in which the flow is laminar. The effects that a screw inserted inside the pipe has, on both the flow mode boundaries and the transient flow characteristics, are also demonstrated. To the best of our knowledge, this is the first inspection of the transient characteristics of an annular flow and the effects of an inserted screw on this type of flow.
1 citations
03 Jan 2022
TL;DR: In this paper , the behavior of multiple laminar jets in contact with each other was studied and the cross-sectional geometry through which the jet flows was analyzed. But, the experimental results were compared with computational results for the time and cost efficiency of the related study in the field of propulsion.
Abstract: Study of the laminar jets is vital because of its usage in propulsion unit. The carburetors need the jets to be streamlined for the better mixing of fuel with the air. There is a limited study on the behavior of laminar jets in contact, especially multiple jets. In this paper, we parametrically studied the behavior of multiple laminar jets in contact with each other. Though the coalescence and non-coalescence of the laminar jets depends on the velocity of jet and the angle at which it flows from the reference frame. It is notable that the pattern observed is based on the cross-sectional geometry through which the jet flows. The experimental study is compared with computational results for the time and cost efficiency of the related study in the field of propulsion. It is quite intriguing to know that this study can also dominate the field of biology.
1 citations
TL;DR: In this paper, a 2D model and a simplified 1D model were used to simulate carbon nanoparticle synthesis via ethylene pyrolysis in laminar flow, and the results showed that radial diffusion sufficiently mixes the gas phase species along the radius to approximate plug flow.
1 citations
TL;DR: In this article , the authors investigated the effect of pulsation on the transport process in a 2D microchannel, where the working fluid is considered as water which is made to flow in the flow disturbing microchannel whiles the microchannel walls were kept at a uniform temperature.
Abstract: Abstract: The present work investigates the effect of pulsation on the transport process in a 2D microchannel. The inlet velocity varies sinusoidally in time at a constant dimension less frequency (St=10) and amplitude of 0.8. The working fluid is considered as water which is made to flow in the flow disturbing microchannel whiles the microchannel walls were kept at a uniform temperature. The solution of two-dimensional Navier-Stokes equation was performed using the SIMPLE algorithm with the momentum interpolation technique. The simulations were performed in the laminar regime within the Reynolds number range between 100- 500 for the microchannel. The results of pulsating flow simulations had been analysed and compared with nonpulsating flow simulations. It is observed that the effect of pulsation in flow interrupting ribbed microchannel is significant and more enhancement of heat transfer is observed at higher Reynolds number while keeping the friction factor within tolerable limits
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TL;DR: In this article , an experimental study of the unforced laminar-to-turbulent transition in pipe flow is performed using pressure measurements and visual observations, and the entropy change and force balance are examined, and peak powers are measured through fast Fourier transform analysis at various Reynolds numbers.
Abstract: This paper describes an experimental study of the unforced laminar-to-turbulent transition in pipe flow. Two pipes with different length-to-diameter ratios are investigated, and the transition phenomenon is studied using pressure measurements and visual observations. The entropy change and force balance are examined, and the peak powers are measured through fast Fourier transform analysis at various Reynolds numbers. Visual observations show that the flow structure changes at the Reynolds numbers corresponding to the peak powers. There is no clear dependency of the transition on the ratio of pipe length to diameter. The flow conditions are classified as laminar flow, transitions I, II, and III, and turbulent flow, separated by Reynolds numbers of approximately 1200, 2300, 7000, and 12 000, respectively. The transition at a Reynolds number of 1200 is caused by the force balance between the laminar and turbulent flows. The other transitions are related to the flow condition in the development region upstream of the pipe flow region. That is, the laminar-to-turbulent transition in the development region affects the transition condition in the downstream pipe flow. The laminar and turbulent development length ratios derived from the entropy changes are in reasonable agreement with the formulas for both laminar and turbulent flows. At large Reynolds numbers, the laminar flow condition will be established through the creation of a laminar-flow velocity profile at the entrance to the pipe.
TL;DR: In this paper , the change in velocity, pressure drop, frictional factor and temperature distribution in the thermal layer across the liquid in the laminar flow is investigated, and various boundary conditions are assumed and the conservation of energy, momentum are also considered.
Abstract: The study of flow of liquids in a circular pipe has been studied for a long time. The theoretical and numerical analysis of viscous fluid is very important in the field of physics, engineering and even in medicine. In any fluid flow, the Napier-Stokes equation are very important to study the nature of flow. On the basis of Reynold number, the flow is either classified as laminar or turbulent. When the heat is supplied to a circular pipe with a liquid having laminar flow, the velocity, rate of flow of volume, temperature gradient, etc. are changed. This study aims to investigate the change in velocity, pressure drop, frictional factor and temperature distribution in the thermal layer across the liquid in the laminar flow. Various boundary conditions are assumed and the conservation of energy, momentum are also considered.
TL;DR: In this paper , the authors investigated numerically the onset of the transition from steady to unsteady laminar flow regime in a three dimensional complex geometry and found that at Re = 400, the symmetry of the flow is destroyed in the second and the third geometric periods whereas it still remains present in the first period which indicates the first step towards the transition.
05 Dec 2022
TL;DR: The authors demonstrate a benchtop jet flow that exhibits persistent laminar flow beyond a Reynolds number of 116,000, a value limited only by the maximum flow-generating capacity of the current facility.
Abstract: Accurate prediction of the transition from laminar flow to turbulence remains an unresolved challenge despite its importance for understanding a variety of environmental, biological, and industrial phenomena. Well over a century of concerted effort has aimed toward a quantitative, mechanistic explanation of Osborne Reynolds' seminal observation of transition to turbulence in pipe flow, typically occurring when the ratio of inertial and viscous fluid dynamic forces -- the eponymous Reynolds number -- is approximately 2000. These studies have been confounded by subsequent observations that the Reynolds number at which transition occurs can be delayed to values as high as 100,000. This record-high laminar Reynolds number has not been exceeded in any similar flow configuration for more than 70 years, however, as it required experiments to be conducted using pipe lengths of up to 18 meters housed within a bomb shelter to eliminate ambient disturbances to the flow. Here, we demonstrate a benchtop jet flow that exhibits persistent laminar flow beyond a Reynolds number of 116,000, a value limited only by the maximum flow-generating capacity of the current facility. High-speed videography of the jet shape and flow velocimetry within the jet confirm the laminar nature of the flow, even in the presence of visible ambient flow disturbances arising from non-idealities in the facility design. The measured spatial evolution of the velocity profile within the jet, approaching a "top hat" shape with increasing downstream distance, appears to promote persistence of the laminar flow. These results suggest the existence of an empirically accessible flow regime in which turbulence might be circumvented at arbitrarily high Reynolds numbers.
TL;DR: In this article , the influence of hydrodynamic conditions in Kenics static mixer, which acts as a multifunctional reactor, on precipitation kinetics of barium sulfate is investigated.
Abstract: In this paper, the influence of hydrodynamic conditions in Kenics static mixer, which acts as a multifunctional reactor, on precipitation kinetics of barium sulfate is investigated. The investigated range of the Reynolds number varied between 500 and 5000, which covered both laminar and turbulent flow regimes. In all experiments, the relative supersaturation was maintained at the constant level (s = 205). The obtained precipitate was collected and used for crystal size distribution (CSD) determination. On that basis, the kinetic parameters of the process were calculated using the mixed suspension mixed product removal (MSMPR) mathematical model of the process. It was found that for the whole investigated range of Reynolds number, the mixing conditions were satisfactory. CSD analysis showed that in the laminar regime, a clear tendency in crystal behavior could not be noticed. However, during the analysis of the turbulent regime, the presence of a critical Reynolds number was noticed. Above this value, there is a change in the flow pattern, which results in a change of kinetic parameters (B, G), as well as manifests in a form of a decrease in the value of mean diameters of crystals. The flow pattern change is caused by the geometry of the reactor’s inserts.