Simulation of the Performance of the Venturi Scrubber for an Advanced Reactor Containment Venting Conditions

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Goel Paridhi ◽  
K. Nayak Arun
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Gas Flow ◽  
Pressure Profile ◽  
Absorption Efficiency ◽  
Severe Accident ◽  
Mitigation Measures ◽  
Liquid Loading ◽  
Venturi Scrubber ◽  
Iodine Absorption

Abstract Post Fukushima, nuclear plants are being retrofitted with severe accident mitigation measures. For attaining depressurization of the containment and mitigate the consequences of the release of the radioactivity to the environment during a severe accident condition, filtered containment venting systems (FCVS) are proposed to be installed in existing reactors and being designed for advanced reactors. The design of FCVS is particular to the reactor type. The FVCS configuration considered in this paper comprises of a manifold of venturi scrubber enclosed in a scrubber tank along with metal fiber filter and demister for an advanced Indian reactor. This study focuses on the assessment of the design of the venturi scrubber for the reactor conditions at which venting is carried out through a numerical model. The numerical model is first validated with experiments performed for prototypic conditions. The predicted pressure drop and the iodine absorption efficiency were found to be in good match with the experimental measurements. Subsequently, the model is implemented for predicting the hydrodynamics, i.e., pressure drop, droplet sizes and distribution, and iodine absorption for prototypic conditions. The hydrodynamics, i.e., pressure profile in the venturi scrubber showed a decrease in the converging section and in the throat section. The diverging section showed decrease in recovery of pressure with the decrease in gas flow because of the increased liquid loading to the scrubber. The iodine absorption efficiency showed a value of 92% for high gas velocity which decreased to 68% for the lowest gas flow rate.

Analyzing Droplet Size Distributions Inside a Self-Priming Venturi Scrubber for Filtered Containment Venting Systems

2018 ◽  
Author(s):  
P. Papadopoulos ◽  
T. Lind ◽  
H.-M. Prasser
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Nuclear Power ◽  
Power Plants ◽  
Gas Flow ◽  
Tube Bundle ◽  
Droplet Size Distribution ◽  
Severe Accident ◽  
Design Element ◽  
Venturi Scrubber

After the accident in the Fukushima Daiichi nuclear power plant, the interest of adding Filtered Containment Venting Systems (FCVS) on existing nuclear power plants to prevent radioactive releases to the environment during a severe accident has increased. Wet scrubbers are one possible design element which can be part of an FCVS system. The efficiency of this scrubber type is thereby depending, among others, on the thermal-hydraulic characteristics inside the scrubber. The flow structure is mainly established by the design of the gas inlet nozzle. The venturi geometry is one of the nozzle types that can be found in nowadays FCVS. It acts in two different steps on the removal process of the contaminants in the gas stream. Downstream the suction opening in the throat of the venturi, droplets are formed by atomization of the liquid film. The droplets are contributing to the capture of aerosols and volatile gases from the mixture coming from the containment. Studies state that the majority of the contaminants is scrubbed within this misty flow regime. At the top of the venturi, the gas stream is injected into the pool. The pressure drop at the nozzle exit leads to the formation of smaller bubbles, thus increasing the interfacial area concentration in the pool. In this work, the flow inside a full-scale venturi scrubber has been optically analyzed using shadowgraphy with a high-speed camera. The venturi nozzle was installed in the TRISTAN facility at PSI which was originally designed to investigate the flow dynamics of a tube rupture inside a full-length scale steam generator tube bundle. The data analysis was focused on evaluating the droplet size distribution and the Sauter mean diameter under different gas flow rates and operation modes. The scrubber was operated in two different ways, submerged and unsubmerged. The aim was to include the effect on the droplet sizes of using the nozzle in a submerged operation mode.

Investigation of Back Pressure Effects on Transient Gas Flow Through Porous Media via Laboratory Experiments and Numerical Simulation

2014 ◽  
Author(s):  
Xiaolei Liu ◽  
Akkharachai Limpasurat ◽  
Gioia Falcone ◽  
Catalin Teodoriu
Keyword(s):  
Steady State ◽  
Gas Flow ◽  
Laboratory Experiments ◽  
Transient Flow ◽  
Pressure Profile ◽  
Back Pressure ◽  
Pressure Effects ◽  
Gas Wells ◽  
Liquid Loading ◽  
Final Steady State

When developing a transient numerical reservoir simulator, it is important to consider the back pressure effects that waves propagating from one end of the porous medium will have on the temporal distribution of pore fluid pressure within the medium itself. Such waves can be triggered by changing boundary conditions at the interface between reservoir and wellbore. An example is given by the transient reservoir response following pressure fluctuations at the wellbore boundary for gas wells suffering from liquid loading. Laboratory experiments were performed using a modified Hassler cell to mimic the effect of varying downhole pressure on gas flow in the near-wellbore region of a reservoir. Gauges were attached along a sandstone core to monitor the pressure profile. The results of the experiments are shown in this paper. A numerical code for modelling transient flow in the near-wellbore region was run to mimic the experiments. The comparisons of simulations and laboratory test results are presented here, for the initial and final steady-state flowing conditions, and where the inlet pressure was maintained constant while initiating a transient pressure build up at the core outlet. The concept of the U-shaped pressure profile along the near-wellbore region of a reservoir under transient flow conditions, originally proposed by Zhang et al. [1], was experimentally and numerically reproduced for single-phase gas flow. This is due to a combination of inertia and compressibility effects, leading to the reservoir response not being instantaneous. The results suggest that, in two phase gas-liquid conditions, liquid re-injection could occur during liquid loading in gas wells. From the experimental results, the U-shaped curves were more obvious and of longer duration in the case of greater outlet pressure. The transition from the initial to the final steady state condition occurred rapidly in all the cases shown here, with the U-shaped pressure profile appearing only over a relatively short time (at the small scale and low pressures tested in this study).

Measurements of Two-Phase Pressure Drop in a Simulated Debris Bed

2017 ◽  
Author(s):  
Milka Hebi Nava Rivera ◽  
Daisuke Ito ◽  
Yasushi Saito ◽  
Mitsuhiro Aoyagi ◽  
Kenji Kamiyama ◽  
...  
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Severe Accident ◽  
Phase Flow ◽  
Two Phase ◽  
Experimental Database ◽  
Flow Through ◽  
Measured Pressure

Two-phase flow through porous media should be well understood to develop a severe accident analysis code not only for light water reactor but also sodium cooled fast reactor (SFR). When a core disruptive accident occurs in SFR, the fuel inside the core may become melted and interacts with the coolant. As a result, gas-liquid two-phase flow will be formed in the debris bed, which may have porous nature depending on the cooling process. Thus, as first step, present work focuses on the characteristics of pressure drop in single- and two-phase flows in different porous media conditions (porous size, liquid and gas flow velocity). In addition, in order to construct an experimental database, the measured pressure drop under different conditions was compared with existing correlations.

Unstable Well Behaviour in Gas Well Liquid Loading

2017 ◽  
Author(s):  
S. P. C. Belfroid ◽  
A. van Wijhe
Keyword(s):  
Pressure Drop ◽  
Mass Flow ◽  
Gas Flow ◽  
Gas Production ◽  
Liquid Loading ◽  
Lower Velocity ◽  
Reservoir Characteristics ◽  
Stability Point ◽  
Production Wells ◽  
The Stability

Liquid loading is the mechanism that is associated with increased liquid hold-up and liquid back flow at lower gas flow rates in gas production wells. In laboratory, most liquid loading experiments are performed at fixed gas and liquid rates (mass flow controlled). In the field, the well behavior is a coupled well-reservoir system in which the reservoir results in a pressure or mass flow controlled inflow, depending on the reservoir characteristics. In this paper results are presented which have been performed with a pressure controlled vessel attached to a vertical pipe. The pressure drop between the vessel was varied to represent reservoir characteristics from tight to prolific. The goal of the experiments was to evaluate the relation and the time ‘trajectory’ between the minimum in the pressure drop curve and the actual flooding point. From these experiments it was concluded that the stability is determined by the overall pressure drop curve. That is the pressure drop from vessel to separator and not the tubing pressure drop curve. This stability point can be at a higher or lower velocity than the actual loading/flooding point and therefore, loading is not the cause of the production decrease. That also means stable production is possible below the flooding point in slugging conditions. In future, the distinction between stable flow and loading/flooding must be made more strict.

Effect of Surfactant (Foamer) Delivery Location on Horizontal Wells Deliquification

2017 ◽  
Author(s):  
Carolina V. Barreto ◽  
Hamidreza Karami ◽  
Eduardo Pereyra ◽  
Cem Sarica
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Rate ◽  
Gas Flow ◽  
Vertical Section ◽  
Horizontal Wells ◽  
Static Mixer ◽  
Liquid Holdup ◽  
Liquid Loading ◽  
Delivery Location

One of the methods to unload liquid from gas wells is foam-assisted lift. The applied surfactant reduces the liquid surface tension facilitating foam stability, and consequently, reducing mixture density and gas slippage. In this experimental study, a 2-in ID facility consisting of a 64-ft lateral section followed by a 41-ft vertical section is used to determine the optimum surfactant delivery location in horizontal wells. Water and compressed air are the liquid and gas phases, and an anionic surfactant is applied continuously with fixed concentration. Lateral section inclination is varied between ±1°, and four injection points are tested, including one with a static mixer, used as an external source of agitation. Recorded parameters are flow pattern, pressure gradient, liquid holdup, and foam quality. In the lateral section, the highest efficiency is obtained by using a static mixer causing significant drop in liquid holdup and increase in pressure drop due to frictional losses. All other injection points show similar behavior to the air-water case, due to negligible generated foam amid the existing flow pattern agitation. In the vertical section, all injection points show similar and significant drops in liquid holdup and delays in liquid loading onset compared to air-water case, and foam quality decreases as gas flow rate is reduced. Increasing the liquid flow rate causes increases in liquid holdup and pressure drop and shifts liquid loading onset to higher gas flow rates. The experimentally observed liquid loading onset is compared to the predictions of Turner et al. (1969), and a modification is proposed in this correlation to consider the effects of surfactant injection. The number of experimental studies investigating foam effects on liquid loading is limited especially for off-vertical configurations. The results of this study provide an experimental source to optimize foam lift in deviated wells.

scholarly journals Numerical Simulation of Flow Behavior within a Venturi Scrubber

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
M. M. Toledo-Melchor ◽  
C. del C. Gutiérrez-Torres ◽  
J. A. Jiménez-Bernal ◽  
J. G. Barbosa-Saldaña ◽  
S. A. Martínez-Delgadillo ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Venturi Scrubber

The present work details the three-dimensional numerical simulation of single-phase and two-phase flow (air-water) in a venturi scrubber with an inlet and throat diameters of 250 and 122.5 mm, respectively. The dimensions and operating parameters correspond to industrial applications. The mass flow rate conditions were 0.483 kg/s, 0.736 kg/s, 0.861 kg/s, and 0.987 kg/s for the gas only simulation; the mass flow rate for the liquid was 0.013 kg/s and 0.038 kg/s. The gas flow was simulated in five geometries with different converging and diverging angles while the two-phase flow was only simulated for one geometry. The results obtained were validated with experimental data obtained by other researchers. The results show that the pressure drop depends significantly on the gas flow rate and that water flow rate does not have significant effects neither on the pressure drop nor on the fluid maximum velocity within the scrubber.

scholarly journals Thermochemical Heat Storage in a Lab-Scale Indirectly Operated CaO/Ca(OH)2 Reactor—Numerical Modeling and Model Validation through Inverse Parameter Estimation

2021 ◽  
Vol 11 (2) ◽  
pp. 682
Author(s):  
Gabriele Seitz ◽  
Farid Mohammadi ◽  
Holger Class
Keyword(s):  
Numerical Model ◽  
Gas Flow ◽  
Reaction Rate ◽  
Heat Storage ◽  
Bulk Material ◽  
Fixed Bed ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Thermochemical Heat Storage ◽  
Speed Up

Calcium oxide/Calcium hydroxide can be utilized as a reaction system for thermochemical heat storage. It features a high storage capacity, is cheap, and does not involve major environmental concerns. Operationally, different fixed-bed reactor concepts can be distinguished; direct reactor are characterized by gas flow through the reactive bulk material, while in indirect reactors, the heat-carrying gas flow is separated from the bulk material. This study puts a focus on the indirectly operated fixed-bed reactor setup. The fluxes of the reaction fluid and the heat-carrying flow are decoupled in order to overcome limitations due to heat conduction in the reactive bulk material. The fixed bed represents a porous medium where Darcy-type flow conditions can be assumed. Here, a numerical model for such a reactor concept is presented, which has been implemented in the software DuMux. An attempt to calibrate and validate it with experimental results from the literature is discussed in detail. This allows for the identification of a deficient insulation of the experimental setup. Accordingly, heat-loss mechanisms are included in the model. However, it can be shown that heat losses alone are not sufficient to explain the experimental results. It is evident that another effect plays a role here. Using Bayesian inference, this effect is identified as the reaction rate decreasing with progressing conversion of reactive material. The calibrated model reveals that more heat is lost over the reactor surface than transported in the heat transfer channel, which causes a considerable speed-up of the discharge reaction. An observed deceleration of the reaction rate at progressed conversion is attributed to the presence of agglomerates of the bulk material in the fixed bed. This retardation is represented phenomenologically by mofifying the reaction kinetics. After the calibration, the model is validated with a second set of experimental results. To speed up the calculations for the calibration, the numerical model is replaced by a surrogate model based on Polynomial Chaos Expansion and Principal Component Analysis.

Two-Phase Flows in Mini-/Micro-Gas Flow Channels of PEM Fuel Cells

2013 ◽  
Author(s):  
Sung Chan Cho ◽  
Yun Wang
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Fluid Model ◽  
Pem Fuel Cells ◽  
Two Phase ◽  
Micro Gas Flow ◽  
Two Fluid Model ◽  
The Impact ◽  
Two Fluid ◽  
Phase Pressure

In this paper, two-phase flow dynamics in a micro channel with various wall conditions are both experimentally and theoretically investigated. Annulus, wavy and slug flow patterns are observed and location of liquid phase on different wall condition is visualized. The impact of flow structure on two-phase pressure drop is explained. Two-phase pressure drop is compared to a two-fluid model with relative permeability correlation. Optimization of correlation is conducted for each experimental case and theoretical solution for the flows in a circular channel is developed for annulus flow pattern showing a good match with experimental data in homogeneous channel case.

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