Flow Tank Research Articles

Study on liquid sloshing characteristics of a swaying rectangular tank with a rolling baffle

This study addresses the sloshing characteristics of a liquid contained in a tank with a vertical baffle mounted at the bottom of the tank. Liquid sloshing characteristics are studied through an analytical solution procedure based on the linear velocity potential theory. The tank is forced to sway horizontally and periodically, while the baffle is fixed to the tank or rolling around a hinged point. The rectangular tank flow field is divided into a few sub-domains. The potentials are solved by a separate variable method, and the boundary conditions and matching requirements between adjacent sub-domains are used to determine the sole solution. The free surface elevations with no baffle or a low fixed baffle are compared with those in published data, and the correctness and reliability of the present method are verified. Then the baffle is forced to rotate around the bottom-mounted point. It is found that the baffle’s motion, including the magnitude and the phase together, can be adjusted to suppress the free surface elevation, and even the sloshing wave can be almost eliminated.

Laboratory Experiments of Drainage, Imbibition and Infiltration under Artificial Rainfall Characterized by Image Analysis Method and Numerical Simulations

Two laboratory experiments consisting of drainage/imbibition and rainfall were carried out to study flow in variably saturated porous media and to test the ability of a new measurement method. 2D maps of water content are obtained through a non-invasive image analysis method based on photographs. This method requires classical image analysis steps, i.e., normalization, filtering, background subtraction, scaling and calibration. The procedure was applied and validated for a large experimental tank of internal dimensions 180 cm long, 120 cm wide and 4 cm deep that had been homogenously packed with monodisperse quartz sand. The calibration curve relating water content and reflected light intensities was established during the main monitoring phase of each experiment, making this procedure very advantageous. Direct measurements carried out during the water flow experiments correspond to water content, pressure head, temperature, and cumulative outflow. Additionally, a great advantage of the proposed method is that it does not require any tracer or dye to be injected into the flow tank. The accuracy and other benefits of our approach were also assessed using numerical simulations with state-of-the-art computational code that solves Richards’ equation.

The Dynamics of Sea Tide-Induced Fluctuations of Groundwater Level and Freshwater-Saltwater Interface in Coastal Aquifers: Laboratory Experiments and Numerical Modeling

Laboratory experiments were conducted in a vertical, two-dimensional, rectangular flow tank, simulating the response of a phreatic coastal aquifer to a sea tide. Imposed sinusoidal fluctuations of the saltwater level at one side of the flow tank caused three types of fluctuations: (a) hydraulic head throughout the aquifer, (b) saturation degree within the capillary fringe, and (c) salt concentration surrounding the freshwater-saltwater interface (FSI), all recorded by head, saturation, and salinity sensors, respectively. Significant time lags were observed both in the saturation degree within the unsaturated zone and in the salinity within the FSI. All measured values, recorded by the three types of sensors, were simulated and reproduced using a numerical model. The calibrated model was used for mapping the time lags throughout the aquifer. It was found that the time lag of saturation fluctuations within the unsaturated zone increased upward from the groundwater level as the unsaturated hydraulic conductivity decreased. Similarly, the time lag of salinity fluctuations within the FSI increased downward, with distance from the groundwater level. We interpret the low hydraulic conductivity at the capillary zone as the source of attenuation of both saturation and salinity, because both are controlled by the vertical advection of the whole freshwater body. This advection is significantly slower compared to the dynamics of pressure diffusion. The uniqueness of this study is that it provides quantitative data on the attenuation at the capillary zone and its effect on the salinity time lag in coastal aquifer systems.

Biological modification of seawater chemistry by an ecosystem engineer, the California mussel, Mytilus californianus

AbstractMarine habitat‐forming species often play critical roles on rocky shores by ameliorating stressful conditions for associated organisms. Such ecosystem engineers provide structure and shelter, for example, by creating refuges from thermal and desiccation stresses at low tide. Less explored is the potential for habitat formers to alter interstitial seawater chemistry during their submergence. Here, we quantify the capacity for dense assemblages of the California mussel, Mytilus californianus, to change seawater chemistry (dissolved O2, pH, and total alkalinity) within the interiors of mussel beds at high tide via respiration and calcification. We established a living mussel bed within a laboratory flow tank and measured vertical pH and oxygen gradients within and above the mussel bed over a range of water velocities. We documented decreases of up to 0.1 pH and 25 μmol O2 kg−1 internal to the bed, along with declines of 100 μmol kg−1 in alkalinity, when external flows were < 0.05 m s−1. Although California mussels often live in habitats subjected to much faster velocities, sizeable populations also inhabit bays and estuaries where such moderate flow speeds can occur > 95% of the time. Reductions in pH and O2 inside mussel beds may negatively impact resident organisms and exacerbate parallel human‐induced perturbations to ocean chemistry while potentially selecting for improved tolerance to altered chemistry conditions.

A new high-precision timely monitoring and metering system for early kick and loss

Kick and loss are two complicated incidents that affect the construction safety in oil and gas well drilling. The commonly-used kick/loss monitoring methods are disadvantageous with monitoring lag and low metering precision, which may cause well collapse, pipe sticking and well blowouts due to untimely detection and improper treatment. In this paper, a new type of kick/loss monitoring and metering system was designed based upon a comparative analysis of several kick/loss monitoring methods commonly used on rig sites. This new system has the functions of early monitoring and alarm, kick/loss velocity metering, total loss metering and automatic filling, and its feasibility was verified through laboratory experiments. And the following research results were obtained. First, the monitoring tank of this new system is divided into two chambers, i.e., a main chamber and a secondary chamber. The return of drilling fluid partially flows back to the shale shaker through the main chamber, and the rest overflows into the secondary chamber. Second, the internal cross section area of the secondary chamber is small, which increases the response sensitivity to liquid level change, so kick/loss can be detected in time. Third, the water head of the outlet pipeline of the main chamber remains constant and the outlet flow is stable, so kick/loss velocity and total kick/loss can be calculated quantitatively based on the change of liquid level in the secondary chamber. And the monitoring error of kick/loss velocity is less than 8%. Fourth, in the process of tripping out, the drilling fluid in the monitoring tank flows into the wellbore under the action of self weight to keep the full liquid level of the wellbore all the time. As a result, lagged filling and partial filling are eliminated. In conclusion, this new kick/loss monitoring system is economical and practical, and giving a full play to the advantages of ground survey and alarm timely and accurately.

Performance analysis and life cycle greenhouse gas emission assessment of an integrated gravitational-flow wastewater treatment system for rural areas

Due to the lack of appropriate wastewater treatment facility in rural areas, the discharging of wastewater without sufficient treatment results in many environmental issues and negative impact on the local economy. In this study, a novel integrated gravitational-flow wastewater treatment system (IGWTS) for treating domestic wastewater in rural areas was developed and evaluated. As the core module of IGWTS, the multi-soil-layering (MSL) system showed good performances for removing organic matters and nutrients in lab-scale experiments. Aeration was found to be the dominant positive factor for contaminant removal in factorial analysis, while bottom submersion had the most negative effect. Based on the critical operational factors obtained from lab-scale tests, the full-scale IGWTS consisting of multifunctional anaerobic tank (MFAT), MSL, and subsurface flow constructed wetland (SFCW) was designed, constructed, and operated successfully in the field application. The final effluent concentrations of COD, BOD5, TP, NH3-N, and TN reached 22.0, 8.0, 0.3, 4.0, and 11.0mg/L, with removal rates of 92, 93, 92, 86, and 76%, respectively. The feasibility of IGWTS was also quantitatively evaluated from the perspectives of resource consumption, economic costs, water environment impact, and life cycle greenhouse gas (GHG) emissions. IGWTS has been proved to be a sound approach to mitigate GHG emissions compared with centralized wastewater treatment plant. It can also be featured as an eco-friendly technology to improve rural water environment, and an economic scenario with low construction and operation costs. Graphical abstract.

A hybrid method for ship response coupled with sloshing in partially filled tanks

An efficient hybrid numerical method was developed to study wave-induced ship response coupled with sloshing-induced compressible fluid response in partially filled tanks of a 138,000 m3 liquefied natural gas carrier at zero speed in regular head and beam waves. A nonlinear boundary element Rankine source code, solving the incompressible incident flow field, accounted for the nonlinear stationary forward speed problem and the weakly nonlinear seakeeping problem. A Reynolds-averaged Navier-Stokes equations solver, computing the compressible sloshing flow in tanks, considered the associated discontinuous numerical domains of coupled simulations. Grid sensitivity studies were performed. Comparative available experimental model test measurements of ship response and free surface sloshing elevations in tanks validated the numerical method. Further investigations regarding the influence of wave steepness and tank fill levels on sloshing were performed. Results demonstrated that liquid sloshing in tanks had a large influence on ship surge and roll responses but hardly effected ship heave motions.

Linear and Non-Linear Stress Analysis for the Prediction of Fracture Toughness for Brittle and Ductile Material using ASTM E399 and ASTM E1290 By ANSYS Program package

Prediction of fracture toughness value of most the metallic materials is a very important issue to be consider in designing of engineering structural components like pipes, flow tanks and pressure vessel where it can be used in the evaluation of critical crack length that is consider very important factor in non-destructive testing because during inspections of these components, the critical crack length is being compared with the minimum allowable flow size. Fracture toughness value can be predicted by using two different types of experimental tests such as ASTM-E399 (which is used to predict fracture toughness under plane strain condition for brittle materials which undergo to small plastic deformation) and ASTM-E1290 (which is used to predict fracture toughness for ductile materials which undergo to large plastic deformation). These experimental tests utilize specimens such as compact tension specimen CT and three-point bend specimen SENB which must be pre-cracked. However, manufacturing of pre-cracked in metallic structural components before testing is expensive and time-consuming process, thus in the current study, fracture toughness will be predicted by using economized method in both time and cost that is the finite elements method by using ANSYS PROGRAM Where, a three-dimensional model has been designed by using two different types of elements (plane-82) and (solid-95).Firstly, two-dimensional model mesh will be idealized by using element type (plane-82) due to ANSYSY PROGRAM can pick–up singularity for two dimensional model only, but in order to obtain more accurate results, a three dimensional model will be designed by utilizing Sweep Model with restriction with ANSYSY abilities in the treatment of fracture mechanics problems for three dimensional model analysis where the element length must be ranging from 1to4 in all directions. In elastic region, the fracture toughness is been predicted directly from ANSAYS PROGRAM using the specification in ASTM-E-399 for compact tension specimen for practical design problems. But in elastic-plastic region, the fracture toughness is been predicted by using the crack tip opening displacement model (CTOD-Model) using the specification in ASTM-E-1290 for three-point bend specimen for practical design problem. The critical value for crack tip opening displacement will be calculated after extracting load-displacement data from ANSAYS PROGRAM then using these data in (CTOD-Model) which is separated into two components, elastic and plastic, the elastic component has been estimated using Dug Dual-Model, while the plastic component will be estimated using Plastic Hinge-Model. However, the fracture toughness value that has been predicted by finite element method from non –linear elastic analyses and from non –linear elastic-plastic analyses gives excellent results which are very close to the experimental results with error ratio ranging between (10% to 14%).

Optimization of the coefficient of performance of a heat pump with an integrated storage tank – A computational fluid dynamics study

The performance of a heating system consisting of a heat pump with an integrated storage tank was evaluated by means of Computational Fluid Dynamics (CFD) calculations. The aim of the investigations was to elucidate how thermal stratification in the tank would influence the COP of the system. Differently designed storage tanks were investigated under typical operation conditions. CFD models of heat storage tanks were developed and validated by experiments on a test tank. Calculations with the validated models were carried out in order to find the optimal tank design and system settings for achieving the highest possible COP. The investigated parameters were volume flow rate, tank geometry, diffuser design and tank wall material. Two different system COPs were defined: one based only on charge operation and the other on both charge and discharge operations. It was found that there is a direct connection between the thermal stratification inside the tank and the COP of the heating system. Higher degree of stratification leads to higher COP. For the ideal case where there is no mixing, no vertical thermal conduction in the tank and no heat loss from the tank, the system COP after a charge-discharge cycle is 3.69. When the effect of mixing is taken into account, the obtained COP of the system is decreased by approximately 9%. If heat transfer to the tank wall and vertical thermal conduction are also taken into account, the obtained system COP is lowered by another 5%. Moreover, the COP of a heating system with high flow rates can be significantly increased by a diffuser plate installed in the tank with a small distance to the inlet/outlet. The best performing system studied consisted of an insulated tall and slim tank with a h/d ratio of 3.64 and a perforated plate diffuser, giving a COP of 3.23 which was 32% higher compared to a case without a diffuser. The performance of the suggested system was not affected by variations of flow rates in the range from 0.12 to 0.24 kg/s.

Extension of a Standard Flow Solver for Simulating Phase Change in Cryogenic Tanks

Cryogenic-liquid-propelled rockets are equipped with tanks containing subcooled liquid propellants such as hydrogen and methane. The pressure evolution in such tanks is governed by the heat exchange of the vapor with the tank walls and liquid surface and the phase change at the liquid vapor interface. Because phase change is a major driver for the pressure evolution, the accurate prediction of the phase change rate is of crucial importance for the design of cryogenic liquid tanks and their pressurization systems. Therefore, in this study the commercial multiphase flow solver FLOW-3D® is extended with a customized phase change model based on the temperature gradients at the phase boundaries. The clear advantage of the temperature gradient model over, for example, kinetics-based models is that it contains no model constants. To validate the customized phase change model, liquid evaporation at a heated wall, liquid evaporation at a superheated liquid body at a wall, the bubble growth problem in superheated liquid, and meniscus evaporation in a heat pipe are considered. The numerical solutions of all computations show a good agreement with reference solutions. Furthermore, the phase change model is applied to the microgravity tank flow problem SOURCE-2, where HFE-7000 evaporates at a superheated wall. With the new phase change model, FLOW-3D is able to predict the pressure evolution with a maximum deviation of 0–20% compared with measurements.

Mortality in Pacus (Piaractusmesopotamicus) caused by Pantoeaagglomerans and Pseudomonas aeruginosa in Excavated Tank

Background:Fish production in Brazil is growing strongly. This growth is being mainly driven by mainland aquaculture, which in 2017 produced 691.700 tons of fish. Toimprove production levels, fish farms have become increasingly intensive, but in these systems, the high fish densities in the ponds, the high feeding rate, and the high organic matter levels in the water can lead the fish becoming stressed. This can cause bacterial proliferationand an increase in mortality. Most species of fish-causing bacteria are saprophytes. They are found naturally in the environment and are usually responsible for secondary or opportunistic infections.Thisstudy reports on an outbreak of Pacus (Piaractusmesopotamicus) mortality at an intensive fish farm, in the municipality of Campo Grande, MS, Brazil,that used excavated tanks.Cases:The outbreak occurred at a fish farm in the municipality of Campo Grande, MS, during August, 2015. A total of 200 pacus in two tanks died after they showedthe following symptoms: lethargy, anorexia, increased mucus production, and disordered swimming and water surface searching. The temperature and dissolved oxygen were measured using a digital thermometer and an oximeter, respectively, and water transparency was measured with a Secchi disc. The pH was measured usinga portable digital potentiometer. The values for the water quality parameters analyzed during the mortality period were temperature, 22.5oC; transparency, 20cm; oxygen dissolved in the early morning 3mg/L and at the end of the afternoon, 4.5mg/L; pH 8.3; and toxic ammonia, 0.002ppm. Five fishes were collected from the tank, immediately cooled to 4°C, and sent to the Microbiology and Pathology Laboratories to perform the microbiological and pathological laboratory procedures.After the replication process, the slow glucose fermentation characteristics in MacConkey Agarand other biochemical tests showed that the lactose non-fermenter bacterium was Pseudomonas aeruginosa and the fermenting bacterium was Pantoeaagglomerans. A necroscopic examination revealed congestion of viscera in general and thickening of the gills; the histopathological examination showed an intense inflammatory reaction in the gills; andthe liver showed congestion and dilation of the central, hepatoportal, and sinusoidal veins,marked cytoplasmic vacuolization, the presence of hemosiderin and leukocytosis, and coagulation necrosis and cholestasis foci.Discussion:The water temperature in the tanks (22.5°C) was lower than what is considered ideal for tropical fish. It ranged from 25 to 32°C. Furthermore,the pH (8.3) was close to the limit of what is considered appropriate. The mean tank flow rate at the time of death was 15 L/min, corresponding to a daily renewal rate of 1.2%, which was lower than the 10% per day recommended as the ideal ratefor excavated ponds in a semi-intensive production system. The decreased water flow in the tank during the period when mortality was recorded caused an increase in the amount of accumulated organic matter. This rise is commonly referred to as eutrophication, which is characterized by an increase in the rate of decomposition and release of nutrients into the water. The excess nutrients, mainly nitrogen and phosphorus, cause excessive phytoplankton and aquatic macrophyte growth, which results in a significant reduction in the amount of dissolved oxygen, particularly during periods of low photosynthetic activity.In this case study, the cause of the fish mortalitywas attributed to opportunistic infection by Pantoeaagglomeransand Pseudomonas aeruginosacaused by imbalances in water quality.

Visualization of graphene oxide transport in two-dimensional homogeneous and heterogeneous porous media.

Graphene oxide (GO) has been indicated to be biotoxic and risky in environment, its environmental behavior thus has received increasing attention in recent. In this study, homogeneous and heterogeneous sand tanks were used to examine the transport behaviors of GO nanoparticles in two-dimensional (2-D) porous media under various conditions. Light transmission visualization (LTV) technology was applied to visualize the real-time transport, retention, and release of GO. GO transport in 2-D porous media was simulated with a simplified Double Monod model. GO mobility decreased with the increasing solution ionic strength (IS) and decreasing media grain size. Preferential flow played an important role in GO transport in 2-D heterogeneous porous media. Even without vertical flow in the sand tanks, GO still spread vertically through dispersion, suggesting the importance of the dispersion process to nanoparticle fate and transport in 2-D porous media. LTV images and breakthrough curves showed that some of the previous retained GO particles were instantaneously remobilized with IS decreasing. With the consideration of the vertical dispersion, simulations of the Double Monod model matched the experimental data well. Findings from this work contribute to expand current knowledge of environmental fate and transport of GO, leading to better assessment and prediction of its environmental risks.

The use of pressure hot water storage tanks to improve the energy flexibility of the steam power unit

Existing thermal power plants must be adapted to cooperate with wind farms and other renewable energy sources by improving their flexibility. The paper analyzes the improvement of the 200MWe block's flexibility by installing hot water storage tanks. The maximum increase in the block output resulting from the shut-off of low-pressure steam bleeds is calculated. During this period, the hot water from water storage tanks is supplied to the boiler. Hot water is accumulated in pressure water tanks during the low-load period of the unit. Water with design temperature in the feed water tank flows into the water pressure tanks to reduce the electric power of the unit in the off-peak night hours. The hot water accumulated during the night in storage tanks is used to feed the boiler during the period of peak demand for electricity. The reduction in the block electric power was calculated for various volumes and charging periods of the water storage tanks. A cost analysis was carried out to demonstrate the economic profitability of installation of pressure water accumulators. It is worth mentioning that hot water tanks may also be applied to fill the boiler evaporator with hot water before the start-up of the power unit from the cold state.

Determination of the ORC-RO system optimum parameters based on 4E analysis; Water–Energy-Environment nexus

This paper presents the concentration disposal index (CDI) concept extension for increasing the Water–Energy-Environmental nexus and reducing the environmental impacts of RO system brine. This non-dimensional index introduces the difference between the density of brine flow and raw water tank in recovery. This concept is utilized in main engine system of the ship. Different configurations of Organic Rankine Cycle (ORC) and working fluids are studied at the outlet of high temperature thermal source (280 °C), based on Energy analysis (1E), Exergy (2E), Economic (3E) and environmental impacts (4E) in order to produce desalinated water (4E+D). The output power from ORC is used as the driver of RO high pressure pump. Based on the waste heat in system, the sources are used for preheating of RO system pump inlet water. These sources are: Lubricating oil, air cooler and jacket cooler and ORC condenser. The key parameters in optimization are: (1) the ORC configuration choice, (2) the working fluid of Rankine cycle based on thermal source, (3) the RO system optimum design, (4) the membrane selection among the DOW company membranes, (5) the pinch and approach temperatures of the Waste Heat Recovery (WHR), (6) the reduction of environmental impacts of RO brines, (7) the selection of Energy Recovery Device (ERD). Determination of these parameters is done according to system optimization by genetic algorithm (GA). In order to consider the CDI function impact, once the system is considered with two objectives based on exergy efficiency of the entire cycle and the unit product cost (UPC) and then is considered by three objectives; the two mentioned ones and the CDI function. The results of these two optimizations indicate that, utilizing CDI reduces the ultimate concentration of the brine and increases the buoyancy force for faster mixture. In three-objective optimization, the ORC configuration is chosen with the recuperator, the R245ca working fluid, the two-stage RO system and the SW30XLE-400i membrane for both of stages.

Generalizing the effects of the baffling structures on the buoyancy-induced turbulence in secondary settling tanks with eleven different geometries using CFD models

Computational fluid dynamics (CFD) models are applied to understand the effects of baffling structures on the buoyancy-induced turbulence flow in secondary settling tanks (SSTs). Eleven SST geometries, including four circular SSTs and seven rectangular SSTs, are evaluated in this study. The main research tool is a Fluent-based two-dimensional SST model. The model is verified with observations from literature. The validated model is then applied to compare the predictions of the effluent suspended solids (ESS) by the buoyancy-decoupled and buoyancy-coupled turbulence models on each SST geometry. Next, the effects of the SST baffling structures on the turbulence properties are compared and quantified. Additionally, stress tests are simulated on the SSTs, to predict their performances using both the buoyancy-decoupled and buoyancy-coupled turbulence models.The results for the original flow conditions show that the effects of the SST baffling structures on the buoyancy-induced turbulence can be divided into three zones: Zones A, where the baffling structures have negligible damping effects, and only the buoyancy-coupled turbulence model provides accurate predictions; Zone B, where the baffling structures partially dissipate the effect of buoyancy on turbulence, and the buoyancy-coupled model continues to provide accurate predictions but the buoyancy-decoupled turbulence model only provides qualitative but similar predictions; and Zone C, where the baffling structures fully dissipate the effect of buoyancy on turbulence, and both models provide similar, accurate predictions. Two indicators, the densimetric Froude number and the differences in turbulent kinetic energy can be used to predict the need for buoyancy coupling.

Testing the adaptive value of gastropod shell morphology to flow: a multidisciplinary approach based on morphometrics, computational fluid dynamics and a flow tank experiment

A major question in stream ecology is how invertebrates cope with flow. In aquatic gastropods, typically, larger and more globular shells with larger apertures are found in lotic (flowing water) versus lentic (stagnant water) habitats. This has been hypothetically linked to a larger foot, and thus attachment area, which has been suggested to be an adaptation against risk of dislodgement by current. Empirical evidence for this is scarce. Furthermore, these previous studies did not discuss the unavoidable increase in drag forces experienced by the snails as a consequence of the increased cross sectional area. Here, using Potamopyrgus antipodarum as a study model, we integrated computational fluid dynamics simulations and a flow tank experiment with living snails to test whether 1) globular shell morphs are an adaptation against dislodgement through lift rather than drag forces, and 2) dislocation velocity is positively linked to foot size, and that the latter can be predicted by shell morphology. The drag forces experienced by the shells were always stronger compared to the lift and lateral forces. Drag and lift forces increased with shell height but not with globularity. Rotating the shells out of the flow direction increased the drag forces, but decreased lift. Our hypothesis that the controversial presence of globular shells in lotic environments could be explained by an adaptation against lift rather than drag forces was rejected. The foot size was only predicted by the size of the shell, not by shell shape or aperture size, showing that the assumed aperture/foot area correlation should be used with caution and cannot be generalized for all aquatic gastropod species. Finally, shell morphology and foot size were not related to the dislodgement speed in our flow tank experiment. We conclude that other traits must play a major role in decreasing dislodgement risk in stream gastropods, e.g., specific behaviours or pedal mucus stickiness. Although we did not find globular shells to be adaptations for reducing dislodgement risk, we cannot rule out that they are still flow-related adaptations. For instance, globular shells are more crush-resistant and therefore perhaps adaptive in terms of diminishing damage caused by tumbling after dislodgement or against lotic crush-type predators.

Measurement of thermal behavior of an ester-filled power transformer at ultra-low temperatures

At arctic ambient temperatures, the viscosity of cooling fluids for power transformers reaches extreme levels. This leads to a change of fluid flow and cooling performance, which is even more critical in case of ester fluids and cooling by means of radiators. To ensure reliable operation even under such conditions, a power transformer has been tested under different loads at ambient temperatures ranging from −50 °C to −30 °C. In this report, we concentrate on the measurement results for two cold start tests: one smooth start at −50 °C and a second, quicker start with full load at −40 °C. The steady state results have been analyzed in an earlier publication. When power is supplied to a completely cold transformer, we observe that flow inside windings and tank develops relatively fast. However, it may take a long time to start natural flow through the radiators. In the meantime, temperatures in the active part may reach undesired levels. In the cold start at −50 °C, the radiators did not become operational at all, even after several days. The losses were too small to overcome the hydraulic resistance in the radiator panels. When the transformer was started with full load at −40 °C, the cooling equipment stayed cold for a long time, but became suddenly active approximately 14 hours after start. At this point, we noticed an abrupt change of temperatures in the radiator. Afterwards, the transformer gradually approached a steady state situation. Although we observed an overshoot of top oil and hot spot temperatures in this heat run, the measured temperatures remained at an acceptable level. This, however, need not be the case in general. Especially in the situation of separate radiator batteries, critical temperatures must be expected.

Microbial Sulfate Reduction and Perchlorate Inhibition in a Novel Mesoscale Tank Experiment

Microbial sulfate reduction occurs ubiquitously in natural environments. In oil and gas reservoirs, the generation of sulfide (also known as souring) can result in the corrosion of steel infrastructure and downgrading of oil quality, among other environmental and health-related concerns. The complex interplay between hydrological, geochemical, and biological processes during souring is poorly understood, preventing effective treatment and mitigation especially in naturally heterogeneous subsurfaces. In this work, three-dimensional flow tank experiments are utilized as a mesoscale experiment that links well-constrained batch and column experiments to field measurements. The mesoscale tank experiment investigating perchlorate treatment of souring is coupled with reactive transport modeling to understand the effects of heterogeneity on souring and effectiveness of perchlorate treatment. Tracer experiments were conducted at the start and end of the experiment to constrain flow pathways and heterogeneities. Is...

Surge Tank Analysis for Water Hammer Remedy for Long Distance Pipeline

Various protection methods can be used for protecting the pipeline system from the impact of water hammer. Which includes the use of special materials for supporting the pipeline and the installation of special devices such as surge tanks, relief valves, and air chambers. In this study, to protect the pipeline system and reduce the effect of water hammer, surge tank has been used. Governing equations of transient flow with and without surge tank is numerically simulated using MATLAB software. Sensitivity analysis was investigated using several variables such as pipe diameter, wave’s velocity and friction factor. Method of characteristics (MOC) was implemented in this study. It was found that the diameter and friction factor of pipe have a significant impact on the results of transient flow and surge tank compared to the effect of wave’s velocity. It has been reached that the capacities of surge tanks at diameter (1m), are (1475m3) at first, second and fourth stages, (1360m3) at third and fifth stages and (570m3) at sixth stage. And at diameter (1.2m), the capacities are (1700m3), (1530m3) and (1475m3) at first, second and third stages respectively. But at diameter (1.4m), the capacities are (1590m3) at first and second stages. For all values of wave’s velocity, the capacities of surge tanks are (1760m3), (1530m3) and (1420m3) at first, second and third stages respectively. But the capacities of surge tanks at friction factor (0.007) are (1810m3), (1585m3) and (1245m3) at first, second and third stages respectively. However, for the capacity of surge tanks at the friction factor (0.008), it was mentioned when the surge tanks capacity of the diameter (1.2m) was mentioned. And when the friction factor is (0.009), the capacities are (1460m3) at first stage, (1415m3) at second and third stages and (570m3) at fourth stage

Influence of biomass and water velocity on light attenuation of Cladophora glomerata L. (Kuetzing) in rivers

The attenuation of photosynthetically active radiation (PAR) through the filamentous alga Cladophora glomerata was investigated both in situ and in an experimental flow tank under natural and artificial lighting using a fiber-optic sensor. Over 35 separate experiments were completed to characterize downward light attenuation and water velocity effects. Measured extinction coefficients ranged from 4.3 to 150.7 m−1 for biomass samples ranging from 40 to 253 mg chlorophyll-a m−2 (41 to 381 g ash free dry weight m−2) at shear velocities from 0 to 51.8 cm s−1. An exponential relationship between light attenuation coefficient (Kalg) and algal biomass thickness (δ) was found (lnKalg = −1.1831 lnδ + 8.3789; r2 = 0.41, p < 0.001). Unexpectedly, chlorophyll-a (Chla) and ash free dry weight (AFDW) areal density were poor predictors of Kalg. No significant correlations (p > 0.01) were found amongst any of the other experimental variables (e.g., shear velocity, Reynolds number, etc.). Cladophora mat thickness (δ) and volumetric biomass (Chla m−3) provided the greatest explanation of downward light attenuation in flowing water, reducing irradiance in proportion to how closely the filaments are pressed together. Observed δ generally decreased with increasing shear velocity, albeit not predictably. Results have important implications on aquatic systems where macroalgae generate variable light regimes on understory aquatic species.