Cylindrical Storage Tanks Research Articles

Stability of Open‐Top Cylindrical Steel Tanks with Primary Stiffening Ring under Wind Loading

AbstractCylindrical steel tanks are very thin shell structures and vulnerable to buckling under external pressure due to wind or partial vacuum due to rapid emptying or blocked vents when they are either empty or partially emptied. A primary stiffening ring is commonly used at or near the top of the tank wall to increase its strength against external pressure instability. Most traditional design treatments largely ignore the non‐uniform circumferential variation of the wind and treat the tank as subject only to uniform external pressure when sizing the primary stiffening ring. Moreover, the interior of the tank also experiences suction pressures due to the leeward suction on the tank. Wind tunnel tests have shown that the magnitude of these suctions can be very significant compared with the external wind pressures. This study has investigated the buckling resistance of a range of cylindrical steel storage tanks with primary stiffening rings subjected to non‐uniform wind loading modeled as harmonic variations, including the suction, using finite element analyses. A criterion for the required primary stiffening ring stiffness is developed, which is found to depend on its value relative to the stiffness of the cylindrical shell under each harmonic of wind loading. The effects of the shell‐ring stiffness ratio on the buckling capacity are studied and it is found to be a powerful measure that is critical to the design of the ring. Improved design rules are directly obtainable from this new treatment.

Experimental and numerical evaluation of a new design of a solar thermosyphon water heating system with phase change material

In this study, an experimental and numerical performance analysis of a new solar water heating thermosyphon design is proposed. The heat losses during the night (off-sunshine hours) are studied by investigating the efficacy of including the phase change materials in the cylindrical storage tank to enhance the utilized fraction of solar energy. The thermal performance of the heating system with a cylindrical thermosiphon tank with phase change materials is experimentally and numerically investigated. The experimental setup consisted of a flat plate solar collector of an area of ​​2 m2 and a storage tank of a volume of 280 liters. The numerical model of the system is simulated by TRNSYS and FLUENT Software and it is validated by experimental and published data. It was found that with the new design, the water temperature inside the tank remains approximately constant at around 35 °C and 25 °C overnight on a summer and winter day, respectively. In the new design, the water temperature was maintained at a value almost double that of the classic one with a maximum value of 67 °C and 55 °C in July and January, respectively. The payback period of the new system estimated by the economic study was 7.39 years with a net present value of $4265 over its lifetime. The energy savings in different zones in Tunisia was found to be in the range of 60–75%, depending on the intensity of the solar radiation.

Operation strategy of multiple stage independent phase change material modules integrated with thermal storage

This paper presents a study on a new technique for the packed bed Thermal Energy Storage (TES) system that consists of having multiple stages of Phase Change Materials (PCMs) modules placed independently. The TES model is integrated with the domestic water heating application and consists of a cylindrical storage tank with spherical PCMs inside the tank. Water is used to transfer heat from the hot water to the PCMs during daytime. The system operates according to a well-defined control strategy that ensures an appropriate distribution of the heat transfer fluid toward the various modules. A parametric study is conducted to evaluate the thermal behavior of the PCMs and the storage performance of the system for complete charge and discharge modes. The paper evaluates the multiple stage independent PCM modules advantageous side compared to the conventional TES system and indicates that the usage temperature and useful energy are significantly enhanced through the use of the proposed technique. In addition to that, the charging and discharging processes analysis are conducted in order to examine the thermal behavior of the independent PCM modules with the variation of different operation parameters.

Numerical simulation of the effect of uplift on seismic behavior of uncontrolled surface steel tanks with Abaqus software

Cylindrical liquid storage tanks are widely used in various industries such as water storage, fuel and chemicals. Failure of fuel tanks, especially in refineries, can lead to terrible and uncontrollable fires, as well as destructive environmental effects. Ground cylindrical steel fluid storage tanks are widely used in different industries. Regarding the significance of these structures, ensuring the proper performance of such structures in earthquakes needs evaluating their seismic performance. The present study examines the seismic behavior of an unanchored fluid storage system via ABAQUS after validation using an experimental model. Next, the uplift of the bottom sheet is studied using the accelerogram records of the 1940 El Centro and 1994 Northridge earthquakes. The overturning moment time history of the fluid storage system and the maximum overturning moments were obtained to identify their behavior. The results indicated that not bracing storage tanks leads to the uplift phenomenon. Finally, the maximum axial stress of the storage tank shell was compared with the values recommended in the construction codes to control the buckling.

자연순환 태양열온수기 유동 및 열성능에 관한 이론해석

This study presents a theoretical analysis of the dynamic behavior and thermal performance of a solar water heater with an internal exchanger using a thermosiphon system. The heat exchanger, made of a helical coil, is placed in the horizontally cylindrical storage tank so that the solar hot fluid crosses a significant mass of stored water. In order to analyze the dynamic natural circulation of solar water heaters by thermosiphon, a new TRNSYS component was developed using W-language, based on a detailed mathematical model. As a result of simulation, the solar heat yield and the average solar fraction were 2,001 kWh and 75.1%, respectively. The lowest solar fraction in January was 50.5%, and then gradually increased, reaching almost 100% from May to September. Here, when the system overheating lower limit temperature is set to 90℃, it was exposed to the overheating period for about 153 hours, which is 6.5% of the annual operating time (about 2,339 hours). Secondly, the instantaneous maximum efficiency of the collector was 42.3%, and the annual average system efficiency considering the heat loss of the solar storage tank was 36.2%.

Developing a Cold Accumulator with a Capsule Bed Containing Water as a Phase-Change Material

The paper presents the investigation of a prototype cold accumulator using water–ice latent heat for the cold storage process. The concept of the cold accumulator was based on a 200-L-capacity cylindrical storage tank in which spherical capsules filled with water were placed. Beds of polypropylene capsules with diameters of 80 mm, 70 mm, and 60 mm were used in the tests. The cold accumulator operated with a water–air heat pump. Based on the test results, the following parameters were calculated: the cooling capacity, cooling power, energy efficiency of the cold storage, and energy efficiency ratio (EER) of the accumulator. The obtained measurement results were described with mathematical relationships (allowing for measurement error) using criterial numbers and the developed “Research Stand Factor Number” (RSFN) index. It has been found that, for the prototype cold accumulator under investigation, the maximum values of the cooling capacity (17 kWh or 85.3 kWh per cubic meter of the accumulator), energy efficiency (0.99), and EER (4.8) occur for an RSFN of 144·10−4. The optimal conditions for the operation of the prototype cold accumulator were the closest to laboratory tests conducted for a bed with capsules with a diameter of 70 mm and a mass flow of the water–glycol mixture flowing between the accumulator and the heat pump of 0.084 kg/s. During the tests, no significant problems with the operation of the prototype cold accumulator were found.

Dynamic response of cylindrical water storage tanks made byECC compared to normal concrete

In this paper, the dynamic behaviour and seismic damages of concrete cylindrical water storage tanks are investigated. Furthermore, by modeling the reservoirs, using normal concrete and engineered cementitious composite (ECC), the effects of ECC on reducing the seismic damages of reservoirs are investigated. For this purpose, ANSYS software is used to perform the nonlinear dynamic analysis of the tanks and different parameters including the hoop force and bending moment of the wall and cracking or crushing of the concrete were examined. According to the results, the relationships and criteria provided in the ACI standard for design of tanks are recommended to be revised in certain parts. Unlike the normal concrete tanks, in those made of ECC, concrete fracture is not observed and the crack width remains very small at a level that is not problematic. Finally, the use of ECC in cylindrical water storage tanks is suggested as a strategy for reducing the seismic vulnerability of this type of hydraulic structures.

Dynamic response of polyurea coated thin steel storage tank to long duration blast loadings

Cylindrical steel storage tanks are often under the threat of long duration blast loadings induced by the explosion of flammable vapor clouds, and therefore the blast response and mitigation method of the tanks are of great importance to related industries. In the meantime, polyurea coating material, which has been proved to be effective in the blast mitigation of different structures, is employed in this study for the protection of steel storage tanks. Gas blast experiments, as well as numerical and theoretical models, are utilized to investigate the response and energy absorption mechanism of steel tanks and analyze the effect of polyurea coatings. The numerical results showed that the bending of the plastic hinge lines and the tension of the connect zone of the cylindrical shell are the main energy absorption ways of the tank. The modified beam-on-foundation model is then established and verified and the model indicates that the polyurea coatings mainly influence the displacements of the tanks by increasing the area density and bending moments of the tanks. Quantitative analysis on the effect of polyurea is conducted utilizing the response spectrum of the tank’s equivalent system and the range of displacement reducing ratio caused by polyurea and the appropriate spraying strategy of polyurea are acquired accordingly. At last, further numerical simulations are performed and give results that validate the theoretical predictions.

Effect of Diffuser Height on Thermocline in Stratified Chilled Water Storage Tank

Chilled water energy storage using thermal stratification technique currently used in the vast area because it contributes to reducing energy consumption and refrigeration capacity as well as its maintenance, operating and capital costs are low. In this paper, experimental tests were carried out on a small-scale vertical cylindrical storage tank equipped with an elbow-type conventional diffuser at inlet heights of 20, 170, 320 and 470mm for flow charging rates from 1.5-7.5l/min. in order to obtain a good thermal separation. The degree of stratification was estimated by means of temperature distributions and performance metrics, which involve thermocline thickness, the half-cycle figure of merit and equivalent lost tank height. The results show that the decrease in diffuser height above the tank floor tends to the steep thermocline or satisfactory thermal separation, the stratification and thermal performance were obtained at diffuser height of 20 mm within the limiting volume flow rates 1.5-4.5 l/min. better than those at volume flow rates ranging from 5.5-7.5l/min. and much better than at diffuser heights of 170, 320 and 470mm for various flow rates.

Evaporation Reduction Test of Premium Unleaded Fuel by the Smart Floating Roof Method in a Horizontal Cylindrical Tank

The floating roof is originally the device that is easily used in a vertical cylindrical storage tank for volatile products. It covers the evaporative surface which remains constantly circular, regardless of the level of the fluid in the tank. However, in a horizontal cylindrical tank, the extent and shape of the free surface of the fluid, the seat of evaporation, varies according to the residual stock. To this end, the concept of the intelligent or flexible floating roof arises from the problem of pollution and energy losses resulting from the excessive evaporation of unleaded premium fuel (SPb) in the Ivory Coast, in the city of Korhogo, which has a hot and dry climate. Therefore, the objective of this study was to design a floating roof suitable for horizontal cylindrical tanks with a fairly competitive evaporation reduction performance. This study was carried out on an experimental station where two identical tanks were tested in comparative trials. One with a floating polypropylene ball roof and the other without a roof. The respective residual volumes of the fluid in each tank were monitored regularly and concomitantly according to evaporation factors such as temperature and pressure. At the end of these tests, it was found that the flexible floating roof absorbed more losses, with an estimated non-evaporation rate of 88% compared to the tank without the flexible floating roof, whose rate was estimated at 80%, i.e. an added value of 08%. Thus, the layers of beads placed at the gas-liquid interface reduced the heat, mass and pressure transfer between the two fuel phases.

Efflux Time for Two Exit Pipe System

Based on integral balances, mathematical equation for efflux time during gravity draining of a Newtonian liquid (below its bubble point) from a large open cylindrical storage tank (Where the flow in the storage tank is essentially laminar) through two exit pipes of same diameter located at the bottom of the vessel (The flow is assumed to be turbulent in each of the exit pipes) is developed. The equation is ultimately simplified and written in dimensionless form. The equation will be of use for arriving at the minimum time required for draining the contents of a cylindrical storage vessel through two exit pipe. The equation is verified with the experi- mental data. A maximum deviation of 19% and an average deviation of 16% are observed. The effect of initial height of liquid on Reynolds' number is also established. It is shown that while draining a liquid from the cylindrical storage tank through exit pipe system, Froude number re- mains constant.

Performance study of a novel funnel shaped shell and tube latent heat thermal energy storage system

The latent heat thermal energy storage system (LHTES) utilizes phase change material (PCM) to store energy. The non-uniformity in heat transfer between heat transfer fluid (HTF) and PCM along the height of the widely used vertical cylindrical shell and tube type storage tank causes a reduced thermal performance of the storage. Hence, in the present work, a passive heat transfer enhancement technique is proposed through a novel funnel shaped configuration of the shell and tube LHTES to achieve more uniform temperature distribution in the PCM as compared to the cylindrical shell and tube LHTES. Additionally, longitudinal fins are introduced in the HTF tube further to enhance the heat transfer between HTF and PCM. A numerical model is developed using the enthalpy-porosity technique to analyze the phase change phenomenon. The thermal performance of the funnel LHTES is evaluated using the first and second law of thermodynamics. The funnel LHTES with the lateral shell surface tilting up to a height of 250 mm shows higher melt fraction and energy efficiency by 11.5% and 66.6%, respectively compared to the cylindrical LHTES. The latent heat content of the funnel LHTES with a shell tilt height of 250 mm during the charging and discharging period is improved by 1.72 and 1.11 times, respectively than that of the cylindrical LHTES. A significant improvement in the rate of solidification of PCM during the discharging process is obtained with the funnel LHTES.

State transients in storage systems for energy fluids

As the world adopts cleaner and/or renewable energy sources, energy fluids (e.g. hydrogen, ammonia, liquefied natural gas, liquid air, etc.), their transport, and their storage are becoming increasingly important. Feed/product flows, flashing recirculation flows, evaporation, condensation, heat leak, and boil-off gas removal lead to state transients in their storage systems with significant mechanical, safety, environmental, and efficiency implications. This study presents a comprehensive simulation model based on a novel stretchable and spatially moving grid for predicting spatiotemporal transients in a cylindrical storage tank. The model is fully validated under limiting scenarios and then applied to several industrial storage terminals involving liquid hydrogen, liquid air, and liquefied natural gas. In addition to its novel grid formulation, the model offers significant advances over simpler lumped-parameter and complex fluid dynamics models in the literature and commercial process simulators. It gives useful practical insights into boil-off gas removal, pressure management, evaporation/condensation, and compressor sizing/operation.

Fitness-for-service of open-top storage tanks subjected to differential settlement

A method for evaluating the mechanical integrity of open-top cylindrical storage tanks subjected to a differential settlement is given. The settlement profile underneath the bottom circumference of the tank shell can be transformed into different harmonic components using the Fourier transformation. The existing method in American Petroleum Institute’s standard API 653, which is currently used by the industry in North America, does not differentiate the effect of different harmonic components. Nevertheless, the proposed method evaluates a cumulative damage factor by considering the effects of first five harmonic components individually. The paper further discusses other limitations of the existing method in API 653 document. Numerous finite element analysis (FEA) simulations are conducted to formulate and validate the proposed method by employing geometric nonlinear algorithm with nonlinear plastic material properties (GMNA) in ABAQUS finite element software. The trend for limiting settlement values with respect to different harmonic components under consideration and different tank geometries are discussed. The proposed method is validated by performing FEA using four actual settlement data profiles on different tank geometries. Lastly, the comparison is drawn between the FEA results, the existing API 653 method and the proposed method. The results of the allowable settlement indicate that the existing method is not consistent with the FEA findings. For some of the actual settlement data, the existing method results in overly conservative values and for others it gives non-conservative values. Thus, the existing method may not capture the true behavior of tanks under settlement and needs modifications. The results of allowable settlement from the proposed method are found to be consistent with the FEA results for all different settlement data and tank geometries. Therefore, it is recommended that the new method is used instead of the existing method.

Optimizing deep learning model selection for angular feature extraction in satellite imagery

Deep learning techniques have been leveraged in numerous applications and across different data modalities over the past few decades, more recently in the domain of remotely sensed imagery. Given the complexity and depth of convolutional neural network (CNN) architectures, it is difficult to fully evaluate performance, optimize the hyperparameters, and provide robust solutions to a specific machine learning problem that can be applied to nontraditional real-world feature extraction and automation tasks. Ursa Space Systems Inc. develops machine learning approaches to build custom solutions and extract answers from synthetic aperture radar satellite data fused with other remote sensing data sets. One application is identifying the orientation of nontexture linear features in imagery, such as an inlet pipe on top of a cylindrical oil storage tank. We propose a two-phase approach for determining this orientation: first an optimized CNN is used in a nontraditional way to probabilistically determine a coarse location and orientation of the inlet pipe, followed by a maximum likelihood voting scheme to automatically extract the orientation of the angular feature within 7.5 deg. We use a known hyperparameter optimization technique to determine the best deep learning CNN architecture for our specific problem and under user-defined optimization and accuracy constraints, by optimizing model hyperparameters (number of layers, size of the input image, and data set preprocessing) using a manual and grid search approach. The use of this systematic approach for hyperparameter optimization yields increased accuracy for our angular feature extraction and orientation finding algorithm from 86% to 94%. Additionally, this proposed algorithm shows how machine learning can be used to improve real-world remote sensing workflows.

Failure of cylindrical steel storage tank due to foundation settlements

A vertical-axis cylindrical steel tank for storing liquid NaOH failed as a result of large settlements of the sand and gravel foundation under its bottom. The tank had a ring-shaped reinforced concrete foundation under its shell, from which a large portion of rainwater would flow to under the tank bottom plates causing the settlement of the sand and gravel foundation. A local hollow, in which rainwater would periodically collect, appeared under the plates of the bottom. This was conducive to intensive corrosion of the plates in the region of the hollow. After 40 years of service a large local dent appeared in the tank’s bottom. Then as a result of intensive corrosion this part of the bottom was perforated and the liquid leaked out of the tank. After it was drained the tank underwent repairs as part of which a new foundation in the form of a reinforced concrete slab was made and the whole steel bottom was replaced. The settlements of sand and gravel foundations under the bottoms of cylindrical tanks for storing liquids are difficult to measure during the continuous operation of the tanks. Numerical analyses of the settlements of the subsoil and the vertical displacements of the bottom’s plates have shown the settlements to have a significant effect on the radial deformations of the tank’s shell in the zone of its contact with the bottom. It is proposed to periodically measure the radial displacements of the lower parts of liquid storage tanks’ shells to gain information about the potential failure hazard to the tanks due to the settlement of their foundations. Such measurements should be introduced as an obligatory element of monitoring the state of safety of each vertical-axis cylindrical steel tank over its whole service life.

Transient Natural Convection in a Thermally Insulated Annular Cylinder Exposed to a High Temperature from the Inner Radius

Extensive numerical analysis was performed for the unsteady state, natural convection in the annular cylinders. The cylinder’s boundaries were thermally insulated, except the inner surface. The fluid (water) in the cylinder initially was assumed at a cold temperature while the inner surface was subjected to a high temperature. The time history for the heat transfer by diffusion and advection was studied. The time needed for fully charging the storage tank and rate of heat transfer was calculated. The predicted results were compared with the pure heat diffusion process and with a steady-state convection system. Therefore, CFD simulations were performed for natural convection in the storage tank. The main objective of this study was to establish correlations for the rate of heat transfer as a function of time and other controlling parameters. The correlation is needed in designing a thermal energy storage system for domestic and industrial heating processes. One of the drawbacks of the conventional thermal storage systems is the slow charging and discharging, where the heat transfer is mainly diffusion dominated. To overcome such a problem, a system was designed based on the natural convective heat transfer mechanism. Therefore, the heat transfer and fluid flow in a cylindrical storage tank were simulated for a range of Rayleigh numbers (104 to 108) and radius ratio. It was found that a convection-operated storage tank reduces the thermal charging process time drastically compared with the thermally diffusion charging process. The rate of reduction in the charging time mainly depends on the rate of heating and geometric parameter of the tank. To the best of the authors’ knowledge, the work is novel.

Dynamic buckling analysis of cylindrical steel water storage tanks subjected to Kobe earthquake loading

AbstractCylindrical steel storage tanks are thin‐walled significant engineering structures. This study investigated the buckling conditions of ground‐supported cylindrical steel liquid storage tanks according to roof shapes and shell thicknesses. The roof shapes selected were open‐top, flat‐closed, conical‐closed and torispherical‐closed‐top tanks, and shell thicknesses were 4, 6 and 8 mm. These tanks may be exposed to several types of failure during earthquakes, such as elephant‐foot buckling, diamond‐shape buckling, overturning and uplift. Great financial loss and environmental damage can also ensue when steel liquid storage tanks are damaged in an earthquake. The seismic analyses were conducted under Kobe earthquake conditions for cylindrical steel tanks with different shell thicknesses and roof types. To investigate dynamic behaviour of the tanks accurately, the hydrodynamic response of each tank was divided into impulsive and convective components. Directional deformation and buckling results are presented for both impulsive and convective masses. As a result, the deformation of the tank is significantly reduced when the top of the tank is in the shape of a torispherical dome. The flat‐closed tank has a maximum directional deformation in both impulsive and convective modes. Results also show that when shell thickness was increased, buckling deformation decreased, but different deformation states were observed on the wall and roof components depending on the type of roof.

Dynamic buckling of cylindrical storage tanks under fluctuating wind loading

Abstract The present paper investigates the wind-induced buckling and vibration of cylindrical storage tanks based on wind tunnel experiments and time-history response analysis. Focus is on the effect of the vibration of tank shells on the buckling behavior. The dynamic buckling loads obtained from the experiments and the time-history response analysis are compared with the results obtained from the static buckling analysis. The effect of the inertia force generated by the vibration on the dynamic buckling behavior is found to be fairly small. Finally, the dynamic buckling loads are evaluated based on the results of the analysis for static wind loading. (100 words).

Numerical analysis of geometrical and process parameters influence on temperature stratification in a large volumetric heat storage tank

This paper presents various numerical analyses of two-dimensional temperature and velocity fields in vertical cylindrical large volumetric heat storage tanks used in municipal heating applications. Numerical simulations were performed in order to investigate the shape impact of the heat storage tank (height-to-diameter ratio), the diffuser distance from the top of the tank, temperature difference between the warm and cold water and the volume flow variation on temperature stratification in the tank. The accuracy and precision of the numerical model was verified by comparing the numerical calculation results with the measurement results from the literature. An empirical model for the calculation of the tank wall (mantle) insulation thickness with maximum constant temperature inside the tank was also developed. The effect of reducing the insulation thickness and changing the seasons on quality of the temperature stratification and thermal losses through the tank insulation were analyzed. The financial analysis justified the possible reduction of the insulation thickness, and more flexible investment in the plant is presented.