Rectangular Storage Tanks Research Articles

Water mixing in rectangular storage tanks: small-scale versus field tests

ABSTRACT Mixing and renewal processes are crucial for maintaining adequate drinking water quality in storage tanks. This paper studies the influence of baffle structures and of fill-and-draw cycles on water mixing and renewal in rectangular cross-section tanks through laboratory tracer tests carried out in two small-scale tanks (with and without baffles) and compares with results from a full-scale test. This study shows that the use of baffles inhibits water mixing and keeps older water pockets in small recirculation zones, though baffles allow faster water renewal than in open tanks for lower flow rates. High water volume variation in fill-and-draw cycles (between 50% to 80%) promotes water renewal, independently of the tank configuration (i.e. cross-section and the existence of baffles). Despite the existing baffle structure in the full-scale rectangular tank with 20% water volume variation, the high flow rates allowed a rapid renewal of the stored water.

Sensitivity analysis of design parameters for melting process of lauric acid in the vertically and horizontally oriented rectangular thermal storage units

Widespread commercialization of PCM-based latent heat storage systems is limited by the low melting and solidification rates during the phase transition process. In this study, fins are used to enhance the phase change process. A parametric study is conducted to understand the effect of fins on the thermal performance of vertically- and horizontally-oriented rectangular storage tanks. Throughout simulations, the fin volume, and thereby the mass of PCM in the tank, were kept constant. It was observed that the horizontal enclosures can take advantage of the development of strong natural convection flow until near the end of the melting process, whereas with vertical counterparts the strength of the convection currents was diminished during the shrinkage stage. The results suggest that longer and thinner fins are more beneficial for enhancing the melting rate than shorter and thicker fins. It was concluded that for horizontal enclosures with fin lengths of 25 and 35 mm, increasing the number of fins does not necessarily shorten the melting time. The maximum melting time reduction compared to the 3-fin vertical enclosure with a fin length of 25 mm (chosen as our benchmark case) was 75.1% when nine 45-mm-long fins are used in a horizontal enclosure.

Finite Element Analysis and Dynamic Characteristics of Anchored Rectangular Liquid-Storage Tank

In order to obtain the natural frequencies and vibration modes of the rectangular storage tanks under liquid-filled state, open anchorage rectangular storage tank models of 1000 m3 are established and the dynamic characteristics analysis is carried out. Considering the influence of wall thickness(t), liquid storage level(h) and other factors on the natural frequencies and vibration modes of the models under static state, the finite element analysis models of rectangular tanks with different parameters are established, and different natural vibration frequencies are compared and analyzed. The results show that the natural vibration frequencies of the structure increase with the increasing of the thickness of the tank wall and the bottom plate. The liquid storage level is negatively correlated with the tank-liquid coupling vibration frequency. The natural vibration frequencies of the tank decrease with the increasing of the liquid storage level.

Optimization of Baffled Rectangular and Prismatic Storage Tank Against the Sloshing Phenomenon

The fluid motion in partially filled tanks with internal baffles has wide engineering applications. The installation of baffles is expected to reduce the effect of sloshing as well as the consequent environmental damages. In the present study, a series of experimental tests are performed to investigate the sloshing phenomenon in a baffled rectangular storage tank. In addition, the sloshing phenomenon is also modeled by using OpenFoam. Based on the experimental and numerical studies, optimization of the geometric parameters of the tank is performed based on some criteria such as tank area, entropy generation, and the horizontal force exerted on the tank area due to the sloshing phenomenon. The optimization is also carried out based on the entropy generation minimization analysis. It is noted that the optimum baffle height is in the range of hb/hw=0.5–0.75 in the present study (where hb and hw are the baffle height and water depth, respectively). Based on the results, the optimal design of the tank is achieved with RA= 0.9–1.0 (where RA=L/W, L and W are the length and width of the tank, respectively). The results also show that the increase of hb can lead to a decrease of the maximum pressure and horizontal force exerted on the tank. It is also noted that the horizontal force exerted on the tank firstly continues to increase as the sway motion amplitude increases. However, as the normalized motion amplitude parameter, a/L (The parameter a is the motion amplitude), exceeds 0.067, the effect of motion amplitude on the force is not obvious. The same optimization is also performed in the multiple-variable-baffled tank and prismatic storage tank.

Multi-dimensional NURBS model for predicting maximum free surface oscillation in swaying rectangular storage tanks

In this paper, a multi-dimensional non-uniform rational B-spline (NURBS) model is presented aiming at predicting the maximum free surface oscillation (MFSO) in the swaying rectangular storage tanks. The accuracy and clear mathematical meaning of the NURBS formulation make it attractive for the purpose. In this regard, a numerical model is developed to simulate the liquid sloshing phenomenon in a rectangular tank by means of coupling the Reynolds averaged Navier–Stokes (RANS) solver and the volume of fluid (VOF) technique. The RANS equations are discretized and solved using the staggered grid finite difference SMAC method. In order to validate the model, a rectangular tank with specified width and water depth is exposed to a presumed horizontal periodic sway motion and the results of the numerical analysis are compared to a well-established example. In the next step, the numerical model is used to simulate the sloshing phenomenon in the rectangular storage tanks with different widths and water depths under different harmonic excitations. Finally, a multi-dimensional NURBS hyper-surface is employed to fit a multivariate function to the sloshing results based on the numerical data. As a result, a new mathematical relationship is suggested by this article to estimate the MFSO in the swaying rectangular storage tanks, so that practitioners may benefit more when they try to apply the presented methodology to their real-world problems.

Optimization of the rectangular storage tanks for the sloshing phenomena based on the entropy generation minimization

The maneuver-induced liquid cargo motion in the partly-filled tanks called, sloshing poses a serious threat to the stability and controllability of this phenomenon. The entropy generation in the sloshing phenomenon is obtained for the first time in the rectangular storage tank. In this paper, a numerical model is developed to simulate the sloshing phenomenon by using coupled RANS solver and VOF method. The RANS equations are discretized and solved using the staggered grid finite difference and SMAC methods. The entropy generation distribution provides designers with useful information about the causes of the energy losses. As an objective, the total entropy generation is introduced as a design criterion parameter for rectangular storage tanks and is compared with the tank perimeter (TP) criterion. In order to do this, the horizontal periodic sway motions with different amplitudes, angular frequencies, and aspect ratios (AR) are applied to the rectangular storage tanks. The results show that the optimal AR is about 2.9 for TP criterion and is about 3.2 for the entropy generation criterion.

Non linear vibration analysis of liquid storage tank

This study presents an idealization scheme for the analysis of rectangular storage tanks acted upon by earthquake excitations. Above and below ground tank, are considered. A linear three-dimensional finite element analysis is adopted to predict the natural frequencies. The analysis parameters are the ratio of height to length of the tank, the type of soil, level of water in the tank, and also the wall thickness.Tanks made from steel as well as from concrete are investigated. A general purpose finite element program (ANSYS 12.0)used to model the analysed system. The tank base and wall are modelled by plane strain shell elements. The contained liquid is represented by a special solid element. Finally, the soil is modelled by simple spring-damper elements. The soil medium is idealized by the elastic half space model, that is, linear springs are assumed to represent the structure-soil interface. Which is then modelled by two-node spring dashpot elements.Forced vibration analysis is conducted on above ground and buried concrete tank. This analysis is carried out by applying the records of the North-South component of the 1940 El Centro earthquake with peak acceleration of 0.32g. It is found that the bending stresses in above ground concrete tank is (74.167) % greater than the stresses in buried tank with the same dimensions.

Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k – ɛ model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state.

Numerical Analysis of the Base-Isolated Rectangular Storage Tanks under Bi-directional Seismic Excitation

Liquid storage tanks are critical elements in the water supply scheme and firefighting system in many industrial facilities for storage of water, oil, chemicals and liquefied natural gas. A common effective method to reduce the seismic response of liquid storage tanks is using baseisolation systems. In this research, the finite element method is used to investigate the seismic behavior of rectangular liquid tanks in three-dimensional domains. The continuous liquid mass of the tank was modeled as lumped masses referred as convective mass, impulsive and rigid mass. The rectangular water tank in two cases base isolated and conventional non-isolated system was selected as a case study. The sloshing displacement and base shear response in two mentioned cases subjected to various ground motions under horizontal components X and Y directions were considered and the results were compared. For this purpose the nonlinear time history analyses of the model were performed. As a result, base isolation was found to be effective in reducing the base shear values, without significantly affecting the sloshing displacements.

Experimental study of inlet structure on the discharging performance of a solar water storage tank

The utilization of the solar water heating system can reduce the conventional energy consumption of a building. A good inlet of the solar storage tank can enhance the thermal stratification and improve the thermal storage efficiency and discharging efficiency. Experiments were carried out to investigate the discharging performance of a rectangular storage tank with different inlet structures which were slotting-type inlet, direct inlet and shower-type inlet. This study aimed to provide guidance for the optimization of the inlet structure of water tank so that the efficiency of solar water heating system (SWHS) could be improved further. The effective discharging efficiency and effective discharging time were introduced to evaluate the performance of water tank with different inlet structures. The results showed that the slotting-type inlet exhibited the best thermal stratification and improved the discharging performance of the tank more effectively than the other two inlets. Energy saving potential of new inlet was also presented.

Numerical simulation of sloshing in rectangular storage tank using coupled FEM-BEM

Sloshing of liquid can increase the dynamic pressure on the storage sidewalls and bottom in tanker ships and LNG careers. Different geometric shapes were suggested for storage tank to minimize the sloshing pressure on tank perimeter. In this research, a numerical code was developed to model liquid sloshing in a rectangular partially filled tank. Assuming the fluid to be inviscid, Laplace equation and nonlinear free surface boundary conditions are solved using coupled FEM-BEM. The code performance for sloshing modeling is validated against available data. To minimize the sloshing pressure on tank perimeter, rectangular tanks with specific volumes and different aspect ratios were investigated and the best aspect ratios were suggested. The results showed that the rectangular tank with suggested aspect ratios, not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing pressure efficiently.

Free Surface Sloshing Effect on Dynamic Response of Rectangular Storage Tanks

Dynamic analysis of liquid storage tanks is one of interesting subjects in the earthquake engineering. In the present paper, the staggered displacement method is utilized for analysing concrete storage tanks. In the proposed method, surface sloshing of the liquid do main is considered in addition to the effect of impulsive component of the liquid on the structure response. Also, different damp ing coefficients are applied on the various co mponents of the liquid. Foundation is assumed to be rig id and an artificial dynamic load as well as a real ground mot ion record are used to analyse the tank-liquid coupled system in t ime domain. The resulted response is co mpared with those obtained from the co mmercial software. It is found that the convective term affects responses extensively and must be considered in seismic safety analysis of storage tanks.

Etude de la réponse sismique des réservoirs de stockage rectangulaires

ABSTRACT The aim of this work is the evaluation of the seismic response of rectangular storage tanks taking into account the effects of fluid-structure interaction and free surface sloshing of the stored liquid. The study is based on a classical finite element model obtained by the discretisation of both the reservoir structure and the stored liquid domain into linear quadrilateral isoparametric elements. The unknown basic variable of the discrete problem is the coupled nodal values of the structure's displacements and the liquid pressure field. The dynamic forces linking the two subsystems are handled by inforcing a dynamic equilibrium condition between the accelerations and the pressures at the fluid structure interface. Modal analysis has been conducted by introducing a symmetrisation technique which allows to take into account sloshing effects with out matrix inversion process usually utilised in fluid-structur interaction models.

The effect of diffuser configuration on thermal stratification in a rectangular storage tank

This study is to systematically analyze the effect of various kinds of design factors on the stratification performance of a rectangular storage tank. Special interest is focused on the diffuser configuration, which crucially impacts the performance of a storage tank. Herein, a new diffuser shape is proposed, which exemplifies improved performance. Three-dimensional unsteady numerical experiments are conducted for four design parameters of a stratified thermal storage tank: Three design parameters with three levels (i.e., the Reynolds number=400, 800, and 1200; the Froude number=0.5, 1.0, and 2.0; and the area ratio of the diffuser to tank cross-section=0.0327, 0.0582, and 0.131) and one design parameter having two levels (i.e., diffuser type=radial plate type and radial adjusted plate type). Orthogonal array L 18(2×3 7) is adopted for the analysis of variance. The result gives quantitative estimation of the various design parameters affecting the performance and helps to determine the main factors for the optimum design of a stratified thermal storage tank. In the range of parameters considered, the Reynolds number is found to be the most dominant parameter. Moreover, the diffuser shape plays a significant role on the performance of a stratified thermal storage tank.

A Numerical Analysis of the Stratification Properties of Chilled Water Storage Tanks Charged at Freezing Point Temperature

The purpose of the present work is to investigate the potential for buoyancy induced stratification and /or turbulent mixing as a function of the Archimedes number. Both axisymmetric cylindrical and rectangular storage tanks are considered

Packed bed thermal storage systems

Experiments were conducted on a vertical flow packed bed sensible thermal storage system. The packing consisted of hollow high density polyethylene spheres filled approximately 95% with water, and water was also used as the working fluid. Experimental results show the effect of altering D E (the equivalent sphere diameter of the packing) on the degree of axial dispersion in thermally short packings. The significance of thermally short versus thermally long packings to designers of sensible storage packed bed systems is discussed. Experimentally measured average temperature wave velocities in the packing are presented. The significance of natural convection during heat exchanger operation is also demonstrated experimentally. Natural convection may explain instabilities in packed bed convection coefficients reported in the literature. It is shown that one-dimensional temperature profiles in the packing can be obtained using rectangular storage tanks in conjunction with flow distributors.