Storm water detention tanks are widely used for the control of combined sewer overflows. Conventional continuous simulation and recently developed analytical probabilistic models have been used for ...analyzing the hydrologic operation of storm water detention tanks. These analyses are necessary in order to accurately estimate the runoff capture efficiency of a given control system or the required storage capacity for achieving a desired runoff capture efficiency. The analytical probabilistic models still have the shortcomings of making simplifying assumptions about the initial storage conditions of a detention tank. Developed in this study is a new stochastic analysis method which can provide similar results as provided by continuous simulations and overcome some of the shortcomings of the previously developed analytical probabilistic models. This stochastic analysis method uses closed‐form analytical equations to estimate the runoff capture efficiency and required storage capacity. Results from these analytical equations are validated by comparing with continuous simulation results and close agreements are observed. These analytical equations are therefore proposed as a computationally efficient alternative for analyzing the hydrologic performance of combined sewer overflow tanks.
Plain Language Summary
Storm water detention tanks are widely used for the control of combined sewer overflows. Conventional continuous simulation and recently developed analytical probabilistic models can be used for analyzing their hydrologic operations. Continuous simulations are time consuming to perform and require a large amount of input data. Analytical probabilistic models still have the shortcoming of making simplifying assumptions about the initial storage conditions of a detention tank. A new analytical stochastic model is developed in this study which eliminates the shortcomings of both the continuous simulation and analytical probabilistic approaches. The new analytical stochastic model uses closed‐form equations to directly estimate the system performance statistics. It can thus be used as a convenient tool for the planning, design, and operation of combined sewer overflow tanks.
Key Points
A new analytical stochastic approach was developed to evaluate the hydrologic performance of combined sewer overflow tanks
Results of the proposed approach compare well with conventional continuous simulation results
The proposed approach can be used as a convenient tool for the planning, design, and operation of combined sewer overflow tanks
Large earthquakes in the last 25 years have caused significant damage to buildings and infrastructure, including the partial or total collapse of storage tanks in various industries. Elephant foot ...buckling, or local buckling at the base, is one of the main failure modes observed in these structures, and this failure mode can lead to their collapse and/or complete loss of contents. Although hydrostatic and hydrodynamic loads typically affect the seismic response of tanks, the effect of soil type on tank buckling behavior has not been widely studied or recognized. This research aims to evaluate the effect of soil type on seismic fragility of tanks by analyzing typical storage tanks used in the wine industry. The work focuses on elephant foot buckling for tanks with both unanchored and anchored bases and compares the influence of three different types of soil and two different tank geometries. The approach uses the capacity spectrum method, as opposed to the more commonly used incremental dynamic analysis, to determine a critical peak ground acceleration to cause buckling at the tank. The tanks were subjected to 21 Chilean seismic records with three different soil types and a no-soil condition. From the results a lognormal fragility curve, and its median and standard deviation, are calculated. The results indicate that unanchored tanks built softer soils exhibit poorer performance, while tanks in competent soils and rock exhibit good performance. Anchored tanks show less sensitivity to soil types than unanchored tanks. The study demonstrates the importance of considering soil-foundation-structure interaction for wine storage tanks, but the results indicate that many comparable storage structures will be similarly affected.
•Examining how soil-foundation-tank interactions affect liquid tank buckling with finite element models•Seismic fragility of liquid storage tanks is evaluated for three different soil types.•The soil type induces dispersion in the seismic fragility curves.•Anchoring tanks is shown to reduce the dispersion in the seismic fragility curves.
► Rainwater harvesting is becoming popular in Australia. ► Rainwater tanks are investigated for 10 locations in Greater Sydney. ► Water savings remarkably vary with locations in Greater Sydney. ► ...Rainwater tanks are not financially viable without Government subsidy.
Due to greater environmental awareness and mandatory water restrictions in many Australian cities, rainwater tanks have become popular in recent years. This paper investigates the water savings potential of rainwater tanks fitted in detached houses at 10 different locations in Greater Sydney, Australia. A water balance simulation model on daily time scale is developed and water savings, reliability and financial viability are examined for three different tank sizes, 2kL, 3kL and 5kL. It is found that the average annual water savings from rainwater tanks are strongly correlated with average annual rainfall. It is also found that the benefit cost ratios for the rainwater tanks are smaller than 1.00 without government rebate. It is noted that a 5kL tank is preferable to 2kL and 3kL tanks and rainwater tanks should be connected to toilet, laundry and outdoor irrigation to achieve the best financial outcome for the home owners. The results from this study suggest that government authorities in Sydney should maintain or possibly increase the rebate for rainwater tanks to enhance its acceptance.
In the building sector, 40% of final energy is used for heating and cooling. Up to 75% of this is used in residential buildings. It is necessary to take a step forward and reduce this share of energy ...consumption, in particular through the use of efficient technologies and their integration into the system of renovation of residential buildings, which is a major challenge for future research in this field. An important technology for achieving this goal is heat storage, where the use of phase change materials as heat storage material allows for a higher energy density. The main advantage of using heat storage technologies is the solution of the problem of the temporal divergence of energy demand and the possibility to use a higher share of energy from renewable sources, e.g. such as solar energy. Solar energy as a resource can be used during the day, when production is higher than demand, which allows storing energy for a later period of demand. This also improves the efficiency of the heat generators in the system in which the thermal storage is integrated. The focus of the present study is on the investigation of phase change materials (PCM) as thermal storage in the conventional water tank storage. A comparison was made between a conventional sensible thermal energy storage tank and a hybrid latent heat storage tank, where the PCM was encapsulated in cylindrical nodules and integrated into the water tank to improve the energy density of the conventional water heat storage tank. The results of the experiment showed that 15% of the PCM inside the water storage tank increases heat storage for 70% over conventional heat storage tank with water only inside. The measured experimental data were compared with the simulation results from TRNSYS model to enable further analysis and improvement of the heat storage tank with PCM integration.
Liquefied natural gas has recently received much attention due to the tightened environmental regulations associated with sulfur oxide and nitrogen oxide. LNG is generally stored in liquid form below ...its saturation temperature of −162 °C. During the storage process at the floating storage regasification unit, LNG continuously evaporates, and it results in the pressure build-up inside the tank leading to potential hazards unless the pressure is controlled properly. In this study, the variation in the pressure and temperature inside the storage tank was estimated by conducting a dynamic simulation of the mathematical model of a non-equilibrium LNG tank. For this, different initial filling ratios (i.e., 10, 50, and 94 vol%) were applied to the modeling and its analysis. First, the model was divided into three zones to enhance its accuracy: vapor, upper and lower LNG zones. Then, two scenarios (i.e., “sealed tank mode” and “venting mode”) were adopted for simulation. Finally, the evaporation rate of LNG was estimated based on its initial filling ratio. As a result, we could estimate the change of pressure and temperature accurately during the operation of the LNG storage and develop an operating strategy based on the different initial filling ratios.
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•A non-equilibrium LNG tank model is developed for large scale LNG tank.•Three separate zones inside the LNG storage are considered for modeling.•Two scenarios are considered: sealed tank and vapor venting condition.•The pressure and temperature increase relatively fast at low filling ratio.
•Establish air chamber model in hydroelectric generating system (HGS) during successive load rejection.•Analyzes the different performance of orifice surge tank and air chamber tank in HGS.•Apply the ...modified NSGA-II algorithm for multiple objective optimization of air chamber tank.•Provide essential guidance for decision-makers to deal with hydraulic transient in successive load rejection process.
Surge tank is an essential device to control hydraulic transient of a Hydroelectric Gnerating Systems (HGS)s. However, various types of surge tanks differently reflect in reducing water hammer and improve performance of HGS. This study aims to analyze the different performance of Air Chamber Tank (ACT) and Orifice Surge Tank (OST) during the successive load rejection process (SULRP). In this study, the mathematical model of the ACT is established and use to analysing the replacement the existing OST in Shitouxia Hydropower station consisting in three parallel unit system.
A modified NSGA-II algorithm is used to perform multiple objective optimization ACT properties and to minimize pressure head in ACT and water head at the inlet of units. The optimization result indicates that the proper selection of initial indoor air height and delay time lead to the decrease maximum water head and fluctuation period in surge tank and falls in overspeed and pressure head at inlet of unit. The results show that, the diameter of ACT can be 2 m smaller than the existing OST and it can decrease the fluctuation period from 130 s to 110.7 s while slightly increasing the overspeed in the last unit. The increasing delay time of the closing guide vane of last unit decreases the water fluctuation in ACT and OST and the maximum water fluctuation in OST and ACT reduce with slope −6.2% and −15% when ΔTd is in range of 14,25 seconds. Finally, the optimized dimension of ACT and OST provides essential guidance for decision-makers to deal with hydraulic transient in SULRP.
The effect of variation of longitude and latitude on the amount of solar radiation is investigated in this work in the Iranian climate context on different solar collectors and storage tank ...geometries. An equation for prediction of solar radiation intensity is presented through regression analysis (R2 = 0.9976). The effects of different types of storage tanks, change of Grashof number, and change of time of experiments on the thermal characteristics of the evacuated tube solar collectors are numerically investigated. Solar irradiance on the collector surface was simulated via P-1 method. Results demonstrated that changing longitude does not influence the amount of solar radiation, whereas change of latitude affects such amount, and regions with higher latitudes (northern areas) receive more beam radiation around solar noon. In addition, the tank with longer height absorbs more heat, and presents a better efficiency. Also, the tank geometry affects its performance; the useful heat gain of a collector possessing a vertical square tank is about 10% more than that of a collector with a cylindrical tank without consideration of heat loss from the tank. Nonetheless, considering such heat loss, the collector with cylindrical tank presents the highest performance due to minor heat loss area of the tank.
•Regression analysis of solar irradiance prediction in Iran was undertaken.•The numerical study is validated by experimental data of a similar study.•Effect of different types of storage tanks on performance of the solar collectors.•Thermal performance of evacuated tube solar collectors in different months of year.•Characterizing the optimum tank type with and without regarding the heat loss.
Abstract
In order to improve the accuracy of the stratified hot water storage tank model and simplify the modeling process of the stratified water tank, a modelling method of the stratified water ...tank based on MATLAB/SIMULINK is proposed. By comparing with TRNSYS platform simulation, the correctness and accuracy of this method are verified. At the same time, this method is used to establish a six-node stratified hot water storage tank. Through the simulation of 8 different working conditions, the influence of different inlet and outlet water flow rates and temperature of the inlet and outlet water on the stratification effect of the hot water storage tank is analyzed.
•A review in characterization of water tanks performance.•Stratification in water tanks.•Different hydraulic schemes to maximize stratification.
To assure high quality thermal storage and high ...efficiency of its acquisition, thermal stratification is often employed in domestic hot water tanks. The whole motivation of stratification lies in the fact that mixing effect can be minimized during operational cycle of the tank so that high temperature water could be taken at the load end, thus maintaining high thermal efficiency at demand side, while low-temperature water can be drawn at lower bottom, thus maintaining the high efficiency at energy collection side. The study of stratification entails the assessment of a wide variety of concepts to be embodied around the central theme of the tank – its design and modelling. This paper presents a systematic review pertaining to various such concepts. For instance, multi-node and plug-flow approach to model various temperature distribution models are considered. These models are categorized in paper as linear, stepped, continuous-linear and general three-zone temperature distribution models. Subsequently, the dynamics of thermocline decay and influencing parameters both during standby and dynamic mode will be demonstrated. In addition, a survey of state of the art methods and practices to ascertain the performance improvement and its quantification will be illustrated. This includes geometrical parameters – such as, structural design incorporation, essentially – inlet design, tank aspect ratio and wall material specification, and also, operational parameters to curb down the inlet mixing. Practice techniques and methods which are presented here in a novel way, extend towards the ground of practical application and research procedures.
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