An analysis of bottom entry nozzles for atmospheric storage tanks

In this paper, we describe the analysis of soil settlement in the vicinity of a bottom entry nozzle of an atmospheric storage tank for several practical loadings. These are the pressure of the liquid stored in the tank, the body force of the rock and soil foundation, and an external moment applied to the nozzle where it emerges from the foundation. The foundation is modelled as a three-dimensional elastic medium which can support no tensile stress and is composed of two materials (rock and soil) with an elastic cylindrical shell embedded in the rock phase. The solution is accomplished with a general-purpose finite element program (ICES—STRUDL II). The overall conclusion reached is that bottom entry nozzles are acceptable for tankage installed on reasonably good soil.     

Analytical and experimental investigation of thermal stratification in storage tanks

An analytical and experimental investigation of transient turbulent two-dimensional charging and discharging of a sensible heat storage tank has been conducted. Parametric studies showed that the turbulent mixing factor due to hydrodynamic disturbances at the inlet ports is the most significant item in the performance of thermal stratification storage tanks. Furthermore, the effect of the aspect ratio and convection at the walls in promoting stratification have been studied. Comparison with experimental data showed the capability of the present analytic approach to accommodate, with a satisfactory degree of accuracy, such problems.     

Plastic behaviour of oblique flush cylindrical nozzles in cylindrical pressure vessels: An experimental investigation

Results of seven tests on cylindrical pressure vessels with flush cylindrical nozzles are reported. Two of the test specimens had radial nozzles and the rest had nozzles oblique to a radial line but normal to the longitudinal axis of the vessel. The specimens were machined out of solid 8 in diameter aluminium alloy bar. Electrical resistance strain gauges were used to measure the distribution of strain. Deflections were measured using clock-gauges and displacement transducers.     

Three-dimensional analysis and investigation of the thermal and hydrodynamic behaviors of cylindrical storage tanks

A numerical analysis of the three-dimensional temperature and velocity fields in horizontal cylindrical storage tanks was performed. The phenomena of laminar natural convection and vertical stratification of temperature were considered. The developed three-dimensional transient computing code solves the equations of energy and momentum through the finite volume method. The simulation of fluid cooling process inside the tank showed the formation of stratified temperature profiles that matched those obtained experimentally. Based on several simulations, a correlation was proposed for determining the degree of thermal stratification inside the tank regarding thermal and geometrical parameters. From this correlation, an expression was proposed to predict the fluid temperature profiles along the time. This information is very important in many applications, such as in thermosiphon solar water heating systems, where the global efficiency of the system increases with the thermal stratification degree of the working fluid. Another case studied considered that the tank was connected to solar collectors, aiming at investigating the influence of the inlet jet position with and without a baffle plate on the preservation of the thermal stratification. Results showed that the baffle plate modified the velocity and temperature fields close to the inlet jet, allowing a better thermal stratification. Also the suitable choice of the inlet jet position allowed the formation of a more effective thermal stratification. Some other aspects of the internal dynamics of this kind of storage tank are presented and discussed. For the cases studied, the inlet jet next to the top led to a greater thermal stratification. However, it was verified that when the inlet jet temperature remains constant for a long period of time, and thus its temperature approaches the temperature of the water inside the tank, for the same height, the temperature profiles obtained become similar to the case of the inlet located at usual height of 2/3 of the diameter.     

Radial loads on pad reinforced nozzles in spherical pressure vessels—A theoretical analysis and experimental investigation

A theoretical elastic analysis has been carried out of the stresses due to a radial load applied to a pad reinforced nozzle in a spherical pressure vessel. Experiments have been carried out applying a radial load of 0·49 MN (50 tons) on one nozzle 0·51 m (16 in) outside diameter by 12·7 mm ($\text{1}\text{2}$ in) thick in a spherical vessel₁ 1·83 m (72 in) outside diameter by 12·7 mm ($\text{1}\text{2}$ in) thick. The pad reinforcement was 9·5 mm ($\text{3}\text{8}$ in) thick and of 0·216 m (8·5 in) radial width. The experimental results confirm the theoretical analysis for the distribution of stresses but the effect of the welds on the stresses at the shell intersections is significant.     

Shear loading of pad reinforced nozzles in spherical pressure vessels—A theoretical investigation

A theoretical elastic analysis is given of a radial nozzle in a pad reinforced spherical vessel subjected to a shear force applied at the nozzle/sphere intersection. Curves of stress concentration factors based on the maximum principal stress and the maximum shear stress are given for a wide range of geometrical parameters. The limitations of the analysis due to the use of thin shell theory are discussed.     

Experimental and numerical investigation of localized fire test for high-pressure hydrogen storage tanks

Vehicle fires may cause localized fires on on-board high-pressure hydrogen storage tanks. To verify the safety performance of such tanks under localized fire exposure, a localized fire test was proposed in the Global Technical Regulation for Hydrogen Fuel Cell Vehicles. However, practicality and validity of the proposed test still require further verification. In this paper, this new fire test was experimentally investigated using the type 3 tanks. Influences of hydrogen and air as the filling media were studied. A three-dimensional computational fluid dynamics model was developed to analyze the effects of filling pressure and localized fire exposure time on the activation of thermally-activated pressure relief device (TPRD). The experimental results showed that temperature distribution on the tank surface was uneven around the circumference. The rising temperature of internal hydrogen or air contributed little to TPRD activation. The simulation results indicated that TPRD activation time was slightly affected by the variations of the filling pressures, but it increased when the localized fire exposure time was extended.     

Hydrogen storage in zeolite imidazolate frameworks. A multiscale theoretical investigation

A multiscale approach is used to investigate the hydrogen adsorption in nanoporous Zeolite Imidazolate Frameworks (ZIFs) on varying geometries and organic linkers. Ab initio calculations are performed at the MP2 level to obtain correct interaction energies between hydrogen molecules and the ZIF structures. Subsequently, classical grand canonical Monte-Carlo (GCMC) simulations are carried out to obtain the hydrogen uptake of ZIFs at different thermodynamic conditions of pressure and temperature.     

Shape optimisation of axisymmetric cylindrical nozzles in spherical pressure vessels subject to stress constraints

In this study, optimal shapes of intersecting pressure vessels are sought using a novel topology/shape optimisation method, called Metamorphic Development (MD). An industrial benchmark design problem of finding the optimal profile of variable thickness that connects a spherical shell pressure vessel to a cylindrical nozzle is considered. Two types of intersecting structures, distinguished by flush and protruding nozzles, are investigated. The optimum profiles of minimum mass intersecting structures are found by growing and degenerating simple initial structures subject to stress constraints. The optimisation seeks to eliminate the stress peaks caused by the opening. The optimised structures are developed metamorphically in specified infinite design domains using both rectangular and triangular axisymmetric finite elements that are ideally suited for modelling continua with curved boundaries. It is shown that the design with a protruding nozzle would produce a better stress distribution than the design with a flush nozzle. The results demonstrate the success of the method in generating suitable, practical solutions to the design problem.     

Some theoretical and experimental aspects of built-in solar storage

The possibility of using a built-in storage solar water heater in Jordan has been investigated. Experimental and theoretical results were obtained using a 90 × 90 × 10 cm solar heater which was tilted at an angle of 30° to the horizontal.It was found that the efficiency of the built-in storage solar heater may reach as high as 78% with a maximum increase in the water temperature of 70°C and at low cost compared to the conventional flat plate collector. It is therefore expected that such solar system may be used to provide reasonably sufficient hot water in Jordan. Analytical solution, based on the assumption that the water temperature equals that of the plate, was used to solve the governing equations. While a numerical solution was used to solve the equations under the condition that the plate temperature is not equal to that of the water.It was found that the assumption of the temperature of the plate (T_p) is equal to the temperature of water (T_w) is only justifiable at early hours of operation in the morning.     

A theoretical and experimental investigation of a novel built-in-storage solar water heater

In this work, a novel built-in-storage type solar water heater of about 87 l capacity has been investigated theoretically and experimentally for the case of no draw-off. The solar water heater which performs the dual function of absorbing and storing hot water is made of 5 pipes, each of length 1.8 m and diameter 12 cm. A baffle plate is placed inside each pipe. The experiments have been performed inside the laboratory using an artificial Sun consisting of 27 lamps. The water temperatures have been measured at various locations in the system. In the theoretical study, transient performance of the system is predicted by solving the mathematical model consisting of energy balance equations written for each control volume comprising one length of pipe. These equations are converted to finite difference form and then solved by a personal computer. The experimental results have been compared with the numerical model and a good agreement has been found between the experimental results and the theoretical predictions.     

Hydrogen storage in gas reservoirs: A molecular modeling and experimental investigation

Hydrogen is one of the clean energy sources that can be used instead of fossil fuel sources to reduce greenhouse emissions. However, hydrogen supply intermittency significantly reduces the deployment and reliability of this energy resource. Therefore, this work investigates the underground storage of hydrogen in depleted gas reservoirs to avoid seasonal fluctuations in hydrogen supply and assure long-term energy security. The obtained results from molecular simulation (Density Functional Theory) revealed hydrogen is adsorbed physically on calcite (104) and silica (001) surfaces on different adsorption configurations. This conclusion is supported by low adsorption energies (?0.14 eV for calcite and ?0.09 for silica) and by Bader charge analysis, which showed no indication of charge transfer. The experimental results illustrated that hydrogen has a very low adsorption affinity toward carbonate and sandstone rocks in the temperature range of 50–100 °C and pressure up to 20 bar. These results show the potential of depleted gas reservoirs to store hydrogen for s is useful in hydrogen recovery as no hydrogen will be adsorbed to the rock surface of conventional gas reservoirs.     

A storage tank for vehicular storage of liquid hydrogen

This article outlines a concept for a new method of fabricating cryogenic liquid hydrogen storge tanks with emphasis on the application of liquid hydrogen as an automotive fuel. It includes a recapitulation of the properties of hydrogen and gasoline for reference, a discussion of automotive fuel utilisation rates, a thermal analysis of the liquid hydrogen boil-off rate for a reference storage container and the new concept tank. In addition, an analysis of the tank concept and its method of assembly line fabrication are provided. The conclusions reached are that this fabrication concept would provide a liquid hydrogen storage tank of improved thermal performance, that the tank could be potentially less expensive to build than current technology tanks, and that the tank would be suitable for automotive containment of liquid hydrogen.     

The theoretical and experimental investigation of the phase-change solar thermosyphon

The paper is concerned with the study of two-phase solar thermosyphon for domestic hot water (SDHW). Due to a combination of ideas of the heat pipe and classical thermosyphon, the heat transfer in the proposed installation is to be realised by the liquid - gas phase change, what should increase significantly both the heat efficiency of the system and the system applicability.     

Improved design of metal-organic frameworks for efficient hydrogen storage at ambient temperature: A multiscale theoretical investigation

A multiscale theoretical technique is used to examine the combination of different approaches for hydrogen storage enhancement in metal-organic frameworks at room temperature and high pressure by implementation lithium atoms in linkers. Accurate MP2 calculations are performed to obtain the hydrogen binding sites and parameters for the following grand canonical Monte Carlo (GCMC) simulations. GCMC calculations are employed to obtain the hydrogen uptake at different thermodynamic conditions. The results obtained demonstrate that the combination of different approaches can improve the hydrogen uptake significantly. The hydrogen content reaches 6.6 wt% at 300 K and 100 bar satisfying DOE storage targets (5.5 wt%).     

A numerical study for the prediction of turbulent mixing factor in thermal storage tanks

The transient behavior of thermal stratification in storage systems were investigated numerically. An efficient computer code based on Chapeau-Galerkin integral formulation is developed. The validation of the present scheme is verified against published experimental and finite difference results. The predictions are adequately simulate the published data. The present results showed that the turbulent mixing (or eddy conductivity) factor caused by hydrodynamic disturbances at the inlet and outlet ports of storage tank plays an important role in the performance of thermal stratification storage tanks. The eddy conductivity factor is included in the model to yield good agreement with experimental data. Further, the variation of this factor is expressed in a decreasing exponential function in terms of Reynolds and Richardson numbers. The effect of nodal grid size on the computed results is also investigated. It is found to have negligible effect on the temperature profiles at moderate grid size.     

A numerical and experimental investigation of different containers and PCM options for cold storage modular units for domestic applications

This paper presents the results of an experimental and numerical study on the solidification of different phase change materials (PCM) encapsulated in spherical and cylindrical shells of different materials and diameters subject to constant surface temperature. The main objective is to determine the time for complete solidification of the PCM and how it is affected by the variations of the surface temperature, material and diameter of spherical shells. As a result of the study, it is expected to define a pair of container and PCM to operate adequately and efficiently together with refrigeration units. The experiments were realized using glass and plastic spherical shells of diameters 0.035, 0.076, 0.106 and 0.131 m, soft drink cans and small plastic water bottles with surface temperatures of ?5, ?10, ?12, ?15, ?18, ?20 and ?25 °C. The phase change materials used are water and mixtures of water with 3.75%, 7.5%, 15%, 25%, 30%, 40% and 50% Glycol content. The results are presented and discussed.     

An experimental and numerical study of thermal stratification in a horizontal cylindrical solar storage tank

The thermal behaviour of a horizontal cylindrical storage tank has been investigated both experimentally and numerically. Four sets of experiments have been carried out where cold water is injected into the bottom of the tank with three different initial thermal fields. The first one is the tank with initial thermal stratification with bottom temperature the same as the inflow temperature. The second set is the tank with the initial thermal stratification, the bottom being at a relatively higher temperature than the inflow temperature. The third set is an initially heated isothermal tank and the fourth is the same as the first set of experiments except that the straight tube inlet nozzle is replaced by a 30° downward bent divergent conical tube. The above experiments show that better thermal stratification can be obtained using the divergent conical tube as the inlet nozzle due to the diffusion effect of the nozzle. Also a slight improvement in the tank performance has been achieved in the second set of experiments when the initial bottom temperature of the tank is higher than the injected cold water temperature. To check the accuracy of the experimental results two different types of one-dimensional numerical models, namely Turbulent Mixing Model and Displacement Mixing Model have been developed and the results are compared with the experiments. This comparison indicates that the numerical results are in good agreement with the experiments especially at the top of the tank.     

Experimental investigation and theoretical modeling of dehydriding process in high-pressure metal hydride hydrogen storage systems

This study explores the endothermic dehydriding (desorption) reaction that takes place in a high-pressure metal hydride (HPMH) hydrogen storage system when hydrogen gas is released to the fuel cell. The reaction is sustained by circulating warm fluid through a heat exchanger embedded in the HPMH powder. A systematic approach to modeling the dehydriding process is presented, which is validated against experimental data using two drastically different heat exchangers, one using a modular tube-fin design and the other a simpler coiled-tube design. Experiments were performed inside a 101.6-mm (4-in) diameter pressure vessel to investigate the influences of hydrogen release rate, heat exchanger fluid flow rate and fluid temperature on the dehydriding process for the HPMH Ti_1.1CrMn. It is shown the dehydriding reaction rate can be accelerated by increasing the fluid temperature and/or the rate of pressure drop. HPMH particles located in warmer locations close to heat exchanger surfaces both began and finished dehydriding earlier than particles farther away. 2-D and 3-D models were created in Fluent to assess the dehydriding performances of the modular tube-fin heat exchanger and coiled-tube heat exchanger, respectively. The models are shown to be quite accurate at predicting the spatial and temporal variations of metal hydride temperature during the dehydriding reaction.