Liquid Fill Level Research Articles

Shape design of vessels for sloshing frequency

Sloshing is oscillatory motion of the liquid free surface contained in a vessel. Many classical studies investigating this fascinating phenomenon assume a fixed shape for the container and calculate sloshing frequencies as a function of liquid fill level. In this article, geometry of vessel is assumed unknown in the problem which is determined according to a pre-defined variation of the fundamental sloshing frequency with respect to the liquid fill level. In order to formulate such a problem, Christoffel–Schwarz conformal mapping is employed to develop a semi-analytical model for analysis of sloshing characteristics in two-dimensional polygonal containers. Consequently, this model is inserted in a suitable iterative algorithm to find the shape of the vessel based on variation of fundamental sloshing frequency with the liquid fill level. To demonstrate the validity of the method, the shape of a horizontal circular container is reconstructed by making use of the sloshing frequencies given in the literature. Then, the developed algorithm is systematically employed to determine the shape of the containers associated with a series of well-defined frequency functions.

Dry catalyst impregnation in a double cone blender: A computational and experimental analysis

The dry impregnation of catalysts is widely used in industrial catalyst preparation, however, until recently, it has not been possible to model this system computationally. In this work, a novel algorithm for the spray and inter-particle transfer of fluid onto and within a rotating bed of granular catalyst support was explored using discrete element method (DEM). The simulations were validated by experiments utilizing a geometrically identical double cone blender fixed with a single nozzle impregnator. The effects of liquid flow rate and fill level were explored at a fixed rotation rate of 25rpm. Specifically, three flow rates of 1.5, 2.5 and 5L/h were selected and evaluated at a 30% and 45% fill fraction by volume. Mixing analysis and fluid concentration distributions were used both experimentally and computationally to investigate the propagation of fluid throughout the bed with the goal of modeling and improving industrial content uniformity. It was discovered that low flow rate systems and lower fill fractions resulted in better mixing and content uniformity throughout the bed. Results obtained from our model show good agreement with experiments, and therefore it was demonstrated that a novel fluid transfer algorithm incorporated into DEM could be used to accurately model dry catalyst impregnation, therefore introducing a new tool for optimizing catalyst manufacturing.

The liquid nitrogen fill level meter for the AGATA triple cluster detector

A novel liquid nitrogen fill level meter has been put into operation for the all-position dewar of the triple cluster detector of the Advanced GAmma Tracking Array. The new device is based on a capacitance measurement between a metallic cylindrical tube inside the dewar and the inner wall of the cryostat. The fill level dependent capacitance is converted by a C/ V-transducer into a DC voltage signal. Direct monitoring of the LN 2 level inside the detector dewar has been performed with several AGATA detectors at various inclinations and rotation angles of the detector axis. The time-dependent LN 2 consumption is an additional quantity used to survey the status of the cryostat. Supplementary results are the investigations of the LN 2 consumption and the heat loss of the detector during different modes of operation.

Effect of anti-slosh baffles on free liquid oscillations in partially filled horizontal circular tanks

An exact two dimensional hydrodynamic analysis based on the linear potential theory is introduced to study the free liquid sloshing characteristics of transverse oscillation modes in a non-deformable horizontal circular cylindrical baffled container which is filled to an arbitrary depth with an inviscid incompressible liquid. Three common baffle configurations are considered: a pair of internal rigid horizontal side baffles of arbitrary extension installed at the free liquid surface, and a surface-piercing or a bottom-mounted vertical rigid baffle of arbitrary extension positioned along the tank vertical axis of symmetry. The problem solution is obtained by the method of successive conformal coordinate transformations, leading to standard truncated matrix eigenvalue problems on simple (rectangular) regions which are then solved numerically for the resonance eigen-frequencies. The effects of liquid fill level, baffle arrangement and length upon the three lowest antisymmetric and symmetric sloshing frequencies and the associated hydrodynamic pressure mode shapes are examined. Also, convergence of the adopted approach with respect to the fill condition, and baffle type/extension is discussed. Limiting cases are considered and the validity of results is established in comparison with the data in the existing literature.

A novel flat heat pipe and its thermal performance analysis

The paper presents a novel flat heat pipe that has the characteristics of easy to construct, can withstand a higher pressure when vacuumed and can be constructed into various scales. The thermal performance of the novel flat heat pipe with or without the wick was analysed using an analytical model. The analysis related to the relations of the maximum heat transport capacity with liquid fill level, working temperature and heat pipe geometry dimension for different working fluids. Copyright The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org, Oxford University Press.

Shaker-based heat and mass transfer in liquid metal cooled engine valves

The highly transient process of the working combustion engine generates a “shaker-effect” inside the hollow valve stem where liquid sodium carries the heat from the hot valve head to the valve stem. Here it can pass through the valve guide, based on convective heat transfer and thermal conduction. The efficiency of these transport mechanisms is still not clearly understood, since the design of many liquid cooled valves is mostly based on empirical knowledge and can lead under certain conditions to a breakdown of the system. A simulation of the processes during the movement of the valve including detailed insight into the highly transient and complex two-phase flow phenomena as well as the heat transfer has been realized by means of direct numerical simulation (DNS) based on the volume-of-fluid (VOF) method. The influence of several relevant influencing factors such as the geometry, the acceleration and the liquid fill level were studied. It was found that the fill level is one of the most influencing factors regarding the efficiency of the heat transfer whereas the influence of geometrical dimensions and in particular the aspect ratio of the cavity were almost negligible in our setup. By averaging the fluid flow and the temperature field it has been shown that liquid cooled valves are more efficient compared to a solid valve but clustering of the liquid filling can appear which causes a temporal breakdown of the “shaker-effect”. In addition the influence of the spatial resolution is shown and 2D vs. 3D simulation setups are compared. To our knowledge, no similar heat transfer predictions of the presented type are published in the literature.

Boiling of Water at Subatmospheric Conditions With Enhanced Structures: Effect of Liquid Fill Volume

Liquid cooling with phase change has been demonstrated to be a very efficient technique for thermal management of electronics because it has the potential to achieve high heat transfer coefficients compared to single phase liquid cooling. Previous studies on liquid immersion cooling with fluorocarbons have shown the effectiveness of boiling enhancement structures in lowering boiling incipience, raising the critical heat flux, and reducing evaporator size. Two-phase thermosyphons are an alternative to liquid immersion cooling, where phase change liquid cooling can be implemented within a closed-loop device. The present study involves a two-phase thermosyphon with boiling enhancement structure in the evaporator, which is subjected to subatmospheric pressures for lowering the saturation temperature of the working fluid. The objective of the present research is to provide a detailed understanding of the effect of liquid-fill level on boiling of water with enhancement structures at subatmospheric pressures. The study will take into account the influence of system pressure and enhancement structure geometry on the boiling heat transfer. Experiments were performed at three different pressures, 9.7kPa, 15kPa, and 21kPa, using a stacked enhancement structure with three different geometries (one, four, and six layers), corresponding to three different liquid-fill levels (fill ratios of 0.5, 0.7, and 0.9). The results are compared with a base line study on subatmospheric pressure boiling from a plain surface at similar liquid-fill levels.

The Effect of Reduced Design Margin on the Fire Survivability of ASME Code Propane Tanks

In the 1999 addenda to the 1998 ASME pressure vessel code, Section VIII, Div. 1 there was a change in design margin for unfired pressure vessels from 4.0 to 3.5. This has resulted in the manufacture of propane and LPG tanks with thinner walls. For example, the author has purchased some new 500 gallon ASME code propane tanks for testing purposes. These tanks had the wall thickness reduced from 7.7 mm in 2000 to 7.1 mm in 2002 and now to 6.5 mm in 2004. These changes were partly due to the code change and partly due to other factors such as steel plate availability. In any case, the changes in wall thickness significantly affects the fire survivability of these tanks. This paper presents both experimental and computational results that show the effect of wall thickness on tank survivability to fire impingement. The results show that for the same dank diameter, tank material, and pressure relief valve setting, the thinner wall tanks are more likely to fail in a given fire situation. In severe fires, the thinner walled tanks will fail earlier. An earlier failure usually means the tank will fail with a higher fill level, because the pressure relief system has had less time to vent material from the tank. A higher liquid fill level at failure also means more energy is in the tank and this means the failure will be more violent. The worst failure scenario is known as a boiling liquid expanding vapor explosion and this mode of failure is also more likely with the thinner walled tanks. The results of this work suggest that certain applications of pressure vessels such as propane transport and storage may require higher design margins than required by Section VIII ASME code.

Performance of Graphite Foam Evaporator for Use in Thermal Management

This paper presents the results of an investigation of the thermal performance of a graphite foam thermosyphon evaporator and discusses the foam’s potential for use in the thermal management of electronics. The graphitized carbon foam used in this study is an open-cell porous material that consists of a network of interconnected graphite ligaments whose thermal conductivities are up to five times higher than copper. While the bulk graphite foam has a thermal conductivity similar to aluminum, it has one-fifth the density, making it an excellent thermal management material. Furthermore, using the graphite foam as the evaporator in a thermosyphon enables the transfer of large amounts of energy with relatively low temperature difference and without the need for external pumping. Performance of the system with FC-72 and FC-87 was examined, and the effects of liquid fill level, condenser temperature, and foam height, width, and density were studied. Performance with FC-72 and FC-87 was found to be similar, while the liquid fill level, condenser temperature, geometry, and density of the graphite foam were found to significantly affect the thermal performance. The boiling was found to be surface tension dominated, and a simple model based on heat transfer from the outer surface is proposed. As much as 149W were dissipated from a 1cm2 heated area.

Analytical and numerical simulation of the thermal performance of `mini' gravitational and `micro' gravitational heat pipes

An analytical model has been developed to investigate the performance of a `mini' gravitational heat pipe and two `micro' gravitational heat pipes of different sizes, using water as the refrigerant. The model has been used to determine the limits of heat transport capacity, which expresses the thermal performance of heat pipes. The model is defined in terms of the physical shape of the heat pipes and evaluates the limits of heat transport capacity as functions of the properties of the working fluid used, the inclination angle and liquid fill level. A numerical model has also been developed and used to investigate the operating characteristics of the heat pipes. The results are presented in terms of the cross-sectional areas, pressures, temperatures and mass flow rates of the liquid and vapour within the heat pipes. In general, the modelling results indicate `micro' gravitational heat pipes have higher heat transport limits than `mini' heat pipes of the same cross-sectional area.

Structure optimisation and performance simulation of a novel thin membrane heat pipe solar collector using a mathematical model

SYNOPSIS A novel thin membrane heat pipe solar collector was designed to be a compact, efficient and low cost heat generator capable of achieving temperatures up to 250°C and suitable for generating electricity and hot water for domestic and industrial use. Two variations of this, “normal” and “thermosyphon”, were indicated and their performance was investigated. The mathematical theory and simulation approach used for efficiency and solar irradiation calculation, geometry and size optimisation as well as numerical analysis were summarised. Influences of geometry, liquid fill level, inclination and working temperature on collector performance were analysed, and the thermal behaviours of the collector under given conditions, including liquid and vapour cross-sectional areas, liquid and vapour pressures, liquid, vapour and wall temperatures, mass flow rate and start-up process, were described in detail. A number of conclusions regarding the aspects above were given.

Steady Turning Stability of Partially Filled Tank Vehicles With Arbitrary Tank Geometry

Steady turning model of a partially filled tank vehicle is developed by integrating the roll plane model of the partially filled arbitrarily shaped tank with the static roll plane model of an articulated vehicle. The rollover immunity of the tank vehicle is investigated through computer simulation. The motion of the free surface of liquid and the associated load shift encountered during steady turning are computed using an iterative algorithm. The influence of tank geometry and liquid fill level on the rollover immunity of the tank vehicles is presented. Rollover threshold levels of a tractor-semitrailer vehicle with tanks of circular, modified square and modified oval cross sections are investigated for various fill levels. The influence of compartmenting of the tank on the steady turning response of the vehicle is presented and an optimal order of unloading the various compartments is determined. The study concludes that load shift encountered during steady turning has an adverse effect on the overturning limits of the articulated liquid tank vehicles. The stability of such tank vehicles may be further affected by the dynamic fluid-structure interactions, vehicle transients and driver’s reaction.