Prediction of two-phase flow through a safety relief valve

Safety relief valves are necessary elements in any pressurised system. The flow inside the safety relief valve shows a number of interesting, yet complicated, features especially when a two-phase flow is involved. Consequently, developing an efficient and accurate means for predicting the safety relief valve performance and understanding the flow physics is a demanding objective. In this article, the ability of a two-phase mixture model to predict the critical flows of air and water through a safety valve is examined. An industrial refrigeration safety relief valve of ¼” inlet bore size has been tested experimentally over a pressure range of 6–15 barg and air mass qualities from 0.23 to 1 when discharging to near atmospheric conditions for a range of valve lift positions. A two-dimensional mixture model consisting of mixture mass, momentum and energy equations, combined with a liquid mass equation and the standard k-e turbulence model for mixture turbulent transport has been used to predict the two-phase flows though the valve. The mixture model results have been compared with the homogenous equilibrium model and the homogenous non-equilibrium model adopted by the ISO standard. It has been shown that the mixture model can be used satisfactorily to predict the mass flows for the above conditions. Overall, the accuracy of the two-phase air mass flow for given inlet liquid flow rates can be predicted to within 15%

Two-phase discharge flow prediction in safety valves

Safety Relief Valves (SRV) are necessary elements in the protection of any pressurised system and the prediction of the expected discharge flows is an important consideration for the valve sizing to ensure that rupture pressures do not occur. The high speed flows that occur inside the SRV are complex particularly when a two-phase flow is involved and lead to a less capable protection device which result in larger valves compared to single phase flows. In this paper the ability of a CFD based two phase mixture model to predict the critical flows of air and water through a safety valve is examined. An industrial refrigeration safety relief valve of ¼” inlet bore size has been tested experimentally over a pressure range of 6-15 barg and air mass qualities from 0.1-1 when discharging to near atmospheric conditions for a fully open condition. A two-dimensional mixture model consisting of mixture mass, momentum, and energy equations, combined with a liquid mass equation and the standard k- ε turbulence model for mixture turbulent transport has been used to predict the two phase flows through the valve. The mixture model results have been compared with the Homogenous Equilibrium Model (HEM) commonly used for in valve sizing in non flashing two phase flow conditions. The accuracy of the models over the two phase flow range are quantified and discussed

Bubble formation at two adjacent submerged orifices in inviscid fluids

A theoretical model has been developed as an extension of single orifice bubble formation to investigate the growth and detachment of vapor/gas bubbles formed at two adjacent submerged orifices in inviscid fluids. The mathematical model treats the two bubbles as an expanding control volume moving to the line of centers above a wall. The movement of the bubbles is obtained by application of force balance acting on the bubble and accounts for surface tension, buoyancy, steam momentum and liquid inertia effects. The liquid inertia effects are determined by applying inviscid and irrotational flow assumptions to allow potential flow theory to calculate the liquid velocity field which then allows the pressure distribution to be calculated. The model is extended to include the mass and energy equations to model the steam bubble formation in sub-cooled water. The theoretical results are compared with the available experimental data of bubble formation during constant mass flow steam bubble formation at two submerged upward facing orifices in sub-cooled water. The model was validated by available experimental data for the growth and detachment processes of two adjacent 1 mm orifices at system pressures of 2 and 3 bars, flow rates of 1.2-4 g/min at sub-cooling of 3.5-35 ºC. The comparisons of theory and experiments indicate that the model successfully predicts the bubbles growth and detachment for the range of conditions studied

The use of interactive multi-player games to enhance second language acquisition of both Mandarin and English

MMORPG have become a popular area of language acquisition research, raising the question of whether games and education can be effectively combined to create a game based on research that has education within its core yet still presents as an engaging gaming experience and provides a mutual learning platform for two languages. The current study is longitudinal and focuses on the question: Can interactive RPGs enhance second language acquisition? <br/

RPGs to enhance the second language acquisition of both Mandarin and English

Research Question: “To what degree can it be evidenced that interactive role playing games enhance the mutual second language acquisition of both Mandarin and English?”♦ Small scale side project to ascertain avatar interaction preferences based on perception.♦ Pilot study will apply psycholinguistic and sociolinguistic research knowledge to specifically designed game

Innovative strategies for 3D visualisation using photogrammetry and 3D scanning for mobile phones

3D model generation through Photogrammetry is a modern overlay of digital information representing real world objects in a virtual world. The immediate scope of this study aims at generating 3D models using imagery and overcoming the challenge of acquiring accurate 3D meshes. This research aims to achieve optimised ways to document raw 3D representations of real life objects and then converting them into retopologised, textured usable data through mobile phones. Augmented Reality (AR) is a projected combination of real and virtual objects. A lot of work is done to create market dependant AR applications so customers can view products before purchasing them. The need is to develop a product independent photogrammetry to AR pipeline which is freely available to create independent 3D Augmented models. Although for the particulars of this research paper, the aim would be to compare and analyse different open source SDK’s and libraries for developing optimised 3D Mesh using Photogrammetry/3D Scanning which will contribute as a main skeleton to the 3D-AR pipeline. Natural disasters, global political crisis, terrorist attacks and other catastrophes have led researchers worldwide to capture monuments using photogrammetry and laser scans. Some of these objects of “global importance” are processed by companies including CyArk (Cyber Archives) and UNESCO’s World Heritage Centre, who work against time to preserve these historical monuments, before they are damaged or in some cases completely destroyed. The need is to question the significance of preserving objects and monuments which might be of value locally to a city or town. What is done to preserve those objects? This research would develop pipelines for collecting and processing 3D data so the local communities could contribute towards restoring endangered sites and objects using their smartphones and making these objects available to be viewed in location based AR. There exist some companies which charge relatively large amounts of money for local scanning projects. This research would contribute as a non-profitable project which could be later used in school curriculums, visitor attractions and historical preservation organisations all over the globe at no cost. The scope isn’t limited to furniture, museums or marketing, but could be used for personal digital archiving as well. This research will capture and process virtual objects using Mobile Phones comparing methodologies used in Computer Vision design from data conversion on Mobile phones to 3D generation, texturing and retopologising. The outcomes of this research will be used as input for generating AR which is application independent of any industry or product

Transient thermal analysis of a data centre cooling system under fault conditions

Data centres housing the IT infrastructure of large organisations constitute a considerable technical challenge to ensure 100% operational availability for mission critical IT systems. Specifying plant cooling systems to maintain suitable temperature levels and dissipate the heat generated can be carried out using industry standard design methods. However, accounting for perturbations in cooling due to failure of plant and restart of backup systems requires for faster thermal transients to be addressed than would normally be encountered in building system analysis. It is in this context that this paper describes the modelling and analysis of a 5 MW chilled water cooling system used for the cooling of a recently constructed UK data centre. The model has been developed using the TRNSYS software and includes a full model of the energy transfers for the data centre including chillers, hydraulic network, valve models and each of the 70 Room Air Conditioning Units. The coupling between the data centre air temperature levels and the cooler system has enabled a full assessment of the cooling system design in response to system perturbations. A number of scenarios are examined involving the failure of the chillers and how the inherent thermal inertia of the system plus additional inertia achieved through buffer vessels allowed a suitable design to be achieved. The detailed transient analysis model allowed the sizing of these vessels effectively and to gain a better understanding of the chilled water plant operation, both in normal conditions and in the case of failure

Massive Higher Spin Fields Coupled to a Scalar: Aspects of Interaction and Causality

We consider in detail the most general cubic Lagrangian which describes an interaction between two identical higher spin fieldsin a triplet formulation with a scalar field, all fields having the same values of the mass. After performing the gauge fixing procedure we find that for the case of massive fields the gauge invariance does not guarantee the preservation of the correct number of propagating physical degrees of freedom. In order to get the correct number of degrees of freedom for the massive higher spin field one should impose some additional conditions on parameters of the vertex. Further independent constraints are provided by the causality analysis, indicating that the requirement of causality should be imposed in addition to the requirement of gauge invariance in order to have a consistent propagation of massive higher spin fields.Comment: 34 pages, comments, references and one Appendix added. Typos corrected. Published versio

The origin of Proterozoic massif-type anorthosites: Evidence from interactions between crustal xenoliths and basaltic magma

Plagioclase-rich reaction zones occur around numerous aluminous crustal xenoliths within a suite of Palaeogene sub-volcanic basic sheets on the Isle of Mull, NW Scotland. The xenoliths consist of a glassy core, containing mullite needles, generated from the melting of pelitic source rocks. Thick plagioclase mantles grew at the interface between the aluminous liquid and the enclosing basaltic magma and provide a high-level analogue for the petrogenesis of Proterozoic massif-type anorthosites. Similar interactions between mantle-derived basic magmas ponded at the base of the crust and relatively Al-rich lower crustal lithologies would result in the precipitation of large volumes of plagioclase. Anorthosite massifs were then emplaced at higher crustal levels as crystal-rich mushes within relatively juvenile Proterozoic crust. The model negates the need to crystallize large volumes of mafic minerals prior to the production of plagioclase-saturated liquids, and also accounts for the significant influence of crustal sources on the isotopic signatures of all members of the anorthosite suite