Numerical Investigation of Heat Transfer in a Forced Flow of He II

In this paper, we use the complete two-fluid model to simulate transient heat transfer for a forced flow of He II at high Reynolds number following the setup of the experiments performed by Fuzier, S. and Van Sciver, S., “Experimental measurements and modeling of transient heat transfer in forced flow of He II at high velocities,” Cryogenics, 48(3–4), pp. 130 – 137, (2008). A particular attention has been paid to the heat increase due to forced flow without external warming. The simulation are performed using HellFOAM , the helium superfluid simulator based on the OpenFOAM technology. Simulations results are then compared to the experimental data

Numerical Investigation of Thermal Counterflow of He II Past Cylinders

We investigate numerically, for the first time, the thermal counterflow of superfluid helium past a cylinder by solving with a finite volume method the complete so-called two-fluid model. In agreement with existing experimental results, we obtain symmetrical eddies both up- and downstream of the obstacle. The generation of these eddies is a complex transient phenomenon that involves the friction of the normal fluid component with the solid walls and the mutual friction between the superfluid and normal components. Implications for flow in a more realistic porous medium are also investigated

Large space structures and systems in the space station era: A bibliography with indexes

Bibliographies and abstracts are listed for 1372 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1990 and June 30, 1990. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

Large space structures and systems in the space station era: A bibliography with indexes (supplement 03)

Bibliographies and abstracts are listed for 1221 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1991 and June 30, 1991. Topics covered include large space structures and systems, space stations, extravehicular activity, thermal environments and control, tethering, spacecraft power supplies, structural concepts and control systems, electronics, advanced materials, propulsion, policies and international cooperation, vibration and dynamic controls, robotics and remote operations, data and communication systems, electric power generation, space commercialization, orbital transfer, and human factors engineering

Design and Analysis of Pulse Tube Refrigerator

After decades of rapid development, the absence of moving parts in the cold head, low vibration, long lifetime and high reliability, pulse tube refrigerators are the most promising cryo-coolers. Because of these momentous advantages, they are widely used in Superconducting Quantum Interference Devices (SQUIDs), cooling of infrared sensors, low noise electronic amplifiers, missiles and military helicopters, superconducting magnets, liquefaction of gases, gamma ray spectrometers, liquefaction of gases, X-ray devices and high temperature superconductors etc. It has also got wide applications in preservation of live biological materials as well as in scientific equipment. It is essential to accurate modelling of the pulse tube cryocooler and predicts its performance, thereby arrive at optimum design. At the current stage of worldwide research, such accurate models are not readily available in open literature. Further, the complexity of the periodic flow in the PTR makes analysis difficult. Although different models are available to simulate pulse tube cryocoolers, the models have its limitations and also range of applicability. In order to accurately predict and improve the performance of the PTR system a reasonably thorough understanding of the thermos fluid- process in the system is required. One way to understand the processes is by numerically solving the continuum governing equations based on fundamental principles, without making arbitrary simplified assumptions. The recent availability of powerful computational fluid dynamics (CFD) software that is capable of rigorously modelling of transient and multidimensional flow and heat transfer process in complexgeometries provides a good opportunity for analysis of PTRs. Performance evaluation and parametric studies of an Inertance tube pulse tube refrigerator (ITPTR) and an orifice pulse tube refrigerator (OPTR) are carried out. The integrated model consists of individual models of the components, namely, the compressor, after cooler, regenerator, cold heat exchanger, pulse tube, warm heat exchanger, inertance tube or orifice, and the reservoir. In the first part of the study, the commercial CFD package, FLUENT is used for investigating the transport phenomenon inside the ITPTR. The local thermal equilibrium and thermal non-equilibrium of the gas and the matrix is taken into account for the modelling of porous zones and the results are compared. The focus of the second part of the study is to establish the most important geometrical dimension and operating parameters that contribute to the performance of ITPTR and OPTR. The numerical investigation procedure for these investigations is conducted according to the Response surface methodology (RSM) and the results are statistically evaluated using analysis of variance method. Finally a multi-objective evolutionary algorithm is used to optimize the parameters and for an optimized case the phasor diagram is discussed

Magnetic fields in neutron stars

This work aims at studying how magnetic fields affect the observational properties and the long-term evolution of isolated neutron stars, which are the strongest magnets in the universe. The extreme physical conditions met inside these astronomical sources complicate their theoretical study, but, thanks to the increasing wealth of radio and X-ray data, great advances have been made over the last years. A neutron star is surrounded by magnetized plasma, the so-called magnetosphere. Modeling its global configuration is important to understand the observational properties of the most magnetized neutron stars, magnetars. On the other hand, magnetic fields in the interior are thought to evolve on long time-scales, from thousands to millions of years. The magnetic evolution is coupled to the thermal one, which has been the subject of study in the last decades. An important part of this thesis presents the state-of-the-art of the magneto-thermal evolution models of neutron stars during the first million of years, studied by means of detailed simulations. The numerical code here described is the first one to consistently consider the coupling of magnetic field and temperature, with the inclusion of both the Ohmic dissipation and the Hall drift in the crust.Comment: PhD thesis defended in University of Alicante, 20 September 201

Coupled geomechanics and transient multiphase flow at fracture-matrix interface in tight reservoirs.

Fractured hydrocarbon reservoirs play a significant role in the world economy and energy markets. Fluid injection (normally water) forces the hydrocarbons out of the reservoirs. Geomechanics, externally applied stress on the rock, play a significant role in the oil recovery from fractured reservoirs. Subsurface fluid injection modifies pore pressure and in-situ stresses locally. In response to the pressure/stress combined effects, the pores and fracture regions undergo deformation. Similarly, it is a well-known fact that pore volume significantly impacts the absolute and relative permeability of fractured tight reservoirs. The governing factors that characterize multiphase fluid flow mechanisms in naturally-fractured tight reservoirs - such as wellbore stability, CO2 sequestration and improved hydrocarbon recovery - are relative permeability and capillary pressure. Although the effects of geomechanical parameters on single-phase fluid flow in naturally-fractured tight reservoirs are well documented, the interdependence between geomechanical and multiphase flows are severely lacking. This study aims to bridge this knowledge gap using advanced numerical techniques, focusing on accurately capturing complex flow phenomena at the fracture-matrix interface to enhance the accuracy of predicting oil recovery from naturally-fractured tight reservoirs, leading towards more efficient operations and reduced costs. Extensive sets of numerical investigations have been carried out in the present study, using an advanced Computational Fluid Dynamics (CFD) solver, to accurately capture transient multiphase flow (oil and water) phenomena within naturally-fractured tight reservoirs. Special attention has been paid towards accurate multiphase flow modelling and characterisation at the fracture-matrix interface. The numerical models have been validated against Berea Sandstone experimental data. Two separate numerical models have been developed with the aim to identify the most appropriate modelling technique for accurate numerical predictions of multiphase flow in naturally-fractured tight reservoirs. These two models are based on duct flow theory and flow through porous medium theory, respectively, while the Brooks and Corey method has been utilised to compute fluid saturation, relative permeability and capillary pressure at the fracture-matrix interface. The results obtained show that the difference between the numerical and experimental results is 30% when duct flow model is considered, while it is 2.57% when porous medium is considered. In order to critically evaluate the dependence of multiphase flow on the geomechanical parameters of naturally-fractured tight reservoirs, a one-way FEACFD coupling scheme has been implemented in the present study, not taking into consideration the pore pressure. The effects of externally applied stress loading on the geomechanical (porosity and fracture aperture) and multiphase flow characteristics (permeability, capillary pressure, relative permeability and fluid saturation) at the fracture-matrix interface have been thoroughly analysed. For accurate modelling and numerical predictions in naturally-fractured tight reservoirs, a viscous loss term has been incorporated in the momentum-conservation equations. The numerical predictions from the one-way coupled model matches well with Clashach core flooding experimental data, with 9% average difference between the two. The results obtained clearly indicate that external stress loading has significant impact on the geomechanical and multiphase flow characteristics at the fracture-matrix interface. Finally, a novel numerical model has been developed based on the full coupling scheme, with the aim to enhance the accuracy of the numerical predictions regarding oil recovery from naturally-fractured tight reservoirs for efficient and cost effective operations. The porous elasticity interface is coupled with multiphase flow in porous media where the mass conservation of each phase, and an extended Darcy's equation, underpin multiphase flow characteristics. The fully coupled model takes into consideration the pore pressure and has been validated against Clashach core flooding experimental data. The developed model has been shown to significantly enhance the prediction accuracy from 9%, for one-way coupled model, to 4%, and has the ability to capture complex multiphase flow phenomena at the fracture-matrix interface. Moreover, the novel model accurately predicts the effects of geomechanical parameters on multiphase flow characteristics. It is envisaged that the novel fully coupled model developed in this study will pave the way for future scientific research in the area of geomechanical-fluid flow coupling for enhanced oil recovery in naturally-fractured tight reservoirs

Bibliography of Lewis Research Center technical publications announced in 1992

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1992. All the publications were announced in the 1992 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses

Nuclear Fusion Programme: Annual Report of the Association Karlsruhe Institute of Technology (KIT)/EURATOM ; January 2010 - December 2010 (KIT Scientific Reports ; 7592)

The Karlsruhe Institute of Technology (KIT) is working in the framework of the European Fusion Programme on key technologies in the areas of superconducting magnets, microwave heating systems (Electron-Cyclotron-Resonance-Heating, ECRH), the deuterium-tritium fuel cycle, He-cooled breeding blankets, a He-cooled divertor and structural materials, as well as refractory metals for high heat flux applications including a major participation in the preparation of the international IFMIF project