Dynamics of gas flow between interconnected vessels: Experiments and simulations

The Thermal Radiation Simulator (TRS) at the U.S. Army Ballistic Research Laboratory uses aluminum powder reacting with liquid oxygen to create a large jet like flame. The flame acts as a large thermally radiant wall, exposing targets to a nuclear weapon equivalent. The aluminum powder is driven pneumatically to the combustion chamber from a pressurized containment vessel. Unfortunately the thermal output of the flame oscillates with large amplitude relative to the mean yield. The fluctuating mass flow rate of aluminum powder from the aluminum powder containment vessel seemed the cause of the unstable output. A computer model of the aluminum vessel was constructed to determine the pressure dynamics in the pressure vessel. The aluminum powder was assumed to behave as a Newtonian liquid. The pneumatic fluid was assumed to be an ideal gas. The model concentrated inside the vessel and at the exit. The result was to determine the mass flow rate of aluminum from the exit given the inlet gas pressures. The model did reveal the source of mass flow fluctuations not to be caused directly by the existing pneumatic set-up. The variation was shown to be perturbated by forces outside the pressure vessel. Once the outside influence was eliminated, the model showed a clean mean flow rate of aluminum powder. The results were applied to the TRS and the thermal output was stabilized.

Quasi-static pressure is important for the design of explosion containment vessels. Experiments of the spherical vessel under blast loading, in which the quasi-static pressure was measured by the pressure sensors of two different installations, i.e. flush installation and guide-hole installation, were carried out. The data obtained by the pressure sensors are consistent with each other. Based on the formula form derived theoretically, the empirical formula was obtained by fitting the data. The main results are as follows:(1) the pressure in the vessel goes into quasi-static state after the blast wave reflects back and forth three times in the vessel; (2) the quasi-static pressure in the spherical vessel is proportional to the explosion equivalent-to-vessel volume ratio, and the empirical coefficient is 1.10 MPa·m3/kg TNT.

Optimal gas-power flow (OGPF) is one of the most fundamental problems for the operation of integrated electric-gas systems (IEGSs), where the gas flow dynamics partial differential equations (PDEs) are computational challenging. This paper aims to propose a lightweight and accurate model for gas flow dynamics for the OGPF problem. Firstly, the second-order hyperbolic PDEs are equivalently derived based on the original PDEs. Then, the second-order hyperbolic PDEs are discretized using the tri-layer explicit difference scheme. Given some mild boundary and initial conditions, the time-domain two-port model for gas flow dynamics is established, where the state variables of the in-between segments of the pipeline are eliminated. Finally, the iterative parameter updating procedure is devised to improve the modeling accuracy. The lightweight feature of the proposed gas flow dynamics model is verified by the simulation results of several test systems.

Solar collectors with surface receivers have low overall energy conversion efficiencies due to large emissive losses at high temperatures. Alternatively, volumetric receivers promise increased performance because solar radiation can be transferred into a fluid medium, which subsequently reduces the concentrated heat at the surface. Nanofluid-based direct solar receivers, where nanoparticles in a liquid medium can scatter and absorb solar radiation, have recently received interest to efficiently distribute and store the thermal energy. We present a combined modeling and experimental study to investigate the efficiency of fluid-based solar receivers seeded with carbon-coated absorbing nanoparticles. A simple one-dimensional transient heat transfer model was developed to compare idealized surface receivers to idealized volumetric receivers. In the limit of idealized behavior, volumetric receivers were shown to be more efficient than selective-surfaces for high concentration levels (C > 100) and/or tall receiver designs (H > 10 cm). Furthermore, volumetric receivers allowed the working range of the fluid to be extended to higher temperatures while maintaining relatively high receiver efficiency. We also designed and custom built a cylindrical receiver to experimentally demonstrate the concept of nanofluid-based receivers and validate the modeling efforts. We explored the effect of particle characteristics such as size, distribution, and material properties, as well as collector parameters such as absorbing depth and level of solar concentration. The work offers design guidelines for the development of efficient volumetric receivers for future solar thermal energy conversion systems.

Rapid Freeze Prototyping (RFP) builds ice parts by depositing and freezing water in a layer-by-layer manner. This paper presents a one-dimensional transient heat transfer model for a thin ice wall built by the RFP process. Closed-form solutions for temperatures of the ice wall during solidification of a layer of water are derived, which can be used to estimate the solidification time. Natural cooling of the ice wall after solidification of a water layer is also studied. The analytical solutions of heating and cooling of the ice wall agree well with both numerical and experimental results.

This article evaluates the impact of effective sky temperatures on building radiation exchange under clear, cloudy, and dusty conditions for extremely hot and dry climates. In part, a dusty sky temperature model has been introduced as a function of atmospheric aerosol optical depth. The sky radiative exchange was evaluated using a one-dimensional transient heat transfer model with numerical calculations performed using the fully implicit finite-difference method. The newly available ASHRAE 2013 clear sky model was evaluated and implemented to calculate the hourly incident solar radiation for a horizontal roof under the extremely hot–dry climate conditions of Riyadh, Saudi Arabia. Results showed that in clear sky conditions, sky longwave radiation contributes to a reduction of the total heat gain. A daily mean clear sky cooling around 2645 and 2385 W-hr/m2 was estimated for July and January, respectively. In contrast, cloud and dust covers increase effective sky temperature and diminish the role of sky radiative cooling. Depending on severity, the mean contributed sky cooling heat exchange was found to range between 436 and 1636 W-hr/m2 for dust storm and scattered cloudy sky conditions, respectively. Similarly, the ASHRAE 2013 clear sky model and the sky temperature models were shown for four other extremely hot–dry global sites.

A combined numerical and experimental study on graphene/ionic liquid nanofluid based direct absorption solar collector

Optimization of nanofluid volumetric receivers for solar thermal energy conversion

When building physics simulations are done initial conditions express the actual hygrothermal state of building envelope. For the temperature field simulations initial condition is represented by the initial temperature in the body profile at the start of heat transfer. In-structure temperature varies quickly so temperature initial conditions are often neglected. Nevertheless in specific cases initial conditions have to be taken into an account even when simple temperature field simulations are done. The contribution shows various temperature initial conditions determination for insulated construction of outdoor test cell. Comparison of measured and calculated temperature profiles in structure shows correctness of start-up pre-calculation initial condition consideration

Cold neutral gas density has important consequences for the energy and particle balances of the hot ion plasma in the end cells of tandem mirrors. Charge exchange loss from cold gas penetration into this plasma detracts from the pressure in the end cells needed for magnetohydrodynamic stability of the mirror. Unfortunately, cold gas can be a by-product of neutral beam injection and of fueling. This report describes measurements of neutral pressure in the rf heated tandem mirror Phaedrus. The emphasis is on the dynamics of gas flow into the end cells, the effects of cold gas on the plasma, and on wall reflux for different wall conditions. The effects of neutral beams and neutral beam generated wall reflux are also studied. A numerical gas flow code is used to model the effects of plasma pumping, charge exchange, and wall reflux on end cell plasma parameters. The titanium sticking coefficient for hydrogen gas was determined to be 0.08±0.08. Wall reflux coefficients in the end cell were determined to be 1.4±0.2 without titanium gettering and 0.75±0.25 with gettering.

This paper presents an advanced and integrated research approach to longwall mining-induced strata movement, stress changes, fractures, and gas flow dynamics with actual examples of its application from recent studies for co-extraction of coal and methane development at Huainan Mining Group in China, in a deep and multi-seam mining environment. The advanced approach takes advantage of the latest techniques in Australia for mine scale geotechnical characterisation, field measurement, monitoring and numerical modelling. Key techniques described in this paper include coal mine site 3D geotechnical characterisation methods, surface deep downhole multi-point extensometers and piezometers for overburden displacement and pore pressure measurements during mining, tracer gas tests for goaf gas flow patterns, and advanced numerical modelling codes for coupled coal mine strata, water and gas simulations, and longwall goaf gas flow investigations. This integrated approach has resulted in significant insights into the complex dynamic interaction between strata, groundwater, and gas during mining at Huainan Mining Group in recent years. Based on the findings from the extensive field monitoring and numerical modelling studies, a three-dimensional annular-shaped overlying zone along the perimeter of the longwall panel was identified for optimal methane drainage during mining.

The Nd-Yag laser percussion drilling process has been used to process nickel-based superalloys in many aerospace applications. It is shown that variations in hole geometry occur during the processing of accurately-machined components. A typical application for the work presented here involved the percussion drilling of thousands of closely-spaced small (approximately 0.4 mm diameter) holes in a given component. The geometry of the laser-drilled holes has been characterised and quantified by means of a high speed vision system. It has, therefore, been possible to carry out a consistent analysis of the geometry of such holes and quantify any variations in the measured geometries. The observed variations are dependent on such variables as laser power, focal position and gas flow dynamics. This paper discusses the statistical analysis of these variations. The paper shows how statistically-determined control limits can be established for individual process variables in order to achieve specific drilling capabilities and how the results can be applied to maintain control and consistency for the percussion drilling process.The Nd-Yag laser percussion drilling process has been used to process nickel-based superalloys in many aerospace applications. It is shown that variations in hole geometry occur during the processing of accurately-machined components. A typical application for the work presented here involved the percussion drilling of thousands of closely-spaced small (approximately 0.4 mm diameter) holes in a given component. The geometry of the laser-drilled holes has been characterised and quantified by means of a high speed vision system. It has, therefore, been possible to carry out a consistent analysis of the geometry of such holes and quantify any variations in the measured geometries. The observed variations are dependent on such variables as laser power, focal position and gas flow dynamics. This paper discusses the statistical analysis of these variations. The paper shows how statistically-determined control limits can be established for individual process variables in order to achieve specific drilling capabi...

Aradiation-proof superhero could make sense of Japan's Fukushima Daiichi nuclear power plant in an afternoon. Our champion would pick through the rubble to reactor 1, slosh through the pooled water inside the building, lift the massive steel dome of the protective containment vessel, and peek into the pressure vessel that holds the nuclear fuel. A dive to the bottom would reveal the debris of the meltdown: a hardened blob of metals with fat strands of radioactive goop dripping through holes in the pressure vessel to the floor of the containment vessel below. Then, with a clear understanding of the situation, the superhero could figure out how to clean up this mess.

8 5 6 2 0 5 8 5 5 ? 5 : tion of the HRT is summarized. The design of some reactor components is described, including fuel system line coolers, the thermal shield, instrument cubicles, the reactor cell air monitor, and sampling facilities. The important design specifications for the HRT fissionproduct adsorption system are outlined. The effects of fluid circulation on HRT stability, the results of the rupture of the fuel inlet nozzle on the pressure vessel, core tank temperature, and heat generation and temperature distribution in the control room area shield were examined. Operation of the HRT mockup loop is summarized. High generalized corrosion rates and U precipitation were observed when 50 ppm oxygen was used. Results from tests of HRT pumps, heat exchanger, sampler mockup, and reflex condenser and recombiner are presented. Design of the instrumentation in the control room area and fabrication of differential pressure and liquid level transmitters are reported. Thorium Breeder Reactor. Stability criteria, the effect of slurry settling on reactivity, and neutron losses due to coating the core tank with platinum bave been analyzed for the TBR. An economic study of partial fuel costs for one-region Pu-U reactors was completed. The design concept of a 300- electrical-Mw thorium breeder power station utilizing low-pressure gas recombination was completed, and construction and operating costs were estimated. Design problems which must be solved before the design can be considered practical are discussed. Medification of TBR design from low- to high-pressure recombination was started. Corrosion. Operation of dynamic-corroslon test loops with uranyl sulfate solutions and thorium oxide slurries proceeded in a routine manner, and results are presented tabularly. Sedimentation characteristics of thorium dioxide slurries were determined at 100 to 300 deg C. Development, fabrication, and operation of in-side loops for radiation corrosion studies are described. Data from in-side loop and bomb experiments to study the corrosion of Zircaloy-2 and stainless steel under irradiation are reported. Results are presented from laboratory corrosion studies of stressed and unstressed specimens of stainless steel, titanium alloy and Zlrcaloy-2, and unstressed specimens of aluminum oxide in simulated HRT solutions. The effects of sulfate additions, calcination temperature, and particle size on the corrosive effects of thorium oxide slurries were studied. Engneering Development. The status of the heat exchanger development program is summarized. Thorium oxide slurry circulation studies and the development of blanket-system components such as dump tanks and pressurizer are continuing. The power removal capabilities of boiling homogeneous reactors are being studied. The results of stress-corrosion tests on austenitic stainless steels and dynamiccorrosion tests of stainless steel welds are reported. The mechanical properties of irradiated Zircaloy-2, stainless steel, and carbon steel specimens are being studied. Chemical Engineering Development. Studies to determine the effect of irradiation on the properties of thorium oxide slurries and to demonstrate slurry radiation stability were continued. Silver was shown to be a good internal catalyst for the recombination of radiolytic gases in thorium oxide slurries. Progress was made in the characterization of thorium oxide preducts and slurries by x-ray, nitrogen adsorption surface area, thermogravimetric, and gaseous adsorption techniques, sedimentation particle size analyses, and bulk density measurements. The HRT fuel processing plant is described. The precipitation of needymium sulfate from

Spherical pressure vessels are used to fully contain the effects of high explosions. In this paper, the vibrations of a spherical containment vessel undergoing elastic response are investigated. Vibration modes of containment vessels are of particular interest, as it is the superposition and interaction of different modes of response with closely spaced frequencies that has been reported to be the mechanism of ‘strain growth’. First, the modal frequencies of a spherical shell for both axisymmetric and nonaxisymmetric response modes are discussed, based on a sequence of papers that have appeared in the open literature. Analytical predictions are then compared with numerical simulations using ABAQUS. It is found that the numerical simulations accurately predict both the axisymmetric and nonaxisymmetric modal frequencies for the complete spherical shell. Next, numerical simulations of modal frequencies for the more complex spherical containment vessel (with nozzles) are compared with the spherical shell results. Numerical simulations for the spherical containment vessel reveal that frequencies are somewhat similar to the complete spherical shell. Limited comparisons with experimentally recorded frequencies for participating modes of vessel dynamic response during high explosive containment testing are presented as well.