Numerical simulation and optimization of bubbling on float glass furnaces. Part 2: Bubbling optimization and verification

HighlightsA detailed study of the relationship between the velocity distribution, length of tube and nozzle sizes. Rotation speed decreased approximately linearly as the length of the tube increased.Relative error was less than 4% for validated results indicating a perfect correlation between the values of numerical simulation, calculated, and experiment results. Abstract.A detailed study of the relationship between velocity distribution, length of tube and nozzle sizes was conducted using a dynamic fluidic sprinkler. Therefore, the objectives of this article were: (1) to study inner flow characteristics of dynamic fluidic sprinkler, (2) to compare numerical simulation and experimental results (3) to introduce an empirical equation of the variation trend of rotation speed for the newly designed sprinkler. A mathematical model for simulation of the inner flow distribution of the sprinkler was obtained by using computational fluid dynamics. The results were validated by numerical simulation and compared to the experimental results. The minimum average deviation between the calculated, simulation and experiment was 0.25%, whiles the maximum was 0.90%. It was found that the relative error was less than 4% results indicating a perfect correlation between the values of numerical simulation, calculated and experiment results. It was established that the rotation speed decreases approximately linearly as the length of the tube increases. The results revealed that the nozzle diameter, length of the tube, and the operating pressure had a significant influence on the rotation speed of the sprinkler. This study provides baseline information to improve water application efficiency for crop production in sprinkler irrigated fields. Keywords: Dynamic fluidic sprinkler, Inner flow, Nozzle, Numerical simulation, Water saving.

The flames considered are those which maintain vibration of the air in a surrounding “air tube.” Earlier theories are reviewed. Rayleigh's theory involves standing waves in the gas supply tube and leads to certain lengths of gas tube for which singing does not occur. It is now found that maintenance of vibration in the air tube may be excellent when the gas tube is so long that no appreciable standing waves are formed in it, and that under suitable conditions there are no lengths of gas tube for which a flame will not sing. Rayleigh's theory is modified by taking into account (1) the increase in viscosity which the flame brings about in the orifice from which it burns and (2) the progressive waves that run downward through the gas tube. These waves involve a maximum rate of efflux of gas near the phase of least pressure in the air tube, whereas Rayleigh's theory involves a maximum rate of efflux a quarter of a period earlier or later, depending on the length of the gas tube. If the most rapid efflux is near the phase of least pressure, and if the flame gases rise from the orifice to the top of the flame in approximately half a period, maintenance is possible. In thirteen cases where the flame sang, values obtained for the time of rise run from 0.6T to 0.9T; and in sixteen cases where the flame was silent, they run from 1.2T to 3.3T. In view of approximations made in reaching these results they are regarded as satisfactory. When the gas tube is of only moderate length, standing waves in it may be superposed on the running waves. This superposition leads to the possibility of lengths of gas tube for which the flame will not sing. Regions of silence are more likely to occur when the flame is small. The size of the flame is also a factor in determining the distance to which it must be inserted in the air tube before maintenance is possible. The distance is a minimum for flames of moderate size. The amended theory gives explanations of these facts and of several others. The initiation of the vibration is attributed to the slight disturbances that are always present in the atmosphere.

The purpose of the work is forecasting the parameters of a gas collector in goaf according to the results of numerical simulation for handling methane migration from goaf into excavations. The subject of the research is the regularities of a gas collector formation at change of pore volume in rocks under the influence of deformations. To estimate the volume of gas released in goaf numerical simulation of the stress-strain state of the investigated area is performed. Numerical simulation is based on the finite element method with usage of the algorithm developed by the authors and a complex of computer programs. The results of the research are the determination of the shapes and borders of a gas collector, the relative content of methane in partially disintegrated rocks, methane volume in a gas collector. The practical value of the received results consists in possibility of forecasting the parameters of a gas collector at the stage of creation of project documentation for working out the suite of coal layers. According to the results of the research the dependence between the volume of gas arriving in goaf and the ratio of gas concentration in coal and rock is determined.

A detailed study of the relationship between velocity distribution, length of tube and nozzle sizes was conducted using a dynamic fluidic sprinkler. Therefore, the objectives of this chapter were to study (1) inner flow characteristics of dynamic fluidic sprinkler. (2) compare numerical simulation and experimental results (3) to introduce an empirical equation of the variation trend of rotation speed for the newly designed sprinkler. A mathematical model for simulation of the inner flow distribution of the sprinkler was obtained by using computational fluid dynamics. The results were validated by numerical simulation and compared to the experimental results. The results revealed that the nozzle diameter, length of the tube and the operating pressure had a significant influence on the rotation speed of the sprinkler. This study provides baseline information to improve water application efficiency for crop production in sprinkler irrigated fields.KeywordsInner flowNozzlenumerical simulationWater saving

Nowadays it is hard to re-valuate the importance of glass and glass products. Glass is used in construction, medicine, food packaging and chemical industry. As those domains continue to develop, they require even higher quality of glass products. Glass production plant is a complex facility that consists of multiple premises used at various stages of glassmaking: storage, batch preparation, glass melting (glass furnace) and product packaging. Glass furnace is a complex technological object. Chemical and physical transformations in the furnace occur simultaneously along with three types of heat exchange for both gas and liquid media. Glassmaking process is characterized by two interdependent parameters that affect the quality of glass products. An efficient process control system is needed to ensure the uninterrupted operation of a glass furnace at given process conditions in order to reach the desired quality of glass products. Development of the efficient control system is based on experimental data. Collecting of glass furnace data through experiment would certainly lead to unacceptable production losses: either due to production rejects or incidents. Usage of glass furnace model is the only alternative to avoid production losses during glassmaking process control system development. This article is dedicated to creation of glassmaking model by combining models of numerous physical and chemical processes that occur in glass furnace. Among the examined physicochemical phenomena are: fuel burning, glass melt and gas medium hydro- and gas dynamics, glass furnace heat exchange. Glassmaking physical reductions and assumptions, initial and boundary conditions are also described in the paper. Keywords: glass production, mathematical model, system of Navier-Stokes equations, batch melting, the equation of radiative transfer

Numerical investigation and analysis of indoor gas explosion: A case study of “6·13” major gas explosion accident in Hubei Province, China

Storage of wood pellets has resulted in deadly accidents in connection with off‐gassing and self‐heating. A forced ventilation system should be in place to sweep the off‐gases and control the thermal conditions. In this study, multiple purging tests were conducted in a pilot scale silo to evaluate the effectiveness of a purging system and quantify the time and volume of the gas needed to sweep the off‐gases. To identify the degree of mixing, residence time distribution of the tracer gas was also studied experimentally. Large deviations from plug flow suggested strong gas mixing for all superficial velocities. As the velocity increased, the system dispersion number became smaller, which indicated less degree of mixing with increased volume of the purging gas. One‐dimensional modelling and numerical simulation of the off‐gas concentration profile gave the best agreement with the measured gas concentration at the bottom and middle of the silo.

A computational glass furnace model was developed for the glass industry to evaluate the glass furnace performance. GFM simulates the major flow and heat transfer characteristics in both the combustion space and glass melter of the furnace, including fluid mixing, combustion, soot/NO/sub x/ formation and transport, radiation heat transfer, batch melting, and glass flow. A computational fluid dynamics code is used to simulate the combustion space flow including NO/sub x/ formation and transport, and spectral radiation heat transfer from soot, gaseous species, and walls. Major features of the model include the time-integral lumped oxy-fuel combustion model and direct integral solution of spectral radiation transport equation. The furnace model has been validated with experimental data from commercial glass furnaces. Radiation heat transfer in a furnace includes three major components: emission from soot and gaseous species, absorption of these species, and emission/reflection of the surrounding walls. The results of a parametric sensitivity study show that the radiation heat transfer components have significant impacts on the calculation of the gas temperature and NO/sub x/.

Combustion heat is used in glass furnaces to melt sand and cullet (scrap glass) into liquid glass to make products. The glass flow in a melter consists of solid particles of sand/cullet, liquid glass, and bubbles. Bubbles formed in the melting processes due to the glass reactions have strong impacts on glass quality and furnace efficiency. Smaller bubbles entrained in the liquid flow degrade the glass quality. Larger bubbles rise to the top of the melter and form a foam layer that impedes the radiation heat transfer from the combustion space and lowers the furnace efficiency. An Eulerian approach was developed to simulate the bubble flow in a glass melter. The approach divides bubbles into various groups and treats each group of bubbles as a continuum. The mass, momentum, and energy conservation equations of the bubble flow are derived to solve for local bubble properties. The approach was incorporated into a multiphase reacting flow computational fluid dynamics code that simulates overall furnace flows to evaluate the impacts of bubbles on glass quality and furnace efficiency.

in this issue, the paper by Kania et al. ([7][1]) presents measurements and modeling results on the role of nitrogen in the gas exchange processes in the middle ear. The middle ear is a semirigid biological gas pocket that is closed most of the time. External influences, such as changing weather

Optimization of the length and position of the absorber tube in small-scale Linear Fresnel Concentrators

Numerical simulation on flow of ice slurry in horizontal straight tubes was conducted in this paper to improve its transportation characteristics and application. This paper determined the influence of the diameter and length of tubes, the ice packing factors (IPF) and the flow velocity of ice slurry on pressure loss by using numerical simulation, based on two-phase flow and the granular dynamic theory. Furthermore, it was found that the deviation between the simulation results and experimental data could be reduced from 20% to 5% by adjusting the viscosity which was reflected by velocity. This confirmed the reliability of the simulation model. Thus, two mathematical correlations between viscosity and flow velocity were developed eventually. It could also be concluded that future rheological model of ice slurry should be considered in three sections clarified by the flow velocity, which determined the fundamental difference from single-phase fluid.

In industrial arena, there are many solid-liquid two phase flow systems like mixing vessels, glass furnaces, solid-liquid separation equipments, etc. Numerical simulations are promising approach to understand the phenomena. Numerical analyses by the Eulerian-Lagrangian approach were performed in the past studies. The Eulerian-Lagrangian methods were applied to various solid-liquid flow systems without the free surfaces. On the other hand, numerical models which can treat the solid-liquid flows involving free surface were hardly developed so far. Hence, in the current study, we develop a Lagrangian-Lagrangian coupling methods to perform the fast simulation of the solid-liquid flows. The liquid phase were modeled by the Explicit Moving Particle Simulation (E-MPS) method. The E-MPS method can simulate the free surface flows easily. The DEM / E-MPS method was applied to a solid-liquid flow in a pipeline. The simulations were performed by changing the acoustic velocity. The simulation results, namely, the solid particle distribution, pressure and fluid velocity were compared in the present study. The DEM / E-MPS method is shown to make possible to perform the fast simulation by assuaging the acoustic velocity.

The zero-gravity problems of a liquid volume sealing a circular tube of gas and a gaseous volume in a circular tube of liquid both involve one phase obstructing another. The two problems differ only in contact angle. From pulmonary research there is a history of axisymmetric analyses for liquid droplets in circular tubes of gas. These analyses consider only axisymmetric solutions—an annulus and an axisymmetric plug. Only recently have nonsymmetric solutions for nonzero contact angle wetting liquids (0°–90° contact angle) been realized by the authors with the use of the Surface Evolver code. Similar to the problem of droplets in a gas filled tube, a bubble in a liquid-filled tube is of interest to the commercial satellite industry and in vascular physiology. Further analysis by the authors now fills in the other half of contact angle range, i.e., either a nonwetting liquid in a tube of gas (contact angles of 90°–180°), or equivalently, a gaseous bubble in a liquid that wets the tube wall. Conditions for the existence and stability of solutions of three topologies are examined.

This paper investigated the flow and heat transfer characteristics of supercritical carbon dioxide (SC-CO2) and supercritical water (SC-H2O) in horizontal micro-channels using a CFD approach. Model of a straight circular pipe of stainless steel with internal and external radii of , respectively, and a heated length of 55 mm was considered. For the simulation, carbon dioxide and water at supercritical pressures of 9.5 MPa and 22.07 MPa respectively were used, while uniform heat was applied on the outer surface of the tube. The thermodynamics properties for both fluids were obtained from the NIST Chemistry Web book. The simulated temperature and heat transfer coefficient variation were compared with experimental results from literature. In general, the simulation results were close to the experiment. Both the simulation and experimental results showed that the wall temperature increased along the tube length. As expected, the heat transfer coefficient values for both supercritical fluids decreased as the length of the tube. This was due the reason that a maximum and dominant convection heat transfer occurred at the entrance of the heated section of the pipe. The results from this study could assist in decisions regarding the use of supercritical fluids in industries which involve heat transfer.