Gas Circulation Research Articles

Energy and Productivity Yield Assessment of a Traditional Furnace for Noncentrifugal Brown Sugar (Panela) Production

Noncentrifugal brown sugar (called panela in Colombia) is a natural sweetener obtained from the extraction, purification, and concentration of sugarcane juices. In this work, energy and productivity yield of a traditional furnace for panela production were evaluated, considering five performance indices. Experimental productions were developed in a pilot plant facility, analyzing furnace gas emissions of furnace and bagasse properties. Mass, energy, and exergy balances were performed. The following indices were obtained from the experimental runs: energy efficiency 12.726 ± 1.091%, exergy efficiency 9.013 ± 0.710%, energy losses through chimney 72.293 ± 11.507%, yield 0.144 ± 0.021 kgpanela/kgbagasse, productivity 7.450 ± 0.520 kgpanela/h, and bagasse consumption 1.258 ± 0.139 kgbagasse consumed/kgbagasse produced. It was found that these outcomes were strongly influenced by excess air and gas circulation velocity through the furnace, which affects the combustion rate and heat transfer between the gases and the juices. Finally, it was concluded that the traditional scheme is inefficient and requires various critical operational adjustments, such as combustion chamber, chimney draft control, and heat exchangers design.

Analysis of continuous wave diode pumped cesium laser with gas circulation: experimental and theoretical studies.

Analysis of the operation of flowing-gas low power DPALs is crucial for designing high power devices. In particular, the comparison between the measured and calculated temperature rise in the laser cell makes it possible to estimate the contribution of the quenching of the alkali atoms electronic states to the gas heating. Here we report on an experimental and theoretical study of continuous wave flowing-gas Cs DPAL with He and CH4 buffer gases, flow velocities of 1-4 m/s and pump powers of 30-65 W. In the calculations we used a 3D computational fluid dynamics model, solving the fluid mechanics and kinetics equations relevant to the laser operation. Maximum CW output power of 24 W with a slope efficiency of 48% was obtained. The experimental and theoretical values of the power and gas temperature are in good agreement. The lasing power was not affected by the flow velocity at this range of pump power and the gas temperature rise was only several degrees. It was found that the best agreement between the measured and calculated temperature rise is achieved for quenching cross-section ~0.05 Å2.

Methane hydrate formation in mixed-size porous media with gas circulation: Effects of sediment properties on gas consumption, hydrate saturation and rate constant

Being a promising potential source for natural gas, methane hydrate (MH) is attracting increasing interest due to its great amount and diverse geographic distribution. The formation of MH is significantly influenced by the properties of sediment media such as porosity and permeability. In this study, in order to have a better understanding on the relationship between MH formation behavior and sediment properties, as well as to synthesize representative hydrate samples, MH was formed in six different sets of mixed-size porous media composed of clay, silt and fine sand, with saline water and circulating methane gas to reflect MH formation with free methane flux in marine sediment. The sediment composition, experimental pressure (15 MPa) and temperature (286.2 K) were chosen based on the SH2 drilling site in the Shenhu area in South China Sea. A two-stage growing behavior was observed for all systems. The gas consumption and hydrate formation rate exhibited positive relations with the permeability and porosity of the sediments. Furthermore, hydrates were found to be preferably formed in the bottom layer of the sediment, which could be attributed to the drastic drop of permeability at the early stage of hydrate formation. Lastly, the hydrate formation rate constant was calculated based on the intrinsic kinetic model and found to be a good reflection of the mass transfer properties of different porous media.

Wind energy harvester based on coaxial rotatory freestanding triboelectric nanogenerators for self-powered water splitting

Electrolysis of water is utilized as an environment friendly approach for production of hydrogen (H2). An external power supply for driving the oxidation or reduction reactions of H2O molecules is mandatory for electrolysis. Harvesting energy from our living environment for electrolytic water splitting is a cost-effective technology for mass production of H2. Here, a coaxial rotatory freestanding triboelectric nanogenerator (CRF-TENG) wind energy harvester was demonstrated, in which the electrospinning PVDF nanofibrous membrane served as triboelectric material. And then a fully self-powered water splitting system for hydrogen production was presented based on the CRF-TENG. By scavenging ambient wind energy, the generated electricity is used for water splitting to produce H2, instead of the external power source. The amounts of H2 were measured by a gas circulation system and gas chromatograph and the H2 evolution rates were calculated. When the wind speed is 10 m/s, the hydrogen generation rate reaches 6.9685 μL/min in the 1 M KOH solution, suggesting an easy scale-up and efficient route for converting ambient mechanical energy into hydrogen energy. Such self-powered water splitting system opens up a new road to more energy applications.

ERT monitoring of gas injection into water saturated sands: Modelling and inversion of cross-hole laboratory data

A set of laboratory experiments were performed in order to investigate the capacity of the electrical resistivity tomography method to detect and monitor the circulation of gaseous CO2 into geological media. The experiments consisted of injecting reactive (CO2) or inert (N2) gases into reactive (carbonate) or inert (silica) sands saturated with water. The laboratory setup was a metric-scale cylindrical tank instrumented with electrodes placed on vertical rods, hence simulating a borehole to borehole monitoring network. The results demonstrated that the ERT method can efficiently detect, locate and image gas circulation plumes. Two main behaviors were identified: either an increase of the medium resistivity due to the invasion of the porous space by an electrically insulating gas phase, or a resistivity decrease induced by dissolution processes that enhance ionic concentrations in the saturating water. The observed anomalies showed varying geometric shapes depending on which type of sand was used. A 3D cellular automaton model was built and managed to reproduce different gas plume circulation patterns and the electrical resistivity response associated. This modeling work confirmed the link existing between the shapes of the resistivity anomalies, the gas plume geometry and the particle size distribution of the sand. Through a numerical sensitivity analysis, several measuring protocols were tested and developed in order to improve the imaging capacity of the electrical resistivity method. Results demonstrated that the most efficient protocol was different depending on the shape of the gas plume, thus stressing the importance of having a priori knowledge on the geological, lithological and hydraulic characteristics of the subsurface, in order to correctly assess the most likely gas plume geometry and hence design the most adapted monitoring protocol.

Simulation of start-up behaviour of a passive autocatalytic hydrogen recombiner

Abstract Heterogeneous catalytic recombination of hydrogen with oxygen is one of the methods used to remove hydrogen from the containment of a light-water nuclear reactor (LWR). Inside a passive autocatalytic recombiner (PAR), hydrogen and oxygen molecules are adsorbed at catalyst active spots and they recombine to yield water. Heat released in this exothermic reaction creates natural convection of gas in the spaces between the elements supporting a catalyst. Hot and humid gas flows upwards into the PAR chimney, while fresh, hydrogen-rich gas enters the PAR from below. Catalytic recombination should start spontaneously at room temperature and low hydrogen concentration. Computational fluid dynamics (CFD) has been used to study the dynamic behaviour of a plate-type Areva FR-380 recombiner in a quiescent environment for several test scenarios, including different rates of increase in hydrogen concentration and temporary catalyst deactivation. A method for the determination of pressure boundary conditions at the PAR exits was proposed and implemented into a CFD code. In this way, transient operation of PAR could be simulated without the need to model gas circulation outside the device. It was found that first a slow downward flow of gas is developed, which may persist until the temperature of the catalyst foils rises. As soon as the gas inside the PAR absorbs enough heat to become lighter than the gas outside the PAR, it starts to flow upwards. Criteria for determining the start-up time of PAR were proposed. Model predictions were also compared with experimental data obtained in tests conducted at the THAI facility.

Hydrogen-diesel fuel co-combustion strategies in light duty and heavy duty CI engines

The co-combustion of diesel fuel with H2 presents a promising route to reduce the adverse effects of diesel engine exhaust pollutants on the environment and human health. This paper presents the results of H2-diesel co-combustion experiments carried out on two different research facilities, a light duty and a heavy duty diesel engine. For both engines, H2 was supplied to the engine intake manifold and aspirated with the intake air. H2 concentrations of up to 20% vol/vol and 8% vol/vol were tested in the light duty and heavy duty engines respectively. Exhaust gas circulation (EGR) was also utilised for some of the tests to control exhaust NOx emissions.The results showed NOx emissions increase with increasing H2 in the case of the light duty engine, however, in contrast, for the heavy duty engine NOx emissions were stable/reduced slightly with H2, attributable to lower in-cylinder gas temperatures during diffusion-controlled combustion. CO and particulate emissions were observed to reduce as the intake H2 was increased. For the light duty, H2 was observed to auto-ignite intermittently before diesel fuel injection had started, when the intake H2 concentration was 20% vol/vol. A similar effect was observed in the heavy duty engine at just over 8% H2 concentration.

On the Terminal Rotation Rates of Giant Planets

Abstract Within the general framework of the core-nucleated accretion theory of giant planet formation, the conglomeration of massive gaseous envelopes is facilitated by a transient period of rapid accumulation of nebular material. While the concurrent build-up of angular momentum is expected to leave newly formed planets spinning at near-breakup velocities, Jupiter and Saturn, as well as super-Jovian long-period extrasolar planets, are observed to rotate well below criticality. In this work, we demonstrate that the large luminosity of a young giant planet simultaneously leads to the generation of a strong planetary magnetic field, as well as thermal ionization of the circumplanetary disk. The ensuing magnetic coupling between the planetary interior and the quasi-Keplerian motion of the disk results in efficient braking of planetary rotation, with hydrodynamic circulation of gas within the Hill sphere playing the key role of expelling spin angular momentum to the circumstellar nebula. Our results place early-stage giant planet and stellar rotation within the same evolutionary framework, and motivate further exploration of magnetohydrodynamic phenomena in the context of the final stages of giant planet formation.

Enhanced photocatalytic hydrogen production from water-ethanol solution by Ruthenium doped La-NaTaO3

The photocatalytic hydrogen production from ethanol aqueous solution, with the use ruthenium doped La-NaTaO3 has been investigated. Ruthenium doped La-NaTaO3 catalysts are prepared by impregnation method. The catalysts are by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Ru co-catalyst demonstrated from the TEM image shows a good dispersion on the surface of La-C-NaTaO3 with an average particle size between 4-5 nm. The photocatalytic reaction is carried out in a closed reactor with a gas circulation system. The catalytic activity of La-NaTaO3 improved markedly (6.6 times from pure water) when Ru is loaded onto its surface. The hydrogen production is notably enhanced in the presence of ethanol as electron donors. This result is much higher when compared with the rate of hydrogen production in the sample without co- catalysts about 9.4 times higher after Ru deposition from ethanol aqueous solution. Increasing the production of hydrogen on the Ru/La-NaTaO3 closely related to the decrease in recombination between electron-hole pairs.

Techno-Economic Analysis of a 600 MW Oxy-Enrich Pulverized Coal-Fired Boiler

Oxy-fuel combustion is one of the most promising methods for CO2 capture and storage (CCS) but the operating costs—mainly due to the need for oxygen production—usually lead to an obvious decrease in power generation efficiency. An “oxy-enrich combustion” process was proposed in this study to improve the efficiency of the oxy-fuel combustion process. The oxidizer for oxy-enrich combustion was composed of pure oxygen, air and recycled flue gas. Thus, the CO2 concentration in the flue gas decreased to 30–40%. The PSA (pressure swing adsorption), which has been widely used for CO2 removal from the shifting gases of ammonia synthesis in China, was applied to capture CO2 during oxy-enrich combustion. The technological economics of oxy-enrich combustion with PSA was calculated and compared to that of oxy-fuel combustion. The results indicated that, compared with oxy-fuel combustion: (1) the oxy-enrich combustion has fewer capital and operating costs for the ASU (air separation unit) and the recycle fan; (2) there were fewer changes in the components of the flue gas in a furnace for oxy-enrich combustion between dry and wet flue gas circulation; and (3) as the volume ratio of air and oxygen was 2 or 3, the economics of oxy-enrich combustion with PSA were more advantageous.

Sealed operation, and circulation and purification of gas in the HARPO TPC

HARPO is a time projection chamber (TPC) demonstrator of a gamma-ray telescope and polarimeter in the MeV-GeV range, for a future space mission. We present the evolution of the TPC performance over a five month sealed-mode operation, by the analysis of cosmic-ray data, followed by the fast and complete recovery of the initial gas properties using a lightweight gas circulation and purification system.

Influence of background gas on two-dimensional metal evaporation

The spatial distributions of macroscopic parameters such as density, bulk velocity and temperature of the metal vapor have influences on the photo ionization yield of target isotope and the utilization ratio of material, which is related to the separation efficiency and the cost of atomic vapor laser isotope separation. To study this problem more practically, a system of binary gas Bhatnagar-Gross-Krook (BGK) model equations, which describe both the metal vapor and the background gas, is established. The physical characteristics are dealt with by dimensionless method for simplifying the calculations. The model equations are discretized by one-order upwind difference and then are solved by iteration method for obtaining stable results. The computational grids are adjusted to the flow field in order to acquire modest computational cost and accurate result simultaneously. Non-uniform grids in the phase space and in the velocity space are constructed to match the macroscopic parameter gradient and the form of the velocity distribution, respectively. The macroscopic parameters in the cases of different background gas densities, temperatures of tail plate and absorptivities are obtained for studying the influence of the background gas. The results show that with the increase of density of the background gas, the density and temperature of the metal vapor increase, the bulk velocities in the x and z$ direction decrease obviously in the domain far from the evaporation source, while the macroscopic parameters that are close to the evaporation source hardly change. As a result, the evaporation rate is not affected. Meanwhile, a circulation of the background gas is driven by the metal vapor, which in turn affects the diffusion of the metal vapor. Besides, as the temperature of tailing plate rises, the influence of the background gas on the macroscopic parameters of the metal vapor weakens. However, the rise of the temperature of tail plate leads the absorptivity of metal vapor to decrease, which enlarges the influence of the background gas. Therefore, it is appropriate to adjust the temperature of the tail plate based on the relationship between the absorptivity of metal vapor and the temperature. The results of theoretical calculation can serve as a reference for designing the vacuum and laser spot of the separation device.

Investigation of local gas holdup and bubble dynamics using four-point optical probe technique in a split-cylinder airlift reactor

A four-point optical fiber probe technique was employed in a split-cylinder airlift reactor with an air-water system. Effect of superficial gas velocities- 0.3, 1.0, 2.0, and 2.8 cm/s- was studied on the local gas holdup and bubble dynamic properties namely, bubble passage frequency, interfacial area, bubble chord length, and bubble rise velocity in both the riser and downcomer sections of the reactor. The bubble chord length and bubble velocity in the riser and downcomer followed log-normal distribution and normal distribution respectively. The gas holdup and interfacial area in the riser increased by 900 and 800% for a superficial gas velocity increase from 0.3 to 2.8 cm/s, while those at the top of the downcomer by 500, and 400% for a superficial gas velocity increase from 1.0 to 2.8 cm/s, respectively. At each superficial gas velocity, the bubble passage frequency, gas holdup, and interfacial area did not vary significantly along the axis of the riser. An axial variation in bubble passage frequency, gas holdup, and interfacial area was observed in the downcomer. A correlation for the variation of the gas holdup in the riser was developed based on superficial gas and liquid circulation velocities. The correlation for the gas holdup in the downcomer was developed to account for the axial variation observed.

The cryogenics design of the SuperCDMS SNOLAB experiment

The Super Cryogenic Dark Matter Search (SuperCDMS) experiment is a direct detection dark matter experiment intended for deployment to the SNOLAB underground facility in Ontario, Canada. With a payload of up to 186 germanium and silicon crystal detectors operating below 15 mK, the cryogenic architecture of the experiment is complex. Further, the requirement that the cryostat presents a low radioactive background to the detectors limits the materials and techniques available for construction, and heavily influences the design of the cryogenics system. The resulting thermal architecture is a closed cycle (no liquid cryogen) system, with stages at 50 and 4 K cooled with gas and fluid circulation systems and stages at 1 K, 250 mK and 15 mK cooled by the lower temperature stages of a large, cryogen-free dilution refrigerator.This paper describes the thermal design of the experiment, including details of the cooling systems, mechanical designs and expected performance of the system under operational conditions.

Force cooled quench tanks for the ITER cryogenic system

The toroidal field magnets of ITER contain over 7 tons of helium. Most of the inventory is expelled from the magnets in case of a quench and it needs to be captured in external storage vessels (Quench Tanks). Force cooled technology with external gas circulation was chosen for these vessels in order to optimize their footprint, risks, and costs. This paper outlines the input data, assumptions, and studies performed in order to choose the most appropriate technology for the Quench Tanks. Further studies to demonstrate feasibility and ensure the required performance, as well as some peculiarities of the design and manufacturing of Quench Tanks are also described.

Development of convection in high temperature coil annealing furnaces using rotating cylinder technique

The present study investigates the usage of rotating cylinders to generate gas circulation inside high-temperature coil annealing furnaces during the annealing treatment of grain-oriented electrical steel. This technique has been investigated to reduce temperature differentials (hotspots) within the furnace space, a phenomenon that occurs due to extremely high temperatures, the static nature of the gas inside of the furnace and long operation conditions. Finite volume numerical simulation using ANSYS Fluent was performed to test the validity of the proposed technique. The numerical results showed fluctuations in velocity magnitude of the fluid in comparison with a case when the technique was not employed. This is because of the vortex generation under the effect of the cylinder rotation. The generation of turbulence enhances gas-mixing quality, and thus it would save a great amount of energy required for the process, producing a product with desired magnetic properties at lower cost.

PELAKSANAAN PENGAWASAN DINAS PERINDUSTRIAN DAN PERDAGANGAN KOTA PEKANBARU DALAM PENDISTRIBUSIAN GAS LPG 3 KG DI KOTA PEKANBARU

This research was conducted at the Department of Industry and Trade City Pekanbaru which supervises the distribution of LPG gas 3 Kg, and pengawai Who works at the Department of Industry and Trade Pekanbaru City and LPG gas distributor 3 Kg located in Pekanbaru Town, Marpoyan Damai Sub-district The purpose of this study is to analyze the implementation of supervision of the Office of Industry and Trade Pekanbaru City in the distribution of LPG gas 3 Kg in Pekanbaru City and the inhibiting factors in carrying out supervision of gas distribution LPg 3 Kg in Pekanbaru City. Determination of the number of samples for employees of Pekanbaru City Trade and Distribution Service using sample sensu so that it can be 4 employees, while samples from LPG gas distributor 3 Kg by assigning 30 dealers from 58 dealers by using randl sampling technique. The type of data used in this study includes primary data and secondary data. Data collection techniques used were observation, questionnaires and interviews. Data analysis technique used by the writer is descriptive qualitative that is in the form of tables and depiction through interview result in field by looking at respondent's answer to the implementation of supervision of Industry and Trade Office Pekanbaru City in Distribution 3 Kg LPG gas in Pekanbaru City, The steps taken in improving the implementation of the supervision of the distribution of LPG gas 3 Kg in the form of data that has been collected are analyzed by describing the existing problems and providing interpension to the relevant results then drawn conclusions. From the research can be concluded that the results obtained are still not according to the rules alias not optimal. Where the inhibiting factors for the supervision of LPG gas distribution are 3 Kg, namely, limited human resources, lack of awareness from the LPG 3 LPG bases on the distribution of 3 kg LPG gas, and the village / kelakarta apparatus and the rt and rw levels which Still do not understand the duties and functions of their positions in the participation of this 3 Kg LPG gas circulation.

Efficiency of liquid-jet high-pressure booster compressors

There are almost no experimental data on the head-capacity curves for liquid-jet compressors with the inlet gas pressure of liquid-jet apparatus more than 1 MPa. Meanwhile, this range is important for many engineering applications in which relatively low compressor ratio is required for the pumping of gas under high pressure. This is mostly the case when gas circulation is to be provided in a closed or almost closed circuit. A head-capacity curve of a liquid-jet apparatus has been estimated experimentally for the air pumping at up to 2.5 MPa by a water jet. To obtain this curve, a new original technique has been submitted and verified which is based on an inverse unsteady problem of gas pumping and allows derivation of the whole curve instead of one operating point, which is the case for conventional methods. The experiments have demonstrated that the relative head of the liquid-jet compressor grows with the apparatus inlet air pressure in the middle part of the curve.

Effect of the burner arrangement on Slab reheating characteristics in a reheating furnace

Slab reheating characteristics in the walking beam type reheating furnace were studied by using the finite volume method (FVM). A geometry model for simulating the gas circulation, heat transfer and slabs reheating process in a reheating furnace was developed by using ANSYS FLUENT software. Usually, slabs are heated in the furnace, and temperature values of the slabs reach above 1,500 K. After that, they are transported to the rolling mill. The slab reheating in a reheating furnace is influenced by many factors, such as gas velocity, moving speed of the slabs, and burner arrangement. Especially, the arrangement of burners shows a great effect on reheating the slabs. In the paper, the main object of study is to investigate the temperature distribution in the reheating furnace by considering the effect of the burner position. In addition, it is found that the temperature fields of the slabs are significantly affected by changing the positions of the burners. (Less)

Validation of COBRA-SFS with Measured Temperature Data from Spent-Fuel Storage Casks

The COBRA-SFS thermal-hydraulic code has been incorporated into the Used Nuclear Fuel-Storage, Transportation & Disposal Analysis Resource and Data System tool as a module devoted to spent-fuel-package thermal analysis. COBRA-SFS has been extensively validated and widely applied to thermal-hydraulic analysis of a large range of spent-fuel storage systems. Instead of recapping that long and detailed history, this paper summarizes the most significant and unique verification and validation of COBRA-SFS, which consists of comparison of code temperature predictions to experimental data obtained in the Test Area North Facility at the Idaho National Laboratory in the 1980s and early 1990s. These data were obtained as part of a program undertaken by the U.S. Department of Energy Office of Civilian Radioactive Waste Management for thermal performance testing of commercial spent-fuel storage cask designs. In total, four casks were tested, and all tests were performed with Westinghouse 15×15 pressurized water reactor spent fuel from the Surry or Turkey Point reactors. COBRA-SFS code results and experimental data comparisons are shown only for the CASTOR-V/21 and the TN-24P casks. CASTOR-V/21 was loaded with the highest decay heat load tested in this program, with individual assembly decay heat values up to 1.83 kW. This effectively bounds storage conditions currently contemplated for high-heat-load systems with test conditions reaching fuel cladding temperatures that approached and in some cases exceeded 400°C, the current regulatory limit for peak cladding temperature in dry storage. TN-24P, with a decay heat load of 20.5 kW, provides comparisons with experimental data that represent a realistic upper bound on typical dry storage initial conditions in independent spent fuel storage installations around the country. The consistency and accuracy of the COBRA-SFS temperature predictions in comparison to the measured data from these casks show that the code appropriately predicts the thermal-hydraulic and heat transfer behavior of these systems. The results presented here provide an excellent illustration of the capability of the COBRA-SFS code to correctly capture all three modes of heat transfer (thermal radiation, conduction, and convection) and the internal circulation of the backfill gas within a spent-fuel package in horizontal or vertical orientation.