Optimum Flow Ratio Research Articles

RESEARCH AND OPTIMISATION OF THE QUANTITATIVE AND QUALITATIVE CHARACTERISTICS OF GRAIN SHIPLOAD LOTS IN GRAIN TERMINALS

The structure of loading different crops onto vessels at the company Ukrelevatorprom’s grain terminal has been considered. The total grain shipped in 2012–2015 was comprised of 33.7–41.5% of maize, 19.7– 32.2% of wheat, 14.4–26.0% of rapeseed, 6.7–14.2% of barley, and 5.4– 11.0% of soya beans. When forming a 35,000-tonne grain shipload, grain lots stored in silos are sometimes of lower quality than contracts require: the protein and gluten contents can be inappropriate, or there can be smut grains or those damaged by sunn pests. The accepted technology of grain shipload formation does not guarantee that the grain quality will be uniform throughout the whole period of loading a vessel, especially in the beginning. In the first 1,000 tonnes of a grain shipload formed, the weight content of wet gluten was found to be 22.6% instead of 23%, the Falling Number was 145–180 s instead of 230s, and the content of smut grains was not the tolerable 5%, but 6.95–7.8%. The subsequent 2,000–3,000 tonnes of wheat, too, had the Falling Number lower than the contract prescribed (142–215 s), and only further on, its value achieved the required range 295–356 s. In the wheat sample formed from 5,000 tonnes, only the test values of the Falling Number (176s) and the content of smut grains (5.1%) were different from what the contract required. The calculated arithmetic means of the quality parameters of the 5,000-tonne wheat samples formed were practically the same as those determined experimentally, except for the values of the Falling Number and the smut grain content. The values of the coefficient of variation obtained showed that the grain lot was of non-uniform quality: it varied in such parameters as the foreign material (20.82–50.93%), sunn pest-damaged grains (7.41–25.76%), Falling Number (8.76–36.36%), and smut grain content (35.88–78.34%). Application of linear programming methods to optimise the shipload composition has allowed all the quality parameters to meet the contract requirements. Loading grain from all silos simultaneously, with the optimum flow ratio, will result in its even distribution in a shipload, and the grain lot will be of higher quality by all the parameters the contract specifies.

Microjet flow control in an ultra-compact serpentine inlet

Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interface plane (AIP) face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control (MFC) effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the momentum coefficient affects the control effectiveness in a dual stepping manner.

Effect of free air inflow method on fine particle classification of gas-cyclone

The effect on particle separation performance using a free air inflow cyclone at the upper plate was examined by experiment and CFD simulation. The 50% cut size with the free air inflow cyclone is smaller than that without the free air inflow cyclone under the same pressure drop condition. The optimum flow ratio defined by the free air inflow rate to main flow rate is 0.4. The four slit inlet cyclone shows better particle separation performance compared to other types. For a flow ratio greater than 0.4, the 50% cut size increases again due to the decrease of the main flow rate.From the simulation results, the rotational and downward flow velocity in the upper cylindrical part with the free air inflow cyclone is greater than that without the free air inflow cyclone. In the case of the free air inflow cyclone, a particle trajectory simulation indicated that particles entering the cyclone tend to move to the circular wall region smoothly. The experimental and simulation results indicate higher particle separation performance for the free air inflow cyclone.

Numerical study of a M-cycle cross-flow heat exchanger for indirect evaporative cooling

In this paper, numerical analyses of the thermal performance of an indirect evaporative air cooler incorporating a M-cycle cross-flow heat exchanger has been carried out. The numerical model was established from solving the coupled governing equations for heat and mass transfer between the product and working air, using the finite-element method. The model was developed using the EES (Engineering Equation Solver) environment and validated by published experimental data. Correlation between the cooling (wet-bulb) effectiveness, system COP and a number of air flow/exchanger parameters was developed. It is found that lower channel air velocity, lower inlet air relative humidity, and higher working-to-product air ratio yielded higher cooling effectiveness. The recommended average air velocities in dry and wet channels should not be greater than 1.77 m/s and 0.7 m/s, respectively. The optimum flow ratio of working-to-product air for this cooler is 50%. The channel geometric sizes, i.e. channel length and height, also impose significant impact to system performance. Longer channel length and smaller channel height contribute to increase of the system cooling effectiveness but lead to reduced system COP. The recommend channel height is 4 mm and the dimensionless channel length, i.e., ratio of the channel length to height, should be in the range 100 to 300. Numerical study results indicated that this new type of M-cycle heat and mass exchanger can achieve 16.7% higher cooling effectiveness compared with the conventional cross-flow heat and mass exchanger for the indirect evaporative cooler. The model of this kind is new and not yet reported in literatures. The results of the study help with design and performance analyses of such a new type of indirect evaporative air cooler, and in further, help increasing market rating of the technology within building air conditioning sector, which is currently dominated by the conventional compression refrigeration technology.

Phase-Transfer Catalysis in Segmented Flow in a Microchannel: Fluidic Control of Selectivity and Productivity

Precise control over the interfacial area of aqueous and organic slugs in segmented flow in a microchannel reactor provides an attractive means to optimize the yield and productivity of a phase-transfer-catalyzed reaction. Herein, we report the selective alkylation of phenylacetonitrile to the monoalkylated product in a microchannel of 250-μm internal diameter operated in a continuous and solvent-free manner in the slug-flow regime. The conversion of phenylacetonitrile increased from 40% to 99% as a result of a 97% larger slug surface-to-volume ratio when the volumetric aqueous-to-organic phase flow ratio was raised from 1.0 to 6.1 at the same residence time. The larger surface-to-volume ratio significantly promoted catalyst phase transfer but decreased selectivity because of the simultaneous increase of the rate of the consecutive reaction to the dialkylated product. There exists an optimum flow ratio with a maximum productivity. Conversion and selectivity in the microchannel reactor were both found to b...

Microcrystalline β-SiC Growth on Si by ECR-CVD at 500°C

ABSTRACTMicrocrystalline β-SiC films were deposited on silicon substrates by electron cyclotron resonance chemical vapor deposition (ECR-CVD) at 500°C utilizing a SiH4-CH4-H2 gas mixture. The effects of two important parameters on film growth, SiH4/CH4 flow ratio and microwave (MW) power, were investigated using X-ray photoelectron spectroscopy (XPS) along with the Fourier transform infrared spectra (FTIR). Results showed that the optimum flow ratio is about 0.5. Under the optimum flow ratio, a large MW power is favorable for the growth of high quality films with an ideal film stoichiometry. Surface morphology inspected by the contact mode atomic force microscopy (AFM) reveals that high MW powers not only improve the film crystallinity but also increase its surface roughness as well.

The Optimum Flow Ratio in a Continuous Countercurrent Fractional Separation Column

The Optimum Flow Ratio in a Continuous Countercurrent Fractional Separation Column

Counter-Current Computation on Trinitrato Complex of Nitrosylruthenium in the Primary Separation Plant of Reactor Fuel Processing, (III)

A mathematical treatment to the optimum flow ratio for the counter-current extraction of penta and tetra complexes of nitrosylruthenium in the primary separation plant of reactor fuel processing has been developed from the previous publication(1×2). The optimum flow ratio is a rather simple function of ratio of reaction rate constants and molar ratio of trinitrato complex to penta and tetra complexes. Another, and much higher, volume flow ratio for the maximum decontamination factor of penta and tetra complexes has also been numerically introduced for justification of the optimum flow ratio. The significant effect of lower nitric acidities in aqueous phase on the ruthenium decontamination has been discussed. Calculated results from the obtained equation for the optimum flow ratio have been compared with the values used in practice in the ruthenium decontamination process, and have shown remarkable agreement.

Calculation of the extraction of the trinitrato complexes of nitrosylruthenium in the primary separation plant of reactor fuel processing—II

A mathematical treatment to determine the optimum flow ratio and the decontamination factor for the counter-current extraction of penta and tetra complexes of nitrosylruthenium in the primary separation section of a reactor fuel reprocessing plant has been developed from the previous paper by Takigishi (1964). The optimum flow ratio is a rather simple function of ratio of reaction-rate constants and molar ratio of trinitrato complex to penta and tetra complexes. The decontamination factor is a complex function of reaction-rate constants, number of stages, mixing time per bank and the volume flow ratios of solvent, feed and strip which may be converted to the optimum flow ratio. Calculated results from the equations obtained in this and the previous paper by the author might give good agreement with the experimental results of the miniature extractor runs by Ashworth et al. (1957). Further calculations provide an analysis of the operation of ruthenium decontamination and the role of repeated decontamination treatments or cycles of operation.