OXYGEN TRANSFER IN HORIZONTAL PIPELINE AERATORS WITH NOZZLES

Horizontal pipeline and tubular loop aerators are of interest for fermentation and waste water treatment and are ideally suited for continuous processing. A major drawback is that these pipeline contactors invariably operate in the “elongated bubble and plug” regime in which the mass transfer rate is low. This article evaluates the performance of a horizontal pipeline aerator fitted with nozzles equispaced along its length to enhance mass transfer rates by promoting turbulence and augmenting effective interfacial area. Such devices can also be advantageously used in long pipe lines as in the case of treating waste while it is being transported. Pressure drop and overall liquid-side mass transfer coefficient data are reported as functions of liquid (water) and gas flow rates and nozzle size and spacing. It is shown that for all the conditions studied, k_La = 0.026(ΔP/L)^1.036 and that the pressure gradient is given by a simple correlation, provided an empirical parameter which characterises a nozzle is known. Preliminary investigations on the effect of surfactant ad the presence of suspended solids (size 75 μm) on mass transfer coefficient are also reported. Very high values of power dissipation can be achieved in such aerators without mechanically moving parts and high values of mass transfer coefficient can be realized.     

模拟舰船燃机压气机级间流场的喷水雾化实验研究

压气机级间喷水是舰船燃气轮机较理想的中冷技术，而此技术的关键是产生小雾滴的雾化技术，本文给出了向模拟燃气轮机压气机级间流场喷水雾化实验研究的目的。设备，测量系统，雾化机理，实验方案及步骤，给出了在模拟燃气轮机压气机组间流场内进行的喷水的不同喷入方式，不同气流速度下雾化特性和对流场阻力特性影响的实验研究结果，通过对实验结果的分析，得出喷嘴的安装方式对压气机组间流场损失的影响及雾化效果影响的结论。     

PIV/PLIF Study of Impinging Jet Ozone Bubble Column with Mixing Nozzles

This paper introduces the results obtained from a particle image velocimetry/planer laser-induced fluorescence (PIV/PLIF) system used in characterizing an impinging jet ozone bubble column with mixing nozzles. This research aims at evaluating the mixing effect resulting from the nozzle diffusers attached to the outlets of the impinging jets' injectors. The PIV system was used to study the flow patterns of the liquid and gas phases under different superficial gas and liquid velocities (u_G and u_L, respectively) values (from 0.002 to 0.017 m/s and from 0.008 to 0.024 m/s, respectively). Furthermore, a particle dynamics analyzer (PDA) system was used to characterize the bubble sizes under the same operating conditions. The PLIF system was used to determine the liquid axial dispersion coefficient (D_L, m²/s) for the mentioned range of operating conditions. The column average gas hold-up (?_G) and specific interfacial area (a) were then determined in order to evaluate the column's mass transfer efficiency. The results showed that higher mass transfer rates can be obtained by using this column, as high ?_G, and were achieved.     

大空间建筑消防设施设计探讨

现行防火规范未能涵盖大空间建筑。强调应根据具体建筑物的火灾发展特性来决定其防火需要,要使火灾安全目标、火灾损失目标和设计目标实现良好统一,即进行性能化设计。并简单介绍了适用于大空间建筑的应用快速响应早期抑制喷头的闭式喷水灭火系统、自动消防水炮系统和自动水枪装置。     

Stability Behavior of Liquid Jets under Gravity

The influence of gravity on the stability behavior of falling liquid strands without external excitation was investigated. To this end, a mathematic‐physical model was developed for the analysis of the stability behavior of liquid strands in the range of low to higher viscosity, the main emphasis being on gravity. The characteristics of the model are discussed and, finally, the stability criterion is derived for the quantitative determination of the point of disintegration.     

CORRELATION FOR DROP SIZE IN LIQUID/LIQUID SPRAY COLUMNS

A single equation is presented which predicts the drop size in liquid/liquid spray columns up to the critical nozzle velocity:

with an average deviation of 9.7%. This can be reduced to 7.3% if two regions are considered separated by a critical nozzle diameter:     

Simulation of Droplet Generation by Mixing Nozzles

In various chemical processes thorough homogeneous mixing is of great importance. Due to their small characteristic dimensions, micromixers have a great potential to achieve fast and uniform mixing. However, in the field of powder synthesis from precipitation processes the use of standard micromixers is severely limited because of rapid clogging of the microchannels. As an alternative, mixing nozzles which are less susceptible to fouling can provide a sufficient mixing quality. The flow field and fluid distribution inside multi‐fluid droplets during droplet formation is simulated. Depending on the geometry and flow rates, complex velocity fields and flow distributions are found and the impact on the mixing efficiency is qualitatively deduced. Furthermore, we point out how the tendency of fouling can be further reduced with the help of improved nozzle geometries.     

Vergleich von Nachweisverfahren für Stutzen in Zylinderschalen unter Innendruck und äußeren Lasten

Various methods for the verification of nozzles in cylindrical shells are described and the results of an example are compared. The example is carried out according to DIN EN 13445‐3, Sect. 16.5, in which the maximum permissible loads from internal pressure, axial force as well as moments in the longitudinal and circumferential direction are calculated. The results are compared with finite element computations performed with a 3D shell model, both with linear‐elastic material behavior and as limit‐load analyzes with ideal‐elastic ideal‐plastic material behavior.     

Aerodynamics of a novel rotating jet spouted bed

A novel rotating jet spouted bed (RJSB) is developed and tested. It consists of a rotating air distributor with two radially located spouting air nozzles. The effects of bed height, distributor rotational speed, nozzle diameter and particle properties on the flow characteristics were examined. Various flow regimes were mapped as functions of distributor rotational speed and superficial air velocity for different materials and column dimensions. Empirical correlations were developed for the minimum spouting velocity, peak pressure drop and steady spouting pressure drop.