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Aerators are applied to provide air entrainment and cavitation erosion protections for high-speed flows. By traditional chute aerators in high-head bottom tunnels, it is difficult to maintain effective aeration protection for low-Froude-number and small-slope conditions. The present study explores a wedge aerator design at the bottom outlet, and detailed experimental data on the aeration cavity and the entrained air diffusion were obtained to assess the aeration protection performance. The wedge aerator separates the water flow from the bottom outlet into an upper free jet and a lower flow layer, creating a middle aeration cavity. The flowing lower layer can enhance the aeration cavity stability, ensuring the cross-sectional air diffusion generation downstream due to the flow collision interactions. The flow Froude number and vertical location are the main parameters affecting the air entrainment coefficient, cross-sectional air concentration distribution, and sufficient concentrations close to the chute floor. Optimized wedge aerators are proposed, indicating that the flow interior separation is an effective hydraulic design for bottom outlets in hydraulic engineering. [ABSTRACT FROM AUTHOR]

In melt blowing, microfibrous nonwoven material is manufactured by using high-speed air to attenuate polymer melt. The melt-blown air jet determines the process of polymer attenuation and fiber formation. In this work, the importance of lateral velocity on the fiber was first theoretical verified. The lateral diffused characteristic of the air flow field in slot-die melt blowing was researched by measuring the velocity direction using a dual-wire probe hot-wire anemometer. Meanwhile, the fiber path was captured by high-speed photography. Results showed that there existed a critical boundary of the lateral diffusion, however, air jets in the x−z plane are a completely diffused field. This work indicates that the lateral velocity in the y−z plane is one of the crucial factors for initiating fiber whipping and fiber distribution.

Electro-Fenton (EF) is a promising electrochemical technology in degrading recalcitrant organic pollutants. However, the technology faces problems of high energy consumption, low cathodic oxygen transfer rate and low H 2 O 2 production efficiency. Therefore, a novel air-breathing gas diffusion electrode (GDE) with multiform hydrophobic layers was prepared by a facile method. The novel GDE allows the air to diffuse to the triphase interface spontaneously, eliminating the cost of aeration. Also, the multiform hydrophobic layers can greatly improve the oxygen transfer rate and expand the triphase interfaces in the GDE, resulting in a high H 2 O 2 accumulation of 44.30 mg L−1 cm−2 h−1 without aeration, which was 18 times higher than that of the virgin cathode. A 100% degradation efficiency of sulfadiazine (SDZ) was achieved with the fabricated GDE in 10 min in EF system. Moreover, theoretical calculations were performed for accurately elucidating the SDZ degradation mechanism and pathway. [Display omitted] • Air can diffuse into the electrode spontaneously with high diffusion coefficient. • Multiform hydrophobic layers in the electrode boosted H 2 O 2 accumulation. • The SDZ degradation process was elucidated using theoretical calculations. [ABSTRACT FROM AUTHOR]

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Abstract: In the present study it is shown that jet flows from innovative rectangular air diffusion grilles with lobed ailerons ensure higher mixing in a room than baseline jets from classical rectangular air diffusion grilles with straight ailerons. The experimental approach uses time resolved and classical large scale PIV measurements. The estimated entrainment in the case of the jet issued from the grille with lobed ailerons is found to be greater than in the case of the standard grille with straight ailerons. This way, lobed ailerons might be a solution for the optimization of air diffusion grilles in order to insure more uniform flows and to reduce thermal discomfort and draught sensation. An analysis of the phenomena being at the origin of this performance is proposed. The jet issued from an elementary slot with lobed geometry is compared to the linear slot jet. Based on the elementary slot jets analysis, it is shown that the vortical dynamics in the lobed flow is complex and is governed by large streamwise structures generated by the lobed nozzle lip. This explains the recorded performance in terms of induction and mixing. The special geometry of the lobed grille was not found to generate supplementary noise as the sound pressure levels were recorded for both grilles for different discharge flow rates. Pressure losses were also found to have similar values for both grilles. [ABSTRACT FROM AUTHOR]

Abstract: A passive chilled beam is a source of natural convection, creating a flow of cold air directly into the occupied zone. Experiments were conducted in a mock-up of an office room to study the air velocities in the occupied spaces. In addition, velocity profiles are registered when underneath heat loads exist and the cool and warm air flows interact. Experimental laboratory study revealed that in the case of the underneath heat gains, even no upward plume was generated and the dummy only acted as a flow obstacle, having a significant effect on the velocity profile. Furthermore, in an actual occupied office environment, the thermal plumes and the supply air diffuser mixed effectively the whole air volume. The maximum air velocity measured was still below 0.25m/s with the extremely high heat gain of 164W/m2. The results demonstrate that analysis methods were the interaction of convection flow and jet are not taken into account could not accurately describe air movement and draught risk in the occupied room space. [Copyright &y& Elsevier]

This paper gives an overview of the most important bioreactor configurations used in waste gas treatment, i.e., conventional and trickling biofilters, the bioscrubber, suspended-growth bioreactors, as well as two-liquid phase systems (stirred tank bioreactor and biotrickling filter). The historical evolution, main characteristics, and recent developments are described in each case. [ABSTRACT FROM AUTHOR]

Abstract: The current density of biofuel cells which use dissolved O2 as electron acceptor is limited by O2 supply to the electrode surface due to the low solubility and small diffusion coefficient of O2 in the electrolyte solution. In order to increase the current density, we constructed an air diffusion biocathode which uses O2 directly from the air. As cathodic biocatalyst, we utilized CueO from Escherichia coli, which belongs to the family of multi-copper oxidases. O2 reduction was catalyzed by CueO adsorbed on Ketjen black-modified carbon paper electrodes. The hydrophobic electrode surface was obtained by optimizing the weight ratio of polytetrafluoroethylene binder to Ketjen black. The current density of O2 reduction reached values as high as 20 mA cm−2 at 0 V vs. Ag|AgCl, KCl(sat.) in a citrate buffer (1.0 M, pH 5.0, 25 °C). [Copyright &y& Elsevier]

Abstract: The indoor air diffusion of a typical office equipped with a floor-standing type air-conditioner (FSAC) in summer was evaluated and optimized. Two existing evaluation indexes, the air diffusion performance index and the energy utilization coefficient, were modified for their more reasonable application in the evaluation on air diffusion performance of a FSAC. And also, a new index, fast cooling effect index, was presented to evaluate the fast-cooling effect. Based on the indoor airflow simulation using computational fluid dynamics, the three indexes were applied to evaluate the air diffusion performance of the FSAC. As a result, the optimal indoor air diffusion types with best thermal feelings, fine energy utilization efficiency and excellent fast-cooling effect were obtained, and also, a control scheme was suggested. [Copyright &y& Elsevier]

When they are hydraulically isolated, embolized xylem vessels can be refilled, while adjacent vessels remain under tension. This implies that the pressure of water in the refilling vessel must be equal to the bubble gas pressure, which sets physical constraints for recovery. A model of water exudation into the cylindrical vessel and of bubble dissolution based on the assumption of hydraulic isolation is developed. Refilling is made possible by the turgor of the living cells adjacent to the refilling vessel, and by a reflection coefficient below 1 for the exchange of solutes across the interface between the vessel and the adjacent cells. No active transport of solutes is assumed. Living cells are also capable of importing water from the water‐conducting vessels. The most limiting factors were found to be the osmotic potential of living cells and the ratio of the volume of the adjacent living cells to that of the embolized vessel. With values for these of 1·5 MPa and 1, respectively, refilling times were in the order of hours for a broad range of possible values of water conductivity coefficients and effective diffusion distances for dissolved air, when the xylem water tension was below 0·6 MPa and constant. Inclusion of the daily pattern for xylem tension improved the simulations. The simulated gas pressure within the refilling vessel was in accordance with recent experimental results. The study shows that the refilling process is physically possible under hydraulic isolation, while water in surrounding vessels is under negative pressure. However, the osmotic potentials in the refilling vessel tend to be large (in the order of 1 MPa). Only if the xylem water tension is, at most, twice atmospheric pressure, the reflection coefficient remains close to 1 (0·95) and the ratio of the volume of the adjacent living cells to that of the embolized vessel is about 2, does the osmotic potential stay below 0·4 MPa. [ABSTRACT FROM PUBLISHER]

In melt blowing, microfibrous nonwoven material is manufactured by using high-speed air to attenuate polymer melt. The melt-blown air jet determines the process of polymer attenuation and fiber formation. In this work, the importance of lateral velocity on the fiber was first theoretical verified. The lateral diffused characteristic of the air flow field in slot-die melt blowing was researched by measuring the velocity direction using a dual-wire probe hot-wire anemometer. Meanwhile, the fiber path was captured by high-speed photography. Results showed that there existed a critical boundary of the lateral diffusion, however, air jets in the x–z plane are a completely diffused field. This work indicates that the lateral velocity in the y–z plane is one of the crucial factors for initiating fiber whipping and fiber distribution. [ABSTRACT FROM AUTHOR]