Showing papers on "Diffuser (sewage) published in 2019"

Aeration Process in Bioreactors as the Main Energy Consumer in a Wastewater Treatment Plant. Review of Solutions and Methods of Process Optimization

Abstract: Due to the key role of the biological decomposition process of organic compounds in wastewater treatment, a very important thing is appropriate aeration of activated sludge, because microorganisms have to be supplied with an appropriate amount of oxygen. Aeration is one of the most energy-consuming processes in the conventional activated sludge systems of wastewater treatment technology (may consume from 50% to 90% of electricity used by a plant), which makes it the most cost-generating process incurred by treatment plants. The paper presents the construction of aeration systems, their classification as well as parameters and factors that significantly affect the aeration process e.g., oxygen transfer efficiency, diffuser fouling, methods of dealing with diffuser fouling, diffuser selection. Additionally, there are briefly presented “smart control” systems in wastewater treatment and effect of application control strategy based on Supervisory Control and Data Acquisition system connected with the decrease in the energy consumption for aeration of bioreactors with activated sludge. It is noted that before the process is optimized, the system should be equipped with suitable metering devices. Only when relevant data is available, the improvements can be carried out. However, it’s important, that the operator should regularly maintain good condition and high efficiency of diffusers.

Bubble generation by micro-orifices with application on activated sludge wastewater treatment

Abstract: We studied the initial gas dispersion performance of diffuser concepts based on micro-orifices and needles with very fine orifice diameters in the range from 37 μm to 225 μm, as such diffusers are currently in discussion for energy-efficient wastewater treatment plants. To evaluate the performance of these micro-orifices, we compared them with industrial rubber membrane diffusers with respect to Sauter mean bubble diameter, pressure drop, frequency of bubble formation, oxygen transfer rate, and power demand for air compression. Our study revealed that, in comparison with current state of the art of rubber membrane diffusers, bubbles generated from the micro-orifices transfer up to 22% more oxygen content into the continuous phase at up to 51% less power demand. Moreover, these micro-orifices are able to produce bubble sizes in the same range as the needle diffusers at 60% less pressure drop and 60% higher bubble generation frequency.

Effect of Slot-Guidance and Slot-Area on Air Entrainment in a Conical Ejector Diffuser for Infrared Suppression

Abstract: A numerical study has been carried out on a new design of ejector diffuser (infrared suppression device). New design conceptualizes exploiting the shape of the slot openings. A circular arc is provided to guide the entrained fluid at the slot openings. Performance of guided-slot ejector diffuser (GED) has been compared with conventional (non-guided-slot) ejector diffuser (NGED) in terms of local and cumulative mass entrainment ratios, temperature distribution and static pressure recovery. Three slot-area variations are also studied, namely (i) increasing slot-area ranging 1 ≤ A0 ≤ 2.02, ( 0 A is area of 1 st slot) (ii) constant slot-area A0 = 1 and (iii) decreasing slot-area ranging 0.49 ≤ A0 ≤ 1. Simulations have been carried out at fixed Reynolds number Re = 1.3  10. It is observed that GED has 3.5% higher cumulative mass entrainment ratio than NGED. GED forms cold annulus region below ejector diffuser wall from 1 slot onwards which results in wall temperatures being close to ambient temperature (300 K). Higher mass entrainment rate and lower wall temperatures make GED a better infrared suppression device but static pressure recovery is better in NGED (Cp = 0.79) compared to GED (Cp = 0.43). Slot-area study reveals that the performance of increasing slot-area for GED and NGED is superior then constant and decreasing slot-area configurations. The cumulative mass entrainment is 20% higher while static pressure recovery is 45% more for the increasing slot-area GED when compared to the decreasing slot-area GED.

A Review of Ground-Effect Diffuser Aerodynamics

Abstract: The ground-effect diffuser has become a major aerodynamic device on open-wheel racing and sports cars. Accordingly, it is widely considered to be indispensable to their aerodynamic performance, largely due to its significant downforce contribution. However, the physics and characteristics that determine how it generates downforce and its application in the auto racing industry require an in-depth analysis to develop an understanding. Furthermore, research that could generate further performance improvement of the diffuser has not been defined and presented. For these reasons, this review attempts to create a systematic understanding of the physics that influence the performance of the ground-effect diffuser. As a means of doing this, the review introduces research data and observations from various relevant studies on this subject. It then investigates advanced diffuser concepts mainly drawn from the race car industry and also proposes a further research direction that would advance the aerodynamic performance of the diffuser. It is concluded that although the diffuser will continue to be paramount in the aerodynamic performance of racing cars, research is needed to identify means to further enhance its performance.

Oxygen transfer improvement in MBBR process

Abstract: In the last years, the upgrading of wastewater treatment plants (WWTPs) could be required in order to comply with the more stringent regulation requirements. Nevertheless, the main issue is related to the surface availability. A proper solution could be represented by the attached biomass processes, in particular the moving bed biofilm reactors (MBBR), that have a significant footprint reduction with respect to conventional activated sludge (CAS). However, MBBR showed an important disadvantage: the poor aeration energy efficiency due to the use of coarse bubble diffusers, which guarantee high reliability and low maintenance costs with respect to fine bubble ones. Moreover, the presence of carriers inside the reactor emphasizes this aspect. The aim of this work is to verify the benefits achievable by installing a fine bubble aeration system inside a MBBR system. The comparison, in terms of oxygen transfer efficiency, between a medium bubble aeration system and a fine ceramic bubble diffuser was studied and the effect of biofilm growth on oxygen transfer was assessed. Several tests were carried out in order to test the operation of a coarse and a fine bubble side aeration at different air flow rates, both in clean water conditions, in order to evaluate the influence of carriers (Chip M type) on the aeration efficiency, both in wastewater conditions with the aim to assess the effect of bacteria growth on the carriers. The main results are the following: (i) the fine bubble system placed off-center ensured good mixing even without using the mixer; (ii) the fine bubble side aeration system compared to the coarse ones did not show significant advantages in terms of oxygen transfer efficiency; (iii) the increase in specific air flow rate negatively influenced the aeration efficiency; (iv) the presence of biomass had a positive effect on the oxygen transfer yield.

2D/3D mixed display based on integral imaging and a switchable diffuser element.

Abstract: In this paper, we present a 2D/3D mixed system with high image quality based on integral imaging and a switchable diffuser element. The proposed system comprises a liquid crystal display screen, lens array, switchable diffuser element and projector. The switchable diffuser element can be controlled to present 2D/3D mixed images or 2D and 3D images independently, and can reduce the Moire fringe and black grid. In addition to the improved display quality, the proposed system has advantages of a simple structure and is low cost, which contribute to the portability and practicability.

Optimization of microalgae Scenedesmus SP. growth rate using a central composite design statistical approach

Abstract: In this research, growth rate of microalgae Scenedesmus sp. was modified by optimizing four effective factors. The operational energy efficiency factor (OEEf) of the photobioreactor was also considered in parallel. A central composite design statistical approach was implemented to evaluate the results. These factors were carbon dioxide concentration (0.038 (air), 2.0, 5.0, 7.0, 10.0%), aeration rate (0.2, 0.5, 1.5, 3.0, 4.0 vvm), initial inoculum concentration (0.140–0.430 g/l) and gas diffuser diameter (0.4, 1.0, 2.6, 4.0, 5.0 mm). All the factors were very significant at the defined ranges. The diffuser diameter also showed different effect when either low or high carbon dioxide concentration was applied. The optimized values (6.02% CO2, 0.39 vvm flow rate, 3.7 mm diffuser diameter and 0.180 g/l initial inoculation) would result the maximum growth rate of 0.525 g/l.d and high OEEf of 19.5 which was very significant. It was concluded that microalgae technology is a promising solution for carbon dioxide sink in large scale and biofuel production after optimizing the biomass production rate.

A design analysis of piezoelectric-polymer composite-based valveless micropump

Abstract: This paper presents the three-dimensional numerical simulation of a micropump, including diffuser and analytical modelling of the micropump flow rate. The numerical simulation of the diffuser is pe...

Hypolimnetic oxygenation of water supply reservoirs using bubble plume diffusers

Abstract: Mobley M, Gantzer P, Benskin P, Hannoun I, McMahon S, Austin D, Scharf R. 2019. Hypolimnetic oxygenation of water supply reservoirs using bubble plume diffusers. Lake Reserv Manage. 35:247–265. Hyp...

Mixing of Tee Diffusers in Shallow Water with Crossflow: A New Look

Abstract: This paper analyzes the mixing of a tee diffuser discharging in shallow water with currents. Experiments are conducted for tee diffusers with different designs discharging in a crossflow. M...

Portable voice assistant device with linear lighting elements

Abstract: Systems, methods, and computer-readable media are disclosed for portable voice assistant devices with linear lighting elements. In one embodiment, an example device may include a housing having a first portion and a second portion, an elongated light bar disposed between the first portion and the second portion, and a first LED disposed within the housing. Example devices may include a reflector component configured to reflect light towards the elongated light bar, and a diffuser positioned adjacent to the elongated light bar. The diffuser may include a first curved portion and a flat portion, and the first curved portion may be substantially aligned with the first LED.

Numerical Simulation of Diffuser of a Gas Turbine using the Actuator Disc Model

Abstract: An analysis of the exhaust diffuser section of a gas turbine is presented by incorporating the reduced order mathematical model “actuator disc concept” that represents the last stage of the turbine. The actuator disc model is one of the simplified numerical methods for analyzing the aerodynamic performance of axial turbine stage. In which, the rotor and the stator of the turbine stages are modeled as zero thickness discs with a specified blade speed and zero speed respectively. Finite volume based commercial CFD package ANSYS FLUENT was employed for the numerical investigation of the applicability of the proposed simplified model. The compressible Navier-Stoke equations along with k- turbulent model were solved in the computational domain by incorporating suitable boundary conditions. The implementation of actuator disc boundary conditions is described in detail. The numerical results obtained from the proposed model are in good agreement with the experimental data available in the literature. The effect of casing angle on the performance of diffuser is presented.

Effect of Shallowness on Dilution of Unidirectional Diffusers

Abstract: The effect of receiving water depth on the dilution of a unidirectional diffuser discharging dense effluent in quiescent conditions is analyzed. Dilution measurements from previous studies ...

Efficiency improvement and evaluation of a centrifugal pump with vaned diffuser

Abstract: In order to enhance the efficiency of centrifugal pump, the structure of a centrifugal pump with vaned diffuser, whose specific speed is 190, was numerically improved by trimming back-blades of imp...

Experimental characterization and modelling of microfluidic radial diffusers for passive self-regulating valves

Abstract: A microfluidic radial diffuser typically comprises a hole in a membrane facing a concentric pillar separated by a small gap where the fluid is forced to flow radially between the membrane and the pillar. Such diffusers are notably used to make passive flow rectification valves for drug delivery devices, wherein several holes are machined into a flexible membrane progressively deflecting against pillars as the pressure increases on top of it. The fluidic modelling of such a diffuser is made difficult by the presence of a transition region between the hole and the diffuser itself. An experimental investigation has been conducted using SOI wafers to form membranes having only one central hole and Pyrex wafers for the substrate and pillars. Both wafers are anodically bonded together after alignment. A simple fluidic model accounting for the specific geometry of the diffuser is proposed and compared to experimental results. A good match is obtained, for Reynolds number in the range 0.5 to 35, using the analytical formula of a radial diffuser in the laminar regime with an effective inner radius 40% smaller than the actual one, in order to correctly simulate the flow constriction at the entrance of the diffuser.

Real-time co-registered photoacoustic and ultrasonic imaging for early endometrial cancer detection driven by cylindrical diffuser

Abstract: In illuminating tissues, a cylindrical diffuser (CD) has an advantage over regular laser sources due to its ability to illuminate a larger volume of the target tissue. This paper presents a co-regi...

Thermostat with halo light system and emergency directions

Abstract: A thermostat for a building includes a halo light emitting diode (LED) system including one or more LEDs configured to emit light and a halo diffuser structured around at least a portion of an outer edge of the thermostat The halo diffuser is configured to diffuse the emitted light of the one or more LEDs around at least the portion of the outer edge of the thermostat The thermostat includes a processing circuit configured to receive one or more data streams, determine whether the one or more data streams indicate a building emergency condition, and operate the one or more LEDs of the halo LED system to indicate the building emergency condition to a user

Steam Turbine Axial Exhaust Diffuser Investigation Using a Test Rig and its Numerical Model

Abstract: Exhaust casings are one of the most important steam turbine components. The main purpose of the exhaust casing is to increase the last stage enthalpy drop, which results in an increase of the whole turbine output. It plays a significant role especially in turbines with lower outputs and in turbines whose condenser is cooled by air. In such cases, the exhaust casings with an axial diffuser is usually used. This paper deals with the investigation of the axial diffuser outlet part based on experimental measurements performed on a test rig installed in a wind tunnel in the Doosan Skoda Power laboratories and numerical simulations. The first part of the paper is about the general issues appearing the exhaust diffusers. Then, the design of the experimental test rig which aim is to simulate the flow conditions in real turbines is described. The last part of the paper is about experimental measurement as well as numerical results. The main observed phenomenon which is the effect of the circumferential angle on the inlet of the diffuser is described on different designs which were tested from the static pressure recovery factor point of view. For measuring flow parameters, a static wall pressure measurement was used together with multi-hole pneumatic probes. For numerical simulations, the commercial code ANSYS CFX 18.2 was used.