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The effects of an inlet inertial jet on the thermal blending of hot and cold heat transfer fluid (molten salt) for a single tank sensible thermal energy storage system are studied using numerical simulations. The simulations show the evolution of the initial stratified layer (thermocline) for a temperature difference of 300 K with a corresponding Atwood number (At) of 0.066. Three diffuser arrangements are investigated: a flat plate solid diffuser, a coaxial ring diffuser with a solid center, and a proposed hemispherical diffuser. The thermal stratifications are examined by a mathematical model named Ideal stratification index (ISI). It is observed that the buoyancy-driven mixing is minimum for the hemispherical diffuser, and the resulting thermocline is 6% better compared to alternative diffusers at 27 l/min. Additionally, the working of the proposed diffuser is demonstrated via experiments with a saline-freshwater combination. These results reveal that the single tank thermocline storage performance can be improved for higher charging/discharging rates using hemispherical diffusers.

Nowadays renewable energy sources play an important role in partially meeting the global energy demand and protecting the environment. Wind energy technology among the renewable sources is developi...

Air diffusers or spargers have been used in separation processes that include conventional wastewater treatment. Over the years, there have been advancements in diffuser design in terms of shape, pore size, orientation and materials of construction as a way of mitigating challenges such as fouling, clogging, energy consumption and poor system efficiency. Some of the available air diffusers are inadequate to solve most of these challenges due to reduced quality and increased quantity of wastewater being treated. Additionally, there is a paucity of information regarding air diffuser design and their effect on operational parameters in wastewater treatment. This review seeks to address the advancement in diffuser design and also the effects of design factors including parameters of air diffusers with a focus of their use in a column flotation system for wastewater treatment. HIGHLIGHTS Applications of 3D printed air diffusers in a column flotation system.; The effect of the diffuser design on operational parameters.; Reducing the rate of fouling and improving the quality of treated water.; Diffuser designs with oxidative air generating properties for wastewater treatment.; Advancement in diffuser design for flotation system used for wastewater treatment.

Centrifugal compressor plays a vital role in the performance of a turbocharger. The compressor contains an impeller and housing, including the vaneless diffuser and a volute. The high-speed flow from the impeller is diffused in the diffuser and volute, before being delivered to the engine. Hence, the housing flow characteristics affect the compressor performance and operating range. Generally, housing has noticeable surface roughness, especially in the volute. This study evaluates the effect of the volute surface roughness on the compressor performance by experimental and numerical analysis. The experiments are conducted for three different volute surface roughness levels to measure the overall compressor pressure ratio and efficiency. The uncertainty in the efficiency for experimental results is within ±0.5% pts. Also, steady-state numerical simulations are performed to analyse the flow mechanisms causing pressure losses. Then, a numerical analysis is done to understand the effect of roughness of the diffuser hub and shroud walls on the compressor performance. From the experimental results, it is found that the increase in the roughness level of the volute from the smooth surface by circa 900% and 1400% shows a significant reduction in the compressor efficiency at the design speed (N) and off-design speeds (0.87 and 1.13 N). The reductions of efficiency are about 0.5%–1% pts at the near surge point, 1%–1.5% pts at the peak efficiency point and 2%–2.5% pts at the near choke flow point. The CFD analyses show significantly higher near-wall turbulence and wall shear resulting in additional pressure losses. Also, it is found that the pressure losses are more sensitive to roughness of the diffuser shroud-wall than that of the hub-wall. On the other hand, the diffuser hub-wall roughness increases the radial momentum in the diffuser passage which suppress the flow separation at low flow rates.

The wind turbine power decreases at low wind speed. A flanged diffuser plays a role of a device for collecting and accelerating the approaching wind, and thus the optimization of the diffuser shape presents an important way to enhance the wind turbine power. In this work, a numerical parametric study was conducted on the diffuser to obtain the initial optimum form of flanged diffuser. Then, the Simplex algorithm is used to obtain the optimal diffuser shape starting from the obtained initial shape. Finally, the obtained optimum diffuser shape is used with conventional wind turbine blade. The diffuser shape is defined by four variables: open angle, flange height, centerbody length, and flange angle. The numerical simulation of flanged diffuser is carried out using the “CFDRC package. The results indicated that, the optimum diffuser shape can be obtained using simplex algorithm which maximizes the entrance average velocity to reach 1.77 times wind speed. The power augmented by a factor about 2.76:5.26 of a selected small wind turbine using the obtained diffuser shape compared to that without diffuser.

Traditional vehicles are designed to bring out the best performance, good fuel economy, fewer emissions, and good high-speed stability. In this process of designing a vehicle, the underbody geometry of a car plays a vital role and is often neglected because of its complicated design bits. Though the presence of uneven surfaces causes the layers of air to separate resulting in generating turbulence. This report is about designing an active rear diffuser of a car. The rear diffuser is an aerodynamic device that is installed in the end part of the underbody of a car. Diffuser now a day is quite a common aerodynamic device that is used in performance cars. The main moto of attaching a diffuser is to reduce the wake produced behind the car and help the streamlines to converge better. The prime focus of this study is to design an active rear diffuser that will not only help in providing great high-speed stability and aerodynamic efficiency but will also use the aerodynamic forces adversely to help the car stop faster and on its track. This is made possible first by understanding the effects of diffuser angle on the aerodynamic forces acting on the car. Further, to actually transform the computational values into a working model, an electronic circuit is designed which mimics the exact movement of the diffuser according to the speed and other driving conditions. Keywords: Adaptive, diffuser, automobile, aerodynamic, aerodynamic Drag, aerodynamic Lift

Clean drinking water is a necessity and recycling stormwater and greywater has been more appealing in the recent decades to provide filtered water for drinking water and non-drinking water purposes. Biosand filters have been a popular filtering system of filtering potable water in developing countries, due to their simplicity in construction, reliability in operation and availability of constituent materials. The sand filtration system consists of diffuser rock, two sizes of gravel, and sand, which the container is constructed from concrete or plastic. Sand filtration system tend to struggle in removing specific chemicals such as nitrate and phosphate. Therefore, innovative materials can be added to the sand filtration system to increase the chances of chemical removal. Innovative materials such as biochar and bentonite clay were used to analyze their effectiveness in sand filtration system experiments. Biochar and bentonite clay have unique characteristics such as absorbing capacity and activated carbon, which remove suspended solids, chemicals, and toxins from contaminated water. Constant head permeability tests were used to simulate the sand filtration system in the lab. 15 tests were completed with different filter media arrangements, which incorporated two types of sand (coarse and fine), two sizes of gravel (small and large), biochar, and sodium bentonite clay. Contaminated water was created by simulating greywater by adding chemicals to reverse osmosis water. The pH, sulfate, chloride, phosphate and nitrate ion concentration removal were analyzed based on the contaminated water and filtered water. The hydraulic conductivity, filtration rate and pressure loss were also analyzed for each test. The tests that had the most effective result in terms of chemical ion removal, pH neutralization and filtration rate was the arrangement that included large and small gravel, fine and coarse sand, and biochar.

The preset paper proposes a novel acoustic diffuser which we call cross rib diffuser (CRD) and investigates its acoustical performance in rooms experimentally. CRD consists of overlapping two one-dimensional periodic rib diffuser (OPRD) with different structural configurations. CRD can achieve high scattering coefficient with wider frequency band than OPRD. Moreover, unlike other diffusers with high scattering property such as metadiffuser and two-dimensional quadratic diffuser, CRD keeps simple and familiar design of OPRD suitable for use in various architectural spaces. In the paper, we firstly evaluated random-incidence scattering coefficient of CRD using 1/5 scaled reverberation room. Then, random-incidence absorption coefficient was measured in 1/1 reverberation room. Finally, an implementation experiment was conducted to examine applicability of CRD in improving acoustics in small meeting room with small absorption treatments. The results indicated that CRD reduced EDT and reverberation time, and increased D50 more than JND values. Additionally, CRD improved reverberation and speech intelligibility more significantly than OPRD with same installation area.

Indoor air quality needs attention, especially during the COVID-19 pandemic because the majority of activities are carried out indoors. The air in the room must be protected from the threat of harmful virus and bacterial contaminants. One such innovation is placing diffuser in the room. Diffuser is a device that converts liquid into gas particles in the air. To reduce harmful virus contamination, a natural antiseptic liquid is filled into the diffuser, one of which is papermint essential oil, which can provide freshness in the room. Air quality is monitored with internet of things (IoT) technology so that users can easily control air quality with just a PC/gadget. The gas output from the diffuser is detected by a gas sensor that is connected to the wemos board so that the data can be connected to the internet cloud. To obtain optimal air quality data, the placement of gas sensors in the area around the diffuser as a point of observation needs to be considered because the distribution of gas in the air is influenced by the vertical wind speed in the room, this can affect the quality of the data generated. This study aims to determine the optimal observation point on an IoT-based diffuser so that the resulting air quality data is more accurate. In this study the gas sensor was placed at a distance of 15 and 25 cm from the diffuser. The direction of the gas sensor placement was adjusted according to the angle of the full circle ranging from 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°, and 0°. The distribution of gas is influenced by the vertical wind speed in the room causing the air quality data at a vertical angle to always have the same pattern. From the results obtained, the optimal observation point as a reference for the position of the gas sensor to the diffuser is at an angle between 135°-180° as well as at an angle between 315° -0°.

Patients with cystic fibrosis are experimenting with inhaling essential oils (scientifically described as random plant-derived secondary metabolites) through diffusers or nebulizers as a form of natural therapy to treat chronic lung infections.

Virgin coconut oil (VCO) is pure coconut oil with low free fatty acid content and high lauric acid content. VCO has been produced in many home industries where the yield obtained is still very small. So, the researchers tried to find a more efficient production process so that they could obtain high process yields. Researchers made VCO using the aeration method with a diffuser type aerator. The experimental variables were air flow rate (L / min): 0.6; 1.8; 4.0; 4,5 and the duration of the aeration process (hours): 2; 3; 4; 5, by using coconut milk from 1 kg of grated coconut in 1 liter of water, the maximum yield is 33.5% at an air flow rate of 4.0 L / min with an aeration time of 4 hours. The quality of VCO obtained were: water content of 0.02%; iodine number 5,54%; peroxidation number 1.36 g.iod / 100 g; 0.19% free fatty acids; saturated fatty acid content of 93.71% and unsaturated fatty acid 6.24% and the color is very clear. The quality test results obtained are in accordance with the quality standards required by SNI 7381-2008.

The present paper assesses the empirical performance of a four-cylinder CNGDI engine with a vaned diffuser turbocharger compressor. This evaluation was performed to compare injection timing operating characteristics of engines coupled with vaneless and vaned diffuser turbocharger. Numerous start of injection (SOI) have been investigated, ranging from advanced SOI (300°CA to 180°CA bTDC) during the intake stroke to retarded SOI (180°CA to 120°CA bTDC) during the compression stroke. This experiment was conducted at a wide-open throttle (WOT) condition and the air fuel ratio is set at a stoichiometric condition. Study outcomes indicate that the vaned turbocharger increases boost pressure by an average of 50% compared to the vaneless variant. In comparison, a CNGDI engine equipped with a vaned diffuser turbocharger compressor increased brake torque by 3.66%, brake thermal efficiency (BTE) by 12.90% and volumetric efficiency by 4.75% when compared to a vaneless variant. Furthermore, a comparison of vaneless and vaned turbochargers indicates that brake specific fuel consumption (BSFC) reduced by 9.43%.

The primary cause of mechanical-related fish injury and mortality in turbomachinery is blade strike. Fish contained in the flow may strike with the rotor blades and the fixed diffuser vanes, the latter being a non-negligible factor causing fish damage in the pump system. In this study, an experiment-based correlation of fish mutilation ratio acts as critical strike velocity. The relation between strike damage in a vaned diffuser and the theoretical pump head is presented as a function of specific speed. As an example, a vaned diffuser is designed for a single-bladed, mixed-flow impeller with the purpose of improving fish friendliness. This pump can be scaled to operate with a head up to 14 m at peak efficiency, without fish damage in the diffuser. Subsequently, experiments are conducted to show the retained pump performance as well as the great improvement of fish friendliness.

Design of a supersonic inlet with double S-bend diffuser was developed. Numerical simulation and wind tunnel experiment were carried out to investigate the aerodynamic performance and variable geometric rules of the inlet. The result indicates that the variable geometry scheme adopted solves the contradiction between starting performance at low Mach number and aerodynamic performance at high Mach number. The inlet works normally and stably over a wide speed range. At design point, the total pressure recovery coefficient reaches 0.47. In addition, two different kinds of inlets with double S-bend diffuser and single S-bend diffuser were studied. Compared with the double S-bend diffuser, the total pressure recovery coefficient of the single S-bend diffuser is higher at low Mach number (Ma0< 3) and lower at high Mach number (Ma0> 3). With the increase of backpressure, shock train mainly moves upstream along the low-energy flow region in the diffuser. For the double S-bend diffuser, shock train will first move along the lower corner and then along the upper corner. For the single S-bend diffuser, it will only move along the upper corner. The strong secondary flow of the double S-bend is the main reason for the above phenomenon.

A transmissive diffuser that is based on polymer-dispersed liquid crystal (PDLC) film has been developed. Liquid crystal E7 and polymer NOA65, at a ratio of 55:45 by weight, were utilized to fabricate the diffuser. With the use of phase separation, diffuser of 7.5 µm PDLC film thickness can be formed after 20 minutes UV irradiation with an ultraviolet lamp (36E @ 365nm). Test results have shown that the proposed diffuser has good classic electro-optical and transmissive imaging features under an external tuneable electric field. The development has a great application potential in augmented reality or mixed reality-type applications.

The strut structure directly affects the flow field characteristics and aerodynamic performance of the gas turbine exhaust diffuser. The effects of the strut profiles and strut skewed angles on the aerodynamic performance of the exhaust diffuser at different inlet pre-swirls were numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes(RANS) and Realizable k-ε turbulence model. The numerical static pressure recovery coefficient of the exhaust diffuser is in agreement with the experimental data well. The reliability of the numerical method for the exhaust diffuser performance analysis was demonstrated. Exhaust diffusers with four kinds of vertical strut profiles obtain the highest static pressure recovery coefficient at the inlet pre-swirl of 0.35. The similar static pressure recovery coefficient of exhaust diffusers with four kinds of vertical strut airfoils are observed when the inlet pre-swirl is less than 0.48. The static pressure recovery coefficient of exhaust diffusers with vertical b1 and b2 struts are higher than that with the a1 and a2 struts when the inlet pre-swirl is greater than 0.48. At the inlet pre-swirl of 0.35, The static pressure recovery coefficient of the exhaust diffuser with the a1 strut decreases with the increasing of the strut skewed angles. The static pressure recovery coefficient of the exhaust diffuser with the b1 strut increases with the increasing of the strut skewed angles, and the static pressure recovery coefficient increases by 3.6% compared with the vertical design when the skewed angle of b1 strut is 40[Formula: see text]. At the inlet pre-swirl of 0.64. The static pressure recovery coefficient of the exhaust diffuser with the a1 strut increases by 8.7% compared with the vertical design when the skewed angle of a1 strut is greater than 20°. In addition, the static pressure recovery coefficient of the exhaust diffuser with the b1 strut decreases by 3.8% compared with the vertical design when the skewed angle of b1 strut is 40°. The method to improve the aerodynamic performance of the exhaust diffuser by appropriate increase the strut maximum thickness and design the strut skewed angle is proposed in this work.

Currently, thermal insulation of GTU output diffusers uses insulation of their inner surface. This is an expensive and complicated technological procedure. For gas turbines as part of CCGT, in order to reduce the cost of insulation and at the same time increase the useful power of the turbine, cooling the diffuser outer surface with a steam stream of a steam circuit can be an alternative way of internal insulation. Steam and gas parameters of a combined cycle plant with a CCGT-450T, as well as the results of experimental and computational studies of the GTU SGT5-3000E gas turbine exhaust channel model were used. The calculations of the efficiency of the surface cooling of the diffuser with the steam coming from the steam circuit were carried out using the analytical method. A scheme of a superheater located on the outer surface of the GTU outlet diffuser operating in a combined cycle is proposed. Analytic evaluation of its effectiveness showed that the surface area of the GTU diffuser of the type SGT5-3000E is sufficient to provide the necessary overheating of low-pressure steam. Installation of such a heat exchanger using the outer surface of the diffuser provides a decrease of the temperature of its outer wall from 537 to 200 оC. The study validity is confirmed by a patent for an invention. It has been established that the use of the outer surface of the GTU outlet diffuser instead of the heat exchange surface of the low pressure superheater of the utilizer boiler can be applied at CCGT unit to reduce heat and hydraulic losses in the diffuser path and in the utilizer boiler path.

Background. Landfill leachate is a source of environmental pollution and a major concern for human health because it contains high concentrations of organic and inorganic contaminants. Objectives. The objective of the present study is to validate the efficiency of the forced aeration treatment technique, which consists of intensively injecting a continuous oxygen flow of 16.75 kg/m3/h for 30 days using a bubble air diffuser in a relatively small volume of 1 m3. The principle of the technique is essentially based on acceleration of the degradation of the effluent as well as reduction of the organic and nitrogenous matter contents. Methods. Forced aeration technology was used for the treatment of leachate from the Mohammedia-Benslimane landfill. The sample was treated by injecting a flow of oxygen to accelerate the biodegradability of the pollutants by the microorganisms. Results. The physicochemical characterization of the raw leachate at the inlet of the aeration tank showed high values for chemical oxygen demand (COD) (38,600 mg O2/l), biological oxygen demand (BOD5) (24,000 mg O2/l), and total Kjeldahl nitrogen (TKN) (5,932.45 mg/L). The proposed treatment technique allowed relatively high purification yields to be achieved, with abatement rates for the major elements COD, BOD5 and TKN of 73%, 98%, and 85%, respectively. Conclusions. The treatment of leachate by intensive aeration technology reduces considerably the pollutant load and achieves a high purification yield. Competing Interests. The authors declare no competing financial interests.

Ejector-diffuser reduces infrared emissions and are installed in combat aircraft to counter the threat of heat-seeking missile. The specific role of an ejector-diffuser is to reduce the heat emissions without substantially affecting the engine performance. The present study investigates a new design of ejector-diffuser wherein straight-plates and hybrid-straight-plates are installed at each slot for improving the ejector-diffuser performance. The evaluation criteria of an ejector-diffuser is specified in terms of air entrainment through the slots, thermal characteristics, and recovery of pressure. This work is carried out in two stages. In the first part, the orientation of the plate at the slot is investigated by varying the angle between the slot and diffuser axis over the range [Formula: see text]. The overall mass entrainment increases from 2.88 to 4.04 with the increase in plate angle. Further, the thermal characteristics also improves with increase in plate angle, but the pressure recovery decreases from 0.701 to 0.155. In the second part, the straight-plate at the slots are partially/fully replaced by hybrid-plate. Two configurations are proposed by first introducing a hybrid-plate at the first slot and straight-plate at the other slots, and subsequently by introducing hybrid-plate at all the slots. It is found that the pressure recovery in both the cases shows a significant improvement compared to the straight-plate case, the value being close to 0.75 for both the cases. However, the cumulative mass entrained by the first configuration of the hybrid-plate is better than the second configuration and is similar to the straight-plate guidance of 28°. Thus, the current study proposes an IRSS device having the hybrid-plate at the first slot and the straight-plate guidance at the remaining slots which reduces infrared emissions with minimum loading on the engine.

This research focuses on the stage of engineering a technical prototype of a composite wind power plant with a diffuser (WPPD). The area of a particular interest in the article is the mathematical aspect of the engineering stage. The article presents a theoretical study as well as experimental and practical data essential to obtain an effective shape of the diffuser. Here are also given engineering calculations and results of patent researches and field tests. The authors calculate the most rational design parameters capable of ensuring the maximum speed in the area of the blades. This leads to an increase in the generated electricity, since it depends on the speed cubed. The increase in speed is stipulated by the passage of the air flow through the narrow part of the diffuser into the area of expansion and is consistent with the Bernoulli equation. The differential equation relates the flow velocity to the cross-sectional area of the diffuser. It should be noted that its inner part is the surface of rotation of the generatrixes around the axis of the diffuser. The surface shape can be adjusted based on the obtained mathematical calculations. In the research, these curves are described in the form of polynomials of various degrees. After integrating the differential equation for each curve individually the best option is selected. Here is also given an example with a quadratic function, which was experimentally substantiated in earlier researches and is used to compare the effects received from different generators. The described technology, with account taken of the shape of the generator fairings, contributes to the further improvement of the WPPD. The article serves as the basis for engineering a technical prototype of a mobile composite WPPD.

In tea brick fermentation, the temperature in the fermentation chamber has an important influence on the reproduction and growth of the golden flower bacteria inside tea bricks. In order to form a uniform and suitable fermentation temperature, the study introduced an upward vertical wall attached ventilation based on the load distribution characteristics of the tea brick fermentation chamber and the practical placement of tea bricks on the shelf. The air distribution of upward vertical wall attached ventilation under different supply air temperature differences was numerically investigated by a mathematical model of flow and heat transfer. Furthermore, the results were compared with two other traditional ventilation modes, which are diffuser ventilation and displacement ventilation. The upward vertical wall attached ventilation demonstrated higher ventilation efficiency and least vertical temperature stratification due to its lower flow resistance. Thus, the temperature unevenness coefficient in the product area could be reduced by between 54.3% and 77.5% compared with the diffuser dilute ventilation and displacement ventilation. Moreover, the upward vertical wall attached ventilation could help to eliminate the indoor heat load during the fermentation of tea bricks, which increases the energy utilisation rate of supply air by 1.7%–18.5%. Therefore, the vertical wall attached ventilation can effectively improve the temperature distribution of the tea brick fermentation chamber and improve the energy utilisation of the air supply.

Reuse of electronic wastes is a critical aspect for a more sustainable circular economy as it provides the simplest and most direct route to extend the lifespan of non-renewable resources. Herein, the distinctive surface and micro topographical features of computer electronic-plastic (E-plastic) scraps were unconventionally repurposed as a substrate material to guide the growth and differentiation of human adipose-derived mesenchymal stem cells (ADSCs). Specifically, the E-plastics were scavenged from discarded computer components such as light diffuser plate (polyacrylates), prismatic sheet (polyethylene terephthalate), and keyboards (acrylonitrile butadiene styrene) were cleaned, sterilized, and systematically characterized to determine the identity of the plastics, chemical constituents, surface features, and leaching characteristics. Multiparametric analysis revealed that all the E-plastics could preserve stem-cell phenotype and maintain cell growth over 2 weeks, rivalling the performance of commercial tissue-culture treated plates as cell culture plastics. Interestingly, compared to commercial tissue-culture treated plastics and in a competitive adipogenic and osteogenic differentiation environment, ADSCs cultured on the keyboard and light diffuser plastics favoured bone cells formation while the grating-like microstructures of the prismatic sheet promoted fat cells differentiation via the process of contact guidance. Our findings point to the real possibility of utilizing discarded computer plastics as a "waste-to-resource" material to programme stem cell fate without further processing nor biochemical modification, thus providing an innovative second-life option for E-plastics from personal computers. National Environmental Agency (NEA) National Research Foundation (NRF) This research is supported by the National Research Foundation, Singapore, and National Environment Agency, Singapore under its Closing the Waste Loop Funding Initiative (Award No. USS-IF-2018-4).

Fast speckle suppression is crucial for time-resolved full-field imaging with laser illumination. Here, we introduce a method to accelerate the spatial decoherence of laser emission, achieving speckle suppression in the nanosecond integration time scale. The method relies on the insertion of an intracavity phase diffuser into a degenerate cavity laser to break the frequency degeneracy of transverse modes and broaden the lasing spectrum. The ultrafast decoherence of laser emission results in the reduction of speckle contrast to 3% in less than 1 ns.

The extraction of sucrose in a cane diffuser depends mainly on the percolation rate, and its optimisation requires the monitoring and control of the liquid holdup with the cane bed. However, most c...

Naturally stratified technology is the most economical and effective method in chilled water storage technique and its core is the design of water diffuser. The better the performance of diffuser a...

Optical diffusion is an essential photon management process for various photoelectronic systems. This work proposes an approach to fabricate optical diffuser by interfacial hydrogen-bonding polymer...

The computational experiments were carried out on the model of butadiene polymerization (toluene as a solvent) in the presence of TiCl4–Al(i-C4H9)3 catalytic system, physically modified in turbulent flows. It was shown that, the higher is the feed rate of reaction mixture into the tubular turbulent apparatus with diffuser-confuser design, and the larger is the ratio of the diffuser diameter to confuser diameter, and the greater is the diffuser opening angle, the lower are the number-average and mass-average molar masses of polybutadiene. These values of number-average and mass-average molar masses of obtained polybutadiene under upper conditions allows using it as a polymer component of sticky glue.

A diffuser is a mechanical device used for converting the kinetic energy of flowing fluid into pressure energy. As the flow advances through the diffuser there is ongoing retardation of the flow resulting in conversion of kinetic energy into pressure energy. This is known as diffusion. Diffuser constitutes an essential part in turbo machinery and engineering structures. The present study aims at CFD analysis for the prediction of flow characteristics using various mathematical models. The annular diffuser considered in the present case has both the hub and casings are diverging with equal angles and hub angle keeping constant as 10°. The characteristic quantity such as velocity profiles at various sections and flow patterns have been presented for studying. Standard turbulence models are studied in the present study.

Passive infrared (IR) suppression device, commonly known as ejector diffuser, is an integral part of the defence system of a ship. The definitive role of passive IR suppressor to counter the IR tracking and locking of the ship has made them indispensable for any combat marine. The gas turbine exhaust gases are the leading heat source on a ship. The exhaust temperature of the gases ranges between 650K-850K. At such temperatures, the ship can be easily detected by the enemy through IR imaging. The role of the ejector diffuser is to (i) lower the gas turbine exhaust gases temperature to the limits (< 450K) such that the IR locking of the marine can be avoided, and (ii) recover static pressure such that the engine performance of the gas turbine is not affected. Ejector diffuser has the ability to entrain ambient air and allow mixing it with the exhaust gases thereby, lowering the temperature of the exhaust gases. However, the mixed exhaust gases temperature depends on the ambient air temperature which under extreme conditions can fluctuate from 273K to 323K. This temperature range can affect the temperature characteristics of an ejector diffuser. The present study undertakes the effect of ambient temperature on the performance of inline-slot ejector diffuser. The ambient temperature (T0) has been varied in the range 273K ≤ T0 ≤ 323K in the step of 10K. It has been found that the mass entrainment increases (≈ 8%) as the ambient temperature decreases. The core temperature at the exit decreases, from 457.58 K to 417.75K, with a decrease in the ambient temperature. However, no significant changes in static pressure recovery.

A numerical simulation of the heat transfer in plate heat exchangers with diffuser channels with small opening angles was performed with a three-parameter differential turbulence model supplemented by the transport equation for a turbulent heat flux. It is shown that the amount of heat transferred from the “hot” coolant to the “cold” increases as compared that in heat exchangers with channels with a constant cross section due to the heat-transfer enhancement in heat exchangers with diffuser channels.

Fuel cell based power generation systems have gained remarkable interest in this modern age, due to its high conversion efficiency and reliability. Among the different types of fuel cells, PEM fuel cells are achieving more significance due to its fast start up time and low operating temperature. This paper studies the mathematical model of proton exchange membrane of fuel cell (PEMFC) using Matlab/SIMULINK software. The paper consists of the calculation of cell voltage, stack current, ohmic loss, activation loss. This model is used to research the fuel cell behavior and the characteristic of output values at different parameters. The model consists of the cathode gas channel, gas diffuser, catalyst layer, and the membrane. In order to composite shape of the gas diffuser and for its gradient in liquid water content, the gas diffuser is modeled as a series of parallel layers with different porosity. It represents in terms of the physical and thermodynamic parameters of the fuel cell. The curve of polarization is expressed parametrically as a function of the surface over potential. This paper expresses for cathode internal as well as overall effectiveness factors, active fraction of the catalyst layer resistance, catalyst layer, limiting current density, and the slope of the polarization curve.

The article presents the analysis of the interactions between the impeller and the vaned diffuser of a radial flow pump. The tests were carried out on the so-called SHF impeller, coupled with a vaned diffuser, and working with air. The particularity of this machine is that the diffuser design flow rate corresponds to 80% of the impeller one. All experimental works were performed at the Fluid Mechanics Laboratory in ENSAM, Lille, France. Investigations have been made for five different flow rates. Global performances of the machine are evaluated thanks to pressure measurements and averaged velocities obtain with a three hole probe, at nine angular positions at diffuser inlet and outlet just as five radial positions in a middle section of a blade-to-blade passage. A post-processing procedure, based on statistical tools, was applied to the experimental results in order to reach a better understanding of the phenomena. In another approach, a numerical simulation of the flow inside the pump, for eight different relative angular positions of the diffuser relative to the impeller (Frozen rotor) was performed by the STAR-CCM+ software. The experimental results were compared to numerical data obtained with the help of STAR-CCM+ computer code.

The paper elaborates on promoting the strength of self-organizing large-scale vortical structures in diffuser dimples aimed at heat transfer enhancement in cooled turbine blades. Conditions, under which the extended diffuser length is formed in the reverse flow inside the dimple, are revealed.