A systematic review and analysis of the literature of diffuser-augmented horizontal-axis turbines are presented. A collection of 155 articles in the area is analyzed and classified. The work sample ...is divided into 16 main research branches for discussion. Performance assessment metrics are proposed based on power coefficient and tip-speed-ratio, to quantify and compare all diffuser-augmented turbines in a unified, meaningful manner. Design suggestions for the development of diffuser-augmented turbines are pointed out based on the analysis of 73 cases. A power coefficient assessment on the work sample presented that, in 58% of the cases, the diffuser-augmented turbines surpassed the power coefficient of scaled bare turbines of the same diameter. A tip-speed-ratio assessment presented that almost 90% of the diffuser-augmented turbines developed a narrower operational interval. Five high-performing diffuser-augmented turbines are discussed, highlighting their methodologies and contributions. Caution is advised when coupling a diffuser to a bare turbine with an already high power coefficient; the diffuser-augmented turbine, especially in those cases, should be designed employing a simultaneous diffuser-rotor optimization.
•Systematic analysis of the current literature on diffuser-augmented horizontal-axis turbines is made.•A collection of 155 articles is dived in 16 research branches and discussed.•A diffuser-enhancement parameter is defined and used to compare the effectiveness of diffusers.•In 58% of the DAHT analyzed, the diffuser increases the Cp when compared to a bare turbine scaled to the diffuser diameter.•Diffuser-augmented horizontal turbines tend to display narrower Cp versus TSR curves compared to its bare version.
This Paper mainly analyze the influence of diffuser on the polarization of backlight. The influencing factors of diffuser was studied in detail. The results indicate that PET, PET‐thickness and upper ...coating are the main factors, and the transmittance can be improved by rotating diffuser at a specific angle.
This paper presents an investigation into the effect of area ratio parameter of diffusers on its energy output through power coefficient C
. This parameter has effect both on diffusers' energy yield, ...besides diffuser's size for architectural integration prospects. A systematic increase in diffusers area ratio is adopted following standardized diffuser profile presented by NACA 1244 aerofoil. A series of area ratios were investigated (i.e., 1.25, 1.5, 1.75, 2, 2.5, 3 and 3.5). Area ratio of 1.5 (i.e., outlet/inlet, 0.75 m/0.50 m) exhibited the highest power coefficient C
of 4.2, in addition to achieving highest resulting velocity of 25.8 m/s under incident velocity of 16m/s. Considerable wind separation inside inner walls of diffusers occurred from area ratio 1.75 onwards, which impacted resulting velocities. Simulations performed with ANSYS CFD Academic to standalone diffusers. A series of incident velocities employed from 1 to 16 m/s that resulted in velocity increase by 120-156% respectively.
Computational analysis is performed on a centrifugal compressor fitted with tapered vaneless diffuser in order to increase the rate of diffusion. The main parameter involved in the present study is ...the wall taper angle of the diffuser, which is varied from 1° to 6° in the interval of 1°. Simulations are performed for the stationary as well as rotating diffuser at a speed of 79,000rpm, by using ANSYS CFX 17.2. By considering the geometry with stationary parallel wall diffuser as the base case, the performance enhancement in the characteristics such as static pressure recovery coefficient, stagnation pressure loss coefficient, isentropic efficiency, energy coefficient and torque coefficient are reported. The flow features in the compressor having various diffuser geometries are studied with the help of static pressure, radial velocity, static entropy, and contours of velocity streamlines at the design point. Of all the cases of stationary tapered diffusers, the diffuser with 3° taper angle showed optimum performance: the increase in isentropic efficiency (η) is by 1.5%, the increase in static pressure recovery coefficient (CP) is by about 9% and the decrease in stagnation pressure loss coefficient (CPOL) by 10.7%. On the other hand, it was found that in the case of rotating diffuser optimum performance: an increase of about 40% in CP and decrease of about 32% in CP0L occurred for a taper angle of 6°. However, its efficiency decreased by 2.9% with rotating diffuser in comparison with the base case, due to increased energy losses.
Human-aware HAVC operations have been shown to be effective in improving energy efficiency, which is constrained by the HVAC system configuration and operational logic. These constraints can result ...in a lack of operational flexibility, which in turn reduces the adaptation capacity for energy efficiency. Therefore, in this study, we investigated the energy efficiency implications of novel adaptive capacities for HVAC including the use of proposed active diffusers, which add to the dynamics of the HAVC systems by adjusting the behavior of diffusers using two modalities of (1) binary actuation of air flow (turning flow on and off), and (2) adjusting the flow direction to target individual needs in an environment. Computational fluid dynamics was used to model and simulate the behavior of a “real-world” thermal zone to evaluate five scenarios of adaptive operations using distributed feedback from the environment, as well as active diffusers. Three scenarios used binary actuation at the thermal zone (collection of rooms) level, and two examined the adaptive operations at the diffusers level. Moreover, we examined the integration of distributed feedback at occupant locations into the control loop using averaged temperatures (in the first three scenarios) and individual-level feedback (in scenarios with diffuser level actuation). The coupling of distributed feedback and independent directional flow at the diffuser level considerably improved thermal comfort while reducing energy demands by ~25%—reflecting a considerable impact on improved energy efficiency. These findings demonstrate the potentials that artificial intelligence frameworks could bring about by enabling autonomous adaptive operations.
•Investigated the energy efficiency implications of novel adaptive HVAC operations.•Introduced the concept of active diffusers that increase diffuser flexibility.•Expanded flexibility by directional flow, binary actuation, and distributed sensing.•Binary-controlled directional flow with distributed feedback was the most effective.•Improved the thermal comfort and reduced energy demands by almost 25%.
Aqua MODIS has successfully operated on-orbit for more than six years since its launch in May 2002, continuously making global observations and improving studies of changes in the Earth's climate and ...environment. Twenty of the 36 MODIS spectral bands, covering wavelengths from 0.41 to 2.2 ?m, are the reflective solar bands (RSBs). They are calibrated on-orbit using an onboard solar diffuser (SD) and an SD stability monitor. In addition, regularly scheduled lunar observations are made to track the RSB calibration stability. This paper presents Aqua MODIS RSB on-orbit calibration and characterization activities, methodologies, and performance. Included in this paper are characterizations of detector signal-to-noise ratio, short-term stability, and long-term response change. Spectral-wavelength-dependent degradation of the SD bidirectional reflectance factor and scan mirror reflectance, which also varies with the angle of incidence, is examined. On-orbit results show that Aqua MODIS onboard calibrators have performed well, enabling accurate calibration coefficients to be derived and updated for the Level 1B production and assuring high-quality science data products to be continuously generated and distributed. Since launch, the short-term response, on a scan-by-scan basis, has remained extremely stable for most RSB detectors. With the exception of band 6, there have been no new RSB noisy or inoperable detectors. Like its predecessor, i.e., Terra MODIS, launched in December 1999, the Aqua MODIS visible spectral bands have experienced relatively large changes, with an annual response decrease (mirror side 1) of 3.6% for band 8 at 0.412 ?m, 2.3% for band 9 at 0.443 ?m, 1.6% for band 3 at 0.469 ?m, and 1.2% for band 10 at 0.488 ?m. For other RSB bands with wavelengths greater than 0.5 ?m, the annual response changes are typically less than 0.5%. In general, Aqua MODIS optics degradation is smaller than Terra MODIS, and the mirror-side differences are much smaller. Overall, Aqua MODIS RSB on-orbit performance is better than that of Terra MODIS.
In this paper, a novel air bleeding aerodynamic diffuser is proposed based on the study of the traditional dump diffuser. The performance and flow characteristics of these two diffusers are compared ...and analyzed using the numerical simulation method, which is validated by experiments. The effects of length and hole diameter on the diffuser’s performance are also studied. The results reveal that, at inlet Mach numbers of 0.15, 0.20 and 0.30, compared with the dump diffuser, the total pressure loss coefficient of the new diffuser decreases by 18.52 %, 15.05 % and 40.23 %. The performance of the air bleeding aerodynamic diffuser with varing lengths has little change, which means its aerodynamic capabilities are still capable of meeting the requirements of advanced combustion chambers. As the diameter of the air bleed hole increases, the total pressure loss coefficient of the diffuser decreases and becomes gentler.
Abstract
While numerical aperture of transillumination at or above 1.25 can be achieved with a substage oiled Abbe condenser, such immersion‐capable condensers can be expensive limiting their use in ...resource poor settings. Also the measurement of numerical aperture generated by illuminators has received relatively little attention in the literature compared to methods for measuring the numerical aperture of acceptance by objectives. In this article, I show how an inexpensive paper diffuser with refractive‐index coupling to the sample slide can generate illumination of a numerical aperture of over 1.4 at a small fraction of the cost of oiled dioptric condensers of comparable numerical aperture. In addition, I present two ways in which a diffuser may also be used to measure the numerical aperture generated by an illuminator using either a calibrated index‐coupled paper diffuser to implement an interpolative variation of the Horsfall method or a diffuser as a detector screen coupled to a self‐built microscope slide‐based illumination system apertometer.
LAY DESCRIPTION
The highest magnifications of light microscopy require immersion objectives that, in turn, require extremely wide‐angle illumination of the specimen to make maximum use of the spatial resolving power of these objectives. However, providing such illumination involves the use of expensive condenser lens arrangements. This article shows how a similar wide angle of illumination can be achieved using a diffuser made of paper that is optically coupled to the specimen slide with an immersion medium. Furthermore, measuring the capabilities of a wide‐angle illuminating device usually involves expensive specialist optical laboratory equipment. This article also shows how such measurements can be made using simple inexpensive self‐built apparatus with the aid of a diffuser. These techniques make the study and use of high‐magnification, high‐resolution light microscopy more accessible to those with limited resources.
Chilled water energy storage using thermal stratification technique currently used in the vast area because it contributes to reducing energy consumption and refrigeration capacity as well as its ...maintenance, operating and capital costs are low. In this paper, experimental tests were carried out on a small-scale vertical cylindrical storage tank equipped with an elbow-type conventional diffuser at inlet heights of 20, 170, 320 and 470mm for flow charging rates from 1.5-7.5l/min. in order to obtain a good thermal separation. The degree of stratification was estimated by means of temperature distributions and performance metrics, which involve thermocline thickness, the half-cycle figure of merit and equivalent lost tank height. The results show that the decrease in diffuser height above the tank floor tends to the steep thermocline or satisfactory thermal separation, the stratification and thermal performance were obtained at diffuser height of 20 mm within the limiting volume flow rates 1.5-4.5 l/min. better than those at volume flow rates ranging from 5.5-7.5l/min. and much better than at diffuser heights of 170, 320 and 470mm for various flow rates.
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