Small Fan Research Articles

Chatham Fan and adjacent upper Baranof Fan channels and levee, US Gulf of Alaska margin

The Chatham Fan (Fig. 1b, c), a relatively small submarine fan, was mapped as part of the University of New Hampshire's Center for Coastal & Ocean Mapping effort to collect multibeam-bathymetric and backscatter data in support of the US Extended Continental Shelf (United Nations Law of the Sea Convention) project (Gardner & Mayer 2005). It has buried a portion of the head of the much larger Baranof Fan (Stevenson & Embley 1987; von Huene 1989; LeVoir et al. 2011) on the US Gulf of Alaska continental margin. Chatham Fan also either buried the upper reaches of Horizon Channel or diverted it northwestwards. The existing levee of upper Horizon Channel was subsequently incised by a well-developed meandering channel that trends along the strike of the levee, not down the steeper lee side of the levee slope. The meandering levee channel is related indirectly to processes that were contemporaneous with the deposition of Chatham Fan. Fig. 1. Multibeam-bathymetric and backscatter imagery, and a CHIRP sub-bottom profile of the Chatham and upper Baranof fans, Gulf of Alaska. ( a ) Location of the study area (red box; map from GEBCO_08). The …

Performance Comparison of Destratification Fans for Large Spaces

Ceiling fan is proven to have a beneficial effect on increasing air velocity and reducing temperature stratification and thus saving energy for high ceiling applications. Studies show that the velocities produced by large diameter, ceiling mounted fans do not produce a negative or positive effect on human comfort. Recently, smaller, high velocity fans have been introduced to the market as an alternative to these large diameter fans that provides similar energy savings due to reduced destratification, while still not moving the air fast enough to cause human discomfort, though these products have been studied less. This study simulates and compares the performance of both large and small diameter fans using a validated computational fluid dynamics (CFD) model. Two different types of destratification fans are investigated for their performance in destratifying the air temperatures in warehouse style retail stores. A portion of a retail store is used as a base to create the test environment. Simulations show that the small diameter high speed fan (SDHSF) is very good at bringing a well-mixed column of air all the way to the floor, but the spaces without a fan directly overhead are hardly affected. The large diameter low speed fans (LDLSF) are able to mix nearly the entire space, though they created uncomfortable drafts near head height. Between these two fans, the LDLSF is more successful at destratifying the entire space, though the SDHSF is better at only destratifying a specific, smaller area. Varying the speed of the LDLSF also allows for successful destratification, while maintaining acceptable draft velocities.

Temperature rise in induction motor windings as the cause of variation in rotational speed of an axial fan

The paper presents results of an experimental investigation performed under controlled laboratory conditions, in order to identify real causes of variation in the rotational speed of an axial fan that can be noticed after a certain period following the start of operation. The theoretical background important for understanding the observed phenomenon is given and the hypothesis is proposed which states that the temperature rise in motor windings and a consequential rise of their resistances are responsible for such specific behavior of the axial fan. The experiment was performed on a standard test rig with a small industrial axial fan, driven by a three-phase induction motor with the rated power of 1.5 kW. The experimental procedure is described in details, measured and calculated results are presented and appropriate conclusions are given. The obtained experimental results confirm the proposed hypothesis.

Investigation of aerodynamic performance of small axial flow fan coupled with deflecting ring

Experimental and numerical investigations on the effect of deflecting rings featuring different axial lengths on aerodynamic performance of the small axial flow fan were conducted under the condition of maximum flow rate. Two deflecting rings, the semi-open type and closed type, were investigated. Aerodynamic and aeroacoustic performances have been measured in experiment, and key analysis of flow was based on computational fluid dynamics results. The numerical and experimental results show that the deflecting ring has great influence on the performance of an axial flow fan. For the semi-open-type deflecting ring, the fan has better P-Q performance and higher efficiency; pressure, vorticity, and vorticity gradient distributions on the blade surface are more uniform; and noise level of the fan is lower at wider frequency bands. For the closed-type deflecting ring, the performance curve has a convex feature; blade pressure difference between the pressure surface and the suction surface is much bigger. The result shows that better aerodynamic and aeroacoustic performances of the axial flow fan can be acquired when the semi-open-type deflecting ring is adopted.

Multidisciplinary constraints of hydrothermal explosions based on the 2013 Gengissig lake events, Kverkfjöll volcano, Iceland

Hydrothermal explosions frequently occur in geothermal areas showing various mechanisms and energies of explosivity. Their deposits, though generally hardly recognised or badly preserved, provide important insights to quantify the dynamics and energy of these poorly understood explosive events. Furthermore the host rock lithology of the geothermal system adds a control on the efficiency in the energy release during an explosion. We present results from a detailed study of recent hydrothermal explosion deposits within an active geothermal area at Kverkfjöll, a central volcano at the northern edge of Vatnajökull. On August 15th 2013, a small jökulhlaup occurred when the Gengissig ice-dammed lake drained at Kverkfjöll. The lake level dropped by approximately 30 m, decreasing pressure on the lake bed and triggering several hydrothermal explosions on the 16th. Here, a multidisciplinary approach combining detailed field work, laboratory studies, and models of the energetics of explosions with information on duration and amplitudes of seismic signals, has been used to analyse the mechanisms and characteristics of these hydrothermal explosions. Field and laboratory studies were also carried out to help constrain the sedimentary sequence involved in the event. The explosions lasted for 40–50 s and involved the surficial part of an unconsolidated and hydrothermally altered glacio-lacustrine deposit composed of pyroclasts, lavas, scoriaceous fragments, and fine-grained welded or loosely consolidated aggregates, interbedded with clay-rich levels. Several small fans of ejecta were formed, reaching a distance of 1 km north of the lake and covering an area of approximately 0.3 km2, with a maximum thickness of 40 cm at the crater walls. The material (volume of approximately 104 m3) has been ejected by the expanding boiling fluid, generated by a pressure failure affecting the surficial geothermal reservoir. The maximum thermal, craterisation and ejection energies, calculated for the explosion areas, are on the order of 1011, 1010 and 109 J, respectively. Comparison of these with those estimated by the volume of the ejecta and the crater sizes, yields good agreement. We estimate that approximately 30% of the available thermal energy was converted into mechanical energy during this event. The residual energy was largely dissipated as heat, while only a small portion was converted into seismic energy. Estimation of the amount of freshly-fragmented clasts in the ejected material obtained from SEM morphological analyses, reveals that a low but significant energy consumption by fragmentation occurred. Decompression experiments were performed in the laboratory mimicking the conditions due to the drainage of the lake. Experimental results confirm that only a minor amount of energy is consumed by the creation of new surfaces in fragmentation, whereas most of the fresh fragments derive from the disaggregation of aggregates. Furthermore, ejection velocities of the particles (40–50 m/s), measured via high-speed videos, are consistent with those estimated from the field. The multidisciplinary approach used here to investigate hydrothermal explosions has proven to be a valuable tool which can provide robust constraints on energy release and partitioning for such small-size yet hazardous, steam-explosion events.

Green-diode-pumped femtosecond Ti:Sapphire laser with up to 450 mW average power.

We investigate power-scaling of green-diode-pumped Ti:Sapphire lasers in continuous-wave (CW) and mode-locked operation. In a first configuration with a total pump power of up to 2 W incident onto the crystal, we achieved a CW power of up to 440 mW and self-starting mode-locking with up to 200 mW average power in 68-fs pulses using semiconductor saturable absorber mirror (SESAM) as saturable absorber. In a second configuration with up to 3 W of pump power incident onto the crystal, we achieved up to 650 mW in CW operation and up to 450 mW in 58-fs pulses using Kerr-lens mode-locking (KLM). The shortest pulse duration was 39 fs, which was achieved at 350 mW average power using KLM. The mode-locked laser generates a pulse train at repetition rates around 400 MHz. No complex cooling system is required: neither the SESAM nor the Ti:Sapphire crystal is actively cooled, only air cooling is applied to the pump diodes using a small fan. Because of mass production for laser displays, we expect that prices for green laser diodes will become very favorable in the near future, opening the door for low-cost Ti:Sapphire lasers. This will be highly attractive for potential mass applications such as biomedical imaging and sensing.

On Decentralized Air-conditioning for Hot and Humid Climates: Performance Characterization of a Small Capacity Dedicated Outdoor Air System with Built-in Sensible and Latent Energy Recovery Wheels

In large commercial buildings facing high cooling loads, conventional heating, ventilation, and air-conditioning (HVAC) systems are typically based on the use of one, or few, large-capacity air handling units (AHUs) to supply conditioned air throughout a centrally-managed air distribution network. The alternative concept of ‘decentralized’ HVAC typically entails the deployment of multiple, small capacity fan coil units (FCUs) operating as dedicated outdoor air systems (DOAS) and located closest to the individual thermal zones they must condition. For this study, the authors commissioned the development of a small capacity, packaged cooling coil with built-in enthalpy recovery devices. This customised unit, intended for use in a cooling-only, decentralized DOAS configuration, includes: two rotary wheels for sensible and latent energy recovery, a single cooling coil, and both supply and exhaust fans. The unit has been intended for building air conditioning use in the Singaporean climate. This paper provides energy performance data based on laboratory testing of the unit with independent control of the following variables: outdoor air conditions, return air conditions, and chilled water flow rate. It is intended that empirical data offered by this study can be adapted for use in future building energy models of decentralized HVAC systems.

Noise control of dipole source by using micro-perforated panel housing

Mitigating low-frequency noise in a small ducted fan system such as hairdryer is still a technical challenge. Traditional duct lining with porous materials work ineffectively due to the limitation of its thickness and length of small domestic product with ducted fans. This study presents a passive approach to directly suppress the sound radiation from the fan housed by a short microperforated panel covered with a shallow cavity backing. The noise suppression is achieved by the sound cancellation between sound fields from a fan of a dipole nature and sound radiation from a vibrating panel via vibro-acoustic coupling and by sound absorption in micro-perforations to widen the stopband. A two-dimensional theoretical model, capable of dealing with strong coupling among the vibrating micro-perforated panel, sound radiation from the dipole source, sound fields inside the cavity and the duct is developed. Through modal analysis, it is found that the even modes of the panel vibration are very important to cancel the sound radiation from the dipole source. Experimental validation is conducted with a loudspeaker to simulate the dipole source, and good agreement between the predicted and measured insertion loss (IL) is achieved.

Using air movement for comfort during moderate exercise

Fitness centers are energy-intensive in warm climates, cooling the interior to low temperatures that are comfortable for exercise. There is little existing guidance on how to do this efficiently. However it is well-known that significant energy can be saved by cooling sedentary occupants with air movement at elevated setpoint temperatures. This experiment investigated thermal comfort and air movement at elevated activity levels. Comfort votes were obtained from 20 subjects pedaling a bicycle ergometer at 2, 4, and 6 MET exercise intensities in four temperatures (20, 22, 24, 26 °C, RH 50%) under personal controlled ceiling fan airflow, as well as in a 20 °C still-air reference condition. An additional test of frontal airflow was conducted at 26 °C. The hypothesis, that air movement together with higher temperatures would produce equal or better comfort and perceived air quality below the reference condition, was confirmed for every temperature up to 26 °C. Subjects preferred air speeds up to 2.3 m/s to maintain acceptable thermal environment at 6 MET. The small frontal fan affecting the facial area was effective but the ceiling fan affecting the whole body provided greater comfort. Fitness centers should operate with elevated air movement to improve both comfort and efficiency.

English

Nowadays in the era of Intelligent Systems; a smart fan is very much essential to the concept of “Smart Homes”. Thus taking in view of the recent developments in home automation we developed a circuit which tracks the presence of person in a room. Most of the previous researches included IR and PIR sensors as the tracking sensor. Performance of Infrared sensors has traditionally been limited by their poor tolerance to light reflections such as ambient light or bright object colors. The Passive Infrared sensors have tolerance problems with temperature limit values. But ultrasonic distance sensors do not have gaps in the coverage zone like a PIR sensor and overall detection range is comparable to that of a PIR sensor. Thus in this paper we suggested the use of ultrasonic sensor module to measure the distance between the human and based on the pre-defined setpoints we have varied the speed of a small fan in the prototype . AT89s51 microcontroller and the ultrasonic transducer module HC-SR04 forms the basis of this circuit. The ultrasonic module sends a signal to the object, then picks up its echo and outputs a wave form whose time period is proportional to the distance. The microcontroller accepts this signal, performs necessary processing and varies the intensity of the fan. We also depicted a concept where these sensors can be attached to overhead ceiling fans propose use of Maximum length sequence (MLS) diffusors for sensing a 360 degree circumference beneath the fan and a thermostat to maintain the temperature in the room.

Irregular plate boundary controls on Foreland Basin sedimentation (Miocene, Kahramanmaraş Foreland Basin, SE Turkey)

The northern movement of the Arabian Plate led to the development of a compressional regime in the south-eastern part of Turkey after the Late Cretaceous. The collision of the Arabian Plate with the Anatolide–Taurides Platform and subsequent development of the Kahramanmaraş Foreland Basin at the beginning of the Miocene evolved as a result of this movement. An irregular plate geometry or promontory of the Arabian Plate caused partitioning of the plate margin (precollision–collision–postcollision). This irregular plate boundary was delimited by western and northern boundary faults and an interior basin fault. The NW-oriented small wedge top basins on the overlying Anatolide–Taurides Platform obliquely cut through the foredeep basin. The region (across the wedge top basin) on the irregular promontory of the underlying Arabian Plate contains different sedimentation depocentres. Small fining-upward submarine fan deposits (including pebbly channel deposits and coarsening-upward lobe sequences) are located at the centre of the irregular part of the plate (in the Tanır region) and overlie planktic foraminifera-bearing claystones. These submarine fan sediments pass outboard into distal interbedded turbidite claystones and siltstones in a downdip direction (S-SE). The boundary fault intersection of the promontory led to the development of a submarine slope environment with irregular sea-floor topography in the Fırnız area (4–5km south-east of the Tanır region). The slump deposits, sandy debrites, and fine-grained thin-bedded turbidites filled this region. Structural alignments and seismicity associated with the plate margin were the main controlling factors on the geometry of the depocentre, sediment quantity, sediment input, sedimentary facies, local sea level changes, and post-sedimentary deformation in the Kahramanmaraş Foreland Basin.

Functionalized Multi-Walled Carbon Nanotubes As Supporting Matrix for Enhancement Oxidation of Fucose on Gold Nanoparticle-Based Catalyst

Biomass extracted from brown macro-algae promises as a future renewable energy because of non-toxicity, natural availability, greenhouse gas free, and do not interfere with the human food chain. Here, we first present the extraction of energy from brown macro-algae via direct oxidation of fucose using anodic catalytic composite material of gold nanoparticles (AuNPs) sintered on functionalized multi-walled carbon nanotubes (f-MWCNTs). The combination of AuNPs/f-MWCNTs showed super catalytic activity on fucose oxidation in compare to AuNPs and f-MWCNTs only. The oxidation peak of fucose shifted to more negative peak by using AuNPs/f-MWCNT/C in compare to Au/C electrode only, while almost there is no peak can be observed in the case of f-MWCNT/C electrode. The direct fucose fuel cell performance by using AuNPs/f-MWCNT/C electrode as the anode resulted in power density of 1.923 mW cm-2, is much more higher than 0.658 mW cm-2 of AuNPs/C and 0.028 mW cm-2 of f-MWCNT/C. A small air - fucose fuel cell using 1 cm2 anode can run a LED lamp. Furthermore, a fuel cell using 16 cm2 anodic electrode modified by AuNPs/f-MWCNT with 3 mL fuel solution can keep a small fan running for at least 3 hours. The results from this research open possibility for practical application of our fuel cell with high efficiency on conversion of energy from brown macro-algae biomasses.

Design Constraints of Small Single-Phase Permanent Magnet Brushless DC Drives for Fan Applications

Permanent magnet brushless dc (BLDC) machines are widely used due to various advantages such as high efficiency and high torque density, and therefore compactness as well as long expected lifetime. All of these benefits are of major interest when designing a drive for a small fan application of a few watts. This paper presents the design investigations of a small single-phase BLDC motor for such an application. Notably, it discusses different constraints which arise during the design process and which may be of special relevance due to the particular given power level and application.

Development of Electronic Nose with Low-Cost Dynamic Headspace for Classifying Vegetable Oils and Animal Fats

A portable electronic nose (e-nose) using low-cost dynamic headspace and commercially metal oxide gas sensors has been developed. This paper reports evaluation on the performance of the e-nose to classify vegetable oils (sunflower and grape seed oils) and animal fats (mutton, chicken and pig fats). The e-nose consists of a dynamic headspace sampling, a gas sensor array and a real-time data acquisition system based on ATMega-16 microcontroller. The dynamic headspace can divided into two chambers, i.e. sample and gas sensor array room. It is also equipped with three small fans for adjusting sensing and purging processes. Principal component analysis (PCA) was used for measurement data analysis after all features being extracted. The first two principal components were kept because they accounted for 91.1% of the variance in the data set (first and second principals accounted for 72.9, 18.2% of the variance, respectively). This results show that the e-nose can distinguish vegetable oils and animal fats. This work demonstrates for the future that the e-nose with low-cost dynamic headspace technique may be applied to the identification of oils and fats in halal authentication.

Influence of Chord Lengths of Splitter Blades on Performance of Small Axial Flow Fan

On the basis of small axial fan with five blades, 6 types of small axial flow fans with different chord lengths splitter blades were designed. Numerical simulation of 6 fan models with splitter blades and prototype fan were done by using Fluent. Based on the obtained simulation results, internal flow characteristics and aerodynamic noise were analyzed and compared. It indicates that: splitter blades with suitable chord length have improved significantly on internal flow characteristics, which inhibits backflow from pressure surface to the suction surface at blade tip and leading edge and restrains flow separation. The 6 model fans are better than prototype fan on aerodynamic noise improvement, but too long or too short chord lengths are both disadvantage to improve aerodynamic noise. The results reveal that 2/6, 3/6 and 4/6 chord length model have relatively better acoustic characteristics and internal flow characteristics. The research program will offer a reference for structural improvements and noise reduction on small axial flow fan.

Effects of perforation number of blade on aerodynamic performance of dual-rotor small axial flow fans

Compared with single rotor small axial flow fans, dual-rotor small axial flow fans is better regarding the static characteristics. But the aerodynamic noise of dual-rotor small axial flow fans is worse than that of single rotor small axial flow fans. In order to improve aerodynamic noise of dual-rotor small axial flow fans, the pre-stage blades with different perforation numbers are designed in this research. The RANS equations and the standard k-ɛ turbulence model as well as the FW-H noise model are used to simulate the flow field within the fan. Then, the aerodynamic performance of the fans with different perforation number is compared and analyzed. The results show that: (1) Compared to the prototype fan, the noise of fans with perforation blades is reduced. Additionally, the noise of the fans decreases with the increase of the number of perforations. (2) The vorticity value in the trailing edge of the pre-stage blades of perforated fans is reduced. It is found that the vorticity value in the trailing edge of the pre-stage blades decreases with the increase of the number of perforations. (3) Compared to the prototype fan, the total pressure rising and efficiency of the fans with perforation blades drop slightly.

A thermal management device for a lower-limb prosthesis

Excessive heat and the resulted perspiration within a prosthetic socket were the most common causes for reporting a reduced quality of life for prosthesis users. This paper presents a novel thermal management device to maintain a constant skin temperature for a lower-limb prosthesis. To decrease the prosthetic socket's thermal resistance, heat pipes were used to concentrate heat flux from the simulated skin surface to a cooling region on the outer surface of the socket where a compact heat sink was attached. A small fan was used to convect heat from the heat sink to the ambient surroundings. Thermal resistance of the cooling device was adjusted to match various thermal loads by changing the fan power. Experiments showed that cooling capacity of the prototype device ranges from 2.1 W to 7.0 W at an ambient temperature of 23.0 °C. The automatic control mode to maintain a constant skin temperature was also demonstrated. Further analysis showed that the device can potentially maintain a constant skin temperature for a thermal load as large as 9.4 W. The compact size, quiet operation and heat removal capability make the device suitable for maintaining a comfortable and healthy thermal environment inside the prosthesis socket.

Large-scale chamber investigation and simulation of phthalate emissions from vinyl flooring

This study investigated phthalate emissions from vinyl flooring in a large-scale chamber. Vinyl flooring materials were examined for their phthalates content; one with high contents of diisononyl phthalate (DINP) and di(2-ethylhexyl) phthalate (DEHP) was selected for emissions testing in a small chamber at two different temperatures. Using the same type of vinyl flooring, large-scale chamber experiments were then conducted in three testing phases. In the first phase, the gas-phase concentrations of DINP and DEHP in the large chamber at 36 °C were about three times lower than those in the small chamber under the same temperature, which is consistent with its lower area/volume ratio. In the second phase, when a large air mixing fan inside the chamber was replaced with a small fan, the gas-phase concentrations of DINP and DEHP in the large chamber were reduced slightly, due to the decease of mass transfer coefficient and emission rate. During the last phase, when the temperature of the chamber was reduced to 25 °C, phthalate concentrations dropped instantly and steeply due to the significantly reduced emissions. However, they did not decrease as quickly thereafter because of desorption of phthalates from the internal surfaces of the large chamber. A fundamental mechanistic model was developed to interpret the experimental results in the large chamber based on the emission characteristics obtained in the small chamber measurements. Reasonable agreement was obtained between the model calculation and experimental data. Further model simulations show that temperature and air mixing above the source material have important effects on the fate of phthalates, while the impact of air change rate (ACH) is not significant.

Design and performance evaluation of thermoelectric generator stove and comparison with traditional, natural and forced draft stoves

The recent work examines the performance of thermoelectric generator (TEG) stove. A TEG is a semiconductor device which converts heat energy directly to electrical energy when a temperature difference is maintained in both the sides of the TEG. The novelty of recent developed design is that a TEG is embedded on the outer wall of the combustion chamber of the forced draft stove. When a temperature difference of 200°C is maintained a power of 9 W is generated from TEG and the generated power is utilised to drive a small dc fan. The excess generated electrical energy can be utilised for lighting and charging a mobile phone. The fan's air cools the cold side of the TEG and the same air is directed inside of combustion chamber. The air improves combustion efficiency and reduces harmful emissions. The performance of the TEG stove is tested by measuring the thermal efficiency, carbon monoxide and particulate matter and then compared with different existing stoves.

Penultimate predecessors of the 2004 Indian Ocean tsunami in Aceh, Sumatra: Stratigraphic, archeological, and historical evidence

AbstractWe present stratigraphic, archeological and historical evidence for two closely timed predecessors of the giant 2004 tsunami on the northern coast of Aceh, northern Sumatra. This is the first direct evidence that a tsunami played a role in a fifteenth century cultural hiatus along the northern Sumatran portion of the maritime silk route. One seacliff exposure on the eastern side of the Lambaro headlands reveals two beds of tsunamigenic coral rubble within a small alluvial fan. Radiocarbon and Uranium‐Thorium disequilibrium dates indicate emplacement of the coral rubble after 1344 ± 3 C.E. Another seacliff exposure, on the western side of the peninsula, contains evidence of nearly continuous settlement from ~1240 C.E. to soon after 1366 ± 3 C.E., terminated by tsunami destruction. At both sites, the tsunamis are likely coincident with sudden uplift of coral reefs above the Sunda megathrust 1394 ± 2 C.E., evidence for which has been published previously. The tsunami (or tsunami pair) appears to have destroyed a vibrant port community and led to the temporary recentering of marine trade dominance to more protected locations farther east. The reestablishment of vibrant communities along the devastated coast by about 1500 CE set the stage for the 2004 disaster.