Suction Fan Research Articles

DRYING CHARACTERISTICS OF OKRA BY DIFFERENT SOLAR DRYERS

Drying of agricultural products is the great importance for preservation of food by human beings. Solar drying refers to a technique that utilizes incident solar radiation to convert it into thermal heat energy for drying purposes. The drying operation is mainly affected by variation of the air drying temperature, air flow rate and air relative humidity. The research was carried out to study the drying characteristics of okra to achieve highly drying rates and good quality. Three similar drying units were designed and manufactured in the Faculty of Agricultural., Menoufiya University and installed on the roof of Agricultural Engineering building. Each unit consists of solar collector, drying chamber, drying trays, chimney, and suction fan. Drying characteristics of okra treated by 1.0%sodium carbonates at boiling point for three minuets under different drying systems and flow rates of air 0.075 m3/sec, 0.149 m3/sec, and 0.249 m3/sec at the same time. Computer program used to define the fit mathematical model described the dying curves of okra in different conditions. The obtained results showed that, indirect dryer for drying okra at air flow rate of 0.075 m3/sec achieved the best quality. The drying efficiency was decreased as, the moisture content of okra crop reduced.

G0500-3-2 擬似ランダム信号入力による一様乱流の生成([G0500-3]流体工学部門一般講演(3))

The purpose of the present study is to make the Reynolds number of homogeneous turbulence as high as possible using a multi-fan wind tunnel. The wind tunnel has great potentialities to provide fluctuations and various velocity profiles due to the independence of an array of small fans. We applied a number of driving modes with different conditions, such as fractal arrangement of driving fan, random input signal, and suction fans. The measurements revealed characteristics of the turbulence those modes generated.

Seasonal and diel patterns of biting midges (Ceratopogonidae) and mosquitoes (Culicidae) on the Parris Island Marine Corps Recruit Depot

The Marine Corps Recruit Depot on Parris Island, SC, is surrounded by tidal salt marshes, which are breeding habitats for many pestiferous biting flies. Knowledge of biting fly behavior patterns is needed to develop effective pest management strategies in urban areas adjacent to salt marshes. We measured biting midge (Ceratopogonidae) and mosquito (Culicidae) seasonal abundance and diel activity patterns on Parris Island using CO(2)-baited suction traps from November 2001 - November 2004. Of the three biting midge species collected, Culicoides furens was most abundant (86.2% of total) and was present in high numbers from late March to November. Culicoides hollensis (12.0% of total) was present during spring and fall but absent in summer and winter; and Culicoides melleus (1.7% of total) was present in spring through fall but absent in winter. Abundance of C. furens had a positive linear correlation with air temperature and rainfall. There were nonlinear correlations between air temperature and C. hollensis and C. melleus numbers, which were most abundant at moderate temperatures. Of 18 mosquito species collected, the most abundant were Aedes taeniorhynchus (42.7% of total), Aedes sollicitans (26.3% of total), Culex salinarius (15.6% of total), Culex quinquefasciatus (7.3% of total), and Aedes vexans (5.7% of total); other species comprised <5% of collections. Aedes taeniorhynchus numbers were positively correlated with temperature and rainfall, and Cx. salinarius was correlated with soil moisture. Activity of most biting midges and mosquitoes were highest the first two hours following sunset. Species of biting flies were present in all months, suggesting that year-round control measures are necessary to reduce exposure to potential disease vectors and nuisance biting.

A Comparison of Two Generic Trap Types for Monitoring Mosquitoes Through an Annual Cycle in Tropical Australia

We compare the community composition, abundance, and seasonality of mosquito species detected by the encephalitis virus surveillance (EVS) CO2 traps and Centers for Disease Control and Prevention (CDC) light traps. Traps were run concurrently for a year during routine weekly monitoring in the vicinity of the city of Darwin in northern Australia. The EVS CO2 traps detected far more individuals than CDC light traps notwithstanding a weaker suction fan, but species richness was similar. Regardless of variation in community composition among sites, differences between trap types were remarkably consistent. Seasonal trends in the abundance of 5 key species from each trap type were similar, but markedly more so in strongly seasonal species. Although EVS CO2 traps outperformed CDC light traps for routine monitoring, the historical transition from the latter to the former is unlikely to have major consequences for the identification of community composition or detection of seasonal trends in key species.

Development of a Photovoltaic Powered Forced Convection Solar Dryer

This solar conversion system incorporates a suction fan powered by a solar PV module. Located at the outlet of the chamber is the d.c suction fan utilised to achieve forced air circulation without the use of external power supply like grid electricity, fossil fuel and battery. Simple thermal energy balance equations and heat transfer equations were employed in the design of the system. The operational efficiency of the collector is 83.2% and mass flow rate 1.58kg/min, the maximum temperature achieved in the chamber was 58oC. The system was used to dry vegetable, hydrophylum. The capital cost is less than $150.

Deux années de comparaison de pièges à &lt;em&gt;Culicoides&lt;/em&gt; dans les îles Baléares

Several types of light traps are being used in different European countries to help determine the potential vector species of blue­tongue virus (BTV). The four traps compared in this study were: i) the Onderstepoort trap – black light trap, with 8 W ultraviolet light tube used in the United Kingdom and Italy; ii) mini-CDC – black light, model 912, with 4 W UV light tube, used in Spain and Portugal; iii) Rieb trap, white light model, with 4 W UV light tube, used from 2000 to 2006 in France; iv) UK trap, with 4 W standard white incandescent bulb, used in the past in the UK and other European countries for African horse sickness surveillance. All traps included a downdraught suction fan. Tests were conducted from 18 Oct. to 19 Nov. 2007, from 18 Feb. to 4 June 2008, and from 1 Oct. to 28 Nov. 2008. During at least nine non-consecutive nights the traps were placed following a randomized block design in four different positions on a cattle farm located on the island of Mallorca (Balearic Islands, Spain). In 2008, only three traps (Onderstepoort, UK and mini-CDC) were tested. Results showed major differences in collecting Culicoides. The Onderstepoort trap showed the best performance in terms of total number of Culicoides captured in autumn both in 2007 and 2008. The UK trap, and especially the Rieb trap showed the lowest efficacy in terms of captures. In autumn 2008, the Onderstepoort trap cap­tured on average 90 Culicoides per night, whereas the mini-CDC captured on average 27. During spring 2008, however, the mini- CDC performed better as it captured on average 180 Culicoides per night, against 84 captured by the Onderstepoort. However, Fisher’s least significant difference test showed no statistically sig­nificant differences between the traps (P &lt; 0.05). No remarkable difference was observed between the four traps as they all cap­tured a similar range of species. Captures of Culicoides newsteadi were greater during the autumn, and those of C. obsoletus in the spring. Finally, the Onderstepoort trap showed a higher sensitiv­ity in catching Culicoides midges in low population levels of the vector, especially during the winter season.

G0501-3-1 フラクタル配置されたファン駆動法による一様乱流の生成(実験,後流)

G0501-3-1 フラクタル配置されたファン駆動法による一様乱流の生成(実験,後流)

Crossflow fan에 의한 컴퓨터 케이스 내부의 유동특성에 관한 연구

The purpose of this study is to find out a flow characteristics when a crossflow-fan is installed inside the computer case and to provide information about the preliminary data of cooling efficiency of CPU and a flow inside and outside of a computer case. Under the condition of operating the fan inside the experimental duct we changed the position of a installation of the slot, and the experiment measured with PIV and the results are as follows. Under the influence of the crossflow-fan installed to the air discharging side, mean velocity between 35 to 45 on the point 80 of the Slot 0.2.3 of the case increased and it influences discharging the air inside of the computer case. On the left-upper end. which isn`t directly influenced by the suction-discharging fan installed inside the PC, a flow occurs caused by vortex due to the Sirocco-Fan and Slot installed on the center of the right side. We can see that a flow distribution increases when the Sirocco-Fan operates and a whirl appears stronger between the slot and the suction fan. It is thought that this phenomenon is influenced by a flow while it is on the way of entering from the suction-fan and going out to the discharging-fan.

Study of wind effects on different buildings of pitched roofs

The characteristics of wind flow past simplified models of one-side pitched roof buildings were examined in a wind tunnel that was designed and built at the Housing and Building Research Center (HBRC). The wind tunnel consists of a square cross section of 200 mm × 200 mm (a bellmouth intake, main entrance duct, a flow straightener, a transition section, and a suction fan). The tunnel was calibrated by a pitot-static tube, determining the flow rate and mean velocity upstream of the models. Static pressure distributions on the external surfaces of models were measured with a free stream velocity of 7 m/s. Smoke visualization tests were also carried to obtain qualitatively the flow patterns around a simulated building models. The flow visualization results gave a good qualitative agreement with measurements. The separation zone, the reattachment length, and the wake region width were clear in the visualization-obtained patterns. The temperature distribution at various points over the pitched roof was measured and the heat transfer coefficient was normalized by the heat transfer coefficient for a 0°. pitch roof. A CFD computer package (ANSYS) based on the finite element method was used to predict velocity contours and vectors in the model domain. The model was created in two-dimensions and meshed with about 15,000 quadratic elements. Convergence and stability of the solution were verified at a certain number of finite elements and iterations. It was found that as the angle of inclination of the roof increased, the mean static pressure on such roof has increased with an enlarged stagnation zone. The results show that a pitched roof of 30° has a much better heat transfer performance than one with 10°, 20°, and 40° for same base building model height and Reynolds number. Good agreement was found between the experimental and computational results.

Process engineering design of pathological waste incinerator with an integrated combustion gases treatment unit

Management of medical wastes generated at different hospitals in Egypt is considered a highly serious problem. The sources and quantities of regulated medical wastes have been thoroughly surveyed and estimated (75 t/day from governmental hospitals in Cairo). From the collected data it was concluded that the most appropriate incinerator capacity is 150 kg/h. The objective of this work is to develop the process engineering design of an integrated unit, which is technically and economically capable for incinerating medical wastes and treatment of combustion gases. Such unit consists of (i) an incineration unit (INC-1) having an operating temperature of 1100 °C at 300% excess air, (ii) combustion-gases cooler (HE-1) generating 35 m 3/h hot water at 75 °C, (iii) dust filter (DF-1) capable of reducing particulates to 10–20 mg/Nm 3, (iv) gas scrubbers (GS-1,2) for removing acidic gases, (v) a multi-tube fixed bed catalytic converter (CC-1) to maintain the level of dioxins and furans below 0.1 ng/Nm 3, and (vi) an induced-draft suction fan system (SF-1) that can handle 6500 Nm 3/h at 250 °C. The residence time of combustion gases in the ignition, mixing and combustion chambers was found to be 2 s, 0.25 s and 0.75 s, respectively. This will ensure both thorough homogenization of combustion gases and complete destruction of harmful constituents of the refuse. The adequate engineering design of individual process equipment results in competitive fixed and operating investments. The incineration unit has proved its high operating efficiency through the measurements of different pollutant-levels vented to the open atmosphere, which was found to be in conformity with the maximum allowable limits as specified in the law number 4/1994 issued by the Egyptian Environmental Affairs Agency (EEAA) and the European standards.

局所相似モデルの概念と風洞実験による検証 : 通風時の換気量予測法に関する研究(第1報)

A new model has been proposed for evaluating the discharge coefficient and flow angle at an inflow opening for cross-ventilation based on the previous analysis of the flow structure by the Large Eddy Simulation. This model is based on the idea that the cross-ventilation flow structure in the vicinity of an inflow opening creates dynamic similarity under the condition that the ratio of cross-ventilation driving pressure to dynamic pressure of cross flow at the opening is consistent. Wind tunnel model study was carried out to reproduce cross-ventilation by attaching suction fan at the leeward side of the building model. Discharge coefficients at stagnant surrounding condition with suction flow correspond well with those exposed to external wind with extremely large suction flow. Total pressure at the opening is preserved even when flow is separated at the upstream corner. It was confirmed that the proposed model can be applied to almost any directions and opening positions.

THERMAL TRANSPORT IN A MULTIPLE JET IMPINGEMENT OVEN

ABSTRACT Three‐dimensional numerical simulation of flow field and heat transfer in a jet impingement oven with multiple jets was carried out. Distribution of local heat transfer coefficient on a model cookie in the oven cavity was obtained from the predicted flow and temperature fields, and compared with the experimentally measured values. Effects of air temperature (400, 450K) and air velocity (2.5, 5, 10 m/s), on the surface heat transfer coefficient were studied. Numerical predictions showed good agreement with the experimental results. It was found that heat transfer coefficient was a strong function of air velocity while air temperature had no effect on the heat transfer coefficient. Local heat transfer coefficient values ranged between 11 and 66 W/m2K whereas average heat transfer coefficient values ranged between 24 and 42 W/m2K. Results also showed that because of the presence of the suction fan in the oven, flow field near the model cookie surface was quite different from that for a jet impinging on a flat surface.

Studies on noise pollution in cotton ginneries

Cotton ginning systems contain numerous types of machinery-each of which is a source of noise and contribute to the overall noise level. Noise pollution in cotton ginneries has never received attention in the past in India. Noise levels of different machineries used in cotton· ginning systems were studied. The likely effect of noise on workers' health and the possible ways of reducing the noise levels were suggested. Noise levels for roller gins were found to vary from 87.0 to 97.7 dBA under no load and from 85.9 to 97.7 dBA under load condition. Noise for double roller gins were found above permissible exposure limit of 85 dBA. Gearbox of the double roller gin was found to generate more noise than other moying elements of the gin. Noise levels of pre-cleaners and lint cleaners were found below the permissible limit. In press house noise level was observed in the range of 793 to 93.5 dBA for different models of presses. Gin house was found to be the noisiest workstation with an average noise level of 96.0 dBA. The noise level for the workstations such as raw cotton suction fan, pre-cleaner, gin house central platform, seed blower and press operator room were observed above the permissible exposure limit Exposure to such a noise may adversely affect overall efficiency, safety, and hearing ability of workers. Protecting them from loud noise by employing technical and personal measures of noise control can create· healthful working conditions in ginneries.

Locating fires in abandoned underground coal mines

A Mine Fire Diagnostic (MFD) Methodology was developed to determine the location and extent of combustion zones in abandoned underground coal mines. In this method, a characteristic fire signature is based on the ratio of higher molecular weight hydrocarbon gases (C 2 to C 5) to total hydrocarbon gas. Initially, gas samples are obtained at the bottom of boreholes under baseline or static conditions. A second set of samples is obtained when a suction fan is used to influence the direction of gas movement. Pressure data define the degree of communication between boreholes. The value of the diagnostic ratio under communication conditions is taken as a measure of subsurface fire activity related to a particular flow direction. Using a Venn diagram technique, the results are mapped as quadrants on a borehole map of the site. Repetition of the communication tests provides overlapping quadrants that define hot, cold, and indeterminate areas. The MFD has been used to distinguish hearted and cold subsurface areas at four mine fire sites. At each of the sites, the extent of the fire could not be inferred from surface evidence, and the location of combustion zones had a significant impact on plans to control the fire. Although the method is labor intensive and requires drilling cased boreholes, it is relatively simple and provides information that cannot be obtained by other methods.

SYNTHETIC COVERS FOR EMISSIONS CONTROL FROM EARTHEN EMBANKED SWINE LAGOONS PART II: NEGATIVE PRESSURE LAGOON COVER

One of the significant odor sources on swine farms is manure storage. This study investigated reducing odor and gas emissions from a 29- × 39-m anaerobic swine lagoon by capturing gases beneath a 0.41-mm thick, flexible reinforced polyethylene membrane. The cover was anchored and sealed about its perimeter by burying the edges in a trench around the lagoon embankment. A fan installed alongside the lagoon drew gases continuously from a looped perimeter duct system to provide a (suction) pressure differential of approximately 500 Pa to hold the lagoon cover in place. The measured average emission rates of CO2, H2S, NH3, and CH4 were approximately 270 kg/ha-day, 92, 20, and 940 g/ha-day, respectively. The average flow rate from the suction fan was 0.194 m3/s (411 cfm) and average odor intensity was 598 OU/m3. The derived odor emission rate was 116 OU/s. The total cost of the lagoon cover was $7,800 or $3.75/m2 ($0.36/ft2). Operating cost was approximately $36/month, based on an electrical rate of $0.10 per kWh.

Schallemission von Landmaschinen (am Beispiel des Amazone Airplanters ED 451 K)

Sound emissions from farm machines cause considerable stress on man and environment. Tests were conducted on sound emissions from an air spacing seeder. The sound analysis from a stationary operated implement gave 96 dB at a distance of 3 m. An analysis was made of the noise source, the suction fan. The highest sound intensity was measured at the fan outlet on the right hand side,. Sound emission increases with higher fan rpm´s and the dominant frequency can be traced back to the multiples of PTO rpm´s. Especially the 1.5, 4.5 and 6 rpm-sequences are incited during fan operation. Currently in the research project sponsored by the German Federal Foundation, measures for reducing noise and their transfer to other farm machines are being examined.

A Silent Cooling System with a Double Suction Type Centrifugal Fan with Backward Blades.

We have developed a new cooling system for the engine of construction machinery. This system produces two different air flow routes by a double suction type centrifugal fan with backward blades. We first measured aerodynamic performance and sound level of the double suction type fan, which consists of two single suction type fans of different design, and compared these measurements to those of single suction type fans. Next, we installed the fan in a scale model of the new cooling system. The performance of this double suction type fan was different to that of a single suction type. It is considered that the effect of interaction of the exit flows from the two different fans caused this performance change. The test model installed in an engine compartment showed that this cooling system reduced the area of air inlets and outlets around the engine and did not cause re-circulation of cooling air.

Active Control of Combustion for Optimal Performance

Combustion-zone stoichiometry and fuel-air premixing were actively controlled to optimize the combustor performance over a range of operating conditions. The objective was to maximize the combustion temperature, while maintaining NOx within a specified limit. The combustion system consisted of a premixer located coaxially near the inlet of a water-cooled shroud. The equivalence ratio was controlled by a variable-speed suction fan located downstream. The split between the premixing air and diffusion air was governed by the distance between the premixer and shroud. The combustor performance was characterized by a cost function evaluated from time-averaged measurements of NOx and oxygen concentrations in products. The cost function was minimized by the downhill simplex algorithm employing closed-loop feedback. Experiments were conducted at different fuel flow rates to demonstrate that the controller optimized the performance without prior knowledge of the combustor behavior.

Recommended Control Configurations for DC Drives With Flexible Shafts

This article deals with new recommended control structures for adjustable-speed direct current (DC) drives with a flexible shaft. Two cases will be analyzed: a two-inertia system (i.e., single motor driving a load through an elastic coupling; e.g., suction fan drive) and a three-inertia system (i.e., two motors driving a common load through two elastic couplings; e.g., dual-kiln drives). The first recommended control con figuration is an extension of the rigid system controller with an added control term that is proportional to the differential speed. The second recommended configuration is the variable-structure sliding-mode con trol (VSC) that is known to be robust, insensitive to parameter variations, and easy to implement. Simulation results for both structures are presented to illustrate the effectiveness of the proposed controllers.

Influence of swirl on the discharge coefficients of sonic nozzles

Flow characteristics of a swirl generator are studied using an open circuit flow loop, and influence of upstream swirl on the discharge coefficients of sonic nozzles is investigated using a high pressure gas flow standard measurement system. The open circuit flow loop consists of swirl generator, testsection, sonic nozzle, suction fan and LDV system. The gas flow measurement system comprises two compressors, storage tank, temperature control loop, sonic nozzle testsection, weighing tank, gyroscopic scale and data acquisition system. Experiments are performed at various nozzle throat diameters, inlet pressures and angles of swirl generator. As the angle of swirl generator becomes larger, axial velocities decrease near the wall and rapidly increase in the pipe core, and swirl velocities increase to form swirl flow. Influence of upstream swirl on discharge coefficients becomes greater as the intensity of swirl increases and as the nozzle throat diameter is enlarged. Variation trend with Reynolds number, however, is very similar each other regardless of swirl intensity.