Fan Flow Rate Research Articles

Axial Fan Blade Vibration Assessment under Inlet Cross-Flow Conditions Using Laser Scanning Vibrometry

In thermal power plants equipped with air-cooled condensers (ACCs), axial cooling fans operate under the influence of ambient flow fields. Under inlet cross-flow conditions, the resultant asymmetric flow field is known to introduce additional harmonic forces to the fan blades. This effect has previously only been studied numerically or by using blade-mounted strain gauges. For this study, laser scanning vibrometry (LSV) was used to assess fan blade vibration under inlet cross-flow conditions in an adapted fan test rig inside a wind tunnel test section. Two co-rotating laser beams scanned a low-pressure axial fan, resulting in spectral, phase-resolved surface vibration patterns of the fan blades. Two distinct operating points with flow coefficients of 0.17 and 0.28 were examined, with and without inlet cross-flow influence. While almost identical fan vibration patterns were found for both reference operating points, the overall blade vibration increased by 100% at the low fan flow rate as a result of cross-flow, and by 20% at the high fan flow rate. While numerically predicted natural frequency modes could be confirmed from experimental data as minor peaks in the vibration amplitude spectrum, they were not excited significantly by cross-flow. Instead, primarily higher rotation-rate harmonics were amplified; that is, a synchronous blade-tip flapping was strongly excited at the blade-pass frequency.

Energy-efficient predictive control of indoor thermal comfort and air quality in a direct expansion air conditioning system

Generally, conventional controllers for comfort are designed by using on/off control or proportional-integral (PI) control, with little consideration of energy consumption of the system. This paper presents a multi-input-multi-output (MIMO) model predictive control (MPC) for a direct expansion (DX) air conditioning (A/C) system to improve both indoor thermal comfort and air quality, whereas the energy consumption is minimised. The DX A/C system is modelled into a nonlinear system, with a varying speed of compressor and varying speed of supply fan and volume flow rate of supply air being regarded as inputs. We first propose an open loop controller based on an optimisation of energy consumption with the advantage of a unique set of steady states. The MPC controller is proposed to optimise the transient processes reaching the steady state. To facilitate the MPC design, the nonlinear model is linearised around its steady state. MPC is designed for the linearised model. The advantages of the proposed energy-optimised open loop controller and the closed-loop regulation of the MIMO MPC scheme are verified by simulation results.

Effect of sprayer settings on spray drift during pesticide application in poplar plantations (Populus spp.)

This study assessed spray drift generated by sprayer settings commonly used for pesticide application in poplar plantations (Populus spp.). Tests were conducted per the ISO 22866 methodology using a mounted air-assisted sprayer (Tifone VRP600) equipped with a swivel-cannon air conveyor (model Cannone 50S). Trials evaluated sprayer settings, combinations of nozzle types, airflow rates, and air direction in both adult and young poplar plantations.Overall, spray drift amounts registered downwind of poplar plantations were less than those obtained to derive reference drift curves during the EU Plant Protection Product registration process that used late-growth-stage fruit crops. In the adult poplar plantation, Venturi nozzles (TVI 8004 red) yielded the highest drift reductions compared to reference sprayer setting, especially at distances farthest from the sprayed area (86% between 40 and 47m). Highest total drift reductions were achieved when conventional nozzles (1.81mm ceramic disc-core) were combined with their spray direction modified for an inclined cannon spray unit. Alternatively, the young poplar plantation showed no drift reduction for distances farthest from the sprayed area, regardless of sprayer settings, which likely resulted from lower foliage density and widely-spaced rows. Yet, both Venturi nozzles combined with high fan flow rates and conventional nozzles combined with reduced fan flow rate showed total spray drift reductions of over 70% within the downwind sampling area.These experimental results represent the first set of data on spray drift amounts in poplar plantations, which is key for defining the reference curves and best practices to reduce spray drift in tall tree plantations.

Temperature Distribution of Three-Dimensional Photovoltaic Panel by Using Finite Element Simulation

The low electricity performance of a photovoltaic (PV) panel has been concerned in the PV application system. The effect of environmental and operating condition was affected the performance of the PV panel. In this research work, the main objective is to perform a three-dimensional geometry model of monocrystalline silicon PV panel with and without cooling system by using finite element method. In the case of a cooling system, the effect of the Direct Current (DC) fan flow rate on the temperature distribution of PV panel was investigated. The electrical behaviour of this PV panel is obtained based on the average temperature of the PV panel obtained and average solar irradiance from site location. According to the experimental results, PV panel with cooling system can be significant to provide better performance than the PV panel without cooling system in the same environmental condition. For the effect of flow rate of DC fan in the PV panel with cooling system, the performance of this PV panel has been improved as increasing in flow rate of DC fan.

Exhaust ventilation in attached garages improves residential indoor air quality.

Previous research has shown that indoor benzene levels in homes with attached garages are higher than homes without attached garages. Exhaust ventilation in attached garages is one possible intervention to reduce these concentrations. To evaluate the effectiveness of this intervention, a randomized crossover study was conducted in 33 Ottawa homes inwinter 2014. VOCs including benzene, toluene, ethylbenzene, and xylenes, nitrogen dioxide, carbon monoxide, and air exchange rates were measured over four 48-hour periods when a garage exhaust fan was turned on or off. A blower door test conducted in each garage was used to determine the required exhaust fan flow rate to provide a depressurization of 5Pa in each garage relative to the home. When corrected for ambient concentrations, the fan decreased geometric mean indoor benzene concentrations from1.04 to0.40μg/m3 , or by 62% (P<.05). The garage exhaust fan also significantly reduced outdoor-corrected geometric mean indoor concentrations of other pollutants, including toluene (53%), ethylbenzene (47%), m,p-xylene (45%), o-xylene (43%), and carbon monoxide (23%) (P<.05) while having no impact on the home air exchange rate. This study provides evidence that mechanical exhaust ventilation in attached garages can reduce indoor concentrations of pollutants originating from within attached garages.

Optimization of Blockerless Engine Thrust Reverser

The aim of this investigation was to perform a parametric computational study of the blockerless engine thrust reverser system concept. Early experimental investigations had revealed that injection flow rates of the order of 3% of the fan flow were needed to divert the entire fan flow out through the cascade opening. For a high bypass ratio engine, this amount was too much to be bled from the compressor. This study performs a more detailed evaluation of the concept and covers cases that could not be tested during the experimental investigation due to the limitations of experimental facility. A numerical model simulating the experimental setup was constructed, and effects of various design parameters such as injection location, injection angle, injection thickness, cascade opening, and operational parameters such as fan flow and injection flow rates were studied using trajectory-based analysis. The results suggest that the injection location and injection angle have a profound effect on the performance, and injection flow rates of less than 1.5% could easily divert the entire fan flow through the cascade opening by optimizing parameters of interest.

Effects of shaft supporting structure on performance test of axial flow fan

CFD numerical simulation combined with theoretical analysis are used to research and discuss the obstructing effect, caused by the supporting structure of torsion meter and connecting shaft, on the outlet airflow of axial-flow fan in type-C ducted inlet device. The relations between axial flow fan's total pressure efficiency and flow rate are studied when the distance between supporting structure and outlet section is different, which may provide a reference for the proper design of the performance test device.

Optimizing performance of ceiling-mounted personalized ventilation system assisted by chair fans: Assessment of thermal comfort and indoor air quality

This study investigates and optimizes the performance of ceiling-mounted personalized ventilation system when assisted with chair-mounted fans. Detailed computational fluid dynamics simulations were performed to study the velocity, temperature, and CO2 fields around the microclimate of the occupant. The computational fluid dynamics model was integrated with a bio-heat model to determine the corresponding segmental skin temperature and local and overall comfort and sensation. The computational fluid dynamics model was validated experimentally using a thermal manikin in a climatic chamber. The segmental skin temperature, velocity field, and CO2 field were validated experimentally. The predicted values and the measured values showed good agreement. The validated computational fluid dynamics model was used to optimize the height of the chair fan and the fan flow rate for the best combination of indoor air quality and thermal comfort. The chair fan's configuration to achieve the best thermal comfort and the best indoor air quality occurred at different fan heights. The optimal fan height and flow rate for best thermal comfort were 40 cm (15.75 in.) above floor level and 10 L/s (0.35 ft3/s), respectively. However, the optimal fan height and flow rate for best air quality were found to be 50 cm (19.69 in.) above the floor level and 10 L/s (0.35 ft3/s), respectively. At this configuration, the chair-mounted fans were able to reduce the thermal plumes and improve the performance of the personalized ventilation system by nearly doubling thermal comfort and ventilation effectiveness. The use of chair-mounted fans allowed for the achievement of energy savings up to 17% when compared with conventional mixing ventilation system.

A numerical and experimental test-bed for low-speed fans

An extensive experimental and numerical database provides detailed information on some transition and noise mechanisms encountered in the low-Reynolds-number flows of low-speed axial fans for the first time. Two different similarly instrumented mock-ups built from the same industrial controlled-diffusion airfoil have allowed the first consistent comparison of wall pressure and near-field velocity statistics on the same geometry with and without rotation in perfect similitude of Mach and Reynolds numbers. The experimental and numerical results on the stationary airfoil constitute the largest unique aeroacoustic data set for airfoil trailing-edge noise characterization including installation effects. A similar experimental aeroacoustic database has been built on the rotating controlled-diffusion blade in the Michigan State University-Automotive Fan Research and Development (MSU-AFRD) test facility for different fan configurations, rotational speeds and flow rates. This yields a unique test-bed for fan code validation. The comparisons between the stationary and rotating airfoils suggest that the wall pressure statistics are hardly influenced by rotation in the trailing-edge region, and that the differences in the velocity statistics in the near-wake are a more energetic wake with smaller velocity deficits and diffusion, and a far-less uniform inviscid region in the rotating case.

Ceiling personalized ventilation combined with desk fans for reduced direct and indirect cross-contamination and efficient use of office space

Crowded offices with short distances separating workers’ stations increase the probability of respiratory cross-infection via two different paths. One path is the contaminant transmission through air by direct inhalation and the other is through the body contact of contaminated surfaces and walls. Mixed ventilation principles used today reduces the probability of cross contamination by increasing the distance between the stations challenging the efficient use of the space or by supplying more fresh air in the space which is energy inefficient.In this work, new cooling and ventilation configuration is studied by modeling using computational fluid dynamics with consideration of space occupancy density while providing good indoor air quality. The configuration considers a ceiling personalized ventilation system equipped with desk fans. The ability of the computational fluid dynamics model in computing the thermal, velocity and concentration fields was validated by experiments and published data. The main objective of the performed experiments was to ensure that the developed computational fluid dynamics model can capture the effect of the desk fan flow rate on particle behavior.The studied system is found to provide acceptable indoor air quality at shorter distance between the occupants compared to the mixing system at considerable energy savings. By optimizing the design of the proposed personalized ventilation system, the occupancy density in an office is enhanced to 8m2 per occupant compared to 12m2 per occupant for conventional mixing system while maintaining better indoor air quality at significant decrease in the energy consumption.

Thermal plumes above hot sources: characterization and capture efficiency

Many industrial processes use or generate thermal sources. The release of heat is generally accompanied by the dispersion of pollutants in the working area, which can lead to occupational diseases in the long-term. The characterisation of plumes stemming from thermal sources by natural convection is required to define the adequate dimensions for ventilation systems (fume collecting hoods and general displacement ventilation systems), used to clean air at work stations. The aim of this paper is to present the methods and techniques that can be used in ventilation engineering to analyse and manage industrial applications. The results presented concern the thermal and dynamic characterisation of plumes generated by different types of sources (horizontal disks, vertical cylinders, horizontal rectangular surfaces). New results concerning the efficiency of a fume extraction hood placed above a flat, rectangular thermal source was analysed as a function of the height and position of the hood in relation to the source and the extraction fan flow rate. These results are of practical interest. A numerical approach of temperatures in the proximal zone is also proposed.

대기 조건에 따른 공랭식 응축기 성능 저하 개선 연구

Air cooled condenser for power plant is used at inland area of desert or mountainous area because condenser coolant like sea water is not necessary. However, the performance of air cooled condenser is influenced by ambient condition such as wind speed and air temperature. Therefore, various devices have been designed to improve the performance of air cooled condenser. In this study, the CFD analysis for air cooled condenser was carried out according to wind speed and wind screen configuration. As wind speed increased from 3m/s to 7m/s, the fan flow rate was reduced about 15.76% and the rise of inlet air temperature was 5.55 degree of Celsius. When the suitable wind screen is equipped, the fan flow rate went up about 5.18% and inlet air temperature dropped by 2.08 degree of Celsius in comparison with original case without wind screen at 7m/s wind speed.

Optimization on Performance of the Latent Heat Storage Unit (LHSU) in Telecommunications Base Stations (TBSs) in China

Abstract A latent heat storage unit (LHSU) that combined with energy storage modules and an air cooler was investigated to save the space cooling energy consumption in telecommunications base stations in China. A mathematical model was employed to simulate the heat transfer processes within energy storage modules and air cooler. In addition, an experiment was carried out in an enthalpy difference laboratory. The relative errors of air and temperature difference between the simulation and experimental results were calculated for energy charging process and energy discharging process, respectively. It was shown that the relative error for the water circulation system was reported to 1.33% and 5.23% under the charging and discharging process and 7.27% and 8.00% for air circulation system. The annual energy saving ratio was presented as a function of PCM melting temperature for varied pump flow rates and fan flow rates. To obtain the maximum annual energy savings ratio, a genetic algorithm was developed, considering fan flow rate, pump flow rate and melting temperature of PCM. Annual energy savings ratios were improved by 6.48%, 4.39%, 3.48%, and 3.51%, in Shenyang, Zhengzhou, Changsha, and Kunming, respectively.

Thermal management for a micro semiconductor laser based on thermoelectric cooling

The performance of semiconductor laser is dependent on its cooling and thermal control system. A micro-thermoelectric cooler (mTEC) used on a semiconductor laser is studied by the finite element analysis method. The heat generated by the laser is 2 W and the heat flux of the laser is 2.5 × 104 W/m2. In order to enhance the heat dissipation of the hot side of TEC and maintain the temperature of optical chips of the laser appropriately ranging in 30–40 °C, different heat dissipation methods are studied. The effects of the heat sink size, the air flow rate of the fan, the radiation of the shell and the ambient temperature on the performance of the laser are analyzed. The results show that the performance of TEC has been improved by increasing the heat sink's size and fan's flow rate, and the radiation of the shell has little effect. An experimental study is also done to verify the simulated results.

Effect of Air Deflectors on Fan Performancein Tunnel-Ventilated Broiler Houseswith a Dropped Ceiling

<abstract> <bold><sc>Abstract. </sc></bold>Air velocity is a critical design parameter for modern commercial broiler houses, owing to the beneficial effects of increased cooling on live performance and thermal comfort in broiler chickens. As a result, design velocities have increased over the last 15 years and broiler growers have installed additional fan capacity or air deflectors in the ceiling peak to reduce building cross-sectional area. While deflectors have traditionally been recommended only for buildings with open ceilings, an increasing number of growers have installed deflectors in dropped ceiling houses to provide local increases in air velocity without additional fan capacity and improve air velocity uniformity across the house. However, adding additional restriction can increase static pressure and reduce fan performance. Fan flow rates were measured in three tunnel-ventilated commercial broiler houses equipped with air deflectors with the deflectors in the deployed (down) and retracted (up) positions. The broiler houses measured 15.2 × 144.8 m and were equipped with 12 tunnel exhaust fans (137.2 cm diameter) and nine air deflectors at 12.2 m intervals, beginning after the tunnel inlet area and ending 15.2 m before the fans. Flow rate and static pressure data were collected concurrently for each fan for each deflector position with all fans operating to simulate tunnel ventilation during warm weather. Data were analyzed using ANOVA and least square means were separated using Fisher’s LSD. The results show that deploying air deflectors significantly reduced mean fan flow rate by 11% (p < 0.0001) and increased static pressure by 11.2 Pa (p < 0.0001). The results of the current study suggest that adding air deflectors is likely not appropriate in existing broiler houses with dropped ceilings when fan performance and energy use are taken into consideration.

Heat load capability matching principle and its applications to anti-freezing of air-cooled condenser

Air-cooled condenser in power plants takes a risk of freezing in extremely cold days, so it is of benefit to the safe and economical operation of direct dry cooling system to propose the anti-freezing principles and take measures. On the basis of the heat load balance between the exhaust steam and cooling air, the heat load capacity matching principle for the anti-freezing of air-cooled condenser is proposed with reference to the freezing point of water. By applying heat exchanger model to the finned tube bundles of air-cooled condenser, the thermo-aerodynamic behavior of cooling air, the condensation of exhaust steam and the sensible heat rejection of condensate in a representative air-cooled condenser cell are synchronously modeled and resolved. The correlations among the ambient temperature, flow rate of cooling air, exhaust steam flow rate and quality, and back pressure of turbine that prevent the air-cooled condenser from freezing are discussed, and the anti-freezing flow rate of exhaust steam, back pressure of turbine and flow rate of axial flow fan are obtained. The results show that the anti-freezing flow rate of exhaust steam and back pressure both increase with decreasing the ambient temperature and increasing the flow rate of axial flow fan, from which derive the secure steam flow rate that can reduce the back pressure as much as possible to improve thermal efficiency. The anti-freezing fan flow rate increases with increasing the exhaust steam flow rate and ambient temperature, but varies little with back pressure. The increased steam quality will result in a higher heat load at the steam side, which allows a higher rotational speed of fan to be free of freezing for air-cooled condenser. The application of heat load capacity matching principle to the anti-freezing of air-cooled condenser contributes to the secure and optimal operation of dry cooling system in power plants.

Optimisation of night-time ventilation parameters to reduce building's energy consumption by integrating DOE2 and MATLAB

We have developed an algorithm to optimise the fan flow rate by integrating DOE2 (building's energy simulation software) with MATLAB's genetic algorithm. In our developed algorithm, MATLAB can send desired values of optimisation variables for different hours to DOE2 to simulate building's energy use, and it can also receive building's energy consumption and other data from DOE2 for the optimisation. This powerful optimisation tool can be used for finding optimal solution of night-time ventilation fan flow rates and maximising energy savings. Results of optimisation are used to train a neural network to predict fan flow rates for different conditions. Night-time ventilation investigated in DOE2 considers parameters such as (1) night-time ventilation duration, (2) ventilation fan flow rate, (3) outdoor temperature, and (4) temperature difference between outdoor and indoor. Optimisation results show outdoor temperature between 10°C and 18°C and the temperature difference of more than 8°C are appropriate for night-time ventilation.

F241 小型シロッコファンの圧力変動の周波数特性(OS9 熱・流動(7))

Although the sirocco fan has the characteristics of high pressure and high quantity flow, there is a problem with the noise which easily becomes loud. The purpose of this study is to clarify the relationship between noise and internal flow of fan flow rate in the three conditions, using numerical analysis. In addition, a sirocco fan with small number of blades was used for this study. As results of the frequency analysis, for scroll tongues, at the maximum flow rate (Q = 0.0320 m^3/s), the pressure varies remarkably, and a high pressure variation value in the blade passing frequency (880Hz) was confirmed. In addition, this phenomenon could not be confirmed at a flow rate of less than maximum efficiency point (Q = 0.0178 m^3/s). For blades, at any rate, to have high pressure fluctuation value at 40Hz was confirmed. These caused rotational noise. But, in the high frequency range (800〜1000Hz), a high pressure variation value could not be confirmed.

Performance prediction of an air-cooled steam condenser using UDF method

The performance of air-cooled steam condensers (ACSCs) is always influenced under the unfavorable effect of wind conditions. It is significant to understand the mechanism of such influences so as to improve and optimize the performance of the condensers. In this study, the flow field around a 2 × 600 MW direct air-cooled power plant at different wind speeds and ambient temperatures is numerically simulated, and the relevant influence mechanism is illustrated. User defined function (UDF) based on steam properties, which plays a critical role in the prediction of condenser back pressures, is proposed to simulate the condensation of the turbine exhaust in the exchangers. It is found that wind speed has great influences on the performance of air-cooled steam condensers due to the variation of pressure distribution around the ACSC platform. Heat transfer rate degrades rapidly, while the fan flow rate rises slightly, with the increase of ambient temperature because the heat transfer potential between ambient air and the turbine exhaust is determined by their temperature difference. Finally, the stable back pressures corresponding to each prescribed wind condition are forecasted according to the comparison between the computational heat transfer rate and the ideal heat rejection.

The Microenvironment Simulation and Ergonomic Evaluation of Negative Pressure Isolation Cabin

The paper simulates the airflow in the microenvironment of negative pressure isolation cabin for the infectious disease patients. The result shows that the proper setting of such parameters as air inlet, air outlet, fan flow rate, and differential pressure control can effectively discharge the contaminated air out of the tank after the air is efficiently filtered. During the cabin ergonomic evaluation experiment based on different negative pressure values, the temperature and humidity rise slightly compared with the external environment but there is no obvious accumulation. Besides, the human life indication is consistently kept in the normal range.