Cross-flow Fan Research Articles

ENHANCING THE EFFICIENCY OF INDOOR LOCAL VENTILATION USING CROSS-FLOW FANS: CASE STUDY FOR A SMOKING CABIN

The paper presents an original solution for increasing air quality and reducing energy consumption of the local indoor ventilation by using cross-flow fans. The solution is a combination between the local exhaust ventilation (LEV) technique from industry, negative-pressure isolation rooms used in hospitals, and air curtains (AC) used for isolating of indoor/outdoor spaces. The solution provides a high air flow rate at low velocity due to the high value of the flow coefficient of the cross flow fans and, in the same time, allows modular setup according to local space geometry. A case study is proposed regarding the isolation of a smoking area where smell and airborne particles appear. A 3D numerical simulation was performed, in which one cross-flow fan with long axial length was considered. The optimum air flow rate and flow pattern was obtained in order to isolate the local space. The results show that a new approach for reducing sick building syndrome could be addressed by providing modular and local ventilation using cross-flow fans.

Approximate Life Cycle Assessment via Case-Based Reasoning for Eco-Design

Life cycle assessment (LCA) is a fundamental tool used in eco-design. However, it can be costly and resource intensive. We take steps toward the automation of the inventory and impact analyses stages of LCA via the proposal and development of a case-based reasoning (CBR) procedure to estimate the ecological effects of a product. The case memory in CBR, which contains representations and ecological effects of known products, is organized using an extension of the function-behavior-structure (FBS) representation for products. The extension includes ecological characteristics and values. We develop similarity metrics to measure the distance between cases in the case memory and the new product. The $k$ -medoids algorithm is used to cluster the case memory, our metrics enable cluster retrieval and case selection, and multiple linear regression analysis is employed for adaptation. Using a database of 100 fans, we test the accuracy of the proposed approach on a cross flow fan not in the database. The method gives ecological effect estimates within 3% of the true values when there are similar fans in the retrieved cluster and about 7% when the retrieved cluster does not contain similar fans.

G0501002 多翼前向き羽を持つ羽根車流れに発生する流体振動

The experimental and numerical studies were performed to clarify the fundamental flow characteristics of a fan with forward-inclined multi-blades. A Sirocco fan and crossflow fan are rotated in the open space, i.e. without casing. The crossflow fan simulates a Sirocco fan with a closed inlet. Using fan's height is 115mm, the inlet and outlet radii are 160 and 180 mm, respectively. The inlet and outlet blade angles are 90 and 150 degrees, respectively. The impller includes 52 blades. The rotational frequency is set to 24 Hz. The radial velocity fluctuations at the impeller outlet are measured using a hot-wire anemometry. The experimental and numerical results show good agreements with respect to frequencies and cell numbers. The FFT spectra of the experimental and numerical results show two peaks in the Sirocco fan and one peak in the crossflow fan. The two- and three-cell oscillations occur for the Sirocco fan, and the one-cell for the crossflow fan.

クロスフローファンの偏心渦が内部流れと性能に及ぼす影響

クロスフローファンの偏心渦が内部流れと性能に及ぼす影響

Experimental and numerical investigations on the eccentric vortex of the cross flow fan

The effects of an eccentric vortex on the performance of a cross flow fan for air-conditioning is evaluated experimentally and numerically. Based on the two-dimensional computational analysis using commercial CFD software, and experimental measurements, a new design is proposed for the inlet guide vanes. The new design reduces vortex shedding from the fan blades, thereby reducing the size of the eccentric vortex, which results in improved fan efficiency. The new design improves the performance of the cross flow fan marginally by 4.6% at a maximum volumetric flow rate of 10.5 m3 min−1.

The Development of a Cross-Flow Fan for Electronic Devices Cooling with a Focus on Laptop Computers

The directive is to develop a new type of cross-flow fan for cooling electronic devices. First, the module is based on the 60X60X6mm fan and attempts to use several parameters to enhance the fan’s performance. The parameters considered here include blade number, angle of the blade, impeller diameter, divergent structure, and outlet area. Both numerical and experimental analyses are carried out on the cross-flow fan which was oriented horizontally. The ANSYS Fluent software is used in a 2D simulation to predict the heat transfer coefficient and the flow fields. Next, the flow and acoustic noise measurements are carried out at different parameters with the aid of AMCA and semi-anechoic chambers. The results show that when the outlet vent size is 70% of fan outside diameter the outcome is an enhanced fan performance of 12%. The optimal number of blades is 37. A block is inserted below the fan blade to improve the fan performance by 8%. The numerical and experimental values of air flow were plotted and found to be consistent. In summary, this study provides a systematic process to develop a cross-flow fan that can meet the requirements for thin and light laptop computers.

1012 様々なアスペクト比を持つクロス・フロー・ファン内の非定常圧力計測

The authors experimentally try to appear the characteristics of the flow inside a cross-flow fan. By the running-average technique, the authors reveal the features in pressure wave form. By comparing the distributions for the singular aspect ratio L/D_2 = 0.6 with those for L/D_2 = 0.3 and 1.0, the authors reveal that the radial position of an eccentric-vortex center becomes inward with decreasing L/D_2. The authors confirm the minimum-pressure coefficient C_<pmin> which is a reduced minimum pressure defind by p_<min>/0.5pu_2^2 is independent of Re not only qualitatively but also quantitatively. The authors get such a conclusion as the eccentric-vortex strength is independent of Re, in addition to the conclusion that the eccentric-vortex centre moves to the impeller centre with decreasing L/D_2. Strictly speaking, C_<pmin> tends to decrease with decreasing Re for L/D_2 = 0.3 and 0.6. This tendency is converse for L/D_2 = 1.0.

리어가이더 곡률반경에 따른 룸에어콘용 관류홴의 공력성능에 대한 실험적 연구

The aerodynamic performance of a cross-flow fan is strongly influenced by the various design factors of a rear-guider and a stabilizer. The design factors considered in this paper are a rear-guider clearance, a stabilizer clearance, and a stabilizer setup angle, respectively. Also, these factors are given to the various diameter ratio between a basic circle and a impeller. The static pressure and the flowrate of a cross-flow fan were measured with a fan-tester. It could be found that the useful design factors with a good aerodynamic performance exist in the certain assembly conditions of an indoor RAC. Therefore, it could be known that a new published patent determining the easy design of an indoor RAC can be applied in a variety of goods.

리어가이더 선단각도에 따른 룸에어콘용 관류홴의 공력성능에 관한 실험적 연구

리어가이더 선단각도에 따른 룸에어콘용 관류홴의 공력성능에 관한 실험적 연구

A New Configuration of Vertical Axis Wind Turbine for a Distributed and Efficient Wind Power Generation System

Preliminary results obtained for a new configuration lift based vertical-axis wind turbine are shown. The turbine rotor is a cross flow fan type made with high curvature aerodynamic profiles. A reduced scale model of the turbine rotor has been designed and preliminary tested at the Department of Aerospace Engineering of the University of Pisa (rotor diameter = 250 mm, rotor height = 210 mm). The reduced scale model shows an efficiency of about 18%. The rotor is of a self-starting type. Two-dimensional CFD analyses have been performed applying both the Moving Reference Frame and the Moving Mesh conditions to the grid which surrounds the rotor blades (Fluent® Rel. 6.3 and STAR-CCM+® Rel. 6.04 have been used). Noticeable scale effects have been found numerically, so, the efficiency of a full scale lift based vertical axis multi-blades optimized wind turbine is expected to be comparable with lift based horizontal-axis wind turbines.

Modular ventilation with twin air curtains for reducing dispersed pollution

The optimal solution for reducing the level of pollutants remains their trapping close to source. When this possibility is absent, the high degree of pollutant dispersion makes difficult and expensive any process of pollutant trapping and cleaning. This work suggests a new approach regarding the ventilation of urban road tunnels, based on the necessity for such spaces to take advantage of ventilation means which permanently direct the air towards cleaning filters while constraining uncontrolled pollutants dispersion. A concept of a modular ventilation is proposed, in which the air flow is not only induced by intake and/or exhaust fans and random obstacles inside the boundaries, but also confined by means of air curtains generated by cross flow fans. The expected result is a higher efficiency of the ventilation and of the subsequent air cleaning process. To illustrate the concept, a case study was undertaken. The investigations were focused on the behavior of twin air curtains generated by two cross flow fans and forming virtual walls inside an urban road tunnel. The results presented indicate how the distance between the curtains should be chosen, so that they remain stable, how the curtains interact with moving vehicles, and how the vents placed on the tunnel ceiling for exhausting polluted gases should be designed.

환기 성능 향상을 위한 횡류팬을 이용한 덕트 형상의 최적화

Recently, the duct system with a cross flow fan was used to improve the ventilation in various industrial fields. For the efficient ventilation, it is necessary to design the duct system based on the flow characteristics around the cross flow fan. In the present study, the flow characteristics around a cross flow fan in the ventilation duct were predicted by using the moving mesh and sliding interface techniques for the rotation of blades. To design the duct system with the high performance of ventilation, the CFD simulations were repeated with the revised duct model based on the DOE. With the numerical results of flow rate through the ventilation duct with various geometric parameters, the optimized geometry of ventilation duct to maximize the flow rate was obtained by using the Kriging approximation method. From the performance curves of cross flow fan in the original and optimized models of ventilation duct, it was observed that the flow rate through the optimized model is about 16 percent larger than that through the original model.

J052013 クロスフローファンの干渉騒音の音源解析(〔J052-01〕流体関連の騒音と振動(1))

It is cleared in relating to interaction noise from cross flow fan with experiments and numerical simulation that the tongue shape affects the characteristic of sound source. Interaction noise becomes remarkable large at the operating point. There are three parts of sound sources on the tongue of the interaction noise. The first one is located at the end edge, the second one is located at the middle of the tongue and the third one in the round corner when the flow from impeller reaches to the tongue. The large interaction noise isn't generated at the round corner of the tongue where the very large pressure fluctuation is emerged. But the middle part of the tongue is the main source of interaction noise. It is proposed that the tongue shape is shortened at middle part of the tongue and the interaction noise is reduced with it.

J055024 小型クロスフローファンの内部流動状態および性能特性に関する研究(〔J055-02〕流体機械の研究開発におけるEFD/CFD(2))

J055024 小型クロスフローファンの内部流動状態および性能特性に関する研究(〔J055-02〕流体機械の研究開発におけるEFD/CFD(2))

에어컨 실내기의 공력소음 예측을 위한 RANS 난류모델의 성능 평가

shear stress transport (SST) and Spalart-Allmaras (S-A) turbulence models were analyzed and compared with the noise data from the experiments. The frequency spectra of the far-field acoustic pressure were computed using the Farrasat equation derived from the Ffowcs Williams-Hawkings (FW-H) equation based on the acoustic analogy model. Two fixed fan casings and the rotating cross-flow fan were used as the source surfaces of the dipole noise in the Farrasat equation. The result with the standard k-

상용차 캐빈 내의 열전모듈에 의한 열유동 수치해석

The steady three-dimensional numerical analysis on the thermal flow using standard k-<TEX>${\varepsilon}$</TEX> turbulence model was carried out to investigate the air cooling effect of a cooler on the cabin for a commercial vehicle. Here, the heat exchanging method of this cabin cooler uses the cooling effect of a thermoelectric module. In consequence, the air system resistance of a cooler within the cabin is about 12.1 Pa as a static pressure, and then the operating point of a virtual cross-flow fan considering in this study is formed in the comparatively low flowrate region. The discharging air temperature of a cooler is about <TEX>$14{\sim}15^{\circ}C$</TEX>. Moreover, the air cooling temperature difference obtained under the outdoor cabin temperature of <TEX>$40^{\circ}C$</TEX> shows about <TEX>$7{\sim}9^{\circ}C$</TEX> in a driver resting space and about <TEX>$9{\sim}14^{\circ}C$</TEX> in the front of a driver's seat including the space of a driver's foot.

Experimental and numerical study of an airfoil in combination with a cross flow fan

In this article, the airfoil comprising a cross flow fan has been studied at various boundary conditions by experiment and numerical solution. The airfoil generates high lift at low forward speeds and shows excellent potential for short take off and landing and vertical take off and landing. According to the experiments, lift and pitching moment coefficients of the airfoil increase and its drag coefficient reduces with the fan rotational velocity. The pitching moment coefficient enhancement demonstrates that the aircraft is more stable at higher rotational speeds. Experiments showed that the aerodynamic coefficients decrease with the free stream Reynolds number. Flow field over the airfoil has been studied by the computational fluid dynamics technique and compared with the experimental data. Numerical solution was in good agreement with the experiments. Solution showed that skin friction coefficient on the airfoil bottom wall is not sensitive to the rotational velocity, but on the upper surface, especially inside the casing, it is deeply influenced by the fan speed, while it increases with the Reynolds number on the both surfaces. According to the numerical solution, the static pressure difference between the airfoil surfaces increases with rotational velocity demonstrating higher lift coefficients at higher fan speeds, and also increases with the Reynolds number that is equivalent to the enhancement of the aerodynamic forces as shown by the experiments. Because of a sharp edge a sudden jump was observed in the pressure distribution on the airfoil upper wall. By replacing this sharp edge with a smooth and round one this pressure jump reduced significantly and pressure distribution on the modified surface became smoother and its extremal value diminished considerably. The streamlines on the upper surface were closer than those on the bottom surface indicating higher pressure on the airfoil bottom wall. They became closer on the airfoil upper surface when fan speed increased. In addition, velocity gradient on the airfoil surfaces increased with the Reynolds number that is tantamount to a higher skin friction coefficient. Discrepancies between numerical and experimental data can be attributed to measurement uncertainty in the experiments and convergence precision in the numerical solution, two-dimensional solution in the computational fluid dynamics and three dimensionality of the flow at the wing tips in reality.

Investigation of flow and heat transfer for a split air conditioner indoor unit

Split air conditioners (SACs) include complicated components, such as the fin and tube heat exchanger (FTHE) and cross-flow fan (CFF), and their complex interaction needs to be investigated in detail. In this study, a three-dimensional representative thin-section model was introduced for modelling SAC indoor units, and heat transfer and fluid flow analysis was made to determine the characteristics of the device. In addition, the numerical method was examined by comparing the results with the heat transfer capacity experiments and Stereo Particle Image Velocimetry (SPIV) measurements at the outlet section of the device were conducted to compare the velocity distribution. The results showed that the difference between the numerical and experimental studies were within acceptable limits; therefore, the thin-section model for the numerical study is a good assumption for determining the heat transfer and flow characteristics of the SACs.

Experimental and numerical investigation of the flap application in an airfoil in combination with a cross flow fan

PurposeThe purpose of this paper is to study flap application in the airfoil comprising a cross flow fan by experiment and numerical simulation.Design/methodology/approachAn airfoil was made and tested in a blowing wind tunnel. Because of complicated shape of the airfoil, distributed quantities in the flow field cannot be measured. They were computed by establishing a CFD code validated by the experimental data. The k‐ε model was used for the Reynolds stress modeling. Flow was considered incompressible, two dimensional and steady‐state. The pressure‐velocity coupling was performed by the SIMPLEC algorithm and convection terms were discretized by using the second‐order upwind discretization scheme.FindingsComputed aerodynamic coefficients were in good agreement with the experimental results. Flap augmented lift and pitching moment coefficients of the airfoil considerably. It was perceived that the airfoil aerodynamic coefficients decrease with the Reynolds number, its lift and pitching moment coefficients increase and its drag coefficient decreases with the fan speed. Static pressure difference between the airfoil surfaces increased with the flap angle and consequently at higher flap angles it must have larger aerodynamic coefficients as proved by the experiments. This pressure difference increases with the Reynolds number that is equivalent to higher aerodynamic forces. It was shown by the numerical solution that surface pressure on the airfoil upper wall decreases with the fan speed while it is not sensitive to the fan speed on the airfoil bottom wall.Originality/valueThis is the first instance in which flap application in the airfoil with forced airflow provided by an integrated cross flow fan is studied.

Experimental visualization of the flow characteristics of the outflow of a split air conditioner indoor unit by meshed infrared thermography and stereo particle image velocimetry

Three-dimensional (3D) flow structures due to the interaction between the device edges, fan casing and cross flow fan (CFF) in the rectangular jet at the outflow of a split air conditioner (SAC) indoor unit were investigated by the stereo particle image velocimetry (SPIV) method. In addition, a novel application of infrared thermography called meshed infrared thermography (MIT), used to determine and visualize the temperature profile in an air flow field, was introduced for the first time and used to investigate the temperature distribution at the outflow section of the SAC indoor unit. The results of measurements that were made at different positions on the device were used to prepare three-dimensional reconstructions of the rectangular jet flow and temperature distribution at the outlet section.