China
Africa
Explore chapters and articles related to this topic
Ventilation Fans
Published in William Popendorf, Industrial Hygiene Control of Airborne Chemical Hazards, 2019
Centrifugal fans differ from axial fans in more ways than they are similar. About the only similarity is that air enters both fans parallel to the impeller’s axis of rotation. As shown within Figures 16.3 and 16.12, air enters a centrifugal fan only near its axial center (none enters near the blades’ tips). In contrast to the propeller shape of axial impellers, most centrifugal impellers like those in Figures 16.13 and 16.17a look more like a wheel (Figure 16.15 would look more like a wheel if it had a back plate as depicted to the left of the graph in Figure 16.16). The impeller of a centrifugal fan directs the air outward (in the radial direction) where the fan housing (the scroll) constrains and redirects the flow tangentially toward the fan outlet. Because the air exits a centrifugal fan tangentially to its impeller, all centrifugal fans effectively create a 90° turn in the ducting (often a disadvantage), as depicted in both Figures 16.3 and 16.11. In contrast to all axial fans as a group, each of the following three main types of centrifugal fans has distinct performance characteristics that give them separate advantages and disadvantages.j
Principles of Energy Conversion
Published in Hamid A. Toliyat, Gerald B. Kliman, Handbook of Electric Motors, 2018
Hamid A. Toliyat, Gerald B. Kliman
Ventilation of an electrical machine is achieved either by air ducts in the rotor, built-in fans, or by a separately driven external fan. The fan might be centrifugal or axial. A centrifugal fan forces air from the center to flow outward, irrespective of the direction of rotation. A propeller-type axial fan can move air axially in either direction depending on the direction of rotation.
Availability Analysis of Equipment Performance Data
Published in W. Li Kam, Applied Thermodynamics: Availability Method And Energy Conversion, 2018
Fans usually perform in a fashion similar to that of the pump. When a fan develops a small pressure change, the air flow is essentially incompressible. Fans used in central power stations either are the axial-flow type or the centrifugal type. The centrifugal fan may have different curved blades, such as forward-curved, backward-curved, and straight radial blades. The different blades will result in different fan performances. Figure 11-2 presents the typical performance of a fan in terms of its capacity. It is seen that the fan design point usually is around the maximum static efficiency. In operation, the fan capacity will determine the fan static pressure head and power input. The following equations are used frequently in practice: () Static air hp = (AFR)(Δp)6350 () ηf=Static air hpShaft hp
Aerodynamic noise prediction of a high-speed centrifugal fan considering impeller-eccentric effect
Published in Engineering Applications of Computational Fluid Mechanics, 2022
Ke-Xin Ren, Zhi-Jun Shuai, Xi Wang, Jie Jian, Tao Yu, Lie-Yi Dong, Wan-You Li, Chen-Xing Jiang
In a centrifugal fan, owing to the impeller-eccentric effect, the end shell is more likely to be hit by the impeller rim and to be bruised and restrained, and the distance between the blade’s trailing edge (TE) and volute tongue varies with time. This could have a significant influence on the unsteady flow field and subsequently the sound generation. Thereby, for effective noise control, the internal flow and sound field characteristics of a high-speed centrifugal fan with eccentric impeller make a valuable subject for research. In this paper, we focus on the aerodynamic noise prediction of a high-speed centrifugal fan considering the impeller-eccentric effect. First, the transient flow field of the high-speed centrifugal fan with an eccentric impeller is calculated. The sound source in the whole flow field is then extracted, and the aerodynamic noise under both normal and eccentric impeller circumstances is investigated and compared with the experimental results by adopting an acoustic FEM. Furthermore, the sound contribution of the sound source in different regions is analyzed through the noise spectrum and the intensity of Lighthill’s tensor.
Mechanical properties changes in oak (Quersus canariensis) and stone pine (Pinus pinea) wood subjected to various convective drying conditions
Published in European Journal of Environmental and Civil Engineering, 2020
Rim Bahar, Sahbi Ouertani, Soufien Azzouz, Houcem Naili, Mohamed Tahar El Ayeb, Afif El Cafci
Convective drying experiments are carried out using a vertical downward dryer type and allowed for close control and regulation of all air-drying parameters. This dryer unit was designed and built at LETTM laboratory of the department of physics of Faculty of Science of Tunis (Figure 1). Air flow was generated using centrifugal fan. Air velocity was adjusted using velocity controller. Air temperature was created using heating resistances inside dryer tunnel. Relative humidity of air flow was controlled using vapor generator with electro-van element outside the dryer. The dryer unit was equipped with a programmable automat to allow controlling and regulating the operating conditions using two moisture and temperature probes placed in the drying room. Digital balance was placed outside the dryer to record the product mass periodically during drying.
Experimental Investigation on Thermal Protection of High Temperature and High Velocity Jet Impinging a Cross-Shaped plate
Published in Heat Transfer Engineering, 2020
Jian Cai, Wei Ye, Shuyang Tu, Shaochen Tian, Xu Zhang
Figure 2 shows a schematic of mockup. The mockup included a full-premixed gas burner, a high pressure centrifugal fan, a combustion mixing chamber with the outer diameter D = 600 mm and an impinging jet nozzle with internal diameter of 150 mm. The nozzle impinges obliquely at an angle α of 30°, between the nozzle center and the normal direction of the impingement surface, as shown in Figure 3. The jet was produced by the designed nozzle and hot gas was supplied by gas burner and centrifugal fan. A pressure measurement device was installed on the gas pipe to monitor the gas dynamic pressure. A thermocouple thermometer was also installed on the gas pipe to ensure that jet exit temperature can be maintained at 500 °C. The parameters of the mockup were summarized as Table 1.