Fan-angle

Figure 5 First- and second-order cone angles (a) and fan angles (b). When the ligand is irregular in shape, the fan angles...

Fan angle, 1019 Ferribalamins, 883 Ferrichromes, 970 calcium complexes, 972 Ferridoxins, 773 Ferrioxamines, 970,971 Ferritin, 772 structure, 975 Ferroverdin, 797 structure, 272 Five-membered rings metal complexes, 76 substituents metal complexes, 82 Fluorine... 

Figure 7 (a) First- and second-order cone angles and (b) fan angles. Irregularly shaped ligands have various fan angles in different planes... 

Nozzle Designation Orifice Diameter Fan Angle Flowrate ( 60 bar)... 

Air-cooled heat exchangers include a tube bundle, which generally has spiral-wound fins upon the tubes, and a fan, which moves air across the tubes and is provided with a driver. Electric motors are the most commonly usea drivers typical drive arrangements require a V belt or a direc t right-angle gear. A plenum and structural supports are basic components. Louvers are often used ... 

The axial-flow fan is inherently a device for moving a consistent volume of air when blade setting and speed of rotation are constant. Variation in the amount of air flow can be obtained by adjusting the blade angle of the fan and the speed of rotation. The blade angle can be either (1) permanently fixed, (2) hand-adjustable, or (3) automatically adjusted. Air delivery and power are a direct function of blade pitch angle. 

Right-angle gear drive is preferred for fans over 3 m (10 ft) in diameter, for electric motors over 22.4 kW (30 hp), and with steam-turbine drives. 

Fan Ring and Plenum Chambers The air must be distributed from the circular fan to the rec tangular face of the tube bundle. The air velocity at the fan is between 3.8 and 10.2 m/s (750 and 2000 ft/in). The plenum-chamber depth (from fan to tube bundle) is dependent upon the fan dispersion angle (Fig. 11-46), which should have a maximum value of 45°. 

The controllable pitch fan provides an infinitely variable air delivery across the K-Fin Sections through automatic changes in the fan blade angle. Temperature can be closely controlled to meet the varying demands of operating conditions and fluctuating atmospheric temperatures with appreciable power savings under low load conditions. For certain control applications, the ability of... 

Large towers often have the motor mounted horizontally connected to a right angle gear drive. The motor can be closely coupled- in the air stream- or connected with a drive shaft with the motor outside the air stream. Maintenance personnel typically prefer the external TEFC motor- when available- for its easier access. Cooling tower fans- like all fans- operate in accordance with the fan laws one of which states that the horsepower required to drive a fan increases to the cube of fan speed. 

Gear boxes are used on just about all large field erected cooling towers and many factory assembled towers- all of the propeller ty e fan, draw-through type. Almost all are right angle gear drives with the input shaft horizontal and the output... 

They are normally fitted with 10-12 blades, the blade tips inclined away from the angle of rotation. They have the advantage of being very efficient, with fan static efficiencies in excess of 80% for airfoil blades. This type of fan has a nonoverloading characteristic curve. 

In this section, the rotational velocity is directly proportional to the rotational velocity n according to the equation u — irDn. The impeller blade angles remain the same regardless of the rotational velocity of the impeller. Hence, the inlet and exit velocity triangles have the same form. The axial velocity of an axial fan changes directly proportionally to the circumference velocity u. This is also valid for the radial velocity at the outer circumference of a radial impeller fan. These velocities are directly proportional to the fan flow volume hence. 

The regulation of axial fan blade angle also influences the inlet and exit velocity triangles in such a way that the axial velocity and thus the volume flow change. When the relative velocity remains parallel to the blade, the efficiency remains high (Fig. 9.52). 

Adjustable pitch fan A fan in which the pitch angle can be set to provide the required airflow rate. The pitch angle may be preset or controlled with the fan running. 

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