Cooling air fan

Dirt buildup on the motor s cooling-air fan guard screen. 

FIGURE 39.27 Flow diagram of a steam dryer for pulp (A, wet pulp B, heating steam at 6-15 bar C, dried pulp D, generated steam at 2-5 bar E, condensate F, plug feeder, G, fluffer H, discharge screw 1, circulation fans J, cooling-air fan). (Courtesy of MoDo-Chemetics.)... 

An additional means for reducing NOx would be to recycle some of the effluent bed gas into the suction of the cooling air fan. This will reduce the oxygen concentration in the combustion air to 13 to 17%, which along with fuel injection will reduce NOx by 50%. 

Air. This tends to be less cool than all sources of cooling water and, because of low air-side heat transfer coefficients, needs finned tubes. The fins are hard to keep clean in areas where the air is dirty or is liable to contain (seasonally) large numbers of insects. On the other hand in the event of an electric power failure stopping the cooling air fans, natural convection through the banks of warm finned tubes can provide up to a quarter of the full condensing capacity subject to temperature. 

NOTE. If a lower wattage lamp is used, longer irradiation times or shorter distances will be necessary. In either case, solvent evaporation can be significantly reduced by directing a flow of cool air (fan) over the reaction tubes. An alternative procedure is to allow the (sealed) tube to stand in sunlight at room temperature for several days. 

All types of clinker cooler emit a great deal of noise, attaining levels of between 95 and lOOdB(A) at points of maximum loudness in the immediate vicinity (about 1 to 5 m distance). With grate and shaft coolers the cooling air fans are the principal... 

The other cooling air fans should be of correspondingly lower performance in terms of pressure developed, reduced stepwise to 10 mbar, as exemplified in Fig. 19. 

The electric power consumption of the cooling air fans accounts for more than 70% of the overall power demand of the cooler. Hence it is essential to use high-efficiency fans which are properly suited to the actual operating conditions of the cooler. 

It is characterized more particularly by its, in principle, simple form of construction. It has no cooling air fans and no separate drive, being rotated with the kiln. See Fig. 35. 

In the event of critically high shell temperatures of a temporary character, large cooling air fans - permanently installed under the cooler in many installations — can automatically be switched on when needed. On the other hand, any water spraying applied to the outside of the cooling tubes must operate continuously. 

Other energy considerations for cooling towers include the use of two-speed or variable-speed drives on cooling-tower fans, and proper cooling-water chemistry to prevent fouling in users (see Water, industrial water treatment). Air coolers can be a cost-effective alternative to cooling towers at 50—90°C, just below the level where heat recovery is economical. 

Cooling-tower fan horsepower can be reduced substantially as the ambient wet-bulb temperature decreases if two-speed fan motors are used. Theoretically, operating at half speed will reduce air flow by 50 percent while decreasing horsepower to one-eighth of full-speed operation. However, ac tual half-speed operation will require about 17 percent of the horsepower at full speed as a result of the inherent motor losses at lighter loads. 

Tube ventilation In this system cooling tubes which work as heat exchangers are welded between the core packet and the outer frame and are open only to the atmosphere. See to Figures 1.20 (a)-(c). One fan inside the stator, mounted on the rotor shaft, transfers the internal hot air through the tube walls which form the internal closed cooling circuit. A second fan mounted outside at the NDE blows out the internal hot air of the tubes to the atmosphere and replaces it with fresh cool air from the other side. This forms a separate external cooling circuit. 

Fan hood with protective grid for cooling air intake... 

The movement of large volumes of cooling air is accomplished by the rotation of large diameter fan blades rotating at high speeds. As a result, noise due to air mrbulence and high fan tip speed is generated. 

Cooling tower fan motors must be properly selected for long life and trouble free operation. In addition, it is important to match the motor s enclosure to the application. Motors in draw through applications that are mounted directly in the air stream, for example, experience tough duty and must be of the totally enclosed type. Motors are categorized as follows ... 

In addition, the small motor fan attempts to blow air down over the motor and is no match for the much bigger cooling tower fan drawing air up and around the motor. The small fan in this case is useless- even counterproductive. This application needs a TEAO motor. Cooling tower manufacturers sometimes purchase special motors tailored for their application... special grease, seals, slingers, weep hole locations, epoxy coatings, etc.. Such features make an OEM replacement more desirable than an off the shelf replacement. 

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. 

Air terminal unit assembly The air terminal unit, consisting of casing, mixing section, flow control, heating, cooling, filters, fans, sound attenuators, etc. 

Amine-stripper overhead condensers are typically air-cooled, fin-fan exchangers. Their duty can be determined from the concepts in Chapter 3 as required to cool the overhead gases and condense the overhead steam... 

The amine cooler is typically an air-cooled, fin-fan cooler, which low-er.s the lean amine temperature before it enters the absorber. The lean amine entering the absorber should be approximately 10°F warmer than the sour gas entering the absorber. Lower amine temperatures may cause the gas to cool in the absorber and thus condense hydrocarbon liquids. Higher temperatures would increase the amine vapor pressure and thus increase amine losses to the gas. The duty for the cooler can be calculated from the lean-amine flow rate, the lean-amine temperature leaving the rich/lean exchanger and the sour-gas inlet temperature. 

This tower depends upon natural draft action the same as a chimney to draw cool air in at the bottom and expel it out the top as warm moist air (Figure 9-101). The action of the tower depends upon the atmospheric temperature therefore, on a hot day the action of the tower may be less than on a cool day. These towers are relatively large, and require power for pumping the water to a point in the tower which is usually lower than for an atmospheric tower. There are no fan costs. Units have been built 310 ft high, base diameter 210 ft and a throat of 120 ft, wdening to 134 ft in diameter at the top [30]. 

These operate by setting the cooling air in motion over a surface of water. Either natural convection or a fan can do... 

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