Air conditioning fan heat


Axial flow fans, ia which the air flow is parallel to the fan axis, are the workhorse fans ia many petrochemical and utiUty iadustry appHcations. These are the first choice of air mover whenever large volumes of air at low (most commonly up to 500 Pa (2.0 ia. H2O)) pressures are needed. Axial flow fans range ia size from 25 mm diameter (cooling computers) up to 12.3 m ia diameter (cooling condenser water ia power plant cooling towers). These fans are used ia air-cooled heat exchangers for process cooling ia many chemical plants ia sizes of 1.8—4.3 m (see HeaT-EXCHANGETECHNOLOGy). Axial fans from 0.6 to 9 m diameter are used ia heating, ventilation, and air conditioning (HVAC) appHcations ia homes and office buildings around the world. Most commonly, axial flow fans are used ia short ducts called fan rings or cylinders, dischargiag iato the atmosphere. Most large fans ia cooling towers have velocity recovery stacks that capture the wasted velocity pressure energy and convert it back iato useful work.  [c.110]

For heating purposes, most air conditioning systems use fossil-fueled furnaces to heat air, or boilers to heat water or produce steam. Forced air systems use a blower fan and ductwork to distribute conditioned air to points of use. Air quality is enhanced in forced-air systems through the use of filters. The filters are normally placed in the return air, just before the heating and cooling components. Provision may be made for fresh outdoor air to be added to recirculated room air. A hydronic heating system uses hot water to convey heat from a boiler to radiators, convectors, or wall and floor panel coils. Most steam heating systems use boiler-produced steam to heat buildings via radiators, convectors, or heating coils placed in ductwork. Heating systems may employ humidifiers in winter to counter the drying effect of heated air, particularly in forced-air systems.  [c.23]

The volume of a fan should be determined by (1) the process material balance plus reasonable extra (about 20%) plus volume for control at possible future requirements (2) generous capacity for purging and (3) process area ventilation composed of fume hoods, heat dissipation, and normal comfort ventilation. Table 12-19 gives suggested air changes for area ventilation, but not air conditioning. Excellent details for evaluation and the design of ventilating, air conditioning, and heating can be found in Reference 31.  [c.569]

This necessitates plant capable of control of temperature by being able to add or subtract heat from the air and control of humidity by being able to add or subtract moisture. The system also comprises fan(s), filtration, and a distribution system and may include noise control. Other terms such as cooling or comfort cooling may be met and these can be taken to mean an ability to lower the temperature of the air by refrigeration but without full control of humidity. Moisture may be removed as an incidental characteristic of the cooling coil. The term air conditioning is sometimes used where control of humidity is not included. It is essential to employ clear specifications of performance.  [c.436]

The energy input of part of the plant must be included in the cooling load. In all cases include fan heat, either net motor power or gross motor input, depending on whether the motors are in the conditioned space or not. Also, in the case of packaged units within the space, heat is given off from the compressors and may not be allowed for in the manufacturer s rating.  [c.271]

Figure 2 illustrates one of the several available test methods (2) and a typical performance curve. Fans designed for a duct as illustrated have a section of straight discharge duct attached. Straightening vanes are provided to eliminate swid, reduce turbulence, and aid flow equalization across the duct. Air flow is determined usiag a pitot traverse while the fan is operated at a constant speed. The measured pressures are corrected for duct losses back to fan outlet conditions. A fan performs ia accordance with the performance curve only if there is an equivalent duct present to convert velocity head efficiently to static head. At the end of the test, the duct is blanked to measure discharge pressure and shaft power at a shutoff (no flow) condition. The opposite extreme of the curve, free deflvery (equivalent to duct removal), is extrapolated from nearly wide-open conditions. Intermediate poiats at sufficiently close iatervals to define the curve would be measured by replacing the blank at the end of the duct with restricting orifices of varyiag cross section.  [c.104]

Beatings used on fans may be either sleeve or antifriction type and must be designed to withstand loads resulting from dead weight, unbalance, and rotor thmst and be able to operate at the iatended maximum speed without excessive heating (see Bearing materials). When natural convection from the beatings is iaadequate, some other cooling method must be provided. Lubricating oil may be circulated through an external cooler, or the pillow blocks may be cored with passages for forced circulation of air or water. Fans operated at high temperatures iacrease the beating cooling problem caused by heat conduction along the shaft. A small external fan wheel on the shaft, called a heat slinger, is frequently provided, or forced-circulation water cooling is used. In addition to the beatings of fans operating on hot, low density gas at high pressure rise, special attention is needed to ensure high rigidity of the wheel and shaft. Fan wheels should be balanced both statically and dynamically, eg, ia the field with chalk and weights (15). Elaborate electronic test instmments are also available. An unbalanced condition causes a vibrational displacement of the beatings which is frequently checked. Table 2 fists typical displacements of fans operating at various speeds and various degrees of unbalance.  [c.109]

Alcohols and Alkoxylates. Alkyl and alkoxyalkyl sulfates can be produced from the corresponding alcohols or nonionics by reaction with a wide variety of reagents including chlorosulfuric acid, sulfur trioxide, sulfuric acid, and sulfamic acid [5329-14-6] (223—233). The products are similar in wetting time, detergency, and foam generation. Chlorosulfuric acid gives slightly better colors but requires disposal of HCl. Sulfation using SO requires controlled reaction temperatures and fast reaction times for best results. The preferred method of sulfation uses some form of continuous thin-fHm reactor. The reaction time is generally 0.1—0.5 seconds and the heat generated in the film is rapidly removed by the cooled reaction surface. In the United States, alkyl and alkoxyalkyl sulfates are mainly produced by the thin-fHm method. An important undesirable side reaction of ethoxylated alcohol sulfation is dioxane formation which can range from traces to hundreds or even thousands of ppm (mg/kg) depending on raw material quaHty and sulfation/neutralization conditions (20,234—236). Dioxane forms by the chemical cleavage of two molecules of ethylene oxide from the parent ethoxylated  [c.83]

The distillation of SiHCl is a relatively straightforward and low cost purification method. On the other hand, the reprecipitation of elemental siUcon by CVD is expensive and compHcated because of the need to maintain the utmost purity at highly elevated temperatures. Long narrow rods of polycrystalline siUcon are heated by an electric current to 1100 C providing the thermodynamic conditions for siUcon precipitation. Because the yield in equation 1 is only - 10%, there is considerable recycling of chlorosilane reagents. In this respect, the semiconductor siUcon factory is typical of most chemical plants. The growth of the polycrystalline siUcon rod is diffusion rate limited, - 1 fim/min, taking as long as two weeks to grow out to a 10-cm diameter. Therefore the process is very slow, very capital intensive, and because heat is continually radiated away at 1100°C during the long growth period, very energy intensive as well. Heat radiation reflectors are employed to reduce energy cost, as well as clusters of rods which intercept one another s thermal radiation. Owing to the electrical energy cost component, semiconductor siUcon plants are frequentiy located in regions having low cost hydroelectric power, such as the Pacific Northwest of the United States. To further reduce the energy cost, silane [7803-62-3], SiH, gas decomposition is being used in at least one large plant to produce semiconductor siUcon in large volumes. The advantage of using silane is that decomposition takes place at a diminished temperature, - 800 C.  [c.117]

When the mean annual temperature is 16.7°C (30°F) lower than the design dry-bulb temperature and when both fans in a bay have automatically controllable pitch of fan blades, annual power required has been found to be 22, 36, and 54 percent respectively of that needed at the design condition for three process services [Frank L. Rubin, Tower Requirements Are Lower for Air-Cooled Heat Exchangers with AV Fans, Oil Gas J., 165-167 (Oct. 11, 1982)]. Alternatively, when fans have two-speed motors, these dehver one-half of the design flow of air at half speed and use only one-eighth of the power of the full-speed condition.  [c.1082]

The rating of a transformer-rectifier unit refers to an external temperature of 35°C. Higher temperatures require the special design of some components and this should be discussed with the manufacturer. Usually T-Rs are outfitted with self-cooling by natural ventilation. Forced ventilation with a fan leads to considerable contamination and is not used for this reason. In particularly difficult climatic conditions (e.g., for steel-water constructions in the tropics), oil cooling is necessary for larger units. This provides good protection for the rectifier cells and transformers, removes heat, and provides protection against atmospheric effects for variable ratio transformers with current collectors.  [c.229]

Fig. 29-16. Afterburner with heat recovery. A, Fume inlet to insulated forced draft fan 310 m /min at 230°C). B, Regenerative shell-and-tube heat exchanger (55% effective recovery). C, Automatic bypass around heat exchanger for temperature control (required for excess hydrocarbons in fume steam under certain process conditions). D, Fume inlet and burner chamber internally insulated (fume steam raised to 425°C by heat exchanger). E, Combustion chamber, refractory lined for 815°C duty (operating at 760 C for required fume oxidation to meet local regulations). F, Discharge stream leaving regenerative heat exchanger at 520 C enters ventilating air heal exchanger for further waste heat recovery. G, Ventilating air fan and filter (310 m /min of outside air). H, Automatic bypass with dampers for control of ventilating air temperature. I, Heated air for winter comfort heating requirements leaves at controlled temperature. J, Discharge stack (470°Q. K, Combustion safeguard system with dual burner manifold and controls for high turndown, L, Remote control panel with electronic temperature controls. Source Hirt Combustion Engineers. Fig. 29-16. Afterburner with heat recovery. A, Fume inlet to insulated forced draft fan 310 m /min at 230°C). B, Regenerative shell-and-tube heat exchanger (55% effective recovery). C, Automatic bypass around heat exchanger for temperature control (required for excess hydrocarbons in fume steam under certain process conditions). D, Fume inlet and burner chamber internally insulated (fume steam raised to 425°C by heat exchanger). E, Combustion chamber, refractory lined for 815°C duty (operating at 760 C for required fume oxidation to meet local regulations). F, Discharge stream leaving regenerative heat exchanger at 520 C enters ventilating air heal exchanger for further waste heat recovery. G, Ventilating air fan and filter (310 m /min of outside air). H, Automatic bypass with dampers for control of ventilating air temperature. I, Heated air for winter comfort heating requirements leaves at controlled temperature. J, Discharge stack (470°Q. K, Combustion safeguard system with dual burner manifold and controls for high turndown, L, Remote control panel with electronic temperature controls. Source Hirt Combustion Engineers.
During the normal Mode of Operation of the system the process air enters the RTO System Fan and passes through the Inlet Diverter Valve where the process air is forced into the bottom of the left ceramic heat transfer bed. As the process air rises through the ceramic heat transfer bed, the temperature of the process stream will rise. The tops of the beds are controlled to a temperature of 1,500 F. The bottoms of the beds will vary depending upon the temperature of the air that is coming in. If it is assumed that the process air is at ambient conditions or 70 F, then as the air enters the bottom of the bed, the bottom of the bed will approach the inlet air temperature of 70 F. The entering air is heated and the media is cooled. As the air exits the ceramic media it will approach 1500 F. The process air then enters the second bed at 1,500 F and now the ceramic media recovers the heat from the air, and increases in temperature. At a fixed time interval (usually 4 to 5 minutes), or based on thermocouple control, the diverter valves switch and the process air is directed to enter the bed on the right and exits the bed on the left. Prior to valve switching the air heated the right bed and now this bed is being cooled. The cooling starts at the bottom and continues upward because the media is hot and the energy is transferred. The process air then goes through the purification chamber and exits through the second bed. When the valves are switched, whatever organics had not been destroyed prior to the flow being reversed are then exhausted out of the stack. In addition, the rapidity of switching or closure of the valves is critical to minimize the bypass of unoxidized organics. If the emissions versus time were plotted, the graph would reflect a very low exhaust concentration level, but whenever the diverter valve switches an organic pulse occurs in the exhaust stream. Since the valves shift every four minutes these pulses reduce the overall destruction efficiency of the organics. Several methods of processing the pulse exist in order to achieve higher destruction efficiencies.  [c.484]

Baghouses may operate under negative or positive pressures. Negative pressure baghouses operate upstream of the fan and must be designed to withstand the maximum head developed by the fan. This could correspond to the case in which all the inlet dampers are closed and the fan is operating under cold conditions. Although the pressure drop across the filter unit may only be 50-200 mm WG, the compartment walls may have to be designed to 1000 mm WG. The compartment must be designed to minimize in-leakage air so that the fan does not have to be oversized. If the dust-air mixture can become explosive, the unit must be designed to resist a positive pressure that is determined from dust-explosion tests. Venting requirements for the baghouse to limit pressure buildup can be determined from a publication by Schofield.The allowable positive pressure for baghouse design must be specified.  [c.1233]

A cyclone system is to be installed as a part of a bagging operation. The unit is shown in Figure 4-48. Determine the head required for purchase of the fan. The conditions are  [c.263]

For a specific service of desuperheating Freon 11 (180°F) and condensing at 115°F, ambient air at 70°F, total Q = 31.6 X 10 Btu/hr, Smith points out that for three comparative designs with a threefold reduction in fan horsepower, a 35% increase occurs in first cost, a 30% increase in surface, and a 75% increase in plan area. In general this trend will apply to all comparisons on design parameters of course it is influenced to a greater or lesser degree by specific conditions, which reflect the sensitivity of changes in flow quantities on heat transfer coefficients.  [c.268]

The process is indicated on the chart in Figure 24.9, taking point B as the tube temperature. Since this would be the ultimate dew point temperature of the air for an infinitely sized coil, the point B is termed the apparatus dew point (ADP). In practice, the cooling element will be made of tubes, probably with extended outer surface in the form of fins (see Figure 7.3). Heat transfer from the air to the coolant will vary with the fin height from the tube wall, the materials, and any changes in the coolant temperature which may not be constant. The average coolant temperature will be at some lower point D, and the temperature difference B — D will be a function of the conductivity of the coil. As air at condition A enters the coil, a thin layer will come into contact with the fin surface and will be cooled to B. It will then mix with the remainder of the air between the fins, so that the line AB is a mix line.  [c.249]

All of the heat extracted from the air, both sensible and latent, passes to the refrigerant and is given up at the condenser to re-heat, together with the energy supplied to the compressor and the fan motor (since the latter is in the airstream). Figures for this electrical energy will have to be determined and assessed in terms of kilojoules per kilogram of air passing through the apparatus. A typical cycle is shown in Figure 24.13 and indicates a final condition of about 47°C dry bulb and 10% saturation.  [c.254]

Research and testing results have shown that mica can be used successfully ia air-conditioner fan blades, dashboard panels, head lamp assembhes, fan shrouds, and door panels. Mica can also be substituted for more expensive glass dakes to strengthen lightweight plastic seat backs, load doors, gtill panels, ignition system parts, and air-conditioning and heater valve housings. Both American and Japanese automakers are incorporating ground mica ia place of asbestos (qv) ia acoustic compounds that change vibrations and eliminate road and engine noise. Mica is also an environmentally accepted replacement for asbestos ia brake linings (see Brake linings and clutch facings).  [c.293]

During winter additional heating is needed in the occupied zone due to the heat losses. The selection of the heating method depends on the selected air conditioning strategy for the heating season. In order to save heating energy costs the exhaust air temperature should not exceed the temperature in rhe occupied zone. Thus, the desired strategy would be the mixing strategy. An appropriate heating method for that purpose would be, for example, an air and recirculation method with fan heaters located close ro the ceiling see Fig. 8.l6fc>.  [c.638]

A typical IFVAC system uses a combination of heating, cooling, humidification (adding moisture) and dehumidification (removing moisture) processes to thermally cniiditinii air. This conditioned air, which is a mixture of outdoor air and recirculated indoor air, is known as supply air. The supply airstream typically passes through filters, heat exchangers that add or remove heat from the supply airstream, a supply fan, air ducts, dampers that are used to regulate the rate of aiidlow, and finally diffusers located either in the ceiling or floor to the occupied space. The return air is drawn from the occupied spaces and flows back to the mechanical rooms either through return air ducts or through the plenum between suspended ceiling and the floor of the next-higher stoiy. A portion of the return air is exliausted to the outdoors, and the remainder is mixed with the fresh outdoor air and resupplied to the space after filtering and thermal conditioning. In general, the supply air contains more recirculated air than fresh outdoor air to keep the energy cost of air conditioning down.  [c.54]

Heat Pumps and Air-Conditioning, Electricity Council, London, 1982 ATKOOL and KOSWING, W. S. Atkins Partners, Epsom, Surrey DALY, B. B., Woods Practical Guide to Fan Engineering, Woods of Colchester Ltd, 1979  [c.371]

When selecting the motor, power requirements, effect of temperature changes on load, and motor starting current and torque have to be considered. Calculation of system air-flow resistance is subject to some error and cannot always be predicted precisely. Therefore, the fan power predicted by the intersection of the fan and system curves may not be precise. If the system resistance is higher, it may be necessary to speed up the fan, which makes it draw more power. If the resistance is less than anticipated, the flow increases (unless dampered) also resulting in higher power consumption. A general rule is to size the motor for the power requited for a system pressure drop both 25% greater and less than that predicted. Air temperature can also affect power requirements. A fan normally operated on a hot gas may have to be started when the system is cold. Under such conditions, the inlet gas density is much higher. The fan develops more head and a greater mass of air is dehvered. Unless the system flow can be throttled back until normal operating temperatures are reached, the motor has to be sized for the cold-starting conditions based on density ratios, often two or three times normal mnning power.  [c.108]

It is never appropriate to add any type of anti-freeze solution to an open cooling tower. Closed (fluid cooler) systems, however, can be protected from freeze-up by the addition of ethylene glycol or other fluids. Fluid cooler casing sections can also be insulated to reduce heat loss thereby protecting the coil from freeze-up. Counterflow, blowthrough towers tend to be more popular as the freeze potential increases. Crossflow towers tend to freeze water on their air inlet louvers under extreme conditions. Fans (propeller type) can be arranged to reverse direction on such towers to melt ice. This process should never be automated. Instead, the operator should weigh the situation and reverse the fan only as long as required. The designer must select components suitable for reverse rotation. Fan discharge dampers are a capacity control accessory item for centrifugal fan cooling towers. They fit in the fan scroll. In the open position, they are much like a thin piece of sheet metal in a moving airstream oriented parallel to airflow. The airstream doesn t know its there. As the dampers close- the sheet metal becomes less parallel to airflow- turbulenee disrupts the air stream. Airfoil dampers essentially ruin fan housing effieiency to achieve a reduction in airflow. Dampers can set and locked when a manual locking quadrant is specified but it is more common to use electric or pneumatic actuators that close the dampers as the exiting water temperature becomes too low. While reducing airflow is the correet method of reducing capacity, dampers are not the best approach. They offer the poorest energy savings and the actuating mechanisms tend to fail long before the average eooling tower life span.  [c.79]

A small fraction of homes use the same appliance to provide both space heating and water heating. This has been done for over a centuiy with tankless coils in cast-iron boilers. Water heating can be provided by modern boilers supplying heat to an indirect water heater that uses the water from the hydronic system to heat water for domestic uses in a storage tank. Since the early 1980s a technology has been developed that uses hot water from the water heater to heat a forced air system via fan coils. Ground-source heat pumps that provide space conditioning while extracting or storing heat from the gi onnd arc often also equipped with the capability to provide water heating.  [c.1217]

Cooling air to the cabinets is normally introduced from the room at low-level front or back with fan-assisted discharge to the rear or top. The normal practice is to introduce room-cooling air at high level. This mixes with rising hot air to give a near-uniform condition in the occupied levels. The distribution of cooling air must be carefully matched to heat load around the room. A large room (say, over 300m ) should have separate zones of control with their own sensors. The ceiling void should nevertheless be common. The recirculation of air will confine itself to the zones fed by individual units when all are running but will be redistributed by a ventilated ceiling in the event of partial failure of plant modules.  [c.444]


See pages that mention the term Air conditioning fan heat : [c.20]    [c.576]    [c.73]    [c.430]    [c.1106]    [c.66]    [c.997]    [c.697]    [c.453]   
Plant Engineer's Handbook (2001) -- [ c.488 ]