Air cooler exchangers

Pressure vessels (including heat exchangers and air coolers) in a... 

Rolling mill drive motor heat exchanger (air cooler) Horizontal (tubes)... 

Specimen Location Tube from a heat exchanger—instrument air cooler... 

Anodic protection today allows safe and efficient protection of air coolers and banks of tubes in sulfuric acid plants. In 1966 the air cooler in a sulfuric acid plant in Germany was anodically protected. Since then more than 10,000 m of cooling surfaces in air- and water-cooled sulfuric acid plants worldwide have been protected. The dc output supply of the potentiostats amounts to >25 kW, corresponding to an energy requirement of 2.5 W per m of protected surface. As an example. Fig. 21-9 shows two parallel-connected sulfuric acid smooth tube exchangers in a production plant in Spain. 

For air-cooled heat exchangers, recirculation is more difficult to define or relate to standard practices. Banks of air-coolers are installed in a variety of configurations so, for a particular proposed installation, a study by specialists may be required. This study of recirculation would probably be done later in the projeet even though the results impact costs. There is a practical limit to the number of front-end studies and this is one that can be deferred until geometry is better defined. 

The price of air-cooled exchangers should be obtained from vendors if possible. If not, then by coirelating in-house historical data on a basis of /ft of bare surface vs. total bare surface. Correction factors for materials of construction. pressure, numbers of tube rows, and tube length must be used. Literature data on air coolers is available (Reference 15). but it should be the last resort. In any event, at least one air-cooled heat exchanger in each project should be priced by a vendor to calibrate the historical data to reflect the supply and demand situation at the expected time of procurement. 

Dual-circuit heat exchanger Combined air heater and air cooler battery, with independent pipework or ductwork circuits for the heating and cooling media. 

The cold recovery device consists of an exhaust air humidifier with an integrated heat exchanger and the supply air heat exchanger, which are connected by a fluid circuit. The first can be described as an indirect evaporative cooler. The cold recovery device is able to transport 83% of the maximum possible enthalpy difference from the exhaust air to the supply air. 

The most direct way to reject heat above ambient temperature to the environment is by the use of aircooled heat exchangers, as discussed in Chapter 151. These coolers exploit a flow of ambient air across the outside of tubes through which process fluids are flowing that require cooling. Such air coolers are very common in some industries, particularly when the plant is located in a region where water is scarce. 

Their major disadvantages are that they require more space, they have a higher initial capital cost, and the coolest temperature that can be attained is 20 to 30°F (10 to 15°C) above the ambient air temperature.1 7 For the same amount of heat transfer, an installed carbon-steel shell-and-tube exchanger will cost about one-third as much as an air cooler. This difference diminishes as more expensive materials are used.18 A modification of the air cooler, called the wet-surface air cooler, overcomes some of the above-mentioned disadvantages. It can reduce the temperature that can be attained to nearly the ambient temperature, and there are some claims... 

Wet-surface air coolers should not be used where the surface temperature of the exchanger exceeds 150°F (65°C), because scaling will occur.19 The pretreatment of the water is similar to that used in the open-loop cooling systems discussed previously.19 The amount of blowdown necessary depends on the water properties and... 

It was noticed that the order of process items in the layout spacing recommendations is almost identical. The furnaces and fired heaters are on the top of the list (see Table 18). The next group is formed by compressors and high hazard reactors. Air coolers, ordinary reactors and high hazard pumps appear next. After that come towers, process drums, heat exchangers and pumps. The last and safest group is formed of equipment handling nonflammable and nontoxic materials. 

Pressure vessels (including heat exchangers and air coolers) in a plant handling flammable fluids are subject to potential exposure to external fire. A vessel or group of vessels which could be exposed to a... 

Technically, the process is being exploited in discontinuously operating units of stainless steel (similar to type 316) which are constructed in two ways. In one method, an esterification vessel is combined with a Raschig column, a heat exchanger to preheat the alcohol recycled for esterification by the vapors emerging from the column, and an air cooler. In a second type of esterification unit partial condensation of the water from the vapors is carried out. Contrary to the former process, neither an esterification column, nor a heat exchanger, nor an equipment for a subsequent separation of the reaction water, nor a reflux pump is needed. 

Loss of airflow through a finned tube air cooler bundle is a universal problem. The effect is to reduce the exchanger s cooling efficiency. To restore cooling, you might wish to try the Norm Lieberman method, which consists of reversing the polarity of the fan motor electric leads. The fan will now spin backward. Depending on the nature of the deposits, a portion of the accumulated dirt will be blown off the tubes— but all over the unit. Personnel observe this procedure from a safe distance. 

Figure 8.4. Example of tubular heat exchangers (see also Fig. 8.14). (a) Double-pipe exchanger, (b) Scraped inner surface of a double-pipe exchanger, (c) Shell-and-tube exchanger with fixed tube sheets, (d) Kettle-type reboiler, (e) Horizontal shell side thermosiphon reboiler, (f) Vertical tube side thermosiphon reboiler, (g) Internal reboiler in a tower, (h) Air cooler with induced draft fan above the tube bank, (i) Air cooler with forced draft fan below the tube bank.

The choice of appropriate equipment often is influenced by considerations of price. A lower efficiency or a shorter life may be compensated for by a lower price. Funds may be low at the time of purchase and expected to be more abundant later, or the economic life of the process is expected to be limited. Alternate kinds of equipment for the same service may need to be considered water-cooled exchangers vs. air coolers, concrete cooling towers vs. redwood, filters vs. centrifuges, pneumatic conveyors vs. screw or bucket elevators, and so on. 

Fig. 3. Rough layout sketch (/) the two fined heaters F-l and F-2 are located together but are separated from the other equipment with a subpipeway connecting the process area to the heater area (2) the reboiler E-2 is located adjacent to its column, T-l. The preheat exchanger E-4 is located adjacent to tower T-3 (3) the elevated overhead condenser E-3 is located next to the overhead accumulator V-l. Also, the air condenser FF-3 is located adjacent to its overhead accumulator V-2 (4) the rest of the air coolers (FF-1—3, -5) are grouped together in a common fan structure (3) all equipment and related piping is routed to and from the existing piperack saving the addition of a new piperack (6) all pumps (P-1—P-6) are located in a row under the piperack, and each...

Air-cooled exchangers are classified as forced-draft when the tube section is located on the discharge side of the fan (see Fig. 5.4). Air coolers are classed as induced-draft when the tube section is located on the suction side of the fan. 

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