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Examples finned tubes

Tray, Truck, and Tunnel Driers In order to accelerate drying, the closet is factory-built with tight walls. It forms a box, and the air is passed by means of a fan over a radiator or over finned tubes and then over the trays. A portion of the air escapes at the discharge opening the remainder is reheated and recirculated. An amount of new air equivalent to the volume discharged is admitted at the fan. Secondary heating tubes are placed in the path of the air to restore their temperature and heat content. In the tray drier, shallow pans 2 ft by 3 ft by 2 in. deep, for example, are placed on a rack, forming part of the drier. In the truck drier, the rack is on wheels, and the whole may be wheeled in and out of the drier. There may be one or several trucks to each drier, and each truck may have twelve, sixteen or more levels for trays. [Pg.140]

Follow the procedures oudined for bare tube equipment, substituting the characteristics of finned tubes where appropriate. The presentation of Wolverine recommends this technique over previous methods. The methods of reference 16 have proven acceptable in a wide number of petrochemical hydrocarbon systems. Figure 10-150 is an example unit in summary form. [Pg.224]

However, this does not necessarily apply to foods which heat by convection. Jowitt quotes both peas in brine and soup as examples where the process time was doubled in a fluidized bed (22 minutes) compared to a steam-heated retort (11 minutes) for the same total process lethality. However, increasing the fluidized bed temperature by 8K resulted in almost equal process times and approximately equal retention of the heat-sensitive vitamin thiamine. Following the heating and holding stages of the sterilisation operation, the cans were cooled in a fluidized bed in which heat was removed by cooling water passed through finned tubes immersed in the bed (Jowitt and Thorne, 1971). [Pg.229]

Figure 8.6. Examples of extended surfaces on one or both sides, (a) Radial fins, (b) Serrated radial fins, (c) Studded surface, (d) Joint between tubesheet and low fin tube with three times bare surface, (e) External axial fins, (f) Internal axial fins, (g) Finned surface with internal spiral to promote turbulence, (h) Plate fins on both sides, (i) Tubes and plate fins. Figure 8.6. Examples of extended surfaces on one or both sides, (a) Radial fins, (b) Serrated radial fins, (c) Studded surface, (d) Joint between tubesheet and low fin tube with three times bare surface, (e) External axial fins, (f) Internal axial fins, (g) Finned surface with internal spiral to promote turbulence, (h) Plate fins on both sides, (i) Tubes and plate fins.
There are various types of finned tubes depending on the application. They are applied, for example, in large air conditioning systems, for radiators of vehicles or where cooling water is in short supply. [Pg.126]

The procedure outlined in this example can also be used when designing equipment using low-fin tubes. The same approach is used when condensing or boiling on the outside of low-fin tubes. [Pg.318]

If hazardous materials must be used and unsafe enviromnents exist, limit the potential for leakage use finned tube heat exchangers for vaporization on the shell side. Develop special procedures during the startup phase, when conditions go through the explosive limits. Measure key variables to trigger safety measures for example, for reactors, include instrumentation to detect temperature runaways. For example, AlChE/CCPS (1995) recommends tPT/df >0 and d (T eacior- Tcooiant)/dt >... [Pg.1332]

Katz et al. [127] and Nakajima and Shiozawa [128], for example, found that coefficients on the upper finned tubes in a bundle are higher than coefficients on the lower tubes as a result of bubble-enhanced circulation. Similar results are reported by Arai et al. [129] for a bundle of Thermoexcel-E tubes. It is quite probable that with certain types of enhanced tubes it is sufficient to use the special tubes only in the lower rows since the bubble-enhanced circulation in the upper rows is so high that enhanced tubes are not effective there. [Pg.807]

Because of the low heat transfer coefiScient usually associated with gases, the gas side surface of heat exchangers are often extended air blown coolers generally employ finned tubes for example. Fig. 7.13 shows how the deposit accumulates on a bank of firmed tubes [Bemrose 1984]. [Pg.87]

Air-cooled heat exchangers are employed on large scale as condensers of distillation columns or process coolers. The approach temperature - the difference between process outlet temperature and dry-bulb air temperature - is typically of 8 to 14 °C above the temperature of the four consecutive warmest months. By air-humidification this difference can be reduced to 5 °C. Air cooled heat exchangers are manufactured from finned tubes. Typical ratio of extended to bare tube area is 15 1 to 20 1. Finned tubes are efficient when the heat transfer coefficient outside the tubes is much lower than inside the tubes. The only way to increase the heat transferred on the air-side is to extend the exchange area available. In this way the extended surface offered by fins increases significantly the heat duty. For example, the outside heat transfer coefficient increases from 10-15 W/m K for smooth tubes to 100-150 or more when finned tubes are used. Typical overall heat transfer coefficients are given in Table 16.10. The correction factor Ft for LMTD is about 0.8. [Pg.635]

Example 2. Using the same basis as the rating example in the radiant section, it is easy to compare plain and finned tubes in the convection section. [Pg.17]

This method differs from the convection section method in the previous example in two z xxs (1) it provides for rating finned tube -riins and (2) it includes credit for radiation ge through the shield coil. The radiation... [Pg.21]

Alternatively, heat pipes may be used to take heat out of highly exothermic reactions. In most cases the heat pipes are close to, or in contact with, separate catalysts. In some examples, the heat pipes could be coated with a catalyst, as for finned tubes (see Chapter 3). [Pg.174]

Example 5.5, If the finned tube in Example 5.4 is placed inside another tube with an inside diameter of 30 mm to form a countercurrent concentric tube heat exchanger, determine the overall heat transfer coefficient for the exchanger when the mass flow rate of the return air at 0.101 MPa and 175 K is 0.094 kg/s. Base the overall heat transfer coefficient on the outside area of the finned tube. [Pg.213]

In this equation, K and hi represent the outside and inside film coefficients of heat transfer of the two fluids Ly, and K the thickness and conductivity of the partition wall and Ri the resistances due to corrosion, dirt, or roughness of the surfaces and Ao, A, and Ay, represent the areas of the wall at the outside, at the inside, and at about the mean of the two (A ). Two fouling resistances are used throughout this book, but most of the literature fails to indicate whether one or both factors are being reported. Accordingly, a single fouling resistance Rd, which is the sum of Ro and iZ will be used in this derivation and no correction for outside and inside surfaces will be made except in such necessary cases as fin-tube resistances (see Example 17-8). [Pg.534]

Example 17-8. Transfer Rate in a Fin-tube Heater. A common type of 24-fin tube has 50.5 sq ft of external finned surface and an internal surface of 8.4 sq ft. The actual ratio of surfaces is... [Pg.565]


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See also in sourсe #XX -- [ Pg.545 ]




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