Finned-Tube Construction

For the general case, the treatment suggested by Kern (Pmcc.s.s Heat Transfer, McGraw-Hill, New York, 1950, p. 512) is recommended. Because of the wide variations in fin-tube construction, it is convenient to convert all film coefficients to values based on the inside bare surface of the tube. Thus to convert the film coefficient based on outside area (finned side) to a value based on inside area Kern gives the following relationship ... 

Finned-Tube Construction The following are descriptions of commonly used finned-tube construc tions (Fig. 11-45). 

Typical metal design temperatures for these finned-tube constructions are 399°C (750°F) embedded, 288°C (550°F) integral, 232°C (450°F) overlapped footed, and 177°C (350°F) footed. 

Counterclockwise from top (1) Extruded fins offer high performance, reliability, and economy. (2) Hy-Fin extruded-serrated fins represent the state-of-the-art in fin tube construction technology. (3) Imbedded fins are recommended for applications involving high process temperatures. (4) L-base wrap-on fins offer low initial cost for applications involving low process temperatures. 

Air-cooled condensers employ axial-flow fans to force or induce a flow of ambient air across a bank of externally finned tubes. F inned tubes are used because air is a poor heat transfer fluid. The extended surface enables air to be used economically. Several types of finned-tube construction are available. The most common types are extruded bimetallic finned tubes and fluted tension-wound finned tubes. The most common fin material is aluminum. 

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