ABSTRACT
Internally finned tubes are primarily used for liquids, although they may also be used for pressurized gases. An example for in-tube gas flow is an air compressor intercooler. Internally finned tubes used for condensation and vaporization inside tubes are discussed in Chapters 13 and 14, respectively. Because liquids have higher heat transfer coefficients than gases, fin efficiency considerations require shorter fins with liquids than with gases. Figure 8.1a and b show internally finned tubes having integral internal fins. These tubes are made with either axial or helical fins. The thermal conductance per unit tube length is η ohA/L. Typical finned surfaces provide an A/L in the range of 1.5 to 3 times that of a bare tube. Fin efficiency concerns will limit the practical fin height for use with liquids. For plane fins, the fin efficiency is given by η f = tanh ( m e ) m e https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203017869/ad7a3d2e-98c7-4744-b815-65a29ae4191e/content/equ8_1.tif"/>
