ABSTRACT
Finned-tube heat exchangers have been used for heat exchange between gases and liquids (single or two phase) for many years. Figure 6.1a and b shows two important finned-tube heat exchanger construction types. Figure 6.1a is the plate fin-and-tube geometry, and Figure 6.1b shows individually finned tubes. Although round tubes are shown in Figure 6.1, oval or flat tubes are also used, for example, in automotive radiators. A plain air-side geometry is shown in the Figure 6.1 geometries. Figure 6.1a and b show a staggered tube arrangement, which provides higher performance than an inline tube arrangement. Externally finned tubes are also frequently used for liquids. Figure 6.1c shows an integral-fin tube used for liquids. However, extended surfaces for liquids typically use lower fin height than for gases. Because liquids have higher heat transfer coefficients than gases, fin efficiency considerations require shorter fins with liquids than with gases. When used with liquids, the fin height is typically in the 1.5 to 3 mm range. The dominant amount of material in this chapter is applicable to high fins, which are used for gases.
