Heat-transfer measurements have been made on three pairs of tube bundles. The bundles of a pair are identical except that plain tubes are used in one bundle and finned tubes in the other. The finned tubes have from 2.07 to 2.76 times as much outside surface as the plain tubes. Heat-transfer measurements were made for water, lubricating oil, and glycerine on the shell side. Several temperature levels and temperature differences were used to give a variety of viscosities and other fluid properties. Shell-side coefficients were determined by extrapolating to infinite water velocity the over-all coefficients for a series of water velocities inside the tubes. These shell-side coefficients are correlated by the following equation
The values of C depend upon the bundle and vary from 0.225 to 0.143. The pressure-drop data are correlated by the methods presented by Donohue. The heat transferred per degree of temperature difference for the clean finned-tube bundles varied from 110 per cent of that for the corresponding plain-tube bundles for water to 200 per cent for the lubricating oil. For the same mass velocity, the shell-side coefficients for the finned tubes based on the outside area are approximately 80 ± 20 per cent of the plain-tube coefficients. In all cases, at the same mass velocities the pressure drop is less for the finned-tube bundles.
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