A Study of Three Tube Arrangements in Unbaffled Tubular Heat Exchangers

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Abstract
Pressure-drop and heat-transfer tests, using a medium-viscosity oil in viscous flow across vertical tubes in three unbaffled exchangers, are reported in the course of a research program on tubular exchangers. The three once-flow-through units have, respectively, equilateral triangular, in-line square, and staggered square tube arrangements, but, in all other respects, are as nearly identical as possible. Heat-transfer data for three bulk-oil temperatures and a constant, but lower, tube-wall temperature, and both isothermal and nonisothermal pressure-drop data at three temperature levels are reported. The two staggered-tube arrangements provide greater heat transfer at a given pumping power loss than the in-line arrangement in the region of viscous flow, but this superiority decreases at higher velocities and may disappear in turbulent flow as previous data have indicated. A correction is presented for the effect of viscosity gradient upon friction during heat transfer but this correction does not allow for free convection or nonuniform flow.

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