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Experimental results are presented for the local parameter values in banks of rough - surface tubes in air and transformer oil. Local velocity and velocity fluctuations were measured by X-shaped sensors with a third wire introduced to measure temperature and its fluctuations. Calculated velocity and temperature profiles are given for the region of boundary layer separation.
Possibilities of augmenting the heat transfer of heat exchangers by introducing rough surfaces were explored. The study covered wide range of He and Pr, relative transverse pitch a from 1.25 to 2.0, relative longitudinal pitch b from 0.935 to 2.0, and relative height of surface elements k/d from 6·10⁻³ to 40·10⁻³. Calculation relations are suggested for the average heat transfer and pressure drop of banks of rough-surface tubes for Re from 10² to 2·10⁶.