Free convection condensation heat transfer of steam on horizontal square wire wrapped tubes

New experimental data are reported for the condensation of steam on square wire wrapped on horizontal instrumented copper tube. 0.8 mm square cross-section wires made of copper and brass and 1.0 mm square cross-section wire made of copper with pitches of 2.0 mm, 4.0 mm and 6.0 mm are used. For both 0.8 mm and 1.0 mm square cross-section wire wrapped tubes, best performing pitch was found to be 4.0 mm i.e. 1.53 and 1.5 for 0.8 mm and 1.0 mm square wire wrapped tubes respectively. The effect of thermal conductivity was evident in case of 0.8 mm (copper and brass) square wire wrapped tube at all pitches tested with significance at 2.0 mm pitch. Compared to equivalent round cross-section wire wrapped tubes, 0.8 mm square wire wrapped tubes showed lower heat transfer enhancement than 0.8 mm diameter round wire wrapped tubes while heat transfer enhancement was higher for 1.0 mm square wire wrapped tubes than 1.0 mm diameter round wire wrapped tubes i.e. 13.4%, 7.1% and 3.7% higher enhancement than the round wire wrapped tubes at 2 mm, 4 mm and 6 mm respectively.