Augmentation of Heat Transfer in Tubes by Use of Mesh and Brush Inserts

This paper summarizes the results of a study to determine the heat transfer and pressure drop characteristics of two types of tube inserts developed specifically for augmenting heat transfer and accommodating high heat fluxes. The best performing mesh-insert tubes exhibited heat transfer coefficients nine times the coefficients with empty tubes while brush-insert tubes had coefficients averaging five times the empty tube values, both comparisons being made at equal mass velocity. Both inserts produced very large pressure drops. Subcooled boiling curves and burnout points are presented; burnout heat fluxes are two to three times the empty tube values at equal mass velocity. For single-phase conditions and for burnout, the mesh and brush tubes have favorable performance characteristics, based on pumping power, which suggest use of these inserts in certain special cooling systems.