Many options are devoted to enhancing heat transfer alongside lowering the pressure drop inside
the tube banks in cross flow with air. Among these, is attaching splitter plates (SPs) to the trailing
edges of the tubes as extended surfaces. That already proved from literature its effective use.
Another proposed option is to increase the surface’s roughness, with limited available data from
literature. Thus, the present research was established to study the effect of using different surface
roughness of a staggered tube-bank in cross flow with air on heat transferred and pressure drop
besides the comparison with installing SPs. To this aim, a full 3D CFD model is developed to study
the two mentioned options without any symmetrical boundary conditions. The study extended to
include the effect of Remax changes from 5000 to 100,000. While three surface relative roughness;
ks/D = 0 (smooth), ks/D = 0.01, and ks/D = 0.02 are investigated. The results confirmed that
increasing heat transfer surface roughness helps to augment the total heat transferred. While a
limited pressure drop increase is reported compared to installing SPs. Combining both; increasing
surface roughness, and, adding SPs, led to multiplying the total heat transfer rate. |
