Investigation of the combined effect of appendages and axial power profile on post-dryout heat transfer in tubes

An experiment has been performed to obtain post-dryout temperature measurements in two vertical Inconel-600 tubes cooled with an upward flow of Refrigerant-134a. One of these tubes exhibited a uniform axial power profile, while the other had a non-uniform axial power profile. The tube with a non-uniform axial power profile was tested in two vertical positions providing measurements in two different profiles. Experiments were carried out in plain and appendage- equipped tubes. The objective of this study is to examine the combined effect of appendages and axial power profile on post-dryout heat transfer. The result shows a strong impact of flow obstacle (shape, size, and pitch) on post-dryout temperature. The effect of axial power profile is noticeable at the developing post-dryout region (attributed mainly to the variation in CHF occurrence), but appears diminishing at the fully developed post-dryout region.