Tests were conducted in a dry vacuum environment, on eight mechanically expanded finned tube heat exchangers (3/8 inch tubes) with different geometries including variation in fin thickness, fins per inch, and net interference. One of the eight heat exchangers was also tested under wet conditions. A mathematical model was used to calculate the thermal contact conductance from the experimental data. An error analysis was performed to estimate the range of error in determining the thermal contact conductance. A scanning electron microscope was used to examine the contact region between the flat aluminum fin and the copper tube. A correlation of the dry contact conductance in terms of fin number (actual fin collar length in contact with the tubes), fin thickness, net interference, and unexpanded tube diameter was obtained.

Units: I-P