Effect of vapor velocity on condensation of low-pressure steam on integral-fin tubes

Experimental data are presented for forced-convection condensation of low-pressure steam on a set of single, integral-fin tubes. The five tubes had fin-root diameter of 12.7 mm and identical fin geometry except for fin spacing, which was varied from 0.25 mm to 2 mm. The range of vapor velocity was 14.7-62.3 m/s at an absolute pressure of 14 kPa. Heat-transfer enhancement was a strong function of both vapor velocity and fin spacing, and the interrelationship of the two parameters led to complex trends in the data. Observations of the extent of condensate flooding (i.e., condensate trapped between the fins at the bottom of the tube) indicated that the effect of vapor shear on flooding was a significant controlling factor in the heat-transfer process, and this factor explained, at least quantitatively, the trends observed.