Abstract
Experiments were performed to study the flow characteristics and heat transfer during condensation of R11 and R113 in horizontal annuli with an enhanced inner tube. The inner tube was a 19.1 mm o.d. corrugated tube with soldered wire fins on the outer surface. The outer tubes were 24.8, 27.2 and 29.9mm i.d. smooth tubes. The mass velocity of the test fluids ranged from 50 to 300 kg/m2s, and the condensation temperature difference from 0.7 to 20 K. The frictional pressure gradient was correlated fairly well by using the Lockhart and Martinelli parameters. The local heat transfer coefficient was 2 to 18 times as large as those for horizontal annuli with smooth and corrugated inner tubes. An empirical equation for the local heat transfer coefficient was developed, where the dimensionless parameters based on the surface tension drained flow and the vapor shear drained flow models were introduced for the low and high vapor velocity regimes, respectively.
