AC-2742 -- Heat Transfer and Pressure Drop during Condensation Inside Horizontal Tubes with Twisted-Tape Inserts PDF

The paper reports the results of an experimental investigation in which heat transfer and pressure drop data were taken during condensation of R-113 inside three horizontal tubes. One tube was smooth, and two had twisted tape inserts with different pitch-to-diameter ratios. The smooth tube was used as a basis for comparison with the data of the tubes with twisted tape inserts. Over the mass flux range tested, the twisted tape inserts enhanced the heat transfer coefficients by as much as 23% over the smooth tube, on a nominal area basis. A correlation equation was proposed for predicting the overall average heat transfer coefficient during condensation inside tubes with twisted tape inserts. The proposed correlation predicted most of the experimental data of the present study and studies of other investigators to within +/-30%. The pressure drop data were satisfactorily correlated by existing correlations.