Filmwise Condensation on Low Integral-Fin Tubes of Different Diameter

摘要

Heat transfer measurements were made for filmwise condensation of R-113, steam and ethylene glycol on three sets of finned tubes which differed only in root diameter. The fin root diameters were 12.7 mm, 19.05 mm and 25.0 mm. A comparison of the enhancement ratios (based on constant vapor-side temperature drop) revealed that, within the range of diameter tested, the effect of root diameter was small. Results indicated that two or more trends may exist while increasing root diameter. With the exception of the small-diameter tubes with steam, a change in root diameter did not effect the optimum fin spacing for each fluid tested. The optimum fin spacing for the small-diameter tubes with steam was approximately 2.0 mm, while the medium- and large-diameter tubes had an optimum fin spacing for each fluid tested. The optimum fin spacing for the small-diameter tubes with steam was approximately 2.0 mm, while the medium- and large-diameter tubes had an optimum fin spacing of 1.5 mm. The optimum fin spacing for R-113 and ethylene glycol was found to be 0.5 mm and 1.0 mm, respectively. A comparison between the outside heat-transfer coefficients of the medium-diameter tubes for R-113 and steam with past NPS investigation showed an agreement within + or - 3 percent and + or - 10 percent, respectively. Keywords: Filmwise condensation, Low integral fin tubes, Modified Wilson plot technique, Heat transfer coefficient. Theses. (MJM)