Heat-Transfer Enhancement of Twisted-Tape Inserts in Turbulent Pipe Flows

摘要

Experimental data of liquid and vapor flows of R113 for Re = 5,000-400,000 were obtained for both a plain tube and tube with snugly fitted twisted-tape inserts. No evidence of tape fin effects was found in the heat-transfer characteristics of a stainless-steel tape insert when compared to a Teflon-tape insert. For twist ratios γ = 5.9, 10.0, and 16.0, improvements in heat transfer of up to 35 percent were observed. Based on a simple consideration of the heat-transfer enhancement mechanisms of twisted-tape inserts, a Dittus-Boelter-type correlation for a plain tube was modified to include twisted-tape effects. For such a case, use of available plain-tube data were recommended to maximize the accuracy of the proposed correlation. The trade-off between pressure loss and heat-transfer enhancement was considered to determine the overall desirability of twisted-tape inserts.