Abstract
Experiments were carried out on water flowing turbulently inside each of the four following electrically heated pipes: 1. 1" inside diameter smooth circular pipe with a long calming section. 2. The same pipe fitted with a series of turbulence promoters made from spirally twisted strips having differing pitches. 3. 3/4 inch square pipe with a long calming section. 4. A Row Indented tube. In case (1), the local coefficients of heat transfer were calculated and the results correlated by empirical equations based on the dimensional analysis. For cases (2) and (3), the local coefficients of heat transfer were likewise calculated, and then plotted against the pipe length for different Reynolds number. After a dimensional analysis of results (for the average coefficient of heat transfer) in the case of promoters, those results Were correlated with those in previous research on air flowing inside pipes having different diameters and promoters of different pitches. In the case of the square pipe, the average coefficients and the coefficients of the tube of infinite length were correlated by the methods of both Dettus & Boelter, and Sieder & Tate, by the use of the hydraulic diameter in the dimensionless groups. For the Row tube the average coefficients of heat transfer were correlated as functions of mass flow rate. Finally, the effect of super or abnormal turbulence on the saving of power was also studied, by the plotting of the ratio of power (at the same coefficient of heat transfer) between the plain and fitted tubes against the coefficient of heat transfer.