Experimental investigation of heat transfer and friction characteristics in a circular tube fitted with V-nozzle turbulators

The effects of V-nozzle inserts on heat transfer and friction characteristics in a uniform heat flux tube are experimentally studied. Three different pitch ratios (PR) of V-nozzle arrangements in the test tube are introduced with PR=2.0, 4.0, and 7.0, in each run. The results of experimental investigations of heat transfer, friction characteristic and enhancement efficiency are presented. It is found that using the V-nozzle can help to increase considerably the heat transfer rate at about 270% over the plain tube. A maximum gain of 1.19 on enhancement efficiency is obtained for the smallest pitch ratio used, PR=2.0. This indicates that the effect of the reverse/re-circulation flows can improve the heat transfer rate in the tube. In addition, correlations from the results are presented. (c) 2006 Elsevier Ltd. All rights reserved.