Improvement in performance of heat exchanger fitted with twisted tape

The improvement in performance of a double pipe heat exchanger fined with t wisted tape as a turbulence promoter with twist ratios of 15.649, 8.54, 5.8 82, 4.95, and 4.149 was experimentally studied. A maximum percentage gain o f 44.7% in energy transfer rate was obtained for the twisted tape of twist ratio 4.149. For all twist ratios, the gain decreases with the Reynolds num ber and becomes constant for Reynolds numbers greater than 3,000. The small er the twist ratio is, the larger the gain in energy for a specific Reynold s number.