Heat transfer and friction factor characteristics are studied for water flowing through the tube in tube heat exchanger for two different configurations, namely,(1) twisted tape with pins and (2) twisted tape with pins bonded to the inner surface of the test section. Experiments are carried out for different twist pitch to the width of the twisted tape ratios (y/w) for both configurations. But very few research works have been done based on the mentioned heat transfer enhancement techniques. This paper presents the effect of twisted tape with pins on the heat transfer for a fully developed turbulent flow. Experiments are conducted by maintaining constant wall temperature. The heat transfer rate and pressure drop is found to be high for configuration (2) of y/w=3.33 when compared to all other configurations. The empirical correlations developed for different twisted tape with pins results in ±7.28% deviation for Nusselt number and ±7.16% for friction factor.

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This paper presents the effect of bonding and without bonding of wire coiled coil matrix turbulator on the heat transfer for a fully developed turbulent flow. Experiments are conducted by maintaining constant wall temperature. Tests are performed on 3 different wire coiled coil matrix turbulators of different pitches of 5, 10 and 15 mm without bonding of the turbulator. Three similar types of heat exchangers are fabricated and the wire coiled coil matrix turbulators with different pitches of 5, 10 and 15mm are inserted in the heat exchangers and bonding is done on the surface of the tube section. Results have indicated that the heat transfer rate enhances inversely with the pitch of the wire coiled coil matrix turbulator with bonding. With a pitch of 5 mm, the turbulators without bonding have resulted in almost 25.4% enhancement when compared with plain tube. On the other hand, for pitches of 10 mm and 15 mm the enhancement were 20.7% and 16.8%, respectively. The empirical correlations developed for turbulators with and without bonding results in ±6% deviation for Nusselt number and ±3% for friction factor. Similarly with a pitch of 5 mm, the turbulators with bonding have resulted in almost 42% enhancement. For pitches of 10mm and 15mm the enhancements were 34.7% and 25%, respectively