Development of Correlations for Friction Factor and Heat Transfer Coefficient for Square and Hex Duct with Twisted Tape Insert in Laminar Flow

The experimental and numerical investigations of heat transfer and friction factor characteristics for laminar flow through a non-circular duct with twisted-tape have been presented. The non-circular ducts include square duct and hexagonal duct. The results of non-circular ducts are compared with circular duct. All the ducts under investigations have same hydraulic diameter. The twist ratios used for the experiments are (Y= 3.5, 4.5, 5.5, 6.5). Experiments and CFD investigations were carried out on square duct, hexagonal duct and circular duct. The result reveals that, both Nusselt number and friction factor increases as the side of non-circular duct increases. Maximum Nusselt number and friction factor is obtained in case of circular duct with twisted tape.