Heat transfer and pressure drop in tube with broken twisted tape insert

An experimental study measuring the axial beat transfer distributions and the pressure drop coefficients of the tube fitted with a broken twisted tape of twist ratio 1, 1.5, 2, 2.5 or infinity is performed in the Re range of 1000 - 40,000. This type of broken twisted tape is newly invented without previous investigations available. Local Nusselt numbers and mean Fanning friction factors in the tube fitted with the broken twisted tape increase as the twist ratio decreases. Heat transfer coefficients, mean Fanning friction factors and thermal performance factors in the tube fitted with the broken twisted tape are, respectively, augmented to 1.28 - 2.4, 2 - 4.7 and 0.99 - 1.8 times of those in the tube fitted with the smooth twisted tape. Empirical heat transfer and pressure drop correlations which evaluate the local Nusselt number and the mean Fanning friction factor for the tube with the broken twisted tape insert are generated to assist the industrial applications. (c) 2007 Elsevier Inc. All rights reserved.