Comparative thermal hydraulic performance analysis on helical screw insert in tube with different number of strips in transition flow regime

Abstract

The experimental analysis is arranged to evaluate thermal hydraulic performance on flow of fluid in the tube with helical screw inserts at numbers of strips and different values of twist ratio at transition flow regime. Single strip helical screw insert is also compared with double strip helical screw inserts at values of twist ratio. Further, the CFD analysis is carried out to visualize thermohydraulic characteristics on present analysis with k−kl−w model. The Nusselt number is shown enhancement with double strip than single strip helical screw inserts at increased values of Reynolds number and decreased values of twist ratio. Friction factor is found enhancement with double strip than single strip helical screw inserts at decreasing values of Reynolds number and twist ratio. A maximum enhancement of 2.82 times in value of Nusselt number is achieved with double strip helical screw inserts at twist ratio of 1.5 and Reynolds number of 2300 as compared with plain tube. Further, common correlations of Nusselt number and friction factor are also developed. Higher enhancement in the values of thermal performance factor is achieved with double strip than single strip helical screw inserts. A maximum value of thermal performance factor of 1.29 is achieved with double strip helical screw insert at twist ratio of 2.5 and low value of Reynolds number. It is observed that double strip helical screw inserts show suitability for miniaturization of heat exchanger which could be beneficial for efficient thermal applications as solar water heater, electronic cooling devices, automobile radiator, power plants etc.