Experimental Investigations of Longitudinal and Twisted Tape Inserts for Augmentation of Heat Transfer

In the past decade, heat transfer enhancement technology was developed and widely applied to heat exchanger applications like refrigeration, automotives, process industry, solar water heater etc. There has been a great attempt to reduce the size and cost of the heat exchanger, and energy consumption. The most significant variable in reducing the size and the cost of the heat exchanger is the heat transfer coefficient and pressure drop. At present, the technology of the Twisted-Tape Inserts [1] to heat exchangers is widely used in various industries. Insertion of twisted tapes in a tube provides a simple passive technique for enhancing the convective heat transfer by introducing swirl into the bulk flow, and by disrupting the boundary layer at the tube surface, due to repeated changes in the surface geometry. The present work is a practical attempt made to study the influences of the twisted tape inserts on the heat transfer coefficient (h) and friction factor (f) in a double pipe U bend heat exchanger. The experimental work is done by considering various twisted tapes with different Twist Ratios from 5 to 20. The effect of inserts is studied with the variation of Reynolds Number (Re) from 3000 to 30000. The main objectives of the work include estimation of heat transfer and friction factor in double U-bend heat exchanger, comparison of the heat transfer and friction factor for counter flow and parallel flow in the double pipe U-bend heat exchanger, understanding the effect of twisted tape insert inside the flow for heat transfer augmentation and friction factor, comparison of the heat transfer with and without twisted tape inserts.