Experimental studies on heat transfer augmenatation Using modified reduced width twisted tapes (RWTT) as Inserts for tube side flow of liquids

Abstract

This project report deals with the use of modified twisted tape inserts as Passive Heat transfer augmentation device. Effect of Reduced width twisted tape (RWTT), Baffled Reduced width twisted tape (BRWTT1) & Baffled Reduced width twisted tape with holes (BRWTT2) on heat transfer and friction factor for heating of water for Reynolds number range 2500-30000, was studied experimentally in a double pipe heat exchanger. Three tapes of different twist ratio
(yw=3.69, yw=4.39, yw=5.25) for RWTT, BRWTT1 & BRWTT2 were used. Based on constant flow rate, the heat transfer coefficient were found to be 1.18-3.66, 2.61-7.07 & 3.58-8.08 times the smooth tube values for RWTT, BRWTT1 & BRWTT2 respectively. The friction factor values were found to be 3.23-5.96, 7.79-11.23 & 8.86-14.44 times the smooth tube values for RWTT,BRWTT1 & BRWTT2 respectively. Based on constant pumping power, the heat transfer coefficient values were found to be 0.88-1.62, 1.59-3.70 & 2.12-4.49 times the smooth tube values for RWTT, BRWTT1 & BRWTT2 respectively. Based on the increase in Heat transfer
coefficient, Performance evaluation criteria R1 & R3, it was concluded that Baffled Reduced width twisted tape & Baffled Reduced width twisted tape with holes performs much better than the Reduced width twisted tapes(RWTT) of the same twist ratio.