Experimental investigation of heat transfer augmentation inside double pipe heat exchanger equipped with reduced width twisted tapes inserts using polymeric nanofluid
In this study, we report a further enhancement in heat transfer coefficients of base fluid in combination with structural modifications of tape inserts. Polyvinyl Alcohol and TiO2 with mean diameter of 15 nm were chosen as base fluid and nano particles, respectively. The experiments are carried out in plain tube with four longitudinal internal fins and reduced width twisted tape (RWTT) inserts of twist ratio varying form 2 5 and width of 12 16. Experiments are undertaken to determine heat transfer coefficients and friction factor of TiO2/PVA nanofluid up to 2.0 volume concentration at an average temperature of 30 degC. The investigations are undertaken in the Reynolds number range of 800 30,000 for flow in tubes and with tapes of different width length ratios. The experiments was verified with well known correlations. The average Nusselt number and friction factor in the tube fitted with the full length twisted tapes at y/w 3.0, and 5.0, are respectively 50 130, and 30 95 higher than those in the plain tube; 90 220 and 100 270 when the working fluid is nanofluid, respectively. For the reduced width twisted tapes, the heat transfer rate is decreased with decreasing tapes width. The average Nusselt numbers in the tube fitted with the RWTT of 16, 14 and 12 are respectively, 210 390, 190 320 and 170 290 of that in the plain tube. With the similar trend mentioned above, RWTT with higher width length yield higher thermal enhancement factor in comparison with smaller width. The use of RWTT led to the highest thermal performance factor up to 1.75. Maximum thermal performance factor which was obtained belonged to twists with twist ratio of 2 and width of 16 with ph 0.5 and Reynolds number range of 800 30,000.