Heat transfer and hydraulic characteristics of micro finned tube inserted with twisted tape inserts and hybrid nanofluid (CNT/Al₂O₃)

This paper communicates the enhancement of heat transfer, friction characteristics and thermal performance of micro finned tube fitted with Left/Right and regular insert tape inserts using CNT and CNT/Al₂O₃ nanofluid. Two different concentrations of nanoparticles were used in the present investigation. In contrast, the CNT/Al₂O₃ nanoparticles are mixed in a weight ratio (50:50) and sonicated for about 2 hours using a bath type sonicator. The prepared nanofluids are stable for almost 48 hours without any sedimentation. Results show that the increase in nanoparticle concentration in the base fluid increases the performance index under turbulence flow regime while the Reynolds number in the range of 2000< Re<5500. Similarly, the Nusselt number and friction increase by 250% and 400%, respectively, with the maximum concentration of nanoparticle and minimum twist ratio. Results also reveal that the use of alternate arrangement increases the turbulence for maximum friction gain and improvement in the convective heat transfer coefficient.