Nanofluids with CNTs for automotive applications

This paper summarizes a recent work on anti-corrosive and enhanced heat transfer properties of carboxylated water based nanofluids. DI water mixed with Sebacic acid (C10H18O4) as carboxylate additive is dispersed with multi walled carbon nanotubes and tested for corrosion and heat transfer characteristics. Corrosion studies made as per ASTM D 1384 show that carboxylate water dispersed with MWCNTs is resistant to corrosion and hence suitable for automotive environment. In addition to MWCNTs, carboxylated water dispersed with nano sized silver, copper and Aluminium oxide are also tested for corrosion performance but found to be giving considerable corrosion in automotive environment. The stability of MWCNT based nanofluids in terms of zeta potential is found to be good with carboxylated water compared to DI water. Significant improvement is observed in the thermal conductivity of nanofluids dispersed with MWCNTs. There is a slight increase in viscosity and marginal decrease in the specific heat of nanofluids with addition of carboxylate as well as MWCNTs. The carboxylated water is dispersed with very low mass concentration of multi walled carbon nano tubes at 0.025, 0.05 and 0.1 % and tested for heat transfer performance. The heat transfer studies are made in Reynolds number range of 2500-6000 in the developing flow regime. The heat transfer performance of nanofluids is carried out on an air cooled heat exchanger similar to an automotive radiator with incoming air velocities across radiator maintained at 5, 10 and 15 m/s. The coolant side overall heat transfer coefficient and overall heat transfer coefficient have improved markedly. It is also found that the velocity of air and flow rate of coolant plays an important role in enhancement of overall heat transfer coefficient. Stanton number correlation for the entire data has been developed. It is found that the wall temperature gradients play an important role in the enhancement of heat transfer when nanofluids are used.