Heat transfer characteristics of automatic transmission nanofluid with twisted tape: an experimental study

Automatic transmission fluid (ATF) is a versatile fluid used in automobiles for cooling, torque converter application, and lubrication purposes. In this paper, the effects of simultaneous utilization of titanium dioxide nanoparticles and twisted tapes on heat transfer as well as pressure drop characteristics of ATF flow have been investigated experimentally. Thermophysical properties of nanofluids were measured experimentally. Moreover, different parameters effects such as nanoparticle mass concentration (0.5%, 1%, and 2%), twist ratio of tapes (10, 20), and the Reynolds number (70-640) on pressure drop and heat transfer were investigated. According to the results, an increment in nanoparticle mass concentration and the Reynolds number led to an increase in pressure drop and heat transfer. Further, both the pressure drop and heat transfer increased by decreasing the twist ratio of the tapes. The maximum increase in convective heat transfer occurred by 127% at the Re number of 262 for the nanofluid with 2% mass fraction and twisted tape 2 (with a twist ratio of 10) compared to the base fluid and plain tube. Considering both the heat transfer and pressure drop by calculation of mean energy ratio at all Reynolds numbers, the nanofluid with 1% of mass fraction along with twisted tape 2 (with mean energy ratio of 1.252) showed the best performance.