Heat transfer enhancement using surfactant based alumina nanofluid jet from a hot steel plate

•Addition of Tween 20 to alumina nanofluid enhanced the thermal conductivity up to 21%.•The lowest viscosity value and the highest drop in contact angle were observed at 55ppm.•An optimum cooling rate of 139°C/s was obtained at 55ppm with a CHF of 2.93MW/m2.•Cooling rate in UFC region was attained at 55 and 70ppm concentration of Tween 20.•This enhanced cooling rate can be beneficial for the production of high quality steel. Enhancement of thermal conductivity by the addition of nanofluid is found to improve the rate of cooling of a steel plate. In the present research work, alumina nanofluid at the previously optimized concentration of 10ppm along with a non–ionic surfactant is employed for jet impingement cooling. The steel plate (100×100×6mm) is cooled from an initial surface temperature of 900°C. The concentration of non-ionic surfactant polyoxyethylene (20) sorbitan monolaurate (Tween 20) is optimized, and the surfactant is characterized based on its thermal properties. A maximum thermal conductivity enhancement of 21% and a minimum contact angle of 40.48° were exhibited by surfactant added nanofluid at 55ppm. Inverse heat conduction method was employed to estimate the heat flux and temperature at the plate surface based on the internal thermocouple data. A maximum heat transfer rate of 139°C/s with a critical heat flux (CHF) of 2.93MW/m2 was attained at a surfactant concentration of 55ppm. SEM and EDAX analysis of the plate surface after jet impingement confirmed the presence of the nanoparticles.