Effect of bath temperature on surface heat flux during quenching in CNT nanofluids

In this paper, the effect of nanofluid temperature on the heat transfer rate has been studied during immersion quenching in Carbon Nanotube (CNT) nanofluid. For this purpose, CNT nanofluid was prepared by suspending 0.25wt% of chemically treated CNTs (TCNT) in de-ionized (DI) water without any surfactant. Quench probes with a diameter of 20 mm and a length of 50 mm were machined from 304L stainless steel and quenched in CNT nanofluid when maintained at 30 °C, 40 °C and 50 °C. The heat flux and temperature at the quenched surface were estimated based on the Inverse Heat Conduction (IHC) method using the measured temperature data during quenching as input. The computation results showed that the peak heat flux increased when the CNT nanofluid was maintained at 40 °C than at 30°C and decreased with further increase in the CNT nanofluid temperature. The enhanced heat transfer performance of CNT nanofluid during quenching at a slightly higher temperature is attributed to the increase in the Brownian motion of CNTs in nanofluid. The reduced heat transfer rate when the CNT nanofluid maintained at 50 °C during quenching was due to the predominant effect of quenchant temperature on quenching heat transfer rate. © 2011 ASM International®.