Forced convection heat transfer of non-Newtonian MWCNTs nanofluids in microchannels under laminar flow

Heat transfer process in micro/mini-scales becomes an urgent need for many applications where size and weight are severe constraints such as electronics. However, the latter led to developing new thermal fluids, the so-called nanofluids, with enhanced thermophysical properties to cover the high heat dissipation requirements due to the devices' miniaturization. In this work, a validated computational model is used to establish guidelines for the compact heat exchanger with microchannels, as well as to assist nanofluid properties tailoring. A finite volume method (FVM) approach is built considering laminar fluid flow conditions in a circular microchannel. The latter is used and validated against available experimental data, and the influence of temperature-dependent thermophysical properties and non-Newtonian behaviour of the MWCNTs (Multi-walled carbon nanotubes) nanofluids are considered. The results show that MWCNTs nanofluids enhance the heat transfer performance of the micro heat exchanger by up to 33%. Moreover, particular operating conditions are seen to improve the system energy efficiency, mainly near to Reynolds number (Re) equal to 1000, when taking into account both heat transfer performance and pressure drop. Additionally, a correlation of the average Nusselt number is proposed to estimate the heat transfer performance of nanofluids in microchannels.