EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF NANOFLUIDS ON FORCED CONVECTIVE HEAT TRANSFER ALONG A MICROCHANNEL
The demand for more compact and efficient heat exchangers has led to the use of microchannels, which allow for smaller, higher surface-to-volume ratio heat exchangers. To further increase efficiency, nanofluids−or fluids with nano-scale particles suspended in them−have become a high interest field of study. These nanofluids allow for more efficient heat exchangers by enhancing its heat transfer coefficient. This paper studies the effect that nanofluid has on forced convection heat transfer coefficient through a microchannel. The variation of heat transfer coefficient was experimentally measured for various nanofluids. Numerous stock nanoparticles were tested, as well as a custom-synthesized semiconductor TiO2 particle with anatase crystal phase. The data was then examined for the effect nanofluids had on forced convection heat transfer coefficient with respect to the dimensionless length, x/D. The experiment pushes the nanofluid through a stainless-steel microchannel with inner diameter of 0.31mm. Thermocouples were attached at the pipe inlet and outlet, as well as along its surface to obtain the thermal profile. The pipe and thermocouples were thermally insulated, and a DC current was used to generate a constant heat flux through the pipe. The input power, absorbed power, local heat transfer coefficient, and Nusselt number can be calculated through the gathered measurements. By using nanofluids, the developed heat transfer coefficient could be increased by over 143%. It was also found that higher Reynolds numbers led to higher developed heat transfer coefficients in nanofluid trials; a 160% increase was observed for TiO2-water nanofluid at Re=400 over Re=100.