Experimental study of forced convective heat transfer of nanofluids in a microchannel

The forced convective heat transfer for flow of water and aqueous nanofluids (containing colloidal suspension of silica nanoparticles) inside a microchannel was studied experimentally for the constant wall temperature boundary condition. Applications of nanofluids have been explored in the literature for cooling of micro-devices due to the anomalous enhancements in their thermo-physical properties as well as due to their lower susceptibility to clogging. The effect of flow rate on thermal performance of nanofluid is analyzed in this study. Variations of thermo-physical properties of the nanofluid samples were also measured. The experimental results show that heat transfer increases with flow rate for both water and nanofluid samples; however, for the nanofluid samples, heat transfer enhancements occur at lower flow rates and heat transfer degradation occurs at higher flow rates (compared to that of water). Electron microscopy of the heat-exchanging surface revealed that surface modification of the microchannel flow surface occurred due to nanoparticle precipitation from the nanofluid. Hence, the fouling of the microchannels by the nanofluid samples is believed to be responsible for the progressive degradation in the thermal performance, especially at higher flow rates. Hence, these results are observed to be consistent with previous experimental studies reported in the literature.