HEAT TRANSFER MEASUREMENTS FOR FLOW OF NANOFLUIDS IN MICROCHANNELS USING TEMPERATURE NANO-SENSORS
- Additional Document Info
- View All
Experiments were performed to study the forced convective heat transfer of de-ionized water (DI water) and aqueous nanofluids in a microchannel and temperature measurements were obtained using an array of nanosensors (i.e., thin film thermocouples or "TFT"). Heat flux values were calculated from the experimental measurements for temperature recorded by the TFT array. The experiments were performed for the different test fluids where the flow rate, mass concentration (of silica nanoparticles ~10-30 nm diameter) in the colloidal suspension and the wall temperature profile (as well as applied heat flux values) were varied parametrically. Anomalous enhancement of the convective heat flux values were observed for the different experimental conditions. Precipitation of nanoparticles on heat exchanging surfaces was confirmed using materials characterization techniques such as Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray spectroscopy (EDX). It is suggested that moderate precipitation of nanoparticles lead to formation of isolated nanofins which cause the observed enhancements in forced convective heat transfer (due to increase in the effective surface area), while excessive precipitation results in scaling (fouling) of the surface which causes degradation of the heat flux values (compared to that of the pure solvent). This study shows that the surface conditions play a dominant role in determining the efficacy for heat transfer in multi-phase flows - particularly those involving nanoparticle coatings and nanoparticle suspensions (compared to the bulk properties of the test fluid itself).
author list (cited authors)
Yu, J., Kang, S., Jeon, S., & Banerjee, D.