THE THERMAL AND TRANSPORT CHARACTERISTICS OF NANOFLUIDS IN A NOVEL THREE-DIMENSIONAL DEVICE

The augmentation in heat transfer can be achieved by improving either transport phenomena with geometry perturbation or thermal conductivity of the fluid itself. In the present study, the simultaneous effects of both the geometry and improved thermal conductivity have been tried on heat transfer enhancement by using two different nanofluids (Al2O3-water and TiO2-water). An innovative three-dimensional device called a coiled flow inverter (CFI) is proposed for the process intensification. The CFI is made up of helical coiled tube, which is bent periodically to 90 degrees at equidistant length. In addition to a CFI, the performance characteristics of helical coil and straight tube have been investigated. The Reynolds numbers are in the range of 25-4000, while the nanoparticle volume fraction varied from 0.25-4%. It was noted that the heat transfer in a CFI improved considerably as compared to helical coil and straight tube of same dimension. The Nusselt number in helical coil augments by 2.5 times to that of straight tube. In the CFI, the Nusselt number further enhanced by 23-35% as compared to helical coil, with 0-4 % increase in the nanoparticle volume fractions. The new correlations are developed to predict the Nusselt number and friction factor for the flow of nanofluids in the CFI. The number of merit in the CFI to that of straight tube are 1.6-1.8 times, with 0-4 % nanoparticle volume fractions. The present study may motivate the design and development of novel compact heat exchangers as well as a new-generation microfluidic device.