Hydronic Coil Performance Evaluation With Nanofluids and Conventional Heat Transfer Fluids

The performance of hydronic heating coils with nanoparticle enhanced heat transfer fluids (nanofluids) is evaluated and compared with their performance with a conventional heat transfer fluid comprised of 60% ethylene glycol (EG) and 40% water, by mass (60% EG). The nanofluids analyzed are comprised of either CuO or $Al2O3$ nanoparticles dispersed in the 60% EG solution. The heating coil has a finned tube configuration commonly used in commercial air handling and ventilating systems. Coil performance is modeled using methods that have been previously developed and validated. The methods are modified by incorporating Nusselt number correlations for nanofluids that have been previously documented in the literature. Similarly, correlations for nanoparticle thermophysical properties that have been documented in the literature are employed. The analyses show that heating coil performance may be enhanced considerably by employing these nanofluid solutions as a heat transfer medium. The model predicts a 16.6% increase in coil heating capacity under certain conditions with the 4% $Al2O3$/60% EG nanofluid, and a 7.4% increase with the 2% CuO/60% EG nanofluid compared with heating capacity with the base fluid. The model predicts that, for a coil with the $Al2O3$/60% EG nanofluid, liquid pumping power at a given heating output is reduced when compared with a coil with the base fluid.