Effect of geometrical parameters on the performance of nanofluid-based single phase natural circulation mini loops

Abstract

Single phase natural circulation loops are widely used passive systems in heat transfer applications. Since achievement of stable flow and highly efficient heat transfer is the main concern of recent studies, effects of geometry and the working fluid on the single phase natural circulation loops’ performance are getting attention. In this study, aspect ratio and pipe diameter effect on thermo-hydraulic performance of mini SPNCLs (SPNCmLs) has been investigated numerically by developing a 3D steady model. Water based Al2O3 nanofluid (1, 2, 3 vol. %) was used as a working fluid. Performance and characteristics of the loop for different working fluids is evaluated by using temperature distributions, mass flow rates and derived non-dimensional parameters. It is shown that pipe diameter effect on the heat transfer performance is more significant compared to aspect ratio. Moreover, nanofluids have higher temperatures and thus effectiveness values compared to water. In order to generalize the SPNCmL performance Num and Ress correlations were developed within the accuracy of ±10%.