Water/TiO2 nanofluid flow heat transfer and pressure drop through ducts with circular, square and rectangular cross-sections

Energy costs have soared rapidly in the last decades. Thus there is a tremendous need for new kinds of working fluids to improve the heating systems performances and to reduce energy consumption. One of the most applicable heating systems are heat exchangers. Study of thermal hydraulic characteristics for laminar fully developed flow through conduits with different cross-sections is significant in the design of heat exchangers. In the present investigation, the thermo-hydraulic behavior of nanofluid trough conduits with circular, square and rectangular cross sectional shapes is studied, experimentally. This investigation aims to study the effect of Reynolds number and shape of cross-section on heat transfer and pressure drop of nanofluid flow. The experiments were conducted for TiO2/water nanofluid with three volume fractions 0, 0.2 and 0.5 under laminar flow regime with constant wall temperature. Analyzed data indicate that friction factors of square and rectangular cases are more than that of circular cross section. Also, it is seen that the addition of nano powder with low volume fraction (0-0.5%) to base fluids does not increase the friction factor remarkably at both circular and non-circular cases. The results show that the Nusselt number of flow through the conduit with circular cross-section is higher than that of non-circular cases. Moreover, it is observed that adding nano powder o base fluid improves heat transfer in sharp corners and therefore its effect is more pronounced in non-circular cross sections.