pressure drop and thermal characteristics of cuo–base oil nanofluid laminar flow in flattened tubes under constant heat flux

an experimental investigation has been carried out to study the heat transfer and pressure drop characteristics of nanofluid flow inside horizontal flattened tubes under constant heat flux. the nanofluid is prepared by dispersion of cuo nanoparticle in base oil and stabilized by means of an ultrasonic device. nanofluids with different particle weight concentrations of 0.2%, 0.5%, 1% and 2% are used. copper tubes of 11.5 mm i.d. are flattened into oblong shapes and used as test sections. the nanofluid flowing inside the tube is heated by an electrical heating coil wrapped around it. required data are acquired for laminar and hydrodynamically fully developed flow inside round and flattened tubes. the effect of different parameters such as flow reynolds number, flattened tube internal height and nanofluid particle concentration on heat transfer coefficient and pressure drop of the flow is studied. observations show that the heat transfer performance is improved as the tube profile is flattened. flattening the tube profile resulted in pressure drop increasing. in addition, the heat transfer coefficient as well as pressure drop is increased by using nanofluid instead of base fluid. furthermore, the performance evaluation of the two enhanced heat transfer techniques studied in this investigation shows that applying flattened tubes instead of the round tube is a more effective way to enhance the convective heat transfer coefficient compared to the second method which is using nanofluids instead of the base liquid.