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Abstract: In this paper experimental investigations on convective heat transfer and pressure drop characteristics in a novel electronic heat sink fitted with dynamic mixers using water and Al2O3/water nanofluid are presented. For this, Al2O3 nanoparticles of average size 47nm are synthesized using microwave assisted chemical precipitation method and characterized using XRD and SEM. Heat transfer and pressure drop characteristics of water and nanofluid are studied in the electronic heat sink of base size 60mm×60mm made of copper with and without the dynamic mixer. The enhancements in the heat transfer and pressure drop results are compared with water and the heat sink without any mixer. The results reveal that there is significant increase in the convective heat transfer when the dynamic mixer is used for enhancing the heat transfer and further increase in heat transfer is found for the nanofluid. The rise in pressure drop compared with the increase of heat transfer is less. [Copyright &y& Elsevier]

Abstract: An experimental investigation on the convective heat transfer and friction factor characteristics in circular tube with spiraled rod inserts (pitch=15mm, 30mm) under turbulent flow with constant heat flux is carried out with distilled water and Al2O3/water nanofluids. For this purpose, Al2O3 nanoparticles were synthesized by using chemical precipitation method. The average size of particle is found to be 40.3nm. The nanoparticles are then dispersed in distilled water to form stable suspension of Al2O3/water nanofluids with 0.3, 0.4 and 0.5% volume concentration of nanoparticles. It is found that (i) heat transfer enhancement is caused by suspending nanoparticles and becomes more pronounced with the increase of the particle volume concentration (ii) the Nusselt number for spiraled rod inserts under turbulent flow showed an increase of about 10–48% compared to the Nusselt numbers obtained with plain tube (iii) the isothermal pressure drop for turbulent flow with spiraled rod inserts were found to be between 2 and 8% higher than the plain tube. [Copyright &y& Elsevier]

The aim of this study is to investigate the enhancement of thermal performance characteristics in a plain tube fitted with helical screw louvered rod inserts using water and carbon nanotube (CNT)/water nanofluids of 0.1%, 0.2% and 0.5% volume concentration under turbulent flow condition. In the experiments, the swirling flow was introduced by using helical screw louvered rod inserts arrangements (forward and backward) inside the inner test tube with different twist ratios, Y = 1.78, 2.44 and 3.0. The experimental results revealed that the increase in heat transfer rate of the helical screw louvered rod insert was found to be strongly influenced by turbulence or vortex motion. The use of helical louvered rod inserts in plain tube causes intensification in heat transfer compared to plain tube for a given Reynolds number, while the Friction Factor was higher which increases with decrease in twist ratio. The maximum thermal performance factor value of 1.23 was found with the use of CNT/water nanofluid of 0.5% volume concentration with twist ratio of 1.78 in backward arrangement. Thermal performance analysis based on the constant pumping power criteria showed that helical louvered rod inserts with backward arrangement led to better thermal performance than that with forward arrangement. [ABSTRACT FROM AUTHOR]