Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow

This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration

Rheological Behavior of Zinc-Oxide Nanolubricants

International audienceWe report an experimental investigation of rheological properties of turbine oil-zinc oxide nanoparticle dispersion with different nanoparticle weight fractions ranging from 0.1 to 4%. Rheological experiments were performed within the temperature range of 0 to 60°C. The results showed that nanolubricants and the base fluid behave like Bingham fluid. Nanolubricant viscosity enhancement as a function of nanoparticle volume fraction is well predicted by Bachelor equation with modified volume fraction. Thereby, rheological data revealed that nanoparticles make aggregates in the turbine oil with diameter about 3.6 of diameter of a single nanoparticle. Moreover, temperature effect on viscosity and yield stress of nanolubricants is shown and discussed

Experimental investigation of Multiwall Carbon Nanotubes/Water Nanofluid Pool Boiling on Smooth and Groove Surfaces

Boiling is an essential process for many industrial applications such as refrigeration, distillation, chemical processes. The efficiencies of these applications are dependent on effectiveness of the heat transfer processes. This study presents the experimental data analysis for pool boiling performance of 0.10~0.20% (wt%) of Multiwall Carbon Nanotubes (MWCNTs)/water nanofluid on smooth and straight, square and circular grooved surfaces. According to experimental results, the highest enhancement in boiling heat transfer coefficient is observed in configuration S4 consisting of 30mm deep circular groove inclined at 45° angle and 33% higher than the base fluid on the smooth surface. Based on this investigation, the paper indicates that the inclination of the circular groove has the potential to enhance significantly pool boiling heat transfer process. Furthermore, the paper justifies that the effectiveness enhancement analysis of the nanofluids under a range of concentrations and geometrical configurations of heat transfer surfaces is still essential and desirable