Enhanced Thermal Conductivity of Copper Nanofluids: The Effect of Filler Geometry.

Nanofluids are colloidal dispersions that exhibit enhanced thermal conductivity at low filler loadings and thus have been proposed for heat transfer applications. Here, we systematically investigate how particle shape determines the thermal conductivity of low-cost copper nanofluids using a range of distinct filler particle shapes: nanospheres, nanocubes, short nanowires, and long nanowires. To exclude the potential effects of surface capping ligands, all the filler particles are kept with uniform surface chemistry. We find that copper nanowires enhanced the thermal conductivity up to 40% at 0.25 vol % loadings; while the thermal conductivity was only 9.3% and 4.2% for the nanosphere- and nanocube-based nanofluids, respectively, at the same filler loading. This is consistent with a percolation mechanism in which a higher aspect ratio is beneficial for thermal conductivity enhancement. To overcome the surface oxidation of the copper nanomaterials and maintain the dispersion stability, we employed polyvinylpyrrolidone (PVP) as a dispersant and ascorbic acid as an antioxidant in the nanofluid formulations. The thermal performance of the optimized fluid formulations could be sustained for multiple heating-cooling cycles while retaining stability over 1000 h.

Estimation of carbon dioxide sequestration potential of microalgae grown in a batch photobioreactor.

The carbon dioxide (CO2) sequestration potential of two microalgae, Chlorella pyrenoidosa and Scenedesmus abundans was evaluated in a tubular batch photobioreactor with provision for continuous flow of 10% CO2 enriched air through the headspace. CO2 sequestration and biomass growth was affected by gas flow rate over the range 20-60ml/min and 40ml/min was found to maximize algal growth and CO2 sequestration. Moles of CO2 sequestered over 20h at a gas flow rate of 40ml/min was estimated using a novel rapid screening approach as 0.096 and 0.036, respectively, for C. pyrenoidosa and S. abundans. At this gas flow rate the maximum growth rate was 4.9mgL(-1)h(-1) and 2.5mgL(-1)h(-1) for C. pyrenoidosa and S. abundans, respectively. The CO2 sequestration and growth rate were comparable at height/diameter ratio of 8 and 16.

1D copper nanostructures: progress, challenges and opportunities.

One-dimensional noble metal nanostructures are important components in modern nanoscience and nanotechnology due to their unique optical, electrical, mechanical, and thermal properties. However, their cost and scalability may become a major bottleneck for real-world applications. Copper, being an earth-abundant metallic element, is an ideal candidate for commercial applications. It is critical to develop technologies to produce 1D copper nanostructures with high monodispersity, stability and oxygen-resistance for future low-cost nano-enabled materials and devices. This article covers comprehensively the current progress in 1D copper nanostructures, most predominantly nanorods and nanowires. First, various synthetic methodologies developed so far to generate 1D copper nanostructures are thoroughly described; the methodologies are in conjunction with the discussion of microscopic, spectrophotometric, crystallographic and morphological characterizations. Next, striking electrical, optical, mechanical and thermal properties of 1D copper nanostructures are highlighted. Additionally, the emerging applications of 1D copper nanostructures in flexible electronics, transparent electrodes, low cost solar cells, field emission devices are covered, amongst others. Finally, there is a brief discussion of the remaining challenges and opportunities.

Economic appraisal of supercritical fluid extraction of refined cashew nut shell liquid.

This manuscript summarises the techno-economic feasibility of refined cashew nut shell liquid (CNSL). A simple mass transfer based mathematical model for the yield prediction is presented. The process parameters and extraction time for maximum profit and purity of the product were optimized. The optimum extraction time for maximum profit and purity was found to be 0.9h at 300 bar and 323 K. The influence of the different costs, such as fixed cost, raw material cost, labor cost, utility cost, etc. on profit and cost of production of the extract is also presented.

Extraction of cashew (Anacardium occidentale) nut shell liquid using supercritical carbon dioxide.

This work investigated the extraction of cashew nut shell liquid (CNSL) using supercritical carbon dioxide (SC-CO(2)). Effects of process parameters such as extraction pressure, temperature and flow rate of SC-CO(2) were investigated. The yield of CNSL increased with increase in pressure, temperature and mass flow rate of SC-CO(2). However, under different operating conditions, the composition of CNSL varied. The study of physical properties and chemical composition of the oil obtained through super critical fluid extraction (SCFE) showed better quality as compared to the CNSL obtained through thermal route. Experimental results were compared with diffusion based mass transfer model. Based on this simple model, extraction time was optimized.