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In this paper, results of a thermodynamic analysis using the entropy generation minimisation method for a parabolic trough receiver tube making use of a synthetic oil-Al 2 O 3 nanofluid as a heat transfer fluid are presented. A parabolic trough collector system with a rim angle of Nanoparticle volume fractions in the range 0 ≤ ϕ ≤ 8% were used. The local entropy generation rates due to fluid flow and heat transfer were determined numerically and used for the thermodynamic analysis. The study shows that using nanofluids improves the thermal efficiency of the receiver by up to 7.6%. There is an optimal Reynolds number at each inlet temperature and volume fraction for which the entropy generated is a minimum. The optimal Reynolds number decreases as the volume fraction increases. There is also a Reynolds number at every inlet temperature and volume fraction beyond which use of nanofluids is thermodynamically undesirable.

This paper presents results of a numerical study on the thermal and thermodynamic performance of a high concentration ratio parabolic trough solar collector using Cu- Above a certain Reynolds number, further increase in the Reynolds numbers makes the entropy generation higher than that of a receiver with only the base fluid. Key wordsConcentration ratio, entropy generation, nanofluid, parabolic trough receiver, thermal efficiency. †

Fiber reinforced composites have been used in several applications for several years and the market is continuously growing. It is known that the addition of fibers for reinforcing of matrix has advantages, especially the mechanical properties of the composites. Environmental and economic concerns are stimulating new research in the development of sustainable fiber for reinforcing polymer matrix. Particularly attractive are new materials in which a good part is based on natural and renewable resources, hence aggravating the environmental concerns that may result in the depletion and dwindling of wood resources from forest. This assessment report provides detailed world production of natural fiber and the inherent looming danger envisaged if attention is not shifted from its continuous usage. It has been stated that natural fibers are renewable and sustainable, but they are in fact, neither i.e. living plants are renewable and sustainable, from which natural fibers are taken, but not the fibers themselves. The US market reports that the composite market was 2.7 billion pounds sterling in 2006 and it is estimated to reach 3.3 billion pound sterling by 2012 with a 3.3% annual growth. Natural fiber market in the US experienced a 13% growth rate (275 million kilograms) between 1994 and 2004 and the demand for the natural fibers continues to rise. The average global annual market growth for natural fibers between 2003 and 2007 was 38%, while Europe saw the highest annual growth rate of 48%. This market was estimated at 0.36 million metric ton in 2007 and it is expected to reach 3.45 million metric ton in 2020. Fiber reinforced market is a multibillion dollar business and the natural fiber composites take a fair part of it.