Abstract:
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–Al2O3 nanofluid as a heat transfer fluid are
presented. A parabolic trough collector system with a rim angle of 80 and a concentration ratio of 86 was
used. The temperature of the nanofluid considered was in the range of 350–600 K. The nanofluid thermal
physical properties are temperature dependent. The Reynolds number varies from 3,560 to 1,151,000,
depending on the temperature considered and volume fraction of nanoparticles in the base fluid.
Nanoparticle volume fractions in the range 0 6 / 6 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.
