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 350-600K. 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≤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.
Bibliographical noteFunding Information:
The support received from the Tshwane University of Technology and the University of Pretoria is duly acknowledged and appreciated. The funding received from the National Research Foundation (NRF), the Translational Engineering Skills Programme (TESP), Stellenbosch University, the South African National Energy Research Institute (SANERI)/South African National Energy Development Institute (SANEDI) at the University of Pretoria, the Council for Scientific and Industrial Research (CSIR), the Energy-efficiency and Demand-side Management (EEDSM) Hub and NAC is also duly acknowledged and appreciated.
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- Entropy generation
- Optimal Reynolds number
- Parabolic trough receiver
- Thermodynamic analysis