Includes CD

Includes references (136-148 p.)

'ABSTRACT The parabolic trough collector (PTC) is the most deployed solar concentrating collector in the world. Thermal performance analysis of the collector is performed in this thesis with the aim of understanding the heat transfer parameters that could enhance the thermal performance of the collector. The PTC used in this thesis is modeled using the engineering equation solver and is adapted from the commercially available LS-2 collector. Thermal model validation is performed with the results of the Sandia National laboratory LS-2 test. A sensitivity analysis is carried out to evaluate the robustness of the model to six key input parameters. Six studies are carried out to evaluate the impact of various working fluids including nanofluids, the effects of variously modified geometries on the collector's performance and the exergetic impact of these geometries on the useful work obtained from the collector. The other studies conducted involves the development of two new nanofluids for use in the solar collector, a detailed entropy generation study of the proposed working fluid on the collector and finally an economic and environmental impact assessment of the irreversibilities on the performance of the PTC is also performed. The results show that of the six working fluids investigated; pressurized water, supercritical CO2, Therminol VP-1, and the addition of CuO, Fe3O4, and Al2O3 nanoparticles to TherminolVP-1, the Al2O3/Oil nanofluid provides the best improvement of 0.22% to thermal efficiency. Five different geometry configurations are considered: plain tube (smooth tube), longitudinal finned tube, a tube with a porous insert, a tube with a twisted tape insert and a wavy (converging-diverging) tube. The findings indicate that all the modifications enhanced heat transfer with the converging-diverging absorber providing the maximum thermal enhancement of 1.16%. An exergetic evaluation of the different absorber geometries evaluated revealed that the biggest cause of exergy losses was due to the exergy destruction from the sun and the absorber. An alternative to using nanoparticles, materials synthesized from green bio-matter (Olive leaf extract: OLE) and agricultural waste (barley husk: BH) is proposed. The heat transfer performance of the nanofluids shows a mean enhancement in heat convection coefficient of 128% and 138% for water/OLE-TiO2 and water/BH-SiO2 nanofluids respectively. Finally, an analysis of the entropy generation in the OLE-TiO2 nanofluid is carried out for varying parameters of inlet temperature, flow rate, and nanoparticle concentrations. The results show that increasing the concentration of nanoparticles considerably decreases the rate of entropy generation in the system. The exergoeconomic study shows that the cost of exergy destruction is seen to decrease from 3.4 $/hr to 0.35 $/hr as the inlet temperature increases from 323 to 650 K. Keywords: parabolic trough collector, heat transfer, thermal enhancement, nanofluids, absorber geometry, exergy, entropy generation, green-synthesis, exergoeconomic, exergoenvironmental.'