A dynamic three-dimensional volume element model (VEM) of a parabolic trough solar collector (PTC) comprising an outer glass cover, annular space, absorber tube, and heat transfer fluid is studied with detail. The model is coupled with an existing semi-finite optical model for the purpose of simulation and optimization. The spatial domain in the VEM is discretized with lumped control volumes (i.e., volume elements) in cylindrical coordinates according to the predefined collector geometry. Therefore, the spatial dependency of the model is taken into account without the need to solve partial differential equations. The proposed model combines principles of thermodynamics and heat transfer as well as empirical heat transfer correlations, to simplify the modeling and expedite the computations. The resulting system of ordinary differential equations is integrated in time, yielding temperature fields which can be visualized and assessed with scientific visualization tools. The current model is validated with experimental data provided in the literature. The model was employed to evaluate the sensitivity of the collector performance described by the first and second law efficiencies to receiver length, annulus gap spacing, concentration ratio, incidence angle, inlet fluid temperature, and flow rate. This work also examined the effects of inlet fluid temperature and temperature differential on dynamic collector performance in the transient case study. Results showed that the first law efficiency was most sensitive to the inlet fluid temperature with the maximum variation of 30%, whereas the incidence angle and concentration ratio affected the second law efficiency the most with the maximum variations of 375% and 300%, respectively. The effect of the remaining parameters were trivial in all cases. In the transient analysis, higher temperature differential and lower inlet fluid temperature yielded higher total heat gain while the total exergy gain was insensitive to both parameters. The first law efficiency should therefore be of greater importance than the second law efficiency in the control of dynamic collector performance based on these two parameters. Furthermore, a sensitivity analysis of vemPTC is done with the Fourier amplitude sensitivity testing (FAST) for selected nine parameters. Cover transmittance shows a highly sensitive parameter within the rest of the selected parameters. After this sensitivity analysis, a multi-objective sensitivity analysis is studied for different heat transfer fluids such as synthetic oils, molten salts, liquid metals, nanofluids, and gases. Sobol sampling method is used for a multi-objective sensitivity analysis of different heat transfer fluids except for nanofluids, because it is more accurate to use a different methodology for sensitivity analysis of nanofluids, due to the effects of specific parameters on both first and second law efficiency. The fluid inlet temperature is a common sensitive parameter for almost all heat transfer fluids. Therefore, a multi-objective optimization study is done with four parameters and the results of it are presented in Chapter Four. Moreover, Chapter Five shows enhancement of the efficiency of both traditional parabolic trough solar collector (PTC) and transparent insulation material integrated PTC in both one and two dimensional model. Altering model types, operating conditions, or making an assumption for some used correlations is studied in the last chapter of this dissertation. After comparing the 1D and the 2D model, the results show that the most promising model type of PTC is the 2D model with TIM integrated one with correlation due to its stability for predicted efficiency. That approved that simplifying the model types may affect the results even though sufficiently accurate results are obtained with a simplified model. Temperature-dependent parameters should be selected for temperature sensitive variable in order to reach precise results.
