A parabolic trough solar collector is a form of concentrated solar power (CSP) system that generates electricity. It is made out of a long, curved, mirrored trough that directs sunlight toward a receiver tube running along the trough’s focal line. This tube contains a fluid that absorbs the concentrated sunlight’s heat. The heated fluid is then utilized to generate steam, which drives a turbine attached to a generator, resulting in electricity. Parabolic troughs are efficient and used widely in utility-scale solar power plants because of their dependability and ability to generate electricity even when the sun is not directly overhead.

Figure 1 – Schematic of the parabolic solar trough collector

In this project, the solar collector itself is the main focus of the study. It is an efficient way to study the collector’s performance by considering the effect of received solar irradiation using a non-uniform distribution of heat flux. The paper entitled “Performance analysis of a parabolic trough solar collector with non-uniform solar flux conditions” has been chosen as the reference paper for the present work.

• Reference [1]: Wang, Yanjuan, et al. “Performance analysis of a parabolic trough solar collector with non-uniform solar flux conditions.” International Journal of Heat and Mass Transfer82 (2015): 236-249.
• Reference [2]: Wang, Jinping, et al. “Performance simulation comparison for parabolic trough solar collectors in China.” International Journal of Photoenergy1 (2016): 9260943.

Simulation Process

As mentioned above, the key focus of the present project is just the collector. Thus, we need to utilize a user-defined function (UDF) on the bottom surface of the collector to apply non-linear heat flux reflected by the parabolic trough. Figure 2 shows the irradiation profile on the outer surface of the absorber presented in the article. It is clear that the Discrete ordinates radiation model is also activated regarding the radiative effects.

Figure 2- irradiation profile on the outer surface of the absorber

Post-processing

The velocity contours show a complicated flow pattern around the receiver tube, with maximum velocities of 22.9 m/s in the areas near the tube surface. The flow field has a certain symmetrical pattern, with the highest velocities found in the top parts of the domain, where the fluid accelerates due to thermal buoyancy effects. The circular receiver tube forms a wake region directly behind it, with lower velocities ranging from 0-4.59 m/s, indicating probable recirculation zones that may decrease total heat transfer efficiency. The gradual transition from high-velocity regions  to intermediate velocities shows the formation of boundary layers and mixing zones surrounding the collector shape.

Figure 3: Velocity distribution around the parabolic trough solar collector

The temperature distribution, when combined with the velocity field, demonstrates the success of the sun concentration design. The heat flow given to the absorber wall via the UDF implementation results in discrete thermal gradients, with peak temperatures occurring at the focus point where the parabolic trough concentrates solar energy. The temperature contours show successful heat transfer to the working fluid, especially in areas where the velocity field supports good mixing. The Discrete Ordinates (DO) radiation model accurately depicts radiative heat transfer processes, as indicated by temperature distribution patterns around the receiver tube. This linked thermal-fluid behavior validates the design’s efficiency in converting solar radiation into useable thermal energy.

Figure 4- Temperature distribution around the parabolic trough solar collector