Enhanced heat transfer in a parabolic trough solar receiver by inserting rods and using molten salt as heat transfer fluid

Chang, Chun, Sciacovelli, Adriano, Wu, Zhiyong, Li, Xin, Li, Yongliang, Zhao, Mingzhi, Deng, Jie, Wang, Zhifeng and Ding, Yulong (2018) Enhanced heat transfer in a parabolic trough solar receiver by inserting rods and using molten salt as heat transfer fluid. Applied Energy, 220, pp. 337-350. ISSN (print) 0306-2619


With the aim to enhance the reliability and overall heat transfer performance of a parabolic trough receiver, concentric rod and eccentric rod are introduced as turbulators, and the flow and convective heat transfer characteristics of molten salt in a parabolic trough receiver are analyzed. A three-dimensional model was developed and has been validated with experimental results and empirical equations. Highly non-uniform heat flux was provided by a novel parabolic trough collector. The result shows that both concentric rod insert and eccentric rod insert can enhance the heat transfer performance effectively. For a parabolic trough receiver with a concentric rod insert, with the increasing of dimensionless diameter B, the normalized Nusselt number is about 1.10 to 7.42 times over a plain parabolic trough receiver. The performance evaluation criteria can't reasonably evaluate the effect of B growth on the comprehensive heat transfer performance. By introducing integrated performance factor, it can give a reasonable solution, and it shows that the integrated performance factor has a significance decreases with the increase of Reynolds number when B is larger than 0.8. With B increasing, the integrated performance factor of parabolic trough receiver with concentric rod insert decreasing under a certain Reynolds number. For an eccentric rod insert, the performance evaluation criteria and the integrated performance factor decrease with the increasing of Reynolds number under a certain dimensionless eccentricity H. The performance evaluation criteria decreases from about 1.84 to 1.68 times over a plain parabolic trough receiver when H is 0.8. Moreover, the temperature distribution can be uniformed and the maximum temperature on the absorber tube also can be remarkably reduced with the increasing of B and H under a certain Reynolds number, which helps to reduce the thermal deflection and increase the reliability for a parabolic trough receiver.

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