NUMERICAL SIMULATION OF PARABOLIC TROUGH RECEIVER UNDER NON-UNIFORM AND FLUCTUANT SOLAR FLUX CONDITION

In this paper, a three-dimensional transient numerical model of a parabolic trough receiver is developed, taking both the non-uniformity and the fluctuation of the solar flux into account. The solar flux distribution is calculated by the Monte Carlo ray-trace method first. Then, the transient coupled heat transfer within the parabolic trough receiver is simulated by the finite volume method where the non-uniform and fluctuant solar flux distribution is treated as the heat flux boundary condition. The present model is validated based on the experimental data published by Sandia National Laboratories. Finally, the model is used to study the transient response characteristics of the parabolic trough receiver. The dynamic variations of the heat transfer fluid outlet temperature and the temperature field of the absorber tube wall are discussed in detail. The results indicate that the non-uniform and fluctuant solar flux distribution leads to the transient non-uniform temperature fields of the absorber tube wall, and the heat transfer fluid outlet temperature is greatly affected by the fluctuation of the solar flux. Also, it is revealed that the absorber tube wall temperature responses to the change of the solar radiation intensity slightly earlier than the heat transfer fluid outlet temperature. The response time increases with the amplitude of the solar flux fluctuation but decreases with the increased heat transfer fluid mass flow rate. The transient response characteristics can provide guides for the operation of parabolic trough solar powers, and the transient non-uniform temperature fields are the basis of thermal stress and strain analysis.