Thermal analysis of solar receiver pipes with superheated steam

Direct steam generation (DSG) process in the absorber tubes of parabolic-trough solar collectors is experiencing an important development in the last decade. This concentrated solar technology can be used in solar fields for electricity production or industrial-process heat supply. The modeling and simulation of the DSG process in the parabolic-troughs are essential for the detailed design of the collector field. One of the critical aspects that should be identified is which process conditions may cause an overheating of the absorber tubes.A Computational Fluid Dynamics (CFD) model has been developed to calculate the temperature profile in the wall of absorber tubes of parabolic-trough solar collectors using steam as heat-transfer fluid. Steam presents lower thermal conductivity than water or other typical liquid heat-transfer fluids used in parabolic troughs. Therefore, for similar process conditions, the thermal stress in the absorber tubes is higher when the fluid is steam. The Finite Volume Method (FVM) package FLUENT is used to implement the model and to perform the investigation. This article summarizes the model used and a comparison of simulation results and measurements taken at a DSG solar test facility located at the Plataforma Solar de Almería, Spain.

► Direct steam generation in concentrating solar systems is one of the new promising technologies for solar power plants.
► Absorber pipes receive non-homogeneous heat flux.
► Non-homogeneous heat flux could produce critical thermal gradients in the receiver pipes, specially with superheated steam.
► CFD analysis helps to predict the pipes behavior with different working conditions.
► Simulation results have been validated with experimental data.