A trans-dimensional multi-physics coupled analysis method for direct-steam-generation parabolic-trough loop

Highlights: • A trans-dimensional multi-physics coupled analysis method is proposed. • 1D loop-level thermo-hydrodynamic sub-model is to predict loop performance. • 3D component-level multiphysics coupled sub-model is to quantify local deformation. • Maximum local z-deviation of DSG-HCE reaches −1.67 cm in superheating section. • HCE in boiling section with stratified flow bends oppositely against other cases. Quantification of the thermal stress-induced deformation issue of the heat collection element (HCE), which is hardly avoidable during the practical operation of parabolic-trough (PT) concentrated solar power (CSP) plants is of primary importance, especially with direct steam generation (DSG) technology. However, currently-available analysis methods are either inefficient or inaccurate. In the present work, a trans-dimensional multi-physics coupled analysis method is proposed. The method consists of a one-dimensional loop-level thermo-hydrodynamic model, which efficiently predicts the global performance of loop, and three-dimensional optical-hydrodynamical-thermal-mechanical coupled model, which accurately quantifies the local deformation of HCE. The information exchange between the two models is accomplished through a self-developed coupling code. After model validation by experimental data, the proposed method is applied in different cases for the preheating, boiling (annular/stratified flow pattern), and superheating sections of a DSG-PTC loop. The worst scenario is found to exist in the superheating section, giving the maximum circumferential temperature difference of 29 K and the maximum z-deviation of −1.67 cm. When it is stratified flow (x = 0.56) in the boiling section, the corresponding values are 21 K and 0.69 cm. It should be noted that, considering the practical installation errors and the interaction between HCE and concentrator, the deformation not only changes the distribution of heat flux but also potentially causes optical loss. Meanwhile, the results verify the capability of the proposed analysis method in performing thermal stress deformation analysis on entire loop, which can be further extended to various forms of line-focused CSP technologies.