Numerical investigation of constructive measures to reduce convective losses of solar thermal power plants

Kurzfassung

In the present project, the simulation of Solar Tower Julich has been done to investigate, evaluate and optimize the application of solar power tower plans. The simulation of the flow around the solar tower helps to find out how wind affects the operation of open volumetric receiver which is indeed the main part of the solar tower. This is done by CFD modeling of STJ in OpenFoam 2.2.0 to investigate pressure and velocity variation over time specifically near the receiver. Once OpenFOAM's meshing tool has been hard to use for complex geometries, ANSYS ICEM CFD 14.0 was applied for meshing and then the output was translated into OpenFOAM format. The air flow around the tower was assumed to be incompressibe and with no temperature effect, i.e. no buoyancy. Therefore, PIMPLE algorithm in OpenFOAM was applied for solving the problem. In this algorithm, the incompressible Reynolds-averaged Navier-Stockes (RANS) equations have been solved together with the turbulence model. It was found that the flow around the tower in all the velocity cases was turbulent and the main turbulence model which was used in this study was realizable k-epsilon model. For one of the simulation cases, k-omega SST turbulence model was also applied to compare the results of these two models. The flow around the tower is an atmospheric boundary layer (ABL) flow and was assumed to be over a flat uniform terrain. For simplicity, some features of real ABL such as air humidity, surface heating, etc. have not been included. The results obtained for five different wind directions and three different wind speeds and afterwards, pressures and velocities have been presented specifically for the area near the receiver. The periodic behavior of vortices has been observed which had the highest values for the west wind direction; therefore, the sensitivity analyses have been done mainly for this direction. Vortex shedding has been evaluated which resulted Strouhal number has a good agreement with Strickland Strouhal number for western, southwestern and northwestern wind direction in different velocities. For northern and southern wind direction, Strouhal number was different from Strickland idea.