Numerical Investigation on the Effects of Baffles with Various Thermal and Geometrical Conditions on Thermo-Fluid Dynamics and Kinetic Power of a Solar Updraft Tower

Abstract

Solar updraft towers (SUTs) are used for renewable power generation, taking advantage of the thermal updraft air flow caused by solar energy. Aerodynamic devices have been applied to SUTs to improve their performance and the baffle is one such device. Here, we investigate the effect of baffle installation on the thermo-fluid dynamic phenomena in the collector of an SUT and how it enhances the overall SUT performance using computational fluid dynamics analysis. Two geometric parameters (height and width of baffle) and two thermal boundary conditions of the baffle (adiabatic condition and heat flux condition) were tested through simulations with 10 different models. The vortex generated by the baffle has a positive effect on the delivery of heat energy from the ground to the main flow; however, one disadvantage is that the baffle inherently increases the resistance of the main flow. Over 3% higher kinetic power was achieved with some of the simulated baffle models. Therefore, an optimum design for baffle installation can be achieved by considering the positive and negative thermo-fluid dynamics of baffles.

Additive Aerodynamic and Thermal Effects of a Central Guide Post and Baffle Installed in a Solar Updraft Tower

“…In our previous studies on the height and location of baffles, baffles have been shown to play an active role in the transfer of heat accumulated in the absorber to the air flow in the SUT. In a study of baffle height, the positive and negative effects of the baffle within the SUT was investigated, and performance improvement of up to 4.69% was confirmed [9]. The baffle location influences flow, which is divided into circulating flow and main flow in the collector, and it was confirmed that the baffle located at the inlet of the collector contributes the most toward enhancing the performance of the SUT [10].…”

“…As one of the aims of this study was to quantify the interactions between the CGP and the baffle, we further created models with both the CGP and baffle installed in the collector. In the case of the baffle, the optimal shape, size, and installation location values determined in our previous studies [9,10] were used-0.15 m high, 0.08 m wide, and location of r = 4.5 m (from the center). As mentioned above, depending on the 15 geometries of the CGP and existence of a baffle, a total of thirty models were analyzed in this study (fifteen models for analyzing the effect of the CGP, and an additional fifteen models for investigating the simultaneous effects of the CGP and baffle).…”

Thermo-Fluid Dynamic Effects of the Radial Location of the Baffle Installed in a Solar Updraft Tower

“…The geometry of the SUT analyzed in this study is basically the same as two previous studies of the SUT with the baffle mentioned above [13,14]. The total height of the SUT is 13 m, the chimney height is 12 m, the collector diameter is 10 m, the inlet of the collector has a height of 0.15 m, and the chimney diameter is 0.25 m (Figure 2a).…”

“…The chimney, roof, and baffle are assumed to be adiabatic ( Table 2). The abovementioned boundary conditions refer to our previous model study [14]. The reason for setting the chimney and roof to the adiabatic condition is to assume no heat loss for that part.…”

“…We concluded that this is not the purpose of this study which only examines the influence of location of the baffle. The numerical model used in this study is based on the previous study of our group [14], and the validation of the model is described in Section B of the Supplementary Materials. The number of iterations was determined by monitoring the convergence of residuals of the mass flow rate of the chimney outlet and the temperature of the chimney inlet.…”