Numerical investigation of the effect of surface roughness on collector efficiency

In this thesis study, in order to increase the energy and exergy efficiency of air solar collectors, the effects of baffle geometries placed in the collector air flow section on the collector efficiency were investigated. Baffle geometries can change the fluid flow and rearrange the air flow in the collector as desired. Within the scope of the study, six different solar collector designs were created and three different air inlet velocities were determined as 0,5 m/s, 0,4 m/s and 0,3 m/s for each collector, and CFD analyzes were made. As a result of CFD analysis, temperature distribution and air streamlines of collectors were examined. The energy and exergy efficiencies of air solar collectors have been calculated with the data obtained from CFD analysis. It has been seen that the baffles placed in the air flow section of the collector have a positive effect on the energy and exergy efficiency. Similarly, the increase in air velocities increases the efficiency values positively, linearly. Among the determined baffle geometries, the highest exergy efficiency was observed at 0,5 m/s speed in the collector with the highest number of baffles, while the lowest exergy efficiency was observed at 0,3 m/s in the collector without baffles. It has been observed that energy efficiency increases up to 25% and exergy efficiency increases up to 22%. The results obtained in the experimental study from the air solar collector were compared with the results of the CFD analysis performed under the same conditions. Considering the average temperature values obtained from the experimental studies and the error analysis results of the measuring devices, it was determined that the average temperature values obtained from the theoretical studies were at a temperature of 366 K and values close to each other. The results of the CFD analysis of the rough surfaces used to increase the efficiency of the collectors provide very close values with the experimental study results.