Effects of rib arrangements on the performance of a parabolic trough receiver with ribbed absorber tube

Six different arrangements of ribbed tube are employed to improve the performance of parabolic trough receiver (PTR) in this paper. Detailed analyses of flow structure, thermal performance, flow resistance and overall thereto-hydraulic performance are conducted. The results indicate that the symmetrical anticlockwise arrangement of double inclined ribs (SADIR) and symmetrical clockwise arrangement of single inclined ribs (SCSIR) achieve the flow pattern with a pair of counter-rotating vortexes and obtain the best performance with reductions in peak temperature and heat loss reaching up to approximately 177 degrees C and 80.1%. Nusselt number of the SADIR and SCSIR are about 1.58-3.21 and 1.41-2.98 times that of the PTR with plain tube, respectively. The enhanced PTRs with ribbed tubes achieve great improvements in overall thermo-hydraulic performance at low Reynolds number (Re < 30,000) but suffer poor overall performance at high Reynolds number. For the range of parameters considered, the PEC value and modified thermal efficiency are ranged in 0.62-1.56 and 0.70-0.73, respectively. And the maximum enhancement in modified thermal efficiency is approximately 1.9%.