Irreversibility analysis of induced swirl flow inside the pipes of flat-plate solar collector using dual tangential nozzles

In the present research, dual-nozzle swirl generator was installed at the blocked end of the straight tube to inject flow tangential to the wall of the pipe with various injection inclinations compared to the longitudinal axis. This causes a swirl flow inside the pipe. Altering some decisive variables, including injection angle, side of nozzle cross-section, pipe diameter, and flow rate, caused to attain various cases with unique hydraulic-geometrical characteristics. Classes ‘A…-D50-N…-M…’ and ‘A…-D20-N…-M…’ bear the main characteristics of the cases embodied in their sub-classes. Entropy generation (St), Nu*, NE, Heat Transfer Improvement (HTI) index and ${\eta}_{w-s}$ were used as effective tools for the basement of the system based on the irreversibility concept. The results showed that all of the cases of class ‘A…-D50-N…-M…’ cause lower frictional-contributed and higher thermal-contributed entropy generation compared to the class ‘A…-D20-N…-M…’. The highest values of the HTI index are 1.5 and 1.763 obtained by ‘A30-D20-N5-M0.4’ and ‘A90-D20-N6.25-M0.1’, respectively.