A new method of acquiring perquisites of recirculation and vortex flow in sudden expansion solar water collector using vortex generator to augment heat transfer

摘要

The present study focuses on the heat transfer enhancement in sudden expansion channel (SEC) which is to be employed as solar water collector using vortex generator (VG) at different angles of attack. Expansion ratio (ER) of SEC is ascribed as 2:1. The analysis of heat transfer enhancement is carried out for various aspect ratios (AR) of , infinity, 8 and 6 of SEC. The angle of attack (beta) of VG is varied from 30 degrees to 90 degrees by an increment of 15 degrees in each case. The results of this study are compared with that of simple rectangular channel (SRC) with VG. The flow is assumed to be laminar, steady and incompressible in the Reynolds (Re) number range investigated. Finite volume based commercial computational fluid dynamics (CFD) code FLUENT 16.2 has been used for solving three dimensional governing equations. The investigation shows that VGs are very effective in SEC than in SRC in enhancing the heat transfer against pressure drop at all angles of attack. Heat transfer rate increases with increase in AR of SEC while the change in friction factor with AR of SEC is negligible except at higher angle of attack. However with increasing angle of attack of VG, friction factor is on the rise. The results reveal that the enhancement of heat transfer rate is due to the combined effect of longitudinal vortex flow and flow separation. VG at beta = 30 degrees and 60 degrees is found to have an optimal heat transfer and fluid flow characteristics in SEC.