In this paper, a heat transfer optimization approach is brought in with focusing on exergy destruction to properly deal with the trade-off between irreversibility of heat transfer process and pump power consumption in turbulent flow for solar air heater. Thus, the exergy destruction minimization principle is mathematically extended to three dimensional turbulent flow and governing equations are derived with variation method. Successively, the optimized flow field for solar air heater is obtained at Re = 12,000 by applying SST k-omega turbulence model. Furthermore, with detail analysis of velocity and temperature distribution, it is found that the longitudinal swirl flow is generated through this optimization approach. Besides, within the scope of this study, the total heat transfer exergy destruction and average absorber temperature are maximally decreased by about 65% and 30 K respectively in the test section compared with the plain duct. And the maximum Nusselt number and friction factor are increased to 1.81 and 3.13 times over plain duct respectively. These results indicate that the optimization approach is effective for improving the thermal-hydraulic performance of solar air heater. Finally, the inclined vortex plate is designed to realize this kind of optimized flow field successfully. This work will promote technique developments of solar air heater. (C) 2019 Elsevier Ltd. All rights reserved.