Field synergy analysis for turbulent heat transfer on ribs roughened solar air heater

Abstract

Convective turbulent heat transfer field synergy equations for a solar air heater channel with rib turbulators are developed based on the extremum principle of heat transfer potential capacity dissipation. Field synergy equations can be used to increase the field synergy between the velocity vector and temperature gradient fields over the entire heat flow domain to enhance the convective turbulent heat transfer. Solution of the field synergy equations gives the optimal flow field of swirls flow under the ribs and in the cavity area (i.e. between rib to rib), which are followed by a gradual increase of Nusselt number up to following rib, having the best field synergy for a different viscous dissipation. Using optimal velocity patterns as a guide, the design of solid inclined, curved and vertical baffles can be introduced in actual applications, so as to generate the desired swirls flow and enhance the overall coverage of turbulent heat exchange. As illustrative examples, the local field synergy angle analyses for turbulent heat transfer in ribs roughened channel with/without solid baffles are presented. Results show that the solid curved baffles mounted near absorber plate has a best performance evaluation criterion of 0.99.