Numerical analysis on a solar air heater provided with saw tooth shaped turbulators for augmented thermal performance

There have been numerous studies on the effect of turbulators of various shapes integrated with the absorber plate for an improved performance. However, a study on saw-toothed profiled turbulators is not available in the literature. In this paper, an attempt has been made to explore in detail on this aspect. Turbulators of different heat transfer surface types mainly create flow disturbance and break the laminar sub-layer, enhancing the heat transfer rate. The present work, saw tooth turbulator profiles with different configurations, i.e. upstream tapered, downstream tapered and flat turbulators attached to the SAH absorber plate, are being numerically investigated. For the base model, i.e. without any turbulators, a numerical and experimental analysis has been carried to establish the overall validity. All tested saw tooth turbulator configurations show better performance compared to the base model. Configuration, which is tapered towards the upstream-end, shows a better performance in terms of outlet temperature, Nusselt number and thermo-hydraulic enhancement factor compared to the other configuration tested. It is found from the analysis that for upstream tapered turbulators, there is an enhancement of 8% to 20% improvement in Nusselt number of the flow as well as 1.05 to 1.18 in the thermo-hydraulic performance corresponding to higher to lower flow rates, respectively. As also for downstream tapered turbulators, an improvement of 5% to 16% in Nusselt number and 1.04 to 1.17 in the thermo-hydraulic performance are observed corresponding to higher to lower flow rates, respectively.